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The Geology of the Midlothian Coalfield

By W. Tulloch, B.Sc. and H. S. Walton, B.Sc.

Bibliographic reference: Tulloch, W. and Walton, H.S. 1958. The Geology of the Midlothian Coalfield. Edinburgh: Her Majesty's Stationery Office

Department of Scientific and Industrial Research. Memoirs of the Geological Survey Scotland.

The Geology of the Midlothian Coalfield.

By W. Tulloch, B.Sc. and H. S. Walton, B.Sc. with contributions by W. Mykura, B.Sc. and H. E. Wilson, M.Sc. Palaeontology by R. B. Wilson, B.Sc. and M. A. Calver, M.A.

Edinburgh: Her Majesty's Stationery Office 1958.© Crown copyright 1958

Published by Her Majesty's Stationery Office To be purchased from:York House, Kingsway, London, W.C.2 423 Oxford Street, London, w.1 13A Castle Street, Edinburgh 2 109 St. Mary Street, Cardiff 39 King Street, Manchester 2 Tower Lane, Bristol 1 2 Edmund Street, Birmingham 3 80 Chichester Street, Belfast or through any bookseller. Price £1 ls. 0d. net

(Front cover)

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Preface

By far the greater part of the Midlothian Coalfield is shown on Sheet 32 of the one-inch geological map of Scotland. The original survey was made by H. H. Howell and the map issued in 1859. The explanatory memoir 'The Geology of the Neighbourhood of Edinburgh' was published in 1861. Continuing his work to the south Howell mapped the remainder of the coalfield which lies within the area shown on Sheet 24, published in 1868, with accompanying memoir dated 1869, Horizontal and vertical sections, illustrating the structure and the correlation of seams in the coalfield, were published in 1863.

The second edition of Sheet 32 appeared in 1892 following a revision by A. Geikie, H. H. Howell, B. N. Peach, J. S. Grant Wilson and H. M. Cadell. A further revision was undertaken between 1902 and 1906, the officers engaged in the Midlothian Coalfield being C. T. Clough, Dr. E. M. Anderson, C. B. Crampton, L. W. Hinxman, J. S. Grant Wilson, W. Gibson and Sir E. B. Bailey.

The third edition of the sheet, based on this work, is dated 1910 and the explanatory memoir was issued as a second edition in the same year. The memoir includes a summary, by G. W. Lee, of the work of many palaeontologists of that and earlier times. Separate drift and solid editions of the map were published in 1928 and 1930 respectively. The six-inch sheets covering the coalfield are dated 1906–8. In 1909 a set of four sheets of vertical sections, illustrating the coal basin, were issued.

A small area at the southern end of the coalfield was re-mapped by Drs. H. H. Read, J. E. Richey and W. Q. Kennedy between 1925 and 1928 and the additional information included in a new edition of Sheet 24, dated 1932. In 1937 this work was continued by Dr. T. Robertson and Mr. J. K. Allan. The main task of re-mapping was, however, undertaken in 1947 and continued until 1952, the officers concerned being Messrs. W. Mykura, W. Tulloch, H. S. Walton and H. E. Wilson, under Dr. J. B. Simpson as District Geologist. New editions of the six-inch maps of the coalfield have since been published. With the exception of the palaeontological details, which are the work of Messrs M. A. Calver and R. B. Wilson under Dr. F. W. Anderson as Chief Palaeontologist, the memoir has been written by Messrs. W. Tulloch and H. S. Walton and edited by Dr. G. H. Mitchell. Messrs. G. A. Goodlet, W. E. Graham and W. Manson have assisted in the collection and classification of material. Dr. E. D. Currie identified goniatites from the Upper Limestone Group and Roslin Sandstone Group.

A considerable volume of new information regarding the coalfield has resulted from the re-survey. The new maps show the geology in greater detail than did the earlier ones.

Thanks are due to many agents, managers, engineers and surveyors of the National Coal Board and of private companies as well as to mining engineers, boring contractors, quarry-owners and water engineers, for much assistance given and information provided.

W. J. Pugh. Director, Geological Survey Office, Exhibition Road, South Kensington, S.W.7 12th September, 1958.

List of six-inch maps

The following is a list of the revised six-inch geological maps, included wholly or in part, in the Midlothian Coalfield, with the initials of the surveyors and dates of survey. The names of the officers are as follows: J. K. Allan, W. Q. Kennedy, W. Mykura, H. H. Read, J. E. Richey, T. Robertson, W. Tulloch, H. S. Walton, H. E. Wilson.

The six-inch maps have been or are being published and are issued in three forms: (1) Uncoloured; (2) Solid edition, coloured to show solid geology; and (3) Drift edition, coloured to show superficial deposits. Copies of the maps are available for public reference in the Library of the Geological Survey and Museum, South Kensington, London, S.W.7, or at the Geological Survey Office, 19, Grange Terrace, Edinburgh, 9. Published maps may be purchased through Ordnance Survey Agents.

Chapter 1 Introduction

From the city of Edinburgh the Pentland Hills extend south-westwards for some twenty miles, forming a range rising to 1898 ft above sea-level at Scald Law. About eight miles to the east a roughly parallel but considerably lower line of hills runs from the coast at Prestonpans, by way of Cousland to a point about half a mile south of D'Arcy Farm. Between these ridges lies the undulating plain of the Midlothian Coalfield, rising gradually southwards to Auchencorth Moss. To the south-east its limits are set by the Moorfoot Hills from Middleton Moor to Gladhouse and the nearly parallel ridge extending south-west behind Leadburn.

The coalfield is drained by the rivers North and South Esk and their tributaries which, uniting below Dalkeith, reach the sea at Musselburgh.

The Pentland Hills consist of sediments and igneous rocks of Old Red Sandstone age with a core of Silurian rocks, bounded on the south-east by the great Pentland Fault. This fracture, in places demonstrably a reverse fault, extends from Portobello south-westwards far beyond Carlops and marks the north-western limit of the Midlothian coal-basin (Figure 1). The eastern boundary of the coalfield is formed by the line of the D'Arcy–Cousland Anticline which closely follows the range of hills mentioned above from Prestonpans to Gorebridge. Along its axis the Lower Limestone Group is exposed in a series of inliers, separating the outcrop of the Limestone Coal Group of the Midlothian Coalfield from the same beds on the western margin of the East Lothian Coalfield. With the dying out of the D'Arcy–Cousland Anticline southwards, however, the East Lothian field joins that of Midlothian. The boundary of the latter in this account is set by the arcuate outcrop of the Lower Limestone Group which ranges from near Crichton on the Tyne Water by way of Borth-wick to Howgate and thence by Leadburn and Macbiehill to the Pentland Fault near Carlops. To the north the coalfield extends beneath the Firth of Forth opposite Musselburgh and Prestonpans for an unknown distance; already workings in the Limestone Coal Group have been carried under the sea for about two miles.

Within the boundaries indicated Carboniferous rocks ranging in age from the Calciferous Sandstone to Barren Red Coal Measures are represented, including the two great coal-bearing groups of Scotland, the Limestone Coal Group and the Productive Coal Measures. Present workings include fifteen major collieries, while two large modern pits designed to win coal from the Limestone Coal Group in the deeper, flatter and as yet largely untapped central portions of the basin are under construction. The annual output of coal is some four million tons and reserves, including that part of the undersea field extending about three miles from the shore, are calculated to reach 980 million tons. In recent years certain seams have been wrought opencast.

Oil-shales were formerly worked near Burdiehouse and Straiton. Other economic products of the coalfield include limestone, refractory clays and brick-clays, while oil and natural gas have been obtained by boring on the crest of the D'Arcy–Cousland Anticline. Blackband ironstone was formerly worked in the Lower Limestone Group at Gilmerton and in the Limestone Coal Group at

Loanhead and Roslin. Sandstones were quarried for building stone. Water is pumped from a number of bores and shafts, much of that derived from the latter being the product of mine drainage.

The thick mantle of glacial drift, which frequently covers the solid rocks and renders their detailed mapping difficult, includes large deposits of sand and gravel which form characteristic glacial features in the landscape and are widely quarried. Peat is worked on a small scale in the south of the field. A remarkable feature is the rarity of igneous intrusions.

Rivers and towns

The drainage of the area is carried by two main rivers. The North Esk and its tributaries drain the south-eastern flank of the Pentland Hills and the western portion of the coalfield. The South Esk is formed by the union of a number of streams which carry the surface waters of the southern and eastern region, though they rise beyond the coalfield in the higher ground approaching and forming the Moorfoot Hills. The North and South Esk unite below Dalkeith and flow thence to the sea at Musselburgh. Streams near Macbiehill flow south-east to the River Tweed and the extreme eastern portion of the coalfield comes within the watershed of the Tyne Water.

The city of Edinburgh lies a few miles to the north-west of the coalfield though its suburbs now reach the edge of the field at Gilmerton and there is a nearly continuous urban belt from Edinburgh along the coast to Portobello and Musselburgh. The largest town actually within the coalfield is Dalkeith, but in addition there are the mining towns of Loanhead, Bonnyrigg and Newton-grange (Newton Grange), the new housing estates of which sprawl over the neighbouring countryside. Penicuik lies some miles farther to the south-west. Much of the rest of the coalfield retains its agricultural aspect, broken in places by the presence of small coal workings or other industrial plant such as paper works, and during the last dozen years, temporarily at least, by large opencast coal workings.

Geological sequence

The formations recognized in the area are summarized below.

The classification of the Carboniferous given above is the traditional Scottish one, which is used on the current maps. It differs from that in use in England and Wales. Thus the Limestone Coal Group, the Upper Limestone Group and the whole, or at least the lower part of the Roslin Sandstone Group of Scotland fall within the Millstone Grit Series of England and Wales, which is synonymous with the Namurian Series. The Calciferous Sandstone Series and all but the uppermost limestone of the Lower Limestone Group of Scotland represent part of the Carboniferous Limestone Series of England and Wales, which is approximately the equivalent of the Dinantian or the Avonian Series.

Geological history

In some places there appears to be a passage between the Upper Old Red Sandstone and the lowest Carboniferous strata. At the south end of the coalfield, however, mapping suggests that the Upper Old Red Sandstone is absent and that the Carboniferous rests unconformably on Lower Old Red Sandstone.

Throughout the Carboniferous Period the area was a basin of deposition in which were laid down in a generally rhythmic manner a succession of mudstones, siltstones, sandstones and limestones. At the tops of certain of the first three, seatclays or seatearths were sometimes formed, often followed by coal seams. In the Calciferous Sandstone there are in addition several oil-shales. Though marked variations in the thickness of the recognizable groups of strata occur from place to place no important break in sedimentation is known until the Roslin Sandstone is reached. The lowest Carboniferous beds, belonging to the Cementstone Group and consisting of shales, cementstones and sandstones, were probably formed in inland sheets of water which were periodically desiccated (Macgregor and MacGregor 1948, p. 41). The succeeding Oil-Shale Group seems to have been formed to a large extent in lagoonal and estuarine waters. The burst of volcanic activity which occurred at the beginning of this period, so well recorded in the vents and extrusive rocks of Arthur's Seat and North Berwick, may have extended over the Midlothian area, for several flows of this age have been proved at depth in the D'Arcy (Midlothian No. 1) Oil Bore. South of Carlops there are lavas on a higher horizon in the group.

A widespread marine transgression is indicated by the Lower Limestone Group. In this formation marine limestones are prominent though they alternate with shales and arenaceous deposits betokening shallower water. Coal seams provide evidence of actual emergence of the area above water-level, but the group as a whole again forms a rhythmic succession.

In Limestone Coal Group times shallower water prevailed but was frequently interrupted by periods of emergence, for in the resulting belt of strata coal seams and seatclays are much more common than marine beds. The last named are represented by thin fossiliferous bands in the shales.

Coals are fewer in the Upper Limestone Group, in which arenaceous sediments predominate and the occasional limestones are thin.

With the oncoming of the Roslin Sandstone Group conditions changed again. Thin marine bands in the lower part of this formation tell of marine intervals, but much of the group consists of sandstone, sometimes coarse and feldspathic, with strong current-bedding and in places carrying bands of coal and shale fragments, characters which suggest deltaic conditions. Many of the clays and sandy clays, especially in the upper part of the group, are true seatclays, though coals are rare. The existence of several proved local unconformities adds weight to the suggestion that this was an unstable period of alternating deposition and erosion and that the deposits, formed close to land, were even at times elevated to form dry land. The strata of the group are often found to be much stained. The colours produced by the staining vary from red and yellow to purple, sometimes mottled. This colouration is considered to be of secondary origin but whether it dates from the end of the Carboniferous, as suspected for the Barren Red Measures (p. 113), or from an earlier time is not yet clear. The presence of a break in the sequence of floras of the Roslin Sandstone, generally known as the 'plant-break', has long been known (Kidston 1894; Clough and Gibson in Peach and others 1910, p. 244). Recently studies of the goniatites (Currie 1954, pp. 537–8) have emphasized the importance of this break in Scotland as also in parts of northern England. Thus while the Limestone Coal Group was deposited during the Lower Eumorphoceras Age (E₁) and the Upper Limestone Group and probably part of the Roslin Sandstone Group in the Upper Eumorphoceras Age (E₂), strata of the Homoceras (H),Lower Reticuloceras (R₁) and Upper Reticuloceras (R₂) ages, as well as part at least of the succeeding Gastrioceras (G) Age, appear to be absent. The indications are that an unconformity occurs in this part of the succession in Scotland (Trotter 1952).

It is difficult to define this break in the Roslin Sandstone Group. Nevertheless it seems at least likely that the upper part of the Roslin Sandstone, above the plant-break, will eventually be found to belong rather to the Productive Coal Measures than to the Millstone Grit as defined in the Pennine region of England.

The Roslin Sandstone Group is succeeded by the mudstones, sandstones, coals and seatclays of the Productive Coal Measures. Consisting of many sandstones, a number of thick coals, mussel bands and several marine bands, these measures compare closely with their counterparts in other coalfields, particularly in the rhythmic manner in which the same types of sediment are repeated again and again throughout the succession. They bear evidence of deposition under shallow or estuarine waters which frequently were so silted up that dry land or swamps arose, where seatclays or coals were formed; yet now and again depression was sufficient to allow the deposition of thin bands of marine shale. These beds persist in upward sequence for several hundred feet and are topped by a marine limestone correlated with Skipsey's Marine Band of the west of Scotland. The succeeding Barren Red Measures consist mainly of sandstones, mudstones and shales, the predominating colours being reddish purple and purple-grey with red, green and yellow mottling. It is probable that these beds were originally of a similar nature to the strata of the Productive Coal Measures but have been stained or otherwise altered after deposition. The alteration perhaps occurred when they formed the earth's crust immediately underlying a land-surface at the close of Carboniferous times and in the period preceeding the formation of the New Red Sandstone.

The Barren Red Measures are the youngest solid strata found in the area. Of Mesozoic and Tertiary rocks there is no trace, other than the quartz-dolerite dykes of the north end of the coalfield, and even these are believed to be of Permo-Carboniferous age. During this great lapse of time the Carboniferous rocks were folded and faulted, depressed and raised, probably several times. Their present structure, which is the sum of the effects of these movements, is that of an asymmetrical syncline, pitching to the north, very steep dips being the order on the west side and gentler dips on the east, with a flatter central portion. The main axis runs south-south-west and is displaced to the west at its southern end. Minor folds occur on the flanks. Important faults, including the Pentland Fault and the Vogrie Fault (Figure 18), traverse the rocks and there are many minor fractures.

Drift deposits, which cloak the solid formations, include products of the Great Ice Age such as boulder clay and mounds and spreads of sand and gravel. Channels, many of which are now dry, formed by the melt-waters of the ice and the deflected surface-drainage of the area, are striking features of the landscape, as also are the great spreads of outwash sands and gravels deposited along the lines of drainage at the close of the Ice Age.

Along the coast there is evidence of a fall in sea-level which has left raised beach deposits and features, generally known as the 100-ft, 50-ft and 25-ft raised beaches, marking the coast-lines of three successive periods. Recent river deposits include river terrace gravels and the alluvium of the modern flood-plains.

Palaeontology

It has not yet been found possible to undertake the examination of the fossils collected from the whole of the Carboniferous strata of the Midlothian Basin. Special attention has, however, been devoted to the palaeontology of the Upper Limestone Group, Roslin Sandstone Group and Productive Coal Measures.

References

CURRIE, ETHEL D. 1954. Scottish Carboniferous Goniatites. Trans. Roy. Soc. Edin., 62, 527–602.

KIDSTON, R. 1894. On the Various Divisions of the British Carboniferous Rocks as determined by their Fossil Flora. Proc. Roy. Phys. Soc. Edin., 12, 183–257.

MACGREGOR, M., and MACGREGOR, A. G. 1948. The Midland Valley of Scotland. 2nd edit. revised. British Regional Geology, Geol. Surv.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

TROTTER, F. M. 1952. Sedimentation of the Namurian of North-west England and Adjoining Areas. Liv. and Manch. Geol. J., 1, 77–112.

Chapter 2 Calciferous Sandstone

Introduction

In West Lothian and parts of Midlothian the junction between Carboniferous and Upper Old Red Sandstone is thought to be conformable, the dividing line being taken at a change of fades. Thus the highest Old Red beds are predominantly arenaceous, red in colour and carry fish remains, including the characteristic genus Holoptychius (Peach 1905, p. 89). The lowest beds of the Carboniferous are also arenaceous but include intercalations of argillaceous sediments bearing lamellibranchs, ostracods and fish remains. The plants show Carboniferous affinities (e.g. Asterocalamites and Alcicornopteris)as emphasized by Kidston (1894, 1924) and this applies also to the fish remains (Traquair 1903). Robertson (in Anderson and Simpson 1938) has indeed suggested that there may be interdigitation of the two facies.

The mapping of the south end of the Midlothian Coalfield, however, suggests that there the higher beds of the Carboniferous successively overlap lower strata of that formation and rest unconformably on Lower Old Red Sandstone volcanic and sedimentary rocks.

The Calciferous Sandstone crops out all round the margin of the Midlothian Basin. The narrow outcrop along the western side from Portobello to Carlops is due partly to the steep dip of the beds and partly to the fact that some strata are cut out by the Pentland Fault. Minor folds cause a repetition of beds in a number of districts (p. 120). Between Straiton and Carlops the strata are much obscured by drift except for the exposures at Bilston Burn and Glencorse. At Carlops the thin outcrop is partly due to the regional thinning of the strata, the succession there being less than a quarter of the thickness at Straiton. Round the south end of the basin from Carlops to Macbiehill, between the Pentland Fault and the Leadburn Fault (a branch of the Southern Upland. Fault) the belt of gently inclined Calciferous Sandstone is mapped as resting unconformably on the Lower Old Red Sandstone. From Macbiehill to Herbershaw the subdivision is cut out by the Leadburn Fault. On the east side of the nose of Ordovician strata around Spurlens Rig, which projects northwards into the Midlothian Basin, a large area of Calciferous Sandstone is mapped between Cockmuir and Gladhouse, but owing to the drift cover there is little information about the nature of the measures there. It is possible that the red sandstones of Toxside Quarry and Tweeddale Burn, as well as the red-coloured lower beds in Mount Lothian No. 1 Bore (p. 15), are of Upper Old Red Sandstone age. Farther north-east, however, the red- and purple-stained sandstones of the Currie Glen, half a mile south-east of Borthwick, have yielded Asterocalamites during the recent re-survey, thus confirming the original reference of these strata to the Carboniferous (Peach in Peach and others 1910, p. 175). Between Glad-house Reservoir and the escarpment of the Moorfoot Hills the drift-covered area, shown on the one-inch map Sheet 24 (1932) as Ordovician, is now considered to be underlain by Calciferous Sandstone or Old Red Sandstone or both. This interpretation, which is essentially that adopted on the 1868 edition of the one-inch map and also on the quarter-inch Sheet 15 (1912), is supported by the discovery of a fault-belt with a well-developed fault-breccia which runs south-westwards between Hog Hill and Jeffries Corse and is in line with the fault-scarp of the Lammermuir Fault (Figure 18). Although shown on the map as bounded by faults in this district, the Calciferous Sandstone may in part rest unconformably on the lower formation as in the West Linton district.

From Gladhouse to Middleton, drift deposits almost entirely conceal the solid rocks. Between Middleton and the Tyne Water the strata, consisting mainly of sandstones, crop out in a gentle anticline plunging north-north-eastwards, but interrupted by north-easterly trending faults. Along the D'Arcy–Cousland Anticline the Calciferous Sandstone rises almost to the surface and has been proved in the oil and gas bores.

The Calciferous Sandstone is divided into a lower, Cementstone Group and an upper, Oil-Shale Group (Figure 3).

Cementstone Group

In the Edinburgh city area the Cementstone Group consists mainly of sandstones with interbedded shales, mudstones, argillaceous limestones known as cementstones, and occasional fossiliferous bands. In the Midlothian Coalfield the Cementstone Group has not been mapped separately, but a thick sandstone with rare fossiliferous shale-bands found below the lavas in the D'Arcy (Midlothian No. 1) Boring is regarded as belonging to this group (Robertson in Anderson and Simpson 1938, p. 31).

Oil-Shale Group

At the top of the Cementstone Group normal sedimentation was interrupted by the extrusion of the Arthur's Seat lavas and tuffs. These volcanic rocks were proved in the D'Arcy Bore though they were considerably thinner than at Arthur's Seat. They have not been found elsewhere in the basin.

The older sediments of the Oil-Shale Group do not differ greatly from those of the Cementstone Group, but there is a gradual increase in bituminous beds, and fossils, mostly non-marine, become more common. Occasional marine bands occur, especially in the upper part of the group, where beds with non-marine shells are insignificant. The sedimentation takes on the marked rhythmic character so well known in the Yoredale Beds (Hudson 1924). The rhythm may be expressed as the repetition in upward succession of the following sequence of beds—coal, shale, limestone, shale, oil-shale, shale, sandy shale, sandstone, seat-earth, coal. Individual members of the rhythm may be absent in any given case (Richey 1937, p. 98). In the Oil-Shale Group the majority of the limestones are non-marine (Macgregor 1938) most frequently containing ostracods and Spirorbis. Beds of tuff occur rarely, but greenish marls and mudstones which may have been derived from volcanic debris are less rare. Disturbed bedding is frequent and results from a variety of penecontemporaneous causes such as desiccation cracks, slump structures, animal tracks and burrows as well as plant-roots.

The higher beds contain a greater number of oil-shales including seams of economic value considered to be equivalent to those at the well-known Pumpherston, Dunnet, Broxburn and Fells horizons of West Lothian.

Details

Cementstone Group

In the Edinburgh city area the thickness of the Cementstone Group was found to be a little over 700 ft. The strata consist of alternating shales and mudstones with thin bands of non-marine limestone, together with some sandstone commonly green and red in colour. In the D'Arcy (Midlothian No. 1) Bore the base of the Arthur's Seat Volcanic Group was thought to have been reached at 3382 ft. Below this the succession proved was as follows, but only part of the bore was cored: white to grey-green sandstone, red in parts, often calcareous with bands of greenish micaceous 'marl' or shale 211 ft; black shale with ironstone nodules, lamellibranchs, ostracods, fish scales and plant-stems 6 in., resting on sandstones, similar in character to those above, which yielded scales of Holoptychius. The last named are considered to belong to the Old Red Sandstone.

Oil-Shale Group

Lower Oil-Shale Group

By definition the Lower Oil-Shale Group includes beds from the base of the Arthur's Seat Volcanic Group to the base of the Burdiehouse Limestone. In the Midlothian Coalfield it has not been possible to recognize the subdivisions of the Lower Oil-Shale Group shown on (Figure 3). This figure gives a conjectural section based on information available in the Edinburgh city area and from the borings in the D'Arcy–Cousland district. In particular the thickness between Hailes Sandstone and Burdiehouse Limestone is uncertain. The best sections are provided by the D'Arcy and Cousland bores sunk for oil and gas on the axis of the D'Arcy–Cousland Anticline (Lees and Taitt 1945). A feature of these boreholes is the frequency with which sandstones are repeated in the succession. The thickness of the Lower Oil-Shale Group in the D'Arcy Bore is 2632 ft, apparently much less than that postulated for the Edinburgh district, but it must be remembered that the latter is calculated from surface mapping and may be an overestimate. The Cousland bores were drilled through measures which are steeply dipping in places and may be faulted; the true thicknesses are therefore uncertain. Frequent fossiliferous beds occur. Of these the Pumpherston Shell-Bed appears to be represented in the Cousland Bore by marine limestone and marine shale. At D'Arcy the same bed lay at a greater depth from the top of the Oil-Shale Group. The associated oil-shales were recorded in the Pentland Diamond Bore near Straiton (Figure 4) where they were found to be thin and impure; on the east side of the basin they seem to be missing as they were not recognized in the D'Arcy and Cousland bores.

Upper Oil-Shale Group

The base of the Upper Oil-Shale Group is taken at the bottom of the Burdiehouse Limestone, an unusually thick non-marine limestone. Similar but thinner beds frequently occur both above and below this horizon. The Burdiehouse Limestone is 30 ft thick at Burdiehouse and Straiton and of excellent quality (Robertson and others 1949, p. 143). At the latter place it is still mined; it is pale grey in colour and fine-grained with plant and fish remains as well as ostracods. A thin rib of chert occurs in the lower part. The limestone thins towards Carlops and also in the Cousland direction, where it appears to be represented by the uppermost of two thin limestones (Figure 5).

In the shales above the limestone an oil-shale 1.5 ft thick was recorded in No. 23 Bore on the Straiton estate. This may be the equivalent of the Camps Oil-Shale of West Lothian (Figure 5); the quality is not known and the Pentland Crosscut Mine section does not record an oil-shale at this horizon. In the Cousland Bore a thin oil-shale (Figure 5) was found above the supposed Burdiehouse Limestone.

The Carlops 'lava' is a vesicular basalt of Dalmeny type, which lies not far above the limestone taken in that district to be the Burdiehouse. There is some uncertainty as to whether it is an intrusion or a lava-flow. In some places it has a rotted top, penetrated by plant-roots (Richey 1926, p. 109); elsewhere induration of the overlying beds is reported. Different sediments certainly rest on it in different places. A possible explanation is that the lava ploughed into unconsolidated sediments. Hinxman (in Peach and others 1910, p. 171) refers to the olivine-basalt lavas cut in Penicuik Bore C (Figure 4) near Eight Mile Burn, a remark which suggests that more than one flow was present in the 100 ft of green marl and whin reported in the borer's log.

The igneous rock recorded in the Cousland Bore at a similar horizon (Figure 5) is also vesicular and was considered to be a basalt lava of Dalmeny type (Anderson and Simpson 1938, pp. 29–30). Fissures in the top of the basalt were filled with the overlying sediment.

A decomposed lava crops out in a faulted inlier in the Currie Glen near Borthwick. The top is veined with carbonate and pale green material which may be sedimentary. Its base is not exposed but up to 10 ft of red mudstone and tuff overlie the basalt and in turn are overlain by massive red- and purple-stained, mostly fine-grained sandstones. There is no evidence as to the horizon of this lava but its character is somewhat similar to that of the lava in the Cousland Bore.

The Pentland Shale, which is correlated with the Dunnet Shale of West Lothian, is the thickest oil-shale developed in Midlothian. It varies from 5.5 to 6.5 ft thick and the roof was stated to be soft blaes. It was worked to a considerable extent between Straiton and Burdiehouse, a distance of two miles along the strike of the beds, and was followed down dip to a depth of 1175 ft from the surface near Loanhead. The yield was 25 to 26 gal of crude oil and 20 to 23 lb of ammonium sulphate per ton of shale. A reference by Traquair (1903, p. 692) to "cephalopodous shells in the roof shale" presumably refers to the Pentland Shale. From a recent exposure of strata in a subsidence-pit, 410 yd S. 21° E. of Burdiehouse Mains, crinoid columnals, an orthocone Nautiloid and indeterminate goniatite fragments were obtained from silty mudstone 8 ft above this seam. If this marine band is the Dunnet Shell-Bed of West Lothian the Pentland Shale must be the equivalent of the Under. Dunnet Seam of that region (Carruthers in Carruthers and others 1927, pp. 55, 56). A seam of oil-shale 2 ft thick, which may correspond to the Main Dunnet, was recorded 20 ft above the Pentland Shale in the Pentland Mine (Figure 5). At Carlops the Carlops Shale, lying 12 to 28 ft above the lava, is correlated with the Pentland Shale. It is 3.5 to 4 ft thick; the analysis is not known but the quality was said to be good (Peach in Peach and others 1910, p. 171). Although proved by a number of bores it was never worked.

In the Cousland Bore the Pentland Shale is probably represented by an impure oil-shale reported to be 3.5 ft thick at a depth of 682 ft.

Thick limestones were recorded in the Pentland Mine (Figure 5) below the Broxburn Shale, at what would be the Dunnet Marls horizon, though in the new Bilston Glen Colliery sinking (Figure 4) only calcareous sandstones and rare thin limestones were found at this level. The Broxburn Shale of Straiton is up to 4 ft in thickness and was worked for about a mile along the strike. It had a roof of strong blaes and a soft pavement. The yield was 20 to 22 gal of crude oil and 20 to 21 lb of ammonium sulphate per ton. An oil-shale, 1 ft 8 in. thick was recorded 12 ft below it, resting on the topmost limestone band. A thin oil-shale between the Carlops Shale and the Pleurotomaria Beds was recorded in some bores near Carlops and may represent the Broxburn Shale.

In the Cousland No. 1 Oil Bore an oil-shale 630 ft from the surface and estimated to be 4 ft thick, was considered to be the Fells Shale (Anderson and Simpson 1938, p. 28). The presence of Anthraconauta sp.in the overlying strata may be compared with the occurrence of the same fossil in measures above the Broxburn Shale in the West Calder area (Mitchell 1955, p. 44) and tends to support the correlation, made on lithological grounds, with the Broxburn rather than with the Fells Shale.

The Fells Shale was the least worked of the Straiton oil-shales. In the Straiton workings thicknesses ranging from 1 ft 8 in. to 3 ft were recorded. An average of 2 ft is mentioned by Carruthers (in Carruthers and others 1927, p. 103). The Fells Shale was, however, the richest shale here, yielding 34 to 35 gal of oil and 10 to 19 lb of sulphate of ammonia per ton.

The Houston Coal may be represented in the Straiton estate by a seam 18 to 22 in. thick at the base of a group of seatclays with coaly bands, proved by a number of chisel-bores. A well-marked coaly band at the top of these clays is overlain by an 8-in. rib of coaly, grey shale which suggests correlation with the 'Grey Shale' of West Lothian (Figure 5). Green sandy marl was logged above it—a possible equivalent of the Houston Marl. A similar development has been found in the new Bilston Glen Shaft.

There are no coals developed in the Carlops succession but in the Cousland Bore a coal up to 2 ft thick may represent one of these coals or the overlying Two Foot Coal.

At Niven's Knowe, a mile west-south-west of Loanhead, shales with a thin impure oil-shale near the top are exposed on the bank on the north side of the road. They dip under the Niven's Knowe Sandstone which was worked in the nearby quarry. Overlying the sandstone on the south side of the road are shales with ironstone bands yielding ostracods and fish remains. These in turn are overlain by shales, silty in part and possibly partly decalcified, with gastropods and other marine fossils. Blocks of papery oil-shale occur nearby but this rock was not seen in place. The marine band compares with the Pleurotomaria Beds of Carlops and may represent the Raeburn Shell-Bed of West Lothian (Figure 5). The oil-shale perhaps corresponds to the Paper Shale referred to in the Straiton area by Grant Wilson (in Peach and others 1910, p. 167), which was then estimated to lie 230 ft above the Fells Shale of Straiton and which was considered to represent either the Raeburn or the Mungle Shale of West Lothian.

The Straiton Estates bores of 1868 proved two poor oil-shales, separated by about 100 ft of shales and sandy shales, which, because of the absence of a sandstone between them, may represent the Raeburn and Fraser shales. The lower was recorded as shaly blaes, 2 ft 3 in. thick, and the upper as 1 ft 3 in. of foul shale. At Carlops the oil-shale bands immediately below and above the Pleurotomaria Beds are thin and impure.

The Cephalopod Limestone is a persistent horizon along the west side of the Midlothian Basin. It consists of a calcareous mudstone with cephalopod fragments and a crinoidal limestone together amounting to about 5 ft in thickness. Blaes with thin oil-shale bands sometimes occur in association. The former exposure in the Bilston Burn, now covered up, showed two separate crinoidal limestones (Grant Wilson and Bailey in Peach and others 1910, p. 169), but it is possible that there is some repetition by folding and faulting. About 100 ft above the limestone here two thin coals occur 9 ft apart, the lower being 12 in. thick in two leaves. The upper, reported to be 2 ft thick, consists of 9 in. of cannel resting on a seatclay, the top inch or two of which is coaly and contains large fish-teeth.

The Bone Bed Limestone (Figure 6) is also a persistent horizon. It is similar to the Cephalopod Limestone, being crinoidal, and reaches a thickness of 3 ft, overlain by a calcareous mudstone. All along the western crop from Gilmerton to Carlops, a characteristic band of soft blaes an inch or two thick, full of Rhipidomella, occurs at the base of the limestone. In blaes with sandy ribs below this, layers and pockets with fragments of Lingula and fish remains form the so-called Bone Bed. A coal, up to 6 in. thick, is found a short distance below the bone bed. A thick development of blaes, with ironstone ribs, occurs above the limestone. In the Glencorse Burn where these strata are well exposed, Lingula and marine lamellibranchs occur 9 ft above the limestone whilst Anthraconauta sp.is found 8 ft 6 in. and 13 ft above the Lingula. Similar faunal sequences are known in the Bilston Burn and in the Burdiehouse Burn at Moredun.

Round the southern margin of the coalfield little is known of the succession in the Upper Oil-Shale Group. In Mount Lothian No. 1 Bore 1 ft 6 in. of limy fakes was recorded 59 ft below the base of the limestone taken to be the Gilmerton. Below this the bore journal records in downward succession: alternating white sandstones, shales and clays 128 ft; marl 67 ft 5 in.; sandstones and shales 76 ft 8 in.; hard bastard limestone 2 ft; red clays and shales and white sandstone 48 ft; red marl and hard limy ribs 50 ft; red shales and white sandstone 86 ft.

At a similar horizon on the left bank of the River South Esk, 350 yd downstream from the Gladhouse Reservoir dam, a thin limestone and shales with marine fossils occur with characters suggesting the Cephalopod Limestone. In the burn at North Middleton, 130 yd downstream from the main road, a thin argillaceous limestone with gastropods was found, but here the Calciferous Sandstone is faulted against the Lower Limestone Group. At Crichton and in the Cousland bores (Figure 5), (Figure 6) two thin marine limestones and associated marine shales lie below the Lower Crichton Limestone. Anderson and Simpson (1938, p. 28) suggested a correlation with the Fraser and Rae-burn shell-beds, though here (Figure 4), (Figure 6) a slightly different correlation is proposed.

It will be seen in (Figure 6) that the successions below the base of the Gilmerton Limestone on either side of the Midlothian Basin are rather different. There appear to be two possible correlations. Either the Bone Bed Limestone has changed its character and is represented by the Lower Crichton Limestone or the latter is an additional limestone between the Gilmerton and Bone Bed not developed on the west side. The correlation adopted on the maps is that shown in (Figure 6). This view is not, however, expressed on 6-in. map Haddington 9 S.W. where the base of the Lower Limestone Group was drawn at an early stage of the revision at the base of the Lower Crichton Limestone. This is an East Lothian map which adjoins 6-in. Edinburgh 4 S.E. to the east. The correlation is based on a number of points of similarity between the Gilmerton Limestone in its type area and the Upper Crichton Limestone. Thus both limestones are crinoidal and in each it is the lower part which has been worked for lime. Below each limestone and resting directly on a coal is a thin argillaceous limestone or calcareous shale with abundant Productid shells. Furthermore the Lower Crichton Limestone is dolomitic and has not been worked.

The best section of these beds is given by the Crichton No. 8 Bore which reads: limestone (Upper Crichton), part crinoidal, part decalcified 16 ft 3 in. seen; limy blaes with argillaceous limestone 6 ft 3 in.; argillaceous limestone with abundant shells, mainly small Productids 3 ft; coal, bright 9 in.; fireclay, silty in parts with black roots 3 ft 9 in.; mudstone, pale greenish-grey 2 ft; limestone (Lower Crichton) pale grey, rather nodular with argillaceous bands and crinoidal in parts 9 ft 4 in.; fakes and blaes with Lingula and traces of other shells 5 ft 5 in. on coal, foul 1 ft.

The whole of this section, with the exception of the lower coal and the fakes and blaes above it, was originally known as the No. 1 Limestone of Tyne Water and was equated with the Gilmerton Limestone (Crampton in Peach and others 1910, p. 191 and below p. 23). The presence of the intervening coal and fireclay was not known at that time.

References

ANDERSON, F. W., and SIMPSON, J. B. 1938. Geological Notes on the Borings for Oil now in Progress at Cousland and D'Arcy, Midlothian. Oil Shale and Cannel Coal, 27–31, Inst. Petroleum.

CARRUTHERS, R. G., CALDWELL, W., BAILEY, E. M., and CONACHER, H. R. J. 1927. The Oil-Shales of the Lothians. 3rd edit. Mem. Geol. Surv.

HUDSON, R. G. S. 1924. On the Rhythmic Succession of the Yoredale Series in Wensleydale. Proc. Yorks. Geol. Soc., 20, 125–35.

KIDSTON, R. 1894. On the Various Divisions of British Carboniferous Rocks as determined by their Fossil Flora. Proc. Roy. Phys. Soc. Edin., 12, 183–257.

KIDSTON, R. 1924. Fossil Plants of the Carboniferous Rocks of Great Britain. Mem. Geol. Surv., Palaeont., 2, 377–522.

LEES, G. M., and TAITT, A. H. 1945. The Geological Results of the Search for Oilfields in Great Britain. Quart. J. Geol. Soc., 101, 255–317.

MACGREGOR, M. 1938. Conditions of Deposition of the Oil Shales and Cannel Coals of Scotland. Oil Shale and Cannel Coal, 6–18, Inst. Petroleum.

MITCHELL, G. H. 1955. In Sum. Prog. Geol. Surv. for 1954, 43–5.

PEACH, B. N. 1905. In Sum. Prog. Geol. Surv. for 1904, 89–90.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. H., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

RICHEY, J. E. 1926. In Sum. Prog. Geol. Sum. for 1925.

RICHEY, J. E. 1937. Areas of Sedimentation of Lower Carboniferous Age in the Midland Valley of Scotland. Sum. Prog. Geol. Sum. for 1935, pt. 2, 93–110.

ROBERTSON, T., SIMPSON, J. B., and ANDERSON, J. G. C. 1949. The Limestones of Scotland. Mem. Geol. Surv., Min. Resources, 35.

TRAQUAIR, R. H. 1903. On the Distribution of Fossil Fish-remains in the Carboniferous Rocks of the Edinburgh District. Trans. Roy. Soc. Edin., 40, 687707.

Chapter 3 Lower Limestone Group

General account

In the Midland Valley of Scotland the base of the Lower Limestone Group is customarily taken at the bottom of the Hurlet Limestone (Macgregor and MacGregor 1948, p. 35). In Midlothian, Clough (in Peach and others 1910, p. 161) considered that the equivalent bed is the Gilmerton Limestone, but in the 1930 edition of the one-inch geological map Sheet 32, the underlying Bone Bed Limestone was regarded as the lowest bed of the group. A review of the evidence, coupled with some additional information from borings at Baads and Harwood mines in West Lothian, supports the former correlation. In consequence, on the current maps, the Gilmerton Limestone is taken as the basal bed of the Lower Limestone Group. The top of the group is taken at the top of the Top Hosie Limestone but in certain places where this bed is absent some difficulty arises (p. 25).

Lithological character

The Lower Limestone Group contains a greater thickness of marine limestone than any other subdivision of the Carboniferous in Scotland; the limestones form three main beds. These were formerly numbered from the bottom upwards, Nos. 1 to 3 (Howell and Geikie 1861, p. 73). Individual limestones were described by Robertson (in Robertson and others 1949). In addition many of the shales are calcareous. The lithology of the group thus differs appreciably from that of the underlying Oil-Shales though rhythmic sedimentation persists, but with different members of the cycle dominant. The cyclic sequence was described by Macgregor and Manson (1935, p. 126), Richey (1951, p. 97) and by Robertson (1948). Bituminous beds are rare; coals are better developed and, though only one is now worked, three seams have been wrought in the past. Sandstones are important. The decalcification of limestones by weathering has locally led to the formation of beds of ochre and in places has reached a considerable depth from the surface. Thus ochre is recorded at 78 ft in Bilston Glen No. 2 Shaft on the horizon of the Gilmerton Limestone. In No. 1 Shaft of the same colliery 'limestone broken with fissures and ochre' was noted at 320 ft. Solution cavities and swallow-holes are present in some areas while bands of fractured limestone such as those seen in the Burn Quarry, Esperston are probably due to collapsed caverns.

Dolomitic limestone (Robertson and others 1949, pp. 24, 29–30) usually occurs in the uppermost parts of the thicker limestones such as the Bilston Burn and North Greens limestones. The Lower Vexhim Limestone is dolomitic in the Esperston district. While these dolomitic bands may be primary, clear evidence of secondary dolomite crossing the bedding planes of limestones adjacent to fault-planes and joint-planes is also found. Both types are known to the quarrymen as 'dun beds'.

Outcrop

Theoutcrop of the Lower Limestone Group forms a narrow belt from Portobello to Carlops, broken only by faulting and by a marked sinuosity at Gilmerton due to folding. From Carlops the outcrop extends around the southern edge of the Midlothian Basin widening between Howgate and Borthwick as the dip decreases. Inliers occur in the core of the Cousland Anticline near D'Arcy and Cousland.

The group is thickest between Portobello and Loanhead ((Figure 7); Goodlet 1957). As happens in both the Limestone Coal Group and the Upper Limestone Group it thins rapidly southwards and less markedly eastwards. In these directions the limestones become more pure and compact, which suggests an increase in distance from the source of terrigenous material.

The generalized succession of the Lower Limestone Group is shown in (Figure 8), in which the principal named beds are indicated and a suggested correlation given with the same group in Fife, West and East Lothian. Detailed sections within the Midlothian Coalfield are included in (Plate 2). In some sections thicknesses given depend on a somewhat arbitrary distinction in hand-specimens between limestone and calcareous shale or sandstone. For example the Top Hosie Limestone often passes laterally and vertically into calcareous sandstone without any appreciable break.

Details

Gilmerton Limestone to base of Dryden Limestone

Gilmerton Limestone

The Gilmerton Limestone was defined by Gibson and Bailey (in Peach and others 1910, p. 180) as consisting at Gilmerton Quarries of a basal bed of crinoidal limestone 10 ft thick overlain by 50 ft of evenly bedded grey limestone. The most northerly exposure was recorded (Milne 1839, p. 341) at Easter Duddingston (Mains) Farmhouse. Farther south, near Niddrie House, the limestone was reported to have been worked in a line of old quarries now filled up. Six feet of limestone are exposed in a quarry 500 yd N. by E. of Edmonstone House. About two miles south of Niddrie House in the old Ferniehill Quarries south of Ferniehill Road the following section occurs: sandstone with blaes bands at base 12 ft; limy blaes 10 ft; limestone, grey, fine-grained 35 ft, on limestone, massive, grey, crinoidal 10 ft.

A good exposure of the base of the Gilmerton Limestone and the underlying beds occurs in the Burdiehouse Burn. South of the Moredun Basin where the limestone resumes an easterly dip, the basal bed, 10 ft thick, was worked in the old Gilmerton Quarries for three-quarters of a mile along the crop and in places was followed underground in mines. It is not exposed again until the Bilston Burn is reached, where in the natural section, as well as in the new Bilston Glen Colliery shafts, the limestone has suffered nearly complete decalcification (p. 17). Thus at the outcrop it is represented by 21 ft of ochre, some thin ribs of minutely crinoidal limestone being seen at the base of the overlying blaes.

In the Glencorse Burn, upstream from Miltonbridge, the section is: sandstone, yellow, gritty at base; sandstone, faky, lower part very crinoidal 1 ft 4 in.; limestone, grey, yellow-weathering, upper part very crinoidal, the whole partly decalcified and probably dolomitized (Gilmerton) 22 ft; blaes, grey 2 ft; limestone, argillaceous, crammed with squashed Productids and with coal streak 5 in., on coal 11 in.

The upper, flaggy part of the limestone was perhaps eroded before the sandstone was deposited. The limestone was originally believed to be the North Greens Limestone (Hinxman in Peach and others 1910, p. 183; Robertson and others 1949, p. 144). It is exposed only 40 yd upstream from the crop of the Lower Vexhim Limestone, the dips being 50 to 60 degrees. The proximity of the two is now considered to be due to a large fault which cuts out the North Greens Limestone and its associated beds.

About two miles to the south-west, near the Cuiken Burn, some old borings cut parts of the Lower Limestone Group, but correlation is difficult owing to the steep dips. The limestone at the bottom of Penicuik No. 83 Bore, 600 yd N.N.W. of Corn-bank, referred to by Hinxman (in Peach and others 1910, pp. 180, 182) as a bore to the south-west of Mauricewood Colliery, was considered by him to be the Gilmerton Limestone, which is the present interpretation. It may possibly be the North Greens Limestone, however, an interpretation supported by the steep dip.

In the area south of Penicuik the Gilmerton Limestone varies from 10 to 35 ft, the latter thickness probably including calcareous shale. There are borings but no natural exposures between here and Nine Mile Burn, where an ochre bed 20 ft thick is taken to represent the Gilmerton Limestone. The base of this bed, containing a skeletal siliceous network with casts of marine fossils, rests on a 12-in. coal. It is next exposed in a small faulted inlier in the River North Esk, 400 yd S.W. of Newhall House. Farther upstream the top of the limestone is seen about 150 yd S. of Amazondean House. It is possible that in this district the overlying Dryden Limestone has been included with or mapped as the Gilmerton.

In the quarries about a quarter of a mile east of Carlops a limestone, mapped as the Gilmerton, is partly exposed, the section in downward order being: limestone, platy with shells and crinoids 6 ft; blaes with shells 12 ft; limestone (worked), about 5 ft. The Gihnerton Limestone is again seen in the disused Carlops Quarry 100 yd to the south across a small fault.

The crop of the Gilmerton Limestone is marked by a line of quarries running south-south-east from the old Whitfield Limeworks a mile south-east of Carlops, to Whitfield Quarry. There is no complete exposure but the downward section is: limy blaes and limestone bands 12 ft; limestone post, crinoidal with numerous marine fossils 5 ft.

At Macbiehill, Braefoot Cottage and Lamancha there are old quarries with exposures of crinoidal limestone. In the quarry about 200 yd S.E. of Whim House the following section was recorded in downward succession: fakes, grey, sandy with occasional shells 7 ft; shale, dark grey 2 ft; shale, calcareous with fossils 3 ft; limestone, massive, grey crinoidal 6 ft.

The Gilmerton Limestone was worked in quarries 0.75 of a mile W. of Mount Lothian cross-roads, and beside the Fullerton Burn just under a mile south-east of the crossroads. At the quarry 0.25 of a mile S. of Upper Side the downward section was : sandstone, yellow 12 ft; sandstone, shaly 7 ft; shale 1 ft; limestone, crinoidal, impure in parts 5 ft; shale, crinoidal 1 ft 4 in.; limestone very crinoidal 2 ft. In another part of the quarry lower beds are exposed consisting of pale fine-grained limestone, crinoidal in places, with clumps of Lithostrotion.

The limestone with Lithostrotion is again exposed in an old quarry 300 yd S.S.W. of Gladhouse (Rosebery) Mains. In the Middleton North Burn nearly 0.75 of a mile S.S.E. of Esperston Farm the top of the Gilmerton Limestone is seen forming the crest of a small anticline, believed to be cut off by a fault to the south. The limestone is next visible in the quarry on Common Hill 0.75 of a mile S. of North Middleton, the downward succession being: shale and sandstone 3 ft; limestone, silty, crinoidal 3 ft; shale and calcareous sandstone with worm-pipes 1 ft 3 in.; limestone, compact, hummocky bedding, Productids and simple corals 8 to 10 ft. In the ground between here and the Tyne Water at Crichton there are no exposures, but in the latter district the Upper Crichton Limestone (Figure 6), (Figure 8); (Plate 2) is regarded as the equivalent of the Gilmerton Limestone. A quarry 200 yd N.W. of Crichton church shows the following section: sandstone 15 ft; shale, calcareous, and nodular limestone bands, Shelly and crinoidal in part, 4 ft on limestone, crinoidal, compact with hummocky bedding and rare patches of Lithostrotion 9 ft. Nearby the limestone has been proved by bores such as Crichton No. 8 (p. 16) in which it had a thickness of at least 16 ft 3 in.

The Upper Crichton Limestone has been proved at the surface on the crest of the Cousland Anticline about 0.25 of a of a mile E.S.E. of D'Arcy and again 0.25 of a mile S.W. of Fordel Mains.

Between Gilmerton and Bilston Burn from 10 to 14 ft of shale overlie the Gilmerton Limestone. At Gilmerton these measures were described as calcareous and fossiliferous; at Bilston and Green Park thin limestone ribs near the base consist of crinoid ossicles and the shale is traversed by worm-tubes. A sandstone, flaggy and ripple-marked in the lower part, follows at Bilston and interbedded with it is another shale-band, 10 ft thick, again with worm-tubes. The Dryden Limestone rests directly on the sandstone.

In Glencorse Burn on the other hand sandstone immediately overlies the Gilmerton Limestone. The top 4 in. of sandstone, being crinoidal and calcareous, may mark the oncoming of the Dryden Limestone. Southwards the sandstone fails and the two limestones are separated by calcareous shales. It reappears, however, in the Crichton area.

Dryden Limestone to base of North Greens Limestone

Dryden Limestone

TheDryden Limestone crops out in Bilston Burn, 250 yd N. 4° E. of Dryden Tower, where the section is: shale with ironstone nodules; limestone, shaly with brachiopods 6 in.; limestone, hard, crinoidal, sandy in part 2 ft; limestone, sandy, and calcareous sandstone, with small marine fossils 2 ft on sandstone, faky and rooty at top. The Dryden Limestone has not been recognized on the eastern side of the Midlothian Basin except at Crichton.

A sandstone overlies the Dryden Limestone and passes up into a seatclay underlying the North Greens Coal. At Greenend, however, a parting of blaes with ironstone 6 ft above the base of the sandstone contains a 5-in. coal. Another coal 8 in. thick occurs near the base of the seatclay and only 5 ft below the North Greens Coal. At Bilston Burn only the blaes was found.

North Greens Coal

TheNorth Greens Coal, which has a seatclay floor and a blaes roof carrying Lingula is one of the best seams in Midlothian. Its maximum thickness—parrot 10 in. on coal 3 ft 11 in.—was recorded in the Niddrie Colliery Crosscut Mine, the usual working thickness being 3 ft 11 in. to 4 ft 3 in.

The most northerly record of the seam is from the railway cutting at Portobello, where the waste was exposed about 250 yd E. of N. from Duddingston Mains. From here to Gilmerton Colliery it has been worked in many places along the outcrop and to the dip, including the outlier of the coal in the Moredun Basin. At Ramsay Pit it varies from 3 ft to 3 ft 8 in., the section measured in the 156-fm Crosscut Mine being: blaes with Lingula; blaes, firm 1 ft; coal, splint 1 ft 7 in. on coal, rough 2 ft. At Burghlee and Dryden 3 ft 8 in. to 4 ft 1 in. were recorded and at Roslin 2 ft 7 in. to 3 ft 1 in.

The seam is not important south of Roslin, though Milne (1839, p. 264) refers to it at Glencorse, where he recorded 6 in. of parrot in the coal, which implies that it was worked there. Penicuik No. 83 Bore passed through 4 ft 6 in. of coal but as the dip was 60 degrees the true thickness is 2 ft 3 in. This seam is here taken as the North Greens Coal but there is a possibility that it is the Under Vexhim Coal.

Throughout the remainder of the southern part of Midlothian it has not been worked, being either too thin or absent. On the east side of the basin the coal is 2 ft 6 in. thick at Dalkeith Colliery where it was wrought to a limited extent. The same thickness was proved at Carberry No. 29 Bore (Plate 2). The coal has yet to be proved under the main basin.

Beds between the North Greens and Rough Parrot coals

The beds between the North Greens and Rough Parrot coals consist of shales, with a Lingula bed near the base, succeeded by sandstone. Along the western crop the sandstone is frequently absent, while the blaes is occasionally missing, as in the Fordel Mains Bore. The Lingula bed above the North Greens Coal is known from Moredun to Bilston Burn, the only other possible record of it being in Crichton No. 4 Bore (Plate 2).

Rough Parrot Coal (Gilmerton Ironstone)

Lying halfway between the North Greens Coal and the North Greens Limestone the Rough Parrot Coal has occasionally been mistaken for the former, to which it bears a marked resemblance (Gibson and Bailey in Peach and others 1910, pp. 178–9). Sections were recorded as follows in downward sequence: Niddrie: blaes; coal 1 ft; blaes 10 in.; coal 1 ft 6 in. sandstone. Greenend bores, Moredun: blaes with Lingula, occasionally parrot at base; coal, free 5 to 8 in.; coal, parroty 2 ft 3 in.; coal, free 0 to 9 in.; fireclay.

The seam deteriorates to the south and near Gilmerton an ironstone, known as the Gilmerton Ironstone, comes in at this horizon. A section of the ironstone taken at Gilmerton (Macgregor and others 1920, p. 170) shows: blaes 8 ft; blackband 1 ft 3 in.; fireclay 6 in.; parrot coal 1 ft 3 in. on free coal 8 in. The measures were exposed in the Ramsay Pit 156-fm Crosscut Mine as follows: blaes, soft with ironstone nodules, Lingula and fish remains at base; cannel, coarse 9 in.; blackband ironstone with fish remains 5 in.; coal 1 in.; fireclay (clay breccia) 5 in.; coal 3 in.; fireclay 1 in.; coal 2 in.; coaly fireclay 1 in. on sandstone. South of Roslin both coal and ironstone are insignificant or absent. The fish remains in the Gilmerton Ironstone were described by Traquair (1903, p. 694).

The blaes with Lingula forming the roof of the Rough Parrot Coal is overlain by variable beds of shale, seatclay, mudstone and sandstone. At Loanhead and Moredun some of these beds are green, with thin clay and shale-breccia bands.

In the Middleton–Esperston area sphaerosiderite is common in the mudstones at about this horizon. These beds are succeeded by marine shales underlying the North Greens Limestone. The marine shales are up to 7 ft thick, but are thin or absent in the southern and eastern areas; they usually have calcareous bands and nodules near the top and are carbonaceous at the base.

North Greens Limestone to base of Vexhim Limestones

North Greens Limestone

The North Greens Limestone is the thickest limestone of the Lower Limestone Group, though only the lowest part is pure enough to be worked. From Niddrie to Roslin the bottom bed is fine-grained, compact, pale grey or brown with crinoidal and algal patches. A thin band of shale with goniatites has been found immediately above this bed in the Ramsay Pit and in the Bilston Glen Colliery No. 1 Shaft. Above this lies argillaceous limestone and calcareous shale up to 100 ft or more thick, overlain by a thick, often coarse sandstone, the North Greens Sandstone.

An exposure of limestone at Easter Duddingston (Mains) Farmhouse (Milne 1839, p. 341) is apparently the North Greens Limestone (Gibson and Bailey in Peach and others 1910, p. 177). The middle part was exposed in the railway cutting near Portobello. At Edgefield railway cutting 1.5 miles S. of Gilmerton the upper part of the limestone is exposed, the section being: sandstone; blaes, faky 5 ft on limestone, argillaceous and fossiliferous with calcareous shale 63 ft. Earlier records give 76 ft for the last item.

The basal bed has been quarried away on either side of Bilston Burn and is not well exposed. The site of an old quarry to the north of the burn was discovered at the commencement of the sinking of Bilston Glen Colliery No. 1 Shaft, where it was found that the bottom bed, 9 ft 6 in. thick, had been worked for nearly a quarter of a mile along the strike and to a depth where the overburden reached 25 ft.

The section of the North Greens Limestone and adjacent beds in Ramsay Pit 156-fm Crosscut Mine was: sandstone; shale 11 in.; limestone, argillaceous, and calcareous shale, fossiliferous 73 ft; blaes, crinoidal and shelly 2 ft; blaes with abundant goniatite fragments 6 in. shale, calcareous and crinoidal 1 ft; limestone, compact, pale grey and patchy crinoidal 6 ft; shale, calcareous with numerous Productids 2 ft; shale with calcareous ironstone nodules 4 ft 3 in.; shale, black, part parroty with fish remains 6 in. on fireclay, greenish, and mudstone.

In the Glencorse Burn the North Greens Limestone is cut out by a fault. The crinoidal limestone exposed there, originally considered to be the North Greens (Robertson and others 1949, p. 144) is now known to be the Gilmerton Limestone (Plate 2). Part of it is exposed in the Braidwood Burn, 100 yd upstream from its junction with the Cornton Burn.

There are good exposures in the River North Esk downstream from Peggy's Pool, from 250 to 550 yd S.W. of Newhall House. Roughly 50 ft thick, the lower 20 ft was quarried on either side of the river. It crops out again 200 yd upstream at the Mill bridge, being repeated by a fault, and here 25 ft are exposed.

On the east side of the large sandstone quarry at Whitfield Limeworks the base of the limestone is exposed, the section showing: limestone, light coloured, crinoidal (base of North Greens Limestone) 4 ft; limestone and limy blaes bands 1 ft 8 in.; limy blaes, dark, with a few shells 1 ft on coal, bright 2 in.

To the south it is exposed in the Bents and Bankhead quarries, a section in the former showing in downward order: limestone, thin bedded, shaly and crinoidal 3 ft; blaes, soft, dark 3 ft; limestone, light-grey, crinoidal 10 ft. Patches of Lithostrotion have been recorded in the limestone and also grains of glauconite.

Along the outcrop from Mount Lothian Quarry, by way of Fullerton and Upper Side quarries, Burn Quarry, Esperston to Middleton and Catcune Quarry the limestone shows distinctive characters which enable isolated outcrops to be identified. Details of individual sections are recorded on the six-inch maps; the characteristic sequence is as follows in downward succession:

The lower limestone is the portion worked and it seems probable that it is the equivalent of the basal beds of the west side of the Midlothian Basin.

Similar sections are seen in the old and new Middleton quarries. Working thicknesses in the Middleton Mines, where the stone is at present mined, range from 15 to 20 ft.

The North Greens Limestone is well exposed at Catcune Quarry. In the valley of the Tyne Water the lowest part of the limestone has been extensively quarried on either side of the river in the Currie Lee Quarries (Robertson and others 1949, p. 147). The section in the old quarry on the west bank of the river 450 yd W.S.W. of Currie Lee is: limestone, crinoidal with silty partings at base 15 ft 6 in.; limestone, impure, banded with calcareous shale 37 ft; shale, grey 2 ft 6 in. on limestone, grey crinoidal (worked) 12 ft. An interesting detail is the occurrence of macroscopic grains of glauconite, and algal patches in the upper part of the worked bed. The glauconite is also present at the same horizon in the Cousland Quarries and in the North Greens Limestone at Bents Quarry (Phemister in Muir and others 1956, p. 125).

At D'Arcy and Cousland the lowest bed of the North Greens Limestone has been both quarried and mined. There are numerous exposures of parts of the limestone but no complete section. In the Cousland No. 1 Bore (1953) a goniatite-bed was recorded in the shale just above the top of the basal crinoidal post of limestone, here 12 ft 10 in. thick (p. 22).

North Greens Sandstone

Directly overlying the North Greens Limestone or separated from it by rarely more than a few feet of shales is the North Greens Sandstone, best developed along the west side of the Midlothian Basin from Portobello to Bilston and across the basin to the Carberry district. It is a gritty and occasionally coarse sandstone. In a small quarry at Loanhead the friable, weathered stone was formerly won by shovel, and the harder part crushed, for sharp sand. It was exposed in the railway cutting at Portobello and again in Bilston Burn, being often stained red in these districts.

Above the North Greens Sandstone is the Under Vexhim Coal, a thin seam up to 2 ft thick but with clay partings, not known to have been worked. It is overlain by shales with ironstone bands and plant fragments.

The Niddrie (or Lower) Vexhim Coal is a persistent seam, even in the southern area. It was worked at Gilmerton, though the working thickness was recorded as no more than 18 in. In the old Gilmerton section (Gibson and Bailey in Peach and others 1910, p. 179) it was stated to be 3 ft thick. At Esperston it is only 9 to 10 in. thick where exposed in the North Middleton Burn.

Vexhim Limestones to Top Hosie Limestone

Vexhim Limestones

The Vexhim limestones are similar to one another and not easy to distinguish in isolated outcrops. The Lower Vexhim Limestone is usually the thicker and a coal is more frequently developed at its base. The two limestones are separated by measures which are mainly shales but which in places include a sandstone. They were laid bare in trenches near Niddrie House. In the Bilston Burn both limestones are well developed but the coals below each have been dug at the outcrop and now are no longer visible. Both limestones are crinoidal, brown weathering and have a dolomitic appearance.

In the Gilmerton Colliery Crosscut Mine the section of the Vexhim limestones reads: sandstone, faky, sheared at base, possibly faulted; Upper Vexhim Limestone 4 ft; fakes 1 ft 6 in.; Upper Vexhim Coal 9 in.; fireclay blaes 1 ft 6 in.; sandstone, rooty 4 ft; blaes 2 ft; fakes, sandy at top 14 ft; blaes, shelly, ironstone balls more common towards base 12 ft; Lower Vexhim Limestone 7 ft; blaes 9 in.; Niddrie Vexhim Coal, lower half bright, 1 ft 5 in. on fireclay.

At Ramsay Pit the Upper Vexhim Limestone is separated by 6 ft of blaes with ironstone plies from the overlying faky sandstone and is 6 ft 4 in. thick which suggests that the Gilmerton section is faulted.

The Vexhim limestones with their coals are again found in Glencorse Burn, about 350 yd upstream from Miltonbridge.

In the River North Esk at two points respectively 300 and 450 yd S.W. of Newhall House one of the Vexhim limestones is present, the following being the section in downward order: blaes, faky with sandy ribs; fakes, crinoidal with calcareous concretions 6 in. shale, calcareous and fossiliferous 1 ft 2 in.; limestone, impure, fine-grained and fossiliferous 4 ft. This limestone has been mapped as the Upper Vexhim Limestone but later comparison with local sections strongly suggests that it is the Lower Vexhim Limestone.

In the Esperston district both limestones crop out along the North Middleton Burn but are easily distinguished; the lower is 4 to 5 ft thick with the Niddrie Vexhim Coal at its base and contains corals and clumps of the tabulate coral Chaetetes; the upper, 1 to 2 ft thick, almost merges into the underlying sandstone as the Upper Vexhim Coal is absent.

Good exposures of the Lower Vexhim Limestone are seen high up on the east bank of the Tyne Water just south of Currie Lee Farm. Both limestones are found in the Vogrie Burn (Plate 2) a little farther north.

Measures between the Vexhim limestones and the Bilston Burn Limestone

The measures between the Vexhim limestones and the Bilston Burn Limestone consist mainly of sandstone, with a thin coal occasionally developed in the middle. In the Loanhead district a thin band of blaes also occurs near the top of the sandstone. A band of blaes at a similar horizon yielded marine fossils about 23 ft above the Upper Vexhim Limestone in Queen Mary's Mount Bore in the Cousland district (Plate 2). About 18 ft higher a foot of limy fakes with limestone bands and coaly debris was recorded.

Immediately beneath the Bilston Burn Limestone in both western and eastern areas of the Midlothian Basin a thick band of blaes occurs, with variable development of coal and coaly sediment near the base, associated with which near Loanhead are thin bands of ironstone and fish remains. In the Cousland district at this horizon up to 9 ft of parroty blaes or up to 5 ft of coal have been recorded. An analysis showed that the latter contained about 50 per cent of ash. This coal is remarkably similar to the Lillie's Shale Coal of Johnstone near Paisley (Clough and others 1925, p. 38), which has been compared with the coal underlying the Mid Kinniny Limestone (Figure 8) of West Fife (Haldane and Allan 1931, p. 25) and so probably is of considerable stratigraphical importance.

Bilston Burn Limestone

In thickness the Bilston Burn Limestone varies much more than the other limestones of the Lower Limestone Group.

In the type locality of Bilston Burn it consists of a main part of banded limestone 40 ft thick with thicker bands of better quality near the bottom, and an upper brown-weathering dolomitic bed 5 ft 3 in. thick, separated by 5 ft of calcareous shale from the main deposit. The base is not now exposed.

In Glencorse Burn farther south 34 ft of grey, rather argillaceous limestone are seen. At the head of Cornton Burn it crops out again but only 3 ft are exposed.

In the Carlops and Cousland districts it appears to have been partially eroded before the deposition of the overlying sandstone. In the Nine Mile Burn this sandstone rests directly on 5 ft 9 in. of ochreous-weathering limestone which overlies 3 ft of blaes.

The limestone is poorly exposed again in the faulted area 300 yd S.W. of Newhall House. Thence to Esperston there are no good exposures though old quarries occur along the outcrop.

At Esperston the limestone is still worked and the downward succession is: sandstone, laminated with ochreous weathering, plant remains and supposed algal markings (Spirophyton caudagalli Vanuxem); shale and sandstone ribs 4 ft; shale with occasional sandy ribs 6 ft; limestone, dolomitic, coarse at top, nodular 3 ft; limestone, fine-grained, blue-grey, in even bands with thin calcareous shale partings with marine shells, crinoidal at base of lowest worked post 17.5 ft. There may be a foot or so of limestone below this left as pavement.

Traces of quarrying are found along the outcrop from here to the Tyne Water, but no good exposures until the Vogrie Burn is reached (Plate 2). The limestone occurs in quarries at the south end of the D'Arcy–Cousland Anticline at Hillhead, where a thickness of at least 18 ft is seen, and again in the quarries about half a mile south of D'Arcy.

A variable thickness of shale overlies the Bilston Burn Limestone but the interval between this and the Top Hosie Limestone is mainly occupied by sandstone. In some districts, such as the northern end of the D'Arcy–Cousland Anticline, this sandstone is particularly thick and, as mentioned above, may rest directly on the limestone. Near the top of the sandstone a thin bright coal, not more than 12 in. thick is sometimes developed. It is separated from the Top Hosie Limestone by a thin sandstone or shale.

In an underground bore at the Lady Victoria Pit (Plate 2) Lingula was found in the roof-shales 1 ft 3 in. above the seam and lamellibranchs both immediately above and below the seam, which here is a cannel 11 in. thick.

Top Hosie Limestone

The highest bed of the Lower Limestone Group usually rests directly on the thick sandstone mentioned above. The top of the sandstone is calcareous and the base of the limestone sandy, the passage from one to the other being gradual. The limestone is crinoidal and overlain by blaes up to 6 in. thick, containing marine shells. It thins out as it is followed southwards and in most of the southern part of the Midlothian Basin is absent, so that it becomes a matter of great difficulty to define the base of the Limestone Coal Group (p. 27). Sometimes a thin band of shale with marine fossils persists at or very close to this horizon and is taken as the lowest bed of the Limestone Coal Group. Occasionally, however, even this is missing and sandstone extends up to the floor of the first of the coals of the Limestone Coal Group, the junction between the two groups presumably lying within it.

The Top Hosie Limestone was exposed in the Portobello railway cutting. A typical section is that in Bilston Burn, which in downward order is: blaes with marine shells (lowest bed of Limestone Coal Group); limestone, crinoidal, passing down into calcareous sandstone 2 ft 6 in.; sandstone, fine-grained 7 ft 6 in.; fakes 1 in.; coal, poor 8 in.; sandstone, rooty at top.

In the Nine Mile Burn the marine blaes rests on sandstone with a slightly calcareous top. In an old sandstone quarry 900 yd E.S.E. of Yorkston Farm, on the east side of Rosebery Reservoir, the sandstone weathers to an ochreous top with a mixture of plant fragments and marine shells. This is mapped as the horizon of the Top Hosie Limestone. The limestone is well exposed in the triangular inlier in the South Esk half-way between Temple and Anniston House. It is here a thin sandy limestone or calcareous sandstone with crinoid ossicles.

References

CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., WRIGHT, W. B., BAILEY, E. B., ANDERSON, E. M., and CARRUTHERS, R. G. 1925. The Geology of the Glasgow District. 2nd edit. Mem. Geol. Surv.

GOODLET, G. A. 1957. Lithological Variation in the Lower Limestone Group of the Midland Valley of Scotland. Bull. Geol. Surv. Gt. Brit., 12, 52–65.

HALDANE, D., and ALLAN, J. K. 1931. The Economic Geology of the Fife Coalfields. Area I. Dunfermline and West Fife. Mem. Geol. Surv.

HOWELL, H. H., and GEIKIE, A. 1861. The Geology of the Neighbourhood of Edinburgh. Mem. Geol. Surv.

MACGREGOR, M. LEE, G. W., and WILSON, G. V. 1920. The Iron Ores of Scotland. Mem. Geol. Surv., Min. Resources, 11.

MACGREGOR, M., and MACGREGOR, A. G. 1948. The Midland Valley of Scotland. 2nd edit. Revised. British Regional Geology, Geol. Surv.

MACGREGOR, M., and MANSON, W. 1935. Variations in the Thickness of the Carboniferous Limestone Series of Scotland, with Special Reference to the Limestone Coal Group. Trans. Inst. Mining Eng., 89, 115–30.

MILNE, D. 1839. On the Mid-Lothian and East-Lothian Coal-Fields. Trans. Roy. Soc. Edin., 14, 253–358. Published separately with additions 1839. Edinburgh.

MUIR, A., HARDIE, H. G. M. MITCHELL, R. L., and PHEMISTER, J. 1956. The Limestones of Scotland. M., Analyses and Petrography. Mem. Geol. Surv. Min. Resources, 37.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

RICHEY, J. E. 1937. Areas of Sedimentation of Lower Carboniferous Age in the Midland Valley, of Scotland. Sum. Prog. Geol. Surv. for 1935, pt. 2,93–110.

ROBERTSON, T. 1948. Rhythm in Sedimentation and its Interpretation: with particular Reference to the Carboniferous Sequence. Trans. Edin. Geol. Soc., 14, 141–75.

ROBERTSON, T., SIMPSON, J. B., and ANDERSON, J. G. C. 1949. The Limestones of Scotland. Mem. Geol. Surv., Min. Resources, 35.

TRAQUAIR, R. H. 1903. On the Distribution of Fossil Fish-remains in the Carboniferous Rocks of the Edinburgh District. Trans. Roy. Soc. Edin., 40, 687–707.

Chapter 4 Limestone Coal Group

General account

The base of the Limestone Coal Group is taken at the top of the Top Hosie Limestone, the summit at the base of the Index Limestone (Figure 2). Where the Top Hosie Limestone is absent the base of the group is taken at the equivalent marine horizon or its calculated level in the measures between the Bilston Burn Limestone and the North Coal or Arniston Parrot Coal (Plate HI; p. 25).

Lithological characters

The same rhythmic sequences of sediments prevail as in the Lower Limestone Group (p. 17) but whereas the most important economic unit, the coal, is frequently repeated, others, notably the marine sediments, are poorly developed.

The seams of coal are usually composite, containing varying proportions of bright coal (clarain), dull coal (durain and fusain) and cannel or parrot coal. The two commonly used mining terms are rough coal, a bright coal with subsidiary dull bands, which breaks easily into roughly cubical blocks, and splint coal which is a harder, mainly dull coal with subsidiary bright bands that usually breaks along the bedding planes. The terms parrot and cannel are used for fine homogeneous coal with a conchoidal fracture and little or no bedding; in mining records the terms are sometimes extended to include fine durain while both are sometimes referred to as gas coal on account of their good yield of gas when retorted.

Limy beds replacing coals in the Limestone Coal Group have been noted at several localities in Midlothian; in Fushiebridge No. 4 Bore, the Upper Mavis Coal, generally about 1 ft thick in other bores nearby, was represented by 6 in. of brownish argillaceous limestone with coal streaks, and a seam 12 ft 6 in. lower in the succession was much altered, and contained numerous thin ribs of carbonate. This type of alteration is analogous to that found in seams in the Productive Coal Measures (p. 96).

Sandstones are the most common sediments, with sandy shales (fakes) and shales (blaes) of secondary importance. The pavements of the coal seams are generally silty or sandy seatearths or sandstone; seatclays are not common

Seatearths are often loosely termed fireclays without reference to their refractory properties. Limestones are rarely developed. Clayband ironstones occur in the shales and seatearths as nodules or impersistent bands. Blackband ironstones (a close association of coal, usually cannel, and clayband ironstone) are less common but were of considerable economic importance during the last and in the early part of the present century (Macgregor and others 1920, pp. 164–95). The blackband ironstones are rather impersistent; they are typically found in association with a Lingula band.

Pyrites in the form of small irregular nodules or knots is most common in the marine shales and, where coals underlie them, the latter often have a thin coating on the cleat which shows iridescent colouring. Marcasite nodules are found near the base of thick sandstone beds.

Most of the shell beds apparently contain only the brachiopod Lingula and it has been customary to distinguish them by the name Lingula beds or bands, reserving the term marine for beds containing a richer fauna of brachiopods, lamellibranchs and other marine forms.

Outcrop

From Portobello to near Carlops the Limestone Coal Group crops out in a belt about a quarter of a mile wide. The dip to the south-east is steep and for this reason the continuity of the crop is but slightly interrupted by the dip-faults. The coals have been much worked along the northern part of this belt where, because of this steep inclination they received the name 'edge' coals and the group was originally called the Edge Coal Group. From Carlops the outcrop widens as it circles the southern rim of the Midlothian Basin but narrows again on entering the steeply dipping belt between Macbiehill and Howgate. Thence it swings eastwards in a semicircle with low northerly dips giving an outcrop nearly two miles wide as far as Gorebridge. There, under the influence of the D'Arcy–Cousland Anticline, which sets in northwards, the outcrop bifurcates, the eastern branch extending into East Lothian and the main western belt narrowing to form the eastern limb of the Midlothian Basin as it passes beneath the sea at Prestonpans. Along the last-named belt also the coals have been much wrought.

A great variation in thickness of the Limestone Coal Group is evident within the basin and is here recorded in the form of an isopachyte map (Figure 10). From the Loanhead area the thickness decreases both to south and east. This thinning is accompanied by the failure of the marine bands or the impoverishment of their faunas which makes correlation of the strata in the southern part of the area difficult. Consequently seam-names given in this district must be regarded as less certain than those in the main part of the coalfield north of the Vogrie Fault.

Correlation

A serious difficulty in correlation in the Midlothian Coalfield is the large number of local names used in different parts of the field. It has been one of the objects of the present survey to attempt a correlation of seams from area to area. To this end a standard set of names has been selected and synonyms indicated as far as possible (Figure 11) and (Plate 3).

Comparison of the stratigraphy of the Limestone Coal Group of Midlothian with that of Fife is shown in (Figure 9). The Kirkcaldy section, the nearest one to Midlothian, is largely compiled from that of Allan and Knox (1934, p. 132) with some additional information as mentioned below. Thus a Lingula band earlier recorded by Mr. Manson in the strata between the Kelty Main and Rough coals in Central Fife has recently been found in the Firth of Forth Tower No. 1 Bore by Ewing and Francis (in the press)who assign it to the roof of the Kelty Main Coal.

A study of the Midlothian and Fife successions reveals some broad similarities though, as might be expected for a separation of over ten miles, the detailed correlation is not certain. Thick coals occur in the range of strata which includes the Corbie and Stony coals of Midlothian and the Dunfermline Splint and Five Foot of Kirkcaldy. Between these thick coal groups and the Black Metals Marine Band there is a further point of similarity in the occurrence of a thick bed or beds of sandstone not only in parts of the Kirkcaldy district but also in Midlothian in such places as Burghlee, Mauricewood and Auchencorth (Plate 3). Where this arenaceous development is present the intervening coals are generally thin and sometimes absent.

Above the Black Metals Marine Band in Midlothian the Blackchapel Coal and Gillespie coals (the Siller Willie coals of the east side of the basin), forming a variable and often closely spaced group, are matched by a similar group in Fife which includes the Swallowdrum, Jersey and Kelty Main coals. Each group is in places succeeded by strata containing a Lingula bed.

The Rough Coal of Fife and Great Seam of Midlothian are each comparatively thick coals of medium quality developed over wide areas. In the strata above each a workable ironstone sometimes occurs. Comparison of the section of the Monkton House Bore with details of sections near Kirkcaldy shows similarity in development of the coals between these coal seams and the Index Limestone. In general the degree of correspondence between the Limestone Coal Groups of Kirkcaldy and Midlothian suggests that they belong to the same depositional basin.

Details

Top Hosie Limestone to base of Johnstone Shell-Bed

The interval between the Top Hosie Limestone and the Johnstone Shell-Bed varies from 105 ft at Gilmerton to 25 ft or less to the south of Auchencorth. The strata include three important coals, the North, the South and the Andrews. In some of the southern parts of the coalfield the seams split so that their identity is not always clear (p. 33).

In the railway cutting between Portobello East Junction and Niddrie North Junction (Wilson and others 1909) the North Coal lies 20 ft 6 in. above the Top Hosie Limestone, the details being: North Coal; clay shale 6 in.; sandstone 7 ft; blaes and ironstone balls with Lingula 13 ft; Top Hosie Limestone.

In Gilmerton Colliery, the Top Hosie Limestone is overlain by 4 ft 6 in. of shale, the lower part of which is shelly. The North Coal lies 9 ft 6 in. higher. To the southwest, in the Gilmerton Diamond Bore, 14 in. of shale rest on the limestone, the remainder of the 37 ft of measures up to the North Coal consisting of sandstone with a shale band in the middle.

The measures are similar at Loanhead and on the eastern side of the Midlothian Basin, the North Coal lying about 13 to 16 ft above the Top Hosie Limestone. The latter is generally overlain by shale with ironstone balls, succeeded by sandy shale and sandstone. Occasionally, however, in the Cowden area sandstone occupies the whole thickness between the Top Hosie Limestone and the North Coal. In the southern parts of the coalfield from 9 to 15 ft of strata separate these two beds, the limestone here being often absent and the shale occasionally missing.

North Coal (Blue of Duddingston; Blackband and Blue of Niddrie; includes Blue of Gilmerton; North and Little Splinty of Loanhead; Arniston Parrot; Parrot of Cowden; Hauchielin of Carberry and Wallyford)

The thickness of the North Coal at various localities is shown on (Plate 3). In the Portobello and Niddrie areas and in the Gilmerton Colliery, two coals are present in this position, the details being: Portobello railway cutting: coal, splint 8 in.; coal 1 ft; fireclay 1 ft 2 in.; sandstone 1 ft 8 in. on coal, splinty 2 ft 1 in. Niddrie Collieries: coal (Blackband Coal of Niddrie) 2 ft; strata 10 ft on coal (Blue Coal of Niddrie) 1 ft 10 in. Gilmerton Colliery: coal; parrot, impure 2 ft 6 in.; fireclay 3 ft; blaes, rooty with ironstone balls 5 ft 6 in.; sandstone 7 ft on coal (Blue Coal of Gilmerton) 2 ft.

Near Loanhead the coal lies up to 16 ft above the Top Hosie Limestone. It is typically in two leaves, the upper leaf formerly being termed the Cannel Fir or Little Splinty. At Ramsay Pit, Loanhead in the 156-fm Crosscut Mine the section is: blaes, sulphury and soft at base with fish scales; sandy fakes 3 in.; coal 1 ft 4 in.; fireclay and blaes 1 ft; coal, splint 2 ft; coal, rough 1 ft 2 in.; fireclay 4 in. on sandstone. The coal was worked extensively in the Loanhead–Roslin area and was reputed to vary from 2 ft 3 in. to 3 ft 10 in., which figures probably refer to the lower or main leaf only.

At Mauricewood the total thickness given was 2 ft 4 in. which probably included both leaves. The coal was worked only to a limited extent. At Cornton and Brunston it is 1 ft 8 in. to 2 ft thick and was worked a little at both places, at Cornton under the name Blue Coal (p. 33).

Elsewhere in the south it is 1 ft to 1 ft 5 in. and less, occasionally being absent altogether. A Lingula bed was found in the roof of the coal from Anniston to Cauldhall Moor but has not been recorded south and west of the latter place.

It attains a workable thickness again between Halkerston and Fushiebridge, where it is up to 2 ft 3 in. thick.

From Vogrie to Newtongrange where it is known as the Arniston Parrot, the coal was formerly worked extensively to a great depth for its band of parrot coal and near Rosewell the workings extended under the centre of the basin. The thickness of the seam varies from 1 ft 6 in. to 3 ft made up as follows: coal, jewel 5 to 20 in.; parrot 1 to 10 in.; coal, bottoms 5 to 14 in. on coal, wild 0 to 9 in. Up to a foot of seatclay sometimes intervenes between the coal and the underlying sandstone. The roof of the seam is finely laminated shale 2 to 3 in. thick with abundant Lingula, overlain by an ironstone rib known as the 'bane', which in places has yielded ostracods. Naiadites was recorded in the shale 6 to 8 in. above the ironstone in the Lady Victoria Pit. Between Vogrie and Southside the Arniston Parrot Coal was stated to be as much as 2 ft 3 in. thick, but in places it was thin or absent.

In a bore put down about 720 yd S.E. of Southside Farm the section of the seam was: coal 4 in.; blaes 1 in. on coal, parroty 1 ft. At Edgehead Colliery the coal is about 2 ft thick and in Cowden No. 124 Bore 3 ft of bright free coal, with splinty bands, occurred. The maximum recorded thickness in the Cowden–Crossgatehall area is 3 ft 8 in. Farther north in an underground bore in Carberry Colliery near the shafts the section in downward order was: coal 2 ft 4 in.; parting 4 in.; coal 1 ft 5 in.

Measures between the North and South coals

The thickness of the measures between the North and South coals varies from 88 ft in the north to 6 ft in the south of the coalfield. The North is succeeded by shale which near or at its base in all but the extreme south of the coalfield contains the Lingula band mentioned above.

A sandstone overlies the shale in a number of districts. In the north-western part of the coalfield these strata include a coal which is correlated with the Duddingston Rough Coal and which splits off from the base of the South Coal (Plate 3).

In the Duddingston district, the Rough Coal of Duddingston, 3 ft 9 in. thick, occurs 57 ft 9 in. above the North or Blue Coal and 30 ft below the South or Carlton Coal. In the Portobello railway cutting and in the Niddrie Crosscut Mine the intervals between the North and South coals are 40 ft and 30 ft respectively; in both localities the intervening strata include a coal 1 ft 8 in. thick and in the Niddrie Collieries a Lingula band was found in shales above the North Coal. In Gilmerton Colliery the North Coal and the South Coal are separated by 30 ft of strata with a coal 1 ft 5 in. thick near the top, the details of the lower part being: blaes, faky at the top with large septarian nodules 5 ft; ironstone with Lingula and fish remains 6 in. on North Coal. The North and South coals are separated by from 18 to 30 ft of strata between Loanhead and Newtongrange; south of here from 6 to 18 ft is the separation. A section of these strata in Rosebery No. 2/50 Bore showed: South Coal; faky fireclay 6 in.; sandstone 1 ft 2 in.; sandy fakes with fireclay and rooty fakes bands 6 ft 11 in.; dark fireclay with roots, ironstone balls at base 3 ft 3 in.; carbonaceous fakes with abundant large Lingula (like L. squamiformis Phillips) 2 in.; North Coal. On the eastern side of the basin, north of the Vogrie Fault, the North Coal is succeeded by shale with occasional ironstone bands and a Lingula bed at the base. Naiadites has been obtained above the Lingula bed at Newtongrange (p. 32). Sandy shale and sandstone underlie the South Coal.

In the Southside area the two coals are about 13 ft apart and in the Cowden–Crossgatehall vicinity 14 to 43 ft. In all these localities the North Coal is overlain by a thin bed of carbonaceous fakes or sandy shales, containing Lingula. Farther north in St. Clement's Wells No. 1 Bore, the interval was 9 ft 3 in., the details being: South Coal; fireclay, faky with black roots 3 in.; faky sandstone and sandy fakes 6 ft 6 in.; blaes, soft, grey with occasional irony balls and pyritized plant fragments 2 ft 4 in.; fakes, dark grey with abundant fragments of Lingula 2 in. on North Coal.

In an underground bore in Carberry Colliery, 420 yd N.E. of No. 3 Shaft, these measures totalled 42 ft and included about 20 ft of shaly sandstone and sandy shale, underlain by a white sandstone, coarse in the lower part, 10 ft thick.

South Coal (Carlton of Gilmerton; Wee of Southside; Wee or Little of Newtongrange)

At Duddingston the South Coal was 5 ft 6 in. thick and in the Portobello railway cutting 6 ft of good bright coal were seen. The section in the Niddrie Collieries was: coal, inferior 11 in.; fireclay 3 in. on coal 4 ft 5 in.; the details of the seam in Gilmerton Pit were similar. Between Loanhead and Roslin the South Coal varies from 4 ft to 2 ft 4 in. and has one or occasionally two thin partings. It is here separated from an underlying coal 1 ft to 1 ft 6 in. thick by 1 ft to 5 ft 6 in. of sandy shale, sandstone and seatclay. This underlying coal, which has in the past been known as the Little Coal at Loanhead, is believed to be the Duddingston Rough Coal. In Roslin Colliery it is so close to the South Coal that it is included under that name. Sections here are as follows: Ramsay Pit 156-fm Crosscut Mine: blaes, dark with ironstone bands and some plant fragments; coal with hard ribs 1 ft 2 in.; coal (lowest leaf of South) 2 ft 2 in.; fakes 3 ft; coal (?Duddingston Rough) 1 ft 6 in. on sandstone. Roslin Colliery No. 2 Mine: coaly blaes; coal, about 1 ft 3 in.; parting 3 in.; coal 2 ft 5 in.; faky fireclay 1 ft 2 in.; coal 1 ft 2 in. on fakes and sandstone, rooty.

In the following localities the term South Coal includes this extra leaf or Duddingston Rough Coal as at Roslin. At Mauricewood, where the coal was worked to a small extent, thicknesses of 2 ft 4 in. to 3 ft 4 in. were recorded. At Cornton and Brunston it is 1 ft 1 in. thick. A section in a mine at Cornton Colliery reads: blaes, hard, shelly with limy balls (? base of Johnstone Shell-Bed, Andrews Coal absent); fakes and faky blaes, striped 5 ft; blaes, grey, micaceous 1 ft; coal (South) 1 ft 1 in.; daugh, grey 1 in.; wild parrot 6.5 in.; fakes, dark, irony 4 in.; daugh, coaly 4 in.; kingle, hard grey 10 in.; coal (Blue or North) 1 ft 8.5 in.; fireclay, hard sandy 4 in. on sandstone.

In the southern part of the coalfield the seam is thin, often split by partings and occasionally absent altogether. In the Newtongrange district it may reach 4 ft in thickness but does not appear to have been worked, probably on account of thick and numerous dirt partings. Between Vogrie and Southside it ranges from 0 to 1 ft 4 in. or exceptionally reaches 3 ft 4 in. in two leaves. Farther north the seam often occurs in two leaves as in Vogrie Burn No. 45 Bore where the section was: coal 4 in.; blaes 1 in. on coal, parroty 1 ft. In the Cowden–Crossgatehall area a representative section is: coal, dirty 1 ft 9 in.; faky fireclay and fireclay 2 ft 6 in. on coal 1 ft 6 in. In the Carberry–Wallyford area the separation between the two leaves varies from 5 ft to 8 ft 6 in. In St. Clement's No. 1 Bore the details in downward succession were: coal 1 ft 3 in.; fireclay, faky with black roots 1 ft; coal 3 in.; fireclay and faky fireclay 2 ft 6 in.; sandstone, faky 4 ft; blaes, faky, with occasional irony patches 2 ft; coal 9 in.; fireclay, carbonaceous, rooty 3 in.; coal, parroty 1 ft.

Strata above the South Coal

The strata above the South Coalare characterized everywhere except in the Auchencorth district by evenly bedded, fine-grained dark shales with bands of clayband ironstone yielding very rarely fish scales and plant fragments. In Burghlee No. 1/54 Bore (Plate 3) a marine shell was obtained from a core stated to be 12 ft above the South Coal. As this is the only record of marine shells at this horizon it is possible that the core sample was misplaced. The shales are most commonly overlain by a sandstone. The thickness of the measures between the South and Andrews coals varies as follows: Portobello railway cutting 70 ft; Niddrie Crosscut Mine 76 ft; Gilmerton Colliery 29 ft; Gilmerton Diamond Bore 38 ft 10 in.; Loanhead to Newtongrange 18 to 48 ft; at the south end of the field it is in places less than 6 ft (p. 29). In the two first named the thickness includes a sandstone respectively 28 and 60 ft thick; from Portobello to Loanhead the bed of blaes above the Carlton or South Coal is 15 to 18 ft thick. Details of these strata in the Ramsay Pit 156-fm Crosscut Mine are as follows: Andrews Coal; fireclay 8 in.; sandstone, rooty at top with fakes at top and base 10 ft 3 in.; blaes 5 ft; clayband ironstone 4 in.; blaes, fine 5 ft 3 in.; clayband ironstone 4 in.; blaes with plant remains at base 6 ft 7 in.; South Coal. A characteristic section in the south-east part of the coalfield was seen on the right bank of the River South Esk 350 yd due west of Arniston House: Andrews Coal; shale, sandy at top 2 ft; sandstone, shaly in part with unconformable base 3 to 8 ft; shale, eroded at top 1 to 2 ft; shale with two thin ironstone bands and plant fragments 1 ft; South Coal. Along the eastern outcrop similar figures for the thickness of the measures between the two seams are: Southside about 21 ft; Cowden to Wallyford 17 to 26 ft.

Andrews Coal (Peacocktail of Gilmerton; Lower Diamond of Carberry)

The Andrews Coal, which lies at the base of the Johnstone Shell-Bed, is frequently pyritous and has often suffered from erosion before the deposition of the marine sediments which form its roof. In places its absence is probably due to this cause.

In the Portobello railway cutting the seam was only 7 in. thick and it was absent in the Niddrie Crosscut Mine, though in a crosscut at Gilmerton it was 4 ft thick, the top 2 ft 6 in. being partly splinty. The section recorded in the Gilmerton Diamond Bore was: coal 1 ft 5 in.; pyrites rib I in.; coal 5 in.; coal and blaes 5 in. on coal 8 in.

Near Loanhead it is in two leaves with a maximum thickness of 2 ft 10 in. The section of the Andrews Coal in the 156-fm Level Crosscut Mine at Ramsay Pit is: coal 1 ft 11 in.; fireclay, hard, dark 1 ft; coal 11 in.; fireclay 8 in. on sandstone and fakes. Working thicknesses ranged from 1 ft 9 in. to 2 ft 3 in. at Roslin but these may refer to the top leaf only. At Mauricewood it is 1 ft 6 in. Round the south end of the coalfield the seam is less than a foot thick and often absent. A section of the group of coals which probably includes the North, South and Andrews in the extreme south of the district was given by the Harbourcraig No. 6 Bore:

Near Vogrie and Southside the Andrews Coal is from 0 to 2 ft thick. In the Newtongrange area the lower leaf is parroty and occasionally is a true cannel; the top is usually pyritous and the thickness of the seam, excluding partings, is less than 2 ft. In the Lady Victoria Pit Shaft the seam with a blaes roof consisted of: coal 11 in.; blaes 3 in.; cannel 10 in. resting on blaes 2 in. on a sandstone post.

In the Cowden region a thickness of 10 in. to 2 ft 2 in. is mentioned. A small area of the coal was worked in Carberry Colliery the thickness being 1 ft 8 in. In this neighbourhood a tendency to split is revealed by the section in St. Clement's Wells No. 1 Bore where the downward sequence was : coal 1 ft 1 in.; parting 2 in.; coal 10 in.; parting 2 in.; coal 4 in.

Johnstone Shell-Bed to base of Corbie Coal Group

The strata between the Andrews and Corbie coals include the Johnstone Shell-Bed, the best developed marine band in the Limestone Coal Group. Whilst at Gilmerton Colliery these measures are 83 ft thick they are as thin as 30 ft in the south of the coalfield near Macbiehill.

Johnstone Shell-Bed

The Johnstone Shell-Bedoccurs typically as two beds of shale with marine fossils, termed the Lower and Upper Johnstone Shell-Bed respectively, separated by a sandstone of variable thickness. The top part of this sandstone and the base of the Upper Bed are often calcareous. In some districts much of the former is pale (perhaps leached) or bluish in appearance; it carries tourmaline and is very hard near Newton-grange where it was known as 'Waffle's Toe'. Each marine bed contains ironstone bands and nodules which in the eastern and southern districts are small and flat; the lower parts of the beds are the more fossiliferous. The lower bed, the lowest few inches of which are also sometimes calcareous, rests directly on the Andrews Coal or its seatearth. In the central and north-western parts of the coalfield additional fossiliferous horizons occur between the lower and upper beds and between the upper bed and the Corbie coals.

The strata separating all these Shelly bands may include, in addition to sandstones, some thin coals and seatearths. The Upper Johnstone Shell-Bed occasionally thins out locally, as near Edgelaw, but it is not clear whether this is due to non-deposition or subsequent erosion.

At Portobello railway cutting the Andrews Coal is overlain by 11 ft of blaes containing lamellibranchs, succeeded by sandstone and shale, while the details of the succession in a crosscut mine in Gilmerton Colliery in which only the lower bed was identified are as follows in downward sequence:

An unusual development of the Upper Johnstone Shell-Bed was encountered in Monkton House No. 37 Bore, where the downward succession was:

The two leaves of the Johnstone Shell-Bed are as much as 48 ft apart in the Loanhead area, but in the south they come closer together. At Auchencorth a limestone up to 2 ft thick, the Harlaw Limestone (Plate 3), occurs 3 to 4 ft above the Andrews Coal on the horizon of the Johnstone Shell-Bed.

In the Ramsay Pit 156-fm Crosscut Mine the following section was observed, which is remarkable in that it contains another band with marine fossils between the Upper and Lower Johnstone Shell-Beds:

Between Loanhead and Newtongrange some 36 to 40 ft of measures separate the Upper Johnstone Shell-Bed from the lowest Corbie coal. Above the blaes of the Upper Johnstone Shell-Bed there is a sandstone, occasionally over 50 ft thick, but usually much less. Here and in the southern parts of the coalfield a thin band of shale and sandy shale is almost invariably found in this sandstone from 4 to 8 ft below the Corbie coals; this band has yielded Lingula in the Lingerwood Pit and represents one of the shelly bands seen in the Monkton House Bore.

Details of the strata between the Andrews and Corbie coals recorded in Harlaw Muir No. 1 Bore, including the Harlaw Limestone were as follows: Corbie Craig Coal; -fireclay, faky 3 in.; sandstone with rootlets at top 6 ft 4 in.; fakes and sandstone, irony, rooty at base 2 ft 6 in.; sandstone 12 ft 6 in.; fakes, sandy with irony plies 4 ft 9 in.; blaes, faky with ironstone balls 4 ft 3 in.; blaes, faky with shells 6 ft 6 in.; limestone, grey, shelly (Harlaw) 2 ft; blaes, limy with shelly debris 1 ft 7 in. on Andrews Coal 8 in.

A typical development of the Johnstone Shell-Bed in the Temple district was found in Rosebery No. 2 Bore (1950), the strata between the Andrews and Corbie coals being: Corbie (Kailblades) Coal; sandstone, rooty, earthy at top 5 ft 3 in.; fakes, sandy with limonite balls and disturbed bedding, planty 2 ft 10 in.; sandstone, rooty, passing down into sandy fakes, planty 3 ft 7 in.; fakes, sandy with occasional flattened irony balls and pyritized plant fragments 3 ft 3 in.; blaes, faky with irony balls 3 ft; blaes, soft with marine shells 4 in.; sandstone, earthy with limy balls and shelly debris (base of Upper Johnstone Shell-Bed) 3 in.; sandstone, fine-grained with faky plies 11 ft; fakes, sandy striped with irony plies 3 ft 10 in.; blaes, faky with flattened irony balls and occasional shell fragments 8 ft 11 in.; ironstone and hard limy fakes with shell fragments (base of Lower Johnstone Shell-Bed) 6 in. on Andrews Coal.

In Dewarton No. 6/52 Bore the interval between the Andrews and Corbie coals was 60 ft, the succession in downward order being: Corbie coals; sandstone, rooty at top 6 ft 9 in.; sandstone, faky and fakes 3 ft 3 in.; sandstone, rooty in upper part 5 ft 9 in.; fakes and sandy fakes 6 ft; fakes with ironstone balls, passing down into faky blaes with ironstone balls and fragments of marine shells at the base 4 ft 9 in.; blaes, faky 1 ft; sandstone, fine-grained, bluish at top, 23 ft 3 in.; fakes, dark grey with small ironstone balls and pyritized plant remains, passing down into faky blaes and blaes with ironstone balls and fragments of marine shells 9 ft 3 in. on Andrews Coal.

In Fordel Mains No. 3 (Old) Bore the Andrews Coal was separated from the Corbie coals by about 72 ft of strata. Farther north in St. Clement's Wells No. 1 Bore the interval was 58 ft 8 in., made up as follows in downward succession:

Corbie Coal Group

Corbie coals (Corbie and Stony of Gilmerton; Corbie Splint, Corbie Rough or Craigie and Beattie of Loanhead; Corbie Splint and Corbie Jewel of Mauricewood; Little Splint and Kailblades of Newtongrange, Southside and Cowden; Lower Kailblades and Kailblades of Coldhame; Lower (No. 2) and Upper (No. 1) Diamond of Prestongrange; Upper Diamond of Carberry; Corbie Craig of south-west and south of coalfield; Kailblades of south-east of coalfield).—In the Loanhead area, where they are most fully developed, the Corbie coals consist of a group of three seams, distinct and separately workable, which are in upward succession the Corbie Splint, the Craigie and the Beattie. Elsewhere two of these coals (or even perhaps all three) come close together to form essentially one seam in leaves (Plate 3). It should be noted that the Stony Coal of Loanhead (Figure 9) and (Figure 11) is at a higher horizon than the seam of that name in the Corbie group.

As far as is known, in the vicinity of Duddingston and Niddrie the Beattie Coal is absent and over most of this area the Corbie group is represented by a single, unnamed seam equivalent to the Corbie Coal of Gilinerton Colliery (Plate 3). The section of this coal in Monkton House No. 37 Bore, is, in downward succession: coal 1 ft 10 in.; coal, cannel, poor in the upper part 1 ft 3 in. The interval between the Corbie Coal of Gilmerton Colliery and the Beattie Seam ranges from 36 ft 11 in. to 48 ft, and in a crosscut mine in Gilmerton Colliery the succession includes a sandstone 40 ft thick, which in places rests directly on the Corbie Coal. In Monkton House No. 37 Bore the Corbie Coal of Gilmerton was directly overlain by 12 ft 8 in. of shale which was slightly carbonaceous in the lower part and contained lamellibranchs in the upper part. Details of the Beattie (Stony of Gilmerton) Coal are given on (Plate 3).

The best development of the Corbie group is in the Loanhead and Roslin districts. The lowest or Corbie Splint Coal varies here from 2 ft 8 in. to 3 ft 6 in. and has been extensively worked; it was described as a superior splint coal. The roof measures are variable, consisting of shale and seatearth where the coal is close to the overlying seam, but including sandstone when separated by a large thickness of strata. The pavement also varies, a seatclay sometimes intervening between the coal and the underlying sandstone. The section in Ramsay Pit 156-fm Crosscut Mine showed in descending order: coal, splint with bright ribs 1 ft 10 in.; coal, bright, hard 5 in.; fireclay, part coaly 2.5 in.; coal with thin dark streaks 3 in.; coal, hard 5.5 in.; fakes, hard 6 in.; sandstone, giving a total thickness of 2 ft 11.5 in.

The Craigie or Corbie Rough Coal between Loanhead and Roslin lies from 1 to 40 ft above the Corbie Splint. It varies in thickness from 2 ft 2 in. to 4 ft 3 in. and has been extensively worked. The floor consists of sandy shale or seatclay; the roof of shale or sandy shale. A section in Ramsey Pit 156-fm Crosscut Mine gave the following section: blaes, soft at base with plant fragments; coal 4 ft 3 in.; ?soft fireclay 6 in. on sandstone.

Near Loanhead the Beattie Coal is separated by 3 to 16 ft of strata from the Craigie Coal and varies in thickness from 1 ft 6 in. to 3 ft 5 in. In the Roslin district the seam lies less than 3 ft above the Craigie and is from 9 in. to 1 ft 6 in. thick. It has a seatclay or sandy shale pavement and a roof of hard sandy shale, above which is shale with abundant Lingula and fish remains. A section of the Beattie Coal in the Ramsay Pit 156-fm Crosscut Mine showed: ironstone, nodular 3 in.; blaes, dark with abundant Lingula and fish remains 8 in.; fakes, hard 1 ft 3 in.; coal, hard, bright 2 ft 6 in. on fire-clay, strong 1 ft.

In the Mauricewood and Cornbank area the Corbie coals consist of two seams, the lower, the Corbie Splint, recorded as 2 ft 6 in. thick. The Craigie and Beattie seams of Loanhead have apparently come together at Mauricewood to form the upper coal, worked there under the name of Corbie Jewel with a thickness of 3 ft 11 in. to 4 ft 2 in. It is, however, possible that the 13-in. coal a little higher in the Mauricewood section (Plate 3) is the Beattie Coal.

In the rest of the southern area the Corbie coals form one coal with a parting. Between Comton and Auchencorth the combined thickness ranges from 3 ft to 4 ft 6 in., with a parting varying from 8 in. to 1 ft 6 in. and the seam is named the Corbie Craig. A section of the coal in the Cornton Mine was: sandstone, irregular base (resting directly on the coal in the eastern part of the workings); fakes and blaes with ironstone rib and Lingula near base 6 ft; coal, banded bright and dull 1 ft 10 in.; coal, dull, very hard 1 in.; coal, banded mostly bright with some pyrites 10in.; fireclay, faky, thickening eastwards 1 to 4 ft; coal, splint 10 in.; coal, rough, bright 11 in. on sandstone, dark grey with roots. Farther south towards Macbiehill the seam is in places less than 2 ft thick; in some cases this appears to be due to erosion of the upper leaf.

In the south-eastern portion of the field between Lilyburn and Halkerston the coals also come together as one seam with two leaves, known as the Kadblades. Here the parting is 2 to 3 ft in thickness; occasionally, as near Rosebery, it reaches 11 ft. The lower leaf, presumably the equivalent of the Corbie Splint, normally varies from 1 ft 3 in. to 1 ft 8 in., though in places, where separated from the upper by a large interval, it is as little as 4 in. thick. The upper leaf ranges from 1 ft 6 in. to 2 ft 9 in. and is usually the thicker of the two. In this area Lingula is scarce in the roof blaes, which is a characteristic greenish grey colour due to pyritization and often carries pyritized plant fragments. In some localities the overlying sandstone rests directly on the coal. The coal has been much worked opencast hereabouts; the parting is rather large for underground mining.

A typical section is exposed on the cliff forming the north bank of the River South Esk opposite Temple church. Here 6 in. of micaceous shale overlain by sandstone forms the roof of the coal, the upper leaf of which is 2 ft thick. This is separated by 2 ft 6 in. of sandy micaceous shale with roots from the lower leaf 1 ft 3 in. thick which rests on sandstone.

On the eastern side of the main coalfield the Corbie Splint Coal, from 2 ft to 2 ft 10 in. thick, is known as the Little Splint but has been little worked. The Craigie and Beattie are close together with a parting which is usually from 1 to 7 in. thick, but occasionally as much as 3 ft, the combined coal being known as the Kailblades. In parts of the Newtongrange district these two coals have been named the Kailblades Bottom and Top coals. Excluding partings the thickness of these two combined coals between Newtongrange and Arniston varies from 2 ft 11 in. to 6 ft 2 in. Near the Lady Victoria Pit Shaft the Kailblades Bottom Coal itself splits into two so that the Kailblades Coal hereabouts appears in three leaves.

A typical section of the Kailblades was recorded in the Whitehill or Peacocks Mine of the Lady Victoria Pit: blaes, faky; top coal 1 ft 4 in.; coal, soft 5 in.; daugh 2.5 in.; bottom coal 3 ft. Blaes, 1 ft 9.5 in. thick, occurs below the bottom coal and in turn rests on 12 ft of sandstone forming the roof of the Little Splint Coal, here 2 ft 1 in. thick.

At Vogrie, however, the Corbie Splint from 1 ft 5 in. to 2 ft thick was close to and usually worked with the Corbie Rough and Beattie coals, the combined thicknesses of these two ranging from 2 ft 6 in. to 3 ft 9 in. All three together were here known as the Kailblades Coal, a typical section in Vogrie Colliery in No. 3 (Old) Pit being: sandstone; coal 1 ft 10 in.; parting 2 in.; coal 2 ft; faky fireclay 1 ft 6 in. on coal 1 ft 11 in. Between Vogrie and Southside the combined thickness of the Corbie coals reaches 4 ft.

In the Southside area the group is frequently represented by three seams close together, as in Dewarton No. 6/52 Bore, where the succession was: coal 1 ft 11 in.; fireclay 2 ft 7 in.; coaly fakes 2 in.; coal 10 in.; coaly fireclay 9 in.; sandstone 9 in. on coal 1 ft 9 in. In some bores, however, as Southside No. 601, the lowest coal, the Little Splint, has split from the two upper seams.

North of the D'Arcy Anticline, in the vicinity of Cowden and Crossgatehall, the interval between the Little Splint and Kailblades coals ranges from 8 ft 6 in. to 17 ft 11 in. The former seam usually occurs in leaves, as in Fordel Mains Colliery No. 3 Bore where the section in downward order was: coal 1 ft 7 in.; fakes and fireclay 1 ft 9 in.; hard rib 7 in.; coal 2 ft 4 in. The details of the Kailblades Coal in the same bore were: coal 1 ft 9 in.; coal, soft 2 in. on coal 1 ft 1 in.

In the Carberry area the Corbie group of coals includes two seams, which in Carberry No. 4 Bore were separated by 47 ft 9 in. of strata, including a sandstone, medium-to coarse-grained, 21 ft 6 in. thick. The Corbie Splint and Craigie coals of Loanhead are represented by the lower of these two seams, the Upper Diamond of Carberry, which often occurs in two leaves. In a bore in Carberry No. 1 Pit the Upper Diamond Coal was: coal 1 ft 5 in.; hard band 3 in. on coal 2 ft 9 in. The Beattie Coal, 11 in. thick, lay 48 ft higher in the succession.

The representatives of the Corbie coals in the Prestongrange district are the No. 1 Diamond, which is the upper seam, and the No. 2 Diamond Coal. Both seams occur in two leaves in the workings of Prestongrange Colliery, the following being representative sections: No. 1 Diamond: coal 2 ft; parting 1 ft 4 in. on coal 9 in.; No. 2 Diamond: coal 2 ft; parting 3 in. on coal 3 in.

The interval between the seams ranges from 3 ft to 5 ft 3 in. In Prestonlinks No. 36 Underground Bore the No. 1 Diamond was overlain by 1 ft 2 in. of carbonaceous fakes and blaes, with Lingula.

Corbie Coal Group to base of Black Metals Marine Band

The measures between the Corbie coals and the Black Metals Marine Band include five named coals, three of which are important, and one named ironstone. In ascending order these seams are: Hopes Coal (Plate 3), Stony Coal, Bryans Coal, Loanhead No. 1 Ironstone, Glass Coal and Ball Coal. The thickness of this group of strata varies in the northern and central part of the field from 120 to 300 ft. In the south it diminishes to about 70 ft, the coal seams thinning also and in places completely disappearing, especially where the full thickness is represented by a thick sandstone known as the Kittleyknowe Sandstone.

At Duddingston 150 ft of measures separate the Corbie and Stony coals and the corresponding thickness was 134 ft in the Niddrie Crosscut Mine. In the mine, the Beattie Coal, the upper seam of the Corbie group, is absent and the seam representing the Corbie Splint and Craigie coals is directly overlain by a sandstone 40 ft thick, succeeded by 8 ft of blaes, followed by a sandstone 66 ft thick. South of Niddrie the thickness of the strata between the Beattie Coal and the Stony Coal ranges from 47 ft 5 in. in Monkton House No. 37 Bore to about 24 ft in Gilmerton Colliery. Both in the bore and in the colliery Lingula has been found in the beds overlying the Beattie Coal. The details of the succession immediately above the coal in the Monkton House Bole were in downward order: fakes, planty, dark grey 1 ft; blaes, faky, dark with fragments of Lingula at the base 1 ft; clayband ironstone, brown 2 in.; blaes, dark with Lingula and fish remains 8 in.; fakes, dark irony 4 in.; Beattie Coal.

Hopes Coal

TheHopes Coal has not been recognized north of Loanhead. Between Loanhead and Newbattle the Hopes Coal lies from 9 to 24 ft above the topmost Corbie Coal and from 6 to 22 ft below the Stony Coal, its thickness varying from 1 ft 3 in. to 2 ft. It is reported to have been worked to a small extent for its cannel, at Loanhead.

The section of the seam in Ramsay Pit 156-fm Crosscut Mine reads: fakes and blaes; blaes, parroty 3 in.; cannel, glossy 1 ft 1 in.; blackband ironstone 3 in.; coal, bright 6 in. on fakes and sandstone. The blackband ironstone contains fish remains and fragments of Naiadites.

In the southern part of the field the Hopes Coal is separated from the Stony Coal by strata less than two feet thick (p. 41). The thickness varies from 6 in. to 1 ft and it lies from 8 to 15 ft above the Corbie coals. In the Southside area it has been referred to in opencast mining as the lower leaf of the Alecks Coal.

From Vogrie to Southside it is up to 1 ft 3 in. thick. Between 18 and 36 ft of measures lie between the Hopes and Stony coals in the central belt of the coalfield, much of the variation being due to an irregular sandstone.

In Southside No. 978 Bore the interval between the Beattie and Stony coals was 34 ft, including a pale brownish grey sandstone about 19 ft thick. A coal, 1 ft 7 in. thick, which probably represents the Hopes Coal of Loanhead, lay 7 ft 10 in. below the Stony Coal. Over most of the Southside area the Kailblades Coal is generally overlain by a thin bed of carbonaceous blaes or fakes, which often contains pyritized plants and occasionally carries Lingula.

In the Cowden–Crossgatehall region the interval ranges from 18 ft to 26 ft and is occupied mainly by sandstone. A coal 1 ft to 1 ft 9 in. thick generally occurs a few feet below the Stony Coal.

Farther north in the Carberry No. 4 Bore, the interval was 34 ft 11 in. including in the lower part 16 ft 6 in. of grey, medium to coarse-grained sandstone. The Beattie Coal was directly succeeded by 3 in. of dark sandy fakes overlain by 2 in. of grey fakes with Lingula and fish fragments.

In the vicinity of the shaft of Prestongrange Colliery the distance between the Upper (No. 1) Diamond Coal and the Stony Coal was about 6 ft (Plate 3), but in the workings farther north the interval had increased to 20 ft.

Stony Coal (Corbie of Duddingston and Niddrie; Parrot Rough of Gilmerton; Alecks of Newtongrange, Southside and Cowden; Beggar of Carberry and Prestongrange; Stoney; Alex)

Therange in thickness of the Stony Coal is shown on (Plate 3). The section in the Niddrie Crosscut Mine was: coal 2 ft 6 in.; blaes 1 ft 5 in. on coal 1 ft 5 in. and in Monkton House No. 37 Bore: coal, with a 2-in. fireclay band in the centre 2 ft; fireclay 5 in. on coal 5 in. In a crosscut mine in Gilmerton Colliery the seam was 3 ft 10 in. thick, the bottom 14 in. being parrot coal.

At Loanhead the Stony Coal, as its name implies, is frequently split by dirt partings. It has been wrought to a limited extent, the lower of its two leaves being up to 4 ft 2 in. thick, excluding thin partings. The records of working thickness vary from 3 ft to 3 ft 4 in. and at Roslin from 1 ft 11 in. to 2 ft 6 in. The pavement consists of seatclay or less frequently of sandy fakes or sandstone. The upper leaf is typically a cannel 1 ft 2 in. to 1 ft 4 in. thick, separated from the lower by up to 1 ft 6 in. of shale and ironstone in which fish remains have been found.

A section in the Ramsay Pit 156-fm Crosscut Mine was: blaes with ironstone ribs; blaes, parroty 5 in.; coal, cannel, coarse 1 ft 4 in.; ironstone, dark 3 in.; blaes, faky with ironstone balls 1 ft 1 in.; coal with dirt ribs 1 ft 4 in.; coal 1 ft; hard parting 6 in.; coal 1 ft 5 in. on fireclay with coal ribs 1 ft.

At Mauricewood a coal was worked to a small extent under the name Stony. It is not known whether this corresponds to the 2 ft 2 in. coal recorded in the mine section (Plate 3) which has been tentatively correlated with the Stony, but which may in fact be the Bryans Coal.

In the Auchencorth district the coal reaches a thickness of 1 ft 9 in. but is frequently absent. Both Hopes and Stony coals occur close together between Lilyburn and Fushiebridge forming a pair very like the Kailblades and Little Splint. They are well exposed in a cliff section on the north bank of the River South Esk opposite Temple church. This shows sandstone resting on the Stony (or Alecks) Coal which consists of a foot of dull and bright coal above 6 in. of bright coal separated from 3 in. of bright coal below by 3 in. of fakes. The Stony Coal lies 3 ft above the Hopes Coal which is a mainly bright seam 8 in. thick, the intervening strata being rooty fakes with a sandstone band. In the Vogrie–Newtongrange district the Stony Coal measures from 2 ft 3 in. to 3 ft 3 in., but it does not appear to have been worked.

Between Vogrie and Southside the Stony Coal is from 6 in. to 2 ft 9 in. thick. In Southside No. 978 Bore the section was: coal, soft 5 in.; fireclay, coaly 6 in. on coal, mainly bright 1 ft 2 in. In the Cowden–Crossgatehall region the thickness ranges from 2 ft 3 in. to 2 ft 10 in. and farther north in St. Clement's Wells No. 1 Bore the seam was found to occur in three leaves: coal 2 in.; ironstone 5 in.; fakes, dark 2 in.; coal 6 in.; fakes, dark 5 in. on coal 5 in. In the workings of Prestongrange Colliery the thickness is about 2 ft 6 in.; but to the north in Prestongrange No. 36 Underground Bore the seam was represented by only 1 in. of coal.

The measures between the Stony and Bryans coals

The measures between the Stony and Bryans coalsare 60 ft thick at Duddingston, 33 ft 6 in. in Portobello railway cutting and 69 ft at Monkton House No. 37 Bore, at the last named of which they include a fine to coarse-grained sandstone 38 ft thick. Near Loanhead the corresponding measures are about 55 ft thick but decrease to 7 ft at the south end of the basin. The details of these strata in the Ramsay Pit 156-fm Crosscut Mine were: Browns Coal; fakes and faky fireclay 5 ft 10 in.; coal 9 in.; faky fireclay 1 ft 9 in.; sandstone, rooty top, faky at base 16 ft 10 in.; fakes 6 ft 6 in.; coal 1 ft; fireclay and fakes 1 ft 5 in.; blaes with ironstone, Lingula and fish remains 2 ft 8 in.; cannel and brown ironstone 7 in.; parroty blaes 7 in.; cannel and brown ironstone 10.5 in.; fakes rooty and faky blaes 5 ft 3.5 in.; blaes with ironstone ribs parroty at base 7 ft 9 in.; cannel (upper leaf of Stony Coal). The Lingula band has not been found in the southern part of the coalfield.

On the eastern outcrop the Stony and Bryans coals are 47 ft 9 in. apart at Southside No. 978 Bore, about 52 ft in the Cowden area and 27 ft 1 in. in St. Clement's Wells No. 1 Bore, at which place the Stony was overlain by 4 ft 7 in. of blaes, parroty at the bottom, with fish remains. Near Prestongrange Colliery the interval is from 29 to 35 ft and traces of shells were found in a bed of faky blaes 3 ft 6 in. thick about 18 ft below the Bryans Coal at Prestonlinks No. 36 Underground Bore.

Bryans Coal (Peacocktail or Big Splint of Duddingston and Niddrie; Browns of Loanhead; Splint of Vogrie; Bryans Splint of Southside and Cowden; Five Foot of Carberry and Wallyford; Jewel of Prestongrange)

The range of thickness of the Bryans Coal is shown on (Plate 3). In the Portobello railway cutting it consists of 3 ft of splint coal. In a crosscut mine at Gilmerton Colliery it is represented by no more than 4 in. of dirty coal. The working thickness in the Loanhead area was 2 ft 4 in. to 4 ft 3 in. but it has only been worked to a small extent. A section in the Ramsay Pit 156-fm Crosscut Mine gave: sandstone; coal 2 ft 4 in.; dirt 7.5 in.; coal 1 ft 7 in. on fakes or faky fireclay. The coal deteriorates locally in the Burghlee Pit where recent underground borings have proved the presence of a thick sandstone accompanied by thinning of the coal. This deterioration is probably connected with the development of partings in the seam encountered in the western workings of the Lady Victoria Pit.

Unless the 2 ft 2 in. coal taken as the Stony at Mauricewood is in fact the Bryans, the latter seam appears to be absent within the Penicuik Syncline. To the south-east, however, the coal reappears near Cauldhall Moor with a thickness ranging from 2 ft to 4 ft 5 in. between there and Fushiebridge though occasionally subject to washouts. It was the principal coal worked opencast at Temple. A measured section on the north bank of Redside Burn was as follows: sandstone, coarse; fakes, coaly with sandy rib 3 in.; coal, splint 1 ft 7 in.; fakes 1 in.; coal, bright 1 ft 2 in.; fireclay 0.5 in.; coal, bright 10 in. on sandstone, rooty at top.

Near Newtongrange the coal has been much exploited, working thicknesses ranging from 3 ft 4 in. to 5 ft 6 in. The included dirt partings were found to thicken towards the centre of the basin and there are occasional washouts. In the Vogrie–Southside area the corresponding thicknesses are 11 in. to 5 ft.

The section of the Bryans Coal in Southside No. 978 Bore was: coal, banded bright and dull 4 ft; fireclay 7 in. on coal, banded bright and dull 1 ft 4 in. In the Southside area the seam thins in an easterly direction; in Vogrie Burn No. 30 Bore the sequence recorded was: coal 7 in.; fireclay 5 in. on coal 2 ft 5 in. By contrast, in the Dewarton No. 6/52 Bore the thickness was reduced to 9 in. Cowden Mines showed 4 in. of cannel coal resting on 3 ft 9 in. of coal with three dirt bands.

In the Carberry–Wallyford region the top part of the seam is a parrot coal, as shown by a section at Carberry Colliery: coal, parrot 6 in.; stone 4 in. on coal 3 ft 9 in. The same feature appeared at St. Clement's No. 8 Bore where the top 3 in. of a 3 ft 6 in. seam consisted of parrot coal; and again at Wallyford Colliery where the section was: coal, parrot 7 in.; stone 2 in. on coal 3 ft 6 in.

In the workings at Prestongrange Colliery the thickness ranged from 3 ft 5 in. to 3 ft 10 in. and the section in the Prestonlinks Underground Bore was: coal 1 ft; coaly fireclay 1 ft 8 in.; sandstone 9 in. on coal, soft 2 ft 3 in.

Strata between the Bryans and Glass coals

A characteristic feature of the strata between the Bryans and Glass coals is the occurrence, in the central or upper part, of a bed of blaes or faky blaes containing Lingula. This lies closely above the horizon of the Loanhead No. 1 Ironstone and is found everywhere except in the southern part of the coalfield.

The Bryans and Glass coals are separated by about 60 ft of strata at Duddingston and 45 ft 9 in. in the Portobello railway cutting.

In the Monkton House Bore, the section, comprising 40 ft 9 in. of beds, was as follows:

In the Loanhead area the Loanhead No. 1 Ironstone, lying from 7.5 to 15 ft above the Bryans Coal and about 27 ft below the Glass Coal, was formerly much wrought (Robertson in Macgregor and others 1920, p. 174). At its thickest it attains 4 ft, deterioration setting in eastwards at depth. The Lingula and fish-bed in the roof-shales of the ironstone was recorded by Traquair (1903, p. 695). A section in the crosscut mine at the 156-fm level in Ramsay Pit reads: blaes with Lingula; blackband ironstone 1 ft 3 in.; blaes 9 in.; brown ironstone 1 ft 7 in.; cannel, coarse 4 in.; cannel, irony 8 in.; brown ironstone 2 in. on fakes. Working thicknesses were usually less than this; thus in one part part of the Burghlee Pit two bands of ironstone, each S in. thick, were separated by a 1-ft parrot.

In the south of the Midlothian Basin, where as little as 15 ft of strata separate the Bryans and Glass coals, both ironstone and Lingula bed are absent. Nevertheless in places a thin band of shale with fish remains may represent the horizon of the Lingula bed as for instance in Rosebery No. 8 Bore, where it occurs 7 ft above the Bryans Coal. The distance between the Bryans and Glass seams in Southside No. 978 Bore was 31 ft 5 in., the details being:

Farther east, in Vogrie Burn No. 30 Bore the Lingula bed was represented by 3 in. of carbonaceous faky blaes containing fish remains and ostracods, in addition to Lingula. An unusual development was noted in Dewarton No. 6/52 Bore, in which a thin rib of blaes with pale brown irony patches, lying 12 ft above the 9-in. coal taken as the Bryans Coal, was found to contain ostracods and fragments of mussels. Bores in East Lothian indicate that, in certain localities, where the mussel bed is well developed, the Bryans Coal is usually poor or absent.

In the workings in Cowden Mines the interval between Bryans and Glass coals was 26 ft 11 in. and the characteristic Lingula bed was found about 12 ft above the Bryans Coal. The details of the strata in St. Clement's Wells No. 1 Bore were in downward sequence:

In Prestonlinks No. 36 Underground Bore these measures were just over 23 ft thick, the Lingula bed lying 10 ft above Bryans Coal.

Glass Coal (Little Splint of Duddingston and Niddrie; Smithy of Newtongrange, Southside and Cowden)

The thickness of the seam at various localities is shown on (Plate 3). In the Monkton House Bore 2 ft 4 in. of bright, soft coal were found and in the crosscut mine in Niddrie Colliery 3 ft 3 in. of good coal.

In the Loanhead district the seam lies about 27 ft above the Loanhead No. 1 Ironstone and varies from 2 ft 3 in. to 4 ft 3 in. in thickness. It was described as a hard, rough coal ribbed with splint of good quality and has been worked extensively. The roof is sandstone or shale, the pavement seatclay, sandy shale or sandstone. The section measured in Ramsay Pit 156-fm Crosscut Mine was: blaes with ironstone balls; coal 3 ft 8 in. on fireclay.

The coal is usually absent at the south end of the field, though it reappears in the south-east as a thin coal up to 6 in. thick. Between Vogrie and Southside it increases to 1 ft 6 in. while towards Newtongrange it varies from 1 ft 7 in. to 2 ft 6 in. though it has only been worked, and that to a limited extent, at Lingerwood. A thickness of 2 ft 9 in. was recorded at Cowden Colliery, but the seam thins to the north and was only 6 in. thick in Prestonlinks No. 36 Underground Bore.

The measures between the Glass and Ball coals

The measures between the Glass and Ball coalsare 30 ft thick near Duddingston, 18 ft to 26 ft 8 in. in the Niddrie–Gilmerton area and from 5 to 55 ft in the Loanhead–Roslin district. The greater thicknesses result from the presence of a sandstone and there is sometimes a coal up to 2 ft, of inferior quality and split by seatclay, 5 to 10 ft above the Glass Coal. The floor of the Ball Coal is a seatclay with ironstone nodules.

Details of these strata in the Ramsay Pit 275-fm Crosscut Mine are: Ball Coal; fireclay with scattered ironstone nodules 7 ft; faky blaes, rooty and with ironstone balls at top 12 ft 6 in.; sandstone 14 ft 6 in.; blaes, faky and rooty at base 1 ft 7 in.; coal 3 in.; fireclay 10 in.; coal 6 in.; fireclay 3 in.; coal 1 ft 3 in.; faky fireclay 10 in.; sandstone with faky bands 4 ft 9 in.; blaes with ironstone nodules 1 ft 2 in.; Glass Coal.

Near Southside from 10 to 21 ft of seatclay, sandy shale and sandstone with occasional thin seams of coal separate the Glass and Ball coals, but the parting is variable. Thus at Cowden Mines the two coals were within 3 ft 6 in. of each other, but farther north at Carberry a coarse to medium-grained sandstone from 13 to 40 ft thick intervenes. In the Prestonlinks Underground Bore the interval was 9 ft 3 in. and the Glass Coal was immediately overlain by 9 in. of hard grey fakes with occasional fish scales.

In the southern part of the coalfield a thick sandstone, the Kittleyknowe Sandstone (p. 39), takes up most of the space between the Corbie Coals and the Black Metals Marine Band. The sandstone is separated from the Corbie Craig Coal by shales with small mussels, mostly preserved in ironstone, recently determined as Naiadites tumidus (R. Etheridge jun.). A representative section was obtained near Kittleyknowe in Lonelybield No. 1 Bore as follows: fireclay and sandy fireclay (below Ball Coal) 3 ft; sandstone, fine to medium-grained at top, coarse in the middle and at base 80 ft 6 in.; blaes and fakes, planty 7 ft 6 in.; fakes and faky blaes with irony plies and balls with N. tumidus towards base 14 ft 9 in.; fakes and faky blaes with ironstone band and numerous plant fragments 5 ft on Corbie Craig Coal. Exposures of these shales and the mussel band occur nearby in the Carlops Burn between its junction with the River North Esk and Kittley Bridge.

Ball Coal (Stinkie of Duddingston, Niddrie and Gilmerton; Beefie or Rough of Loanhead; Hard Splint of Cowden)

The Ball Coal immediately underlies the Black Metals Marine Band and like the Andrews Coal is sometimes pyritous; in places it has been removed by erosion.

The section of the Ball Coal recorded in Monkton House No. 37 Bore was: coal, bright 5 in. on coal, bright with plies of fusain 1 ft 7 in. In a crosscut mine in Gilmerton Colliery the seam was found to consist of 3 ft to 3 ft 3 in. of good coal.

Between Loanhead and Roslin the coal varies from 1 ft 5 in. to 3 ft thinning to the south with a soft shale roof and pavement of soft seatclay, characters which render the coal unworkable. An attempt was made at Ramsay Pit, where the section encountered at the 156-fm level was: blaes, soft, sulphury-weathering with marine shells; coal with dirt plies 2 in.; coal, hard splint, banded 1 ft; coal, hard, bright, banded 1 ft 2 in.; fireclay 2 in.; coal 8 in. on fireclay, making a total coal thickness of 3 ft.

At Mauricewood the 1 ft 9 in. coal overlying the thick sandstone is probably the Ball Coal though originally identified by Grant Wilson (in Peach and others 1910, p. 211) as the Blackchapel. Elsewhere in the south it is of little importance being often absent but occasionally reaching 1 ft 9 in.

Between Vogrie and Newtongrange it is only 1 ft 4 in. to 2 ft thick and has not been worked; from Vogrie to Southside it sometimes reaches 2 ft 2 in. but is absent in places.

In Cowden Mines the section was: coal, soft 1 ft 6 in.; parting 3 in .; coal, dirty 8 in.; parting 2 in. on coal, dirty 1 ft 9 in., while at Prestonlinks No. 36 Underground Bore the details in downward sequence were: coal 1 ft 5 in.; sandy fireclay 2 in.; coal 3 in.; coaly fireclay 5 in.; coal 6 in.

Black Metals Marine Band to base of Gillespie Coal Group

Black Metals Marine Band

Themeasures between the Ball Coal and the Gillespie Group of coals include a marine band, here called the Black Metals Marine Band, which is the most important fossiliferous horizon in the Limestone Coal Group, lying as it does near the middle of the group. Though its importance was not immediately recognized, it was first recorded at the beginning of the century in the Lady Victoria Pit (Clough in Peach and others 1910, p. 221). Recently it has been traced throughout the Midlothian and East Lothian coalfields (Macgregor 1937, p. 69; 1938, p. 62). It consists of up to 30 ft of dark, often silty or sandy shale with clayband ironstone nodules and bands with marine fossils, immediately overlying the Ball Coal. In some parts of the central and eastern districts it is found in two bands which, as in the case of the Johnstone Shell-Bed, are separated by a sandstone. The most common fossil is Lingula, the abundance of this genus distinguishing it from the Johnstone Shell-Bed. Other fossils include brachiopods, particularly Productids, and lamellibranchs, but in the southern area these other forms are so scarce that in borings usually only Lingula has been recorded.

Between the Ball and Peacock coals

The thickness between the Ball and Peacock coals is about 60 ft in the Duddingston, Portobello and Niddrie areas, a typical section being that at Monkton House Bore where the measures were 61 ft thick and the Black Metals Marine Band was in two bands as mentioned above:

At Gilmerton the Black Metals Marine Band was well developed, again in two leaves.

The thickest known development of the Black Metals Marine Band is near Loanhead, as for example in the Burghlee Colliery No. 1/53 Bore where the following section was obtained: Peacock Coal; fireclay, sandy towards base 3 ft 11 in.; sandstone, faky at top and base 18 ft; fakes and faky blaes with plant fragments 7 ft 9 in.; blaes and faky blaes with Lingula and other marine fossils 12 ft 6 in. on Ball Coal. Marine fossils are more abundant at the base and Lingula tends to be concentrated in layers.

In the southern part of the coalfield the marine band consists of a few feet of shale with a thin ironstone band yielding Lingula. Below this are sandy or silty shales with rare marine fossils, particularly lamellibranchs, often preserved in ironstone nodules. The band is well exposed by the Fullarton Water, 500 yd S.E. of Cauldhall Farm and in its continuation the Redside Burn, 800 yd S.S.W. of Redside. A typical section was recorded in Rosebery No. 7 Bore (1951) as follows: ?Peacock Coal; sandstone, rooty at top, faky at base 14 ft; fakes, striped, sandy and planty 3 ft 9 in.; blaes, grey, soft and planty 3 ft; blaes with Lingula and pyritized plants 3 ft; clayband ironstone with Lingula 1 in.; blaes with irregular bally clay-ironstone band 2 in.; fakes, grey, silty, with pyritized plants and fragments of brachiopods 2 ft on Ball Coal.

From Halkerston to Newtongrange the marine shale is split by a sandstone band which is often calcareous (Clough in Peach and others 1910, p. 221) with bedding disturbed by marine organisms and frequently containing Productus sp.Halkerston No. 494 Bore (1951) provided the following section: Peacock Coal; sandstone, faky and rooty at top passing down into sandy fakes 19 ft 9 in.; blaes, grey, micaceous, faky 3 ft 4 in.; blaes, grey, with Lingula and fish scales 2 in.; sandstone, hard, limy, disturbed and reworked, with obscure shell-traces, clayband ironstone balls at top and bottom 2 ft 3 in.; blaes, dark grey, micaceous, faky, with pyritous knots and patches, Lingula and fish scales 2 ft 9 in. on brownish grey rooty fireclay.

A section of the measures between the Ball and Peacock coals was provided by the Southside No. 978 Bore and was as follows:

In some parts of the Southside area a thick coarse-grained sandstone, pebbly at its base, is present. In Southside Nos. 159 and 165 bores, where this thick sandstone was found, the Black Metals Marine Band was absent and has probably been washed out along with the Ball Coal.

In No. 4 Bench, Cowden Mines, the thickness of measures between the Ball and Peacock seams was 59 ft 5 in. Farther north in the Dalkeith Colliery, the details of the succession were similar, although the interval was about 18 ft less. In Falside Hill No. 52 Bore, sited about half a mile south-east of Wallyford Colliery, the Black Metals Marine Band was in two leaves, separated by 5 ft of sandstone and fakes.

On the north-east corner of the coalfield, in Prestonlinks No. 36 Underground Bore the thickness of intervening strata was 49 ft 3 in., the Ball Coal being directly overlain by 1 ft of carbonaceous fakes, with megaspores, succeeded by 5 ft 6 in. of fakes and faky blaes with septarian nodules and occasional marine shells, overlain in turn by 3 ft 6 in. of grey fakes with marine shells.

Peacock Coal (Blackchapel of Duddingston; Blackchapel or Corbie Craig of Niddrie; Coronation of Newtongrange, Southside and Cowden; Four Foot of Carberry, Wallyford and Prestongrange)

In a crosscut mine just over half a mile north of Niddrie Collieries the Peacock Coal is in two leaves, each 2 ft thick, separated by 1 ft 6 in. of blaes. In Monkton House No. 37 Bore the details were: coal, bright 1 ft 5 in.; cannel 11 in. on coal, bright 1 ft 8 in.

The Peacock Coal appears to be absent in the Gilmerton district for it was not found in the crosscut mine which runs from the pit-bottom in a south-eastward direction ((Plate 3) and Macgregor 1937, p. 69).

In the Loanhead and Roslin neighbourhood the thickness ranges from 2 ft 7 in. to 5 ft and the seam is widely worked. The roof consists of strong, rather sandy fakes and blaes, while the floor is of sandstone, fakes or fireclay. The upper part of the coal was described as a fine splint, the lower, main part, as a rough coal with pyrites. A typical section in the Ramsay Pit 156-fm Crosscut Mine shows: sandstone; coal 1 in.; fakes with ironstone balls 1 ft 2 in.; coal 1 ft 3 in.; fireclay 2 in.; coal 3 ft 9 in. on fakes. Lingula was found in the fakes below the 1-in. coal in the crosscut mine at 275 fm.

At Mauricewood, the coal, 2 ft 6 in. thick (Plate 3), taken to be the Peacock, was previously named the Gillespie (Grant Wilson in Peach and others 1910, p. 211).

The mine-plans there show restricted workings in Peacock' Coal, the thickness varying from 2 ft 3 in. to 2 ft 4 in. Elsewhere in the southern part of the field it does not exceed 2 ft 3 in. and is occasionally absent.

The Peacock Coal has been worked on the eastern side of the coalfield. At Lingerwood and Lady Victoria pits it is up to 4 ft thick and has been known as the Coronation Coal, the correlation being certain.

In the Emily and Gore pits, however, difficultes of correlation arise. Thus in the Emily Pit (Plate 3) a split seam, with approximately 2 ft 9 in. of coal where recorded in both shaft and working sections, has been worked under the name 'Coronation'. Since in the shaft section, about 4 fm below this seam, there is a 2 ft 1 in. coal in the position of the Peacock or true Coronation, it seems likely that the 'Coronation' seam of this colliery is in fact the Kittlepurse (p. 47).

The problem at the Gore Pit is more difficult. The coal worked as the 'Coronation' may, as at Emily Pit, be the Kittlepurse. Such a correlation presupposes either that the Peacock (or true Coronation) exists below the seam worked as 'Coronation' or else that it is missing in that area.

At Fushiebridge and Arniston Mains, despite the correlation shown on (Plate 3), a similar doubt remains as to the identity of the seams immediately above the Black Metals Marine Band.

A measured section of the Peacock Coal in Lingerwood Crosscut Mine gave: fakes; coal 3 in.; grey freestone 1 ft; coal 3 ft 7 in. on sandstone.

Between Vogrie and Southside the coal is subject to washouts later filled by the overlying Coronation Sandstone and thicknesses of 1 ft 2 in. to 4 ft were recorded, the coal occasionally occurring in two leaves.

At Southside No. 150 Bore the seam was composed of 3 ft 7 in. of bright coal with some splint ribs, but in this district there is again a tendency to form two leaves as at Vogrie Burn No. 30 Bore where the section was : coal 7 in.; fireclay 5 in. on coal 2 ft 5 in.

In the Cowden–Crossgatehall–Carberry area the Peacock Coal generally contains a parroty band, representative sections in that region being as follows: Cowden Mines: coal 9 in.; parrot coal 9 in. on coal 2 ft. Dalkeith Colliery: 2 ft 4 in. with top 6 in. to 1 ft parroty. Carberry Colliery: coal 11 in.; parrot coal 1 ft on coal 1 ft 8 in.

Details of the coal in the underground bore in Prestonlinks Colliery were: coal 9 in.; fireclay, faky fireclay and coaly fireclay 1 ft 11 in.; coal 3 ft 9 in.; fireclay and coaly fireclay 1 ft 6 in. on coal 9 in.

Measures between the Peacock and Kittlepurse coals

In the Duddingston and Niddrie regions the measures between the Peacock and Kittlepurse coalsare about 30 ft in thickness. At Monkton House No. 37 Bore this belt of strata was 43 ft 6 in. thick and included a hard, fine-grained sandstone 24 ft thick. In the Loanhead and Newtongrange districts 50 to 25 ft or less of measures separate these coals. Between Newtongrange and Southside the Coronation Sandstone, often coarse and in places 50 ft thick, overlies the Peacock Coal, whilst fakes and fireclay, frequently with a coaly band, surmount the sandstone.

In the Southside region the interval ranges from 8 ft 3 in. to 15 ft 6 in. North of the D'Arcy Anticline in the Cowden Mines the coals were separated by a sandstone 9 ft 9 in. thick and in the railway cutting at Crossgatehall the separation was only 3 ft 6 in. The thickness of the intervening beds increases to the north of Crossgatehall, being about 12 ft in Carberry Colliery and 19 ft to 24 ft in Prestongrange workings.

Kittlepurse Coal (Little Gillespie of Duddingston and Niddrie; ? 'Coronation' of Emily Pit; Blackbird of Lingerwood and Cowden, Lower Blackbird of Southside; Three Foot of Carberry, Wallyford and Prestongrange)

The section of the Kittlepurse Coal in a crosscut mine in Gilmerton Colliery was: parrot coal, poor 1 ft 2 in. on coal 1 ft 3 in. Between Loanhead and Roslin 1 ft 10 in. to 3 ft 2 in. is the thickness and the coal has been most widely worked at Roslin Colliery. Here the roof-blaes contains an occasional ironstone rib carrying fish remains. At the Ramsay Pit 156-fm Crosscut Mine the following section was obtained: blaes, parroty and irony at base; coal, bright with splint ribs 2 ft 3 in.; coal, foul 9 in. on fireclay with ironstone balls.

South of Roslin the Kittlepurse Coal may reach as much as 1 ft 6 in. but is absent over a large area, particularly in the extreme south.

Northwards again it improves so that at Fushiebridge and the Gore Pit the coal correlated with the Kittlepurse is 1 ft to 1 ft 1 in. thick (p. 48).

At Emily Pit the record of the shaft section (Plate 3) is not clearly understood at this horizon. As mentioned on p. 46 the coal correlated with the Kittlepurse appears from its measurements and surveyed level to correspond with the coal worked in the pit under the name 'Coronation'. The coal in question in the shaft measures : coal 1 ft; fireclay 1 ft; coal 1 ft 11 in. on coaly fireclay, whilst one of the working sections of the 'Coronation' Coal near the pit-bottom is identical. As the pits adjoin and the sections are similar it is at least possible that the coal worked as 'Coronation' at the Gore Pit is in fact also the Kittlepurse. If this is the case then the true Coronation (Peacock) is probably missing at, and south of, the Gore Pit.

A split development of the seam occurs in the Southside area where it was worked opencast as the Lower Blackbird Coal. For example in Southside No. 165 Bore, the details were: coal 10 in.; fireclay 2 in.; sandy fakes and faky sandstone 2 ft 3 in.; fireclay, dark 3 in. on coal, bright with dull ribs 1 ft 9 in.

In the Cowden–Crossgatehall–Carberry area the coal generally occurs in two leaves, the section seen in the Cowden Mines being: coal 1 ft; coaly blaes 1 ft 6 in. on coal 2 ft; while in the railway cutting at Crossgatehall the seam was 2 ft 5 in. thick, splinty towards the top, with a 7-in. parting near the middle.

A representative section as found in Carberry Colliery is: coal 1 ft; fireclay 1 ft 2 in. on coal 1 ft 6 in. Farther north in Prestonlinks No. 36 Underground Bore 3 ft 4 in. of bright and dull banded coal with plies of foul coal were found.

Measures between the Kittlepurse and Calpatie coals

The measures between the Kittlepurse and Calpatie coals along the western outcrops are variable and include a thin coal at Loanhead, but are thicker and mainly arenaceous south of here; the thicknesses are shown on (Plate 3). The roof shale of the Kittle-purse contains fish scales at Roslin. On the eastern side of the basin, north of the D'Arcy Anticline, in Cowden Mines, the Kittlepurse is again overlain by a few inches of dark blaes with fish scales. A 6-in, coal was noted in Crossgatehall railway cutting, set in sandstones which occupy almost all the 31 ft 10 in. of section between the two coals. In Falside Hill No. 48 Bore the Kittlepurse Coal is apparently absent and the 1-ft coal just over 50 ft above the Peacock is thought to be the Calpatie.

Calpatie Coal (Copatie; Perpetual of Gilmerton; Upper Blackbird of Southside)

The Calpatie Coal is absent or poorly represented in the Duddingston–Niddrie area, but was found 17 ft above the Kittlepurse in Monkton House No. 37 Bore and is 16 ft above that coal in a crosscut mine at Gilmerton Colliery.

In the Loanhead district, the coal is very variable, its thickness ranging from 3 in. to 2 ft 5 in. The roof measures are of blaes and ironstone known as the Calpatie Ironstone (No. 2 Blackband Ironstone of Vertical Sections, Geological Survey, 1909). The pavement consists of seatclay or sandy shale. The seam is reported to have been worked to a small extent in the Loanhead district, probably for the ironstone. The roof shale and ironstone carry ostracods and fish scales with occasional Lingula. A 6-in. ironstone was formerly worked at Gilmerton where it was separated from the roof-coal of the Calpatie by 4 in. of parroty blaes. In the Bilston Burn the Calpatie Coal lies close below the Blackchapel Coal, the section here being: Blackchapel Coal; sandstone and fakes, rooty, with ironstone balls at base 5 ft 3 in.; faky blaes with ostracods and fish remains 4 in.; clayband ironstone, nodular, with ostracods and Lingula 3 in.; blaes 3 in.; clayband ironstone, nodular 1 in.; blaes, coaly at base 4 in.; coal (Calpatie) 4 in. on sandy fireclay. A good section of the Calpatie Coal and Ironstone was recorded in the Roslin Colliery No. 1 Up Bore (1950): blaes, parroty, irony 10 in.; and blaes, black with brown ironstone balls 9 in. (forming the Calpatie Ironstone); blaes, faky and irony with fish scales and Lingula 1 ft; coal (Calpatie) 2 ft 5 in. on fireclay.

At Greenlaw and Mauricewood the presumed equivalent of the Calpatie Coal is 2 ft 4 in. to 2 ft 6 in. thick and was named 'Blackchapel' by Howell (Howell and Geikie 1861, p. 89). South of Penicuik and in the remainder of the southern area it is thin or absent. At the Gore Pit the seam is absent or may possibly be the coal about 1 ft thick, here referred to as the Kittlepurse (p. 47). The fossiliferous horizon a little above the Calpatie has also been found at the Gore Pit as shown by the following section in a return airway: Blackchapel Coal (here known as Blackbird); fakes, hard sandy 1 ft; faky fireclay 1 ft; blaes, hard carbonaceous with ironstone nodules and ostracods 1 ft; fireclay, faky 8 in.; sandstone with fakes bands 2ft; fakes and blaes with ironstone balls 1 ft; parroty blaes 1 in.; coal (?Kittlepurse) 1 ft 1 in.; sandstone and fakes bands 8 ft 5 in.; coal 2 in.; sandstone and fakes 8 ft 10 in.; fireclay 1 in.; coal 6 in.; fireclay 4 in.; coal ('Coronation') 1 ft 5 in.

At Lady Victoria Pit the Calpatie, 1 ft 5 in. thick, was referred to as the Blackbird (Vertical Sections Sheet 1 D, Geological Survey, 1909). The seam at Lingerwood is separated by about 11 ft of faky sandstone from the overlying fossiliferous band which was here proved to contain Lingula and fish remains. Between Vogrie and Southside the coal is only 1 ft 4 in. thick and even then split by dirt partings. The name Upper Blackbird was used for this seam in the Southside area where it was worked opencast. The shale above the seam here usually carries ostracods and fish scales.

The Calpatie Seam was 2 ft 1 in. thick at Cowden Colliery, and the section in Carberry Colliery No. 3 Shaft was : coal 1 ft 4 in.; blaes 2 ft 3 in. on coal 6 in.

Measures between the Calpatie Coal and the Blackchapel Coal

The measures between the Calpatie Coal and the Blackchapel Coal consist of 9 ft 3 in. of rooty faky fireclay in Southside No. 165 Bore. In Brosie Mains No. 3 Bore, where the intervening strata were 14 ft 10 in. thick, a thin bed of blaes with ostracods was found about 4 ft below the Blackchapel (Lower Siller Willie of Southside). The measures between the seams have increased in thickness in the Cowden–Crossgatehall region, and reach 35 to 50 ft, including a thick sandstone. Farther north, near Carberry Colliery the interval is about 30 ft and contains a sandstone about 6 ft thick. In Falside Hill No. 48 Bore the Lingula bed was found 6 in. above the Calpatie Coal.

Blackchapel Coal (Siller Willie or Sparable of Lingerwood; Blackbird of Gore and Emily Pits; Lower Siller Willie of Southside; Five Foot of Prestongrange)

The Blackchapel Coal is poorly developed or absent at Duddingston and Niddrie. In Monkton House No. 37 Bore the seam, lying 20 ft above the Calpatie Coal, appears to have split and to be represented by two coals 14 ft apart, the upper totalling 1 ft 4 in. and the lower 11 in.; the intervening strata consist of seatclay and sandstone. The coal occurs in three leaves 7 ft 6 in. above the Calpatie Seam at Gilmerton and Melville Estates No. 1 Bore,^‡1  600 yd S.E. of Gilmerton Colliery. In a crosscut mine at Gilmerton Colliery the section was: coal 2 ft; blaes 2 in.; coal 1 ft 6 in.; blaes 1 to 2 in. on coal 1 ft 8 in., while the bore showed: coal 10 in.; blaes and coal 1 ft 6 in.; coal 3 in.; blaes 3 in. on coal 9 in.

In the neighbourhood of Loanhead the Blackchapel is an important coal, though it suffers from washouts, now generally filled by the thick sandstone which overlies it. As a result of this local erosion and of regional thinning the thickness varies from a maximum of 5 ft 4 in. It has been described as a soft, free coal of poor quality with ribs of stone and pyrites. Working thicknesses are: Ramsay Pit: 3 ft 3 in. to 4 ft 7 in. with a variable parting of 3 to 12 in. in the lower part; Burghlee: 2 ft 9 in. to 4 ft. At Roslin where the coal is split into two or more leaves and is locally missing owing to washouts, it has not been worked.

In the south-west the Blackchapel again becomes workable between Roslin and Auchendinny. At Mauricewood and Greenlaw the coal is respectively 4 ft 8 in. and 4 ft 4 in. thick, in both cases with a parting. Earlier published sections of these pits refer to other coals lower in the succession as the 'Blackchapel' (Grant Wilson in Peach and others 1910, p. 211; Howell 1861, p. 89), the true Blackchapel being named the 'Stairhead'. In mine-plans a worked area of the 'Stairhead' is shown with a thickness of 3 ft.

The Blackchapel Coal is either thin or absent at the southern end of the Midlothian Basin though there is a possibility that in the Lilyburn–Auchencorth area it may be represented by a coal here referred to as the Gillespie (p. 51). It reappears near Fushiebridge in the south-eastern part of the field where it is the lowest of three coals close together and reaches a thickness of 2 ft 10 in. as shown in Fushiebridge No. 137 Bore (Plate 3).

At the Gore and Emily Pits the Blackchapel Coal is known as the Blackbird. It is frequently split by fireclay ('dirt') partings. Working thicknesses range from 2 ft 2 in. in three leaves to 3 ft 6 in. in two leaves. Typical sections recorded in the Gore Pit are: coal 7 in.; dirt 2 in. on coal 2 ft 7 in. and in another place: coal 7 in.; dirt 2 in.; coal 1 ft 3 in.; dirt 1 in. on coal 7 in. In the Emily Pit Shaft (Plate 3) the coal 3 ft 3 in. thick, is directly overlain by sandstone.

In the Lady Victoria and Lingerwood pits, however, strata with thin coals come between this sandstone and the Blackchapel Coal. The section in the shaft of the former pit reads: sandstone; blaes 1 ft; coal 9 in.; fireclay and fakes 2 ft 11 in.; coal 1 ft 5 in.; blaes 1 ft; coal (Blackchapel) with 9-in. blaes parting 3 ft 10 in. on blaes and fakes. The Blackchapel Coal is known as the Lower Siller Willie in the Southside area, where it was worked opencast.

The section of the Blackchapel Coal in Southside No. 165 Bore was: coal, bright 10 in.; fireclay, dark, faky with ironstone balls at base 1 ft 6 in. on coal, hard, bright with dull bands 4 ft. Representative sections in the Cowden–Crossgatehall region are: Cowden Mines: coal, splinty 1 ft; parting 2 in.; coal 1 ft 9 in.; fireclay, sandy 1 ft on coal 9 in. Dalkeith Colliery: coal, parrot 6 in. on coal 1 ft. Crossgatehall railway cutting: coal 1 ft 1 in.; parting 8 in.; coal, bright 1 ft 5 in.; parrot 6 in.; parting 1 in. on coal, bright 11 in. Near Carberry Pit-bottom the details were: coal 9 in.; parrot partings 3 in. on coal, rough 1 ft 3 in.: and in Prestonlinks No. 36 Underground Bore the seam consisted of 4 ft of bright and dull banded coal.

Measures between the Blackchapel and Gillespie coals

The measures between the Blackchapel and Gillespie coalswere over 24 ft thick at Monkton House No. 37 Bore and included a 1 ft 4 in. coal 10 ft 10 in. above the Blackchapel. The increase in thickness of these measures to 84 ft 6 in. at Gilmerton Colliery is largely accounted for by sandstones, one of which is over 70 ft thick.

Near Loanhead and Roslin the Blackchapel Coal is succeeded by a thick, often coarse and even pebbly sandstone. Above the sandstone come seatclay and sandy shale with coal-streaks and sometimes a thin coal with a roof of shale and ironstone nodules carrying fish remains. Sandy shale and seatclay underlie the Gillespie Coal. These strata vary from 50 to 100 ft in thickness. At Mauricewood and at Newton-grange, as mentioned above, strata with thin coals overlie the Blackchapel, and the sandstone under the Gillespie Coal is thin.

The Blackchapel and Gillespie coals are less than 8 ft apart in Cowden Mines, but in Dalkeith Colliery, about half a mile to the north-east, this interval has increased to 41 ft owing to the presence of a thick sandstone. At Carberry Colliery it is again reduced to about 11 ft while a figure of 28 ft 4 in. was noted in Falside Hill No. 48 Bore where a 3-in. coal was included in the succession and a sandstone 10 ft 6 in. thick at the top. At Prestongrange and Prestonlinks the corresponding figures ranged from 18 ft to 40 ft 6 in., in the latter case including three thin coals.

Gillespie Coal Group

Gillespie coals (Great Gillespie of Duddingston and Niddrie; Gillespie, Wee Gillespie (or Moffats) and Charlies of Loanhead and Roslin; 'Great Seam and Ironstone' of Mauricewood; Upper Siller Willie and Teenie of Southside; Siller Willie of Cowden; Jewel or Splint of Carberry; Clay of Prestongrange)

The term Gillespie Coal Group is here used to describe the variable assemblage of coals and associated measures which lies at or about the horizon of the Gillespie Coal of earlier publications (Milne 1839, pl. xviii; Howell 1861, p. 84; Peach and others 1910, pp. 196, 197, 200). It includes the important Loanhead No. 2 Ironstone.

The following table shows the equivalent names of members of the group in the different areas:

The Gillespie Group in Monkton House No. 37 Bore was as follows: coal 1 ft 7 in.; fireclay, grey, lipy 1 ft 10 in. on coal 3 ft. A coal 1 ft 4 in. thick lying about 10 ft below this may represent the lowest member of the sequence. In the Gilmerton Diamond Bore a 3-ft seam, the lower 3 in. being splint coal, was overlain by 17 ft of strata above which was a 1-ft coal in two leaves with 2 in. of ironstone. At Loanhead and Roslin the group is best developed. The lowest coal, there called the Gillespie, was described as a soft, rough coal of good to medium quality, with a thickness of 2 ft 2 in. to 3 ft 9 in. A typical section in the Ramsay Pit 156-fm Crosscut Mine was: blaes faky; coal, cannel, coarse 1 in.; coal, mainly bright 3 ft 6 in. on fireclay with ironstone balls.

In recent underground bores in Burghlee Pit the cannel and the blaes in the roof of of the seam were found to contain fish remains and ostracods. The Wee Gillespie Coal near Loanhead lies as much as 12 ft above the Gillespie, though south of Roslin as little as 9 in. of strata separate the two seams. The thickness of the seam varies from 1 ft 5 in. to 2 ft 4 in. but it is not known to have been worked by itself. Sandy shale or shale form the roof and a seatclay the floor.

At Mauricewood and Greenlaw the Gillespie and Wee Gillespie coals are very close. At these two pits, indeed, the combined seams were worked together under the mistaken impression that they were the Great Seam (Howell in Howell and Geikie 1861, p. 89; Grant Wilson in Peach and others 1910, p. 211). This mistake undoubtedly arose because in this district where the coals of the Gillespie Group have come close together (Mitchell 1955, p. 44) the true Great Seam has deteriorated (p. 56). The thickness of the combined Gillespie and Wee Gillespie varied from 5 ft 2 in. in two leaves to 4 ft 3 in. in three leaves, but workings were on a limited scale and mainly designed to win the overlying ironstone.

The Loanhead No. 2 Ironstone, which is closely associated with the Charlies Coal, was the most important ironstone worked in the earlier part of the present century (Robertson in Macgregor and others 1920, p. 181). It was found to be of economic thickness, and was worked at all the coal-pits between Loanhead and Mauricewood. A maximum thickness of 3 ft 7 in. of coal and ironstone was recorded in the Ramsay Pit and in the Mountmarle Bore, though working thicknesses were rather less. Between Loanhead and Mauricewood it lies from 18 ft to 1 ft 4 in. above the Wee Gillespie Coal, the greater thickness being accounted for by the presence of more sandy or silty sediments. The ironstone was earlier referred to by Traquair (1903, pl. II) and by the Geological Survey (Vertical Sections Sheet 1C, Geological Survey, 1909) as the 'No. 3 Blackband Ironstone', the name 'No 2 Blackband Ironstone' being then used for the Rumbles Ironstone (p. 56). Large numbers of fish genera are recorded by Traquair from the 'Boroughlee Ironstone', but the Loanhead No. 2 and the Rumbles Ironstone both yield fish remains and both were worked at Boroughlee (now known as Burghlee) Pit. It is not therefore clear from which of the two ironstones Traquair's specimens were derived. It is even possible that they came from both these horizons. A section of the Loanhead No. 2 Ironstone in the Ramsay Pit 156-fm Crosscut Mine gave: blaes with fish remains; ironstone, clayband 4 in.; cannel, hard, irony with fish remains 5 in.; ironstone with ribs of cannel 3 in.; cannel, coarse 3 in.; cannel 1 ft; blackband ironstone 10 in.; coal, foul 1 in.; coal, bright 4 in. on fire-clay with ironstone balls.

At Mauricewood and Greenlaw the ironstone was worked most extensively, the thickness ranging from 10 in. to 2 ft 9 in., but was here thought to be the Great Seam Ironstone (Robertson in Macgregor and others 1920, p. 187). It was mined along with the Mauricewood 'Great Seam' which lies close below it.

The full section of the Gillespie Group (Mauricewood 'Great Seam and Ironstone') is given in the following sequence proved at Mauricewood: fakes; daugh 3 to 6 in.; coal 9 in.; fireclay, hard 1 ft; coal, gas 3 in.; blackband ironstone (Loanhead No. 2) 11 in.; daugh 3 to 4 in.; fireclay and ironstone balls 3 ft to 3 ft 6 in.; blaes, dark 6 to 7 in.; coal, free 1 ft, fireclay parting, hard 9 in. and coal 9 in. (Wee Gillespie in two leaves); fireclay, hard 2 ft 6 in.; coal 2 ft 6 in. (Gillespie).

The Charles Coal may reach a thickness of 1 ft 9 in. in the Loanhead—Roslin district in places where the Loanhead No. 2 Ironstone is poorly developed or absent. A Lingula band occurs in the blaes above the Charlies Coal.

In Burghlee No. 1/53 Underground Bore the following section, from the Wee Gillespie Coal to the Lingula band, was recorded: blaes with Lingula and fish remains 11.5 in.; coal 4 in.; fireclay 8 in.; blaes, parroty and cannel bands with pyritized plants and fish remains 2 ft 9 in.; blackband ironstone with ostracods 1 ft; blackband ironstone, inferior 1 ft 3.5- in.; coal 3 in.; blackband ironstone 4 in. (base of Loanhead No. 2 Ironstone); fireclay and faky sandstone 11 in.; fakes 1 ft 10 in.; clayband ironstone 3 in.; blaes 4 in.; Wee Gillespie Coal.

To the south and east of Mauricewood the Gillespie Group thins, the coals split up and the Loanhead No. 2 Ironstone fails. The group is of little economic importance south of Penicuik House though the Penicuik No. 117 Bore a quarter of a mile south of the house probably passes through a fault which accounts for the absence of the coals at that place.

At Cornton the coals have not been recognized, but at Brunston the Gillespie Group may be represented by three coals originally described by Hinxman (in Peach and others 1910, p. 214) as the Great, Stairhead and Gillespie, the lowest being shown as 240 ft above the Corbie Craig. The section in question is as follows: sandstone; coal 'Great Seam' 1 ft; fireclay and ironstone balls 5 ft 3 in.; coal 'Stairhead' 1 ft 11 in.; fireclay and ironstone balls 3 ft 3 in.; coal 'Gillespie' 1 ft 8 in. on indurated clay.

In the southern part of the coalfield between Brunston, Kirkettle and Auchencorth a split coal lying 40 to 50 ft above the Black Metals Marine Band has been taken to represent the Gillespie Group of coals and is named Gillespie Coal on the maps. It varies from 1 ft 11 in. to 3 ft 9 in. though it is occasionally thin or absent. During the prospecting for opencast coal in 1950 and more recently on certain opencast plans this seam was named the Perpetual Coal and it still remains a possibility that it is lower in the succession than the Gillespie Group (p. 49). The section of the coal in Auchencorth No. 14 Bore was: fireclay, faky with ironstone balls; fireclay, coaly, hard 4 in.; coal, parroty 11 in.; coal 1 ft 3 in.; fireclay, coaly 2 in.; coal 9 in.; fireclay, coaly 2 in.; coal 10 in. on sandstone with fireclay bands.

From Lilyburn to Fushiebridge the Gillespie Group occurs either as two seams up to 12 ft apart or as a set of thin coals and fireclays. A thin band of brown and grey breccia with small angular clay fragments is a persistent feature of the roof of the topmost coal. Near Fushiebridge two seams of coal of workable thickness occur close together and are thought to represent the Gillespie Group. From Redside to Fushiebridge the shale above the upper coal has yielded Lingula, Orbiculoidea and other fossils. The section in Fushiebridge No. 160 Bore was: fakes and faky blaes with Lingula 1 ft 11 in. coal, clarain and fusain 5 in.; fakes, coaly 2 in.; coal, clarain and fusain 2 ft 4 in.; fireclay, faky and fakes 2 ft on coal, clarain and fusain 2 ft 8 in. In downward succession the three seams probably are the Charlies, Wee Gillespie and Gillespie coals.

Farther north at the Gore Pit the Gillespie Group has been worked as the Siller Willie Coal in two leaves sometimes referred to as the Siller Willie Top and Bottom coals. A section of these coals measured in a mine for a return airway in the Gore Pit reads as follows: blaes, soft and sulphury-weathering with scarce Lingula fragments 1 ft 6 in.; coal 4 in.; fireclay 3 in.; coal 1 ft 11 in.; coaly fireclay 2 in.; coal 7 in.; fireclay 1 in.; coal 1 ft 8 in. (Siller Willie Top or Upper leaf); fireclay and faky fireclay 3 ft 3 in.; coal 2 ft and coaly fireclay parting 7 in. and coal 1 ft (Siller Willie Bottom Coal); fire-clay 2 ft on coal 5 in. The spacing of the seams varies considerably so that sometimes only one leaf has been worked. At the neighbouring Emily Pit the shaft section (Plate 3) shows the Gillespie Group represented by two separate seams. In the workings in this pit west of the shaft, however, a typical section of the 'Siller Willie' Coal shows: coal 2 ft 8 in.; clay 1 ft 10 in.; coal 2 ft 3 in. • dirt 2 in. on coal 5 in.

In the Vogrie (Old) No. 1 Pit Shaft a coal named 'Siller Willie' lay 10 fm below the Great Seam. A section of the seam in the pit records: clay 3 in.; coal 8 in.; clay 2 ft 6 in., on coal 3 ft. It is possible that in this case the seam is the Blackchapel Coal (p. 48).

In the Newtongrange and Southside districts the Gillespie Group consists of three seams, the lower two known at Southside as the Upper Siller Willie coals and the topmost as the Teenie. The Teenie Coal has Lingula in the roof shales. In the old shaft section of Lingerwood Pit the name 'Siller Willie' was used for the group but in the crosscut mine, driven in 1952 for the main haulage, the name Siller Willie is used for the Blackchapel Seam (Plate 3). In this mine the following section was measured: fakes and faky blaes with Lingula 1 ft; coal 2 in.; fireclay 9 in.; coal (Teenie) 1 ft 10 in. to 2 ft 5 in.; fireclay with ironstone balls 4 ft 5 in.; coal (top leaf of Upper Siller Willie) 2 ft; fireclay and blaes 1 ft 6 in.; coal 6 in.; blaes 2 ft 5 in.; coal (bottom leaf of Upper Siller Willie) 2 ft 4 in. coaly blaes and fireclay 1 ft 4 in. resting on sandstone.

In most of the Hillhead and Southside area the two leaves of the Upper Siller Willie are close together as one coal. An example is Hillhead No. 291 Bore (Plate 3), where, however, the Teenie Coal, 18 in. thick with Lingula in the roof shales, lies 18 ft above. The Upper Siller Willie in Brosie Mains No. 3 Bore was 3 ft thick and included bright and dull banded coal.

Details of the Gillespie Group at Cowden Mines were: blaes and ironstone with Lingula; coal 4 in.; blaes, parroty 2 in.; coal 6 in.; parting 2 in.; coal 1 ft 10 in.; measures 13 ft 6 in.; coal 1 ft 4 in.; fireclay 1 ft; coal 3 ft 6 in.; fireclay 9 in.; faky sandstone 4 in. on coal 1 ft. In Dalkeith Colliery the details were: faky blaes with plants; coal, dirty 9 in.; fireclay 9 in.; coal 4 in. (probably Charles); separated by an interval of 15 ft 9 in. from coal with a dull band in the centre 1 ft 5 in.; sandy fakes 2 ft; coal, bright 1 ft 5 in.; coal, dull 3 in. on coal, hard, streaky 2 ft.

Near the pit shaft at Carberry 4 ft of the coal here known as the Carberry Jewel were recorded, but just over a mile to the north-east the section was : coal 10 in.; parting 9 in. on coal 5 ft, a 4-in. coal noted in the shaft some 27 ft higher in the succession presumably being the attenuated upper seam of the Cowden and Dalkeith sections (Plate 3).

In Prestongrange Colliery a coal on or at about this horizon is known as the Clay Coal and is generally found in two leaves, the rangeof thickness being: coal 10 in. to 1 ft 3 in. parting 1 to 5 in. on coal 1 ft 3 in. to 1 ft 11 in. Corresponding details at Prestonlinks No. 36 Underground Bore were: coal, hard, bright 11.5 in.; carbonaceous fakes 0.5 in. on coal, hard, bright 1 ft 6 in.

Gillespie Coal Group to base of Great Seam

The strata between the top of the Gillespie Group and Great Seam consist mainly of sandstone but include the Stairhead Coal and in places a seam slightly lower in the succession known as the Wee Stairhead. The thickness of these strata varies from about 90 ft in a crosscut mine in Gilmerton Colliery to some 20 ft near Lilyburn and Kirkettle in the south of the coalfield.

Since the Charles and Stairhead coals are difficult to recognize in the north-eastern part of the field and the Wee Stairhead is absent, the succession may be illustrated by the sequence found between the Gillespie and Great seams in the Cowden Mines, examined in 1933 and published later as the Smeaton succession (Macgregor 1937, p. 71; 1938, p. 62) as follows:

The identification of Lingula above the coal here correlated with the Stairhead must be regarded as tentative since it was a field determination. It constitutes the only record of this shell from this horizon in the Midlothian Coalfield.

The succession in Dalkeith Colliery is generally similar to that found in Cowden Mines, but the coal probably representing the Charlies Coal is thin and only fragments of fossil plants were found in the strata immediately above it (p. 52). Fish scales occur in parroty blaes overlying the seam representing the Stairhead Coal.

In Carberry Colliery the interval between Gillespie and Great coals is about 103 ft and includes three coals, the highest of which lies approximately 15 ft below the Great Seam, and probably represents the Stairhead Coal. A sandstone 32 ft thick occupies the central part of the succession and a 4-in. ironstone occurs immediately over a 2-in. coal which is found about 36 ft below the Great Seam. Details of the strata overlying the Gillespie Coal in Falside Hill No. 48 Bore were found to be:

At Wallyford Colliery the Great lies about 177 ft above the Gillespie with three thin coals intervening. The two upper contain parrot coal and the higher of these two is overlain by blaes with lamellibranchs (Anderson in Peach and others 1910, p. 229).

At Prestongrange the corresponding thickness is about 100 ft and includes the Diver Coal, 2 ft thick, lying about 30 ft above the Gillespie. In Prestonlinks No. 36 Underground Bore where the Great lies 43 ft 3 in. above the Gillespie, two 1-ft coals occur 7 ft 4 in. apart; the lowest, with a Lingula band close above it, lies 15 ft above the Gillespie (Jewel or Splint).

Wee Stairhead Coal

The Wee Stairhead is a coal only developed between Gilmerton and Roslin, where the maximum thickness is 1 ft 10 in. and the seam, in two leaves, is usually of poor quality. It lies 20 to 60 ft above the Loanhead No. 2 Ironstone or Charles Coal and from 5 to 20 ft below the Stairhead Coal. It is not known to have been worked. A representative section of the strata between the Loanhead No. 2 Ironstone and Stairhead Coal was obtained in Burghlee No. 1/53 Underground Bore: Stairhead Coal; fakes and sandy fireclay 1 ft; sandstone with fakes bands 10 ft; fakes and blaes, planty 9 in.; coal (Wee Stairhead) 1 ft 4 in.; sandstone, faky top and base 5 ft 1 in.; fakes and blaes, planty 1 ft 4 in.; fireclay and fakes, sandy 1 ft 5 in.; sandstone and faky sandstone 20 ft; blaes with Lingula and fish remains 11.5 in.; Loanhead No. 2 Ironstone.

In southern districts as little as 10 ft of strata separate the Gillespie Group and Stairhead Coal. The Lingula band has been found near Redside and Fushiebridge (p. 52).

Stairhead Coal (Diamond of Newtongrange)

The Stairhead Coal, which lies about 60 ft above the Gillespie at Portobello is an important seam, of which the following are representative sections at the north end of the field: Portobello railway cutting: coal, bright 1 ft 6 in.; coal, parrot 2 ft; on coal, bright 3 ft; Gilmerton Colliery: coal 1 ft 4 in.; parrot coal:8 in. on coal 1 ft 2 in.; Gilmerton Diamond Bore: coal 1 ft 5 in.; coal, parrot 5.5 in.; coaly blaes 0.5 in. on coal 1 ft 2 in.; Monkton House No. 37 Bore: coal 3 ft 7 in.; faky fireclay 4 in.; on coal 1 ft.

The Stairhead is much worked in the Loanhead area. At the Ramsay Pit its thickness ranges from 2 ft 11 in. to 3 ft 5 in. with a parting in the middle. At Burghlee and Dryden it is from 2 ft 2 in. to over 3 ft and at Roslin from 1 ft 10 in. to 2 ft 5 in. It is described as a rough, second quality coal. The roof is usually sandstone, though in the eastern part of Burghlee Colliery this gives way to sandy shale. The pavement may be of sandstone, sandy shale or silty seatclay. Erosion of the top of the seam has occurred in several places. The overlying sandstone thins to the east so that in the Mountmarle Bore and Burghlee underground bores the Stairhead lies close below the Great. Sections of the Stairhead Coal are as follows: Burghlee, east side: sandstone; blaes 1 ft 6 in.; coal, rough and hard 6 in.; coal, rough 1 ft 5 in.; coal, parrot rough 4 in.; coal, rough and tumphy 4 in.; coal, rough 1 ft 5 in.; fireclay 4 in. on blaes. Ramsay Pit 156-fm Crosscut Mine: sandstone; coal, bright 1 ft 2 in.; coal, poor 3 in.; coal 1 ft 6 in. on sandstone. In this section about 11 in. of coal are missing by erosion at the top of the seam.

The coal worked under the name Stairhead at Mauricewood is probably the Blackchapel. The true Stairhead is probably the coal 1 ft 2 in. thick underlying the Union Coal (p. 55). At Kirkettle and Lilyburn it is 1 ft to 1 ft 6 in. and over the remainder of the southern area 1 ft or less.

In the eastern part of the coalfield the Stairhead is known as the Diamond. At Fushiebridge the thickness is 2 ft or less. Between Vogrie and Newtongrange it ranges from 1 ft 7 in. to 2 ft 4 in. and has been worked to a limited extent for house coal. The sandy shale or sandstone roof is accompanied by a floor of sandstone, sandy shale or seatclay.

In Southside No. 989 Bore the Diamond Coal, consisting of bright and dull banded coal, was 2 ft 1 in. thick and lay 18 ft 4 in. above the Teenie and 1 ft 10 in. below the Great Seam.

At Portobello railway cutting about 7 ft of fakes and blaes overlie the Stairhead followed by 27 ft of sandstone on which rests the Great Seam.

Between Gilmerton and Loanhead 20–35 ft of sandstone with an uneven base separate the two seams. This sandstone is 38 ft thick in Roslin Colliery No. 1 Mine and is overlain by 2 ft 6 in. of rooty fakes followed by 6 in. of coal and 2 ft 1 in. of fakes with coal streaks. This coal here lies 18 ft 7 in. below the Great Seam. From a study of nearby bore sections it appears to have split from the base of the latter coal, the interposed strata consisting of fireclay and rooty fakes with sandstone bands. Eastwards and southwards from Loanhead and Roslin the Stairhead Coal usually lies close below the Great Seam.

Great Seam to base of Index Limestone

The strata from the bottom of the Great Seam to the Index Limestone vary in thickness from about 200 ft in the north to 60 ft in the south of the coalfield. In the Prestonlinks No. 36 Underground Bore they were approximately 129 ft thick. In addition to the Great Seam itself they include three or four named coals and an ironstone of importance. In ascending order these are the Rumbles Coal, the Rumbles or No. 3 Ironstone, the Flex and the Geordie coals.

Great Seam (Union of Mauricewood; Rumbles of Brunston)

The Great Seam, the thickest coal of the Limestone Coal Group in the Midlothian Coalfield, is a composite seam which frequently includes ribs of parrot coal and thin dirt partings. The range in thickness and the constitution are shown on (Plate 3) and (Figure 12).

In the Loanhead area thin variable coals occur close above the seam, the upper part of which is often left in the roof during mining. Consequently working thicknesses are not generally overall thicknesses. A band of parrot or cannel appears to be a persistent feature of the upper part of the seam here. In the Roslin district the lowest portion of the seam splits off (p. 54), the whole seam thins southwards, and the Rumbles Coal comes to lie close above it. The Great Seam has been worked well under the basin at one point where the Burghlee workings on the west are no more than 1000 yd from those of Easthouses on the east.

At Greenlaw and Mauricewood the Great Seam is not well developed, being only 2 ft 3 in. to 4 ft thick. It was known as the Union Coal and originally correlated with the Flex Coal. The seam worked there as the Great Seam is now known to be the Gillespie Coal (p. 50). Between Mauricewood and Cornton the true Great Seam measures from 4 ft 8 in. to 2 ft 7 in. but appears to be absent in Cornton Bore where its place is probably taken by a group of fireclays.

At Brunston, where the coal was known as the Rumbles or Rumbolds, a thickness of 4 ft 11 in. was recorded in the crosscut mine, but this thickness is suspect and may include partings, or be a horizontal measurement in measures which dip at 45 degrees. Nearby, in the Hare Moss and Auchencorth area thicknesses recorded do not exceed 3 ft 3 in.

In the Kirkettle–Lilyburn district the coal varies from 1 ft 10 in. to 3 ft 6 in. with a sandstone, fakes or fireclay floor and a roof of fireclay or fakes.

At Redside there are signs of old coal workings on the west side of the small burn 80 yd S.E. of Redside Farm which may have been in the Great Seam since the Gillespie coals are exposed a little farther downstream.

Between Halkerston and Fushiebridge coal thicknesses range from 3 ft 4 in. to 4 ft 6 in. As in the Newtongrange area the seam is here directly overlain by a thick sandstone. From Vogrie to Southside the range of thickness is from 3 ft 6 in. to 5 ft 10 in.

In Brosie Mains No. 1 Bore the Great Seam consisted of: coal; bright with splinty bands 6 in. on coal, bright and dull, banded 3 ft 9 in.

Interval between the Great and Rumbles coals

The interval between the Great and Rumbles coalsis 24 ft at Duddingston and 28 ft 6 in. in the Portobello railway cutting. At the latter locality the Great Seam is overlain by 8 ft of blaes, succeeded by 20 ft of sandstone, rooty in parts, with thin fakes partings. The intervening strata were 8 ft 9 in. thick in Monkton House No. 37 Bore and 13 ft in a crosscut mine in Gilmerton Colliery; at the latter place the Great Seam was overlain by 2 ft 6 in. of coaly blaes with an ironstone band, followed by 1 ft 3 in. of coal.

Near Loanhead and Roslin the Rumbles Coal lies 12 to 18 ft above the Great Seam, the intervening strata being fireclay, thin coals and sandstone.

In the southern areas the seams are from 2 to 8 ft apart, separated usually by fireclay.

On the east side of the coalfield the distance between the seams is generally about 25 ft, but in the old Cowden Colliery was 62 ft 2 in., being occupied almost entirely by sandstone.

Rumbles Coal (Rumbolds; Laverock of Duddingston; Dryden Gas; ?Johnstone or Waverley of Mauricewood; Mavis of Newtongrange and Cowden; Cryne of Vogrie).

In the Portobello railway cutting the Rumbles Coal is represented by two seams separated by 4 ft 4 in. of strata, the details being: coal 2 ft 2 in.; sandstone 4 ft; fireclay 4 in. on coal, bright, blocky 1 ft 6 in. Sections at other localities on the west side of the coalfield are: Monkton House No. 37 Bore: coal 2 ft 3 in.; fireclay, sandy, rooty 1 ft 2 in. on coal 1 ft. Gilmerton Colliery: coal 2 ft; fireclay 2 ft; coaly blaes 1 ft 6 in. on coal 1 ft. Gilmerton Diamond Bore: coal 1 ft 9 in.; sandstone 8 ft 9 in. on coal 1 ft 10 in.

At Loanhead also the coal occurs in two leaves. From 1 ft 9 in. to 4 ft 2 in. thick it was worked extensively between Burghlee and Roslin, mainly for the cannel, which was an important producer of gas, but also for the ironstone (Robertson in Macgregor and others 1920, p. 186). Ironstone is developed as bands in the coal in some places and forms the Rumbles Ironstone. The section of the seam in the Ramsay Pit 156-fm Crosscut Mine was: blaes with nodular ironstone bands, Lingula and fish remains; coal, hard, bright 1 ft 2 in.; cannel 1 in.; coal, bright with fusain plies 1 ft 1 in.; fireclay and sandstone 2 ft 1 in.; coal, bright 10 in.; coaly fireclay 2.5 in.; coal, hard, bright 7 in. on fakes and fireclay. A section at Burghlee is: blaes; coal, wild, parrot 1 ft 6 in. ironstone 9 in.; coal, gas 1 ft 8 in.; ironstone 7 in. on fakes. Fish remains are abundant in the roof of the coal or in the ironstone (p. 51). The identification of the Lingula recorded in the blaes 3 to 4 ft above the seam was made underground and must be regarded as tentative.

From Greenlaw to Penicuik House the coal varies from 1 ft 6 in. to 3 ft; at Mauricewood it appears to have been worked under the name of Johnstone Coal according to the mine plans and lies about 13 to 15 ft above the Great Seam. Here, however, the name Waverley seems also to have been used for it (Grant Wilson in Peach and others 1910, p. 211).

In the Kirkettle–Lilyburn area the Rumbles Coal lies close above the Great, the thickness ranging from 1 ft 6 in. to 2 ft 9 in. A split develops in places, the two leaves being up to about 5 ft apart. Fish remains have occasionally been recorded in the roof-shale. The pavement is a seatclay. A section in Kirkettle No. 11 Bore showed: blaes; coal 1 ft 7 in.; fireclay 1 ft 9 in.; coal 5 in.; fireclay 8 in.; coal 1 in.; fireclay 2 in.; coal 1 in. on fireclay and fakes. Elsewhere in the south of the coalfield the coal is thin or absent.

Between Vogrie and Southside and at Fushiebridge two coals are found at this horizon and are known as the Lower and Upper Mavis, separated by about 6 to 14 ft of seatearth and seatclay with an occasional bed of sandstone. The lower of the two varies from 0 to 2 ft 6 in. and the higher from 0 to 1 ft 6 in., though there is one doubtful record of 3 ft 3 in. The Upper Mavis has been replaced by limestone near the Vogrie Fault (p. 27). In the shaft at Vogrie (Old) No. 1 Pit the Rumbles is probably represented by a seam named 'Cryne' lying 5 fm above the Great Seam, but no details are known.

In the Vogrie–Newtongrange district the Rumbles Coal, known as the Mavis, is 2 ft 2 in. at the Emily Pit shaft and is separated from the Great by up to 60 ft of strata which are mainly sandstone. In the Lady Victoria Pit Shaft three coals were recorded at the horizon of the Rumbles aggregating 7 ft 3 in. of coal, but the record is suspect.

In the Southside area the Rumbles Coal is again split and the two seams, separated by about 20 ft of fakes and fireclay, are known as the Lower and Upper Mavis coals. Often one or the other is absent. The lower was 9 in. thick in Southside No. 199 Bore, and in Southside No. 989 Bore the upper was 1 ft 2 in. while the lower was missing.

In the old Cowden Colliery the Rumbles Coal consisted of a single seam 2 ft 8 in. thick, but in both Dalkeith Colliery and Carberry Colliery two seams were present at this horizon. The section in Dalkeith Colliery was: coal 1 ft 8 in.; sandstone 1 ft 6 in.; on coal 1 ft 3 in.; and in Carberry Colliery: coal 1 ft 2 in.; fireclay and fakes 5 ft 2 in. on coal 1 ft.

Measures between the Rumbles and Flex coals

The measures between the Rumbles and Flex coalswere 30 ft thick in the Duddingston area and 40 ft in Monkton House No. 37 Bore. They included, in the central part, a sandstone 16 ft thick. In a crosscut mine in Gilmerton Colliery the thickness of the intervening beds was 49 ft 6 in., as follows:

Between Loanhead and Roslin the Flex Coal is separated from the Rumbles by 35 to 50 ft of strata which include a coal up to 1 ft 5 in. thick, in the roof-shales of which Lingula was found, in addition to the possible record of Lingula in the roof of the Rumbles.

In Southside No. 989 Bore the distance between the Rumbles and Flex coals was 21 ft 9 in., the latter being directly overlain by 1 in. of carbonaceous blaes, succeeded by 2 in. of clayband ironstone and 3 ft of dark brown, slightly parroty blaes with irony plies.

In old Cowden Colliery the interval was 53 ft 6 in. and consisted mostly of sandstone, while in Carberry Colliery the separation was 32 ft and included a sandstone 14 ft thick.

Flex Coal (Cryne of Cowden)

The section of the Flex Coal in a crosscut mine at Gilmerton Colliery was : coal 2 ft; parrot 6 in. on coal 6 in. at Gilmerton Diamond Bore the details were: coal 5.5 in.; fakes 1.5 in. on coal 2 ft in.

The Flex Coal varies from 2 ft to 3 ft 11 in. between Loanhead and Roslin, the thinning being in a southward direction. It was described as a good rough coal and has been extensively worked. The Lingula band found here in the roof-blaes is a constant feature over the central and northern portions of the coalfield and has occasionally been recorded in the south. A section in the Ramsay Pit 156-fm Crosscut Mine gave: blaes with Lingula; coal, mainly bright 3 ft 9 in. on fireclay with ironstone balls.

The coal correlated with the Flex in the south-west between Roslin and Penicuik varies from 2 ft to 2 ft 6 in. in thickness. Formerly (Grant Wilson in Peach and others 1910, p. 211) a coal at Mauricewood, 4 ft thick and lying 59 ft 6 in. above the Union (Great), was named the Johnstone Coal. This seam is on the horizon at which the Flex would be expected, though the thickness seems unduly great. It is not the Johnstone Coal of the mine-plans. In the rest of the southern area the Flex is thin or absent.

Near Newtongrange the Flex Coal has the name Cryne Coal and between here and Vogrie is 2 ft 1 in. to 2 ft 6 in. thick, but between Vogrie and Southside it does not exceed 1 ft to 1 ft 11 in. and is not known to have been worked except to a small extent in the opencast site of Southside.

A section of the Cryne in Southside No. 989 Bore reads: parroty blaes partly pyritized with Lingula and fish fragments 1 in.; coal 2 ft on sandy fireclay.

Farther north the following section was seen in Dalkeith Collieries: coal 1 ft 3 in.; coaly fireclay 1 ft 3 in. on coal with much blaes 1 ft 9 in.

In the Prestonlinks No. 36 Underground Bore a seam, 1 ft 3 in. thick, occurred 34 ft above the Great Seam and was directly overlain by 1 ft 3 in. of blaes with fragments of Lingula. It is likely to be on the horizon of the Flex Coal.

Measures between the Flex Coal and the Index Limestone

The measures between the Flex Coal and the Index Limestoneproved to be 70 ft 10 in. thick in Monkton House No. 37 Bore and were made up as follows:

In a crosscut in Gilmerton Colliery the thickness was 114 ft and there the Flex Coal was immediately overlain by 3 in. of parroty blaes with Lingula and fish scales, succeeded by a sandstone 54 ft thick, coarse at the base and finer towards the top.

Geordie Coal

In the Loanhead ground a seam, the Geordie Coal, is between 18 and 39 ft above the Flex Coal, separated by strata which include two thin coals. It varies from a maximum of 3 ft 4 in., is subject to washouts and is also split by partings. It has been wrought at Roslin where the section recorded in the No. 1 or Splint Mine was: fireclay with ironstone balls; coal, bright, banded 2 ft 2 in.; coaly fireclay 1 ft on fireclay with ironstone balls.

At Greenlaw the Geordie seam is from 2 ft 6 in. to 2 ft 7 in. thick but elsewhere to the south it is unimportant or absent.

Along the eastern outcrop of the coalfield the measures between the Flex Coal and the Index Limestone include the Deception Coal, perhaps the equivalent of the Geordie Seam. Between Vogrie and Newtongrange it is from 1 ft 7 in. to 2 ft 6 in. thick, though in the Southside direction it does not exceed 1 ft 3 in. and is separated from the Flex by strata which include a 6-in. coal. The same strata include a thin blackband ironstone at Lady Victoria Pit, at which colliery, however, the sequence is not clear and the exact correlation of the Geordie uncertain.

At Southside No. 216 Bore the Deception Coal lay 17 ft 5 in. above the Flex Coal. The latter was directly overlain by 3 in. of parroty and pyritous blaes with fish remains and Lingula. The Deception Coal itself was 1 ft 6 in. thick and consisted of bright and dull coal with layers of cannel.

In Dalkeith Colliery the section of the Deception Coal was: coal 1 ft 3 in.; dirt 7 in. on coal 6 in. and the strata between that seam and the Flex were about 26 ft thick, including a thin coal, mostly parrot, with a 4-in. parting of ironstone containing fish remains. The Deception Coal was 1 ft 9 in. thick in Carberry Colliery and lay 24 ft 9 in. above the Flex.

Between the Geordie Coal and the Index Limestone near Loanhead there is a sandstone 80 ft thick, which, however, has completely thinned out at Roslin (Plate 3). Above this a thin coal and fireclay lie about 12 ft below the Index Limestone, separated from it by blaes with thin ironstone nodules and ribs, succeeded by sandstone. A streak of coal, 1 to 3 in. thick, is found a few inches below the base of the Index Limestone.

In the south the thin coal and blaes with ironstone are usually recognizable, the coal here lying about 6 to 10 ft below the limestone.

In Roslin Colliery the return airway between Nos. 1 and 2 mines showed 1 ft of silty mudstone immediately below the Index Limestone. This band yielded Orthotetid indet., Rhynchonellid fragments, Aviculopecten sp., Myalina sp., Prothyris sp., Sanguinolites sp., Solenomorpha?, Streblopteria ornata (R. Etheridge jun.), Euphemites sp.and a Loxonematid indet.

A bed of grey mudstone with ironstone balls, 1 ft 6 in. thick, but not bottomed, occurs in Silver Burn below the road-bridge in Penicuik policies, 390 yd N. 40° E. of the north-eastern corner of Penicuik House. It lies just below the Index Limestone though the junction is not visible, and yielded Lingula mytilloides J. Sowerby, Schellwienella sp., Nuculana attenuata (Fleming) and Posidonia?.

Strata underlying a limestone thought to be the Index are exposed on the banks of the River North Esk, south-south-east of the ruins of Penicuik House. In the left bank, 455 yd S. 15° E. of the House the limestone rests on a 6-in. faky band with Stenoscisma sp., Myalina?, Palaeolima? and a trilobite pygidiurn. Underlying this band is about 1 ft of grey faky blaes with Stenoscisma?, Aviculopecten?, Cardiomorpha?, ?Edmondia sulcata (Phillips), ? Nuculopsis gibbosa (Fleming), indeterminate Pectinids, Prothyris sp., Sanguinolites cf. striatus Hind and Solenomorpha parallels? (Hind).

On the right bank, about 100 yd upstream, a section is seen which includes strata slightly lower in the succession:

References

ALLAN, J. K., and KNOX, J. 1934. The Economic Geology of the Fife Coalfields. Area II. Mem. Geol. Surv.

EWING, C. J. C., and FRANCIS, E. H. Nos. 1 and 2 Off-shore Borings in the Firth of Forth (1955–56). Bull. Geol. Sum. Gt. Brit. (In the press).

FRANCIS, E. H. 1956. The Economic Geology of the Stirling and Clackmannan Coalfield, Scotland. Area north of the River Forth. Coalfield Papers: Geol. Sum. Gt. Brit. No. 1.

HALDANE, D., and ALLAN, J. K. 1931. The Economic Geology of the Fife Coalfields. Area I. Mem. Geol. Surv.

HOWELL, H. H., and GEIKIE, A. 1861. The Geology of the Neighbourhood of Edinburgh. Mem. Geol. Surv.

MACGREGOR, M. 1937. In Sum. Prog. Geol. Sun. for 1936, pt. 1.

MACGREGOR, M. 1938. In Sum. Prog. Geol. Surv. for 1937, pt. 1.

MACGREGOR, M., LEE, G. W., and WILSON, G. V. 1920. The Iron Ores of Scotland. Geol. Surv., Min. Resources, 11.

MILNE, D. 1839. On the Mid-Lothian and East-Lothian Coal-Fields. Trans. Roy. Soc. Edin., 14, 253–358. Published separately with additions 1839, Edinburgh. MITCHELL, G. H. 1955. In Sum. Prog. Geol. Sum. for 1954,43–5.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Sum.

TRAQUAIR, R. H. 1903. On the Distribution of Fossil Fish-remains in the Carboniferous Rocks of the Edinburgh District. Trans. Roy. Soc. Edin., 40, 687–707.

WILSON, W., CLOUGH, C. T., LEE, G. W., and TAIT, D. 1909. The Recently Exposed. Section on the Railway Line, South-East of Portobello, with Comparisons. Trans. Edin. Geol. Soc., 9, 193–201.

Chapter 5 Upper Limestone Group

General account

The Upper Limestone Group includes the strata between the base of the Index Limestone and the top of the Castlecary Limestone. The latter limestone is known to be present in the north-west part of the coalfield, in the region from Joppa southwards to the Bilston Burn, but all the available evidence indicates that in most of the Penicuik Syncline and along the eastern outcrop of the Upper Limestone Group the Castlecary Limestone is absent (Plate 4), and a conjectural position for the top of the group has therefore been chosen in the southern and eastern regions. The variations in thickness of the group are shown on (Figure 13).

Lithological characters

The Upper Limestone Group contains several thick sandstones and a considerable proportion of shales, sandy shales and shaly sandstones. There are four principal limestone horizons, in upward succession the Index Limestone, the Orchard Beds, the Calmy Limestone and the Castlecary Limestone. In this memoir the Orchard Beds, which are approximately in the same stratigraphical position as the Lower and Upper Orchard limestones of the Glasgow district (E. M. Anderson in Clough and others 1925, p. 71), are defined as the strata in the Bilston Burn between the top of the coal which is 384 ft above the Index Limestone (Plate 4) and the top of the 10-in. crinoidal and shelly sandstone 76 ft above this coal. The details of the Bilston Burn section are given on pp. 67–68. Three of the limestones in the Upper Limestone Group were formerly identified by numbers, No. 4 being the Index, No. 5 the Calmy and No. 6 the Castlecary (Howell in Howell and Geikie 1861, p. 73), and the Orchard Beds, or part of them, have in the past been referred to as the 'Extra' Limestone (Peach and others 1910). The Index, Calory and Castlecary limestones are all rather impure, sometimes dolomitic, and have not been worked to any extent. In addition to the four main marine horizons there are, in other parts of the succession, beds of shale with marine fossils, in places associated with thin, often lenticular limestones, including what appear to be representatives of the Huntershill Cementstone and Lyoncross Limestone. Several coal seams are present, the most important being the South Parrot and the Wood (Plate 4). The former has been worked at certain localities on the west side of the basin including the Niddrie area, and is at present worked at Roslin and Loanhead under the name of South Parrot Splint.

Outcrop

Theupper part of the group is exposed on the shore at Joppa, on the west side of the coalfield; from there the outcrop extends in a south-southwesterly direction by way of Woolmet towards Gilmerton station. About half a mile south of the station the strata are displaced by the Sheriffhall Fault (Figure 18) and south of the fault the general line of strike is south-westerly. The outcrop of the group extends through the eastern part of Loanhead and passes just west of Roslin and Penicuik.

Between Penicuik and Auchencorth the beds are affected by minor folds. The details of the Upper Limestone Group in this area are derived mainly from a series of old borings, one of which dates back to 1866 (Plate 4); in some of these the borer's description of parts of the succession may be incorrect and most of the thin fossiliferous bands which are found elsewhere in the coalfield are unrecorded.

To the south of Auchencorth the exact extent of the outcrop is uncertain, but so far as is known the southern limit is in the region of Whim House.

On the eastern side of the Penicuik Syncline (Figure 18) the positions of the upper and lower limits of the Upper Limestone Group are again uncertain but from just west of Leadburn to a point about 500 yd W. of Howgate (Figure 4) the eastern limit of the outcrop is formed by a north-easterly trending fault. Farther to the north-east the Leadburn Fault, with a similar trend, limits the outcrop for most of the way between Upper Firth and Newbigging.

Three outliers of the Upper Limestone Group occur in the region between Newbigging and Harvieston. The most westerly of these is situated on the south-west side of the Vogrie Fault, south-west of Shewington Farm; another is present in the north part of Cauldhall Moor; the third, forming the small faulted Halkerston Syncline, lies about a quarter of a mile north-east of Halkerston Farm.

On the east side of the coalfield the outcrop of the Upper Limestone Group, displaced by several faults, runs in a northerly direction from Harvieston Mains to Newtongrange, and from there in a north-north-easterly direction, again somewhat displaced by faults, particularly by one at Smeaton Shaw, to just north of Wallyford. Thereabouts it swings eastwards, but the north-north-easterly strike is resumed on the shore at Cuthill.

Details

Index Limestone

The thickness of the Index Limestone at various localities is indicated on (Plate 4). The section seen in Monkton House No. 37 Bore showed dark grey crinoidal limestone 3 ft 1 in. thick, earthy at top and bottom, with large shells in the lower part. The limestone was overlain by blaes containing marine fossils, including Posidonia sp.(juv.) and Bucanopsis sp.Orthotetid and Productid fragments and ? Streblopteria ornata (R. Etheridge jun.) have been found in blaes above the Index Limestone in the Bilston Burn. In the Millstone Grit Mine, Gilmerton Colliery, the Index Limestone occurred in two beds: limestone 1 ft 10 in.; blaes, grey, faky 6 in. on limestone, grey, earthy, encrinital 2 ft 2 in. A hard, crinoidal, shelly limestone 3 to 4 ft thick, taken as the Index, is seen in the Silver Burn, just below the road bridge in Penicuik policies, and 390 yd N. 40° E. of the north-east corner of the ruins of Penicuik House. Just under half a mile to the south-south-west, a nodular limestone about 4 ft thick, ochreous in parts, with a band of P. (Gigantoproductus) sp.(latissimoid) 18 in. from the base, crops out on both banks of the River North Esk; this bed has been mapped as the Index Limestone, but the identification is not absolutely certain (p. 81). In Hare Moss No. 130 Bore the limestone occurred in two beds, as follows: limestone, pale grey, earthy, shelly, with a 3-in. limy fakes band in the middle, 2 ft; blaes, pale grey, poorly bedded, with scarce encrinites 2 ft 3 in.; fireclay 9 in.; limestone, ochreous, 6 in. on limestone, hard, compact, with occasional fragments of shells 5 ft.

In Newbigging No. 16 Bore, put down about two and three-quarter miles east of Penicuik, the Index Limestone was represented by 9 in. of brown, ochreous, decomposed limestone, with encrinite fragments. The poor development of the limestone is probably due partly to decalcification and partly to erosion prior to the deposition of the sandstone which immediately overlies it. The Index Limestone was absent in two bores put down about a quarter of a mile farther south; in one of these, Cauldhall Moor No. 46 Bore, a bed of blaes 9 ft 10 in. thick, with small red irony balls, overlain by sandstone, has been interpreted as the stratum immediately underlying the limestone, the absence of the limestone being attributed to erosion.

In the Halkerston area the Index Limestone was found to be 2 ft 3 in. thick and was composed of hard, ochreous weathering, pale grey, sandy limestone. In the Southside region the Index Limestone was passed through in Sauchenside No. 9 Bore; the total thickness was 4 ft 8 in., being subdivided as follows: limestone, decalcified, shelly 8 in.; limestone, hard, grey, crystalline, shelly 2 ft 6 in.; limestone, impure, fossiliferous 9 in. on limestone, hard, compact, grey, with shell-debris 8 in. These beds were overlain by 17 ft of fakes with irregular ironstone balls in the lower part, succeeded by 22 ft of fine-grained sandstone.

The lower part of the Index Limestone is exposed in the Gore Water, a little above the bridge at Goiebridge. The top, formerly seen but now obscured, was said to be characterized by numerous Productus latissimus (Clough and Crampton in Peach and others 1910, p. 241), but the part of the limestone now exposed contains few fossils; Chaetetes sp.and a fragment of Productus (Gigantoproductus) latissimus? J. Sowerby have been found. In Prestonlinks No. 36 Underground Bore the limestone was brownish grey, compact, shelly and encrinital, with small dark patches, and the lower 6 in. was argillaceous. Orthotetids and Nuculana attenuata (Fleming) have been recorded in the beds overlying the Index Limestone in an underground bore about half a mile to the south-south-west.

Index Limestone to Orchard Beds

Measures between the Index Limestone and the South Parrot Coal

The thickness of the measures between the Index Limestone and the South Parrot Coalvaries from 119 ft at Niddrie to 85 ft at Southside.

Two marine shell-beds are known in this range of strata, and several thin coals are generally present (Plate 4). The section in Bilston Burn is as follows:

The thick sandstone between the Index Limestone and the South Parrot Coal probably corresponds to the Bishopbriggs Sandstone of the Glasgow district. It was formerly quarried near Joppa and is known as the Joppa Sandstone.

The marine measures which, in the Bilston Burn, occur 42 ft 3 in. to 49 ft 8 in. above the top of the Index Limestone, are thought to include beds corresponding to the Huntershill Cementstone, which overlies the Bishopbriggs Sandstone at Bishopbriggs. They probably also include, however, measures which may be on the same horizon as the shelly limestone found in the middle of the sandstone at Bishopbriggs (L. W. Hinxman in Clough and others 1925, pp. 76, 77). Two marine shell-beds were also found in No. 1 Mine to the South Parrot Coal in Roslin Colliery, the details of the fossiliferous beds and the intervening strata being:

In the Penicuik area the shale with ironstone balls which generally succeeds the Index Limestone is sometimes limy in its upper part and thin ribs of limestone are occasionally present. The remainder of the interval includes shale, sandy shale and shaly sandstone, with sandstone posts which are of considerable thickness in certain areas.

Above the limestone mapped as the Index in Silver Burn (p. 63) more than 20 ft of sandstone, sometimes faky and with fakes bands, overlies 6 ft of micaceous fakes and faky blaes. A gap of about 3 ft separates this bed from the Index Limestone below, a 1-in. band of shelly silty mudstone immediately above the limestone yielding Orthotetid and Rhynchonellid fragments and a Pleurotomariid.

About half a mile to the south-south-west, on the right bank of the River North Esk 515 yd S. 6° E. of the south-west corner of Penicuik House the limestone mapped as the Index (p. 63) is overlain by at least 1 ft 6 in. of grey blaes, containing Orbiculoidea sp., Schellwienella sp., and Posidonia sp.

Grey fakes and faky blaes, 3 ft 4 in. thick, on the horizon of the Huntershill Cementstone were found in a crosscut at Roslin Colliery approximately 37 ft above the Index Limestone. The only identifiable fossils were Orthotetids and Prothyris sp.

The Huntershill Cementstone (p. 64) was represented in Hare Moss No. 130 Bore by 1 ft 9 in. of sandy fakes with disturbed bedding, containing Lingula and fish scales.

About 6 ft of blaes overlying the Index Limestone are exposed on the left bank of the Gore Water, about 260 yd upstream from the road bridge at Gorebridge.

In the shaft of the Lady Victoria Pit the Index Limestone is overlain by blaes and faky blaes, passing upwards into fakes, succeeded by a sandstone 84 ft thick. The corresponding sandstone was about 50 ft thick in Prestonlinks No. 36 Underground Bore, and was overlain by 1 ft of sandy fireclay and 4 in. of coal, succeeded by 8 in. of blaes containing Lingula.

South Parrot Coal (South Parrot Splint of Loanhead)

In a crosscut in Niddrie No. 13 Pit the section was: coal, splint, 1 ft 10 in. on coal, parrot, 1 ft, and the details as formerly seen at Edgefield were: coal, parrot 1 ft 3 in. on coal, free, 10 in. In the Mavisbank level of the Ramsay Pit the seam consisted of 1 ft 4 in. of splint coal on 5 in. of parrot coal, underlain by 1 ft 3 in. of rough coal. As the seam is followed southwards and south-eastwards the parrot disappears and a section in the Ramsay Pit level crosscut at 275-fm showed: coal, mostly durain 1 ft 6 in. on coal, mostly clarain, 1 ft 3 in.

In Sauchenside No. 26 Bore, near Southside, the seam was 1 ft 6 in. thick. Farther north, in the Emily Pit shaft the section was: coal, splint 1 ft 7 in., and in Prestonlinks No. 36 Underground Bore the details were: coal 1 ft; blaes 2 in.; coal 6 in.; blaes 1 in. on coal 1 ft.

Beds between the South Parrot Coal and the base of the Orchard Beds

The thickness of the beds between the South Parrot Coal and the base of the Orchard Beds varies from 313 ft at Gilmerton Colliery to 164 ft at Southside.

Thick sandstones, often coarse and gritty, occur in this part of the succession in the Niddrie railway cutting, and at other localities two marine shell-beds and several Lingula beds have been found (Plate 4). In addition, Lingula was collected immediately above the South Parrot Coal in Niddrie Collieries by Traquair (1905, p. 696). A thick bed of blaes occurs between the South Parrot Coal and the lower marine bed in many parts of the coalfield. The lower of the two marine bands was found 86 ft 9 in. above the South Parrot Coal in the Roslin Colliery No. 1 or Splint Mine, the intervening strata including sandstone, sandy fakes and fireclay, with thin coal seams. The details of the shell-bed and the associated strata are: faky blaes with irony bands and occasional ironstone nodules, Lingula and Streblopteria ornata (R. Etheridge jun.) 1 ft; faky blaes and blaes, with occasional ironstone balls and irony bands 4 ft 6 in.; coal, bright 6 in. on coal, with black fireclay bands 5 in.

In the Monkton House Bore this horizon was represented by a 13-in. band of grey fakes with scraps of Lingula, found about 74 ft above the South Parrot Coal (Plate 4).

The upper marine band, which represents the Lyoncross Limestone, crops out in the Bilston Burn where the succession was: fakes with irregular ironstone bands and nodules containing marine fossils including Lingula mytilloides J. Sowerby, Productus (Buxtonia) sp., Nuculana attenuata (Fleming), Palaeoneilo laevirostris? (Portlock) and Euphemites urei (Fleming) aff. mut. ardenensis (Weir) 2ft 6 in.; fakes with large limestone nodules showing cone-in-cone structure 1 ft 6 in.; sandy fakes 1 ft 4 in. on coal 2 in. The 2-in. coal lies about 157 ft above the waste of the South Parrot Coal.

The Lyoncross Limestone was also found in the Roslin Colliery No. 1 or Splint Mine, where it lay about 28 ft above the marine band (see above). The succession was as follows:

In the Monkton House Bore the Lyoncross Limestone was represented by 2 ft of faky blaes containing poorly preserved shells.

Measures between the Lyoncross Limestone and the Orchard Beds

The measures between the Lyoncross Limestone and the Orchard Bedsvary considerably from place to place, and though consisting mainly of sandstone, sandy fakes and fakes, with fireclay and thin coat seams, they also include beds of blaes, some of which are fossiliferous. In the Monkton House Bore a Lingula band was recorded 95 ft above the position of the Lyoncross Limestone, and about 16 ft higher up a bed of blaes 2 ft 2 in. thick contained fragments of poorly preserved shells. Three Lingula bands were recorded in the Bilston Burn. The lowest, some 6 ft above the Lyoncross Limestone, consisted of 6 in. of carbonaceous faky blaes with Lingula and fish scales. About 81 ft of strata, including a 34-ft sandstone, separated this band from the succeeding marine blaes, 5 ft 4 in. thick with numerous Lingula and fish scales. About 27 ft higher up, a 1 ft 6 in. band of blaes was noted, with Lingula and small lamellibranchs. About 7 ft 7 in. below the middle of these three Lingula bands a poor, splinty coal, 9 in. thick, was found, immediately overlain by 2 in. of carbonaceous blaes, with plant remains and fragments of ? Lingula.

In the No. 1 or Splint Mine at Roslin Colliery a 6-in. bed of hard, dark irony blaes with Lingula and fish scales occurred about 60 ft above the Lyoncross Limestone.

Owing to lateral variation it is difficult to correlate these Lingula bands from one locality to another, but it appears that the two fossiliferous horizons, found in the Monkton House Bore 16 ft apart (shown as one band on (Plate 4)), correspond to the two upper Lingula bands of the Bilston Burn succession.

Strata including beds tentatively correlated with the Lyoncross limestone and the Orchard Beds were passed through in Halkerston No. 440 Bore, the details of the presumed Lyoncross Limestone and its associated strata as recorded by the borer being: limy fakes 1 ft 3 in.; fakes 9 in.; faky fireclay 1 ft 6 in.; limestone 1 ft 6 in.; faky fireclay 3 ft 6 in. on limy fakes 2 ft 6 in.

In some localities a thin coal is found immediately below the Orchard Beds; a coal 1 ft thick, composed mainly of cannel with some coaly blaes, was seen in the Bilston Burn, and in the Roslin Colliery No. 1 Mine the seam had the following section: coal, splinty, with bright layers 8 in. on coal, inferior, parroty 6 in.

On the east side of the coalfield the South Parrot Coal and the Orchard Beds are separated by strata including fakes, faky blaes and blaes, with seatclays and thin coals; there are also several sandstones which, in the Newtongrange–Cowden area are of considerable thickness. In the Prestonlinks Underground Bore a thin rib of carbonaceous blaes containing Lingula and fish remains was recorded 164 ft above the Index Limestone, and 15 ft higher in the succession there was a 1 ft 8 in. bed of grey fakes and faky blaes with pale brown decalcified limestone balls and patches. The latter contained fragments of crinoid columnals and marine shells, and probably marks the position of the Lyoncross Limestone.

Orchard Beds

The best development of the Orchard Beds is found in the Bilston Burn, and the details of the section there are given on pp. 67–68.

In the Monkton House Bore the Orchard Beds were almost 50 ft thick, the details being:

In this bore it was necessary to fix an estimated position for the upper limit of the Orchard Beds since the crinoidal and shelly sandstone, which marks the top of these beds in the Bilston Burn, was not found.

In the Millstone Grit Mine at Gilmerton Colliery the upper part of the Orchard Beds appears to be absent, probably owing to erosion. The development is similar to that found in the Monkton House Bore, but a greater proportion of impure limestone was recorded, as follows:

In the Bilston Burn the Orchard Beds are just over 76 ft thick. The section given below is composite, being compiled from exposures at three localities, namely Bilston Burn, 60 yd downstream from the railway viaduct south of Loanhead; Bilston Burn, 130 yd downstream from the junction between the Bilston Burn and the Kill Burn; Kill Burn, 60 yd upstream from its junction with the Bilston Burn:

The following fossils have been obtained from the bottom 4 ft of the above section: Crinoid columnals, Camarotoechia? Composita cf. ambigua, Lingula mytilloides, Orthotetid fragments, Productus (Dietyoclostus)cf. muricatus, P. (Dictyoclostus)pugilis? Phillips, P. (Eomargintlera) aff. longispinus (J. Sowerby), P. (Gigantoproductus) cf. latissimus (very broad, much inrolled form; very abundant in a bed about 2 ft above the base of the section), P. (Productus) cf. carbonarius, Schizophoria resupinata (Martin), Spirifer cf. trigonalis (Martin), Aviculopecten cf. interstitialis (Phillips), A.? cf. scoticus, Cypricardella rectangularis (McCoy), Nuculana attenuata, Nuculopsis gibbosa (Fleming), Parallelodon semicostatus? (McCoy), Pernopecten sp.,? Promytilus megaloba (McCoy), Sanguinolites striatolamellosus de Koninck, Schizodus sp. (juv.), Bucanopsis decussatus (Fleming), Euphemites urei cf. mut. ardenensis and Glabrocingulum armstrongi E. G. Thomas.

Bores in the Penicuik region indicate that there is considerable variation in the Orchard Beds (Plate 4); this may, however, be partly due to inaccurate identification of strata.

Several exposures of parts of the Orchard Beds occur in the area north-east and east of Penicuik. A hard, brown-weathering, limy sandstone at least 3 ft thick, and formerly regarded as the Castlecary Limestone, crops out 700 yd N. 8° W. of Firth Mains Farm, in the stream which flows past Firth House; crinoid columnals, Productus (Buxtonia) sp., P. (Productus) cf. carbonarius, a Productid indet. (Echinoconchus?) and Spirifer cf. bisulcatus J. de C. Sowerby have been found in this bed. In the right bank of the stream 465 yd S.W. of Firth Mains Farm the following section is seen:

About a mile farther west, on the right and left banks of the River North Esk, 360 yd E. of Valleyfield Paper Mills, and 660 yd N. 10° W. of Pomathorn station, the details of the section are:

These beds were formerly thought to include the Calmy Limestone.

About 40 yd downstream strata which probably belong to the basal part of the Orchard Beds are seen:

About three-quarters of a mile west of Penicuik, in a gully on the right bank of the Loan Burn, 170 yd N. 31° E. of Spear Gate Lodge, strata thought to be part of the Orchard Beds are seen, the details being:

About 40 yd upstream in the Loan Burn the following beds crop out:

The beds in the gully are thought to be separated from those in the burn by a fault. It is possible that the strata in the burn form part of the Orchard Beds, higher in the succession than those in the gully. In this case the fault is small and the gap between the two exposures includes about 7 ft of strata. On the other hand the fauna from the exposure in the burn bears a resemblance to faunas found at the horizon of the Calmy Limestone in other parts of the area, and the fault may be fairly large.

About 630 yd to the south-south-west, in the Silver Burn, 560 yd N.E. of Penicuik House, part of the Orchard Beds are exposed, as follows:

The above beds were formerly thought to include the Index Limestone.

About 3 ft of flaggy sandy limestone with ? Edmondia sulcata crops out on the left bank of the River North Esk, 530 yd E. 10° N. of Penicuik House; this bed has been mapped as part of the Orchard Beds, but the correlation is uncertain.

The greater part of the Orchard Beds crops out just under half a mile to the south-south-west, in a small stream on the right bank of the River North Esk, 500 yd S. 30° E. of Penicuik House:

A condensed development of the Orchard Beds is found in the Cornton Burn, about 70 yd N.N.E. of Cornton Farm:

To the south-west of Brunston Castle the beds are thrown into a series of gentle folds, and part of the Orchard Beds, brought up by one of these folds, is seen in a small stream that falls into the Esk, 240 yd E. 36° N. of Auchencorth Farm:

The top beds of the above section are also exposed on the steep left bank of the River North Esk, 300 yd N. 18° W. of Auchencorth Farm, where over 3 ft of fine-grained dolomitic limestone with ochreous patches is seen resting on about 1 ft 8 in. of hard calcareous mudstone with crinoid columnals, finely comminuted brachiopod and shell fragments and poorly preserved ostracods. About 500 yd N. 20° E. of Auchencorth Farm there is an outcrop of dolomitic limestone containing a large patch packed with corals, including Dibunophyllum linnense Hill, and abundant Clisiophyllid corals, which is probably in the basal part of the Orchard Beds.

The strata exposed at the last three localities were formerly thought to include the Calmy Limestone.

The Orchard Beds were passed through in Arniston Mains Nos. 1 and 2 bores (Plate 4); the details of the borer's log for that part of the succession in No. 1 Bore are as follows:

The 10-in. impure limestone at the top of this section possibly corresponds to the thin sandy limestone near the top of the Orchard Beds in the Bilston Burn.

Part of the Orchard Beds is exposed in the Gore Water, about 900 yd N.W. of Harvieston Mains Farm; the succession, formerly considered to include the Calmy Limestone, is as follows:

Three beds of limestone, with shale partings between, were formerly exposed on the shore at Cuthill Rocks, north of Preston Grange House; these strata were, until recently, thought to represent the Calmy Limestone, but a re-examination of the fauna indicates that they are part of the Orchard Beds. The fossils recorded are a Clisiophyllid coral, crinoid columnals, an echinoid spine, a Fenestellid, an encrusting polyzoan (on coral), a Chonetid, Lingula mytilloides, fragments of Orthotetids, Productus (Dictyoclostus) aff. pugilis, P. (Eomarginifera) aff. longispinus, P. (Linoproductus) sp., Aviculopecten? cf. scoticus, Wucula' oblonga Hind non McCoy, Nuculana attenuata, Parallelodon aff. semicostatus, Schizodus sp.(juv .), Streblochondria? cf. elliptica, Bellerophon sp., Euphemites sp.and a pygidium and part of a cephalon of Weberides cf. mucronatus.

During a pit-sinking at the Tileworks, Morrisonshaven, Prestongrange, one and three-quarter miles east-north-east of Musselburgh, the following section was exposed: limestone 1 ft; shale 3 ft; limestone 1 ft on shale 10 to 12 ft.

The fossils listed below were collected from the shale and suggest that these strata belong to the Orchard Beds: a crinoid calyx and columnals, a fragment of a Chonetid, Productus (Dictyoclostus) aff. muricatus, P. (Gigantoproductus)cf. latissimus, P. (Linoproductus) sp., Aviculopecten? cf. scoticus, Pernopecten?, Schizodus cf. wheeleri (Swallow), Streblochondria? cf. elliptica, and parts of the cephalon and thorax of a trilobite.

The Orchard Beds at Prestonlinks Colliery are shown on (Plate 4). A good section of these strata, from which fossils were collected, was obtained in an up-bore in the workings of the same colliery. This bore, which was situated about two and a half miles N. 17° E. of Prestongrange Colliery, showed :

The fauna in the last three items includes bryozoa, Lingula sp., numerous Productus (Gigantoproductus)cf. latissimus (broad, inrolled form) and Schizophoria sp.

Orchard Beds to Calmy Limestone

The thickness of strata intervening between the Orchard Beds, and the Calmy Limestone is from 255 ft (Niddrie) to 138 ft (Arniston).

In the Monkton House Bore the Orchard Beds are succeeded by fakes and sandy fakes, overlain by sandstone. A white, reddish and purplish sandstone, over 96 ft thick, with a 3-in. band of fakes near the centre, was seen in the Millstone Grit Mine at Gilmerton Colliery, resting directly on the Orchard Beds; the upper part of these beds seems to have been removed by erosion before the deposition of the sandstone.

In Arniston Mains No. 1 Bore the Orchard Beds were overlain by fakes, passing upwards into a sandstone about 48 ft thick, and a thick sandstone in the same strati-graphical position was passed through in Anniston Mains No. 2 Bore, where it was overlain by about 20 ft of fakes and sandstone, with a coal 1 ft 2 in. thick, which probably corresponds to the Wood Coal of the west side of the coalfield. The strata between this coal and the Calmy Limestone were found to include fakes, faky sandstone, and blaes, with a thick sandstone in the upper part; about 16 ft above the coal a bed of blaes, over 20 ft thick, was passed through. This bed is in the same stratigraphical position as that in which Edmondia punctatella occurs in the Bilston Burn and elsewhere in Midlothian.

Wood Coal

The Wood Coal, which was formerly worked in the Duddingston area, occurs about 140 ft above the top of the Orchard Beds in the Niddrie railway cutting; in the Bilston Burn the interval between the coal and the Orchard Beds is 75 ft. In Drydenbank No. 6 Bore, just north of the Bilston Burn, the Wood Coal and an underlying seam were passed through; the recorded thicknesses of the coals and the intervening strata were exaggerated owing to the steep dip of the strata, and the following is an approximate section, corrected for dip:

Between the Wood Coal and the Calmy Limestone

Between the Wood Coal and the Calmy Limestone several fossiliferous horizons have been found, and the lowest of these, which contains Edmondia punctatella (Jones), is of widespread occurrence (Plate 4). It is everywhere underlain by a thin, incompetent bed of shale, invariably crushed and full of polished surfaces.

A Lingula band, which was found in the Monkton House Bore about 22 ft below the Calmy Limestone, probably corresponds to the middle marine band of the Bilston Burn succession. The topmost horizon, a marine shell-bed which lies 6 to 12 ft below the Calmy Limestone in the Joppa–Bilston Burn area, has been recorded at many other localities on the western side of the main syncline and in the Penicuik region.

The details of the strata between the Wood Coal and the Calmy Limestone on the Joppa shore were:

The succession in the Millstone Grit Mine at Gilmerton was similar to that at Joppa. Edmondia punctatella was found in grey blaes about 50 ft above the Wood Coal, and a bed of blaes with ironstone balls about 6 ft below the Calmy Limestone contained the following fauna: crinoid columnals, Conchotrema sp.(burrows in gastropod), Sphenothallus [Serpulites] sp., Cardiomorpha cf. limosa, Edmondia sulcata?, Myalina sp., Nuculana cf. laevistriata, Prothyris cf. elegans, Sanguinolites cf. striatus, S. sp. nov.(variabilis McCoy-omalianus (de Koninck) group), Bucanopsis sp., Donaldina sp., and Euphemites sp.

In the Bilston Burn the interval between the Wood Coal and the Calmy Limestone is less than at Niddrie and Gilmerton, and the proportion of sandstone and fakes between the Edmondia Band and the Calmy Limestone is also less. The details of the Bilston Burn succession are:

It is interesting to note that, in the Midlothian Coalfield, E. punctatella occurs in association with marine fossils in poorly bedded grey blaes (silty mudstone) and not, as in many other areas in Scotland, in a low-grade oil-shale (Drop 1910, p. 394; Haldane 1925).

In the Penicuik region the Wood Coal is not known for certain; the strata between the Orchard Beds and the Calmy Limestone include thick sandstones, with sandy shales, shales and occasional coal seams. The marine bands, including the Edmondia punctatella Band, were not recognized in the sections given in (Plate 4), but are known elsewhere in the neighbourhood. Two coals, the upper 16 in. and the lower 12 in. thick, are seen in the Hare Burn, half a mile south of Penicuik House; the lower seam was formerly thought to be the South Parrot Coal.

The strata underlying the Calmy Limestone crop out in a small stream on the right bank of the River North Esk, 500 yd S. 44° E. of Penicuik House:

The beds immediately underlying the Calmy Limestone are exposed on the left bank of the River North Esk, at the bend 500 yd E. 11° S. of the south corner of Brunston Farm, the details being:

A poor development of the same strata is seen in the Black Burn, below the bridge at Dykeneuk, just over one and a quarter miles south of Penicuik, where the Calmy Limestone rests on 5 ft of blaes with ironstone balls, containing Lingula sp., Actinopteria? cf. persulcata, Edmondia punctatella, Myalina cf. peralata de Koninck, and Sanguinolites cf. clavatus.

In a small stream 280 yd downstream from Auchendinny Mains Farm a grey sulphurous-weathering mudstone has been found, containing the following fauna which is typical of the lamellibranch bed underlying the Calmy Limestone: Lingula mytilloides, Orbiculoidea sp., Cardiomorpha cf. limosa, Nuculana laevistriata, Prothyris? and Sanguinolites cf. striatus. About 8 ft of strata separate the base of this bed from 2 ft of grey blaes, containing Actinopteria? cf. persulcata, Edmondia punctatella, Sanguinolites cf. clavatus and Bucanopsis sp.

The beds below the Calmy Limestone are again seen farther to the north-east, in a stream 560 yd N. 29° E. of Auchendinny Mains. The Calmy Limestone is separated by a gap of a few inches from about 1 ft of blaes, with a hard limy band which is very fossiliferous. The fauna includes: Orthotetid and Rhynchonellid fragments, Aviculopecten? cf. scoticus, Euchondria sp., Myalina sp.This bed rests on faky blaes, irony, with hard fakes bands at intervals, yielding Lingula mytilloides and about 4 ft thick.

Just over half a mile to the north-east, on the right bank of the River North Esk, on the north side of the railway and 620 yd W. 27° N. of Kirkettle Farm, beds estimated to be about 12 ft below the Calmy Limestone are also exposed. Thus 1 in. of soft crushed blaes rests on black faky blaes about 2 ft thick which is slightly parroty and contains Lingula mytilloides. This in turn rests on black coaly fakes an inch thick.

Calmy Limestone

The thickness of the Calmy Limestone at various localities is indicated on (Plate 4). The section at Joppa is: limestone, grey with reddish veins, with crinoid columnals, Productus (Gigantoproductus)cf. latissimus, P. (Sinuatella) sp., and Spirifer sp.1 ft; blaes 6 in. on limestone, brown-grey 2 ft 9 in., and in the Monkton House Bore: limestone, impure, dark grey, with bands of limy blaes, numerous encrinites and shell fragments 1 ft 6 in. on limestone, grey, with argillaceous plies 1 ft 10 in. In the Bilston Burn the limestone was thicker: limestone, dark grey, faky, crinoidal, 4 in.; blaes, 3 in.; limestone, grey, fairly pure, 10 in.; blaes, limy with crinoids 6 in. on limestone, grey, with small crinoid ossicles 3 ft.

There are several exposures of the Calmy Limestone in the area to the south-west of Penicuik. A hard crinoidal sandy limestone, at least 4 ft thick, is exposed on the right bank of the River North Esk, 830 yd E. 12° N. of Penicuik House; and about 700 yd to the south-west, in a small side stream, on the right bank of the river, 500 yd S.44° E. of the House, 3 ft of sandy limestone, ochreous in parts, crops out, containing an Orthotetid, Stenoscisma sp.and Myalina sp.

On the left bank of the river 500 yd E. 11° S. of Brunston Farm 1 ft 4 in. of coarse, crinoidal limestone rests on 1 ft 6 in. of limestone, sandy, ochreous and decalcified with Productid fragments, Schellwienella?, Stenoscisma sp., Myalina verneuili? (McCoy), Pectinid fragments and Schizodus?.

The limestone is again exposed in the strip of wood on the same side of the river, 200 yd west of the above locality; the details of the section are similar, and the fauna of the lower sandy limestone includes Composita?, Orthotetid fragments, Productus (Productus) carbonarius?, Schellwienella?, Stenoscisma sp., Myalina verneuili? and a Pectinid.

About one and a half miles south of Penicuik, in the Black Burn, 330 yd S.W. of Halls Farm and 45 yd downstream from the junction with the Lead Burn, a limestone 4 ft thick, formerly thought to be the Castlecary, is seen, the top half being crinoidal and the bottom half sandy. Lingula sp., Productus (Gigantoproductus) sp.(latissimoid) and Myalina sp.have been found here. On the left bank of the Lead Burn 25 yd upstream from the junction with the Black Burn, an ochreous sandstone crops out, containing Orthotetid fragments, Productus (Productus) carbonarius?, Stenoscisma sp., Myalina aff. verneuili and an incomplete Pectinid; this bed probably represents the lower part of the Calmy Limestone.

The Calmy Limestone crops in the River North Esk at Esk Mills half a mile below Penicuik, where it appears as a hard grey crinoidal rock, and is again seen about 560 yd north-east of Auchendinny Mains, where there is an outcrop of about 1 ft of hard crinoidal limestone with numerous Productus (Gigantoproductus)cf. latissimus (broad, inrolled form). A poorly preserved trilobite pygidium is also recorded from this locality. Almost two-thirds of a mile farther north-east, on the right bank of the River North Esk, 620 yd W. 27° N. of Kirkettle Farm, about 3 ft of crystalline limestone crops out, containing crinoid columnals, ?Edmondia sulcata and a gastropod fragment. This bed was formerly mapped as the Castlecary Limestone.

The Calmy Limestone is exposed at two places in the River South Esk, north-east of Carrington. In a small inlier on the right bank, about 950 yd W. 16° S. of Harvieston Mains, 1 ft of hard grey limestone having dark partings, with Productus (Gigantoproductus) sp.(latissimoid) is seen resting on 2 ft 4 in. of light grey, hard, crinoidal limestone. A sandy crinoidal limestone at least 2 ft thick, with crinoid columnals, Productus (Gigantoproductus) sp.(latissimoid) and a smooth Spiriferid crops out on the same side of the river about 800 yd farther north.

A limestone with the following section was cut in the shaft of the Lady Victoria Colliery: limestone, impure 1 ft; blaes, soft 3 in. on limestone 2 ft 3 in. Formerly thought to be the Castlecary Limestone, it is now taken as the Calmy.

A hard grey crinoidal limestone at least 2 ft 6 in. thick crops out on the shore about one and a half miles east of the mouth of the River Esk. On the 1954 edition of the six-inch geological map Edinburgh 4 N.E. this bed is shown as the Castlecary Limestone, but information collected subsequent to publication suggests that it is more probably the Calmy Limestone.

Calmy Limestone to Castlecary Limestone

At Joppa the Calmy Limestone lies 275 ft below the Castlecary Limestone, but here strata are believed to be missing owing to a fault. The thickness of the intervening strata is 348 ft 6 in. in the Niddrie railway cutting and 406 ft in the Bilston Burn. An important feature is the occurrence of several Lingula bands and marine shell beds in the central or upper part of the succession (Plate 4). A thin marine limestone, which occurs at Joppa, was also found in the Monkton House Bore. These fossiliferous horizons correspond to the Plean Limestones of the Central Coalfield of Scotland (Crampton in Hinxman and others 1917, pp. 21, 22; Dinham in Dinham and Haldane 1932, pp. 96, 97), but owing to the variations in the measures, it has been found difficult to establish correlations, not only between the Midlothian Coalfield and the Central Coalfield, but also from one area to another within Midlothian.

In the north-western part of the coalfield the Calmy Limestone is generally succeeded by a bed of shelly blaes and faky blaes, which was about 13 ft thick in the Monkton House Bore and over 17 ft thick in Bilston Burn. At both places these strata are succeeded by fakes and sandy fakes, followed by a thick sandstone.

The strata between the Calmy Limestone and the Castlecary Limestone at Joppa are as follows:

It will be observed that the bed of blaes, faky blaes and fakes which generally overlies the Calmy Limestone is very thin at Joppa, owing perhaps to a fault or a local unconformity.

In the Monkton House Bore (Plate 4) the upper half of the succession was very similar to that found on the shore at Joppa, but only one marine band was found, consisting of shelly blaes with a thin marine limestone. The details of this shell-bed and its associated strata were as follows:

The marine shell-bed and limestone correspond to the limestone band of the Joppa shore section. In the Monkton House Bore a 2-ft bed of faky blaes containing shell fragments and fish scales was found about 35 ft below the base of the above section.

In the Bilston Burn the Calmy Limestone is overlain by about 17 ft of faky blaes carrying ironstone nodules, with crinoid columnals, Chonetes cf. laguessianus, abundant Orthotetids, Schellwienella sp., Schizophoria cf. resupinata, Spirifer sp. cf. bisukatus, and Nucula attenuata. The presence of Orthotetids in the shales above the Calmy Limestone would seem to be of importance as a means of identifying this horizon (p. 79).

These beds are succeeded by fakes with ironstone nodules, the latter containing marine fossils; the following fauna has been collected: an Orthotetid (juv.), Productus (Dictyoclostus)cf. scoticus J. Sowerby, Pectinids, and Posidonia sp.There is a greater proportion of sandstone in the upper part of the succession in the Bilston Burn than at localities farther north. The top marine band lies about 100 ft below the Castlecary Limestone, and consists of 1 ft of blaes, containing a Fenestellid, Orbiculoidea sp., Orthotetid fragments, Productus (Dictyoclostus) aff. muricatus, P. (Dictyoclostus)pugilis, Aviculopecten sp.(juv.), Edmondia sulcata?, Palaeolima?, Sulcatopinna sp., and Bucanopsis sp.About 70 ft lower a band of blaes, 3 in. thick, is found, with Promytilus?, lamellibranchs (Myalina? and Sanguinolites?), Euestheria sp., and fish scales. This fossiliferous stratum is underlain by two others, one 11 ft 10 in. below, consisting of 4 in. of blaes with Promytilus sp., Sanguinolites cf. plicatus (Portlock) and ? Sedgwickia suborbicularis, and one 13 ft lower, represented by blaes with Lingula mytilloides, Orbiculoidea sp., and Sanguinolites?. The lowest of these shell beds rests on 1.5 in. of greenish pyritized coaly blaes, underlain by 1 ft of coal with fireclay ribs.

In some of the Penicuik bores shown on (Plate 4) the Calmy Limestone was found to be overlain by a thick bed of blaes, succeeded by fakes and sandstone, but in others the bed of blaes was thin and a sandstone lay close above the limestone. The upper part of the succession between the Calmy Limestone and the top of the Upper Limestone Group includes fakes, blaes, fireclays and thin coals.

A band of ironstone nodules containing a fauna resembling that of the top Plean marine band at Joppa and Bilston Burn was formerly seen in the Hare Burn about one and a half miles south-west of Penicuik and 555 yd W. 19° S. of Ramsay's Monument; the following fossils have been collected: Composita sp., a large ventral valve of an Orthotetid, Productus (Buxtonia) ?, P. (Sinuatella?)(markedly bilobate brachial valve), P. (Dictyoclostus) aff. muricatus, P. (Dictyoclostus) pugilis?, P. (Linoproductus) sp., Aviculopecten cf. interstitialis, A. sp., and Sulcatopinna mutica? (McCoy).

In the River South Esk, to the west of Harvieston Mains Farm three marine shell-beds have been found in the strata between the top of the Calmy Limestone and the conjectural base of the Roslin Sandstone Group (Plate 4). The details of the lowest bed and of the strata between it and the Calmy Limestone as seen on the right bank of the river 950 yd W. 15° S. of Harvieston Mains are:

A calcareous sandstone with Orthotetids (globose dorsal valves) and Productus (Dictyoclostus) sp.representing the upper part of the lowest of the three marine bands crosses the river 360 yd N. 36° W. of Arniston Mains Farm, and farther north, on the right bank 900 yd W. 10° N. of Harvieston Mains Farm, the upper part is again exposed, the details being: fakes, sandy in parts, with sandstone bands, containing worm pipes and an Orthotetid shell (globose dorsal valve) 5 ft on blaes, faky, with thin impure ironstone ribs (a few fragments of brachiopods seen, including a Productid?) 3 ft + .

Farther north, near a sharp bend in the river, 600 yd W. 31° S. of Millbank House, the lowest band is represented by a 2-in. sandy rib containing plant fragments and Orthotetid shells resting on 2 ft of purple blaes with bands of sandy ironstone nodules containing Orthotetid shells (globose dorsal valves) and a Rhynchonellid.

The next-shell bed lies about 48 ft higher in the succession, the intervening strata being composed mainly of reddish sandstone. The band consists of fakes, faky blaes or blaes, generally with ironstone ribs or balls, underlain by a thin coal or coaly blaes. Lingula is the most abundant fossil, but occasionally Orbiculoidea and lamellibranchs have also been found. On the east bank of the river, due west of Harvieston Mains, the succession is: blaes, faky, with plant remains, and hard dark micaceous fakes, with Lingula mytilloides, Orbiculoidea sp., lamellibranch fragments and Donaldina? 3 ft; blaes, faky, black, with a few Lingula fragments 6 in. on blaes, coaly, with coal streaks 2 in.

The highest shell-bed, which is only exposed at one locality, about 460 yd W. 23° N. of Arniston Mains Farm, is separated from the above-mentioned band by 78 ft of strata composed mainly of sandstone, fakes and fireclay with thin coaly ribs. The details of the fossiliferous beds and associated strata are:

In the shaft of the Lady Victoria Colliery the Calory Limestone was overlain by about 44 ft of blaes, succeeded by fakes with irony bands, and sandstone.

A fauna resembling that of the top Plean marine band of Joppa, Bilston Bum and the River South Esk near Harvieston Mains is found in a shell-bed exposed on the shore at Westpans, east of Musselburgh, about 400 yd north-west of Drummore. This bed, which lies 250 ft above the Calmy Limestone, consists of a nodular limestone about 1 ft thick, resting on dark blaes, and contains the following fossils: echinoid plate, Lingula mytilloides, Productus (Dictyoclostus) aff. muricatus, P. (D.)pugilis and Euphemites sp.

Castlecary Limestone

The Castlecary Limestone, which, in most of the Joppa–Roslin area, occurs in two beds, is well exposed on the shore at Joppa, where the details are: limestone, dark, earthy 1 in.; fakes, limy, earthy, shelly and encrinital 2 in.; limestone, crystalline, blue and brown, with solution cavities 5 ft; blaes, grey, shelly 4 ft 6 in. on limestone, grey and brown, shelly and encrinital about 3 ft. In Mountmarle No. 1 Bore (Figure 14), however, the Castlecary Limestone was represented by a dark grey limestone 3 ft 6 in. thick, probably corresponding to the lower of the two posts found at Joppa. The upper bed was presumably eroded before the deposition of the overlying sandstone, a view which is supported by the fact that in the Bilston Burn this sandstone rests directly on the upper bed of the limestone.

No exposures of the Castlecary Limestone are found in the region south-west of Roslin, and in three bores, Penicuik Nos. 49, 60 and 96, it is unrecorded (Plate 4). It is unlikely that the limestone has been overlooked in each of these borings, and its absence is probably due to an unconformity. The conjectural outcrop of the Castlecary Limestone is indicated on several of the recently published 6-in. geological maps of the east side of the coalfield, but it is now considered probable, mainly on palaeontological grounds, that this limestone is missing along the eastern outcrop of the Upper Limestone Group. The limestone formerly mapped as the Castlecary in the River South Esk west of Harvieston Mains, and on the shore north of Drummore, east of Musselburgh, is now taken as the Calmy, since recent investigation has shown that, at both localities, the overlying strata contain faunas which elsewhere in Midlothian are characteristic of the beds between the Calmy and Castlecary limestones.

In the Cowden Colliery and New Mills level, east-south-east of Dalkeith, a limestone 2 ft 6 in. thick was met with about 155 ft above the Calory ((Plate 4); and C. T. Clough and C. B. Crampton in Peach and others 1910, pp. 234–40). The precise correlation of the 2 ft 6 in. limestone is uncertain, but it may represent the Castlecary. W. T., H. S. W.

Palaeontology

A detailed examination of the fossils has shown that distinct faunal assemblages seem to be confined to definite horizons in the Upper Limestone Group. These assemblages were first noted during the examination of the fossils from the well exposed sections on the shore at Joppa, in the Bilston Bum and in Gilmerton Colliery. At these localities continuous sections through the whole or part of the Upper Limestone Group are seen and the correlation of the main limestone horizons with those of other parts of the Midland Valley is well established. When the faunas from isolated outcrops in the Midlothian area were studied it was seen that the same faunal assemblages were present and were distinctive enough to form a basis for correlation all over the Midlothian Basin.

Index Limestone

The limestone and the associated roof blaes are not very fossiliferous. Productus latissimus was recorded from exposures of the Index Limestone in the Bilston Burn and in the Gore Water near Gorebridge (Peach and others 1910, pp. 235, 241). At the latter locality many fossils were said to have been observed but unfortunately, none was collected at the time. Recent visits to the exposures have proved rather disappointing; the former locality yielded nothing and at the latter a few crushed specimens identified as Productus (Gigantoproductus)cf. latissimus J. Sowerby together with Chaetetes sp.were observed. From the exposure of the limestone on the shore at Cuthill, however, shells referred to P. (G.)cf. latissimus were found to be common in a thin calcareous mudstone parting near the base of the limestone. These specimens are also crushed but do not appear to be so wide or inrolled as the form occurring in the Orchard Beds discussed below. In Roslin Colliery, in the return airway between No. 1 and No. 2 Mines the Index Limestone and the associated strata are well exposed. Here, the beds above the limestone are almost barren and no more than the outlines of a few latissimoid Gigantoproductids can be seen on the surface of the limestone. Immediately underneath the limestone there is an unusual development of about a foot of silty mudstone containing Rhynchonellid fragments and a relatively rich molluscan fauna including a short form of Prothyris sp.The fauna bears a superficial resemblance to the first fauna found under the Calmy Limestone, discussed below, but it is not identical with it. This development has not been observed at any other locality in the area and appears to be a very local phenomenon. In the Penicuik Estate area, west of Penicuik, the Index Limestone is mapped as cropping out at two localities, in the Silver Burn (p. 63) and on the banks of the River North Esk south of Penicuik House (p. 63). These two localities are only about half a mile apart but the faunal and lithological developments are quite different from each other, those of the latter in fact having much in common with the Calmy Limestone. The field evidence makes it difficult to interpret the section as other than an exposure of the Index Limestone, but there remains the possibility on palaeontological grounds that it is a small faulted outcrop of higher beds.

Huntershill Horizon

TheHuntershill horizon has been seen at two places in the area. At Bilston Burn the fauna is characterized by abundant Orthotetids, while in the No. 1 Mine Roslin Colliery, Prothyris sp.(a short form) and an Orthotetid have been collected.

Lyoncross Horizon

TheLyoncross horizon has also been seen in both the Bilston Burn and in Roslin Colliery No. 1 Mine. At the former locality a relatively good marine fauna occurs (p. 65) but from the latter locality only Streblopteria ornata has been collected.

Orchard Beds

TheOrchard Beds contain the most prolific marine fauna of any of the fossiliferous horizons of the Upper Limestone Group in the area. The most characteristic member of the fauna, which occurs in profusion in a distinct band near the base of the sequence, is the form identified as P. (G.)cf. latissimus. The specimens are well preserved, although they sometimes occur in such abundance that they are crushed together. The normal width of fully grown individuals is about 100 mm. The pedicle valves are fusiform, spinose and are markedly inrolled in all but the very latest stages of growth when the anterior tends to flatten out and develop longitudinal folds. Of the other Productids which occur in the Orchard Beds, a form closely allied to Productus (Dictyoclostus) muricatus is extremely common and characteristic. The remainder of the fauna is characterized by the abundance of Schizophoria sp., Spirifer spp.,Pectinids and other marine lamellibranchs.

The Orchard Beds are the only part of the Upper Limestone Group in Midlothian where trilobites occur at all commonly. Usually only the pygidia are present and when preservation is good the specimens have been identified as Weberides cf. mucronatus.

Calmy Limestone

TheCalmy Limestone itself is not very fossiliferous but usually contains scarce latissimoid Gigantoproductids. The specimens seen have all been poorly preserved or incomplete. One specimen from the shore section at Joppa has been determined as Productus (Gigantoproductus)cf. latissimus and sufficient of it is seen to show that it is not the same as the form from the Orchard Beds.

Two faunas distinguish the Calmy Limestone. They both occur below the limestone and contain characteristic lamellibranchs. The lower fauna is found some 40 to 60 ft below the Calmy Limestone in the Joppa–Gilmerton–Bilston Burn area and contains Actinopteria? cf. persulcata, Edmondia punctatella and Sanguinolites cf. clavatus. The last named form is known also from the upper fauna but there it is not so common. The presence of Edmondia punctatella is of particular interest as it is known to occur below the Calmy Limestone in many parts of the Midland Valley (Haldane 1925). It was first discovered in Midlothian by Messrs. W. Manson and G. A. Goodlet in the underground workings in Gilmerton Colliery and has now been found at several localities in the area. The upper fauna is from beds some 6 to 12 ft below the limestone in the Joppa–Gilmerton–Bilston Burn area. The characteristic forms are Cardiomorpha cf. limosa, Prothyris cf. elegans and Sanguinolites sp. nov. The last form is probably related to the Sanguinolites variabilis McCoy- omalianus (de Koninck) group but lacks the carinate posterior extension of these species.

Measures between the Calmy and Castlecary limestones

In the section on the shore at Joppa these measures are well exposed and two marine bands, two Lingula bands and one band with Anthraconauta sp.have been recorded. The marine bands are broadly equivalent to the Plean Limestones of the Stirling area but a precise correlation of individual bands is not possible on the present evidence. The upper of the two marine bands is worthy of special attention. It lies about 87 ft below the Castlecary Limestone at Joppa and about 100 ft below it in the Bilston Burn section. The band carries a rich marine fauna, similar in some aspects to, but not as rich as the fauna of the Orchard Beds. The characteristic and common fossil is a form of Productus (Dictyoclostus) muricatus with slightly coarser and more spinose costae than the form present in the Orchard Beds, and it is accompanied by P. (D.) pugilis. The fauna has been recognized from a shore exposure north-east of Westpans, Musselburgh (where it was formerly regarded as a Millstone Grit marine band), in the Hare Burn one and a half miles south-west of Penicuik and in the River South Esk section in Arniston Glen near Gorebridge, where Tylonautilus nodiferus (Armstrong) is also present. There has been some confusion in the past with regard to this last locality. A large fauna was recorded from the band (Peach 1904, p. 120) and the horizon was given as about 242 ft above the No. 6 (Castlecary) Limestone. Later the band was described as marine shale and ironstone (Peach and others 1910, p. 215) and referred to a position some 150 ft above the No. 6 Limestone. The limestone that was originally called the Castlecary is now thought to be the Calmy and the marine band is considered to be about 180 ft above this limestone. The fauna of the marine band was regarded as having affinities with the so-called 'Nebraskan fauna' (Hind 1908) but Hind did not cite this locality when listing the places from which his 'Nebraskan fauna' had been recorded. The original locality at which the band was exposed is 100–150 ft up the steep left bank of the River South Esk at a bend 50 yd upstream from the wooden footbridge and in addition the band has now been located where it crosses the river 170 yd upstream from the footbridge and 460 yd W. 23° N. of Arniston Mains Farm.

Castlecary Limestone

Inthe shore section at Joppa and in Gilmerton Colliery where the normal beds above the Castlecary Limestone are seen, a band containing abundant specimens of Anthraconauta sp.has been found immediately above the limestone. Records of this fossil above the Castlecary Limestone are also known from many other parts of the Midland Valley (Wilson in Francis, 1956, p. 14) .R.B.W.

References

CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., WRIGHT, W. B., BAILEY, E. B., ANDERSON, E. M., and CARRUTHERS, R. G. 1925. The Geology of the Glasgow District. 2nd edit. Mem. Geol. Surv.

DINHAM, C. H., and HALDANE, D. 1932. The Economic Geology of the Stirling and Clackmannan Coalfield. Mem. Geol. Surv.

DRON, R. W. 1910. The Index-Beds in the Carboniferous Limestone Series of Scotland. Trans. Inst. Mining Eng., 38, 383–97.

FRANCIS, E. H. 1956. Economic Geology of the Stirling and Clackmannan Coalfield, Scotland. Area North of the River Forth. Coalfield Papers: Geol. Sum. Gt. Brit. No. I.

HALDANE, D. 1925. Notes on the Discovery of 'Edmondia' punctatella (Jones) in Fife. Trans. Edin. Geol. Soc., 11, 386–9.

HIND, W. 1901–5. A monograph of British Carboniferous Lamellibranchiata, 2, Palaeont. Soc.

HIND, W. 1908. On the Lamellibranch and Gastropod Fauna found in the Millstone Grit of Scotland. Trans. Roy. Soc. Edin., 46, 331–59.

HINXMAN, L. W., CRAMPTON, C. B., ANDERSON, E. M., and MACGREGOR, M. 1917. The Economic Geology of the Central Coalfield of Scotland, Area II. Mem. Geol. Surv.

HOWELL, H. H., and GEIKIE, A. 1861. The Geology of the Neighbourhood of Edinburgh. Mem. Geol. SUPT.

NEWELL, N. D. 1937. Late Paleozoic Pelecypods : Pectinacea. State Geol. Sum. Kansas, 10.

PEACH, B. N. 1904. In Sum. Prog. Geol. Surv. for 1903, 118–25.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

TRAQUAIR, R. H. 1905. On the Distribution of Fossil Fish-remains in the Carboniferous Rocks of the Edinburgh District. Trans. Roy. Soc. Edin., 40,. 687–707.

Chapter 6 Roslin Sandstone Group

General account

The base of the Roslin Sandstone Group is taken at the top of the Castlecary Limestone, where this limestone is present. The available evidence from bores, mines and natural sections, however, suggests that the limestone is present only in the north-western part of the coalfield, in the region extending from Joppa as far south as Bilston Burn (Figure 14). In the New Mills Level, south-east of Dalkeith, a limestone 2 ft 5 in. thick was recorded about 158 ft above the Calmy Limestone (Plate 4), and Clough and Crampton (in Peach and others 1910, p. 239) identified it as the Castlecary Limestone, but this correlation is by no means certain. In the southern and eastern parts of the coalfield, therefore, an estimated position has been chosen for the base of the group.

The top of the group is taken at the base of the Seven Foot Coal in the northern part of the coalfield, and at the base of the Melville Group of coals and fireclays in the southern part (Plate 5) (and p. 93).

Classification

Thegroup thus corresponds approximately to the Millstone Grit of Scottish usage and is defined as such on many of the six-inch maps. In view of the fact that the term Millstone Grit Series as now used in much of Great Britain includes the Upper Limestone and Limestone Coal groups, the older name of Roslin Sandstone Group is here preferred. In consideration of the stratigraphical importance of the factors involved some account of the present position will now be given.

The relationship of the Millstone Grit of Scotland and England has been discussed by Macgregor and Pringle (1934, pp. 1–7). The present state of knowledge, based on their work and on subsequent research, is here briefly summarized.

The base of the Millstone Grit Series in the Pennine area of England is taken at the base of Genus Zone E_l of Bisat's classification in which he subdivides part of the Carboniferous succession on the basis of goniatites (Bisat 1924, 1928). This horizon marks the boundary between the Lower and Upper Carboniferous goniatite faunas. Currie, in a recent paper, states that in Scotland the base of the Pendleian (E_l) Stage can fairly confidently be taken below the Top Hosie Limestone (Currie 1954, p. 535). Goniatites have been found in the Roslin Sandstone Group at only one locality in Midlothian, namely in the marine band which lies about 27 to 32 ft above the Castlecary Limestone in the Bilston Burn, and the specimens found there have been ascribed to the upper part of the Arnsbergian (E₂) Stage (Currie 1954, p. 537). There is at present no evidence that beds of H, R and G age are represented in Scotland. In consequence of this a non-sequence is suspected at some horizon between E₂ and G beds, as is also the case in Northern Ireland (Fowler 1955, p. 42). Such a view supports Kidston's (1894; 1923) work on the floras, reviewed by Crookall (1939, pp. 15–19), for Kidston found a palaeobotanical break within the 'Millstone Grit' on the basis of which a boundary was inserted on the 1910 and 1930 (Solid) editions of one-inch Sheet 32 to indicate the approximate division between Lower and Upper Carboniferous rocks. Traquair (1891; 1903) also drew a distinction between the estuarine fish faunas found below and above the 'Millstone Grit'. It should be noted that the boundary between Lower and Upper Carboniferous rocks in Scotland was drawn at a higher level than that taken between the two subdivisions in England, where it is based on goniatite zones.

The mapping of certain parts of Scotland (Macgregor 1930, pp. 461–3; Ross 1931, pp. 39–43; Pringle and Richey 1931, pp. 25–33; Dinham in Dinham and Haldane 1932, pp. 113–16) suggests that the non-sequence may in fact be an appreciable unconformity although it cannot yet be demonstrated with confidence in Midlothian. Such an unconformity must not be confused with the minor unconformity within the Arnsbergian Stage (E₂), which has been recognized in Stirling and Clackmannan (Dinham in Dinham and Haldane 1932, p. 115) and locally results in the absence of the Castlecary Limestone and even beds underlying it.

At Joppa the highest bed containing Kidston's 'Lower Carboniferous' flora consists of a band of blaes and coal 2 to 3 in. thick lying about 250 ft above the Castlecary Limestone, and a pale grey siliceous rib, half an inch to 1 in. thick, 240 ft higher up in the succession, yields 'Upper Carboniferous' plants. A major unconformity may well lie somewhere between these two plant beds.

In England the top of the Millstone Grit Series is taken at the top of the Rough Rock immediately below the Gastrioceras subcrenatum Marine Band which occurs in beds of G age of Bisat's classification and at the base of the Anthraconaia lenisulcata Zone. No trace of the G. subcrenatum Band has been found in Midlothian. So far as is known the basal beds of the Productive Coal Measures as here defined belong to the Carbonicola commutes Zone unless the marine band above the Seven Foot Coal is a representative of the A. lenisulcata Zone. While the lower beds of the Roslin Sandstone Group therefore, up to the palaeontological 'break', represent part of the Millstone Grit Series of the Pennine region, the relationship of the upper part of the group remains uncertain; it may include strata representing part of the Coal Measures of the English succession.

Lithological characters

TheRoslin Sandstone Group is characterized by grits and sandstones, sometimes coarse, pebbly and red-stained. In the northwestern part of the coalfield (Figure 14) these sandstones occur in the lower half of the succession and again near the top, the intervening strata consisting mainly of mottled red, yellow and grey clays and argillaceous sandstones both of which contain nodules of sphaerosiderite. Most of the clays have been described in logs as fireclays, and are shown as such for example in (Figure 14). The term has, however, been used to cover shales which have been reddened or otherwise altered as well as true seatclays, but none of which is necessarily refractory.

In the Bilston Burn, Carrington and Levenhall areas the complete succession is not exposed, but the seatearths and seatclays appear to be less well developed than in the Joppa–Gilmerton area. In various parts of the coalfield thin conglomerates occur, consisting of fragments of pale grey clay, dark grey blaes, and coal, with occasional pieces of hard siliceous sandstone in a rather coarse matrix of yellow sandstone. The pebbles in the conglomerate vary in length from one-quarter inch to 3 in. and are often angular in outline. These conglomerates, which are sometimes 2 ft to 3 ft thick, frequently rest on eroded surfaces of the underlying beds.

Marine shell-beds are important and occur as: (a) blaes with marine fossils; (b) blaes and ironstone balls, both containing marine fossils; (c) limestone. A shell-bed may be represented by a limestone at one locality and by a calcareous ironstone at another.

In the Millstone Grit Series of the Pennines marine bands with distinctive goniatite faunas have proved of great value in working out the detailed stratigraphy of this formation (Stephens and others 1953). In Midlothian, despite careful collecting, goniatites have been recorded only in one of the marine bands at one locality (p. 89). Consequently a doubt persists as to the precise stratigraphy of the Roslin Sandstone Group, which remains a largely lithological subdivision (p. 84). The marine bands which do occur have been used locally, but with some hesitation, for correlation (Figure 14); it is at present not possible to make correlations between the marine shell-beds found in the north-west part of the coalfield (Joppa–Bilston Burn) with those on the east side (River South Esk and Westpans).

Several coal seams are found in the Roslin Sandstone Group, but the majority are only a few inches thick.

Outcrop

On the west side of the coalfield the Roslin Sandstone Group is well exposed on the shore at Joppa, where, with the exception of a gap of 45 ft near the base, an almost complete succession can be seen. The steep dip of 50 to 60 degrees at Joppa continues as far south as the Sheriffhall Fault (Figure 18). South of this fault, however, the dip decreases and the width of the outcrop is much greater. From Melville Castle southwards the beds strike along the valley of the River North Esk by Lasswade to Hawthornden and Roslin, where the cliffs on either side of the river are formed by the massive gritty red sandstones of the upper part of the group. Good exposures of the lower part of the succession are seen in the Bilston Burn, near its junction with the River North Esk.

South-westwards from Roslin the outcrop extends in a synclinal belt as far as Auchencorth Moss. Extensive drift deposits conceal the solid rocks between Roslin and the River South Esk near Carrington so that the outcrop is not known with any certainty; it is probable that a large part of the group is cut out in that area by the Vogrie Fault.

On the eastern side of the coalfield exposures occur in the River South Esk in the vicinity of Carrington, and on the shore at Levenhall, east of Musselburgh.

Details

At Joppa and in the Redcroft Fireclay Mine one and a quarter miles to the south-south-west, the Castlecary Limestone is overlain by a bed of shaly blaes 3 ft and 3 ft 9 in. thick respectively, containing abundant Anthraconauta sp.with ostracods and fish remains. The lower part of this bed is more shaly than the upper part, and thin ironstone ribs are present throughout. In the Millstone Grit Mine at Gilmerton Colliery the succession immediately above the Castlecary Limestone was as follows:

The shaly or parroty blaes probably represents- the oil-shale which overlies the Levenseat Limestone in the eastern part of the Central Coalfield (Grant Wilson in Peach and others 1910, p. 137; Carruthers in Carruthers and others 1912, pp. 142, 146; Macgregor in Macgregor and Anderson 1923, p. 44; Conacher in Carruthers and others 1927, p. 245; Dinham in Dinham and Haldane 1932, p. 99; Wilson in Francis 1956, p. 14). In Monkton House No. 37 Bore this horizon is represented by 6 in. of carbonaceous faky blaes with fish remains and coprolites, separated from the Castlecary Limestone by 7 in. of blaes and limy blaes. No trace of the shaly bed was found either in the section exposed in the Bilston Burn or in Mountmarle No. 1 Bore. At the former locality the upper bed of the limestone is directly overlain by a sandstone, while in the bore the upper bed is apparently absent, and the basal beds of the Roslin Sandstone Group consist of sandstone with clay or shale bands.

In the Millstone Grit Mine at Gilmerton Colliery and in the Bilston Burn three marine horizons occur within 80 ft of the base of the group. The section at the former was:

In the Bilston Burn the details of the corresponding part of the succession are:

The lowest marine band mentioned in these two sections was also found in the Red-croft Fireclay Mine and in the railway cutting between Niddrie Junction West and Niddrie Junction South. At both localities a marine limestone was present. On the shore at Joppa the two lower bands, if present, are obscured by mud and boulders; a shelly ironstone, underlain by soft grey blaes with occasional marine fossils occurs about 80 ft above the Castlecary Limestone and is thought to represent the uppermost band.

At Joppa there are seven marine bands above the one just mentioned, each of which consists of a thin bed of blaes, generally containing balls or nodular ribs of ironstone. In Monkton House No. 37 Bore only two marine shell-beds were found in the Roslin Sandstone Group, but the apparent absence of others may be due to the fact that fossils are very scarce in many of these bands. Correlations suggested by a detailed comparison of the bore-log and the Joppa shore section are shown in (Figure 14). It appears, however, that the three marine bands found near the base of the Roslin Sandstone Group in Gilmerton Colliery and in the Bilston Burn are missing in the Monkton House Bore, probably owing to a minor unconformity.

In the Bilston Burn three higher marine horizons have been found in addition to the three described on p. 89. About 109 ft above the Castlecary Limestone there is a bed of fakes and faky blaes with ironstone nodules and sparse marine fossils, including Lingula mytilloides, Productus (Productus) carbonarius?, Edmondia? and Euphemites?, resting on 9 in. of dark carbonaceous blaes with numerous marine fossils, including Productid fragments, Promytilus sp., and other lamellibranchs. About 21 ft higher in the succession a 3 ft 6 in. bed of blaes occurs, containing nodular ironstone bands and sparse marine shells. The details of the highest marine band and the associated strata are as follows :

In Mountmarle No. 1 Bore, where the upper leaf of the Castlecary Limestone is absent, a total of 327 ft of Roslin Sandstone Group was passed through, consisting mainly of sandstones with beds of blaes. Penicuik No. 96 Bore (Figure 14) is one of a series which indicates that the Castlecary Limestone is absent in the area immediately north-east of Penicuik. An arbitrary line has therefore been taken in this bore for the base of the Roslin Sandstone Group, about 160 ft above the 4-ft limestone that is considered to be the Calmy Limestone.

South-west of Penicuik, on the south bank of the River North Esk, in South Bank Wood there are exposures of massive purplish and grey sandstones with intercalations of fakes. A bed made up of angular pebbles derived from volcanic material set in a sandy matrix is reported to have been seen slightly lower in the succession (Hinxman in Peach and others 1910, p. 249). Recently outcrops of conglomerate were found containing rounded pieces of white sandstone, grey clay, ironstone, oil-shale and some black carbonaceous material in a purple matrix, but no volcanic material was recognized.

In the River South Esk near Carrington, there are exposures of the lower part of the succession. In the course of the recent revision of this area it has been decided, mainly on palaeontological grounds, that the Castlecary Limestone is absent and that the limestone formerly regarded as the Castlecary (C. T. Cough and C. B. Crampton in Peach and others 1910, p. 241) is probably the Calmy; of the five marine bands previously thought to be of Roslin Sandstone age (C. T. Clough in Peach and others 1910, pp. 249–52), only the two upper ones are now placed in that part of the succession.

The lower band is exposed 520 yd W. 18° N. of Arniston Mains Farm, where the section is as follows :

Farther north, on both sides of the river, 60 to 70 yd downstream from the bridge due west of Shank House, the same band is represented by a calcareous ironstone 1 ft thick, which weathers to haematite and contains marine fossils including Chaetetes sp., Schizophoria? and Spirifer sp.Still farther north, 700 yd W. 5° S. of Millbank House, the following section was seen: limestone, nodular, sandy, haematitic, with marine fossils, including a Clisiophyllid coral, crinoid columnals, Composita?, Productid fragments, and Spirifer sp. 1 ft 8 in.; blaes, purple, with ironstone nodules 3 in. on blaes, coaly 0.5 in.

The upper marine band found in the River South Esk lies about 100 to 115 ft above the lower one, the intervening strata consisting mainly of sandstone, violently false-bedded in part, with several beds of fireclay. The shell-bed crops out on the left bank, 950 yd W. 40° S. of Millbank House, the section being:

Another outcrop occurs 10 yd up a small stream on the east bank of the river, and 1050 yd E. 9° S. of Carrington church, where 7 ft of red and purple blaes are seen with occasional ironstone nodules and Productus (Productus)cf. carbonarius.

On the left bank of the river, 815 yd W. 16° N. of Millbank House, there is an outcrop of purple and grey blaes 1 ft thick, with ironstone nodules, the latter containing marine fossils. Chonetes sp., Lingula sp., Orthotetid shells, Productus (Linoproductus) sp., Spirifer sp., Edmondia?, Limatulina'? and Pectinid fragments have been recorded from this locality. The position of this bed in the Roslin Sandstone sequence is uncertain; it is probably on the same stratigraphical horizon as one or other of the two marine bands described above, and may possibly be on the horizon of the highest shell-bed found in the group at Joppa.

Strata belonging to the Roslin Sandstone Group are exposed on the shore at Westpans, east of Musselburgh, but the outcrops are much obscured by mud and only certain parts of the succession can be seen. Evidence, accumulated since the six-inch geological map Edinburgh 4 N.E. was published in 1954, suggests that the limestone shown on that map as the Castlecary is the Calmy, and that the 1-ft nodular marine limestone lying about 245 ft higher in the succession and formerly included in the Roslin Sandstone Series (Clough and Gibson in Peach and others 1910, p. 252) is of Upper Limestone Group age. The Castlecary Limestone is considered to be missing and the base of the Roslin Sandstone Group is now taken at the top of the 1-ft limestone. Two marine bands have been recorded at Westpans in the strata now taken to represent the Roslin Sandstone Group. The lower, a bed of blaes with ironstone nodules about 40 ft above the conjectural base of the group was formerly seen on the east side of Westpans Rocks, about 450 yd N.W. of Drummore; both blaes and ironstone contain marine fossils. A massive sandstone, gritty in parts and about 100 ft thick ('Westpans Rocks') separates this marine band from the higher one, which consists of blaes with a nodular ironstone band which has yielded Productus (Productus) carbonarius? and a poorly preserved gastropod. This shell bed is underlain by an impure coal 1 to 2 in. thick. W.T., H.S.W.

Palaeontology

A band containing abundant specimens of Anthraconauta sp.overlies the Castlecary Limestone at Joppa and in the Redcroft Mine (p. 87).

Several marine bands are known from the lower part of the Roslin Sandstone Group in the area but not enough information is available to correlate individual bands. One marine band worthy of mention is that occurring some 30 ft above the Castlecary Limestone in the Bilston Burn (p. 89). This band is of historic interest because Hind (1908) claimed that some 50 per cent of the lamellibranch species showed a close resemblance to species from the Coal Measures of Nebraska and Illinois. When Hind published this work he had only seen some 66 specimens from the locality, many of them poorly preserved. Soon afterwards D. Tait, its discoverer, made more extensive collections from it and recently Mr. W. E. Graham collected many more specimens from the same locality. The whole collection has now been examined and the faunal list is given on p. 89. Some of Hind's original determinations based on poor material have been amended and additions have been made to the original faunal list (Hind 1908, p. 337), including some new species of Pectinids.

It is considered that the fauna does not resemble American faunas so closely as Hind thought but that it is typical of the shelly facies containing abundant lamellibranchs and calcareous brachiopods at the top of the Arnsbergian (E₂) Stage of the British Namurian. This shelly facies was predominant in Scotland at the same time as the dark grey mudstones containing goniatites and lamellibranchs were being deposited in the Pennine area of England. Only at a few places in the latter area such as Congleton Edge (Hind 1910, p. 578) are shelly faunas found and then at somewhat higher horizons in the Millstone Grit Series. It is of interest to note that Hind (1908, p. 333) thought that the brachiopods of the Scottish 'Nebraskan fauna' were identical with those found at Congleton Edge. R.B.W.

References

BISAT, W. S. 1924. The Carboniferous Goniatites of the North of England and their Zones. Proc. Yorks. Geol. Soc., 20, pt. 1,40–124.

BISAT, W. S. 1928. The Carboniferous Goniatite Zones of England and their continental Equivalents. Compte Rendu Congres de Strat. Carb., Heerlen, 1927,117–33.

CARRUTHERS, R. G., CALDWELL, W., and STEWART, D. R. 1912. The Oil-Shales of the Lothians. 2nd edit. Mem. Geol. Surv.

CARRUTHERS, R. G., CALDWELL, W., BAILEY, E. M. and CONACHER, H. R. J. 1927. The Oil-Shales of the Lothians. 3rd edit. M., Geol. Surv.

CROOKALL, R. 1939. The Plant 'Break' in the Carboniferous Rocks of Great Britain. Bull. Geol. Surv. Gt. Brit. 1, 13–26.

CURRIE, ETHEL D. 1954. Scottish Carboniferous Goniatites. Trans. Roy. Soc. Edin., 62, 527–602.

DINHAM, C. H., and HALDANE, D. 1932. The Economic Geology of the Stirling and Clackmannan Coalfield. Mem. Geol. Surv.

FOWLER, A. 1955. The Zonal Sequence in the Carboniferous Rocks of south-east Tyrone. Bull. Geol. Surv. Gt. Brit., 8, 38–43.

FRANCIS, E. H. 1956. The Economic Geology of the Stirling and Clackmannan Coalfield, Scotland. Area North of the River Forth. Coalfield Papers: Geol. Surv. Gt. Brit. No. 1.

HIND, W. 1908. On the Lamellibranch and Gastropod Fauna found in the Millstone Grit of Scotland. Trans. Roy. Soc. Edin., 46, 331–59.

HIND, W. 1910. Staffordshire. Geology in the Field. Jubilee Volume. Geol. Assoc. 564–91.

KIDSTON, R. 1894. On the Various Divisions of the British Carboniferous Rocks as determined by their Fossil Flora. Proc. Roy. Physical Soc. Edin., 12, 183–257.

KIDSTON, R. 1923. Fossil Plants of the Carboniferous Rocks of Great Britain. Mem. Geol. Surv., Palaeont.

MACGREGOR, M., and ANDERSON, E. M. 1923. The Economic Geology of the Central Coalfield of Scotland, Area VI. Mem. Geol. Surv.

MACGREGOR, M. 1930. Scottish Carboniferous Stratigraphy. An Introduction to the Study of the Carboniferous Rocks of Scotland. Trans. Geol. Soc. Glasgow, 18, 442–558.

MACGREGOR, M., and PRINGLE, J. 1934. The Scottish Millstone Grit and its position in the Zonal Succession. Sum. Prog. Geol. Surv. for 1933, pt. 2,1–7.

PEACH, B. N., CLOUGH, C. T., HJNXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

PRINGLE, J. and RICHEY, J. E. 1931. Carboniferous Rocks of the Thornhill Basin, Dunnfriesshire. Sum. Prog. Geol. Surv. for 1930, pt. 2,25–33.

ROSS, G. 1931. An Unconformity of Millstone Grit Age in the Douglas Coalfield, Lanarkshire. Sum. Prog. Geol. Surv. for 1930, pt. 2,39–43.

STEPHENS, J. V., MITCHELL, G. H., and EDWARDS, WILFRID. 1953. Geology of the Country between Bradford and Skipton. Mem. Geol. Surv.

TRAQUAIR, R. H. 1891. List of Fossil Dipnoi and Ganoidei of Fife and the Lothians. Proc. Roy. Soc. Edin., 17, 385–400.

TRAQUAIR, R. H. 1903. On the Distribution of Fossil Fish-remains in the Carboniferous Rocks of the Edinburgh District. Trans. Roy. Soc. Edin., 40, 687–707.

Chapter 7 Coal Measures

It has long been the practice in Scotland to subdivide the Coal Measures into the Productive Coal Measures below and the Barren Red Coal Measures above, the boundary between the two being taken for convenience at the top of Skipsey's Marine Band. This classification is adhered to in the present account.

It is only right to point out, however, that though this is in many ways convenient, it suffers from certain disadvantages. In some areas grey measures with coal seams occur above Skipsey's Marine Band; in others the marine band is absent or cannot be recognized, so that an arbitrary line, approximating to its horizon, has to be taken.

Recent research has made it clear that in many districts, if not everywhere in Scotland, the Barren Red Measures are in fact grey Coal Measures which have suffered red-staining and other alteration. This alteration includes the destruction of coal seams or their passage into dolomite and the obliteration of fossils. It was apparently brought about by the downward percolation of solutions from an old land surface formed of folded and faulted Coal Measure and earlier rocks, which existed before the deposition of the New Red Sandstone. The depth to which the alteration took place also varied so that the base of the zone of reddening and other alteration now lies at different horizons ranging from above Skipsey's Marine Band to considerably below it. The alteration of the coals is discussed on p. 96 and further notes on associated phenomena are given on p. 113.

Productive Coal Measures

(Figure 15) shows a generalized vertical section of the Productive Coal. Measures in the Midlothian Coalfield. In the northern part of the coalfield the base of the Productive Coal Measures is taken at the bottom of the Seven Foot Coal. To the south of the Sheriffhall Fault, however, the base is less well defined, since the Seven Foot Coal and the succeeding Pinkie Four Foot Coal tend to split southwards (Plate 5), developing into a group of variable coals and fireclays, which has been named the Melville Group on the recently published six-inch maps of the coalfield. The top of the Productive Coal Measures is taken at the top of Skipsey's Marine Band, a bed of marine shale containing a thin impure marine limestone, which is seen in the rivers North and South Esk in Dalkeith Park.

Lithological characters

TheProductive Coal Measures are composed mainly of white and grey sandstones, grey and dark grey shaly sandstones, sandy shales, shales, seatearths and a number of thick coal seams, of which at least fourteen have been worked underground. There are several thinner seams, some of which have been wrought at outcrop. Bands and balls of brown clay-band ironstone are frequently present in the shales and seatearths. In general the shales of the Productive Coal Measures are less sandy and less micaceous than those of the Limestone Coal Group. In the upper part of the Productive Coal Measures the sandstones are often stained red, and the shales are usually red and purple-grey in colour, while the ironstones have been converted to deep red haematite. Many of the sandstones in the Productive Coal Measures are coarse-grained in parts, with pebbly beds. A few thin beds of impure compact argillaceous limestone, believed to be of secondary origin, and generally associated with red and purple shales, have been found on different horizons (pp. 96).

In addition to Skipsey's Marine Band two other marine horizons are present. In the Millstone Grit Mine at Gilmerton Colliery Lingula and other brachiopods have been found in blaes and ironstone nodules just above the Seven Foot Coal. Faky blaes with ironstone nodules carrying marine shells crop out on what is thought to be the same horizon in a small burn (Castleview of (Plate 5)) about 500 yd E.S.E. of Roslin Chapel. The other band, known as the Queenslie Marine Band (Manson 1957) which has been noted in several recent borings, occurs between the Little Splint Coal and the Golden Coal (Figure 15), and contains foraminifera, Lingula and fish remains.

Several beds contain non-marine lamellibranchs (mussels) which occur usually either as flattened specimens in shale or preserved in the round in ironstone nodules. The richest and most widespread mussel band is the one above the Fifteen Foot Coal.

Outcrop and workings

The Productive Coal Measures occupy a belt of country approximately nine miles long extending south-south-west from the sea at Musselburgh to just beyond Carrington. The width of the outcrop varies considerably from place to place, the variation being due mainly to cross faults. At Musselburgh the outcrop is about two and a quarter miles wide; south of Dalkeith, immediately south of the Sheriffhall Fault, it narrows to about one and a half miles, but becomes broader again towards the south end of the outcrop.

Owing to the fact that the Midlothian Coalfield is largely drift-covered, there are very few natural exposures of the junction between the Millstone Grit and the Productive Coal Measures. The line shown on the geological maps for the base of the Productive Coal Measures is thus mainly conjectural and is based principally on information from underground workings and from borings.

It will be observed that on the generalized vertical section (Figure 15) alternative names are given for most of the coals in the lower part of the Productive Coal Measures. The names on the left-hand side are those used in the area to the north of the Sheriffhall Fault, while those on the right-hand side (with the exception of the Six Foot Coal and Pinkie Three Foot Coal) are those used to the south of the fault. The Fifteen Foot Coal of Joppa and Newcraighall splits into two seams as it is traced south and east, the upper being called the Pinkie Three Foot Coal and the lower the Six Foot Coal.

North of the Sheriffhall Fault the most extensively worked coals in the lower part of the Productive Coal Measures are the Fifteen Foot Coal, the Nine Foot Coal, Salters Coal, and the Cowpits Five Foot Coal. The Little Splint Coal has been worked to a limited extent from Woolmet Colliery, and comparatively small workings exist in the Seven Foot Coal. In the upper part of the Productive Coal Measures the Musselburgh Jewel Coal and the Rough and Splint coals have all been extensively wrought and relatively small areas of the Diamond and Beefie seams have been won on the east side of the coalfield. None of the coals above the Little Splint is at present worked.

South of the Sheriffhall Fault the Jewel Coal of Whitehill, the Whitehill Splint and Rough coals, and the Whitehill Great Seam have all been mined extensively, while the Parrot Rough Coal and the Dalkeith Under and Upper coals have also been wrought, although on a much smaller scale.

Calcareous coals and carbonaceous limestones

InDalkeith No. 48 Bore, sited about 675 yd N.E. of Dalkeith House, two impure limestones were recorded in the upper part of the Productive Coal Measures; one was pale brown in colour, the other greenish-grey, and both contained ribs of impure coal (pp. 111–112). Each was underlain by fireclay, and the upper was overlain by blaes containing fragments of shells, while the lower was succeeded by 8 in. of very pale creamy marl overlain by limy blaes. Comparison of the journal of this bore with the journal of Olivebank No. 2 Bore indicates that the upper limy horizon can be correlated with the Clayknowes Coal and the lower with the Splint Coal (Figure 15).

About 1200 yd S.W. of Dalkeith House, in a bore near Ironmill, ribs of compact buff limestone, brecciated in parts, with carbonaceous streaks, were found, associated with 4 in. of coal, the details being: limestone, buff, compact 1 ft 2 in.; fireclay 10 in.; fakes, brown, limy 1 in.; coal 4 in.; limestone, buff, brecciated, with carbonaceous streaks 6 in. on limestone, pale brown, rooty 3 ft.

The coal in this section probably corresponds to the seam generally found underlying the Queenslie Marine Band. A bore sunk to a depth of 400 ft at Dalkeith Brewery, about 650 yd E. of the Ironmill Bore, passed through three limy horizons, each composed of more than one bed of limestone. Many of these calcareous beds contained thin ribs of carbonaceous material and several were brecciated, being composed of small irregular pieces of buff limestone embedded in blaes. The strata penetrated in this bore were formerly thought to be on the north side of the Sheriffhall Fault and to belong to the Barren Red Coal Measures. It is more probable, however, that the fault passes to the north of the bore, and that the brecciated and carbonaceous limestones represent altered coals in the Productive Coal Measures. Comparison with nearby bores suggests that the lowest calcareous bed is approximately on the horizon of the Glass Coal, that the middle limestones represent the Quarry Coal and the Cowpits Five Foot Coal, and that the upper limestones represent the Little Splint Coal and a seam about 18 ft lower in the succession.

Each of the bores mentioned above was sunk close to a large fault, and in each case the strata associated with the altered coals were stained reddish and purple.

The passage of a seam of coal into a bed of dolomite in Wirral Colliery, Cheshire, was described by Strahan (1901). Dron (1905) has given a detailed account of the occurrence of calcareous coal at Dalzell and Broomside Colliery, south of Motherwell, and further information regarding the same phenomenon in the Lanarkshire area was given by M. Macgregor (in Clough and others 1920, pp. 120–21) and by C. T. Clough (in Clough and others 1926, pp. 93–7). Dron found that the most marked alteration occurred in the vicinity of faults, but Clough (in Clough and others 1926, p. 95) stated that some of the calcareous coals in the Coatbridge area occur in a part of the coalfield which is fairly free from faults, while farther west, where faults are numerous, no alteration has been encountered. In the discussion on Dron's paper it was stated that, whenever calcareous coal was found in the Splint seam, the blaes overlying the coal were strongly tinged with red, and Clough also commented that the strata in the roof of altered coals in the Coatbridge vicinity were generally reddened.

In No. 4 Pit, Mauchline Collieries, Ayrshire, the Tourha' Coal was found to pass laterally into a dark grey argillaceous limestone 1 ft thick, which consisted of a central granular portion 4 in. thick, overlain and underlain by an equal thickness of limestone with well developed cone-in-cone structure (Flett 1929, pp. 40–1; Mykura 1956).

Details

Seven Foot Coal to base of Salters Coal

Seven Foot Coal, Pinkie Four Foot Coal and intermediate strata (Melville Group)

At Joppa, Newcraighall, Woolmet and in bores near Monktonhall, Monkton House and Castle Steads the Seven Foot Coal and the Pinkie Four Foot Coal are quite distinct and are separated by strata varying in thickness from 25 ft to 40 ft. South of the Sheriffhall Fault, however, the seams tend to split up into a group of variable coals, which, along with their associated strata, have been named the Melville Group. On the north-east side of the coalfield, at Cowdenfoot, Smeaton and Pinkie the two seams are usually close together.

On the shore at Joppa only the lower and upper parts of the Seven Foot Coal can be seen, but according to old records the section of the seam was as follows: coal 1 ft 3 in.; fireclay 4 ft; coal 6 ft; fireclay 2 ft 6 in. on coal 2 ft. The strata between the Seven Foot Coal and the Pinkie Four Foot Coal consist mainly of fakes, sandy fakes and sandy fireclay, the total thickness being 35 ft. About 12 ft above the Seven Foot Coal there is a bed approximately 1 ft thick, consisting of alternations of sandy ironstone and thin beds of coaly blaes. The ironstone, which contains fragments of mussels and fish remains, has numerous small inclusions of fusain and bright coal, giving the rock a brecciated aspect.

Near the pit-bottom at Newcraighall Colliery the Seven Foot Coal is 6 ft thick, and in Monktonhall No. 2 Bore the section was: coal 1 ft 9 in.; blaes 1 ft 11 in.; coal 5 ft 4 in.; blaes 1 ft 7 in. on coal 2 ft 3 in. In this bore the Seven Foot and Pinkie Four Foot coals were separated by 34 ft of strata, mainly sandstone, faky blaes and fakes, with a 10-in. coal in the lower part. The section of the Pinkie Four Foot Coal near the pit-bottom in Newcraighall Colliery is: coal 7 in.; fireclay 6 in.; coal, soft 7 in.; coal, hard 2 ft 9 in. on coal, sclitty 3 in.

The base of the Productive Coal Measures is not exposed in the workings at Wool-met Colliery, but the journal of an old underground bore put down three-quarters of a mile south-south-east of the pit gives the section of the Seven Foot Coal as : coal 9 in.; fireclay 1 ft 6 in. on coal 4 ft. The Pinkie Four Foot Coal, separated from the Seven Foot by 25 ft of strata, was 3 ft thick.

At Gilmerton Colliery a good section of the lower part of the Productive Coal Measures was exposed in the Millstone Grit Mine, driven in 1942–43. A notable feature is the deterioration of the Seven Foot and Pinkie Four Foot coals. The latter is represented by 1 ft 9 in. of coaly fireclay, and the former by 1 in. of coaly blaes resting on 7 in. of coal. Immediately above the position of the Seven Foot Coal there is a bed of grey blaes with ironstone nodules, some of which contain marine fossils, among which are foraminifera including Rectocornuspira?, Lingula mytilloides, Productus ('Pustula') sp., and irregular vermiform structures.

Several bores put down north-west of Eskbank in the area between South Melville Farm and the River North Esk showed that the Seven Foot Coal and the Pinkie Four Foot Coal are there represented by a very variable group of coals, separated by sandstone, fakes and fireclay, with thin bands of blaes with ironstone ribs and balls. The total thickness of the group, including coals and intervening strata is about 50 ft, and the thickness of the individual coals varies from 6 in. to 3 ft 9 in. At Esk Mouth Bore, mudstones about 14 ft above the Seven Foot Coal yielded Carbonita humilis (Jones and Kirkby) and fish remains, but no marine fossils were recognized.

The details of the Melville Group are not well known in the Polton area; bores near Midfield indicate that the succession there is similar to that found north-west of Eskbank, but the coals seem to have decreased both in number and in thickness.

Little is known of the Melville Group at Whitehill Colliery. A blind bore or pit put down from the Jewel Coal of Whitehill about 250 yd N.E. of the pit-bottom struck three thin coals at a depth of about 70 ft. These coals, no doubt part of the Melville Group, had the following section: coal 10 in.; blaes and fireclay 3 ft 1 in; coal 1 ft; clay 4 in. on coal 7 in.

In a small stream on the south-east bank of the River North Esk, about 450 yd E.S.E. of Roslin Chapel there are exposures of strata which are considered to belong to the Melville Group. These beds, about 60 ft thick, consist mainly of blaes, fireclay, and thin sandstone bands, with several coals, mostly thin. The lowest coal is 1 ft 6 in. thick and overlies a fireclay which in turn rests on a thick sandstone. This coal is overlain by blaes containing ironstone nodules which have yielded occasional marine fossils including Polyzoa?, Lingula sp., Productus ('Pustula') sp., Aviculopecten scalaris (J. de C. Sowerby) and Edmondia sp.Beds of the Melville Group are also seen in the south bank of the North Esk, in the large bend south of Roslin Castle; about 20 ft above the top of the massive sandstone on which these beds rest D. Tait found a band containing a few specimens including Edmondia cf. transversa Hind, pectinid lamellibranch fragments and an indeterminate fish scale.

According to a bore put down just south-west of Stonefield Hill Farm the upper part of the Melville Group in that vicinity contains coals which are rather thicker than those in the Eskbank, Polton and Whitehill areas. The total thickness of the group was about 112 ft, as follows:

The top coal of this section was possibly the Jenny Meggat, a seam which is said to have been formerly worked in the Whitehill area.

On the right bank of a small stream, 530 yd N.W. of Redside Farm, a trench dug in 1950 revealed the following section: fakes 2 ft; limestone, lenticular, cone-in-cone structurepart 0 to 3 in. fakes 7 in.; coaly fireclay and fireclay 4 in.; coal, bright 7 in.; hard sandy limy bed with cone-in-cone structure 0.5 in in. to 2.5-in.; coal, bright 3 ft; fakes, coaly 1 in. on coal, bright, with hard fusain bands 1 ft. These strata are thought to be part of the Melville Group.

Measures which probably belong to the Melville Group were passed through in Aikendean No. 1 Bore, about 650 yd S.S.W. of Aikendean Farm; the beds included two coals 18 ft apart, the upper being in leaves, as follows: coal 5 in.; fakes 3 in.; coal 4 in.; coaly fakes 3 in. on coal, splint 2 ft 2 in. The section of the lower coal was: coal 1 ft 10 in.; blaes, parroty 1 ft 1 in. on coal 6 in. The upper coal was overlain by 2 in. of blaes, overlain in turn by fakes containing ironstone nodules, one of which yielded specimens of Anthraconauta subovata Dewar.

The Melville Group was passed through in Upper Dalhousie Farm No. 1 Bore immediately west of the farm. The beds consisted of about 80 ft of sandstone, fakes and fireclay, with thin coals. The thickest coal, about 30 ft from the base of the group, occurred in two leaves: coal 1 ft 5 in.; blaes 1 in. on coal 5 in.

Another exposure of beds thought to belong to the Melville Group occurs on the right bank of the River South Esk, 150 yd N.N.E. of Prestonholm House, where two coals 4 ft 2 in. apart are seen. The upper coal, which is rather disturbed in the section, appears to be about 2 ft 9 in. thick, and the lower is 9 in.

In the region immediately north of Cowdenfoot the lower part of the Productive Coal Measures has been proved in several bores. Here, as is generally the case along the north-east side of the coalfield, the Seven Foot and Pinkie Four Foot coals are close together, giving a series of coals with partings of fireclay and blaes. In a bore 400 yd

N.E. of Cowdenfoot the section of the combined Seven Foot and Pinkie Four Foot seams was: coal 7 in.; blaes 3 in.; coal 2 ft 4 in.; fireclay 2 ft; coal 1 ft 4 in.; fireclay 1 ft; blaes 1 ft on coal 3 ft.

A boring put down near the mouth of No. 9 Mine, Dalkeith Mines, near Smeaton, gave the following section for the combined seams : coal, soft, 2 ft 1 in.; fireclay 5 ft 5 in.; coal 1 ft 4 in.; fireclay 1 ft 8 in.; coal 1 ft 9 in.; fireclay 4 in.; coal 2 ft 4 in.; fireclay 4 ft 11 in. on coal 1 ft 1 in.

Farther north, in Pinkiehill No. 5 Bore 630 yd W.S.W. of Barbachlaw Farm, the details were:

In another bore in the Pinkie area (Pinkiehill No. 5 Bore) the Seven Foot and Pinkie Four Foot coals were separated by 12 ft 7 in. of strata.

Strata between the Pinkie Four Foot Coal and the Fifteen Foot Coal

The strata between the Pinkie Four Foot Coal and the Fifteen Foot Coal are the equivalents of the measures between the Melville Group and the Jewel Coal of White-hill (Figure 15). Furthermore the lower part of the Fifteen Foot Coal is represented by the Six Foot Coal of Pinkie.

At Joppa the section above the Pinkie Four Foot Coal is as follows:

The interval between these strata and the position of the Fifteen Foot Coal is occupied mainly by a massive false-bedded sandstone, coarse and gritty in parts, the total thickness of measures from the top of the Pinkie Four Foot Coal to the bottom of the Fifteen Foot Coal being about 92 ft.

Near the pit-bottom at Newcraighall Colliery the beds between the Pinkie Four Foot Coal and the Fifteen Foot Coal are about 85 ft thick, and include a sandstone 60 ft thick. The section above the Pinkie Four Foot Coal is as follows:

At the Esk Mouth Bore, 230 yd W. of the Gasworks at Musselburgh, dark mudstone 4 ft 7 in. above the Four Foot Coal yielded Carbonicola cf. pseudorobusta Trueman and fish remains including Rhabdoderma sp.and Rhizodopsis sp.A grey mudstone 2 ft 5 in. above contained an indeterminate lamellibranch (? C. bipennis group).

In Monktonhall No. 1 Bore the Fifteen Foot Coal was split into the Six Foot Coal and the Pinkie Three Foot Coal, and the 44 ft of strata between the Pinkie Four Foot and the Six Foot coals consisted mainly of fakes and sandstone.

South-south-east of Woolmet Colliery, in the underground bore mentioned earlier (p. 97), the Pinkie Four Foot Coal is separated from the Six Foot Seam by 82 ft of strata, mostly sandstone. In Monkton House No. 37 Bore where the interval between the two seams was about 78 ft, the details of the intervening strata were:

In the Millstone Grit Mine at Gilmerton the Pinkie Four Foot Coal and the Six Foot Coal are separated by about 90 ft of strata, practically all sandstone.

South of Dalkeith the interval between the top of the Melville Group and the Jewel Coal of Whitehill is occupied mainly by sandstone, exposures of which are seen in the South Esk near Elginhaugh and in the railway cutting at Broomieknowe, south of Lasswade. The sandstone was formerly quarried near Broomieknowe, where it is massive, coarse and pebbly, and at least 40 ft thick. The total thickness of intervening strata is about 55 ft at Eskbank and 65 to 70 ft in the Whitehill area.

At Cowdenfoot and Pinkie the comparable measures consist largely of sandstone, the total thickness being about 50 ft.

Fifteen Foot Coal (Six Foot and Pinkie Three Foot; Jewel of Whitehill and Parrot Rough)

TheFifteen Foot Coal is now totally obscured at Joppa, but it is said to have been 12 ft 6 in. thick at that locality.

In Newcraighall Colliery, 330 yd E.S.E. of the pit-bottom the section of the coal and its associated roof metals is as follows:

South-south-east of Woolmet Colliery the Fifteen Foot Coal of Joppa was represented by two coals separated by 27 ft of strata. The lower coal, corresponding to the Six Foot Coal of Cowden and Pinkie, was 3 ft thick, and the upper seam, the Pinkie Three Foot, had the following section: coal 1 ft 3 in.; coaly blaes 6 in. on coal 4 in.

In Monkton House No. 37 Bore the Fifteen Foot Coal was 4 ft 4 in. thick.

In the Millstone Grit Mine at Gilmerton the Six Foot Coal occurred in two leaves, the upper being 2 ft 2 in. thick, and the lower 2 ft 8 in., with a 2 ft 4 in. parting. The Pinkie Three Foot Coal, which was 13 ft above the Six Foot Coal, had the following section: coal, banded 6 in.; coal, hard, 8 in.; coal, splint 10 in.; fireclay, coaly 1 in.; coal, cannel 7 in. on coal 6 in.

North-west of Eskbank the Jewel Coal of Whitehill is reported to be a good, clean coal about 2 ft 6 in. thick. The Parrot Rough Coal, 4 ft 6 in. to 19 ft 7 in. above the Jewel, varies from 1 ft 11 in. to 4 ft in thickness, and generally contains a seam of parrot coal.

In the Polton area the Jewel Coal of Whitehill varies in thickness from 2 ft 2 in. to 3 ft 2 in., and the Parrot Rough from 1 ft 10 in. to 3 ft 3 in. Bores near Midfield showed that the latter coal is of poor quality in that region, with impure parroty bands in the centre or near the bottom.

In the workings at Whitehill Colliery the Jewel Coal is generally about 2 ft 6 in. to 3 ft 1 in. thick, but an underground bore sunk just over a mile south-east of the pit showed that the seam was only 5 in. thick at that point. The coal appears to be missing in Broachrigg Farm No. 4 Bore, Stonefield Hill Farm No. 3 Bore and Aikendean Nos. 1 and 2 bores. The strata between the Jewel and Parrot Rough coals in the Whitehill area (Plate 5) consist mainly of fireclay and faky sandstone, and vary in thickness from 4 ft 5 in. to 12 ft. About 1000 yd E.S.E. of Whitehill Colliery Shaft the section of the Parrot Rough Coal was: cannel coal, coarse 6 in.; blaes, rooty 1 ft 9 in.; coal, free, with cannel ribs 2 ft 5 in.; fireclay 4 in. on coal 1 ft 7 in., and in Carrington No. 2 Bore the following section was seen: coal, bright 1 ft 10 in.; coal, parrot 6 in.; blaes, parroty 4 in. on coal, bright 8 in. To the east, however, near Carrington Barns Farm, the Parrot Rough Coal appears to thin out and disappear; in Aikendean No. 1 Bore a coal, possibly the Parrot Rough, was 1 ft 6 in. thick, 4 in. of dull, splinty, impure coal resting on 1 ft 2 in. of mainly bright, banded coal. In Aikendean No. 2 Bore there was no coal at the corresponding stratigraphical position.

There are no exposures of the Jewel Coal in the vicinity of Newbattle Abbey and it is possible that the coal is missing in that area. The Parrot Rough Coal is seen in the Mary Burn, 150 yd S.E. of the Abbey, where the section is : coal, mainly bright 1 ft 3 in. on coal, impure, parroty 6 in.

North-east of Dalkeith in Cowden Cleuch No. 5 Bore, 420 yd N.E. of Cowdenfoot, the section of the Six Foot Coal was: coal 4 ft; blaes 6 in.; coal 8 in.; blaes 5 in. on coal 9 in. About 18 ft of strata, mostly sandstone, separate the Six Foot Coal from the Pinkie Three Foot Seam, which generally occurs in two leaves as follows: coal 11 in.; sandstone 3 ft 2 in. on coal 1 ft 1 in.

Farther north in No. 9 Mine, Dalkeith Mines, near Smeaton, the Six Foot Coal, Pinkie Three Foot Coal and associated strata occur as follows:

The coals in the lower part of the Productive Coal Measures were formerly worked from several pits in the vicinity of Cowpits, but the old workings have been long abandoned. The Six Foot and Pinkie Three Foot seams are reported to have been respectively 4 ft 6 in. and 3 ft thick, separated by 9 ft of blaes.

At Pinkie the interval between the two seams is usually somewhat larger than at Cowpits :

Strata between the Fifteen and Nine Foot coals

The details of the strata between the Fifteen and Nine Foot coalsas seen on the shore at Joppa are:

At Newcraighall the Nine Foot Coal is separated from the Fifteen Foot Coal by 18 ft of strata, mainly sandstone and blaes, that include a well-known mussel band. The following section of the roof metals of the Fifteen Foot Coal was seen in a mine 330 yd E.S.E. of the pit-bottom: faky sandstone; blaes with ironstone ribs, bearing Carbonicola aff. communis, C. cf. pseudorobusta and C. sp. intermediate between communis and pseudorobusta 4 ft; fakes, grey with irony ribs 1 ft 10 in.; faky blaes 1 ft 4 in. on coal (Fifteen Foot). Specimens collected from this locality were discussed by Weir and Leitch (1936) and also formed the subject of a study by Leitch (1936).

In Monkton House No. 37 Bore there are 21 ft of strata between the two seams:

A mussel band also occurs above the Pinkie Three Foot Coal in the workings at Woolmet Colliery and in the. Millstone Grit Mine at Gilmerton Colliery; Carbonicola spp. (including elongate varieties of C. communis)have been found at Woolmet, and C. cf. pseudorobusta and C. sp.(cf.communis)at Gilmerton.

North-west of Eskbank the Jewel Coal of Whitehill lies about 5 ft below the Parrot Rough seam, and on the north bank of the River North Esk, 550 yd. W. of Elginhaugh Bridge, a band of ironstone nodules containing Spirorbis sp., Anthraconauta sp.and Carbonicola spp. was formerly exposed, about 15 ft above the latter coal.

A nodular ironstone rib containing Carbonicola sp.has also been found above the Parrot Rough Coal in the Broomieknowe railway cutting and in Polton Colliery but in the Whitehill area, where the beds between the two coals vary in thickness from 6 to 24 ft, no mussels have been recorded from the strata above the Parrot Rough, although fish scales have been found at several localities.

Mussels have also been found at the same horizon in the north-eastern part of the coalfield. In the Mary Burn, near Newbattle Abbey, the total thickness of intervening strata was about 8 ft, the details being:

At Dalkeith No. 9 Mine, the succession between the two coals is :

Recent boreholes in the northern central portion of the coalfield have also pierced the mussel band above the Fifteen Foot or equivalent coal. Thus at Esk Mouth Bore, grey mudstone 9 ft 6 in. above the seam yielded Carbonicola cf. communis and C. aff. pseudorobusta. The former fossil was also obtained at Dalkeith Nos. 48 and 49 bores which are situated respectively 660 yd N.E. of Dalkeith House and 850 yd S.E. of Sheriffhall Mains.

Nine Foot Coal (Barrs of Cowpits and Smeaton; Whitehill Splint)

Thesection of the Nine Foot Coal as formerly seen at Joppa was: coal 1 ft 1 in.; fireclay 2 ft on coal 5 ft 6 in. In Monkton House No. 37 Bore, the details of the seam were: coal 10 in.; fireclay and coal ribs 1 ft 7 in. on coal 4 ft 9 in., and, near the pit-bottom at Woolmet Colliery: coal 5 in.; fireclay 2 in.; coal 3 in.; fireclay and fakes 10 in.; coal, with splint ribs 1 ft 11 in.; fakes, parroty 2 in.; coal, splinty 1 ft 3 in. on coal, hard 1 ft 6 in.

South of the Sheriffhall Fault, in Glenesk Colliery No. 1 Bore the section was: coal 7 in.; blaes 3 in.; coal 1 in.; blaes 5 in. on coal, good splint 4 ft 2 in., and in the shaft at Polton Colliery the seam was reported to be a good coal, 3 ft 2 in. thick.

To the south, in the workings of Whitehill Colliery about half a mile south-east of the pit, the following section was seen: coal, free 7 in.; hard irony band, 1 in. to 3 in.; coal with splint ribs 3 in.; coal, hard, splint 11 in.; coal, hard, free 9 in.; coal, hard, splint 6 in. on coal, hard, free 8 in. The hard irony band, locally known as the 'bane' is a distinctive feature of the roof of the Splint Coal in some parts of the workings at Whitehill Colliery.

The coal is apparently missing at certain localities south of Whitehill, for it was not found in the Broachrigg Farm No. 4, Gourlaw Farm No. 5 or Aikendean Nos. 1 and 2 bores.

The Splint Coal crops out in the Mary Burn, near Newbattle Abbey, where it is at least 2 ft thick. A coal, also about 2 ft thick, which formerly cropped out in a little burn on the east side of the road, about 370 yd S.S.E. of Newbattle Bridge, was considered to be the Splint.

At Cowdenfoot the Nine Foot Coal occurs in two leaves: coal 1 ft 4 in.; fireclay, faky 5 in. on coal 4 ft 9 in., and in Dalkeith No. 9 Mine, the section was: coal, sclitty 2 in.; coal, free 9.5 in.; fireclay with coaly ribs and bands 1 ft 2.5 in.; coal, splinty 3 in.; coal, splint with bright bands 1 ft; stony ply 0.5 in.; coal, cannel 1 in. on coal, free 3 ft.

To the north, in Pinkiehill No. 1 Bore the coal was 3 ft 7 in. thick.

Strata between the Nine Foot and Salters coals

At Joppa, the strata between the Nine Foot and Salters coalsconsist of 33 ft of rapidly alternating sandstone, fakes and faky blaes, with some fireclays. About 8 ft above the Nine Foot Coal there are two thin blaes bands, 6 in. apart, containing Spirorbis sp., Anthraconauta cf. tenuioides Dewar, and A. spp.

A similar thickness is recorded at Newcraighall and Woolmet collieries, but in Monkton House No. 37 Bore the interval is just over 52 ft, and includes a sandstone 24 ft thick.

Anthraconauta cf. trapeziforma was found in blaes overlying the Nine Foot Coal in Castle Steads No. 38 Bore, put down about one and a quarter miles north-east of Dalkeith.

North-west of Eskbank the strata consist mainly of fakes and sandy fakes from 21 ft to 40 ft thick.

In the Polton and Whitehill areas the distance between the two equivalent seams (Whitehill Splint and Whitehill Rough) varies from 6 ft to 25 ft; where the interval is large the strata consist mainly of sandstone, with fireclay at the top.

Near Cowdenfoot, and at Smeaton and Pinkie the beds between the two seams are about 50 ft thick, and at Cowdenfoot they consist mainly of fakes and sandstone.

Salters Coal to base of Queenslie Marine Band

Salters Coal (Whitehill Rough)

AtJoppa the Salters Coal is reported to have occurred in two leaves: coal 2 ft; fireclay 4 ft on coal 2 ft.

The section seen in a rising mine east-south-east of the shaft at Newcraighall Colliery was: coal, with dirt plies 6 in.; coal 9 in.; fireclay, coaly 1 ft; fireclay 2 in.; coal 2 ft on coal, sclitty 1 ft; and the details proved in Monkton House No. 37 Bore were: coal, rather soft, with much fusain, 3 ft 1 in.; fireclay 6 in. on coal 5 in.

At Woolmet Colliery, in a rising mine near the pit-bottom the following section was seen: coal, free 4 in.; coal, splint 6 in.; coal, hard 1 ft 5 in.; coal, sclitty 1 in.; coal, free 5.5 in.; coal, dirty 1 in. on coal 6 in.

In the Millstone Grit Mine at Gilmerton Colliery, Salters Coal was of irregular thickness, for it was reduced to less than 1 ft in places by a washout. A representative section is: coal with splinty plies 1 ft 4 in.; coal, free 8 in. on coal, coarse 8 in.

In Glenesk Colliery No. 1 Bore the coal occurred in three leaves, as follows: coal, good, clean 5 in.; stone 1 in.; coal 1 ft 1 in.; stone and coaly blaes 2 in. on coal 1 ft 1 in. Bores in the vicinity of Midfield proved that the seam varied from 3 ft to 4 ft 2 in. in thickness.

The seam was 3 ft 6 in. thick in the shaft at Whitehill Colliery, and the section seen underground about one mile south-east of the pit was: coal, bright, clean 2 ft 9 in.; soft parting 1 in.; coal 7 in.; soft parting 1 in. on coal, bright and dull banded 1 ft 3 in. The coal appears to thin out in a south-easterly direction; in Carrington No. 2 Bore it was represented by a thin seam in two leaves, 9 in. apart, the upper being 3 in. thick, and the lower 7 in. Farther to the south-east, in Aikendean Nos. 1 and 2 bores, the coal was missing altogether.

Salters Coal crops out in the Mary Burn, near Newbattle Abbey, where it is at least 2 ft thick, and is overlain by a massive sandstone.

The seam is generally about 2 ft thick near Cowdenfoot and Smeaton, and about 1 ft 6 in. in the Pinkie area. In an underground bore, however, about one mile northwest of Dalkeith Mines the coal was missing.

Throughout the coalfield the beds between the Salters and Glass coals consist almost entirely of sandstone, mainly medium-grained, with coarse bands. At Joppa, Newcraighall and Woolmet their total thickness is about 60 ft, and in Monkton House No. 37 Bore the interval between the seams was 51 ft, including a sandstone 41 ft thick.

In the Millstone Grit Mine, Gilmerton Colliery, Salters Coal is overlain by a sandstone, reddish and purple in parts, with coarse bands, about 150 ft thick, which apparently cuts out the Glass Coal.

South of the Sheriffhall Fault the interval between the two equivalent coals (Whitehill Rough and Whitehill Great) is also mainly occupied by sandstone. The total thickness of intervening strata varies from 26 ft in the shaft at Polton Colliery to 114 ft in the underground workings of Whitehill Colliery, about one and an eighth miles south-east of the pit-shaft. Carbonicola pseudorobusta has been recorded from the roof of the Rough Coal in Eldendean (Eldindean) Pit, Polton Colliery (Weir and Leitch 1936, p. 732). The Great Seam at Whitehill Colliery is underlain by a fireclay, formerly used for the manufacture of bricks. In Dalkeith No. 9 Mine, a coarse-grained, current-bedded sandstone, about 40 ft thick, separates the two seams, and at Pinkie the interval between the coals is about 65 ft, but the details of the intervening strata are unknown.

Glass Coal (Whitehill Great)

AtJoppa the Glass Coal is said to have been 3 ft 7 in. thick.

In the rising mine in Newcraighall Colliery mentioned above the seam was poorly developed, being represented by 2 ft of coaly fakes and sclitty coal, and in Monkton House No. 37 Bore the coal was also thin: coal 1 ft 3 in.; carbonaceous blaes 6 in.; coaly blaes 1 in. on impure blackband ironstone with traces of ostracods 2 in.

At Woolmet Colliery, in the rising mine near the pit-bottom, the section was: coal 7 in.; coaly fakes 3.5-in.; coal 1 ft; fakes 9 in. on coal, 2 ft 6 in.

West of Eskbank the Glass Coal is very variable, the greatest recorded thickness being 2 ft. In Glenesk Colliery No. 1 Bore, however, the seam was missing.

Near Polton the coal usually occurs in several leaves, as shown in the journal of Whitehill No. 5/51 Bore: coal 4 in.; clay rock, brecciated 3 in.; coal 2 ft 1 in.; fireclay with thin coal ribs 1 ft 2 in.; coal 1 ft 1 in.; blaes, parroty 2 in.; coal, parroty 3 in.; coal and coaly blaes 1 ft 7 in.; on coal 1 ft 2 in.

In a surface mine at in.; Colliery the following downward section was seen : coal, coarse 2.5 in.; fireclay 11 in.; ironstone 1.5 in.; coal 8.5 in.; coal, splint 6.5 in.; coal, free 4 ft 3 in. Bores put down about one mile north-east of the colliery showed that the coal occurred in several leaves in that vicinity. The section found in one of these bores, Whitehill No. 9/52, was: coal 2 in.; clay rock, brecciated 3 in.; coal, splinty 1 ft; coal 7.5 in.; blaes, coaly 1 in.; coal 2.5 in.; blaes, coaly 3 in.; coal 1.5 in.; coal and foul coal 1 ft 7 in.; blaes, coaly 1.5 in. on coal, soft 2 ft 6 in. The seam is generally of better quality farther south, as was shown in bores sunk about one and a quarter miles east of Whitehill Colliery. Whitehill No. 3/51 Bore, at Shiel Bridge, proved the following section: coal 3 ft 5 in.; blaes, parroty 3 in.; blaes 1 ft 5 in. on coal 2 ft 7 in. The coal is occasionally absent, however, as was proved in Whitehill No. 14/52 Bore put down about 1100 yd E. of Whitehill House.

In Shewington No. 2 Bore, near the south end of the outcrop of Productive Coal Measures, the details of the coal were: coal 5 in.; clay rock, brecciated 4 in.; coal 3 ft 6 in.; fireclay 8 in.; coal 6 in.; fireclay 1 ft 6 in.; ironstone 4 in.; blaes, faky 1 ft 7 in.; coal 1 ft 11 in.; fakes, carbonaceous 2 in. on coal 1 ft.

Near Carrington, in Aikendean No. 1 Bore, a coal, thought to be the Glass Coal, had the following section: coal, foul 1 in.; fireclay 4 in.; Coal, bright 6 in. on coal, splint 3 ft.

No details are available regarding this coal in the Cowdenfoot area, but in Dalkeith No. 9 Mine, and at Pinkie, in Pinkie Mains No. 4 Bore, the thicknesses were 1 ft 7.5 in. and 1 ft respectively.

Beds between the Glass (Whitehill Great) and Cowpits Five Foot (Dalkeith Under) coals

Over most of the coalfield the beds between the Glass (Whitehill Great) and Cowpits Five Foot (Dalkeith Under) coals usually include a thick false-bedded sandstone with coarse bands. The details of the strata overlying the Glass Coal at Joppa are:

Neither the Quarry Coal nor the Cowpits Five Foot Coal is exposed at Joppa.

About 15 ft above the Glass Coal in the rising mine at Newcraighall Colliery there are two thin coals, separated by 4 in. of fireclay. They are overlain by 4 ft 9 in. of sandstone with thin fireclay bands, which in turn are succeeded by a massive current-bedded sandstone, 92 ft thick, which is coarse at the base and rests on an irregular surface. The Quarry Coal, 1 ft 1 in. thick, is separated from the massive sandstone by 6 ft of strata, mostly faky fireclay, with ironstone bands and balls; 4 ft 6 in. of faky fire-clay occupy the interval between the Quarry Coal and the overlying Cowpits Five Foot Coal.

In Monkton House No. 37 Bore the Glass Coal was overlain by 7 in. of black carbonaceous blaes with fish scales, succeeded by 8 in. of dark faky blaes with some irony bands and occasional traces of mussels. In this bore the interval between the Glass Coal and the Cowpits Five Foot Coal was about 116 ft. The lower 60 ft consisted mainly of sandstone, fakes and fireclay with thin coals, above which came a white and pale grey sandstone, medium-grained, with coarser bands, 46 ft thick. The Quarry Coal, 1 ft 4 in. thick, was separated from the Cowpits Five Foot Seam by 4 ft of fireclay and faky fireclay.

In the rising mine in Woolmet Colliery, mentioned earlier, the Glass Coal and the Cowpits Five Foot Coal are about 129 ft apart, the interval being occupied mainly by sandstone. The Quarry Coal is 1 ft 3 in. thick and lies 6 ft below the Cowpits Five Foot seam.

As already mentioned (p. 104) the Glass Coal seems to have been replaced by a sandstone in the Millstone Grit Mine at Gilmerton Colliery. In a rising mine running off this mine two thin coals, 3 ft apart, were noted, the lower being 154 ft above the Salters Coal. These coals are overlain by a sandstone, coarse in the lower part, 53 ft thick, succeeded by 28 ft of strata, mainly sandstone, faky fireclay and fireclay, with the Quarry Coal, 5 in. thick, 9 ft below the Cowpits Five Foot Coal.

North-west of Eskbank the distance between the Glass Coal and the Cowpits Five Foot Coal is about 120 ft and consists mainly of sandstone with fireclays in the lower part. In a bore near Polton Colliery the seams were separated by about 95 ft of strata, the lower 30 ft of which consisted principally of fakes, sandstone and fireclay, while the upper part included a grey, brown and white sandstone 55 ft thick. The Quarry Coal, 7 ft 4 in. below the Cowpits Five Foot, was 1 ft 5 in. thick.

In the shaft at Polton Colliery both the Cowpits Five Foot Coal and the Quarry Coal are absent; a fireclay, which underlies the probable position of the former coal occurs 112 ft above the Glass Coal.

To the south, the thickness of this group varies from about 70 ft near Whitehill Colliery to about 115 ft in Whitehill No. 3/51 Bore, 900 yd E.S.E. of Whitehill House. In the latter bore, the interval between the Whitehill Great and Cowpits Five Foot coals was occupied mainly by a thick sandstone, coarse-grained and pebbly in parts; the Glass (Whitehill Great) Coal was separated from the base of the sandstone by a few inches of fireclay, and the Quarry Coal, 15 ft below the Cowpits Five Foot Coal was represented by a seam 1 ft 9 in. thick. In Whitehill No. 9/52 Bore, the base of the thick sandstone was separated from the Glass Coal by about 23 ft of strata, mainly fakes and faky sandstone with a 5-in, coal near the top.

In the vicinity of Whitehill Colliery, where the distance between the coals is 70 ft, the thick sandstone found in the bores mentioned above is absent. The intervening strata consist mainly of sandstones, fakes and fireclays, with thin coals and coaly blaes bands; an interesting feature is the occurrence of a 5-in, band of faky blaes with ironstone ribs and mussels about 30 ft above the Glass Coal. Carbonicola commons and C. cf. robusta? (J. de C. Sowerby) have been found at this horizon. Near Carrington, in Aikendean No. 1 Bore a coal 1 ft 4 in. thick, considered to be the Cowpits Five Foot Seam, was found 86 ft above the Glass Coal; the intervening strata consisted mainly of medium and coarse-grained sandstone. Strata which probably lie between the Glass and Cowpits Five Foot coals are exposed at several localities in the River South Esk in the vicinity of Dalkeith. A massive, false-bedded, coarse yellow and red sandstone is seen in the river 800 yd S.W. of Newbattle Abbey, and farther downstream, between Benbucht Bridge and New Mills Bridge there are various exposures of reddish sandstone and purple and grey fakes with fireclays and thin coals.

The section seen in Dalkeith No. 9 Mine was very similar to that recorded in Monkton House No. 37 Bore. The Glass Coal was overlain by 60 ft of strata, mainly sandstone, fakes and fireclay, with thin coal ribs, succeeded by a massive current-bedded sandstone, coarse in the lower part, about 55 ft thick. The total thickness of strata between the Glass Coal and the Cowpits Five Foot Coal was 128 ft, and the Quarry Coal, 1 ft 9 in. thick, occurred 11 ft below the latter coal.

In the Esk Mouth Bore, a silty carbonaceous mudstone with irony layers near the base, at a depth of 994 ft, 2 ft above the Glass Coal, yielded macrospores, Anthraconauta cf. candela Dewar, and fish remains including Megalichthys?

Cowpits Five Foot Coal (Dalkeith Under)

In the north-western part of the coalfield the thickness of the Cowpits Five Foot Coal varies from 3 ft 9-in. to 4 ft 11 in. In the Monkton House Bore the seam consisted of 4 ft 3 in. of soft, bright and dull banded coal.

Near Eskbank, in Glenesk Colliery No. 1 Bore, the thickness was 2 ft 8 in. The coal was absent in the shaft of Polton Colliery, but a nearby bore recorded a good coal, 2 ft 6 in. thick.

To the south, in the Whitehill vicinity, the seam is generally thin and occurs in several leaves. In the surface mine at Whitehill Colliery the downward section was : coal, parrot with bright bands 6 in.; fakes, coaly 5 in.; fakes, parroty 5 in.; cannel 5 in.; fakes, coaly 2 in.; coal, mainly bright 1 ft 11 in., and in Whitehill No. 3/51 Bore the details were as follows: coal 1 ft 2 in. blaes, parroty 1 ft 10 in. on coal 9 in. To the east, in Aikendean No. 1 Bore the thickness was 1 ft 4 in.

A coal, formerly mapped as the Whitehill Rough Seam, which crops out on the left bank of the River South Esk, about 600 yd N.N.E. of Lothian Bridge, is now considered to be the Cowpits Five Foot Coal. Only about 11 in. of coal were visible when the exposure was visited in 1950, but in an earlier survey 2 ft 1 in. of coal were seen.

The thicknesses of the coal in the Smeaton and Cowpits areas are shown in (Plate 5). There are old workings in the Cowpits Five Foot Coal in the Inveresk area, but no details are available regarding its thickness.

Interval between the Cowpits Five Foot (Dalkeith Under) and Little Splint (Dalkeith Upper) seams

At Woolmet Colliery, in a mine about 600 yd E.S.E. of the pit-shaft, the interval between the Cowpits Five Foot (Dalkeith Under) and Little Splint (Dalkeith Upper) seamsis about 90 ft, and includes a sandstone 58 ft thick. The Cowpits Five Foot Coal was overlain in Monkton House No. 37 Bore by 25 ft of strata, mainly fakes and sandstone, succeeded by a sandstone 126 ft thick. The Little Splint Coal was missing, perhaps because of a washout either at the base of or within the thick sandstone.

About one mile south of Woolmet Colliery, in Todhills Farm No. 1 Bore, the distance between the coals was 77 ft, including a sandstone 30 ft thick.

Farther south the beds between the two coals consist almost entirely of sandstone. The thicknesses of the intervening strata as found in various bores were as follows: Hardengreen Farm: 99 ft; Whitehill No. 4: 60 ft; Whitehill No. 12: 65 ft and Gourlaw Farm No. 5: 88 ft.

In the vicinity of Smeaton 79 to 96 ft of measures separate the two coals. In Bore P 313, 430 yd S.W. of Dalkeith No. 9 Mine, the thickness was 79 ft 4 in., including a sandstone, nearly 30 ft thick, in the lower part.

The section seen above the Cowpits Five Foot Coal in Dalkeith No. 9 Mine was:

In Castle Steads No. 38 Bore, put down nearly a mile west-north-west of the above mine, Carbonicola cf. bipennis Trueman and Weir (non Brown) was found in a bed of blaes, 13 ft 6 in. above the Cowpits Five Foot Coal.

Little Splint Coal (Dalkeith Upper)

The Little Splint Coal, as stated above was not found in Monkton House No. 37 Bore. The section seen underground, 380 yd E.S.E. of Woolmet Colliery, was: coal, splint 1 ft 9 in.; coal, hard 1 ft 2 in. on coal, sclitty 3 in.

Farther south, in Todhills Farm No. 1 Bore the seam was only 1 ft 10 in. thick, including some dirt plies, and in a bore near Ironmill, a quarter of a mile north-east of Eskbank station, the thickness was 2 ft 4 in.

In the area immediately south of Eskbank the coal is generally about 3 ft thick; the section recorded in a bore 170 yd W.N.W. of Hardengreen Farm was: coal, soft 7 in.; coal, hard 2 ft 3 in. on coal, soft 2.5 in.

In Whitehill Nos. 4 and 12 bores the coal occurred in several leaves, as shown in the journal of No. 12 Bore: coal 2 ft 7 in.; fireclay 6 in.; coal 6 in.; fireclay 1 in.; coal 1 ft 2 in.; fireclay 1 ft on coal 9 in. To the south-west of these bores, in Gourlaw Farm No. 5 Bore, a coal, thought to be the Little Splint, had the following section: coal 1 ft; fireclay 1 ft 6 in. on coal 3 in.

Thicknesses of the Little Splint (Dalkeith Upper) Coal in the north-eastern part of the coalfield are given in (Plate 5).

Strata between the Little Splint Coal and the Queenslie Marine Band

Details of the strata between the Little Splint Coal and the Queenslie Marine Band were recorded in Todhills No. 1 Bore (Plate 5). The coal was overlain by 52 ft 5 in. of strata, mainly consisting of fakes, faky sandstone and sandstone in the lower part and fireclay and sandstone above. These beds were succeeded by 4 ft of fireclay, faky at the base, on which rests a 1 ft 1 in. coal, which directly underlies the marine band.

Queenslie Marine Band to base of Splint Coal

Queenslie Marine Band

Therecognition, in the middle of the Productive Coal Measures of Scotland (Manson 1957) of a marine horizon widely known in England and Wales, is of great stratigraphical importance. The marine band, called the Queenslie Marine Band, is now known as a Lingula band at several places in Midlothian and its discovery not only allows detailed correlation to be made with greater certainty within the coalfield itself but makes much wider comparison possible.

As already noted the Queenslie Marine Band was found at Todhills No. 1 Bore where it consisted of 2 ft 4 in. of fine-grained dark blaes with small Lingula in the upper part. It has also been recently found in Monkton House No. 37, Castle Steads No. 38, Esk Mouth and Dalkeith No. 49 boreholes. In the first-mentioned bore the Little Splint Coal was absent and the marine horizon, consisting of blaes with Lingula mytilloides J. Sowerby, occurred about 182 ft above the Cowpits Five Foot Coal, the intervening strata being mainly sandstone. The section of the marine band and the associated strata found in Castle Steads No. 38 Bore was as follows:

The pavement of this coal lay about 60 ft above the pavement of the Little Splint Coal.

At Esk Mouth Bore, the Queenslie Marine Band occurred at a depth of 650 ft 8 in. and consisted of 6 ft 8 in. of silty mudstone containing Rectocornuspira?, sponge spicules and Lingula mytilloides.

A recent bore 850 yd S.E. of Sheriffhall Mains, known as Dalkeith No. 49 encountered the marine band at 730 ft. The slightly silty mudstone yielded foraminifera including Rectocornuspira?, Lingula mytilloides and fish debris.

In a bore near Ironmill, Dalkeith, a 4-in. coal, associated with a thin limestone and limy beds was found about 70 ft above the Little Splint Coal and probably represents the coal below the Queenslie Marine Band (p. 96). The intermediate beds contained a sandstone, 45 ft thick, which was coarse and pebbly in places.

Measures between the Queenslie Marine Band and the Musselburgh Jewel Coal

The measures between the Queenslie Marine Band and the Musselburgh Jewel Coal locally include a seam known as the Golden Coal. In the Newcraighall–Millerhill–Sheriff hall region the Golden Coal, ranging in thickness from 1 ft 8 in. to 2 ft 6 in., occurs about 40 ft below the Mussel-burgh Jewel Seam (Milne 1839). One of the coals recorded in the section of Woolmet Colliery Shaft was formerly thought to be the Golden (Gibson and Bailey in Peach and others 1910, p. 258) but is now considered to be part of the Musselburgh Jewel; the true Golden is probably the 2-ft seam 38 ft lower in the succession.

The succession between the Queenslie Marine Band and the Musselburgh Jewel Coal recorded in the Todhills No. 1 Bore was as follows, the Golden Coal apparently being absent unless represented by the 2-in. seam:

In Bore P 313 on the east side of the coalfield near Smeaton (Plate 5), the interval between the Little Splint Coal and the Musselburgh Jewel Coal was about 220 ft, with a 90-ft sandstone in the lower part, but the Queenslie Marine Band was not recognized. The Golden Coal, 46 ft below the Musselburgh Jewel Coal, occurred in two leaves: coal 1 ft 6 in.; blaes 7 in. on coal 11 in.

The Golden Coal and the coals above are only found in the area north of the Sheriffhall Fault.

Musselburgh Jewel Coal

The thickness of the Musselburgh Jewel Coal varies from 2 ft to 6 ft; in Pinkie Salt Works No. 3 Bore and Olivebank No. 2 Bore the seam occurred in leaves, the sections being respectively: coal 10.5 in.; faky rib 4 in.; coal 1 ft 5.5 in.; blaes rib 2 in. on coal 1 ft, and coal, clean 2 ft 4 in. on coal, with ribs 2 ft 4 in.

Strata between the Musselburgh Jewel and Beefie seams

The thickness of strata between the Musselburgh Jewel and Beefie seams was about 130 ft in the Pinkie Salt Works No. 3 Bore (Figure 16) on the north-west side of the coalfield, 66 ft in Rothesay Place No. 4 Bore, Musselburgh, and 61 ft in Dalkeith No. 49 Bore, just over half a mile north-west of Dalkeith. In the first-mentioned bore and at several other localities in the north-western part of the coalfield the interval includes a thick sandstone. Several coal seams are usually present in the intervening measures, and one of these, the Diamond Coal (see below), is of workable thickness in certain localities.

Fossiliferous, dark grey, slightly silty mudstone 7 ft above the Musselburgh Jewel Coal at Esk Mouth Bore yielded Spirorbis sp., indeterminate lamellibranchs, and fish remains. Immediately above this band, in light to medium grey mudstone were found Spirorbis sp., Anthraconaia or Anthracosia sp., Anthracosia aff. aquilina (J. de C. Sowerby), A. disjuncta Trueman and Weir, A. cf. nitida (Davies and Trueman), A. aff. ovum, A. cf. subrecta Trueman and Weir, A. sp. cf. caledonica Trueman and Weir, A. sp., intermediate between aquilina and ovum, A. sp., intermediate between phrygiana (Wright) and ovum, and Naiadites cf. carinatus (J. de C. Sowerby).

A further 79 ft higher, at 400 ft 3 in., grey mudstone with clay ironstone carried Anthracosia? and Anthracosphaerium turgidum (Brown).

At 359 ft in Monktonhall No. 2 Shaft, about 13 ft above the Musselburgh Jewel Coal, Anthraconaia cf. salteri (Leitch) and Naiadites cf. productus (Brown) were found in dark irony mudstone. In No. 1 Shaft, only Spirorbis sp., fragments of lamellibranchs and fish remains were recovered, in this case about 5 ft above the coal, with Naiadites sp.2 ft higher.

Fish remains and fragments of non-marine lamellibranchs were found in the roof-metals of the Musselburgh Jewel Coal in Bore P 313, put down half a mile south-southwest of Smeaton Farm, the details being:

Fish remains are reported from the roof shale of the Musselburgh Jewel Coal at an old pit about three-quarters of a mile south-south-east of this bore (Clough and Anderson in Peach and others 1910, pp. 262–3; Traquair 1903, p. 697).

Diamond Coal

The Diamond Coal was worked in the vicinity of Monktonhall, south-west of Musselburgh, where the seam was about 3 ft thick and lay approximately 33 ft above the Musselburgh Jewel. The coal waste found 200 ft above the Little Splint Coal in the shaft at Woolmet Colliery was formerly thought to be that of the Musselburgh Jewel, but now seems more likely to be the waste of the Diamond.

Measures between the Diamond and Beefie coals

In the Inveresk Water Bore (Figure 16) two mussel bands were found in the measures between the Diamond and Beefie coals; the details of the section are:

In Rothesay Place No. 4 Bore, Musselburgh, a bed of blaes with fragments of shells resembling Naiadites was found 45 ft above the Musselburgh Jewel Coal waste. This mussel band probably corresponds to the band above the 2-ft coal in the Inveresk Water Bore.

A bed of blaes with ironstone nodules 12 ft below the Beefie Coal in Castle Steads No. 38 Bore was found to contain ?Anthracosphaerium cf. propinquum (Melville).

Beefie Coal

As can be seen from (Figure 16) the Beefie Coal is of variable thickness, and in certain areas is reduced to a few inches. The maximum recorded thickness is 6 ft, in the Craighall region. In the Inveresk Water Bore, where the coal was 3 ft thick, the upper part was a clean strong splint, and the lower part contained splint bands. In Olivebank No. 2 Bore the section was: coal 1 ft 8 in.; fireclay 9.5 in.; coal 5.5 in.; coaly blaes 2.5 in. on coal 9.5 in.

The coal lying about 237 ft above the Little Splint in the shaft of Woolmet Colliery (Plate 5) is now taken as the Beefie and not the Diamond as heretofore (Gibson and Bailey in Peach and others 1910, p. 258).

Interval between the Beefie and Rough coals

In the Musselburgh area the interval between the Beefie and Rough coalsis generally about 70 ft and includes a thick sandstone. The following fossils were collected from above the Beefie Coal at Balaclava Old Pit, Shawfair, about two miles north-west of Dalkeith: Anthracosia cf. aquilina, A. cf. aquilinoides (Chernyshev), A. cf. phrygiana and Naiadites cf. productus.

At Monktonhall No. 1 Shaft Anthraconaia sp., Anthracosia cf. nitida, A. cf. phrygiana and fish remains including Platysomid scales, Rhabdoderma sp., and Rhizodopsis sp.were collected from dark grey mudstone about 5 ft 6 in. above the Beefie Coal.

Rough Coal

The variations in thickness of the Rough Coal are illustrated in (Figure 16). In both Pinkie Salt Works No. 3 Bore and Olivebank No. 2 Bore the seam occurred in three leaves, the section in the former bore being: coal 11.5 in.; fireclay 7 in.; coal 10.5 in.; fireclay 3 in.; blaes, coaly 5 in.; faky rib 1 in. on coal 1 ft 2.5 in. At Inveresk Water Bore, the coal was recorded as being 4 ft 6 in. thick, but the core was all ground away and the details of the seam are unknown.

Strata between the Rough and Splint coals

The strata between the Rough and Splint coals, which in the north-western part of the coalfield include a thick sandstone, range in thickness from 25 ft to 63 ft. In the Inveresk Water Bore (Figure 16) the Rough Coal and the Splint Coal were separated by 44 ft of strata, mainly grey fakes and blaes with thin beds of sandstone near the base.

Splint Coal to base of Barren Red Measures

Splint Coal

The thickness of the Splint Coal ranges from 5 ft 9 in. in Pinkie Salt Works No. 3 Bore to 4 ft 7 in. in Olivebank No. 2 Bore. The available evidence suggests that the seam is thickest on the west side of the coalfield and thins eastwards. In Dalkeith No. 48 Bore the position of the Splint Coal was occupied by 4 in. of streaky pale grey-green argillaceous limestone with coal partings up to 0.5 in. thick (p. 96).

Beds between the Splint and Clayknowes coals

The beds between the Splint and Clayknowes coals, which range in thickness from 303 ft in the Craighall area to 149 ft in the Smeaton–Dalkeith region, contain a large proportion of red and grey sandstone. The details of the strata immediately above the Splint Coal in Monkton House No. 37 Bore were:

The blaes above the Splint Coal in the Craighall area and at Smeaton is said to have contained a bed of mussels, and a 1-in. mussel rib was also recorded above this coal in Olivebank No. 1 Bore. In Dalkeith No. 48 Bore the impure limestone representing the Splint Coal was immediately overlain by a very pale creamy, limy marl, 8 in. thick, succeeded by pale grey and purple-grey, limy blaes and faky blaes, 2 ft 5 in. thick. Dark mudstone about 9 ft above the Splint Coal at Esk Mouth Bore, Musselburgh, yielded Calamites sp., Spirorbis sp.,? Anthraconaia oblonga (Wright), Anthracosia? and indeterminate ostracods (Carbonita?). From a depth of 54 ft 4 in. at Monktonhall No. 1 Shaft Anthraconaia cf. pulchra (Wright non Hind) was collected.

A band of ironstone nodules containing mussels, lying between the Splint Coal, and the Clayknowes Coal, was found in a trench 310 yd W. 22° N. from Longthorn Farmhouse, about one and a half miles north-west of Dalkeith; the faunal list is as follows: Anthraconaia cf. librata (Wright), A. sp.intermediate between librata and cymbula (Wright), Anthracosia cf. atra (Trueman), A. cf. concinna (Wright), A. sp.(? near similis Hind pars), Naiadites sp.

An indeterminate lamellibranch (Anthracosia?)and ?Naiadites cf. productus were collected from a position about 110 ft above the Splint Coal during the sinking of Olivebank Pit. At about this horizon at a depth of 213 ft 8 in. in dark mudstone with irony layers at Dalkeith No. 49 Bore, 850 yd S.E. of Sheriffhall Mains Spirorbis sp., Anthracosia aff. atra,? Anthracosphaerium radiatum (Wright), Naiadites cf. angustus Trueman and Weir, Carbonita sp.and Elonichthys sp.were collected.

About 136 ft above the Splint Coal at Esk Mouth Bore, Musselburgh, at a depth of 143 ft 6 in. in reddish stained mudstone, Anthracosia cf. caledonica Trueman and Weir occurs.

Clayknowes Coal

The maximum recorded thickness of the Clayknowes Coal is 3 ft 6 in. in the Smeaton–Dalkeith area; in Dalkeith No. 48 Bore, however, the seam was represented by 4 in. of pale brown streaky impure limestone, with thin coaly partings ((Figure 16) and p. 96). At the north end of the coalfield, in Olivebank No. 1 Bore, 2 ft 8 in. of dirty coal were found.

Strata occupying the interval between the Clayknowes Seam and Skipsey's Marine Band

In Dalkeith No. 48 Bore the strata occupying the interval between the Clayknowes Seam and Skipsey's Marine Band were 105 ft 10 in. thick, and the general succession was as follows:

In Dalkeith Park, on the south bank of the River North Esk, Skipsey's Marine Band is underlain by a coal which varies in thickness from 8 in. to 15 in. Another seam, 11 in. to 15 in. thick, was formerly seen 36 ft lower in the succession. Strata between this coal and the Clayknowes Coal, grey, brown and red sandstones with occasional fireclays and thin coal seams, are exposed further downstream, in the vicinity of the junction of the rivers North and South Esk, and in the River Esk, south-east of Castle Steads Farm.

In Dalkeith No. 49 Bore, put down in 1955, 910 yd E.N.E. of Sheriffhall, two Lingula bands, about 1 ft apart, were found, the lower being approximately 20 ft below Skipsey's Marine Band.

Skipsey's Marine Band

Thereare good exposures of Skipsey's Marine Band on the south bank of the River North Esk, 250 yd upstream from the junction of the rivers North and South Esk. The details of the section vary from exposure to exposure, but the following is a representative section: limestone, cone-in-cone, lenticular 6 in.; blaes, dark purplish, marine fossils 1 ft; limestone, hard, dark, impure, marine fossils 2 in.; blaes, faky, dark, micaceous, marine fossils 10 in.; blaes, purplish 2 in. on coal.

The fauna collected many years ago from dark 'limestone' and silty calcareous mudstone or micaceous mudstone has been re-examined and yielded the following forms: Lingula sp., Orbiculoidea?, Chonetes skipseyi Currie, Productus (Productus)carbonarius de Koninck, P. (Dictyoclostus) craigmarkensis? Muir-Wood, cf. Schuchertella pratteni (McChesney), S.?, Huanghoceras [Metacoceras] costatum (Hind), coiled Nautiloid, Hindeodella sp., Idiognathodus cf. delicatus Gunnell, Ozarkodina sp., Streptognathodus sp., undetermined platformed conodonts and fish remains including Rhizodopsis sp.

In Dalkeith No. 48 Bore, the details were: faky blaes, purple, passing down into dark blaes with thin irony ribs, scarce Lingula and lamellibranchs 8 ft 8 in.; limy rib, dark grey 1 in.; blaes, dark grey with occasional marine fossils 2 ft 6 in. on limestone, dark grey, fine-grained, with occasional fragments of obscure shells 11 in.

Some doubt exists about the horizon of a limestone in the River North Esk, 250 yd N.N.E. of Dalkeith House (p. 114) and perhaps at this level.

Barren Red Coal Measures

The base of the Barren Red Coal Measures is taken immediately above Skipsey's Marine Band.

Lithological characters

The reddish and purplish colour which characterizes most of the Barren Red Coal Measures is due to the presence of ferric oxide. Ironstone balls and ribs, originally composed of siderite, have been oxidized to deep red haematite and many of the sandstones contain small red spots, which are probably haematitic pseudomorphs after sphaerosiderite. The process of oxidation has altered the character of some of the fine-grained sediments, and most of the beds described as marl in the journal of Dalkeith No. 48

Bore (p. 114) were probably originally either blaes or fireclay; the bedding of the blaes has often completely disappeared, and in fireclays all the carbonaceous material has been removed, leaving only the impressions of rootlets. The destruction or alteration of coals has already been mentioned (p. 96).

Reddened beds of Carboniferous age have been described and their origin has been discussed by several authors, including Bailey (1926) and Trotter (1939, 1953a, 1953b, 1954). The reddening is thought to have taken place in a semiarid climate during the Carboniferous–Permian interval, when periods of drought allowed air to penetrate far down below the pre–New Red Sandstone land-surface (Bailey 1926). Trotter (1953b, 1954) considers that the depth to which these beds have been reddened by oxidation was controlled by the level of the pre–New Red Sandstone water-table.

Outcrop

The Barren Red Coal Measures occupy a small area to the north of Dalkeith and it is calculated that they occur beneath drift in the western part of Musselburgh.

Details

The character of the Barren Red Coal Measures was well seen in Dalkeith No. 48 Bore, which passed through about 280 ft of these measures. The following is a condensed journal of part of this bore:

Good exposures are to be found in the rivers North and South Esk in Dalkeith Park, immediately north of Dalkeith, where the general dip is in a southerly direction at angles ranging from 7 degrees to 18 degrees.

In the strata mapped as Barren Red Coal Measufes in Dalkeith Park there would seem to be at least two dark, earthy carbonaceous limestones. The lower one, ranging in thickness from 4 in. to 6 in., is exposed in the River North Esk about 750 yd N. of Dalkeith House and is perhaps in the same stratigraphical position as the 6-in. bed of blaes with ribs of calcite found about 194 ft above Skipsey's Marine Band in Dalkeith No. 48 Bore.

The, apparently, higher carbonaceous limestone is seen in the River North Esk, 250 yd N.N.E. of Dalkeith House and 100 yd N. of Montague Bridge, on the south side of an east-west fault. In a red sandy shale which cropped out about 50 yd N. of Montague Bridge H. B. Maufe detected marine fossils (Clough in Peach and others 1910, pp. 272–3).

In the revised six-inch map it was assumed that the fault mentioned above has no appreciable throw, and that these marine beds lie approximately 380 ft above Skipsey's Marine Band. Recently some doubt has been thrown on this interpretation. The locality has been re-examined and an excavation which was made on the right bank of the river about 60 yd N. of Montague Bridge gave the following section in descending order:

Maufe's specimens probably came from the lowest beds of the above section and contained in addition Aviculopecten?.

On palaeontological grounds there are reasons for believing that the fauna is that of Skipsey's Marine Band. All the fossils listed are known from that band or from the equivalent horizon in English or Welsh coalfields. The characteristic Skipsey's band brachiopods Chonetes skipseyi and Dictyoclostus craigmarkensis found in the exposure of Skipsey's Marine Band 250 yd upstream from the junction of the rivers North and South Esk (p. 113) are, however, absent; this is perhaps because the 'limestone' lithology of which they are characteristic is not represented.

To sum up, there remains some uncertainty as to the stratigraphical position of the exposures, but the palaeontological evidence affords no positive indication of the presence of a marine band higher than Skipsey's in the Midlothian Coalfield. W.T., H.S.W.

Palaeontology

The faunas of the Coal Measures of the Midlothian Coalfield are distinctly poor, and despite intensive search of available sections at outcrop and underground, the results have been disappointing. The paucity of non-marine shells was noted by Weir and Leitch (1936, p. 731), although they were able to establish the presence of the Carbonicola communis Zone and the lower part of the Anthracosia similis and Anthraconaia pulchra Zone. The additional material now available proves the presence of the intervening Anthraconaia modiolaris Zone although there is insufficient faunal evidence to indicate firm zonal boundaries (Figure 15). The recognition of the Queenslie Marine Band in the A. modiolaris Zone, however, provides an important line for correlation within the coalfield and also with adjacent coalfield areas.

There is as yet no evidence in Midlothian of the marine faunas frequently found in the Anthraconaia lenisulcata Zone unless indeed they are represented by the marine band above the Seven Foot Coal or by the bands in the upper part of the Roslin Sandstone Group, from none of which have goniatites been recovered.

In the Productive Coal Measures, as mapped, the non-marine faunas above the Pinkie Four Foot and the Fifteen Foot coals, characterized by forms allied to Carbonicola pseudorobusta and C. communis clearly belong to the C. communis Zone (Leitch 1936). This zone in fact appears to embrace the strata for some distance above the Glass Coal where Anthraconauta cf. candela, Carbonicola communis and C. robusta? have been found, but the boundary between this zone and the succeeding A. modiolaris Zone is ill-defined.

The presence of the latter zone is suggested by the fauna from above the Cowpits Five Foot Coal, which includes Carbonicola cf. bipennis, C. oslancis? and allied forms.

The recognition of the Queenslie Marine Band, of A. modiolaris Zone age, is of importance, though the fauna obtained from it is disappointingly meagre (p. 108). In strata a few inches above the marine band Anthracosia cf. ovum was found.

The fauna above the Musselburgh Jewel Coal includes Anthraconaia cf. salteri and Anthracosia spp.of the aquilina-ovum group, indicating the upper A. modiolaris Zone. The upper limit of this zone is not well defined though shells from above the Beefie Coal are believed to be from an horizon close to the boundary between the A. modiolaris and the similis-pulchra zones including as they do aquilina-and phrygiana-like forms of Anthracosia as well as Naiadites productus. The measures between the Splint and Clayknowes coals carry a fauna which is evidently of Lower similis-pulchra Zone age, including Anthracosia allied to atra and concinna, as well as Anthraconaia cf. librata and a form between librata and cymbula. Anthracosia cf. caledonica has been found about 136 ft above the Splint Coal and is probably the highest mussel fauna yet proved.

Skipsey's Marine Band carries the characteristic brachiopod Chonetes skipseyi and a specimen believed to be Productus (Dictyoclostus) craigmarkensis. In addition, Productus (Productus) carbonarius and an Orthotetid compared with Schuchertella pratteni are recorded, both of which appear to be new records for Skipsey's Marine Band, though they are known in the equivalent beds in certain English and Welsh coalfields. Conodonts are common, as usual at this horizon.

The possibility of a marine band higher than Skipsey's occurring near Dalkeith is discussed on p. 114. The palaeontological evidence is consistent with the exposure in question being a representative of Skipsey's Marine Band brought in by faulting. M.A.C.

References

BAILEY, E. B. 1926. Subterranean Penetration by a Desert Climate. Geol. Mag., 63, 276–80.

CLOUGH, C. T., WILSON, J. S. G., ANDERSON, E. M., and MACGREGOR, M. 1920. The Economic Geology of the Central Coalfield of Scotland, Area VII. Mem. Geol. Surv.

CLOUGH, C. T., HINXMAN, L. W., WRIGHT, W. B., ANDERSON, E. M., and CARRUTHERS, R. G. 1926. The Economic Geology of the Central Coalfield of Scotland. Area V. 2nd edit. (with additions by M. Macgregor). Mem. Geol. Surv.

DRON, R. W. 1905. The Occurrence of Calcareous Coal in a Lanarkshire Coalfield. Trans. Inst. Mining Eng., 27, 92–6 and 241–5.

FLETT, J. S. 1929. In Sum. Prog. Geol. Surv. for 1928, pt. 1.

LEITCH, D. 1936. The Carbonicola Fauna of the Midlothian Fifteen Foot; a Study in Variation. Trans. Geol. Soc. Glasgow, 19, 390–403.

MANSON, W. 1957. On the Occurrence of a Marine Band in the Anthraconaia modiolaris Zone of the Scottish Coal Measures. Bull. Geol. Surv. Gt. Brit., 12, 66–86.

MYKURA, W. 1956. Proc. Geol. Soc. No. 1541, pp. 124–5.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

STRAHAN, A. 1901. On the Passage of a Seam of Coal into a Seam of Dolomite. Quart. J. Geol. Soc., 57, 297–306.

TRAQUAIR, R. H. 1903. On the Distribution of Fossil Fish-remains in the Carboniferous Rocks of the Edinburgh District. Trans. Roy. Soc. Edin., 40, 687–707.

TROTTER, F. M. 1939. Reddened Carboniferous Beds in the Carlisle Basin and Edenside. Geol. Mag., 76, 408–16.

TROTTER, F. M. 1953a. Exploratory Borings in South West Lancashire. Trans. Inst. Mining Eng., 112, 261–83.

TROTTER, F. M. 1953b. Reddened Beds of Carboniferous age in north-west England and their origin. Proc. Yorks. Geol. Soc., 29, 1–20.

1954. Reddened Beds in the Coal Measures of South Lancashire. Bull. Geol. Surv. Gt. Brit., 5, 61–80.

WEIR, J., and LEITCH, D. 1936. The Zonal Distribution of the Non-marine Lamellibranchs in the Coal Measures of Scotland. Trans. Roy. Soc. Edin., 58, 697–751.

Chapter 8 Igneous rocks

Igneous rocks are remarkably scarce in the coalfield. Olivine-basalts of Calciferous Sandstone age are known, most of them being extrusive (p. 10) but others near Carlops (p. 11) and in Currie Glen (Figure 4) showing apparently intrusive relationships. In the latter case the basalt has been mapped as a dyke occupying a fault-plane, though it may in fact be a faulted part of the Currie Glen lava (p. 11).

The remainder of the intrusions are quartz-dolerite dykes. A group of these dykes, at least six in number, is present in the northern part of the coalfield (Figure 18). These intrusions, regarded as Permo-Carboniferous in age, have a general east-west trend, although in some places their direction is more nearly east-north-east or east-south-east. The coal seams are burnt alongside the dykes and the igneous rock is bleached and has been altered to 'white trap' where it has come in contact with coal. At one locality it was found that a dyke occupied a fault-plane; elsewhere no displacement of the seams has occurred along the line of a dyke.

Three dykes have been passed through in undersea workings from Prestongrange Colliery (Figure 4) and the adjacent Prestonlinks Colliery. The most northerly was cut by two mines about two and a quarter miles north of Prestongrange Colliery and in one of these the dyke extended for about 275 ft along the mine and included two near-vertical inclusions of baked sediments, one about 15 ft thick and the other 1 ft to 3 ft in width. The whin appeared to occupy a fault-plane and the beds on the north side of the dyke were found to be about 56 ft higher in the succession than those on the south side. A dyke and a fault, presumably continuations of those encountered in the mine just described, were passed through in another mine three-quarters of a mile to the east-north-east. There the dyke was 170 ft thick and the fault, which lay a short distance to the north had a northward downthrow of over 600 ft.

About three-quarters of a mile to the south another dyke, ranging in thickness from 40 ft to 160 ft, was encountered, and just over half a mile farther south another, about 100 ft thick, was met. In the undersea workings north of Prestongrange Colliery the three dykes described above have a west-south-west trend.

On the shore north of Prestongrange Colliery there is an outcrop of a fourth east-west dyke, over 100 ft wide in places, and what is probably the same intrusion was passed through just north of Musselburgh in undersea workings of Newcraighall Colliery. A little over three-quarters of a mile farther south a 100-ft dyke was met with in the workings of Wallyford Colliery (Figure 4), and in one part of this pit a 10-ft dyke was present a short distance to the south of the main dyke. Near Newhailes House, two and three-quarters of a mile west of Wallyford, a dyke, trending west-north-west and possibly a continuation of the Wallyford 100-ft dyke, was penetrated in mines from Newcraighall Colliery.

Farther westwards an east-west dyke is exposed in the Brunstane Burn near the viaduct north-west of Brunstane House, where about 7 ft of quartz-dolerite is seen, and a parallel dyke, about 100 yd farther south was said to have been met with in the workings in Niddrie Collieries. Just over half a mile west of the exposure in the Brunstane Burn a dyke, 28 ft thick, was found in a sewer-tunnel; this intrusion is possibly a continuation of one of the Brunstane dykes.

Chapter 9 Structure

Introduction

The Midlothian Coalfield is a structural basin, the present shape of which bears but little relation to the original basin of deposition as suggested by a study of the isopachyte maps (Figure 7), (Figure 10), (Figure 13). From these maps the present southern margin appears to be nearest to an original limit of deposition, a suggestion which is supported by the apparent overlap of the lower groups of the Carboniferous at the south-western end of the basin (p. 8). The broad structure is an asymmetrical syncline gently pitching to the north-north-east. It is bounded on the west by the Pentland Fault which separates it from the anticline of the Pentland Hills and on the east by the D'Arcy–Cousland Anticline and the Leadburn Fault and Herbershaw Anticline. Along the western limb of the syncline the dips are steep and occasionally inverted whilst the dips on the eastern limb are moderate. Details of the structure of the coalfield are shown on a contour map based on observed or calculated levels in the Great Seam of the Limestone Coal Group supplemented by others in the Nine Foot Coal of the Productive Coal Measures (Figure 17). The principal folds and faults are shown diagrammatically in (Figure 18).

Folding

The broad synclinal fold of the Midlothian Coalfield (Figure 18) is in reality a compound structure. The axis of a major syncline, here called the Main Syncline, extends south-south-westwards from Musselburgh to the Vogrie Fault south of Roslin. On the north-western flank of this fold there are several minor folds.

South of the Vogrie Fault two synclines can be clearly recognized. The principal one, known as the Penicuik Syncline, also with minor corrugations on its north-western side, extends from the fault south-westwards towards West Linton. A less well-defined, broadly synclinal area, the Rosebery Syncline, forms the south-eastern portion of the coalfield. The Rosebery Syncline is separated from the Penicuik Syncline by the Herbershaw Anticline and Leadburn Fault and is bounded on the east by the Halkerston Fault with its accompanying synclinal fold.

The Main Syncline

The Main Synclinelies between the Pentland Fault and the D'Arcy–Cousland Anticline and is bounded to the south by the Vogrie Fault. It is a composite syncline consisting of three main parts (Figure 19):

1. The steep western limb is highly inclined and in places even overturned. Inverted Coal Measure strata are found at Newcraighall (Figure 4) while between Niddrie and Gilmerton dips of 80 degrees or more eastwards are common in the Limestone Coal Group. At depth the beds forming the steeply inclined western limb bend abruptly in monoclinal manner to form the flat or gently dipping wide central part of the syncline. Thus in the Great Seam the change from steep to gentle dips occurs at Niddrie at about — 2300 ft O.D., at Burghlee at about —1000 ft O.D. and in Roslin Colliery workings at about —200 ft O.D.
2. The eastern limb has westerly dips of up to 38 degrees; between Newtongrange and Arniston there is again a fairly sharp transition from these moderately steep beds to the gently dipping beds of the central part of the syncline.
3. In the central part where there are a number of lesser undulations or minor folds the dips are often less than 10 degrees. The trends of the main synclinal axis and the minor fold-axes vary from north to north-east.

Penicuik Syncline

The Penicuik Synclineis bounded on the west by the Pentland Fault and on the east by the Leadburn Fault and the Herbershaw Anticline. It forms a smaller version of the Main Syncline with steep, occasionally inverted, dips along the western limb, gentle dips in the centre and moderate dips along the eastern limb. There is, indeed, more than a suggestion of two synclinal axes (Figure 17), (Figure 18). Minor folds are common along the western limb. Examples are those mapped in the Upper Limestone Group near Penicuik House and those near Carlops where the Lower Limestone Group and Calciferous Sandstone crop out close to the Pentland Fault. Inversion of the western limb of a syncline is seen in the ground west of Newhall House, Carlops.

Rosebery Syncline

The Rosebery Syncline is a shallow gentle fold between the Herbershaw Anticline and the Halkerston Syncline and Fault. Dips in it are rarely more than 6 degrees. North of the Vogrie Fault the syncline is represented by a minor fold near Carrington (Figure 18).

D'Arcy–Cousland Anticline

The D'Arcy–Cousland Anticline flanks the Main Syncline to the east; it extends from Prestonpans to the Vogrie Fault near Gorebridge (Figure 4) and (Figure 18) and almost separates the Midlothian and East Lothian coalfields. The general form is an elongate dome with moderate dips to east and west. At the northern end it pitches north-north-eastwards in a similar way to the Main Syncline, but at the southern end near Gorebridge an abrupt southerly pitch is seen. This important anticline has been drilled for oil and gas (p. 134).

Herbershaw Anticline

The Herbershaw Anticline is a faulted fold bounding the east side of the Penicuik Syncline from the Vogrie Fault at Newbigging to near Spurlens Rig. To the south of Herbershaw is the ridge of Ordovician rocks of the Kingside and Spurlens Rig area, against which the Carboniferous is faulted.

Halkerston Syncline

The Halkerston Syncline is a sharp, faulted fold running south from the Vogrie Fault near Fushiebridge to Halkerston; dips of up to 30 degrees have been recorded. The centre of the syncline is occupied by an outlier of the Upper Limestone Group (p. 62). The eastern limb of this fold may structurally be the continuation of the eastern limb of the Main Syncline north of the Vogrie Fault.

Other minor folds

Other minor folds occur on the west limb of the Main Syncline bordering the Pentland Fault. The most striking of these is the Moredun Basin, a syncline involving Lower Limestone Group and Upper Oil-Shale Group strata at outcrop. The principal synclinal axis runs north-north-east. At Broomhills, north-west of Straiton, a synclinal structure is indicated by records of old oil-shale workings and the disposition of oil-shales and associated strata which were seen to dip steeply in the adjacent Burdiehouse Burn. West of Straiton, bores, including the Pentland Diamond Bore (p. 11), have proved an anticline lying between this syncline and the Main Syncline to the east. South-west of Straiton a series of sharp synclines and anticlines with axes directed north-south were encountered in workings in the Pentland Shale.

Faulting

As already mentioned the north-western boundary of the Midlothian Coalfield is formed by the powerful south-westerly trending Pentland Fault (Figure 17) and (Figure 18).

The equally important Lammermuir Fault, with a somewhat similar trend, lies at the south-eastern extremity of the coalfield. This fault and the Leadburn Fault, which is parallel to the Pentland Fault, form part of the great fault-system that extends. from Loch Ryan to Dunbar and is often referred to as the Southern Upland Fault (Anderson 1951, pp. 93, 98; Macgregor and MacGregor 1948, p. 1). A number of lesser faults also run in a general south-westerly direction, among them being the Dunbar–Gifford Fault.

Faults running approximately east-west are numerous, the most important being the Carrington Fault. Faults with a north-westerly trend include the Carberry Fault and are particularly abundant on the north-western margin of the field.

The faults already mentioned follow directions which are commonly found in the Midland Valley of Scotland (Macgregor and MacGregor 1948, p. 5) but in addition the Midlothian Coalfield has fractures with other trends. Thus some follow a north-south direction, an obvious example being the Halkerston Fault.

The most conspicuous faults within the coalfield are the Vogrie, Crossgatehall and Sheriffhall faults. These fractures start on the eastern side of the coalfield with a south-westerly trend and swing across the field in arcuate courses concave to the north and take on a north-westerly trend on the western side of the basin.

Pentland Fault

The Pentland Fault runs from Portobello to Carlops and beyond in a southwesterly direction. For the greater part of its course the fault separates the Midlothian Carboniferous from Old Red Sandstone rocks of the Pentland Hills and Braid Hills. Between Craigmillar and Portobello, however, the base and progressively higher beds of the Carboniferous of the Edinburgh district abut on the west side of the fault. At Portobello, where it disappears under the Firth of Forth, the Upper Oil-Shale Group on the east is thrown against the Lower Oil-Shale to the west.

At Liberton the highest beds of the Upper Oil-Shale Group are brought against Upper Old Red Sandstone strata which, if the displacement is entirely in the vertical sense, implies a throw of thousands of feet. The Pentland Fault was considered to be a reverse fault by Peach and others (1910, p. 8) on account of the steep, and in parts inverted, belt of strata bordering the east side. A gravitational survey was carried out across the line of the fault near Portobello (McLintock and Phemister 1929, pp. 10–28) and the conclusions drawn confirmed the original view of a reverse fault inclined steeply to the west. Shortly afterwards a magnetic survey was carried out in the same area (Hallimond 1931, pp. 30–38) which gave results less conclusive in regard to the nature of the fault. More recently bores put down in connexion with oil prospecting were reported to have proved a reverse hade of 22 degrees near Mortonhall (Lees and Taitt 1946, p. 275).

In 1949 a sewer-tunnel was driven through rock across the line of the fault farther north. The tunnel ran eastwards along Milton Road West to the crossroads just over a mile east of Duddingston where it turned south along Niddrie Road. Although no main plane of movement could be distinguished, a zone of steeply inclined Oil-Shale Group strata with frequent thin crush-belts was encountered about 800 ft in width with no specifically identifiable horizons. The line of outcrop of the fault calculated from the gravitational survey of 1929 lies within this crush-zone, 200–300 ft from the west side and close to the present line of outcrop of the fault shown on the six-inch geological map (Edinburgh 4 S.W.), 100 yd south-south-east of the crossroads. The Pentland Fault may have acted at another period in post-Carboniferous times as a sinistral wrench-fault (Anderson 1951, p. 99).

Lammermuir Fault

The Lammermuir Fault is the limiting fault of the south-eastern part of the Carboniferous of Midlothian and East Lothian (Bailey in Clough and others 1910, p. 165). It is the most easterly of the fractures in the Southern Upland Fault-system. The plotted course of the Lammermuir Fault has been altered in the recent mapping from that shown on the 1955 reprint of the one-inch geological Sheet 24 (p. 8) and now follows the Moorfoot Hills scarp feature more closely between Broad Law Quarry and Hoghill. This scarp feature is in line with a fault with well developed fault-breccia seen cutting the Ordovician strata of Hoghill; the latter fault is therefore considered to be the south-western extension of the Lammermuir Fault.

Dunbar–Gifford Fault

The Dunbar–Gifford Fault of East Lothian (Bailey in Clough and others 1910, p. 166) extends into the area and is mapped about a mile to the north-west of and roughly parallel to the Lammermuir Fault. In the area dealt with in this memoir the evidence upon which the fault is drawn is slight, namely faulting of the Currie Glen lava and the steep dip of the Calciferous Sandstone of the upper part of the South Middleton Burn. The mapped fault limits the crop of the Lower Limestone Group for some distance south-west of Middleton, but the identity of the strata in this district on the south side of the fault has not been proved (p. 8).

Leadburn Fault

The Leadburn Fault is the direct north-easterly continuation of the principal member of the Southern Upland Fault-system in the Biggar–Symington country. It forms the eastern boundary of the Carboniferous of the Penicuik Syncline south of Leadburn, where it brings the Lower Limestone Group against Ordovician. North of Leadburn the fault runs through Carboniferous strata just west of the axis of the Herbershaw Anticline. Moderately steep westerly dips occur along the western or downthrow side. The amount of throw where the fault is in Carboniferous strata is only from 120 to 300 ft. It is of interest to note that the Southern Upland Fault near New Cumnock in Ayrshire shows evidence of having originated in pre-Carboniferous times and of having been affected by comparatively little later movement (Anderson 1951, p. 97). The Leadburn Fault may in pre-Coal Measure times have been continued by the Crossgatehall Fault (p. 124).

Vogrie, Crossgatehall and Sheriffhall faults

The Vogrie, Crossgatehall and Sheriffhall faults are the three main faults within the coalfield. These faults are remarkable in that each of them has a curved course running south-westwards on the east of the basin, swinging westwards across it and then turning or branching in a north-westward direction. Their downthrows are on the whole to the north and their hades where known are in this direction; they therefore appear at first sight to be normal faults. The greatest downthrow of the Sheriffhall and Vogrie faults occurs in their middle, roughly east-west, portions. This fact was originally explained by Clough (in Peach and others 1910, p. 161) on the supposition that they originated during the folding of the basin. It seems possible, however, that they were initiated earlier than the folding, along lines oblique to the strike of the fold-axes, and were themselves folded. It is noteworthy that, as shown in (Figure 18), the fold-axes are shifted laterally along the lines of these three faults.

The Vogrie Fault

The Vogrie Fault runs in a curved course from Southside by Vogrie to Roslin. The fault is well exposed in the Gore Water, where the adjacent strata on the north-western side, including the Index Limestone, are crumpled. At Arniston Mains the throw is about 1000 ft. At this point the Vogrie Fault turns to the west and is joined by a splay from the east, the throw of both main and branch faults being about 500 ft. In the middle part the Roslin Sandstone Group is thrown down to the north against the Limestone Coal Group, giving an apparent vertical displacement of about 1200 ft. The north-westerly continuation of this fault on the west side of the coalfield near Rosslynlee appears to give a dextral displacement of the main synclinal axis of the basin (Figure 18).

In general, different structures are seen on either side of the fault, which, with the other facts known, suggests that wrench movement has occurred during its history.

Crossgatehall Fault

The Crossgatehall Fault extends from Port Seton in a south-south-westerly direction to Crossgatehall. From here it passes through Newtongrange, turns westwards, and splays out to the north-west towards Polton in the Coal Measures.

The throw is to the north or west in most of its course; a little west of Newtongrange, for instance, a northerly downthrow of 420 ft is recorded. Between Queen Mary's Mount and Prestonpans, however, the throw is to the east and in places of greater amount.

Near Queen Mary's Mount there is a possible sinistral displacement of the Cousland anticlinal axis, whilst at Port Seton and Prestonpans there are apparent sinistral displacements of quartz-dolerite dykes. In both instances, however, the evidence is inconclusive. Where this fault or splays from it are running east-west or north-west there is a possible dextral displacement of the axis of the Main Syncline.

The Coal Measures between Upper Dalhousie Farm and Whitehill House have proved to be unfaulted. Workings in the Arniston Parrot Coal of the Limestone Coal Group below, however, extending westwards just past Whitehill House, ended at a series of small faults. This fact, taken with the striking alignment of the Crossgatehall Fault with the Leadburn Fault, has suggested the possibility that the two may have been continuous as a pre-Coal Measure fault which did not operate again in this area in Coal Measure or later times.

Sheriffhall Fault

The Sheriffhall Fault has a sinuous course: from Smeaton it crosses the Main Syncline by Sheriffhall to near Burdiehouse. The maximum apparent throw is about 600 ft to the north. The fault-plane was reported to have ruts and scratches inclined at 20 to 30 degrees to the horizontal in one instance and in another scratches inclined at 30 or 50 degrees to the horizontal dipping towards the south-east (Milne 1839, pp. 304 and 273). The strata were observed to be shattered on the northern or downthrown side.

Carrington Fault

The Carrington Fault commences about half a mile north-north-east of the village of that name and runs in a westerly direction for about one mile before turning to the south-west. A good exposure of the fault-plane in the southwesterly part of its course was seen in a mine in the Whitehill Colliery workings in Coal Measures. The fracture was nearly vertical and showed large-scale horizontal fluting. The throw is less than 200 ft here. In the Lady Victoria Pit workings (Figure 17) in the Limestone Coal Group, where the Carrington Dook cuts the east-west part of the fault, there is a drag-down of strata on the northern side and crushed and contorted strata on the southern (downthrown) side of the main dislocation. The apparent vertical displacement is here 510 ft. The throw decreases rapidly to the east from this point and the fault has been mapped as dying out. It may, however, be continuous in this direction with another fault of opposite throw, but on a similar line, encountered in the Emily Pit workings.

Carberry Fault

The Carberry Fault, which runs from Crossgatehall to Monktonhall, perhaps has the greatest throw of any north-west fault in the coalfield. At the former place it terminates against the Crossgatehall Fault. The downthrow was proved to be 780 ft to the north in Dalkeith Colliery, where a mine was driven from the Peacock (Coronation) Coal through the fault to the North Greens Coal.

Halkerston Fault

The Halkerston Fault is the best known of a number of north-south faults which occur in the southern part of the coalfield. A belt of folded and faulted strata which includes the Halkerston Syncline (p. 120) and is up to a quarter of a mile wide, extends from the Vogrie Fault to the Dunbar–Gifford Fault (Figure 18). It separates very gently northerly or north-easterly dipping beds to the west in the Arniston House and Esperston district from the moderately steep westward dipping strata of Middleton and Catcune. The Halkerston Fault runs mainly down the east side of this belt and has a westerly downthrow. Despite numerous shallow borings the structure of the area is still imperfectly understood and it is possible to interpret the facts by postulating wrench faulting. The relationship to the Halkerston Fault of the east-west fault which runs by Temple has not been proved. Another marked north-south fault outside the coalfield area runs south from the Lammermuir Fault a little to the east of the line of the Halkerston Fault and is shown on the 1955 reprint of one-inch geological Map Sheet 24 as a wrench fault. If these two north-south faults are part of the same fracture line then there has been a sinistral displacement along the line of the Lammermuir or the Dunbar–Gifford Fault or both.

Remaining faults mapped in the coalfield

The remaining faults mapped in the coalfield are shown, with those described above, in (Figure 18). Some minor faults too small to record on the maps are, however, worthy of notice. For instance small reversed faults or thrusts with high hade have been observed cutting steeply inclined Limestone Coal Group strata in crosscut mines in the Ramsay Pit at Loanhead. The displacement along the fault-planes is about 2 to 3 ft.

Such faults may be the cause of the narrow 'wants' noted by Mr. G. K. Sibbald of the National Coal Board as occurring in the South Parrot Splint Coal of Burghlee Pit, where they reach a length of 1000 yd and trend north-north-east.

Age and relationships of folding and faulting

Apart from some possibly pre-Coal Measure faulting (p. 123) the folding and faulting in the coalfield are clearly post-Coal Measures in age, since all beds, including the Barren Red Measures, are involved. The exact age is, however, a matter for speculation. As already noted there is some support for the view that certain faults were active shortly before the main folding of the Coal Measures (p. 124). The major folds are considered to be the result of pressures which also gave rise to local minor crumpling and produced the reverse movement of the Pentland Fault and of certain minor thrusts.

In the Midland Valley the major east-west faulting is generally considered to be of Permo-Carboniferous age and to have begun before the intrusion of the east-west quartz-dolerite dykes; the north-west trending faults are regarded as later than the east-west faults and possibly of Tertiary age (Anderson 1951, p. 37). In accordance with this view a number of north-west faults are seen in Midlothian to terminate at, or branch from faults trending in other directions, including east-west.

If the dykes at the north end of the coalfield have in fact been disrupted by north-easterly tear-faults (p. 124), it follows that the faulting along these lines is at least in part later than the intrusions.

References

ANDERSON, E. M. 1951. The Dynamics of Faulting and Dyke Formation with Applications to Britain. 2nd edit. Edinburgh.

CLOUGH, C. T., BARROW, G., CRAMPTON, C. B., MAUFE, H. B., BAILEY, E. B., and ANDERSON, E. M. 1910. The Geology of East Lothian. Mem. Geol. Surv.

HALLIMOND, A. F. 1931. On a Preliminary Magnetic Survey over the Pentland Fault, near Portobello, Midlothian, Scotland. Sum. Prog. Geol. Surv. for 1930, pt. 3, 30–38.

LEES, G. M., and TAITT, A. H. 1946. The Geological Results of the Search for Oilfields in Great Britain. Quart. J. Geol. Soc., 101, 255–317.

MACGREGOR, M., and MACGREGOR, A. G. 1948. The Midland Valley of Scotland. 2nd edit. British Regional Geology, Geol. Surv.

MCLINTOCK, W. F. P., and PHEMISTER, J. 1929. A Gravitational Survey over the Pentland Fault, near Portobello, Midlothian, Scotland. Sum. Prog. Geol. Surv. for 1928 pt. 2, 10–28.

MILNE, D. 1839. Memoir on the Mid-Lothian and East-Lothian Coal-Fields. Trans. Roy. Soc. Edin, 14, 253–358.

Chapter 10 Drift deposits

During the Pleistocene Ice Age the Midlothian Coalfield was completely submerged by ice at the time of maximum glaciation. The contents of the lowest boulder clay or ground moraine deposited at this time show that the ice originated in the Highlands (Peach and Home in Peach and others 1910, pp. 32930). The boulder clay was widely spread, filling in hollows and valleys and thus gives rise to buried channels which are a considerable mining hazard. Although glacial striations have not been observed on the rocks of the coalfield, streaking out or disturbance of the softer rocks is often seen at the surface. During the retreat of the ice large quantities of sand and gravel and clay were laid down partly as morainic but mainly as fiuvioglacial and lacustrine deposits. Diversion of drainage by the ice resulted in the formation of glacial drainage channels, often deeply cut and mostly directed to the east. After the disappearance of the ice-sheets falls of sea-level left a succession of raised beaches and deposits of marine clays. Progressive rejuvenation of the re-established rivers resulted in a succession of river terrace deposits. Peat was formed in places. Blown sand has accumulated to a small extent behind the present sea-beach.

Buried channels

A number of pre-Glacial buried channels, filled by glacial drift, often unusually thick, have been recognized. Where sufficiently proved they are shown on the six-inch geological maps. Evidence of the existence of these channels is derived mainly from boreholes, but their margins are sometimes revealed by denudation along modern river courses. The direction of some of the buried channels suggests that that they may have been glacial drainage channels, formed at some early stage in the glacial history of the area. In many parts of the coalfield little is known about the details of rockhead topography. The following account brings together most of the available evidence regarding buried channels.

Temple Channel

(Six-inch Midlothian 14 S.W.).—The Temple Channel runs roughly northwards from Broadhead Wood by the east side of Temple Farm to Arniston House; from here it probably crosses obliquely to the west side of the River South Esk. This river runs in a nearly parallel course about half a mile to the west in a rock-cut gorge extending from Rosebery Reservoir by Temple to a point a quarter of a mile west of Arniston House. The thickness of drift filling the channel is more than 131 ft 6 in., at which depth the Arniston Mains No. 23 Bore, 550 yd N.E. of Temple Farm, failed to reach rockhead.

Redside Channel

(Six-inch Midlothian 14 S.W.).—The Redside Channel runs eastwards from a point 500 yd S. of Redside, crosses the Redside Bum obliquely and appears to cross the River South Esk 600 yd W.S.W. of Amiston House, where it may join with the Temple Channel. At the point where it crosses the Redside Burn laminated clays, and silts as well as boulder clay are exposed at water-level. The greatest thickness of drift so far proved in the Redside channel was 171 ft in Rosebery No. 4a Bore, 400 yd S.E. of Redside.

Gore Channel

(Six-inch Midlothian 8 S.E., 14 N.E.).—Deep drift found in bores in the grounds of Harvieston House near Gorebridge, along with other evidence, suggests a possible buried course of the Gore Water. Although there is not enough evidence to mark the conjectural course on the map, the channel may run a little to the west of the present river from Harvieston House to the Shank Bridge, where boulder clay is exposed in the river. It probably extends northwards from here to Emily Pit, which was sunk through 112 ft of drift.

Edgelaw Channels

(Six-inch Midlothian 14 S.W.).—The thickest drift recorded in Midlothian is in the Cauldhall and Edgelaw district, south of Carrington. In Rosebery No. 10 Bore (1951), 450 yd E.N.E. of Edgelaw, 204 ft of drift was drilled before rockhead was reached. This is probably not a maximum thickness as the bore was sited near the bottom of a late-glacial drainage channel. Here again the evidence is not sufficient to plot a buried channel course on the map. The main hollow probably runs north-eastwards under or just west of Cauldhall Farm and under Edgelaw Farm. Nearby a separate or tributary buried channel has been mapped on the east side of the Fullarton Water on the evidence of Fullarton No. 20 Bore (1951), 650 yd S.E. of Cauldhall Farm, which was stopped at a depth of 100 ft without reaching rock-head. The channel is shown as crossing the Fullarton Water 300 yd north-east of the bore, where boulder clay is seen at stream level.

Roslin Channel

(Six-inch Midlothian 7 S.E., 8 S.W., 13 N.E.).—The River North Esk occupies a rock-cut gorge between Roslin and Polton. From Polton to Lasswade the present river flows in a broad valley mainly cut in drift. The old valley between Roslin and Polton probably lies to the west of the present course under the Hewan Bog and Bank near Polton and possibly extends upstream under Roslin itself. Deep drift was found in a number of bores in the vicinity.

Loanhead No. 2 Bore (1867), situated 150 yd N.W. of the bridge where the Roslin to Bilston road crosses the Kill Burn, failed to bottom the drift at 180 ft; Loanhead No. 11 Bore, one mile west of Roslin Chapel, encountered 164 ft. It is uncertain whether these bores are situated on the main buried channel of the River North Esk or on one of its tributaries from the Pentland Hills.

Whitehill Channel

(Six-inch Midlothian 14 N.W.).—A drift-filled hollow was revealed by borings in the ground north-east of Whitehill House. It extends north-north-east for over half a mile from a point 550 yd east-north-east of the house. Here 110 ft of boulder clay was recorded in Whitehill No. 8 Bore (1952). Smeaton Channel (Six-inch Midlothian 8 N.E.).—A buried channel runs south-south-east from Smeaton House towards Langside House. The maximum drift thickness recorded was 112 ft 7 in. in Smeaton No. 3 Bore, 600 yd S.S.E. of Smeaton House.

Niddrie Channel

(Six-inch Midlothian 4 S.W.).—The presence of a buried channel near the Wisp Pit of Niddrie Collieries has been known since the last century (Milne 1839, p. 313). It extends to Redcroft, near which place it was recently cut through in a surface mine driven to reach fireclay.

Forth Channel

Thepossibility of undersea coal workings between Midlothian and Fife is discussed on p. 133. In this connexion rockhead topography and the nature of the overlying drift deposits are important factors affecting undersea development but concerning which there is as yet little concrete evidence. The presence of a buried channel in the River Forth at Bo'ness and Bridgeness has been known for some time (Cadell 1913, p. 97). The greatest depth was recorded in 1936 when a mine driven from the Carron Company's Bridgeness Colliery encountered sand and gravel 675 ft below Mean Sea Level (Macgregor 1940, p. 253). The sea-bed is here 20 ft below Mean Sea Level. A seismic refraction survey across the Firth of Forth between Fife and Midlothian has recently been carried out (Drysdale 1956) but gave no indication of any continuous deep buried channel. A buried channel roughly 400 ft below Ordnance Datum was inferred running east-north-east at a position about 7.5 miles N. of Prestonpans. One of two traverses nearby did not record it. This information can still be reconciled with the Bridgeness evidence if, as suggested by Cadell (1913, p. 98), the depth of the channel at the latter place is due to glacial scouring rather than normal river valley formation.

Boulder Clay

The composition of the boulder clay varies considerably and depends to a large extent on the character of the rocks over which the ice moved. In the main coalfield the basal boulder clay is usually a stiff grey clay with stones, often striated, ranging from the smallest pebbles or fragments up to large boulders about 6 ft across. In other districts, as for example on the flanks of the Currie and Maggie Bowie glens near Borthwick, the boulder clay is extremely sandy in places and is reddish in colour. It commonly has intercalations of gravel, such as those seen along the west bank of the River South Esk near Aikendean. As might be expected, boulder clay is usually thickest in hollows and thinnest on the ridges of the solid rock topography. Thus on the D'Arcy–Cousland ridge it is absent or thin and patchy whilst in many places in the lower lying parts of the coalfield it is commonly over 60 ft thick. Positive boulder clay forms, such as drumlins, are not known in Midlothian.

Because of their strength, the tougher, clayey varieties of boulder clay are more resistant to erosion than some of the solid rocks, such as soft shales and seatclays and they form a satisfactory foundation for buildings.

Two boulder clays, separated by a considerable thickness of sand, have been found in the Loanhead–Roslin district (Anderson 1940). They contain different suites of erratics (McCall and Goodlet 1952, p. 407) but, except where they were seen to be separated by the sand, it was not found practicable to distinguish them in the field. The lower clay is typically grey when fresh, but weathers brown, whereas the upper is almost invariably brown in observed sections.

Glacial sands and gravels

(Figure 20) shows the distribution of sand and gravel. On the revised six-inch geological maps these deposits, many of fluvioglacial origin, have been divided into Moundy Sand and Gravel, and Terraces or Spreads of Sand and Gravel.

Moundy sand and gravel

Deposits of moundy sand and gravel, evidently derived locally, consist partly of well-washed material in which coal fragments, sometimes arranged in definite layers, are conspicuous. They occur most abundantly in the area south of Penicuik and Fullarton. Many of these deposits are disposed in rounded or elongated kame-forms that occur as isolated small hills, such as the one at the south end of Lasswade, or form groups of mounds with hollows between (kettle-hole topography), as in the district between Mount Lothian and Toxside south of Fullarton. The remainder form sinuous ridges and may be eskers; a striking example is the prominent ridge about a mile long extending in a northerly direction from Sheriffhall north-west of Dalkeith. Some of these ridges, such as that running in a north-south direction, 300 yd W. of Pentland village, consist of poorly sorted gravel and boulders with some clay in the matrix.

Terraces or spreads of sand and gravel

The deposits mapped as spreads of sand and gravel are mainly composed of well washed, often current-bedded, material, the sand sometimes containing coal fragments and occasional layers of silt or clay. They occur in great spreads whose upper surfaces are often terrace-like and conform to a general level, as for example near Borthwick.

Between Dalkeith and Penicuik these deposits cover large areas bordering the River North Esk. From Loanhead to Penicuik, however, they are overlain by a covering of boulder clay up to 10 ft thick which forms the overburden in the working sand-pits.

Glacial clays

Deposits of clay, broadly speaking fluvioglacial, though more strictly speaking of glacial-lacustrine origin, are not common in Midlothian. In the southern part of the coalfield, small thicknesses occur, usually inter-laminated with silt.

Such are the deposits on the right bank of the South Middleton Burn 400 yd S. of Middleton House, 1 mile S. of Borthwick, where at least 4 ft of laminated clay and silt are seen under 10 ft of sand and gravel. At Borthwick Hill Sandpit, half a mile north-north-west of Borthwick, up to 12 ft of laminated clay and silt, much sheared and crumpled, is seen to overlie at least 40 ft of sand.

In the main part of the coalfield more extensive deposits of clay are found round Newtongrange. At the disused clay pit 500 yd north-west of this town, laminated stoneless clay was seen to underlie boulder clay while 250 yd west-north-west of this pit the lower part of the clay is exposed at the top of the right bank of the River South Esk, with the following section: clay, brown, stoneless 3 ft; clay, brown, sandy with stones 1 ft; silt, laminated 1 ft; on boulder clay 10 ft.

Farther north fluvioglacial clays are known near Smeaton and Cowdenfoot (p. 136) where they partly fill a buried channel.

Raised beach deposits

Sand and gravel deposits belonging to the 100-ft, intermediate and 25-ft raised beaches occur along the coast from Edinburgh to Prestonpans and extend up to two miles inland towards Dalkeith (Figure 20).

The 100-ft Raised Beach

Sand and gravel attributed to a raised beach have been mapped up to the 100-ft contour line. There is in places an indefinite feature at this height but on the whole the deposits are not readily distinguishable from the fluvioglacial sands and gravels which adjoin them to the south. No marine fossils have been found in them. On the drift edition of the one-inch geological map Sheet 32 (1928) sands and gravels rising to over 150 ft above sea-level near Dalkeith are included as 100-ft Raised Beach deposits. On the recently published revised six-inch geological maps, however, these are now mapped as glacial deposits.

The greater part of the laminated clay deposits formerly worked at Portobello (p. 136) is believed to belong to the period of the 100-ft Raised Beach (Peach and others 1910, pp. 335, 349; Tait 1934, pp. 61–5).

Intermediate raised beaches

Impersistentfeatures close to the 75-ft and 50-ft contours, marking the margins of intermediate beaches, have been recorded at Monktonhall just south of Musselburgh. Again no fossils have been found here in the associated sand and gravel.

The 25-ft Raised Beach

Sandsand gravels, sometimes loosely bound with a ferruginous cement and containing an assemblage of shells comparable with those of the present shore, are associated with this beach (Lee in Peach and others 1910, pp. 410–11). The beach itself, partly rock-cut, forms a striking feature along the coast of Midlothian. The topmost beds of clay at Portobello are believed to belong to the time of this beach (Clough in Peach and others 1910, p. 336).

River terraces

A number of river terraces are found along the courses of the rivers North and South Esk and their tributaries. Where these two rivers unite to form the River Esk below Dalkeith there are as many as five consecutive terraces. Between the confluence and Musselburgh the lower terraces are cut in raised beach deposits and the river has eroded down to boulder clay. Some of the higher terraces may, therefore, be equivalent in age to the raised beaches.

Farther inland, as for example near Dalkeith and Loanhead, it is difficult to know whether to assign some deposits to the lowest glacial gravel spreads or to the highest of the river terraces.

In general the river terrace deposits and present river alluvium vary greatly in texture from silt to gravel and boulders.

Alluvium and lake deposits

Lake deposits are relatively small in extent; they consist of silt and clay. Some of them, such as the clay deposits at the disused Newlandrigg tileworks, about two miles north-east of Gorebridge, are probably immediately post-glacial in age. Many of the glacial drainage channels contain alluvial deposits. The alluvium which forms the present usually flat bottoms, consists of clay, silt or sand and often overlies sand and gravel thought to be of glacial origin.

Peat

Where 2 ft or more in thickness peat has been mapped. Areas of peat are most common in the higher moorland tracts of the southern parts of the coalfield, where some are of economic importance (p. 140). Peat also forms the top deposit in some glacial drainage channels, such as the one which runs just west of Edgelaw Farm and the channel which skirts the south margin of the Arniston House policies.

Blown sand

A small area of blown sand, associated with the present beach in the form of small dunes, has been mapped near Musselburgh.

Landslips

Slips of solid rocks have not been mapped in the coalfield area. Small slips of this nature are nevertheless known to have occurred in parts of the river gorges such as the Roslin, Arniston and Currie glens.

Large-scale slipping of thick glacial deposits has also occurred along some valley sides. A good example is seen on the east bank of the River South Esk between Rosebery Reservoir and Howburn. Here a slip of gravel and boulder clay nearly half a mile long has taken place. Where river valleys are wide and cut in drift, like the North Esk between Polton and Lasswade, their sides now appear to be stable, but the irregular character of the slopes frequently suggests that slipping took place at an earlier date.

References

ANDERSON, J. G. C. 1940. Glacial Drifts near Roslin, Midlothian. Geol. Mag., 77, 470–73.

CADELL, H. M. 1913. The Story of the Forth. Glasgow.

DRYSDALE, W. S. 1956. Firth of Forth Seismic Refraction Survey. Trans. Inst. Mining Eng., 115, 435–54.

MCCALL, J., and GOODLET, G. A. 1952. Indicator Stones from the Drift of South Midlothian and Peebles. Trans. Edin. Geol. Soc., 14, 401–9.

MACGREGOR, M. 1940. The buried Channel of the Forth. Advancement of Science, 1, No. 2, 253–4.

MILNE, D. 1839. Memoir on the Mid-Lothian and East-Lothian Coal-Fields. Trans. Roy. Soc. Edin., 14, 253–358.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

TAIT, D. 1934. Braid Burn, Duddingston, and Portobello Excavations, 1929–31. Trans. Edin. Geol. Soc., 13, 61–71.

Chapter 11 Mineral resources and water supply

A comprehensive general account of the mineral resources of the Lothians, with references to more detailed information, was given by MacGregor (1945) but is now out of print. A summary of the available information is given below.

Coal

The positions of the collieries at present working are indicated on (Figure 4); Polton and Wallyford are now only used for pumping. The coals produced are of a variety of types and include those suitable for gas-producing, household, manufacturing and steam-raising purposes. Analyses of many of the coal seams in the Midlothian Coalfield have been published (Peach and others 1910, pp. 342–3; Gray 1930, pp. 26, 27, 38). Among the seams which have been most extensively worked in the Limestone Coal Group are the North, South (Carleton), Bryans, Peacock, Blackchapel, Stairhead and Great seams, and, in the Productive Coal Measures, the Fifteen Foot, Nine Foot, Salters, Cowpits Five Foot, Musselburgh Jewel, Rough and Splint coals.

Reserves of coal are present both in the Limestone Coal Group and in the Productive Coal Measures, those in the former group being considerably the greater. Information regarding 'the present position and the future prospects' of the Midlothian Coalfield is included in a Report on the Scottish Coalfields (Scottish Coalfields Committee 1944), in which it was estimated that reserves in the Limestone Coal Group then amounted to 712 million tons with a possible additional 85 million tons, not including the vast reserves which may exist in undersea areas outwith the 1944 leaseholds. In addition, a further 184 million tons were believed to remain in the Productive Coal Measures.

Since the above report was completed the sinking of two large new collieries has been commenced at Bilston Glen, south-west of Loanhead (Plate I), and at Monktonhall, about two miles north of Dalkeith, with the object of working seams in the Limestone Coal Group in the deeper parts of the Main Syncline. Monktonhall Colliery will also extract coal from seams in the Productive Coal Measures.

A large extension of the Midlothian Coalfield may be expected to the north of the present undersea workings off Musselburgh and Prestonpans in the direction of the Fife Coalfield. As yet little is known of the potentialities of the undersea field as the formations present and the structure can only be surmised. An assessment of these possibilities was made in the middle of the last century (Landale 1864) but the correlation of the Midlothian and Fife seams was then very inaccurate. The seams of the Limestone Coal Group can now be correlated in a broad manner (Figure 9).

Exploratory work by the National Coal Board is in progress at the time of writing and bores have recently been sunk from the sea-bottom off the Fife coast (Ewing and Francis. In the press). A study of the isopachytes in the Midlothian area (Figure 10) suggests a thinning of the Limestone Coal Group in the northerly undersea direction.

Oil-shale

In the Straiton district, south of Edinburgh, three seams of oil-shale, the Pentland, Broxburn and Fells, have been proved to be of economic value and were worked up till 1898. Other seams are either thin or impure (p. 15). As mentioned by MacGregor (1945, p. 8), a narrow strip of Oil-Shale Group strata probably crops out on the west side of the coalfield as far south as Carlops, but the high dip of the beds presents mining problems. Borings near Carlops and Macbiehill show at least one workable oil-shale over a considerable area (Gibson 1922, p. 49; Carruthers and others 1927, pp. 7, 104–5).

On the east side of the coalfield two thick seams of oil-shale were pierced at depths of 600 or 700 ft in some of the borings for oil and gas at D'Arcy and Cousland, but their exact thickness and quality have not been conclusively proved (pp. 13–14; Gibson 1922, pp. 49, 61; Giffard 1923, p. 242; Carruthers and others 1927, p. 112; Anderson and Simpson 1938, p. 29).

Mineral oil and gas

A number of borings for oil and gas have been made along the crest and on the flanks of the D'Arcy–Cousland Anticline.

In December 1919 boring operations were commenced at a site near D'Arcy Farm, about two and a half miles south-east of Dalkeith; natural gas was found in a fine-grained sandstone at 724 ft, the flow being estimated at 300 000 cu. ft per day, and at 1810 ft oil of very good quality was struck in a soft sandstone. The bore was continued for a further 10 ft, but this apparently did not increase the flow of oil. In the course of two months' trial the well yielded only 7 tons of oil, and in September 1922 operations were suspended (Gibson 1922, pp. 60–63; Giffard 1923, p. 242).

During the period 1937–40 nine oil-wells were drilled in the D'Arcy–Cousland–Falside area. Cousland No. 1, sited just over a quarter of a mile south of Cousland village, reached a depth of 2917 ft; all the sandstones below a depth of 214 ft were found to be oil-impregated; on test much gas but only a little oil was obtained. During a test of short duration a gas-yield of 5 900 000 cu. ft per day was obtained at depths of between 1724 and 1806 ft (Lees and Taitt 1946, p. 271). Six wells were drilled near D'Arcy Farm: Midlothian No. 3, 500 yd E.N.E. of the farm, reached a depth of 1760 ft and produced 31 barrels of oil per day, while Midlothian No. 6 was sunk to nearly 2300 ft, the final production being approximately 35 000 cu. ft of gas per day. Both Midlothian No. 3 and No. 6 are still in production. In 1947 another well, Cousland No. 4, was sunk 350 yd S.W. of Fordel Mains Farm; many of the sandstones through which the bore passed were oily and, during a 3-hour test at a depth of about 1500 ft, gas was produced at a rate ranging from 50 000 to 101 000 cu. ft per day. The bore was finally abandoned at a depth of 1995 ft. A bore for gas (Cousland No. 5) was put down in 1954, about 300 yd S.S.W. of Cousland No. 1 Bore, in the hope of tapping the supply of gas found in that boring, but although a depth of 1918 ft was reached, only relatively small quantities of gas were proved.

All these bores began in beds of the Lower Limestone Group and passed into the Calciferous Sandstone, from which the oil and gas were obtained. Midlothian No. 1, the deepest of the bores, struck the junction between the Carboniferous and the Old Red Sandstone at about 3600 ft and reached a total depth of 3857 ft.

Crude petroleum, floating on top of the water, is found in St. Catherine's Balm Well, about three quarters of a mile south of Liberton church; the well is situated close to the Pentland Fault, on its south-east side, and the underlying rocks belong to the Upper Oil-Shale Group. Crude oil is also reported to have been met with during the construction of a deep drain about half a mile southwest of Niddrie House; this site is also near the Pentland Fault and is on the outcrop of the Upper Oil-Shale Group (Clough in Peach and others 1910, p. 365). These oil seepages suggested that the Pentland Fault, generally considered to be a reversed fault, might be acting as an oil-seal, and that a quantity of oil might be present in the strata immediately to the east of the fault. Three shallow bores, however, put down near the line of the Pentland Fault, about 400 yd W. of Kaimes village, S. of Liberton, indicated a reversed fault with a hade of approximately 22 degrees, too steep to act as an effective oil-trap (Lees and Taitt 1946, p. 275).

Bedded ironstone

Ironstone in the form of layers or nodules has been worked both in the Lower Limestone Group and in the Limestone Coal Group in Midlothian (Macgregor and others 1920, pp. 164–95).

A blackband ironstone in the Lower Limestone Group, between the North Greens Coal and the North Greens Limestone, was formerly worked at Gilmerton, where the maximum thickness was about 15 in. The ironstone, which was associated with the Rough Parrot Coal, thins both to the north and to the south of Gilmerton (Plate I and pp. 2; 22). In a tunnel just west of the Moredun Institute, half a mile north-west of Gilmerton, where the lower part of the Lower Limestone Group is present in a small syncline, the following section of the ironstone was seen: shale with Lingula 2 ft 6 in.; shale, parroty 1 ft; coal, cannel 1 ft; ironstone, blackband, impure 6 in.; fireclay, soft, dark, coaly 1.5 in.; ironstone, blackband 1 in.; coal, bright 2 in.; ironstone, blackband, impure 5 in.; coal, cannel, dull 1 ft 5 in.; coal, bright 9.5 in. on seatearth, dark, soft. A group of bores put down about 400 yd N.E. of the Moredun Institute found a coal in two leaves but no ironstone.

In the Limestone Coal Group the Loanhead No. 1 Ironstone, between the Glass Coal and Bryans Coal (Figure 9) was formerly worked at several localities on the west side of the coalfield; the seam deteriorates to the north of Gilmerton and to the south of Loanhead. The Loanhead No. 2 Ironstone, found about 30 to 60 ft below the Stairhead Coal (Figure 9) was at one time the most important ironstone wrought in Midlothian; the maximum development was found in the Loanhead district where the seam was worked in both the Burghlee and Ramsay pits and also at Roslin Colliery. At Mauricewood, to the south, it was extensively mined but was there known as the 'Great Seam' ironstone (p. 50). Thin blackband ironstones associated with the Stairhead Coal and the Great Seam were at one time worked in Niddrie Collieries; the ironstone with the Great Seam was about 8 in. thick, and that with the Stairhead was 10 in., the lower 4 in. being of inferior quality (Peach and others 1910, p. 341). An ironstone band, known as the Rumbles or No. 3 Ironstone, found about 12 ft to 18 ft above the Great Seam in the area south-west of Loanhead, was extensively worked in the vicinity of Dryden, between Burghlee and Roslin.

Fireclay, shale (blaes) and clay

The seatclay under the Clay Seam at Prestongrange Colliery was formerly worked for brickmaking, and in the latter half of the last century a fireclay a short distance below the Index Limestone was wrought at Joppa for the manufacture of firebricks, pipes and gas retorts (Peach and others 1910, p. 348). Recently, seatearths have been mined for the manufacture of bricks at several collieries in Midlothian, including Ramsay, Roslin and Prestongrange in the Limestone Coal Group and Whitehill in the Productive Coal Measures.

Of late years shale has been worked at several collieries, including Prestongrange, Newbattle and Amiston in the Limestone Coal Group, and Newcraighall and Woolmet in the Productive Coal Measures. Shale for the manufacture of bricks was extracted from an excavation in the upper part of the Upper Oil-Shale Group, about a quarter of a mile north-east of Straiton. The material from colliery bings is also being used for the same purpose.

Mottled red-brown, purple-grey, pale green and yellow marls or mudstones, some of which are probably altered shales or seatearths, are present in the Barren Red Coal Measures in the area immediately north of Dalkeith. In Dalkeith No. 48 Bore one of these beds was over 20 ft thick (p. 114). Samples of these clays have been moulded and burnt into miniature bricks which are reported to have resembled Staffordshire blue bricks, both in appearance and in strength (Peach and others 1910, p. 348).

Laminated clay of the 100-ft Raised Beach deposits was worked extensively at Portobello for many years for the manufacture of bricks, tiles, chimney-pots, flower-pots, etc. (Miller 1870, p. 91; Peach and others 1910, p. 349). The clay, which near the surface is inclined to be sandy, was proved by boring to be at least 100 ft thick. A small area of shelly clay about 10 ft thick belonging to the 25-ft Raised Beach deposits is also present at Portobello (Tait 1934, pp. 61–5).

Clay for the manufacture of bricks and tiles was formerly worked in pits about 550 yd S.W. of Smeaton Farm. A group of bores put down between 1939 and 1942 near No. 9 Mine, about 400 yd E. of the site of these pits, proved the existence of a buried channel, partly filled with dark clay and sandy clay at least 50 ft thick, overlain by boulder clay (p. 128). Clay over 18 ft thick was also met with in a bore near Cowdenfoot, three-quarters of a mile south of the Smeaton Clay-Pits. The clay in the brick-pits and at Cowdenfoot is probably of fluvioglacial origin. Finely laminated clays were at one time dug for brick-making near Eskbank railway station and in old clay-pits north-west of Newton-grange; at both localities the clay is apparently overlain by boulder clay. There are several exposures of stoneless clay in the banks of the Dalhousie Burn southwest from the Newtongrange clay-pits, and clay was formerly dug for the manufacture of tiles in a pit about 300 yd S.W. of Upper Dalhousie Farm. Bricks and tiles were also made from a yellowish sandy clay dug in a pit north of Toxsidehill, at the south end of the coalfield.

Limestone

A description of the character, occurrence, distribution and accessibility of the limestones in the Midlothian Coalfield was given by Haldane and Simpson (1942), and more general information on the same subject is contained in a later publication (Robertson and others 1949, pp. 139–48). Muir and others (1956) have dealt with chemical analyses and petrography. MacGregor (1945, p. 12) noted the limestone output in the Lothians between 1900 and 1937.

The most important limestones from the economic point of view are the Burdiehouse Limestone, at the base of the Upper Oil-Shale Group of the Calciferous Sandstone, and the Gilmerton, North Greens and Bilston Burn limestones in the Lower Limestone Group.

The Burdiehouse Limestone has been worked for many years at Burdiehouse and Straiton. At present the limestone is being worked from a shaft at the Clippens Lime Works, Straiton. The stone is used for iron smelting, cement-making and lime-burning and as ground limestone for agricultural use (Robertson and others 1949, p. 143).

None of the limestones in the Lower Limestone Group is any longer being wrought on the west side of the coalfield. The Gilmerton Limestone was extensively quarried opencast, and mined, north-west and west of Gilmerton, but several of the old quarries have now been filled in. The upper part of the limestone is rather impure, and only the lower bed, consisting of 8 ft of crinoidal limestone, was wrought.

On the south-east side of the coalfield the North Greens Limestone is at present being mined and worked opencast at Middleton Lime Works, about 600 yd S.S.W. of North Middleton cross-roads, and at Esperston Lime Works, in a new opencast (Burn Quarry) 800 yd S.S.E. of Esperston Farm. The Bilston Burn Limestone is being worked at Esperston Lime Works, in a quarry 800 yd N.W. of Esperston Farm.

Of late the basal bed of the North Greens Limestone has been mined at Northfield Quarry, near Cousland; for a time this bed and the overlying calcareous shale were used for the manufacture of cement at a nearby works. The upper part of the limestone, which is much less pure than the lower bed, is being wrought in a quarry 800 yd S.W. of Northfield Farm. The analysis of the beds overlying the calcareous shale suggests that they are suitable for the manufacture of rock wool (Guppy and Phemister 1949, pp. 21–2).

Ochre

Two ochre beds are exposed in the Bilston Burn, three miles south of Gilmerton; the lower, about 21 ft thick, represents the Gilmerton Limestone, and the other, 3 ft thick, occurs at the top of the North Greens Limestone. It is reported (Hinman in Peach and others 1910, p. 180) that these beds were at one time worked for ochre, but there seems to be little conclusive evidence for this. About seven and a half miles to the south-west, in the Nine Mile Burn, the Gilmerton Limestone is represented by a bed of ochre at least 20 ft thick.

Sandstone-building stone

The sandstone output of the Lothians between 1900 and 1937 is given by MacGregor (1945, p. 15).

Calciferous Sandstone

A grey to brown or yellowish sandstone in the Calciferous Sandstone was formerly worked at Currie Glen, Borthwick (Craig 1893, pp. 266, 273; Peach and others 1910, p. 358), and a brown ripple-marked sandstone in the upper part of the Upper Oil-Shale Group was once worked in quarries at Long Loan, about one mile south-south-west of Gilmerton. The Binny Sandstone, grey or white in colour, was at one time worked at Straiton Quarry; the stone was found to contain crude oil which stained the surface of dressed blocks, as a consequence of which the quarry was closed; it is now partly filled in.

Lower Limestone Group

Sandstonesin this division were formerly worked at Edgehead Quarry, immediately south of Gilmerton, and in a quarry near Edgefield, one and a quarter miles south-south-west of Gilmerton. At the former quarry, now filled in, the stone was soft and yellowish or whitish, while at Edgefield the sandstone quarried (the North Greens Sandstone) was soft and pale yellowish, with some pebbly bands.

Limestone Coal Group

Sandstones at various horizons in the Limestone Coal Group have been worked in the past, but all the quarries are now abandoned and many have been, or are being, filled in.

A massive false-bedded sandstone immediately under the Corbie coals was formerly wrought in two quarries in Lawfield Wood, a quarter of a mile north-east of Lawfield Farm, one and three quarter miles south-east of Dalkeith, and a yellow freestone just below the Ball Coal was quarried 300 yd N.E. of Marfield, three and a quarter miles south-west of Penicuik. The rock in the last-mentioned quarry, at one time thought to be in the upper part of the Limestone Coal Group (Peach and others 1910, p. 356), is on the same horizon as the Kittleyknowe Sandstone (p. 39). In Masterton Quarry, one mile south-east of Newtongrange, a massive, coarse, pebbly sandstone, lying between the Corbie coals and Bryans Coal, was formerly worked, but the quarry is now filled in. The Coronation Sandstone, overlying the Peacock Coal, was wrought in several quarries in the area north and east of Gorebridge, for example at Whitehouse Quarry, two-thirds of a mile north by east of Gorebridge, and Millstone Brow Quarry, two-thirds of a mile east of Gorebridge. At Lilyburn Quarry, one mile and three-quarters east-south-east of Penicuik, a sandstone in the upper part of the Limestone Coal Group was at one time worked on a small scale to obtain material for facing artificial stone (Macgregor and others 1940, pp. 29–30). A sandstone in the upper part of the Limestone Coal Group was wrought at Shaw's Quarry, near Easthouses, just over one mile south-east of Dalkeith, and another sandstone, higher up in the succession, between the Great Seam and the Index Limestone, was worked in Melville Quarry, one mile south by west of Gilmerton and in a group of old quarries a quarter of a mile east-south-east of Gilmerton.

Upper Limestone Group

JoppaQuarry, where the Joppa Sandstone, overlying the Index Limestone, was formerly worked, is now filled in; a sandstone on the same horizon was wrought at Cowden Cleuch Quarry, one and a half miles east by north of Dalkeith, and in two neighbouring quarries.

Roslin Sandstone Group

The sandstones of the Roslin Sandstone Group have not been quarried to a great extent, probably because they tend to be rather soft and, in some localities, are gritty and pebbly. About 30 ft of reddish sandstone is exposed in the disused Castle Quarry, about 150 yd S.E. of Dalhousie Castle and a very coarse, pale yellow sandstone is exposed in a disused quarry about half a mile east-south-east of Newbattle Home Farm. A brownish sandstone was wrought in a large quarry 400 yd W. of Smeaton Shaw Farm, and two quarries in a sandstone near the top of the Roslin Sandstone Group were formerly in operation, one on each side of the Haddington Road, east of Leven-hall, to the east of Musselburgh, but both are now filled in and built over.

Coal Measures

Sandstonesin the Productive Coal Measures were formerly worked at two quarries near Bonnyrigg; a massive coarse sandstone, the Broomieknowe Sandstone, just below the seatearth of the Jewel Coal, was wrought in a quarry south-west of Broomieknowe station, and a yellow sandstone at least 60 ft thick, lying some distance above the Whitehill Great Seam, was quarried about 450 yd N.E. of the station. The last-mentioned quarry is now partly filled in and no rock is now exposed. In the vicinity of Barleydean, at the south end of the outcrop of the Productive Coal Measures there is a group of old quarries where medium-grained and coarse-grained reddish sandstones were once worked. A sandstone between the Cowpits Five Foot Coal and the Little Splint Coal was at one time wrought at Cowpits, about one and a quarter miles south of Musselburgh, but the quarry is now completely overgrown.

Siliceous sandstone

Lower Limestone Group

A bed of ganister-like sandstone 3 ft thick, and separated from the base of the North Greens Limestone by 9 in. of shale, crops out in the Cairn Burn 500 yd E. of Upper Whitfield, two miles south-east of Carlops and the same bed was formerly exposed in Deepsykehead Quarry, just under one mile north of Upper Whitehill, where the thickness was variable and averaged 2 ft 6 in. The percentage of SiO₂ in this rock ranges from 95.05 to 99.44 (Thomas and others 1920, pp. 24, 25, 29, 30). A bed of hard white sandstone 2 to 3 ft thick was formerly seen a few feet above the top of the North Greens Limestone in Middleton Quarry, about one mile south-west of Middleton House, and a sandstone on the same stratigraphical horizon crops out in the North Middleton Burn, 550 yd S.S.E. of Esperston Farm, where it is at least 3 ft thick (Anon. 1920, p. 153). A hard brown rooty sandstone is exposed in a small stream 210 yd S.E. of Westhouses, about one and a quarter miles east of Newtongrange. The rock is about 1 ft 6 in. to 3 ft thick and, since the drift cover is very thin, the outcrop can be traced for 400 yd south-east from the exposure in the stream. An analysis showed that the SiO₂ percentage was 95.21, but the rock was not found suitable as a substitute for Belgian sand in glass-making (Anon. 1920, p. 154; Thomas and others 1920, pp. 24, 25). Another ganister-like sandstone, at least 18 in. thick, which crops out on the south bank of the River North Esk at the bend just under one mile east-southeast of Auchendinny, has been analysed and proved to have a SiO₂ percentage of 96.98 (Thomas and others 1920, pp. 24, 25).

Sandstone for moulding, glass-making, etc.

In a quarry two-thirds of a mile north-east of Gilmerton a soft yellow sandstone, between the Great Seam and the Index Limestone, was excavated many years ago and used as a source of sand for stable yards (Gibson and Bailey in Peach and others 1910, p. 199). A current-bedded coarse-grained kaolinitic sandstone in the Limestone Coal Group between the Corbie Craig Coal and the Black Metals Marine Band was worked between the years 1937 and 1943 in Kittleyknowe Quarry, three-quarters of a mile east-north-east of Carlops, as a source of silica sand; the processed sand was used for pig-iron moulding, for steel moulding, for acid open-hearth furnaces and for the manufacture of bottle-glass. Reserves are large (MacGregor 1945, p. 22). The North Greens Sandstone was formerly worked for sharp sand (p. 24).

Sand and gravel

A detailed description of the distribution, extent and nature of the sand and gravel deposits in the Midlothian Coalfield (p. 129) is included in a recent account by Haldane (1948); most of the sand-pits at present in production are sited in a belt of fluvioglacial deposits extending south-west from Dalkeith to beyond Penicuik and one is also in operation in similar deposits near Borthwick (Figure 20). At Newhailes Sand-pit, near Musselburgh, fine, coarse and sharp sands in the 100-ft Raised Beach deposits have been worked of late.

Peat

Extensive areas of peat are present at the south end of the coalfield, between Penicuik, Carlops, Leadburn and Gladhouse, the largest being Auchencorth Moss. A sample of peat from Side Moss three miles south-west of Temple was tested some years ago in connexion with the extraction of ester waxes (Cawley and King 1946, p. 21).

Water supply

Detailed information regarding water supply from underground sources in Midlothian, and a well-catalogue for that area, are given by MacGregor, Allan and Lawrie (1942). MacGregor (1945, p. 36) also gives notes on the hydrogeology of the rocks of the Lothians.

The Cementstone Group in the Edinburgh district includes a considerable thickness of manly beds and yields of water from bores in that formation are not high; the water obtained is hard and is mostly used for brewing. The Oil-Shale Group and the Lower Limestone Group both contain thick sandstones and yield hard water on boring (MacGregor 1945, pp. 37–8). The water found in the Limestone Coal Group is hard and sometimes acidic and highly mineralized (Clough in Peach and others 1910, p. 364), but both the Upper Limestone Group and the Roslin Sandstone Group give good supplies, although that from the former formation is generally rather hard. The highest yield in Scotland was probably given by a bore put down in the upper part of the Productive Coal Measures at Inveresk, near Musselburgh. The bore was sited near the central axis of the syncline and passed through several thick sandstones, the yield on test being 60 000 gallons per hour.

Spring water is obtained from fluvioglacial sands and gravels in some areas, e.g. at Dalkeith, Lasswade and Bonnyrigg.

References

ANDERSON, F. W., and SIMPSON, J. B. 1938. Geological Notes on the Borings for Oil now in Progress at Cousland and D'Arcy, Midlothian. Oil-Shale and Cannel Coal. Inst. Petroleum.

ANON. 1920. Refractory Materials: Ganister and Silica-Rock—Sand for Open-Hearth Steel Furnaces—Dolomite. Resources and Geology. 2nd edit. Mem. Geol. Surv., Min. Resources, 6.

CARRUTHERS, R. G., CALDWELL, W., BAILEY, E. M. and CONACHER, H. R. J. 1927. The Oil-Shales of the Lothians. 3rd edit. M., Geol. Surv.

CAWLEY, C. M., and KING, J. G. 1946. The Extraction of Ester Waxes from British Lignite and Peat. Fuel Research Board, Technical Paper No. 52.

CRAIG, G. 1893. On Building Stones used in Edinburgh: their Geological Sources, Relative Durability, and other Characteristics. Trans. Edin. Geol. Soc., 6, 254–73.

EWING, C. J. C., and FRANCIS, E. H. Nos. 1 and 2 Off-shore Borings in the Firth of Forth (1955–56). Bull. Geol. Surv. Gt. Brit. (in the press).

GIBSON, W. 1922. Cannel Coals, Lignite and Mineral Oil in Scotland. Mem. Geol. Surv., Min. Resources, 24.

GIFFARD, H. P. W. 1923. The Recent Search for Oil in Great Britain. Trans. Inst. Mining Eng., 65, 221–50.

GRAY, T. 1930. A Survey of Scottish Coking and Furnace Coals. Physical and Chemical Survey of the National Coal Resources, No. 15. Fuel Research Board.

GUPPY, E. M., and PHEMISTER, J. 1949. Rock Wool. 2nd edit. Mem. Geol. Surv., Min. Resources, 34.

HALDANE, D. 1948. Sands and Gravels of Scotland. Quarter-Inch Sheet 15: Fife-The Lothians-Berwickshire. Geol. Surv. Wartime Pamphlet, No. 30 pt. 4.

HALDANE, D., and SIMPSON, J. B. 1942. Limestones of Scotland: East-Central Scotland. Geol. Surv. Wartime Pamphlet No. 13, Area III.

LANDALE, D. 1864. Description of the Large Coal-field under the Firth of Forth. Trans. Roy. Scot. Soc. Arts, 6, 341–64.

LEES, G. M., and TArrr, A. H. 1946. The Geological Results of the Search for Oilfields in Great Britain. Quart. J. Geol. Soc., 101, 255–317.

MACGREGOR, A. G. 1945. The Mineral Resources of The Lothians. Geol. Surv. Wartime Pamphlet, No. 45.

MACGREGOR, A. G., ALLAN, J. K., and LAWRIE, T. R. M. 1942. Water Supply from Underground Sources of South-East Scotland (Quarter-Inch Geological Sheet 15): Well-Catalogue for One-Inch Sheet 32 (Lothians Portion). Geol. Surv. Wartime Pamphlet, No. 28, pt. 2.

MACGREGOR, M., LEE, G. W., and WILSON, G. V. 1920. The Iron Ores of Scotland. Mem. Geol. Surv., Min. Resources, 11.

MACGREGOR, M., and others. 1940. Synopsis of the Mineral Resources of Scotland. Mem. Geol. Surv., Min. Resources, 33.

MILLER, H. 1870. Edinburgh and its Neighbourhood, Geological and Historical; with the Geology of the Bass Rock. 4th edit. Edinburgh.

MUIR, A., HARDIE, H. G. M., MITCHELL, R. L., and PHEMISTER, J. 1956. The Limestones of Scotland. Chemical Analyses and Petrography. Mem. Geol. Surv., Min. Resources, 37.

PEACH, B. N., CLOUGH, C. T., HINXMAN, L. W., GRANT WILSON, J. S., CRAMPTON, C. B., MAUFE, H. B., and BAILEY, E. B. 1910. The Geology of the Neighbourhood of Edinburgh. 2nd edit. Mem. Geol. Surv.

ROBERTSON, T., SIMPSON, J. B., and ANDERSON, J. G. C. 1949. The Limestones of Scotland. Mem. Geol. Surv., Min. Resources, 35.

SCOTTISH COALFIELDS COMMITTEE. 1944. Scottish Coalfields, The Report of the Scottish Coalfields Committee. Scottish Home Department.

TAIT, D. 1930. Brick-making with low-grade Oil Shale at Hailes Quarry, Edinburgh. Trans. Edin. Geol. Soc., 12, 195.

TAIT, D. 1934. Braid Burn, Duddingston and Portobello Excavations, 1929–31. Trans. Edin. Geol. Soc., 13, 61–71.

THOMAS, H. H., HALLIMOND, A. F., and RADLEY, E. G. 1920. Refractory Materials: Ganister and Silica-Rock-Sand for Open-hearth Steel Furnaces-Dolomite. Petrography and Chemistry. Mem. Geol. Surv., Min. Resources, 16.

Appendix: Glossary of mining and rock terms used in this memoir

IN the Scottish coalfields, as in others, there are traditional names for rocks and mining terms which have come into use during the long history of mining in the country. Their precise meaning is often a source of difficulty to those unaccustomed to them and coalfield geologists are tending more and more in all fields to adopt common rock terms such as sandstone, siltstone, mudstone, clay and shale with suitable descriptive adjectives in place of the local names like fakes and blaes.

This has been done to a large extent in the present memoir, but it would be manifestly absurd and often misleading to attempt a wholesale conversion of local terms, so that many examples of them will be found in the text. A list of terms is given below.

Figures and plates

Figures

(Figure 1) Sketch-map of the Midlothian Coalfield

(Figure 2) Generalized section of the rocks of the Midlothian Coalfield

(Figure 3) Generalized section of the Calciferous Sandstone of Midlothian 2—(120)

(Figure 4) Map showing the positions of the principal shafts and bores in the area

(Figure 5) Comparative vertical sections of the Oil-Shale Group in the Lothians

(Figure 6) Diagram showing details of the strata between the Bone Bed and Gilmerton limestones

(Figure 7) Isopachytes of the Lower Limestone Group

(Figure 8) Generalized sections of the Lower Limestone Group showing suggested correlations with Fife, West Lothian and East Lothian

(Figure 9) Generalized section of the Limestone Coal Group showing possible correlations with the Fife succession

(Figure 10) Isopachytes of the Limestone Coal Group

(Figure 11) Correlation of the Limestone Coal Group across the Main Syncline of the Midlothian Coalfield

(Figure 12) Comparative sections of the Great Seam

(Figure 13) Isopachytes of the Upper Limestone Group

(Figure 14) Comparative sections of the Roslin Sandstone Group

(Figure 15) Generalized section of the Productive Coal Measures

(Figure 16) Comparative sections of the upper part of the Productive Coal Measures

(Figure 17) Contour map of the Great Seam and the Nine Foot Coal

(Figure 18) Map of the principal faults, folds and dykes

(Figure 19) Sections across the Midlothian Coalfield

(Figure 20) Map showing the principal deposits of sand and gravel

Plates

(Plate 1) (Frontispiece) Bilston Glen Colliery during construction In the distance to the south-west are the Pentland Hills, consisting of volcanic rocks of Lower Old Red Sandstone age.

(Plate 2) Comparative sections of the Lower Limestone Group

(Plate 3) Comparative sections of the Limestone Coal Group

(Plate 4). Comparative sections of the Upper Limestone Group

(Plate 5). Comparative sections of the Productive Coal Measures

(Front cover)

(Rear cover)