Content and licensingview original scan buy a printed copy

Geology of the Falkirk district Memoir for 1:50 000 geological sheet 31E (Scotland)

By I B Cameron, A M  Aitken, M A E Browne, and D. Stephenson

Bibliographical reference: Cameron, I B, Aitken, A M, Browne, M A E, and Stephenson, D. 1998. Geology of the Falkirk district. Memoir of the British Geological Survey, Sheet 31E (Scotland).

British Geological Survey

Geology of the Falkirk district: Memoir for 1:50 000 Geological Sheet 31E (Scotland)

D F Ball, M T Dean, E R Phillips, K E Rollin, R A Smith

Contributors: D F Ball, M T Dean, E R Phillips, K E Rollin, R A Smith

London: The Stationery Office 1998. NERC copyright 1 998 First published 1998. ISBN 0 11 884541 1. Printed in the UK for The Stationery Office J61729 C6 6/98

The grid used on the map figures is the National Grid taken from the Ordnance Survey map with the permission of The Controller of her Majesty's Stationery Office. (Figure 2) is based on material for OS 1:50 000 scale maps, number 65.

Acknowledgements

Notes

Preface

Geology underpins a wide range of activities vital to the creation of wealth, particularly in relation to the exploration for and exploitation of resources. It is also vital that we have the best possible understanding of the geology of the United Kingdom if we are to maintain the quality of life whether through the identification of potential hazards prior to development or helping to ameliorate problems occurring after development. The British Geological Survey is funded by central government to improve our understanding of the three-dimensional geology of the UK through a national programme of geoscience surveying, data collection, interpretation, publication and archiving. One aim of this programme is to ensure coverage of the UK land area by modern 1:50 000 geological maps, mostly with explanatory memoirs, by the year 2005. This memoir, which describes the geology of the Falkirk district of the Midland Valley of Scotland, is part of the output from that programme.

The past development and early prosperity of the district resulted from its favourable geology. Resources of coal, ironstone, fireclay and limestone provided the raw materials for the industrialisation of central Scotland which began in 1760 when the Carron Ironworks started smelting local coal and ironstone. Opencast exploitation of the coal continues to the present day. However, this past development is also the cause of many present-day problems in the region and detailed knowledge of the abandoned underground mine workings is essential when planning for development. Therefore just as geology was vital to the past development of the Falkirk district so it is essential to its future prosperity and well-being.

The area described is part of the now largely inactive Central Coalfield of Scotland. This is the first general account of the geology of the area since the original brief 'Explanation of Sheet 31' was published in 1879 which covered both the Falkirk (31E) and Airdrie (31W) districts.

The rocks at outcrop in the area are all of Carboniferous age and are largely obscured by unconsolidated deposits of Quaternary age. Although the exposure of these rocks is poor, much is known from mining records particularly the records of boreholes drilled during the search for and exploitation of coal and ironstone.

Volcanic activity during the early part of the Carboniferous contributed to the unusual conditions of deposition of the Viséan East Kirkton Limestone and to the unique preservation of a fossil terrestrial community which included insects, plants, fish and other vertebrates.

The movement of Quaternary glaciers across the area moulded the rock surface and deposited glacial detritus. Isostatic recovery after the retreat of the ice caused marine deposits to be raised above sea level leaving extensive areas of flat-lying 'carse' in the north-east of the area.

Resources of coal, limestone, fireclay, sand and gravel and hard rock aggregate remain and will be available for exploitation by future generations.

David A Falvey, PhD Director. British Geological Survey Kingsley Dunham Centre Keyworth, Nottingham. NGI2 5GG

Geology of the Falkirk district — summary

The district described in this memoir is in central Scotland, between Glasgow and Edinburgh and includes the towns of Falkirk, Grangemouth, Bathgate and Shotts.

The eastern part of the area includes the scenically attractive volcanic uplands between Linlithgow and Bathgate and, in the north, the low-lying flat 'carse' lands bordering the Forth estuary. The rest of the area forms part of the now largely inactive Central Coalfield of Scotland.

The rocks at outcrop are all of Carboniferous age and include the principal coal-bearing formations of the Midland Valley, the volcanic rocks of the Bathgate Hills and the Midland Valley Sill. Early mining in the area provided the coal and ironstone on which the industrialisation of Scotland was founded. The extraction of coal has now almost ceased but the effects of mining remain and a detailed knowledge of the location of abandoned mine workings is essential for planning and construction. The strata, their structure and the fossils they contain are described. Fossils of particular interest have been found recently in a quarry near Bathgate. Items collected include fossil insects, scorpions, plants, fish and other vertebrates.

During the Quaternary the district was subjected to glaciation on at least one occasion. An account is given of the effects of the movement of glaciers over the landscape and the deposits left by the ice and by glacial meltwater are described. The flat 'carse' lands were raised above sea level as the land rose when relieved of the weight of the ice.

The local occurrence of economic minerals is described, including coal, fireclay, moulding sand, sand and gravel, rock aggregate and peat.

This memoir will be a useful reference for those with a geological interest in the district and for comparison with other areas. It will also be useful for planners and civil engineers involved in development and construction in an area where there are particular foundation problems posed by old underground workings. There is also a need to plan development so as to avoid the unnecessary sterilisation of limited resources.

(Table 1) Geological succession in the Falkirk district

(Front cover). Cover photograph. Linlithgow Place [NT 003 773] birthplace of Mary, Queen of Scots, situated on a promontory on the south side of Linlithgow Loch. The underlying rocks are basaltic lavas of the Bathgate Hills Volcanic Formation. (D5075. (Photographer F.I. MacTaggart)

Chapter 1 Introduction

This memoir describes the geology of the Falkirk Sheet (31E) of the Geological Map of Scotland. The map is published at the 1:50 000 scale in two editions: a Solid with Drift edition and a Solid edition. The area concerned and its regional setting are shown in (Figure 2 and (Figure 29).

The Falkirk district lies in the eastern part of the Central Coalfield of the Midland Valley of Scotland. The rocks at outcrop are all of Carboniferous age and they form a broad asymmetric north-south syncline in which the strata on the eastern flank are notably more steeply inclined than those on the western flank. The structure is known as the Clackmannan Syncline to the north of Falkirk and the Falkirk-Stane Syncline to the south. The strata include seams of coal and ironstone which were mined in many parts of the district. Oil shales were also worked in the south-eastern part of the district on the western margin of the West Lothian oil shale field. Mining was at one time the principal occupation and coal and ironstone were the foundation of the industrialisation of the district.

In the east of the district volcanic rocks were extruded contemporaneously with the Carboniferous strata and ultimately formed the Bathgate Hills, one of the more scenically attractive parts of the district.

The district was affected by glaciation during the Quaternary Period, and glacial erosion and deposition are responsible for the present-day topography.

Opencast coal mining continues in the area but underground mining has now almost ceased. However, extensive abandoned underground workings, especially the earlier near-surface workings, have left ground which presents problems for new development and construction. Aspects of geology affecting land use planning are treated in a series of Technical Reports, each accompanied by a suite of thematic maps. These are listed in Information sources.

Area and physical features

The Falkirk district lies roughly equidistant between Edinburgh and Glasgow (Figure 29). The general topography of the district is shown in (Figure 2). The highest ground is in the south where rounded moorland hills rise to over 300 m above OD. The highest points are Hendry's Corse (359 m) and Leven Seat (356 m). A broad area of ground over 200 m high extends north-westwards across the district from the south-east corner, forming the watershed between drainage to the east and north-east into the Forth basin and drainage to the west into the Clyde basin. Another area of relatively high ground occurs near Bathgate on the eastern edge of the area. Various processes of erosion acting on the outcrop of the more resistant volcanic rocks which form the Bathgate Hills have resulted in the formation of one of the more scenically attractive parts of the district. The highest of the Bathgate Hills is the unnamed hill (312 m) to the south of Cairnpapple Hill (310 m).

The effect of glaciation on the landscape has been to superimpose on the broad-scale topography a system of mounds and ridges with a north-east to south-west alignment. The latter has had some effect in controlling the course of minor streams.

Large areas of flat-lying, low ground, generally less than 20 m above OD, occur in the north-east of the district, bordering the upper reaches of the Firth of Forth. These flat-lying areas, known as the carse, are underlain by raised marine sediments, and are limited on the landward side by a former coastline (Plate 1).

The elevation of the land which formed the carse also rejuvenated the down-cutting ability of the rivers in the area to the south of Falkirk and Bo'ness. The River Avon and a number of lesser streams have incised themselves into the rock and in the case of the Avon formed a gorge.

The Antonine Wall, built by the Romans about AD 142, crosses central Scotland from Bridgeness on the Forth to the Clyde at Old Kilpatrick, passing through the district to the south of Falkirk and Bonnybridge. The siting of the wall was influenced locally by geological factors. It was built on the crest of the back-feature of the raised beach between Bridgeness and Falkirk where it gave a commanding position overlooking the low flat ground to the north (Plate 2).

Through routes from east, west and north have long converged on the area around Falkirk. Several of the old drove roads met in this area and cattle trading took place annually at the Falkirk Tryst on a site near Stenhousemuir. Subsequent highways were established following the ancient ways and later the Forth and Clyde Canal, the Union Canal and the railways were built on very similar routes. Now motorways to the west, east and north take the bulk of the traffic.

The industrialisation of the district started in the latter half of the eighteenth century and was based on the smelting of iron. Prior to 1760 iron was smelted in areas where wood for making charcoal was plentiful using imported haematite ore. The small charcoal furnaces gave way to ironworks using coal to smelt bedded iron ores. The Carron Ironworks began operating in 1760 using locally won coal and clayband ironstone. The mining of coal and ironstone spread to many parts of the district and the landscape today bears the scars of over two hundred years of mining. Ironstone mining declined rapidly after the First World War and coal mining is now mostly limited to opencast excavations. Deep mining of coal for power station use continues from the Longannet Complex, just outside the district to the north, taking coal from under the Forth. Most of the district is underlain by coal-bearing strata.

Outline of geological history

The district lies in the Midland Valley of Scotland between the Highland Boundary Fault to the north and the Southern Upland Fault to the south. The Midland Valley is considered to be a displaced 'terrane' emplaced in its present relationship with the Highlands and Southern Uplands by large-scale sinistral strike-slip movement during the end-Silurian to mid-Devonian interval (Hutton, 1987). Since then the Midland Valley has been a north-east- to south-west-orientated basin downfaulted between the Highlands and the Southern Uplands.

The nature of the basement rocks in the Midland Valley is known only from indirect evidence (Bamford, 1979). Geophysical studies indicate that a metamorphic basement lies at a depth of between 7 and 9 km. The basement is 20 to 25 km thick and the base of the crust is at a depth of about 33 km. The composition of the basement is indicated by the occurrence of metamorphic fragments carried to the surface as xenoliths in volcanic vents (Upton et al., 1983). These rocks range in composition from ultramafic granulites through anorthosites to quartzofeldspathic granulites.

The oldest rocks encountered in drilling within the district are believed to be of Lower Devonian age. Falcon and Kent (1960) noted red and purple tuffs overlying white trachyte with feldspar phenocrysts at 1231m in a borehole near Salsburgh [NS 817 649]. These were compared with the acid lavas of the Lower Devonian.

All rocks at outcrop in the district are Carboniferous in age (Figure 1). The oldest are Viséan and consist of sandstones, mudstones, oil shales, coals and basaltic lavas. Subaerial volcanic activity was widespread in the Midland Valley in Lower Carboniferous times. A large area of basaltic lava occurs at outcrop to the west of the district and is known to extend eastwards into the district where it occurs at depth buried beneath younger strata. Lavas also occur at outcrop in the vicinity of the Bathgate Hills in the east of the district. Eruption in the west ceased sometime in the Viséan, but persisted in the east well into the Namurian. The geological succession in the Falkirk district is given in (Table 1).

The sedimentary strata consist principally of sandstones and mudstones with relatively minor proportions of limestone, coal and, in the oldest rocks, oil shales.

They were deposited as part of a very extensive fluviodeltaic system which occupied most of north-west Europe during the Carboniferous. Sediment was carried from Caledonian mountains to the north and deposited at or near sea level in a differentially subsiding basin. Early Carboniferous strata were deposited, in part at least, under lagoonal conditions and the strata include seams of oil shale. Cyclic sedimentation, including the deposidon of seams of economically valuable coal, lasted from the Viséan to the late Carboniferous. Periodic marine incursions brought about the deposition of thin but widespread limestones mainly in the late Viséan Lower Limestone Formation and in the Namurian Upper Limestone Formation. In the area of the Bathgate Hills, marine limestones of Viséan age were deposited fringing volcanic islands. An unusual fauna has been recently been recovered from one of the associated nonmarine limestones which included the earliest known reptile, amphibians and various terrestrial invertebrates (Wood et al., 1985; Rolfe at al., 1994a).

A period of uplift and erosion in the source area and within the Midland Valley brought about mainly fluvial deposition during late-Namurian Passage Formation times, temporarily replacing the fluviodeltaic processes. Marine incursions were brief and largely confined to the lower part of the formation.

Two episodes of basaltic intrusion are known in the district. Most of the intrusive igneous rocks are quartz-dolerites which occur as east-west dykes and sills. They are of late-Carboniferous age. An alkali-dolerite sill, probably of Namurian age, is present in the Lower Limestone Formation in the south-east of the district.

After deposition of the Carboniferous, the strata were folded to form the Clackmannan Syncline in the north and its southwards continuation, the Falkirk-Stane Syncline. Faulting took place on east-west faults.

Little is known of the geological history of the district during the interval between Carboniferous times and the Quaternary.

During the Quaternary the entire region was overwhelmed by glaciers, probably on more than one occasion. The overall west to east movement of the ice is recorded in the erosional effects on the higher ground and in the orientation of the elongate features in the ground moraine. Changes in relative sea level after the disappearance of the ice permitted the emergence of shallow marine deposits which form the raised beaches seen in the north-east of the district, bordering the Firth of Forth.

Chapter 2 Viséan

Viséan rocks occur at outcrop in the eastern part of the Falkirk district but they are probably present at depth throughout the district. The outcrop lies on the eastern limb of the broad north-south synclinal structure which controls the pattern of outcrop distribution in the district. The northern part of the syncline is known as the Clackmannan Syncline and to the south of Falkirk it is called the Falkirk-Stane Syncline.

Rocks of Viséan age include strata of the West Lothian Oil Shale Formation, the Lower Limestone Formation, the Bathgate Hills Volcanic Formation, the Salsburgh Volcanic Formation and the Clyde Plateau Volcanic Formation. The last two formations are known only from boreholes in the western part of the district. Volcanic rocks of the Bathgate Hills Volcanic Formation take the place of much of the West Lothian Oil Shale and Lower Limestone formations in the Bathgate Hills area, and in the Rashiehill Borehole [NS 8386 7301] in the western part of the district. The volcanic formations are described in Chapter Six. The lithostratigraphical classification and its relationship to the chronostratigraphy are given in (Table 2).

The base of the Viséan is unknown in the district but the top occurs just below the Top Hosie Limestone, close to the top of the Lower Limestone Formation (Currie, 1954). Only the two youngest stages of the Viséan, the Asbian and Brigantian stages, are known to be present.

According to Leeder (1988) the Viséan ranges in age from 350 to 326 million years (Ma) and the base of the Asbian is estimated to be 335 Ma. The oldest lavas of the Clyde Plateau Volcanic Formation may be about 350 Ma.

During the Viséan the Midland Valley of Scotland lay in equatorial latitudes (Smith et al., 1981) south-east of the North American-Scottish-Scandinavian Caledonides continent. Overall, the climate was hot but changed from semi-arid early in the Dinantian to wet year-round. Sediment derived mainly from the north was deposited by alluvial, lacustrine and deltaic processes in an extensive low-lying area subject to periodic marine transgression especially in the late Viséan. Deposition was significantly influenced by two episodes of contemporaneous volcanism and by differential subsidence.

West Lothian Oil Shale Formation

The West Lothian Oil Shale Formation crops out in a small, largely drift-covered area south-east of Bathgate (Figure 1). Northwards from Bathgate it interdigitates with and is replaced by rocks of the Bathgate Hills Volcanic Formation. Elsewhere it is concealed by younger strata. The strata are known mainly from borehole information in the western margin of the former West Lothian oil shale field to the south-east of Bathgate, from a few deep boreholes in the western part of the district and from two mine shaft sections in the Bo'ness area.

In the south-east of the district the oldest known horizon at outcrop is the Broxburn Shale, but strata down to just below the Barracks Limestone are known from old borehole logs, some of which are of doubtful reliability (Figure 7)." data-name="images/P941462.jpg">(Figure 3) and (Figure 7)." data-name="images/P941463.jpg">(Figure 4).

In the north-east corner of the district, sections in the Viséan in the Kinneil Colliery No. 1 [NS 9868 8120] and No. 2 [NS 9880 8127] shafts at Bo'ness prove only the uppermost strata down to the Raeburn Shale. However, the Blackness No. 2 Borehole [NT 0471 8027], about 4 km east of the district, provides a record of most of the upper part of the formation from the Under Limestone down to the Burdiehouse Limestone.

In the western half of the district, the Salsburgh No. 1A [NS 8166 6487] and Craighead No. 1 [NS 8267 6212] oilwells provide the only information about the West Lothian Oil Shale Formation. In the No. 1A Well, the lower part is replaced by volcanic rocks of the Salsburgh Volcanic Member (Chapter 6). A limestone overlying the volcanic rocks at a depth of 1111 m is correlated with the Burdiehouse Limestone. However, as there are two other similar limestones not far below, intercalated in the Salsburgh Volcanic Member, this correlation is uncertain. In the Rashiehill Borehole [NS 8386 7301] 10 km to the north of these wells, the whole formation is similarly replaced by volcanic rocks.

In the eastern half of the district, therefore, the nature of the lower part of the formation can only be inferred from the adjacent Lothian sequence (Chisholm et al., 1989, fig. 1). In the western half of the district the upper part of the formation rests on volcanic rocks and the lower part is not present.

Classification

The formation was defined by Chisholm et al. (1989) and replaces the Upper Oil Shale Group and the upper part of the Lower Oil Shale Group of the former classification. It consists of a lower Calders Member and an upper Hopetoun Member. The base of these two constituent members are placed at the base of the Humbie Shell Bed and the base of the Burdiehouse Limestone respectively. The top of the formation is the base of the Hurlet Limestone, in the overlying Lower Limestone Formation.

In the chronostratigraphical classification the formation is partly Asbian and partly Brigantian. The base of the Brigantian Stage is believed to be about the base of the Raeburn Shell Bed.

The West Lothian Oil Shale Formation is equivalent to the Aberlady Formation in East Lothian (Chisholm et al., 1989) and is thought to be equivalent to the Pathhead, Sandy Craig and Pittemweem formations in East Fife (Forsyth and Chisholm, 1977).

In the miospore zonation of Neves et al. (1973) beds at the base of the formation (not known in the district) are in the top of the TC Zone. Beds up to the Houston Coal are in the NM Zone and the higher strata are in the VF Zone.

Lithology

The lower part of the West Lothian Oil Shale Formation, below the Raeburn Shell Bed consists characteristically of lake-bed and deltaic mudstone and siltstone. Bituminous mudstone and oil shale are minor components. Non-marine, commonly bioclastic limestone and dolomite are also developed usually as thin beds normally associated with the argillaceous rocks. Oncolites and stromatolites are found in some of these carbonates. As minor components within the Formation, marine mudstone and siltstone may locally be present. Off-white to grey, in places, reddish brown or purplish grey, fine- to medium-grained, in some cases, coarse and pebbly sandstone is generally subordinate to the argillaceous rocks. Locally, thick, upward-fining, multi-storey channel sandstones are developed. Seatearth, seatclay and unbedded, commonly greenish grey clayrocks and calcareous marls occur together with thin beds of coal, and blackband and clayband ironstone.

The overall pattern of sedimentation within the lower part of the West Lothian Oil Shale Formation is of upward-coarsening lake (rarely marine) delta cycles, with thinner upward-fining fluvial units erosively capping them. However, a significant proportion of the argillaceous rocks was deposited in periodically waterlogged wetlands as seatrocks and marls. The abundant nomarine faunas are of Curvirimula, estheriids, spirorbids and ostracods.

The upper part of the West Lothian Oil Shale Formation, from the base of the Raeburn Shell Bed to the base of the Hurlet Limestone, consists typically of black to grey mudstone and siltstone. Part is of marine shelf and deltaic origin, with marine bioclastic limestone and dolomite also developed as thin beds within the mudrocks. Part is nonmarine with rare thin, lacustrine limestones interbedded. Off-white to grey, fine- to medium-grained, in some places, coarse and pebbly sandstone is generally subordinate to the argillaceous rocks. Locally, upward-fining, multi-storey channel sandstones are developed. Seatearth and seatclay, together with thin beds of coal, blackband and clayband ironstone, bituminous mud-stone and oil shale also occur.

The overall pattern of sedimentation within this part of the formation is of upward-coarsening deltaic cycles, with thinner upward-fining fluvial units erosively capping them. The marine faunas are usually diverse and abundant. The nonmarine faunas are of Curvirimula, estheriids, and ostracods.

The freshwater limestone which overlies the Salsburgh Volcanic Formation in the Salsburgh No. 1A borehole is tentatively correlated with the Burdiehouse Limestone. Oncolites and stromatolites are found in some of these freshwater carbonates.

Stratigraphy

Lower part of formation in Salsburgh area

In the Salsburgh area, the lower part of the formation, below the base of the Raeburn Shell Bed has only been proven in two deep, largely open-holed oilwells. At the local base of the formation, resting on the Salsburgh Volcanic Formation, is a 3.4 to 6.5 m-thick limestone, tentatively correlated with the Burdiehouse Limestone (Figure 7)." data-name="images/P941462.jpg">(Figure 3). It is a bituminous, siliceous, partly ashy, pale to dark grey, banded lacustrine carbonate with ostracods. Unlike the two limestones interbedded with the volcanic rocks below, there is no indication that it contained macroscopic algal remains, although it is likely to be partly algal in origin.

The strata above this limestone up to a 3.7 m-thick oil shale, possibly the Dunnet Shale, is about 96 to 100 m thick. The sequence consists largely of mudstone with some oil shales, siltstone with some thin and thick (12 m) beds of lacustrine limestone (oolitic in places), ironstone, marl and volcanic ash. Little sandstone is present. The marl and ash are found only in the lowest 40 m and are overlain by a thin limestone supposedly correlated with the Barracks Limestone.

The interval between the Dunnet Shale and the Two Foot Coal above the Houston Marls is about 134 to 152 m. The strata consist largely of mudstone and siltstone with some beds of limestone up to 3 m thick, volcanic ash and marl. Some beds of oil shale are present but they cannot confidently be correlated with the Fells or Broxburn shales. Sandstone is uncommon and restricted to the basal part of the interval. Marls and cementy limestone beds are concentrated in the top 48 m and this part of the succession includes the position of the Houston Coal and also the Houston Marls. The marls are between 27 and 45 m thick and there may be a thin lava flow at the base.

The interval between the Two Foot Coal and the base of the Racburn Shale is about 72 to 84 m. The strata consist of sandstone with subordinate amounts of siltstone, mudstone and marl. Ashy beds are recorded and traces of coal. The Mungle Shale may be present about 20 to 30 m below the top of the interval.

Upper part of formation in Salsburgh area

The interval between the base of the Raeburn Shale and the floor of the Hurlet Limestone is between 156 and 175 m. It consists of mudstone with oil shales, and siltstone with subordinate beds of manly fireclay and some sandstones usually less than 8 m but up to 15 m thick. Thin coal seams are present, as are thin marine and lacustrine limestones rarely up to 0.6 m thick. The Raeburn Shale and its associated mudstones are up to 19 m thick, the oil shale itself being perhaps 2 m in thickness and located near the top. The Raeburn Shell Bed marine band has not yet been proved in the Salsburgh area, nor have the overlying Fraser or Basket Shell Bed marine bands. The Fraser Shale itself is poor and represented by 6 to 10 m of mudstone and inferior oil shale. The base is about 60 to 70 m above the top of the Raeburn Shale. The Basket Shell Bed may be represented by about 3 to 5 m of mudstone with a bed of limestone about 0.6 m thick in the Craighead No. 1 Borehole.

About 39 to 43 m below the Hurlet Limestone and Coal is the 0.6 m-thick Under Limestone. It is crinoidal in part and overlain by about 14 to 23 m of argillaceous rocks. Towards the top of these beds there are impersistent thin limestones that may represent the lacustrine horizon found in the Bathgate area. The Under Limestone locally is underlain by a 3 m-thick basalt lava. The Hurlet Coal is poorly developed and is described as coal and coaly mudstone in 0.6 m of strata.

Upper part of formation in Bo’ness area

The limited data available from the Kinneil Colliery Nos. 1 and 2 shafts suggests that the upper part of the West Lothian Oil Shale Fomation in the Bo'ness area is relatively thin. The proven succession, from the base of the Raeburn Shale up to the base of the Hurlet Limestone, is about 118 m thick. This compares with an estimated thickness of 170 m in the Blackness No. 2 Borehole on the Livingston district (Sheet 32W) to the east, 156 to 175 m in the Salsburgh area to the west, 160 m in Baads Mine No. 1 Borehole [NS 9973 6099] in the south and 132 m in the Cobbinshaw area just out of the district to the south.

The generally argillaceous succession in the Blackness No. 2 Borehole is summarised in (Figure 7)." data-name="images/P941464.jpg">(Figure 5). The estimated interval between the Hurlet Limestone base and the top of the Burdichouse Limestone is about 335 m which expands eastwards to at least an estimated 385 m in the Blackness No. 1 Borehole [NT 0537 7953]. This contrasts with about 538 m in the Cobbinshaw area where the succession below the Raeburn Shale is thicker.

In the Kinneil Nos. 1 and 2 shafts, the interval between the base of the Raeburn Shale and the base of the Hurlet Limestone is composed largely of argillaceous rocks including seatrocks and thin coal seams. Sandstone is uncommon and only one bed exceeds 6 m thick. One limestone has been found and three marine mudstones occur.

The Raeburn Shale mudstone is at least 15 m thick with vestiges of shells, perhaps the Raeburn Shell Bed, above the roof of the underlying quartz-dolerite sill. The Fraser Shell Bed has been found in both the No. 1 and No. 2 shaft sections and is characterised by Posidonia becheri with goniatites. The base of this marine band is about 36m above the top of the Raeburn Shale mudstone. Above the Fraser Shell Bed, are marine mudstones containing Naiadites sp., Sanguinolites and Estheriids. About 6 m above the base of the Fraser Shell Bed, is the Basket Shell Bed with a 0.6 m-thick crinoidal limestone. The 12 m of argillaceous strata above the Basket Shell Bed contain Curvirimula scotica and Estheriids.

Although a mudstone containing Spirorbis sp. occurs about 21 m below the Hurlet Limestone, there is no trace of any lacustrine limestone or of the marine Under Limestone which are known farther south. Below the marine mudstone and thin coals that underlie the Hurlet Limestone is a succession up to 15 m thick dominated by rocks with rootlets including seatclays. As in the adjacent Dunfermline area, north of the Firth of Forth, the Under (No. 1 Abden) Limestone is either not developed or destroyed by pedogenic processes.

Lower part of formation in Bathgate-Addiewell area

The Burdiehouse Limestone has not yet been proved in this part of the district but in the Harburn mines [NT 0410 5843] just to the east, it was recorded as cream or grey, with conchoidal fracture and over 9 m thick. At least 77 m of mainly sandy strata have been shown to be present between this horizon and the Dunnet Shale which ranges between 1.3 and 4 m in thickness. The Upper Dunnet Shale, 1.4 m thick, has also been recognised in one borehole about 7.5 m above the Dunnet. The Under Dunnet, with the marine Dunnet Shell Bed, has not yet been identified in this area. However, to the south-east, a mudstone with Lingula appears at this level in the Cobbinshaw Hill No. 26 Borehole [NT 0317 5729]. In this same borehole, the Barracks Limestone, 0.25 m thick, has been recognised with a thin bed of volcanic ash immediately above. In the Redhouse No. 8 Borehole [NS 9988 6573], the Barracks Limestone is about 1.9 m thick and lies about 12 m below the Dunnet Shale. The largely argillaceous interval between the Dunnet Shale and the Broxburn Shales is 57 to 66 m thick. The Broxburn Shales commonly occur in one or two seams with an aggregate thickness ranging. Some records note the occurrence of ‘curly shale’.

The Fells Limestone, only up to 54 cm thick, is 36 to 45 m above the Broxburn Shales. In this argillaceous interval the Broxburn Marls have only rarely been identified as perhaps 2.5 m thick. The Fells Shale, 1 to 3 m above the limestone, is usually 1 m thick and is separated from the Houston Coal above by about 45 m of largely argillaceous strata. The Houston Coal, which in places is in two leaves and of inferior quality, ranges in thickness from 0.6 to 2.0 m. The 0.30–0.45 m-thick Grey Shale, with the underlying 0.30–0.45 m-thick Upper Coal, is about 4 to 5 m above the Houston Coal.

The interval between the Houston Coal and the Two Foot (Stewart's) Coal is about 61 m and consists of red, green and dark grey argillaceous seatrocks and marls, including the Houston Marls. The Two Foot Coal at the top ranges in thickness from 0.4 to 0.6 m. It is of inferior quality. The succession between this coal and the Raeburn Shale is unknown. The interval between the Two Foot Coal and Mungle is estimated to be 25 to 43 m, and that between the latter and the Raeburn Shale to be 33 to 36 m. The Dunnet Shale and to a lesser extent the Fells and Broxburn Shales were worked south of Blackburn. é

Upper part of formation in Bathgate-Addiewell area

The Raeburn Shale to Hurlet Limestone interval has only been satisfactorily proved in the Baads Mine No. 1 Borehole [NS 9973 6099]. The marine Raeburn Shell Bed was not reached by this borehole but is expected to be developed in this area. The Raeburn Shale was less than 0.6 m thick. The interval between the Raeburn and Fraser shales is 13 to 41 m and is essentially argillaceous with clay ironstone nodules and bands, and thin coal seams associated with seatrocks. The Fraser Shale, which was worked to a small extent south of Blackburn, is 1.1 m thick and is underlain by the goniatite-bearing mudstone of the marine Fraser Shell Bed. The marine band has a 0.45 m-thick crinoidal limestone near its base, but Lingula is present in the mudstone immediately beneath.

The interval between the Fraser Shale and the marine Basket Shell Bed is about 33 m thick. The lower part is sandy and the upper muddy. Seatrocks are common throughout with some green or red-mottled marls. A coal seam, 0.4 m thick, occurs immediately below the Basket Shell Bed which is up to 3 m thick. There is a thin marine limestone rib near the top. The rich fauna includes goniatites. Neither the coal nor the limestone are present in the Wilsontown Diamond Borehole [NS 9518 5564] to the south, 1 km within the Lanark district (Sheet 23E).

Above the Basket Shell Bed is a further 40 to 50 m of mainly bedded argillaceous strata with a few clayband ironstones and with seatrocks containing several thin coal seams in the top 6 m. Above the thickest seam (30 cm) is a marine mudstone containing, near its top, a partly crinoidal limestone, This is the Under Limestone which is only 0.2 to 0.3 m thick and in one or two leaves. This limestone is about 13 m above the Basket Shell Bed.

The interval between the Under Limestone and the base of the Hurlet Limestone is 27 to 51 m. The former thickness was proved in the Wilsontown Diamond Borehole, In the Baads Mine No. 1 Borehole, the lower part is argillaceous and the upper is more sandy. A 0.33 m-thick coal lies 21 m above the Under Limestone. It is overlain by muddy strata containing a 0.53 m-thick, possibly lacustrine cementy limestone about 1.3 m above the coal. Thin beds of ironstone and oil shale are also present. The only fauna reported was of ostracods from the mudstones.

About 11 m above the same coal, is another 0.4 m-thick lacustrine limestone containing spirorbids, ostracods and rootlets. This bed may be the same as the 0.3 m-thick ostracod limestone exposed in the Breich Water [NS 9920 0294] near Addiewell and in the River Almond [NS 9914 6524] near Blackburn. Any of these limestones might reasonably be correlated with the non marine Baldernock Limestone of the Glasgow area but continuity in any case seems unlikely. Only one limestone, about 3,5 m thick, with ostracods and spirorbids, is present in the interval above the Under Limestone in the Wilsontown Diamond Borehole. It is about 4 m below the coked HurletCoal.

In the Baads Mine No. 1 Borehole, the Hurlet Coal, in three leaves, is 1.55 m thick and is almost directly overlain by the Hurlet Limestone at the base of the overlying Lower Limestone Formation. This development of the coal and its relationship to the Hurlet Limestone is reasonably typical for the area. However, to the east, as the flows and ashes of the Bathgate Hills Volcanic Formation become interbedded, the Hurlet Coal is known to be absent. Where developed, this seam varies in thickness between 1.1 and 2.4 m. The top leaf may be separated from the Hurlet Limestone by up to 4.0 m of mudstone. The three leaves may be almost fused or variably spread within 3 m of strata. The coal was worked fairly extensively south of Blackburn.

East Kirkon Limestone

The East Kirkton Limestone represents a development of nonmarine limestone belonging to the West Lothian Oil Shale Formation intercalated within the Bathgate Hills Volcanic Formation (Figure 6). It lies stratigraphically below the Hurlet Limestone but its stratigraphical relationship to the Under Limestone is not known. The East Kirkton Limestone is only exposed at a disused quarry [NS 990 690] at East Kirkton ((Figure 6); (Plate 3)). At this locality it dips 20 to 45° to WSW. The limestone and mudstone sequence is between 9 and 19 m thick, comprising mainly laminated limestone with some nodular, spherulitic and massive limestone beds and lenses interbedded with black mudstones, thin ironstones and reworked tuffs. The limestone contains siliceous laminae and lenses of chert which may be the result of contemporaneous hot spring waters (Plate 4). Locally within the limestone beds there are stromatolites, clusters of gypsum crystals and thin lenses of coal. Within the black mudstone and laminated limestone beds, there is a sparse but diverse terrestrial early fauna and flora which has recently (1985–1992) been extensively collected and studied by a team from the National Museums of Scotland (Rolfe et al., 1994a).

The bulk of the fossils consist of plants (gymnosperms and pteridosperms) and dominantly land-living animals, including the oldest known terrestrial tetrapods (amphibians and reptilomorphs) (Plate 5), terrestrial/aquatic eurypterids, scorpions, millipedes, a mite and a harvestman. Charred wood fragments occur within this sequence and suggest that the surrounding forest was subject to forest fires which may have driven the land animals to their deaths in the lake.

The overlying shaley mudstone and reworked tuff contain, besides ostracods and bivalves, a relatively diverse fish fauna which is more typical of the formation and it is inferred that the water body had become connected to the larger Lake Cadell (Loftus and Green-smith, 1988). This suggests that the East Kirkton Limestone was the result of temporary lacustrine conditions with an exceptional chemistry allowing preservation of a terrestrial fauna but lacking the normal aquatic fauna.

Lower Limestone Formation

The Lower Limestone Formation crops out only on the eastern margin of the district (Figure 1) and (Figure 7) from near

Bathgate southwards to Woolfords. From Bathgate northwards, the formation is largely replaced by the Bathgate Hills Volcanic Formation. Away from the outcrop, borehole data are scarce and available mainly from Kinneil Colliery in the Bo'ness area, and from around Salsburgh and Rashiehill on the western margin of the district.

The standard stratigraphical nomenclature for the Lower Limestone Formation has now been applied throughout the district (Table 3). The detail of the relationship where this formation interdigitates with the Bathgate Hills Volcanic Formation is seen both at outcrop in the Bathgate Hills and in a few of the deeper borehole records such as Salsburgh No. 1A and Rashiehill. Information from mineral exploration drilling in the Bathgate Hills has clarified the correlation of the standard limestone names with those used within the volcanic succession (Stephenson, 1983b; Smith et al., 1994). The local successions are summarised in (Figure 8).

Classification

The rocks of the Lower Limestone Formation are the youngest Viséan strata in the district. They have been assigned on palaeontological grounds to the Brigantian Stage of the latest part of the Viséan Series. The base and top of the formation are approximately coincident with those of the P2 Goniatite Zone which forms the upper part of the Brigantian. The formation also includes the upper part of the VF and lowest part of the NC miospore zones. The poorly resolved boundary between the VF and overlying NC Miospore Zone lies near the top of the formation.

Lithostratigraphically, the Lower Limestone Formation is the lowest unit in the Clackmannan Group. The base of the formation is taken at the base of the Hurlet Limestone. The base of the overlying Limestone Coal Formation is at the roof of the Top Hosie Limestone or its local correlative.

The thickness of the Lower Limestone Formation is not well constrained but Browne et al. (1985) compiled conjectural isopachytes in the range of 100 to 150 m for most of the district (Figure 7). The thickness exceeds 200 m in the Harwood-Blackburn area on the eastern margin of the district. Only three borehole records prove the fullthickness (Figure 8). In the Rashiehill Borehole the lowest part of the unit may be replaced by volcanic rocks. The thickness of the formation is 110 m in the Salsburgh No. 1A Oilwell and 124 m in the Craighead No. 1 Borehole in the west of the district. It is 194 m in the Harwood Mine No. 6 Borehole [NS 9902 5826] and an estimated 187 m in the No. 5 Borehole [NS 9936 5845] in the south-east of the district.

Lithology

The Lower Limestone Formation generally comprises limestone, mudstone, siltstone and sandstone in repeated cycles that coarsen upwards. Upward-fining cycles, lacking limestone, also occur. Both types of cycles may be capped by thin beds of seatclay or seatearth and coal. The limestones are almost exclusively marine and bioclastic, and are pale to dark grey in colour. The mudstone and siltstone are black to grey, while the sandstone is pale grey to off-white and usually fine- to medium-grained. Coal seams are few in number and usually thin, less than 0.3 m. Nodular clayband ironstone and limestone are well developed in the finer-grained rocks and calcareous mudstone is also present. Minor lithologies include cannel and black-band ironstone. Upward-fining parts of the succession, dominated by fine- to medium-grained sandstone, locally include pebbly coarse-grained sandstone. There are no thick multistorey sandstones.

The formation is predominantly of lower coastal plain, shallow-water marine origin as is shown by the presence of marine fossils in the limestones and many of the mudstones. Upper coastal plain lakes are represented by the few non-marine faunal bands known. However, largely marine deltaic environments are represented by the upward-coarsening cycles and delta distributary and fluvial ones by the upward-fining cycles. The marine deltas were probably of lobate form, based on the limited occurrence of lake deposits and of seatrocks and coal seams.

Stratigraphy

The stratigraphy of the formation is best described in two parts, recognising the considerable differences between the standard succession and that of the volcanically dominated Bathgate Hills sequence.

Standard sequence

Hurlet Limestone to Blackhall Limestone

The Hurlet Limestone is a hard, dark grey to dark brown, locally shelly, crinoidal limestone usually in one leaf, ranging from L5 to 3.6 m in thickness. In places it is present as two leaves, each about 0.6 to 1.0 m thick, and separated by up to 4 m of mainly muddy strata. It is uncertain whether the 0.8 m-thick marine, calcareous mudstone immediately above the top of the Bathgate Hills Volcanic Formation in the Rashiehill Borehole at a depth of 792 m represents the Hurlet Limestone or the slightly higher Craigenhill Limestone. In the Bo'ness area, the Hurlet Limestone is 1.20 to 1.75 m thick.

The interval between the roof of the Hurlet and the floor of the Blackhall (Foul Hosie) ranges between 24 m in the Salsburgh No. 1A Oilwell to 97m in the Murrayfield No. 1 Borehole [NS 9875 6554]. It could be as little as 12 m in the Rashiehill Borehole (see above). At Salsburgh and Rashiehill the interval consists mainly of argillaceous rocks. South of the Bathgate Hills, the lower part of this interval, generally ranging between 35 and 45 m, consists mainly of marine mudstone with clay ironstone nodules, but also includes the Craigenhill Limestone. This apparently impersistent bed is up to 0.6 m thick and is found about 19 to 26 m above the roof of the Hurlet Limestone. The upper part of the interval is predominantly arenaceous with sandstones generally between 30 and 54 m thick. It consists of two to seven upward-coarsening cycles truncated by thicker upward-fining ones capped by thin coal seams. The coal seams are laterally impersistent, with none in some records and up to seven in others. These seams also vary in thickness but locally reach 0.8 m (in two leaves) but average only 0.3 m. They are of inferior quality. The Wilsontown Smithy Coal is the only named seam and is known to have been mined. In the Bo'ness area, the interval between the Hurlet and Blackhall limestones appears to be about 55 to 70 m thick. The 0.40–0.95 m-thick Craigenhill Limestone is about 14 to 25 m above the Hurlet Limestone.

Blackhall Limestone to Hosie limestones

The Blackhall Limestone is an earthy to hard, pale to dark grey or brownish grey, crinoidal limestone usually in one leaf from 1.37 to 3.70 m thick. In places it is present as two or more leaves, separated by beds of mudstone. The interval between the roof of the Blackhall Limestone and the floor of the Main Hosie Limestone ranges between 49 m in the Rashiehill Borehole to 77 m in the Cuthill No. 24 Borehole [NS 9859 6367]. This interval consists predominantly of marine muddy rocks with little sandstone and no coals. One or two impersistent thin limestones are known in this interval varying in thickness from 0.05 to 0.45 m and found 11 to 18 m, or 24 to 40 m above the Blackhall Limestone. These may correlate with the two fossiliferous marine mudstones found in this interval in the Rashiehill Borehole.

In the Bo'ness area, the Blackhall Limestone is 2.06 to 3.40 m thick. The interval between this limestone and the Main Hosie Limestone is 52 to 65 m and contains an impersistent limestone up to 0.6 m thick about 35 m above the Blackhall. This limestone, Carriden No. 4a, is probably represented by the Seafield Marine Band mudstone in the Kinneil Colliery No. 2 Shaft.

Hosie limestones

The Hosie limestones are rather variable, earthy to hard, pale to dark grey or brownish grey, crinoidal and in places shelly limestones. The named seams, Main, Mid, Second and Top, usually occur as single leaves from 0.15 to to 2.10 m thick but locally may not be developed. The Main Hosie ranges in thickness from 0.15 to 1.70 m, the Mid Hosie from 0 to 1.12 m, the Second Hosie from 0.36 to 2.10 m (in 3 leaves, the lowest of unfossiliferous cementstone), and the Top Hosie from 0 to 1.1 m. The interval between the Main and Top Hosie limestones usually consists largely of marine muddy rocks and varies in thickness from 16m in the Rashiehill Borehole to 23 m in the Jersay Bridge Borehole [NS 8300 6086]. However, where upward-fining channel sandstone is developed, usually between the Second and Top Hosie, the total interval increases to 44 m. The separation between the Second and Top Hosie increases from about 4 m to 29 m.

In the Forrestfield Borehole [NS 8604 6707], there is a 27 m-thick, garnetiferous, pebbly sandstone below the Second Hosie out of a total thickness of 43 m for the Hosie succession. In common with the sequence in the Glasgow and Airdrie districts, there is usually a thin coal seam or seatrock, midway between the Mid and Second Hosie limestones. This is the Lillie's Shale Coal which, where present, ranges from 0.12 to 0.38 m in thickness.

The Main Hosie Limestone, the lowest of the Hosie limestones, crops out in the River Almond south of Blackburn [NS 9863 6527] where over 0.6 m of crinoidal limestone is exposed. Earlier records indicate that 0.2 m of coal lies below this limestone. The overlying Hosie limestone succession is not exposed in this section but is known to be intruded by a picritic sill which continues south and crops out just east of the Skolie Burn [NS 9868 6238]. In the overlying, westward-dipping succession three limestones are intermittently exposed which are considered to correlate with the Mid, Second and Top Hosie limestones respectively. They are interbedded with black shaly mudstones, calcareous siltstones, and between the Second and Top Hosie, there is a coal 0.38 m thick.

In the Bo'ness area, the Main Hosie Limestone is 0.13 to 0.4 m thick, the Mid Hosie 0.25 to 1.45 m, the Second Hosie 0.85 to 1.20 m and the Top Hosie 0.35 to 1.73 m. The interval between the Main and Top Hosie limestones appears to range between 36 and 56 m. The Main and Mid Hosie limestones are 4 to 9 m apart, the Mid and Second 8 to 20 m, and the Second and Top 24 to 27 m. The variation in thickness between the Mid and Second Hosie Limestones is explained by the development of the Carriden Ash, locally more than 14 m thick. Below the Carriden Ash, an impersistent coal seam is developed which is correlated with the Lillie's Shale Coal. It is known locally as the Victory Coal and is usually 0.6 to 1.0 m thick in one to four leaves.

Bathgate Hills sequence

Hurlet Limestone to Blackhall Limestone

The Hurlet limestone has been mapped at the eastern margin of the district [NS 999 717], on the basis of the Mid Tartraven No. 4 Borehole [NT 0062 7254] in the vicinity of Mid Tartraven, just within the Livingston district to the east. The Hurlet Limestone was encountered 46 m below the Tartraven (Blackhall) Limestone which crops out at Mid Tartraven. The Hurlet Limestone in this borehole is 6.66 m thick, buff to grey, and massive with some crinoid and shell debris.

At West Kirkton [NS 988 690], a temporary exposure at the water board site showed the Hurlet (West Kirkton) Limestone resting abruptly on volcanic breccias and overlain by calcareous and tuffaceous sandstones. At the base of this carbonate succession is a fine-grained grey impure limestone followed by dark grey silty mudstones and thin limestones with crinoid ossicles and brachiopods. The succeeding granular to fine-grained tuffaceous sandstone, 2 m thick, is overlain by 5 m of bedded bioclastic limestone with minor cherty patches.

The Craigenhill Limestone horizon has not been positively identified in the Bathgate area, although there is a bed of limestone developed locally between lava flows, 25 m above the Hurlet Limestone at West Kirkton [NS 9880 6905]. The bed is possibly an upper leaf of the Hurlet Limestone but is not likely on stratigraphical and structural evidence to represent the Blackhall Limestone.

Blackhall Limestone to Hosie limestones

The Blackhall (Tartraven) Limestone has been identified in several sections and boreholes where it is overlain by the Neilson Shell Bed (Wilson, 1966; 1989). The limestone has been mapped at the eastern margin of the district [NS 998 720] on the evidence of boreholes put down near Mid Tartraven. In these boreholes, the limestone sequence is between 7.9 and 12 m thick and overlies a thin coal. The bulk of the limestone is bioclastic with abundant crinoid and some coral and bryozoan debris. However, the base of the limestone is darker, laminated and includes fissile calcareous mudstone which generally lacks fossils. This change in lithology could represent an upward change from lagoonal or estuarine conditions below to shallow-marine conditions, similar to the change described in the Blackhall Limestone around Paisley (Whyte, 1994). However, elsewhere in the district, the Blackhall Limestone includes Lingula and marine brachiopods at its base (e.g. Murrayfield No. 1 Borehole).

The continuation of the Blackhall Limestone southwestwards from the eastern margin of the district is tentative, and it may have been replaced by penecontemporaneous volcanic rocks. The Blackhall Limestone succession farther south, away from the influence of the Bathgate Hills volcanics, is partly exposed along the River Almond [NS 989 653] and Breich Water [NS 9886 6276].

Hosie limestones

Within the southern Bathgate Hills, the Petershill (Hillhouse) Limestone (Plate 6) and (Plate 7) is believed to be equivalent to the Main and Mid Hosie limestones. It is the thickest limestone in the succession and it is exposed in several disused quarries, e.g. [NS 984 695]. The limestone developed during an interval between outpourings of Bathgate Hills lavas. The succession has been described in detail by Jameson (1987) who established a lower, carbonate Reservoir Member and an upper, clastic Silver-mine Member. The carbonate member at Petershill has been interpreted in terms of a transgressive-regressive sequence with two periods of subaerial exposure marked by erosion surfaces. The transgression is marked by the carbonaceous shales containing Lingula towards the base of the member. The depositional environment, as identified by Jameson (1987), ranges from a shoreward lagoon to the north, passing southwards into a near-shore turbulent zone and a reef-like build-up and thence into an offshore shallow shelf. Foraminiferal faunal dating of the limestone indicates an uppermost Viséan, V3c age (Jameson, 1987) and confirms the Brigantian age assigned to the Lower Limestone Formation.

The exceptional development of limestone at Petershill is probably related to a volcanic rise on which limestone could accumulate without being swamped by clastic sediment.

The Petershill Limestone must also have been deposited in a period relatively free from volcanic eruptions and in a moderately humid tropical environment (Parnell, 1988). The Petershill Limestone is considered to represent a combined Main and Mid Hosie limestone over the volcanic rise (Smith et al., 1994), which is likely since these limestones are only 4 to 9 m apart in the Bo'ness area to the north and are also known to coalesce farther west near East Kilbride (Whyte, 1981).

The marine bioclastic limestone exposed at Wairdlaw [NS 994 731] appears to be isolated within the Bathgate Hills Volcanic Formation. It also appears to lie at a higher stratigraphical horizon than the Petershill Limestone, although its faunal assemblage is similar to that at Petershill. It is possible, therefore, to correlate the Wairdlaw Limestone with the Second or Top Hosie limestones or more likely a combination of both since the volcanic rise continued to develop into Limestone Coal Formation times. The Top and Second Hosie limestones cannot always be separated from each other in Strathclyde (Whyte, 1981). Around Bo'ness the Top Hosie is 0.35 to 1.73 m thick and the Second Hosie is 0.85 to 1.3 m thick whereas at Wairdlaw, the limestones with coral colonies and interbedded mudstones are 4 m thick, overlain by mudstones containing Calamites, Productus and scales of Palaeoniscus. The input of mud containing Calamites suggests the influence of nearby vegetated land (Cadell, 1925).

Chapter 3 Namurian

Namurian rocks underlie the greater part of the Falkirk district and are absent only in a narrow north-south zone on the eastern edge of the district. They are disposed in a broad synclinal structure with a north-south axis, and are at outcrop in the north-west, and in a north-south strip, 3 to 6 km wide, in the eastern part of the district.

Three formations forming part of the Clackmannan Group are included in the Namurian: the Limestone Coal Formation, the Upper Limestone Formation and the Passage Formation. The rocks are predominantly grey mudstones, silty mudstones, and pale grey or yellow sandstones with important but subsidiary seams of coal, ironstone, limestone and fireclay. Coal seams characterise the Limestone Coal Formation, limestones are prominent in the Upper Limestone Formation and fireclay is an important constituent of the predominantly arenaceous Passage Formation.

The base of the Namurian is not coincident with the base of the Limestone Coal Formation but has been shown to occur just below the Top Hosie Limestone at the top of the Lower Limestone Formation (Currie, 1954). The relationship of the lithostratigraphical to the chronostratigraphical divisions is shown in (Table 2). Radiometric dating gives an age range of 326 to 315 Ma for the Namurian (Leeder, 1988).

During the Namurian the Midland Valley of Scotland lay in equatorial latitudes, south-east of the North American-Scottish-Scandinavian Caledonides (Smith et al., 1981). Sediment derived mainly from the north was deposited by alluvial and deltaic processes in an extensive low-lying area subject to periodic marine transgression. Deposition was significantly influenced by differential subsidence and contemporaneous volcanism.

Limestone Coal Formation

The Limestone Coal Formation, formerly Limestone Coal Group, occurs at outcrop only in a narrow north-south strip in the eastern part of the district and in a small area in the north-west corner (Figure 9). The eastern outcrop extends from Bo'ness on the Firth of Forth southwards through Bathgate and beyond to the southern edge of the district. The strata dip towards the west and are concealed beneath the younger rocks of the Central Coalfield.

In part of the outcrop between Linlithgow and Bathgate the strata have been replaced by rocks of the Bathgate Hills Volcanic Formation.

The Limestone Coal Formation and the Lower and Middle Coal Measures are the main coal-bearing sequences in the Central Coalfield. Coal and ironstone were formerly worked underground in the Limestone Coal Formation in the eastern limb of the syncline and on the western limb in the north of the district. Coal mining in this part of the succession has now ceased.

The rocks are very poorly exposed and most of the information available comes from borehole and mining records. Since this information relates mainly to the extraction of coal, ironstone and fireclay, relatively little is known about that part of the formation which occurs below the principal coal-bearing horizons.

The lack of information on the thickness of the formation as a whole makes it impractical to map out thickness variations except in general terms. Broadly the formation is thinnest around the Salsburgh area in the south-west of the district where it is about 110 m thick. The thickness gradually increases NNE to about 200 m in the Falkirk area. North of Falkirk the thickness increases more rapidly to about 350 m in the Kincardine area, just outwith the district to the north, and to about 400 m under the Forth SSW of Culross. An isopachyte map for part of the formation in the northern part of the area is given in Francis et al. (1970, p.185) and generalised isopachytes for the upper part of the formation are given in (Figure 9).

The strata of the Limestone Coal Formation record a change in the type of sedimentation from the deltaic conditions with shallow-marine carbonates of the underlying Lower Limestone Formation to fluviodeltaic deposits with coal seams which characterise the Limestone Coal Formation. The strata consist for the most part of a succession of upward-coarsening cycles interupted in places by upward-fining sandstones. There are two main marine incursions which form a framework enabling the more detailed correlation between sequences. The Johnstone Shell Bed and the Black Metals Marine Band are about one third and half way up from the base respectively. In addition there are marine mudstones at the base of the formation, overlying the Lower Limestone Formation and at the top below the Index Limestone.

The complex interaction of the various factors which controlled sedimentation, at least in the northern part of the district, has been discussed by Read and Forsyth (1989) and Read (1994). Sediment from the Highland source area was transported by large river systems from the north-east and north-west into an area of differential subsidence. Superimposed on the range of sedimentary cycles inherent in fluvial and deltaic sedimentation were cyclical movements of sea level with at least two periodicities. Contemporaneously in the eastern part of the district rocks of the Bathgate Hills Volcanic Formation were formed and replaced or interdigitated with the sedimentary strata.

Classification

The Limestone Coal Formation is the oldest of the three subdivisions of the Clackmannan Group and it includes the strata stratigraphically above the Top Hosie Limestone at the top of the Lower Limestone Formation up to the base of the Index Limestone which is the lower boundary of the Upper Limestone Formation. The strata fall within the lower part of the Pendleian Stage (E1a) of the Namurian Series and within the NC Miospore Zone.

Lithology

The strata consist of a sequence of sedimentary cycles made up of clastic rock types arranged in upward-coarsening succession from a mudstone at the base through siltstone to sandstone, and with a palaeosol and coal seam at the top in the complete cycles. After deposition of the coal the surface was flooded and the cycle of deposition was renewed. In many instances the cycles are incomplete with one or more of the component lithologies absent.

The mudstones at the base of the cycle may include Lingula or non-marine bivalves and they tend to become silty and finely micaceous upwards. The silty mudstone passes up into sandstone, very commonly with an intervening sequence of silty mudstone with siltstone laminae and thin beds of fine sandstone. The sandstones are fine to medium grained, pale grey or buff coloured, with ripple lamination or cross stratification. Fossil plant material is common in most rock types.

In some cases the sandstone is overlain by a bed of upward-fining sandstone with an abrupt erosive base. Read and Forsyth (1989) interpreted this upper sandstone as fluvial rather than deltaic. In their investigation of the upper part of the Limestone Coal Formation between Glasgow and Stirling, Read and Forsyth (1989) made a distinction between a distal and a proximal facies association. The former is characterised by the lateral persistence of the lithological components of the cycle and by a relatively strong marine influence. In the latter facies there are rapid lateral changes in the strata and the fluvial influence is stronger. In the distal facies coals tend to be laterally persistent and rarely more than a metre thick, but in the proximal facies coals tend to be less consistent and coals which are thick in one section may tend to be split by clastic wedges when traced laterally. The two facies are end members of a series which tend to grade into one another both vertically and horizontally.

In the Falkirk district the two end members of the series can only be recognised in parts of some sections. In most areas both associations appear to be present.

Strata with a marine fauna occur at the base and top of the formation, and also in the Johnstone Shell Bed and the Black Metals. The fossiliferous rock is dark grey calcareous shale usually with thin clayband ironstone beds and nodules. The Black Metals is an unusually thick and persistent bed of dark grey shale which includes beds with a marine fauna. In places the shale is bituminous and clayband ironstone is common. Towards the northeast of the district, siltstone and sandstone are interbedded with the shale (Read, 1965).

Volcanic rocks

Volcanic activity coeval with the deposition of the Limestone Coal Formation is evident in the succession in the eastern part of the district (Figure 9). In parts of the outcrop between Bathgate and Linlithgow the entire formation is replaced by the Bathgate Hills Volcanic Formation, and volcanic rocks replace part of the formation from Armadale to north of Bo'ness. The extent of the volcanic rocks to the west is obscured by the cover of younger rocks, but lavas have been recorded in bores 2 to 3 km west of Armadale and in bores at Grangemouth. However, no volcanic rocks at this level were found in boreholes at Forrestfield [NS 860 670] and Rashiehill [NS 839 730] on the west side of the Falkirk-Stane Syncline.

Stratigraphy

In the north-western part of the district the Stirling Coalfield nomenclature is used for the seam names; in the north-east around Grangemouth and Bo'ness where the succession is similar to that in West Fife, West Fife names are used along with some names local to the Bo'ness area. In the south, where there are fewer coals, Lanarkshire names are used (Figure 10).

Much detailed stratigraphical information about the formation is contained in accounts by Hinxman et al. (1917, pp.6–19), Macgregor and Anderson, (1923, pp.24- 29, 35–42), Macgregor and Haldane (1933, pp.36–55) and Read (1959), and in a number of Technical Reports.

Base of formation to Johnstone Shell Bed

There are very few sections through this interval. In the south-west of the district this part of the formation is about 40 m thick at Forrestfield and about 50 m at Rashiehill. At the base of the formation there is a calcareous shale about 3 m thick with a marine fauna. The other strata below the Shell Bed are predominantly arenaceous with a few very thin coals.

In the south-east the strata are about 38 m thick. The marine shale at the base is about 1.5 m thick. The strata above consist mainly of sandstone, including both massive sandstone and thinly bedded sandstone with mudstone. There are a few thin seatbeds and some very thin coals.

In the north-east there are about 60 m of strata in this part of the formation. The marine mudstone at the base of the formation is about 6 m thick. Above this the depositional cycles are 6 to 8 m thick with Lingula sp. and non-marine bivalves in the mudstones at the base of each cycle. Coals, 0.5 to 0.9 m thick, are present in the upper half of the interval including the Smithy Coal, which was formerly worked extensively in the Bo'ness area.

Johnstone Shell Bed

The Johnstone Shell Bed is a widespread marine horizon that has been recognised wherever there is a section through that part of the sequence. It represents a significant marine incursion, probably resulting from a eustatic rise in sea level. In the southern part of the district the shell bed is 1 to 2 m thick and consists of mudstone and calcareous shale with thin beds and nodules of clayband ironstone. It also contains a thin impure shelly limestone known as the Slingstane Limestone. In the north-east the shell bed is split into an upper and lower marine shale with about 16 m of mainly sandy strata intervening. Thin mudstone beds with Lingula and bivalves, and thin clay-band ironstone beds are also present. In the north-west the shell bed is reduced to about 0.4 m of mudstone with a marine fauna.

Johnstone Shell Bed to Black Metals

The interval between the top of the Johnstone Shell Bed and the base of the Black Metals is thickest in the northeast of the district where there are up to 100 m of strata. The succession shows considerable variation laterally. Several coals are present, and two have been worked, but they are not notably persistent laterally. The thickest is the Cowdenbeath Five Foot (about 1.58 m). Thick beds of sandstone have eroded the underlying strata and have removed much of the coal in places. The thickness of the sedimentary cycles also varies from about 4 up to 9 m. Volcanic rocks from the Bathgate Hills Volcanic Formation occur in some borehole sections.

In the north-west the interval thins to about 55 m. The succession in this area is predominantly arenaceous and there are thick coarse sandstones with erosive bases in the upper part. The Lower Knott Coal is the only named seam, but it has not been worked in the district.

At Rashiehill, the strata are 50 m thick and the succession includes the Kilsyth Coking Coal and the Garibaldi Coal. The former is the thicker at 0.7 m but they are too deeply buried to have been a workable prospect.

Farther east in the Whitrigg area [NS 967 646] the interval is 60 to 65 m and erosive fluvial sandstones, particularly in the upper half of the interval, have disrupted the fluviodeltaic cycles. The coals have the east Lanarkshire names and the best-developed seams are the Wilsontown Gas and the Haywood Under.

Black Metals

The Black Metals is an unusually thick and persistent bed or set of beds of dark grey mudstone with a fauna which at one or two levels is marine. It can readily be recognised throughout the district in sections through that part of the succession. A detailed study of the Black Metals has been carried out by Read (1965) in an area east of Stirling which included the northern edge of the Falkirk district.

In the southern part of the district the Black Metals normally are 8 to 10 m thick and consist of dark grey shale, bituminous in parts with thin beds and nodules of clayband ironstone. Marine fossils are usually found in the lower part and Lingula and Naiadites are normally fairly common throughout. Fossil plant matter is also present. In the south-east at Whitrigg, the Black Metals are overlain by a coarse erosive sandstone and the thickness of shale is reduced to about 5 m.

In the northern part of the district the lateral changes in the Black Metals have been described by Read (1965). In the north-west, the strata consist of up to 19 m of dark grey shale with thin ironstones but, in the north-east, the equivalent strata are thicker and become sandy with thin coals and seatearths. At Grangemouth the thickness is about 35 m and under the Forth SSW of Culross the equivalent beds are 85 m thick. Read attributed the abrupt increase in thickness to the interaction of a major marine transgression with local processes of rapid subsidence and sedimentation.

Black Metals to base of Index Limestone

The upper part of the Limestone Coal Formation includes most of the coals which have been of economic importance and consequently there are numerous borehole sections through all or most of this part of the sequence. Detailed information is given in accounts by Hinxman et al. (1917, pp.6–19), Macgregor and Anderson, (1923, pp.24–29, 35–42, Macgregor and Haldane (1933, pp.36- 55) ) and Read (1959) and also in Technical Reports by Forsyth (1988a-b, 1990a-d) and Cameron and Chisholm (1988; 1990).

The thickness variations for this part of the formation follow the same pattern as that in the underlying beds. There is little significant difference in thickness across the southern part of the district but there is abrupt thickening in the north-east (Figure 10). Read and Forsyth (1989) and Read (1994) have given an account of the type of sedimentation and the controls on sedimentation which operated during deposition of this part of the formation in the Glasgow-Stirling area which includes the northernmost part of the Falkirk district.

In the south-west the strata are 75 to 90 m thick and include several thin unworked coal seams and seatbeds. The coals in some sections can be tentatively correlated with seams farther to the east, but the proportion of sandstone in the sequence varies substantially making correlation uncertain and indicating a considerable fluvial influence on the sedimentation. The only fossil horizon known in this part of the sequence is a Lingula band and it is assumed to be equivalent to the Lingula band above the China Coal in the southern and south-eastern parts of the district.

The strata in the south-east are of a similar thickness (c. 90–100 m), but several of the coal seams are thicker and more persistent. Five seams were formerly worked. Sandstone is the predominant lithology with coarse erosive sandstones at some levels. Lateral variation is less evident than farther west and local correlation is more certain. The Wilsontown Main, Bathgate Jewel, Woodmuir Smithy, China and Balbardie Gas coals were the most widely worked seams in the area.

In the north-west the strata are thicker (150–180 m) and the coals are more numerous. Most are thin, but four seams, the Bannockburn Main, Hartley, Greenyards and Knott coals were worked fairly extensively. The Bannockburn Main Coal was one of the most valuable in the Limestone Coal Formation. Read (1961) has described the variations in the Bannockburn Main Coal and laterally equivalent strata in relation to the overall variations in thickness of the Limestone Coal Formation as a whole in the Stirling-Denny-Bo'ness area. The Torwood area [NS 84 85] in the north-west of the district is intermediate in sedimentological aspect between the Kilsyth Trough to the west, which was less subject to fluvial influences, and the Kincardine Basin to the east, which was acting as a trap for the more proximal, fluvially influenced facies association. Marine fossils are not present except immediately below the Index Limestone, but Lingula occurs sporadically at a few horizons. The most persistent is the Sub-Hartley Lingula Band a few metres below the Hartley Coal. Lingula also occurs locally in mudstone overlying the Berryhills Limestone. The latter is nonmarine and occurs in many sections in this part of the sequence (Read, 1959; Francis et al., 1970). It is an impure, grey coloured rock, containing ostracods in places, and is up to 0.3 m thick.

The strata above the Black Metals thicken abruptly in the north-east of the district. Under the Forth SSW of Culross they are over 250 m thick, and at Grangemouth they are about 230 m thick. The increase in thickness was considered by Read (1965) to be due to relatively rapid subsidence acting as a trap for sediment transported by major river channels from the north-east. The strata include numerous coals, many of which are thin, but about twelve coals have been worked in the past and of these at least eight were wrought over a considerable area. In addition ironstone at two levels was worked on the south side of the Forth. The extent of mining was restricted in the south where the coal-bearing strata give way to volcanic rocks between Bo'ness and Linlithgow. Thick sandstones are also present, particularly in the lower half of the interval. They are coarse, feldspathic, upward-fining channel sandstones and contain in the basal part mudstone and siltstone intraclasts. Strata with a fully marine fauna are not present except immediately below the Index Limestone, but beds of shale with Lingula occur at several horizons.

Variation in the development of the Bannockburn Main Coal illustrates the proximal and distal facies associations described by Read and Forsyth (1989). In the north-west of the district, where the distal facies association prevails, the Bannockburn Main Coal is a composite seam, or is split into two seams. At Torwood there is over 2 m of coal in two seams and other thin leaves in a total of about 2.9 m of strata. The equivalent beds in the Kincardine Basin, in the proximal facies association, are about 36 m thick, consisting mainly of sandstone and including several coals.

Upper Limestone Formation

The Upper Limestone Formation, formerly the Upper Limestone Group, crops out mainly in the eastern part of the district between Bo'ness and Breich. In the northwest around Denny, it is also brought to the surface by the effects of the Banknock Fault (Figure 11). At depth under the greater part of the district, it has been proved by numerous boreholes, many of which penetrate the full thickness of the formation. Conjectural isopachytes are given in (Figure 11). The greatest thickness in the Clackmannan Basin is 502 m recorded from the Westfield Borehole [NS 8834 8706] (Figure 12) about 1 km north into the Alloa district (Sheet 39E). Just to the south of this, on the northern margin of the district, the thickness is reduced to 435 m in the Mossneuk Borehole [NS 8723 8609] (Figure 12). Near the southern margin of the district, the formation is typically about 190 m thick as in the Levenseat Borehole [NS 9423 5960]. In all three boreholes, the Castlecary Limestone is present at the top of the formation. In the Forrestfield Borehole [NS 8604 6707], where the Castlecary Limestone is missing due to erosion, the formation could be as little as 151 m thick. However, there is doubt about which sandstone marks the erosive base of the overlying Passage Formation in this borehole. The Upper Hirst Coal is still being mined (1998) at the Longannet Mines Complex, but there are no active workings within the Falkirk district. This seam ranges from 320 to 106 m above the Index Limestone, and 222 to 44 m below the top of the Castlecary Limestone (or erosive channel sandstone base).

Classification

The rocks of the Upper Limestone Formation form the middle of the three Clackmannan Group units within the Namurian Series. They are assigned on palaeontological grounds to the late Pendleian (El ) and Arnsbergian (E2) stages. The Castlecary Limestone at the top of the Formation lies just below the top of the Arnsbergian Stage. The formation includes the upper part of the NC and the whole of the TR miospore zones (Chapter 5).

The base of the formation is defined at the floor of the Index Limestone. The base of the overlying Passage Formation is the roof of the Castlecary Limestone. However, in much of this district, this limestone is missing because of its removal by penecontemporaneous erosion by incising river channels. For this reason, the top of the formation has often to be placed at a suitable, but perhaps arbitrary, erosive channel sandstone base.

Lithology

This formation is characterised by rhythmic repeated upward-coarsening sequences of black to grey, sometimes calcareous, mudstones overlain by siltstones and sandstones capped by seatrocks and coal. The mudstones commonly include thin limestones. The sandstones are generally off-white and fine to medium grained. The coals are usually less than 0.6 m thick.

Minor lithologies present include ironstones and cannel. Upward-fining sequences of coarse- to fine-grained sandstones passing up into finer-grained rocks are also present. The formation is predominantly of shallow-water marine shelf and deltaic origin but also in part of lacustrine origin. The presence of paleosols, including coals, show that subaerial delta top and lower alluvial plain environments existed. However, the heavily bioturbated striped beds (usually thinly interbedded siltstone and sandstone) indicate that delta lobe abandonment was a common event with subsequent marine reworking of the delta top. The existence of alluvial plain environments is also confirmed by the presence of the upward-fining channel sandstone bodies. These are particularly well developed where associated with penecontemporaneous faulting within the sedimentary basin causing significant intraformational unconformities, such as that which cuts out the Castlecary Limestone.

Stratigraphy

Nine marine limestones of varying thickness and persistence provide the primary basis of correlation (Figure 12). Four of these, the Index, Orchard, Calmy and Castlecary limestones are in general relatively thick and persist over a wide area of the Midland 'Valley. The other five, namely the Huntershill Cement, Lyoncross, and Plean Nos. 1, 2 and 3 limestones are generally thinner and less persistent. With the exception of the Castlecary, all the limestones are overlain by mudstones containing a varied marine fauna. In addition to the named beds, there are more than 20 other marine and Lingula bands. Faunal variations are such that there are more marine bands in the centre of the sedimentary basin (northern end of the district), but fewer marine and more Lingula bands towards the south.

Volcanic rocks such as beds of waterlain tuff and tuffaceous siltstone occur at several levels in the formation. These beds are usually thin but exceptionally may be 3 m to 60 m thick. Lava flows also occur and replace most of the sedimentary succession up to the floor of the Calmy Limestone cycle in some parts of the district as in the Redding Diamond [NS 9158 7759] and Couston [NS 9464 7145] boreholes (Figure 12). Locally, as in the Easter Jaw Borehole [NS 8718 7451], volcanic rocks replace much of the interval between the roof of the Calmy Limestone cycle and the floor of the Castlecary Limestone. The volcanic rocks are described in the chapter on the Bathgate Hills Volcanic Formation.

Index Limestone to Lyoncross Limestone

This interval ranges from 182 m in the north to 44 m in the south. The Index Limestone usually occurs in the lower part of a thick bed of mudstone. It ranges in thickness from 0.58 m to 2.21 m and only rarely is in leaves. It is grey in colour, muddy and may also be shelly and crinoidal. The succession above the Index Limestone is variable with one or two thicker sandstones, a bed of limestone and many thin coal seams. Apart from the impersistent Huntershill Cement Limestone, there are up to six marine or Lingula bands, as many as four non-marine musselbeds, and beds with ostracods. The numbers of minor cycles recognised in the interval varies from one or two in the south to 18 m the north. Most of these cycles are underlain by a thin coal seam; 14 seams is the maximum number recorded down to none in the south of the district.

The marine Huntershill Cement Limestone lies some 12 m to 33 m above the Index Limestone and may be separated from it by strata including the Bishopbriggs Sandstone and by rather persistent lava flows up to 40 m thick. The Huntershill Cement Limestone is never more than 0.4 m thick and is commonly represented by shelly mudstone. In places it is missing due to erosion. Some distance above this limestone is the thick Cadgers Loan Sandstone which is generally coarser than other beds of sandstone and is usually pebbly. It is a multistory channel sandstone body.

Lyoncross Limestone to Orchard Limestone

This interval ranges from 90 m in the north to 18 m in the south. The Lyoncross Limestone is a hard, fine-grained, grey limestone that contains crinoidal debris and shells but it is not everywhere developed. Sometimes even the associated marine mudstones are missing or have not been recognised. The succession above the Lyoncross Limestone consists of one to 13 or more minor cycles with up to four marine or Lingula bands, and at least one nonmarine mussel bed. Some of the cycles are underlain by a thin coal seam. In the south there are usually one to four, and in the north seven to 13 seams. Only locally is there development of coarser sandstone.

Orchard Limestone to Calmy Limestone

This interval ranges from 108m in the north to 40 m in the south. The Orchard Limestone is a hard, fine-grained, grey limestone that is crinoidal and sometimes shelly. It is usually found near the base of a thick mudstone. Although it is up to 0.75 m thick, the limestone is not always developed and is usually under 0.3 m in thickness. The lower part of this interval, above the mudstone, usually contains a thick development of sandstone forming the upper part of the upward-coarsening Orchard Limestone cycle. In the Plean area of the Alloa district, this sandy unit is called the Cowie Rock. In the upper part, there are one to three marine bands and one or two Lingula bands. The two most persistent marine beds form the Glenboig Marine Band. This band is known to occur under the northern third of the district, but is also known from two boreholes in the south. In places some of the marine bands are replaced by nonmarine musselbeds. More than eight thin cycles are developed in the upper part of this interval but, although as many as eight thin coal seams are known below the Upper Hirst Coal, usually there are only one to four. The Upper Hirst Coal is 1 to 7 m below the Calmy Limestone. It varies in thickness from 0 to 2.45 m in one to three and rarely up to six leaves. It is a high ash scam that has been mined at the Longannet Mines Complex for fuelling the power station.

Calmy Limestone to Castlecary Limestone

This interval ranges from 220 m in the north to 75 m in the south. However, the Castlecary Limestone is usually absent because of erosion south of Falkirk, and the minimum thickness is reduced to 44 m where this named horizon is missing. The Calmy Limestone is usually in two to four leaves and is found towards the base of a thick bed of mudstone. It varies in thickness from 0.50 to 4.56 m, but is usually 1.3 to 2.0 m. The limestone is typically fine grained, pale grey or grey, and may contain shells and sometimes crinoid debris. The Plean No. 1 Limestone and Coal is 23 to 97 m above the Calmy Limestone.

In the upper part of this interval there are up to five marine or Lingula bands in the north diminishing to none in the south. The Plean No. 1 Limestone is the lowest of these marine beds. This limestone and associated mudstones are commonly hard to recognise or are undeveloped in the south but the carbonate bed is up to 0.65 m thick in the north. The underlying coal is impersistent but is up to 1.77 m thick in the Letham area.

Between the Plean No. 1 Limestone and the Castlecary Limestone (or eroded base to the Passage Formation) are the Plean No. 2 and No. 3 limestones with their associated mudstone and underlying coal. Both these horizons are much affected by contemporaneous erosion and the No. 3 Limestone is normally absent in the district. The No. 2 Limestone is more persistent in development and the associated mudstone more readily identified than either of the other two limestones, especially in the south of the district. However, in the interval between the Plean No. 1 and No. 2 limestones which varies in thickness from 14 to 69 m, there are from one to over ten minor cycles, with as many as five marine or Lingula bands developed in the north but not present farther south.

The Plean No. 2 Limestone and the underlying coal are each up to 0.55 m thick in the north but an average thickness is less than 0.3 m. The cycle above is the Plean No. 3 Limestone and this bed and the associated coal seam are never more than 0.3 m thick. The interval between the bases of these two marine bands ranges from 8 to 17 m. The interval between Plean No. 2 Limestone and the Castlecary Limestone is as much as 45 to 50 m in the north, with three to six minor cycles recognised and including one at a horizon where Lingula was previously unknown (Francis et al., 1970, p.201). The interval thicknesses diminish southwards and are further reduced by erosion such that the base of the Passage Formation is at the level of the Plean No. 2 horizon.

Over much of the district the Castlecary Limestone has been removed by penecontemporaneous erosion. In the north, the sporadic pattern of absence appears to reflect the erosive incision of a meandering river channel in which coarse sandstone was laid down at the base of the Passage Formation. The uneroded thickness of the Castlecary Limestone ranges from 1.6 to 3.3 m in the north but where it is preserved in the south, as at Leven Seat [NS 9423 5960], the limestone is 2.5 m thick. The limestone may be dolomitic and dark to pale grey in colour. The grain size is also variable. Shells and crinoidal debris are scattered throughout the limestone. In boreholes in the Whitrigg area [NS 96 64], the Castlecary Limestone is only 0.6 m thick because of erosion; it is rooty and shows concretionary pedogenic nodular features with cream and green secondary clay patches in between.

Passage Formation

The Passage Formation, formerly Passage Group, forms north-south outcrops on either side of the district (Figure 13). In the east the outcrop extends from Longannet [NS 95 85] and Grangemouth in the north to Fauldhouse and Leven Seat in the south. The western outcrop underlies Larbert and Bonnybridge in the north and emerges in the core of the Salsburgh anticline in the south-west of the district. The outcrop also extends from the main eastern outcrop westwards where it has been brought to the surface by the Mungal Fault, north of Falkirk, and similarly by the Lenzie-Torphichen Fault in the Avonbridge area.

The Passage Formation includes the strata overlying the Castlecary Limestone at the top of the Upper Limestone Formation and lying beneath the Lowstone Marine Band at the base of the Lower Coal Measures. Locally, marine horizons in the lower part of the formation and in the upper part of the Upper Limestone Formation have been removed by erosion and replaced by sandstone. In these circumstances locating the base of the Passage Formation is problematical.

The thickness of the formation ranges from about 350 m in the north of the district to about 100 m in places in the south-west (Figure 14). The strata tend to thicken gradually northwards and eastwards with an apparently more rapid thickening north of Falkirk. There is insufficient data to relate the changes in thickness to known faulting.

A period of uplift, erosion and regression in the early part of the Passage Formation brought about a change from the deltaic conditions with major marine incursions, which prevailed during the Upper Limestone Formation, to predominantly fluviatile deposition with an influx of coarse detritus from the north (Read, 1969; 1988). The relatively thick beds of limestone and marine shale which are characteristic of the underlying formation are much thinner in the lower part of the Passage Formation and are vestigial in the upper part. At the top of the formation fluvial sedimentation is replaced by the fluviodeltaic conditions of the overlying Coal Measures.

The rocks are not well exposed and information about the sequence comes mainly from borehole information. A good section in the lower part of the formation can be seen in Torwood Glen [NS 830 855] and parts of the sequence can also be seen in the gorge of the River Avon in the vicinity of the Birkhill Fireclay Mine [NS 965 789]. The mine is open to visitors (1995).

Classification

The strata range in age from the upper part of the Arnsbergian Stage of the Namurian into the Langsettian Stage of the Westphalian. Fossil evidence is virtually confined to a few marine horizons and miospores in the coal seams. The goniatites on which the Namurian classification is based are very poorly represented. The post-Arnsbergian stages are thin and incomplete and faunal or microfaunal evidence for the presence of the Chokierian and Alportian stages is lacking (Neves et al., 1965; Ramsbottom et al., 1978). The base of the Langsettian Stage of the Westphalian is believed to occur within the upper part of the Passage Formation. The relationship of the chronostratigraphical divisions to the lithostratigraphical formations is shown in (Table 2).

The presence of marine bands enables the stratigraphical correlation of one section with another. Originally the marine bands were numbered from 1 to 3 m ascending order but subsequently others were found and the numbering scheme had to be modified. The sequence includes Nos. 0, 1 and 2 marine bands and Nos. 3, 5 and 6 marine band groups. Up to 16 or 17 individual marine bands are known but many occur only locally.

Lithology

The formation consists principally of sandstones, mudstones, a few thin limestones and marine mudstones, thin coal seams and a few ironstones.

The lithology of the basal part of the formation resembles that of the Upper Limestone Formation. It includes up to three thin marine limestones or fossiliferous mudstones with sandstones and thick apparently unbedded mudstones. The upper part of the formation, however, is dominated by sandstones which are interbedded with poorly bedded mudstones. Coal seams, with one or two local exceptions, are thin and impersistent.

There are also some thin fossiliferous bedded mudstones which allow a degree of correlation between sections.

The sandstones of the Passage Formation have been described by Read (1969). They are white, pale grey or yellow in colour and tend to occur mainly in beds which are coarse grained at the base and become finer grained upwards. They are mainly subarkoses but quartz arenites and sublitharenites also occur.

The upward-fining sandstones may occur singly or as a series with the base of each resting on a scoured surface cut into the underlying beds. The coarser sandstone in the lower part of each unit may contain scattered small pebbles or angular clasts of siltstone or mudstone. Locally, fossilised drifted tree trunks occur in the basal parts of the thicker sandstone beds. The finer beds may be ripple laminated and include partings of siltstone and mudstone.

The single upward-fining sandstones are commonly less than 5 m thick. Thicker sandstones, formed from a series of upward-fining sandstone units, may be up to 24 m thick, but are usually less than 12 m. The thinner sandstones are considered to be simple channel fills and the thicker sandstones may represent the deposits of meander belts.

The petrography and provenance of the Passage Formation sandstones has been studied by Muir (1963). The sandstones were found to be mainly orthoquartzites (quartz arenites) and protoquartzites (sublitharenites) and a few subgreywackes (lithic arenites). From his study of the mineral assemblages Muir concluded that the sandstones were derived from a low-grade metamorphic source intruded by acid igneous masses comparable to the Upper Dalradian in its present outcrop. He also noted that the heavy mineral asssemblage in the Passage Formation was very different from that in both the Upper Limestone Formation and the Coal Measures.

A sandstone in the lower part of the formation at Leven Seat [NS 943 580] has been worked for many years as a silica sand and used for moulding sand and several other non-industrial uses ((Plate 8); Chapter 11).

The sandstones pass up by gradation into siltstone and mudstone. The argillaceous strata range in colour from dark grey or pale grey to mottled lilac, reddish brown and yellow. They are up to 19 m thick, but usually less than 10 m. Some mudstones are bedded, particularly the marine mudstones, but in many cases both the siltstone and mudstone show little sign of bedding. The original stratification is believed to have been obliterated by root systems and soil-forming processes. Rootlets can be seen in the darker beds but partial oxidation as a result of the lowering of the water table has removed carbon from the variegated, pale coloured rocks making rootlets less obvious. The mudstone is composed mainly of poorly crystallised kaolinite, hydrous mica and finely divided quartz, together with minor amounts of iron and carbonaceous matter (Wilson et al., 1972; Read and Dean, 1978).

The rocks are thought to be the overbank deposits of a large river system. Read (1969) and Wilson et al. (1972) suggested that the kaolinite may have been a product of tropical weathering. However, Morgan (in Read and Dean, 1978) noted that aluminium hydroxide minerals characteristic of bauxitic weathering had not been detected in these rocks.

The mudstones are economically the most important of the rock types in the Passage Formation. They include seams with the properties of fireclay which have been worked in several places, although the industry is almost dormant at the present time (Plate 9).

A thin bed of tuffaceous siltstone close above the Castlecary Limestone has been recorded in a borehole to the north-west of Torphichen [NS 967 723]. This is believed to be the highest stratigraphical level at which the Bathgate Hills Volcanic Formation occurs.

Unconformities

Many of the sandstone units in the succession rest on scoured surfaces eroded into the underlying beds. This results in the absence in places of one or more of the marine horizons which are the means of correlating one section with another. In the lower part of the formation there are three widespread marine horizons, No. 0, No. 1 and No. 2 marine bands, but any one, two or all of these may be absent due to erosion by overlying sandstones. The same is true for less persistent beds of ironstone and fireclay. In places also the Castlecary Limestone and underlying strata of the Upper Limestone Formation have been eroded down to a stratigraphical level just above the Plean No. 1 Limestone. Many of these unconformities appear to be of local significance only.

Read (1981) identified three depositional breaks or facies changes in the Passage Formation which he thought sufficiently important to be considered as the local expression of the Mississippian-Pennsylvanian erosional break in North America. The lowest of these breaks, which is at the base of the formation, immediately above the Castlecary Limestone, caused deep channelling into Upper Limestone Formation strata. The second is positioned immediately overlying the No. 2 Marine Band, and the third overlies the No. 3 Marine Band group. Read considered that the biostratigraphical evidence favoured the unconformity overlying the No. 2 Marine Band as the most likely equivalent of the North American hiatus, although the unconformity at the base is a more striking example of regression.

Stratigraphy

The lower part of the formation includes the No. 0, No. 1 and No. 2 marine bands which may include thin fossiliferous limestones. The thickness of this part of the formation ranges from about 9 m up to 40 m. The strata tend to bethinner in the southern part of the district and in the north-west with the greatest thickness in the Grangemouth area. Ina borehole at Kincardine Bridge, just outwith the district to the north, a thickness of 58 m was recorded between the No. 2 Marine Band and the base of the sandstone assumed to mark the lower limit of the formation in the absence of the Castlecary Limestone.

At the base of the formation, immediately overlying the Castlecary Limestone there is a thin bed of carbonaceous mudstone which includes fish remains. However, in many instances the mudstone has been removedand replaced by the overlying sandstone.

The No. 0 Marine Band consists of fossiliferous marine shale up to about 3.5 m thick and commonly includes a thin earthy limestone. In places the bed consists solely of a thin limestone and in several localities it is entirely replaced by an erosive sandstone.

No. 1 Marine Band in its best development consists of up to 3 m of fossiliferous marine shale including a thin bed of earthy limestone up to 1 m thick. In many cases, however, it is not present or is reduced to a thin bed of limestone or mudstone with a marine fauna.

No. 2 Marine Band tends to be the most persistent of the marine horizons in the Passage Formation, although it also is liable to have been eroded and replaced by sandstone. It most often consists of a marine shale with a thin limestone up to 1 m thick. The limestone is known as the Roman Cement Limestone and, in places, it is characterised by the presence of abundant ribbed brachiopod shells (orthotetids).

The interval between No. 2 Marine Band and the Netherwood Coal, which is within the No. 3 Marine Band group, varies from about 10 m in the south-west to about 55 m north of Grangemouth. This part of the sequence has been studied by Read and Dean (1982) using statistical techniques to draw inferences about the relationship between basin subsidence, lithological composition and numbers of fluvial cycles. The study showed that the numbers of rooty horizons and fluvial cycles, together with total thicknesses of sandstone and of mudstone + siltstone, all show a statistically significant linear relationship with the total thickness of strata and therefore with net subsidence. The rocks consist of sandstone with beds of mudstone and fireclay. The fireclays have been worked at various localities and are collectively known as the Lower Fireclays. They are overlain by the Leven Seat Sandstone (Plate 8) which is about 12 m thick. There is also a clayband ironstone, known as the Curdly Ironstone, close above the No. 2 Marine Band, which was formerly worked in the south of the district.

The No. 3 Marine Band group consists of three thin beds of fossiliferous shale in up to 22 m of strata, but rarely are all three present in a single section. Overall the group is fairly persistent, although individual fossiliferous horizons are less so. The Netherwood Coal occurs within the group. It is normally a thin seam commonly split by several thin partings of seatclay. Nowhere in the district does it attain a workable thickness. Where three marine bands are present the coal underlies the second lowest. The lowest marine band in the group is commonly not present.

The interval between the Netherwood Coal and the lowest marine bed in the No. 5 Marine Band group ranges from about 8 m in the south-west to 53 m in the Grangemouth area. It consists mainly of sandstone with rooty beds. Rarely there is a thin coal and clayband ironstone.

The No. 5 Marine Band group usually consists of up to three marine mudstone horizons within about 16 m of mainly arenaceous strata. One, two or all three beds may be missing. The fauna tends to be less abundant and less varied than most of the marine horizons lower down in the Passage Formation.

Between the top of No 5 Marine Band group and the base of No. 6 Marine Band group the strata consist mainly of sandstone and are up to 44 m thick.

No. 6 Marine Band group in the northern and eastern parts of the district includes up to three fossiliferous marine horizons in about 45 m of strata. In the south-west the marine bands have not been found or are reduced to a single Lingula band. A poor quality coal and the overlying Goodockhill Slatyband Ironstone occur at about the equivalent stratigraphical level. The ironstone is variably developed and was worked during the last century in the Kirk O' Shotts-Salsburgh area. The fossiliferous beds of No. 6 Marine Band group are less persistent laterally than most of the Passage Formation marine horizons and are separated one from another by a considerable thickness of strata. As a result they tend to be of limited use in correlating one section with another. It is believed that the base of the Westphalian occurs at or close above the No. 6 Marine Band group (Neves et al., 1965).

The strata above the No. 6 Marine Band group range in thickness from about 90 m in the north-east of the district to about 36 m in the south and south-west. In the north-east the strata are almost exclusively arenaceous. The sandy facies extends up into the Lower Coal Measures so that the location of the boundary between the two formations is arbitrary. Coals are present but for the most part are very thin and impersistent. The Bowhousebog Coal, which has spores of Westphalian age (Neves et al., 1965), is the most persistent; it is up to 1 m thick locally, but it tends to be sulphurous and of poor quality. It has only been worked in a small way, usually with fireclay. The Glen Coal occurs near the top of the formation. It has been worked around Armadale and its lateral equivalent, the Crofthead Slatyband Ironstone was worked extensively during the last century around Fauldhouse and towards Harthill. The Upper Fireclays occur around the position of the Bowhousebog Coal and have been worked particularly in the Bonnybridge area (Plate 9) and around Whitburn. Fireclay also occurs a little higher in the succession at the level of the Glen Coal.

The top of the formation is placed at the base of the Lowstone Marine Band. Where the marine band does not occur the base of the Lowstone (Armadale Stinking) Coal, or an equivalent position, is used.

Chapter 4 Westphalian

Coal Measures

Two of the three formations which are of Westphalian age in Scotland are present in the Falkirk district, with the Lower Coal Measures occupying by far the largest area. Relatively small outliers of Middle Coal Measures occur zmainly in the southern half of the district with a small faulted outlier in the north (Figure 15).

The lower boundaries of the Westphalian and the Lower Coal Measures are not coincident. The Subcrenatum Marine Band which marks the base of the Westphalian has not been found in Scotland, but evidence from miospores (Neves et al., 1965) has shown that the base occurs at an undefined position in the upper part of the Passage Formation (Chapter 3). The base of the Lower Coal Measures is placed at the Lowstone Marine Band or at a position thought to be equivalent. The marine band is a locally convenient marker horizon, recognisable throughout most of the district, which lies some way above the base of the Langsettian Stage of the Westphalian. The relationship between the lithostratigraphical and chronostratigraphical divisions is shown on (Figure 16). This figure also shows the zonation based on nonmarine bivalves. The Passage Formation, although partly of Westphalian age, is described in the preceding Namurian chapter. Radiometric dating indicates that the lower part of the Westphalian was deposited between 315 and 311 Ma (Leeder, 1988).

The Coal Measures are subdivided into three formations: Lower, Middle and Upper Coal Measures. The outcrop of the Lower Coal Measures in the Falkirk district occupies approximately half of the area of the map but the Middle Coal Measures outcrop is restricted to a number of small mostly faulted outliers. The Upper Coal Measures are not present in the district. The strata form a broad open synclinal structure orientated north-south. The outcrop is limited to the east by steeper dips which bring older rocks to the surface in a zone down the east side of the district. Similarly in the north-west older rocks at surface dip eastwards below the Coal Measures outcrop. Included in the sequence are numerous seams of coal of which more than 12 were formerly mined underground. There are also areas where thin seams of ironstone were extracted. At present (1995) all mining in the Coal Measures is carried out using opencast methods (Plate 10), (Plate 11).

The boundary between the Lower and Middle Coal Measures is taken at the base of the Vanderbeckei (Queenslie) Marine Band which also marks the base of the Duckmantian Stage of the Westphalian (Figure 16). The marine band or its position in the sequence can normally be recognised in the district; it is a widespread horizon throughout western Europe.

The principal structures affecting the Coal Measures strata are the Clackmannan Syncline in the north and the Falkirk-Stage Syncline in the south. The outcrop is crossed by numerous east-west faults, with two important faults subdividing the district into three parts. North of the Banknock Fault is the southern part of the Kincardine Basin (Francis et al., 1970). Between this and the Slamannan Fault, which crosses the centre of the district, is the Falkirk-Slamannan area, the Harthill-Faulhouse-Shotts area lies south of the Slamannan Fault.

The general north-south strike and the predominance of east-west faults is replaced in the south-west corner where the north-west to south-east Salsburgh Anticline brings Passage Formation rocks to the surface flanked by Lower and Middle Coal Measures. The main faulting in the area also has a north-west to south-east orientation.

The thickness of the Lower Coal Measures ranges from 145 m to 207 m. The formation is thickest in the area to the south of Harthill and it thins to the west and to a lesser extent to the north. The maximum thickness noted in the Kincardine Basin in the Stirling district is 155 m (Francis et al., 1970).

The full thickness of the Middle Coal Measures does not occur in the district. The greatest residual thickness is about 90 m in the south-west.

The Coal Measures were deposited in a warm and humid climate and palaeomagnetic evidence indicates that, at that time, the area lay in equatorial latitudes. The strata are believed to have been deposited in delta-plain and alluvial-plain environments with drainage generally from a large continental area to the north. The sediments accumulated under conditions of continuous but non-uniform subsidence modified by eustatic changes in sea level. The conditions of deposition produced a degree of cyclicity in the sequence of strata. Periodic brief incursions by the sea left important marine horizons which are the basis of the subdivision of the succession. Volcanism which was an important feature of the Namurian had ceased before Westphalian sedimentation began.

The rocks are very poorly exposed with only scattered exposures and few sections. The succession is known principally from borehole records and mining information. Most of the records stem from the search for coal and ironstone and more recently from the need to investigate ground conditions prior to construction. Many of the early records lack sedimentological and palaeontological information. Much detailed information is contained in the Economic Memoirs describing the Central Coalfield (Hinxman et al., 1917; Macgregor and Haldane, 1933; Clough et al., 1916; Macgregor and Anderson, 1923).

Lithology

The strata consist of pale yellow, grey or brown sandstones, siltstones, mudstones and coal seams with seatbeds. They tend to occur in upward-coarsening cycles with mudstone at the base passing up through siltstone and sandstone to a root-bed underlying the coal seam. The cyclical sequence in many cases is incomplete with one or more of the component lithologies absent. Thin clayband ironstones or layers of nodules are common in the mudstone beds above the coal seams. Blackband and slatyband ironstones also occur. The cycles vary greatly in thickness from a few metres to over 30 m but the majority are between 8 and 12 m.

The upward-coarsening cycles are locally interupted by upward-fining sequences with medium to coarse sandstone in the lower part and a sharply defined or erosive base. In some cases they are overlain by another coarse-based sandstone but others pass up into a fine-grained scathed and coal seam. These rocks are interpreted as the deposits of river channels.

Marine fossils are restricted to three horizons but while marine forms do occur, in many instances the marine band is represented by a Lingula band and in bore sections the position of the bed may only be apparent from its position in the sequence of coals: The Lowstone Marine Band and the Vanderbeckei (Queenslie) Marine Band occur at the base of the Lower and Middle Coal Measures respectively and are found throughout the district. The third marine band, the Sub-Glenfuir, appears to be less widespread and does not seem to be present in the west of the district (Forsyth and Brand, 1986; Brand, 1977). Nonmarine bivalves occur at several horizons facilitating correlation between sections. The more important and persistent musselband horizons are the Auldshields Musselband which has a Lenisulcata Zone fauna, a musselband above the Upper Drumgray Coal in the Communis Zone and the Kiltongue Musselband in the lower Modiolaris Zone. Mussels also occur less abundantly above some of the other coals.

Lower Coal Measures

North of Banknock Fault

North of the Banknock Fault the Lower Coal Measures outcrop forms a small basin structure with low dips towards the Kinnaird area [NS 88 85] where the complete succession is preserved beneath a small outlier of Middle Coal Measures (Figure 17). The sequence is about 175 m thick. The Lowstone Marine Band, marking the base of the formation, is poorly developed in this area, with only rare marine fauna or Lingula having been found. In several bores the position of the marine band can only be recognised from the sequence of coals and in others sandstone replaces the thin coals and mudstones which are usual at this position.

The lower part of the formation from the bottom up to the base of the Mill Coal includes the Bonnyhill Craw, Colin-burn (Highstone), Armadale Main (Glenfuir), Armadale Ball and Armadale Upper Ball coals. The Colinburn and, in a small area, the Armadale Main have been worked. This interval is predominantly arenaceous and is about 52 to 56 m thick. Nonmarine bivalve faunas usually occur in the mudstones overlying the Colinburn Coal, and Lingula is present at some localities below the Armadale Main Coal representing the Sub-Glenfuir Marine Band. The Auldshields Musselband is not present.

The interval from the base of the Mill Coal to the base of the Kiltongue Musselband (Carron Two Foot) Coal is about 70 to 75 m and includes most of the workable coal seams in the Lower Coal Measures in this part of the district. The most extensive workings are in the Shotts Gas (Lower Coxrod), Lower Drumgray, Upper Drumgray and Kiltongue coals. Small areas of the Mill and Mid Drumgray Coals were also worked. The Lower Drumgray and Shotts Gas Coals occur close together with only about 2 m of strata between them. A coarse sandstone between the Airth Shellband Coal and the Shotts Gas Coal locally cuts out the Airth Shellband and the Shellband Coal. Nonmarine bivalves occur commonly in the Airth Shellband and above the Upper Drumgray Coal.

The upper part of the Lower Coal Measures from the Kiltongue Musselband Coal to the Vanderheckei Marine Band is about 40 to 45 m and includes the Kiltongue Musselband, Kinnaird House, Ladygrange and Airdrie Virtuewell coals. With the exception of the Kinnaird House Coal the seams are thick enough to have been worked, but there are no records available to show that they have been exploited in this area. The strata are predominantly arenaceous particularly between the Kinnaird House Coal and the Ladygrange Coal. There are abundant nonmarine bivalves in the Kiltongue. Musselband which occurs approximately midway between the the Kiltongue Musselband Coal and the Kinnaird House Coal. Locally the bed is split into an upper and lower musselband.

Brie Vanderbeckei Marine Band has not been found in this part of the district but its position is assumed to be in a mudstone a few metres above the Airdrie Virtuewell Coal.

South of Banknock Fault and north of Slamannan Fault

In this area the strata lie in a shallow basin structure with a general ENE-WSW elongation. The outcrop is bounded to the west and east and partly in the north and south by strata of the Passage Formation. The dips are very low and the greatest residual thickness occurs in the area to the SSE of Falkirk where all but the uppermost Lower Coal Measures strata are preserved (Figure 18).

In a few instances the Lowstone Marine Band is marked by the presence of marine fossils with Lingula or Lingula alone but commonly the base of the formation is recognised by comparison with the general succession. Locally the Lowstone Coal and the overlying mudstone are absent and replaced by sandstone.

The succession up to the Mill Coal is about 44 to 53 m thick and includes the Bonnyhill Craw (Bowhouse Main), Colinburn, Armadale Main (Glenfuir) and Armadale Ball coals, all of which have been worked in the area (Plate 10). The Armadale Main Coal commonly occurs with one or more partings of seatclay and in parts of the area cannot be traced. The Armadale Ball Coal occurs normally as an upper and lower seam. This part of the sequence tends to be arenaceous and conglomeratic beds occur in places immediately above the Bonnyhill Craw and Colinburn coals. There are a few records of Lingula in the Sub-Glenfuir Marine Band with fish scales, ostracods and nonmarine bivalves, but at many localities no fauna has been found at this horizon. Nonmarine bivalves occur commonly above the Colinburn and Upper Ball coals but development of the Auldshields Musselband varies from being a musselband ironstone to a thin coal or ironstone with mussels in the overlying mudstone. Beds of fireclay occur beneath the Colinburn, Armadale Main and Armadale Ball coals. They have been mined in places and worked opencast along with the overlying coals.

The interval from the base of the Mill Coal to the Kiltongue Musselband Coal is about 75 m to 89 m and includes, in addition to the Mill Coal, the Shotts Gas, Lower Drumgray, Mid Drumgray, Upper Drumgray and Kiltongue coals. The Mill, Lower Drumgray and Upper Drumgray coals were the most widely worked, but the Mid Drumgray and Kiltongue coals were also worked less extensively. The Shotts Gas Coal is thin of poor quality and split into leaves. Erosive sandstones occur locally above the Shotts Gas and Lower Drumgray coals. A thin musselband ironstone occurs immediately above the Mill Coal in places. Nonmarine bivalves, together with fish scales and ostracods, also occur consistently at a horizon a few metres above the Mill Coal overlying a thin poor quality coal. This position is correlated with the Airth Shellband to the north. Mussels are commonly present above the Shotts Gas Coal and occur in musselband ironstone above the Upper Drumgray Coal.

The upper part of the succession from the base of the Kiltongue Musselband Coal to the youngest preserved strata in this part of the district has a maximum thickness of 40 m and includes the Kiltongue Musselband Coal, the Ladygrange Coal, the Bellside Ironstone and Airdrie Virtuewell Coal. All three coals have been worked locally. The Airdrie Virtuewell Coal is the thickest seam and was more widely worked than the others. The Bellside Ironstone is a thin blackband ironstone but there are no records of it having been worked in this area. In addition to nonmarine bivalves there are fish scales and ostracods above the Kiltongue Musselband Coal and ostracods in strata overlying the Bellside Ironstone. There are also nonmarine bivalves above the Airdrie Virtuewell Coal.

In the Bonnybridge area [NS 825 805] Lower Coal Measures strata occur downfaulted between the Banknock Fault and the Dennyloanhead Fault. The coal seams in this area are known by local names but they can be readily correlated with the succession elsewhere. Both sets of coal names are given in the generalised vertical sections on the geological sheets NS 87 NW and NS 88 SW. The thickness of the section in the Bonnybridge area is comparable with equivalent intervals of strata in adjacent areas.

South of Slamannan Fault

The Lower Coal Measures south of the Slamannan Fault forms a broad open synclinal structure which plunges very gently towards the north. In the south-west between Salsburgh [NS 830 625] and Allanton [NS 85 58] there is a north-westerly trending anticlinal axis causing the strata to dip gently south-westwards. The complete Lower Coal Measures succession is preserved in several areas where there are small downfaulted outliers of Middle Coal Measures (Figure 19).

The lower part of the formation from the Lowstone Marine Band up to the base of the Mill Coal varies from a maximum of about 60 m in the Benhar area [NS 900 630] to less than 40 m at the south-west of the district. The marine band can normally be recognised in borehole sections in the eastern part of the outcrop where it consists of a thin bed of mudstone with Lingula and ironstone nodules. In one or two instances a marine fauna has been recorded but in most cases the position is either absent or can only be determined from the sequence of coals. In the south-west between Caldercruix [NS 82 68] and Shotts the lower part of the Lower Coal Measures is particularly arenaceous. This part of the succession includes the Colinburn, Armadale Main, Armadale Ball and Mill coals, all of which have been worked. These coals are best developed in the eastern half of this part of the district and the Mill, Armadale Main and Armadale Ball particularly have been extensively worked in the Armadale–Harthill–Shotts area (Plate 11). These coals are less well developed towards the west; south and west of a line approximately from Caldercruix to Shotts the upper coals are very poorly developed or absent. The Colinburn Coal is present but is thin and generally unworked. There are workings in the vicinity of Armadale in the Armadale Slatyband Ironstone and the Boghead Gas Coal. Boghead Gas Coal or Torbanite was a coal particularly rich in volatile constituents which was in great demand in the middle of the last century. Crude oil was extracted from the coal by heating in a retort. The seam averaged about 0.3 m thick with a maximum of about 0.5 m near Tippethill [NS 946 661]. It was of limited areal extent and was rapidly worked out, but its exploitation led directly to the West Lothian oil shale industry (Carruthers et al., 1927).

Fossiliferous horizons occur above the Colinburn and Upper Ball Coals and at two other horizons, the Sub-Glenfuir Marine Band and the Auldshields Musselband, between the Colinburn Coal and the Armadale Main Coal. These fossil horizons are poorly developed or absent in the western and south-western parts of the area. The Sub-Glenfuir Marine Band has been recorded only in the eastern part of the outcrop, from south of Arrriadale to Headlesscross [NS 912 585], where the fauna consists of nonmarine bivalves or Lingula. The Auldshields Musselband is relatively more persistent, although better developed in the west than the east; locally it develops into a musselband ironstone. The fauna in the mudstones above the Colinburn Coal and the Upper Ball Coal commonly consists of nonmarine bivalves accompanied locally by ostacods, fish scales and rarely foraminifera.

The succession from the base of the Mill Coal to the base of the Kiltongue Musselband Coal varies considerably. The thickest sequence is in the Benhar area [NS 900 630] where it is up to 114 m thick, but it reduces to less than 50 m at the western and south-western limits of the district. This includes the Mill, Shotts Gas, Lower Drumgray, Mid Drumgray, Upper Drumgray and Kiltongue coals. The Mill, Lower Drumgray and Upper Drumgray coals were widely worked in the area and the Shotts Gas was also worked to a lesser extent. There are one or two other thin coals in the sequence which have not been worked in this area. The Kiltongue Coal was worked locally in the western part of the area. The coals tend to be thin in the west and south-west, and the Mill Coal is poorly represented south of Caldercruix. It is commonly split into two leaves and the Upper Drumgray usually occurs in two or more leaves except in the Harthill area.

Nonmarine bivalves occur above several of the coal seams, locally accompanied by fish debris and ostracods.

They tend to be uncommon in the strata immediately overlying the Mill Coal but a musselband ironstone, which is known locally as the Shiels Musselband, is developed in places in the western part of the area. Mussels can also usually be found in one or more beds above the Shotts Gas Coal. Some records note mussels in the roof of the Lower Drumgray Coal and they also occur in places associated with the Mid Drumgray Coal. A persistent well-developed musselband occurs above the Upper Drumgray Coal, in some cases separated from it by several metres of strata. The Kiltongue Coal rarely has an associated fauna.

The upper part of the Lower Coal Measures from the base of the Kiltongue Musselband Coal to the base of the Vanderbeckei (Queenslie) Marine Band ranges from 29 m in the south-west to 42 m elsewhere. The section includes the Ladygrange and Airdrie Virtuewell Coals. There are also two thin ironstones which were worked locally last century. The Kiltongue Musselband Coal is a thin coal underlying the musselband. It is distinctive in that in places it consists, in part at least, of an oil shale which was extracted at one time, The Ladygrange Coal is commonly thin and is absent in the south-west, but it was worked elsewhere in small areas from several pits. The Airdrie Virtuewell is a thicker coal and was extensively worked, The Bellside Ironstone between the Ladygrange Coal and the Airdrie Virtuewell Coal, and the Roughband Ironstone above the Virtuewell Coal were worked in a smallway in the south-western part of the district. The Roughband Ironstone in places is a hard pale coloured Spinorbis limestone,

The Kiltongue Musselband is a persistent horizon and the nonmarine bivalves are accompanied by ostracods and fish debris at some localities. Nonmarine bivalves also occur, less commonly, above the Ladygrange Coal, Bellside Ironstoneand locally above the Virtuewell Coal. The Roughband Ironstone becomes in places a musselband ironstone.

Middle Coal Measures

Several small outcrops of Middle Coal Measures strata overlie the Lower Coal Measures, many of them bounded, in part at least, by faults.

In the northern part of the district, near Kinnaird [NS 88 85], afew metres of Middle Coal Measures strata are preserved in the southern part of the Kincardine Basin, The Vanderbeckei Marine Band has not been recorded and the presence of the Middle Coal Measures is interred from the thickness of strata overlying the Airdrie Virtuewell Coal.

Middle Coal Measures strata also occurdownfaulted between the Banknock Fault and the Dennyloanhead Fault

Dennyloanhead and to the north of Falkirk ((Figure 15) and (Figure 20)). About 70 m of strata are present in the former outcrop anti about 64 m to the north of Falkirk. There are about five coals in the sequence but the extent, of working, if any, is unknown. The Vanderbeekei Marine Band has not been noted in any of the bores in this part of the district but it is assumed to occur in a bed of mudstone above the Airdrie Virtuewell Coal. Some old records show a musselband ironstone at its supposed position.

In the vicinity of Longriggend [NS 82 70] and Limerigg [NS 86 71] there are a number of small outcrops of Middle Coal Measures hounded by NW-SE faults. Up to 24 m of strata are present above the Vanderbeckei Marine Band which includes Lingula and foraminifera. There are two thin unworked coals in the sequence probably representing the Airdrie Blackband and Coatbridge Musselband coals. Some nonmarine bivalves have been recovered from the mudstone overlying the Airdrie Blackband Coal and a musselband ironstone is developed in the roof of the Coat-bridge Musselband Coal. The limit of outcrop is inferred from plans of workings in coals in the Lower Coal Measures, The extent of working, if any, in the Middle Coal Measures is unknown.

Between Harthill and Fauldhouse an outcrop of Middle Coal Measures occurs between faults trending WNW-ESE (Figure 15). Up to 57 m of strata remain overlying the Vanderbeckei Marine Band, The latter occurs in a mudstone with thin clayband ironstones and includes a few marine fossils, Lingula, nonmarine bivalves, fish remains and ostracods. The Airdrie Blackband Coal and the Coatbridge Musselband Coal are both present but only the former attains a thickness which allowed it to be worked locally. Nonmarine bivalves occur above the Coatbridge Musselband Coal.

In the south-west of the district between Hareshaw [NS 815 605] and Bellside [NS 81 58] the Middle Coal Measures dip generally to the west cut by NW-SE faults and east-west faults. Up to 90 m of Middle Coal Measures strata are present and include in upward sequence the Airdrie Blackband, Coatbridge Musselband, Virgin, Glasgow Splint,

Humph, Glasgow Main and Pyotshaw coals (Figure 20). The Pyotshaw and Main coals are known to have been worked in the area and others may also have been worked. The Vanderbeckei Marine Band contains Lingula, non-marine bivalves and fish remains. Bivalves are also present above the Coatbridge Musselband, the Splint and Humph coals. A sandstone with an erosive base which becomes finer upwards occurs above the Vanderbeckei Marine Band and locally replaces the mudstone including the marine band.

Chapter 5 Carboniferous biostratigraphy

Biostratigraphical correlation of the Scottish Carboniferous was summarised by Francis (1991; see also George et al., 1976; Ramsbottom et al., 1978). For discussion of the nature and palaeoecological significance of the Dinantian and Namurian marine macrofaunas from central Scotland see Wilson (1967; 1989). Palaeoenvironments of the Bathgate Hills area at the eastern edge of the Falkirk district were summarised by Smith et al. (1994).

Viséan: Strathclyde Group (Plate 12)

West Lothian Oil Shale Formation

In the formalised miospore zonation of Neves et al. (1973), the beds of the West Lothian Oil Shale Formation from the Dalmahoy Shale to Houston Coal comprise the uppermost TC and NM zones. The strata above the Houston Coal to below the Hurlet Limestone fall within the VF Zone.

The mudstones have common plant remains and contain sparse nonmarine bivalves, principally Curvirimula scotica. Ostracods are, however, much more frequent in occurrence.

The Raeburn Shale contains ?Clinopistha parvula and Posidonia becheri; the latter is also known from the Basket (Cot Castle) Shell Bed of Strathaven and East Kilbride and has been used to recognise the P1 goniatite Zone (Chisholm et al., 1989). The overlying Fraser Shell Bed, at the base of the Fraser Shale, contains Actinopteria persulcata, Posidonia aff. corrugata, Sanguinolites spp. and fragmentary, stratigraphically insignificant goniatites. A varied fauna of productoids and other brachiopods was found in the Under Limestone of West Lothian (Chisholm et al., 1989). The freshwater, laminated East Kirkton Limestone and associated black mudstones seen in East Kirkton Quarry [NS 9902 6908] in the Bathgate Hills, contain algal? debris, Telangium sp., arthropods including Hibbertopterus scouleri, ostracods, insects and sparse articulated vertebrate skeletons. The latter include species of the genera Acanthodes, Balanerpeton, Cosmoptychius, Elonichthys, Eurynotus, Rhadinichthys, Silvanerpeton and Tristychius. The intercalated tuffs contain isolated bones, whilst the mudstones towards the top of the quarry contain fish and plant remains. The Fraser Shale has not been identified around East Kirkton (Smith et al., 1994).

The Brigantian fossil community from the 15 m-thick sequence at East Kirkton Quarry is remarkable. Terrestrial taxa were found by the commercial collector S P Wood in 1984 (Wood et al., 1985) and include a species of the genus Ophiderpeton. The significance, geological relationships and relevance of this exceptional and unusual biota were comprehensively summarised by Rolfe et al. (1994b) and associated papers discussing plants, scorpions, eurypterids, myriapods, fish and amphibians recovered from the sequence. The fauna also includes the very early stem-group amniote Westlothiana lizziae which was redescribed by Smithson et al. (1994).

At the top of the Hopetoun Member, in the shales between the Hurlet Coal and the Hurlet Limestone, a fauna was recovered from the pit at No. 16 Mine, Addlewell [NS 9979 6210]. The specimens included elements of the Macnair Fauna (Wilson, 1989) which is important for correlation purposes, with (amongst others) Lingula squamiformis, Productus cf. concinnus, Actinopteria persulcata, Sanguinolites costellatus and Streblopteria ornata.

Viséan-Westphalian: Clackmannan Group

Lower Limestone Formation

No miospores are known to have been recovered from the area of the Falkirk district. Dean (1987) referred conodont elements recovered from the major limestones of the Lower Limestone Formation of the Midland Valley to a Gnathodus symmutatus fauna. He commented that each limestone is readily recognisable from its conodont fauna (Dean, 1987, 137–138, fig. 9). The multi-element species included, amongst others, Cavusgnathus naviculus, Gnathodus girtyi, G. bilineatus, Lochriea mononodosa and Mestognathus bipluti, which are also typical of the standard British L. mononodosa and G. girtyi collinsoni conodont zones of Varker and Sevastopulo (1985).

The marine macrofaunas from the Lower Limestone Formation are, in general, more varied than those from the West Lothian Oil Shale Formation. The Hurlet Limestone itself typically contains algae, brachiopods (including Productus cf. concinnus and Schizophoria resupinata), and crinoid columnals. At West Kirkton Quarry [NS 9882 6879], also in the Bathgate Hills, the West Kirkton Limestone, which is probably a correlative of the Hurlet Limestone (Smith et al., 1994), contains a fauna of corals, brachiopods and crinoid fragments which bears some relationship to the Hurlet fauna in its more varied phase. The argillaceous marine strata stratigraphically above the limestone are particularly fossiliferous, with a diverse fauna of colonial corals, bryozoa, a greater variety of brachiopods, gastropods, and nuculoid and pectinoid bivalves. Away from the Bathgate Hills area, however, the fauna in the mudstones above the Hurlet Limestone is much less diverse, though the spines and plates of the echinoid Archaeocidaris are commonly present.

The Craigenhill Limestone is generally poorly represented in the Falkirk district. Corals, brachiopods and crinoid columnals are usually, but poorly, present. Wilson (1989) stated that the bivalve Streblopteria ornata is found in all areas where this marine bed is present.

A marine bed equated with the Craigenhill Limestone was encountered in the Rashiehill Borehole [NS 8386 7301] at 792 m depth. Within the lava pile, some 240 m below the Craigenhill position, another limestone was found, but it cannot be confirmed that this limestone, which contains Aviculopecten subconoideus, correlates with the Hurlet position. Indeed, George et al. (1976) and Wilson (1989) tentatively correlated it with the Macgregor Marine Bands (which include the Pumpherston Shell Bed) at the base of the West Lothian Oil Shale Formation.

Correlation of the Blackhall Limestone, the standard name for the former Carriden No. 5, Foul Hosie and Tartraven limestones within the district, was facilitated by the presence of the associated Neilson Shell Bed (Wilson, 1967). This development normally occurs in mudstones intercalated with and towards the top of the limestone or stratigraphically above it. The characteristic fauna of the Neilson Shell Bed, seen well, for example, at Breich Water [NS 9886 6276] , is dominated by brachiopods including Crurithyris urii, gastropods including the discoidal form Straparollus (Euomphalus) carbonarius, common nuculoid bivalves, and orthocone and coiled cephalopods including goniatites (see also Currie, 1954). Wilson (1989) listed the significant Neilson Shell Bed species as Tornquistia youngi, Borestus wrighti, Tropidocyclus oldhami, Euchondria neilsoni, Pernopecten fragilis and Posidonia corrugata gigantea which, according to present records, are only found at this stratigraphical level.

In the interval between the Blackhall and Hosie limestones in the Rashiehill Borehole, marine strata exist with Crurithyris sp., Lingula squamifonnis and bivalves. This may be the local correlative of the Milngavie and Mill Hill marine bands of the area north of Glasgow and Fife respectively. These marine strata may also be represented at Kinneil Colliery [NS 987 812].

The Hosie limestones have been extensively collected, particularly at Skolie Burn in the section between [NS 9885 6249] and [NS 9871 6242]. The combined Main and Mid Hosie limestones probably equate with the thick Petershill and Hillhouse limestones of the Bathgate Hills (Brand in McAdam et al., 1993) and the isolated marine bioclastic limestone with abundant Siphonodendron irregulare exposed at Wairdlaw (Smith et al., 1994; but see also Peach et al., 1910, p.111). In general, the lower Hosie limestone faunas are diverse and abundant, with all the major groups represented. Trepostomatous bryozoa are common, but brachiopods dominate - with Eomarginifera and other productoids, rhynchonellids and spiriferids. The bivalve Caneyella membranacea is all but confined to the Hosie limestones and more common in the lower two.

The upper Hosie limestones are generally developed in two posts: the Second IIosie and Top Hosie. They comprise a separate cycle from the lower Hosie limestones from which they are split by the Lillie's Shale Coal in the Rashiehill Borehole. Whilst corals are relatively scarce, the faunas are again rich, and all the major fossil groups are represented. Brachiopods and bivalves dominate, with the most abundant bivalve Posidonia corrugata being found especially in associated mudstones (Wilson, 1989). The discovery of the goniatite Cravenoceras scoticum in shales about lm below the local equivalent of the Top Hosie Limestone at Jackton near East Kilbride (Sheet 23W) led Currie (1954) to take the base of the Pendleian Stage (and of the Namurian Series) below the Top Hosie Limestone.

Limestone Coal Formation

Whilst the nonmarine bivalve genera Curvirimula and Naiadites are found in abundance at several horizons in the Limestone Coal Formation, and the restricted-marine brachiopod Lingula is common, beds with rich marine faunas are scarce. There are, apart from the mudstones above the Top Hosie Limestone with common Lingula squamiformis, Pleuropugnoides sp., Productus sp. and Posidonia corrugata, just two widely correlated marine hands in the lower half of the formation, and neither is generally developed in carbonate facies (but see below).

The Johnstone Shell Bed may be developed in two beds, the lower carrying the richer faunal assemblage which according to Wilson (1967) includes Serpuloides carbonarius, Lingula squamiformis, Pleuropugnoides cf. pleurodon, Productus spp., Euphemites spp., Retispira spp., Palaeoneilo luciniformis, P. mansoni and Streblopteria ornata. The information available for the Falkirk district tends to corroborate these general observations, including the relatively rare occurrence of the brachiopods Composita cf. ambigua and Schizophoria cf. resupinata, apparently for palaeoecological reasons (Wilson, 1967). Indeed, Cornposita cf. ambigua (together with Productus spp. and Streblopteria ornata) is common where the Johnstone Shell Bed is developed in a crinoidal carbonate facies (the Slingstane Limestone) in the south-eastern corner of the district.

The Black Metals Marine Band, seen more rarely in two or three beds, contains a fauna not as rich as the Johnstone Shell Bed. Where well developed, the dominant species as previously noted by Wilson (1967) are Serpuloides carbonarius, Buxtonia spp., Lingula spp., Pleuropugnoides cf. pleurodon and Streblopteria ornata. In some areas, however, only Lingula is present. In the strata above the Black Metals Marine Band, the only other marine horizon of note in the Limestone Coal Formation, apart from the shales immediately beneath the Index Limestone referred to below, is in the roof of the Bo'ness Splint Coal which contains Lingula squamiformis. It is probably the equivalent of the Lingula band in the roof of the China Coal in the Bathgate-Wilsontown area (Forsyth, 1980, p.9).

Upper Limestone Formation

The Upper Limestone Formation includes five major limestones, with several lesser marine and Lingula beds. The Index, Lyoncross, Orchard, Calmy and Castlecary limestones mark the acme of marine cycles, with their associated mudstones containing rich faunas. Biostratigraphical classification of the formation is based on goniatites and miospores, as summarised by Ramsbottom et al. (1978).

Of the rare zonally significant goniatites, Tumulites pseudobilinguis (the E1b2 Zone index) was recognised from the Index Limestone in the Cardowan No.1 bore, in the Airdrie district (Sheet 31W) (Ramsbottom, 1977), and Eumorphoceras grassingtonense (E2a1 Zone) was found in the Orchard Limestone at Orchard, in the Glasgow district (Sheet 30E) (Currie, 1954). Thus, Upper Limestone Formation strata from the base of the Index Limestone to the base of the Orchard Limestone are of Pendleian (E1 Zone) age, and the strata of the Orchard Limestone and above are of Arnsbergian (E2 Zone) age.

Smith and Butterworth (1967) established a series of 'miospore assemblages' for strata of Chadian to Westphalian D (or possibly Lower Stephanian) age based on sequences from all the major British coalfields. Their Dinantian and Namurian assemblages I-V were subsequently replaced by the schemes of Neves et al. (1972) and Owens et al. (1977) whose NC and TK zones (latest Brigantian to late Arnsbergian) included the Upper Limestone Formation. The base of the TK zone approximates to the Pendleian-Arnsbergian stage boundary.

Dean (1987) referred the conodont elements he recovered from the major limestones of the Upper Limestone Formation of the Midland Valley to a Gnathodus bilineatus-Lochriea spp. fauna. This was subdivided into a lower Gnathodus girtyi subfauna and an upper Aethotaxis advena subfauna at the top of the Orchard Limestone. The constancy of the lower subfauna limited conodonts as a biostratigraphical tool during that interval, but the faunal changes that occurred at and within the upper subfauna apparently allowed discrimination of the Calmy and Castlecary limestones (Dean, 1987, p.139, fig. 9). The Castlecary Limestone at Culross Shore [NS 9718 8557] included conodont elements assignable to (amongst others) the multielement taxa Gnathodus bilineatus, Lochriea commutata, L. mononodosa and L. nodosa, species typical of the standard British lower Gnathodus bilineatus bollandensis Zone of Higgins (1985).

Hutton (1965) showed that the Upper Limestone Formation limestones are recognisable from their foraminiferal content. There is a marked change in the faunas stratigraphically above the Calmy Limestone, and the faunas vary with facies within individual limestones.

Wilson (1967) studied the macrofaunas from all the major limestones of the Upper Limestone Formation in Central Scotland (including the more minor Plean limestones). Their few faunal distinctions are listed below, but much of the total fauna is common to most of the marine horizons in the formation and may be described as 'background fauna'. In terms of lists this has little value, but regional variations in relative abundance of various species do aid in the process of distinguishing particular beds.

The Index Limestone is recognisable by its macropalaeontological features. It contains algal concretions, though not in the Kincardine Basin (Wilson, 1967), and Latiproductus cf. latisimus is commonly present. In the shales above and below the limestone a rich and varied fauna of brachiopods, gastropods and nuculoid bivalves is usually present. The Lyoncross Limestone is faunally highly variable when traced laterally. Productoids (in particular Eomarginifera) are well represented, though not in the Kincardine Basin, and the bivalve genus Streblopteria occurs throughout. Streblopteria ornata is not found stratigraphically above the Lyoncross Limestone. The marine shales associated with the Orchard Limestone contain a very rich fauna with corals, bryozoa, many and various brachiopod and bivalve species, and trilobite fragments. The brachiopod Antiquatonia costata has only been positively recorded from this stratigraphical level in the Scottish Carboniferous. The marine shales associated with the crinoidal Calmy Limestone have a rich fauna dominated by brachiopods. It is, however, the underlying Edmondia punctatella band that distinguishes this limestone. Of the Plean limestones, No. 1 (the lowest) has the most varied fauna in the limestone and associated mudstones. The dominant species are the brachiopod Schizophoria cf. resupinata, and the bivalves Myalina mitchelli and Schizodus taiti. The higher beds typically contain many nuculoid bivalves. The fauna of the Castlecary Limestone includes algal concretions but is not distinctive.

Between the major marine limestones, beds with non-marine bivalves occur. Lingula bands are also seen, but more important is the Huntershill Cement Limestone variably developed between the Index and Lyoncross limestones and seen for example at depth in boreholes at Kinneil Colliery and Grangemouth Dock [NS 9513 8387]. Where best developed the macrofauna includes brachiopods, gastropods and bivalves.

Passage Formation

Biostratigraphical control of the Passage Formation is given mainly by goniatites and miospores (Ramsbottom et al., 1978). Stratigraphically significant goniatites occurring in the formation are Anthracoceras paucilobum (E2 Zone) the highest occurrence of which was in the No. 0 Marine Band in the No. 36 Carronhall Borehole [NS 8717 8521] (Currie, 1954), and Homoceratoides sp. (H2 or lower R1 zones) in the No. 3 Marine Band group in the Maggie Duncan's Hill Borehole [NS 9417 9053], north of Kincardine in the Alloa district (Sheet 39E) (Neves et al., 1965).

Miospores from the Bonnyside No. 2 Mine [NS 8347 7929], south-east of Bonnybridge were studied by Neves et al. (1965). They noted miospores of Arnsbergian (E2 Zone) type occurring as high as the No. 2 Marine Band, but none of Chokierian or Alportian (H Zone) age. Miospores of Kinderscoutian (R1 Zone) age occurred within the No. 3 Marine Band group, and those from coals within the No.5 Marine Band group to some distance above the No.6 Marine Band group suggested that the Marsdenian (R2 Zone) and Yeadonian (G1 Zone) stages were present. The miospores of the Bowhousebog Coal indicated with some certainty a lower Westphalian (G2 Zone) age, suggesting the base of the Westphalian Series occurs in the uppermost beds of the Passage Formation.

The best development of the Passage Formation is in the Kincardine Basin (Wilson, 1967), and the finest continuous natural section is found in Torwood Glen [NS 831 854] in the north-west corner of the Falkirk district. Here Crampton (in Hinxman et al., 1917) first described the marine bands in the Scottish 'Millstone Grit' and numbered them in ascending order from 1 to 3, the top one comprising three separate marine beds. Since then, other bands have been found and the numerical scheme has been adapted to accommodate them (Dinham and Haldane, 1932; Francis, 1956; Read, 1959). The names generally used now, in ascending order, are Nos. 0, 1 and 2 marine bands and Nos. 3, 5 and 6 marine band groups, but the scheme is still being refined. At least 17 separate marine horizons have been recorded in the Passage Formation of the Scottish Central Region, but some are of very local distribution and at no one locality are all 17 present (Francis, 1991).

In general, rich fossil assemblages are confined to the stratigraphically lower marine bands in the formation. They are very variable and are composed mainly of species present in the Upper Limestone Formation. The faunas do, however, become restricted upwards towards the base of the Coal Measures.

The carbonaceous shale immediately above the Castlecary Limestone contains the nonmarine bivalve Curvirimula sp. and fish remains. Where developed above the Levenseat Limestone, the No. 0 Marine Band typically contains Composita cf. ambigua, inarticulate brachiopods, orthotetoids, productoids, gastropods, nuculoid and other bivalves (including the E2 Zone indicator Posidonia corrugata) and cephalopods. The fauna common to both the No. 1 and No. 2 marine bands at Torwood Glen includes Composita cf. ambigua, productoids, orthotetoids, Schizophoria cf. resupinata, and gastropods. Inarticulate brachiopods and nuculoid, pectinoid and other bivalves (including Posidonia cf. corrugata) are, however, more prominent in the No. 1 Marine Band whilst Schizodus cf. taiti assumes importance in No. 2. The No. 2 Marine Band (or Roman Cement Limestone) is particularly well developed over a wide area and can be correlated throughout the Kincardine Basin and parts of the Central Coalfield. In places it is largely composed of crushed orthotetoid and Schizophoria valves (Wilson, 1967). The disconformity above the No. 2 Marine Band may be equivalent to the Mississippian-Pennsylvanian hiatus (Read, 1981). The No. 3 Marine Band group in a tributary to the River Avon [NS 9577 7946] contains a fauna including productoids, Schellwienella sp., Schizophoria resupinata, Dentalium sp. and Edmondia unioniformis. Within the district, Nos. 5 and 6 marine band groups may only be represented by Lingula mytilloides at each horizon with little else. However, there are common exceptions, an example being in the stream section near Muldron Bridge [NS 923 583] where the No. 6 Marine Band group includes the brachiopods Crurithyris sp., Lingula mytilloides and Productus sp., with Aviculopecten murchisoni and other bivalves.

Westphalian: Coal Measures (Plate 13)

The Subcrenatum Marine Band which defines the base of the European Westphalian and the Coal Measures of England and Wales has not been recognised in Scotland. Lumsden and Wilson (1979) concluded that the base of the Scottish Coal Measures should be taken at the first marine band below the lowest beds in the sequence which could be recognised palaeontologically as having a definite Westphalian age. In the Kincardine Basin this arbitrarily defined level is the Lowstone Marine Band, but work on miospores by Neves et al. (1965) showed that the base of the Westphalian in the Kincardine Basin is in fact some 70 to 80 m lower. Since the Lowstone Marine Band is the marker throughout the Central Coalfield, this means that the base of the Westphalian is stratigraphically lower than the base of the Lower Coal Measures as currently defined over a large part of central Scotland.

The Vanderbeckei (Queenslie) and Aegiranum (Skipsey's) marine bands respectively mark the bases of the Duckmantian (Middle Coal Measures) and Bolsovian/Westphalian D (Upper Coal Measures) in Scotland (MacGregor, 1960). Both bands are traceable virtually throughout Western Europe, except in some marginal areas (Ramsbottom et al., 1978).

Whilst 'Estheria' marker bands, certain ostracods with limited distributions (e.g. Geisina arcuata), long-ranging plant species and other methods have all been used in correlation of the Coal Measures in Scotland, the main methods involve miospores and nonmarine bivalves. Of the miospore zones, the SS Zone of Owens et al. (1977) and zones VI to XI of Smith and Butterworth (1967) include the Scottish Coal Measures. The upper boundary of the SS Zone coincides with the base of Zone VI. Zones X and XI have not yet been located in Scotland.

Biozonation of the Scottish Coal Measures by non-marine bivalves was initiated by Weir and Leitch (1936) who applied the emended scheme of Davies and Trueman (1927). Since becoming locally defined in terms of coals or prominent marine bands the biozones are now treated as chronozones, though they still require formal definition (Ramsbottom et al., 1978). The present scheme and relative development of faunas in each chronozone in the Scottish Coal Measures was summarised by Ramsbottom et al. (1978, fig. 14). Whilst faunal evidence of the Lenisulcata Chronozone is still scarce, there are good Communis, Modiolaris and Lower Similis-Pulchra chronozone faunas. Faunas of the Upper Similis-Pulchra, Phillipsii and Tennis chronozones, however, remain poorly represented.

Nonmarine bivalves are useful in local correlation within a coalfield but their distribution over central Scotland is variable and they are of limited application when successions in different coalfields are compared. Haldane (in Dinham and Haldane, 1932), for example, referred to difficulties in correlating the coal seams of the Clackmannan and Central coalfields. However, many of the nonmarine bivalves are characteristic of particular beds or a limited range of strata, and it is possible to recognise a series of broadly defined faunal belts within the zones based on the periods of dominance of individual species (Calves 1956; 1969).

The Lenisulcata Chronozone fauna includes Carbonicola crispa above the Colinburn Coal, and C. extenuaia, C. proxima and Naiadites hibernicus in the Auldshields Musselband. The Lowstone Marine Band at the base of the Lower Coal Measures typically contains Lingula mytilloides with sporadic Spirorbis sp., nautiloid whorls, ostracods and Planolites sp. The Sub-Glenfuir Marine Band is irregularly developed and rarely contains more than Lingula mytilloides.

The Communis Chronozone fauna contains Carbonicola polmontensis which is common in the lower part associated with C. communis and Curvirimula trapeziforma; Carbonicola pseudorobusta, C. robusta and Curvirimula candela occur above the Shotts Gas Coal, and Carbonicola oslancis, C. pseudorobusta and C. rhomboidalis above the Upper Drumgray Coal. Planolites sp. (a large form) occurs in silty beds above the Mill Coal.

The Modiolaris Chronozone includes coals from the Kiltongue Musselband Coal to the Humph Coal. The fauna in the Kiltongue Musselband includes Anthraconaia modiolaris, Anthracosia regularis, Carbonicola oslancis, C. rhomboidalis and Naiadites triangularis. The faunas above the succeeding coals up to the roof of the Airdrie Virtue-well Coal contain increasing numbers of species of Anthracosia including A. aquilina, A. ovum and A. regularis, whilst the number of Carbonicola species decrease. Naiadites quadratus and Geisina arcuata are also present at these horizons. In the roof of the Coatbridge Musselband Coal the fauna includes Anthraconaia salteri, Anthracosia pinygiana, Anthracosphaerium affine and A. turgidum. The faunas above the Glasgow Splint Coal also include Anthraconaia salleri associated with Anthracosia aquilina, A. caledonica, A. disjuncta, A. phrygiana, Anthracosphaerium exiguum and A. turgidum. Poorly preserved faunas above the Humph Coal include Anthracosia aquilina, A. disjuncta and A. phrygiana. Brand (1977) gave details of the fauna of the Vanderbeckei (Queenslie) Marine Band in Scotland and discussed the various depositional facies as interpreted from the faunal distribution. In the Falkirk district, where the faunal facies are known in the southern part of the Central Coalfield, they include the Lingula/ Foraminifera, Lingula, and pectinoid/Cephalopod facies. The last occurs in an area around Harthill [NS 905 643], and the Polkemmet 1 Bore [NS 9127 6262] contained Ammodiscus sp., Glomospira sp., Glomospirella sp., Serpuloides stubblefieldi, ?Lachlymula sp., Dunbarella sp., ?Anthracoceratites vanderbeckei and conodont elements.

In the Falkirk district the area occupied by the Lower Similis-Pulchra Chronozone is very small. Its base is taken at the Glasgow Main Coal. The roof of the Pyotshaw Coal has a fauna containing Anthracosia aquilina (Trueman and Weir non Sowerby), A. atra, Anthracosphaerium turgidum and Euestheria sp.

Chapter 6 Volcanic successions

Lower Devonian

A succession of andesitic volcanic rocks with a thin lateritic top surface, encountered in the Salsburgh No. 1A Oilwell [NS 817 649], are comparable with intermediate to acid lavas of the Lower Devonian elsewhere in the Midland Valley. These were recorded between 1216 m and 1300 m (Falcon and Kent, 1960). 'Quartz-porphyry or granophyre' (23 m) is overlain by homogeneous, white, silicified feldspar-phyric trachyte (46 m) and by a 15 m-thick sequence of red and purplish tuffs and mudstones with rare andesitic lavas (Figure 22)." data-name="images/P941480.jpg">(Figure 21).

Clyde Plateau Volcanic Formation (Dinantian)

A sequence of lavas, possibly belonging to the Clyde Plateau Volcanic Formation, was recorded in the Rashiehill Borehole [NS 839 730], near Slamannan (Anderson, 1963; (Figure 22)." data-name="images/P941480.jpg">(Figure 21)). The basal part, 67 m thick from 1111 m to 1178 m, consists of about 15 predominantly feldsparphyric lava flows, separated by boles. Most of the lavas are silicified and albitised, but the majority are clearly recognisable as comparable to the microporphyritic and macroporphyritic basaltic lavas, of Jedburgh and Markle type respectively, which are common throughout the Dinantian volcanic successions of the Midland Valley (MacGregor, 1928; Macdonald, 1975). Some flows appear to be more fractionated, and the lowest flow is a porphyritic hawaiite or mugearite with macrophenocrysts of labradorite-andesine and sparse pseudomorphs after microphenocrysts of pyroxene and possibly olivine. The groundmass consists of oligoclase microlites and iron oxides with intersertal devitrified glass.

Correlation with the Clyde Plateau Volcanic Formation is made on the basis of the petrographical features of the individual flows and the overall range of composition which are typical of the formation elsewhere. The Clyde Plateau Volcanic Formation forms an extensive continuous outcrop in the western Midland Valley to the north, west and south of Glasgow (Cameron and Stephenson, 1985). The nearest surface outcrops to the Rashiehill Borehole are in the Campsie Fells, some 13 km to the north-west (Forsyth et al., 1996), and the borehole provides valuable evidence of the continuity of the formation beneath the Central Coalfield Syncline. Comparable rocks have not been detected, however, any farther to the east or south-east, and seismic evidence suggests that the lavas thin rapidly to the east of the borehole, to be replaced by the thick sedimentary succession of the West Lothian oil shale field (Hall, 1971).

Basaltic tuffs and rare lavas at a broadly comparable stratigraphical level in the Salsburgh Oilwell, only 8 km to the SSW of Rashiehill, have much more in common with pyroclastic deposits to the east and with the subsequent Bathgate Hills Volcanic Formation, contrary to any implication that they too may be a continuation of the Clyde Plateau Lavas (Hall, 1971; Cameron and Stephenson, 1985). It therefore seems likely that the distal parts of both the Clyde Plateau lavas of the western Midland Valley and the generally younger Bathgate Hills volcanicity of the eastern Midland Valley overlap slightly stratigraphically, and possibly geographically, in the Slamannan-Salsburgh area.

Bathgate Group (Dinantian to Namurian)

The Bathgate Group is a persistent group of volcanic rocks which interdigitate with the sedimentary rocks of the upper part of the Strathclyde Group and the larger part of the Clackmannan Group (Browne et al., 1995). In the Falkirk district the group comprises the Salsburgh Volcanic Formation and the Bathgate Hills Volcanic Formation.

Salsburgh Volcanic Formation (Dinantian)

The supposed Lower Devonian volcanic rocks at the bottom of the Salsburgh Oilwell are overlain directly by 100 m of greenish tuffs and basaltic lavas of the Salsburgh Volcanic Formation with sporadic interbeds of limestone, mudstone and tuffaceous sandstone (Figure 22)." data-name="images/P941480.jpg">(Figure 21). In marked contrast to the underlying andesitic rocks, this basaltic sequence is much impregnated by calcite. It is overlain, at 1111 m depth, by an ostracod-bearing limestone, which has been equated with the Burdiehouse Limestone at the base of the Hopetoun Member of the West Lothian Oil-Shale Formation. If this correlation is correct, the stratigraphical position of the volcanic rocks is at the top of the Calders Member of the West Lothian Oil Shale Formation (see Chapter 2), in a comparable position to the Seafield-Deans Ash of the Livingston district (Sheet 32W) (Mitchell and Mykura, 1962).

Thin beds of tuff are known, mainly from boreholes, at other horizons in the lower part of the overlying Hopetoun Member elsewhere in the Livingston district (Mitchell and Mykura, 1962), It is unlikely that any of these beds crop out at surface in the Falkirk district but they may be present at depth. For example, in the Salsburgh Oilwell, a 1.5 m-thick bed of grey calcareous tuff with carbonaceous streaks occurs at a depth of 1075 m. This is equivalent to the Port Edgar Ash of the West Lothian oil shale field, as it occurs just below a limestone which has been correlated with the Barracks Limestone. There is no equivalent at Salsburgh of the Barracks Ash, which is widespread elsewhere above the limestone.

Bathgate Hills Volcanic Formation (Viséan to Namurian)

The pyroclastic activity described above can be regarded as a precursor to more persistent and widespread volcanic activity, resulting in the pyroclastic rocks and resistant basaltic lavas which form the Bathgate Hills (Smith et al., 1994). Detailed descriptions of this major volcanic formation throughout its whole outcrop are given by Peach et al. (1910) and Cadell (1925), and the northern part is described by Macgregor and Haldane (1933). Several earlier works are referred to and summarised by these authors.

The base of the formation is well marked by widespread tuffs which commence above the Two Foot Coal in the adjoining part of the Livingston district and slightly higher, above the Raeburn Shale, in the Falkirk district. Volcanic rocks are then prominent throughout the succession, with an increasing predominance of lavas, up to the top of the Limestone Coal Formation. More restricted developments of lava occur in the Upper Limestone Formation, up to the level of the Calmy Limestone, and the highest recorded pyroclastic rocks occur just above the Castlecary Limestone, at the base of the Passage Formation.

Since the Bathgate Hills Volcanic Formation is so well constrained stratigraphically by interbedded fossiliferous sedimentary rocks, and since it spans the Dinantian-Silesian boundary, the rocks are potentially very important targets for radiometric dating in the context of the international timescale. Unfortunately only K-Ar whole-rock methods have been used to date, and these have limited value owing to loss of radiogenic argon from even the freshest available samples (de Souza, 1979). Four samples of lava have been analysed (all but one from the Falkirk district) and three of these cluster tightly around 301 ± 8 Ma (Fitch et al., 1970; de Souza, 1979). This is an unrealistic date for the age of the lavas, but it does correspond closely to the age of later quartz-dolerite intrusions which may have been coeval with a hydro-thermal event that overprinted the lavas (de Souza, 1979). A more realistic date for the volcanic activity is the age of 328 ± 12 Ma obtained from the Hillhouse Sill by Miller and Brown (1965) but the significance of this early publication must be viewed with caution. All quoted dates have been adjusted using current decay constants given by Steiger and Jager (1977).

The volcanic rocks have an aggregate thickness at outcrop of around 600 m, with the thickest development in the centre of the Bathgate Hills south of Linlithgow. Their lateral extent, as determined from boreholes and mining information in the Central Coalfield, which is shown on (Figure 22), suggests that the volcanic deposits are restricted to a subcircular area, 20 to 25 km in diameter. Thick pyroclastic deposits of an apparent proximal nature occur in boreholes between Couston [NS 950 710], Reddingmuirhead [NS 916 776] and Waulkmilton [NS 980 776], suggesting the presence of a long-lived volcanic centre or several centres in this particular area (Cadell, 1925; Macgregor and Haldane, 1933). At Redding and Couston, the pyroclastic deposits occur almost up to the level of the Calmy Limestone, and at Waulkmilton, they occur up to the Index Limestone. The Bathgate Hills Volcanic Formation extends to the Rashiehill Borehole, Slamannan, where 26 flows of olivine-basalt lava with rare intercalations of sedimentary rock (total thickness 318 m) rest directly upon the Clyde Plateau Lavas and extend stratigraphically upwards to just below the Blackhall Limestone. The Bathgate Hills Volcanic Formation does not, however, extend to the Salsburgh No. 1A Oilwell [NS 8167 6487], where volcanic rocks are absent above the level of the Port Edgar Ash.

The formation is also absent from the Netherton [NS 9092 6578] and Forrestfield [NS 8604 6707] boreholes, which terminated at the Johnstone Shell Bed and Hosie limestones respectively. It seems likely therefore that there is an abrupt lateral termination to the south-west of at least that part of the volcanic pile above the Hosie limestones, and possibly of the whole volcanic field. Similarly, although some 350 m of volcanic rocks are present on the coast at Bo'ness, none have been recorded only 3 km to the north on the opposite side of the Firth of Forth.

Petrology

The volcanic rocks of the Bathgate Hills are almost exclusively basaltic. Only six major element analyses are available (Macdonald et al., 1977), two of which are from the Falkirk district (Nos. 16 and 17), and trace element data from one of these is used in a discussion of the composition of the underlying mantle source area by Macdonald (1980). The petrography of the lavas has been described in detail by Falconer (1906) and Flett (in Peach et al., 1910), who refer to some earlier descriptions. The analyses indicate that they are mostly relatively primitive, silica-undersaturated alkali olivine-basalts, commonly with sufficient normative nepheline (greater than 5%) to be classed as basanite (Macdonald et al., 1977). One analysis, from Craigmailing Farm [NS 995 727], is a hawaiite, but no other flows of more differentiated rock are known.

Petrographically the lavas are remarkably uniform. All are microporphyritic with phenocrysts of olivine and variable amounts of clinopyroxene up to 2 mm in diameter, rarely forming clusters up to 20 mm in diameter. Microphenocrysts of plagioclase are extremely rare. Most of the rocks are fine grained, commonly with an appreciable amount of brown glass in the groundmass, but some are medium-grained doleritic rocks with a slightly ophitic groundmass texture. Analcime is a common component of the groundmass, but is always of secondary origin. Falconer (1906) described a gradation of textures dependent upon the relative abundance of feldspar, augite and glassy base in the groundmass. The range extends from the medium-grained doleritic rocks, with or without olivine phenocrysts, through fine-grained basaltic rocks with both olivine and augite phenocrysts and with increasing amounts of both augite and glass in the groundmass, to 'limburgitic' basalts with olivine and augite phenocrysts set in a glass-rich groundmass. Rocks throughout this range have been classed for map purposes as either Dalmeny type or Hillhouse type in the scheme devised for basaltic rocks of the Midland Valley by MacGregor (1928). Those classed as Dalmeny type have microphenocrysts of olivine and lesser augite in a groundmass of plagioclase, augite and iron oxides. They grade into Hillhouse types with more abundant augite as phenocrysts and more especially in the groundmass, and with appreciable groundmass glass and/or analcime; most of these are probably basanites in composition. Very rare macroporphyric basalts with phenocrysts of plagioclase, olivine and lesser augite are classed as Dunsapie type.

The central parts of lava flows are commonly hard, compact and very fresh, hence well exposed at outcrop. Freshly broken surfaces are usually dark blue, lustrous and appear finely crystalline or glassy. Many appear to be aphyric, but almost always prove to be microporphyritic under the microscope. Microphenocrysts of olivine (red-brown due to alteration products) and augite (black) are also more apparent on weathered surfaces. The top and base of flows are typically amygdaloidal and/or scoriaceous with much hydrothermal alteration and are consequently less well exposed, giving rise to a conspicuous ridged topography (trap featuring) in places which reflects the alternating hard and 'soft' parts of the flows.

Kaolinised or reddened tops to flows seen in boreholes, particularly in the central part of the Bathgate Hills, but also in the higher parts of the Rashiehill Borehole sequence, indicate subaerial erosion. However, thin impersistent intercalations of sandstone, mudstone, seat-clay and coal are common, indicating that, for much of the time, the lavas did not accumulate to any great height above sea level. Coals and seatclays with rootlets are commonly developed directly on top of lava flows and fragments of fossil wood have been found incorporated in the base of flows, including some 'trunks' in apparent position of growth recorded at Grangepans by Cadell (1925).

In the northern part of the outcrop, between Linlithgow and Bo'ness, there is evidence to suggest that magma was erupted on to, or even intruded into, wet unconsolidated sediments (Peach et al., 1910). Lavas are commonly brecciated and amygdaloidal with much hydrothermal alteration and calcite veining. Irregular blocks of lava and rounded pillow-like masses are wrapped in a matrix of disturbed sediment, and sediment infills cavities or occurs as clasts within the lavas. Where lava is in contact with carbonaceous shales it is commonly altered to 'white trap' and the shale is rich in pyrite. These features were all particularly well seen in underground roadways at Kinneil Colliery, but they are also recorded from the Rashiehill Borehole (Anderson, 1963).

Succession in Falkirk district

The volcanic rocks of this district can be divided stratigraphically for descriptive purposes into four units, the boundaries of which correspond approximately, but not exactly, to those of the West Lothian Oil Shale Formation, the Lower Limestone Formation, the Limestone Coal Formation and the Upper Limestone Formation.

'West Lothian Oil Shale Formation'

The basal pyroclastic deposits of the Bathgate Hills Volcanic Formation in the Falkirk district are mainly above the Racburn Shale and extend upwards, generally to the level of the West Kirkton and Hurlet limestones, and locally to the Petershill Limestone. The latter is thought to be equivalent to the Mid and Main Hosie limestones. Flows of basaltic lava are present within the higher deposits. These flows are shown separately on the map where possible, but in poorly exposed areas, their inferred presence is indicated by the combined symbol ZB. This basal unit is broadly equivalent stratigraphically to the Longmuir and Riccarton Hills lavas of the adjoining Livingston district, but continuity of outcrop is difficult to prove owing to poor exposure. Basaltic lavas at this level are known from boreholes between Boghall [NS 995 685] and Blackburn, but in the River Almond a thin bed of tuff is the only representative.

Most of the natural exposures probably owe their existence to an increased resistance to erosion in a baked zone on top of an inclined sill of quartz-dolerite at Whitelaw [NS 994 692] and around the ruins of Craigs [NS 996 702]. Recent excavations have also revealed a 4 m-thick section above the East Kirkton Limestone in East Kirkton Quarry [NS 990 690], which has been formally named the Geikie Tuff (Rolfe et al., 1994h). More detailed information has come from borehole sections, in particular those at Silvermine Quarry [NS 991 715] and North Mine Quarry [NS 993 722] (Stephenson, 1983b).

The pyroclastic rocks are usually green, grey green or purple brown with broad colour banding. Bedding is generally poor, although sporadic graded bedding and load casts suggest subaqueous deposition. Clasts are poorly sorted and are usually subangular to subrounded, although beds of ellipsoidal lapilli are common. In boreholes at Beecraigs [NT 010 740], just within the Livingston district, lapilli tuffs have an interstitial cement of sparry calcite. Texture is variable and grain size varies widely from fine ash tuffs to pyroclastic breccias with clasts up to 8 cm long.

The clasts are almost entirely of fine-grained basalts, commonly amygdaloidal, or of reworked tuffs. Sedimentary clasts (sandstone and carbonaceous mudstone/ siltstone) occur rarely. Harder bands show some evidence of secondary silicification. Numerous seatclays occur as soft, friable, pale green or cream clays with a mossy or mottled texture. They commonly contain plant rootlets and, in the Geikie Tuff at East Kirkton, they occur within fossiliferous tuffs containing fish scales and ostracods (Rolfe et al., 1994b). Leaching at seatclay horizons below the Petershill Limestone has resulted in slight metalliferous enrichment, mainly in lead and zinc (Stephenson, 1983; Chapter 11).

Layers and lenses of chert and abundant spherulites of carbonate, which are a feature of the East Kirkton Limestone, have been interpreted as evidence of hot-spring activity associated with the volcanicity (Geikie in Howell and Geikie, 1861; Muir and Walton, 1957; McGill et al., 1990; 1994), but Walkden et al. (1994) have argued that the carbonate features are lake-floor precipitates formed within a volcanic setting, but without hot-spring activity.

'Lower Limestone Formation'

At the top of the basal pyroclastic unit, at about the level of the Petershill Limestone, lavas become dominant upwards and laterally from the Hilderston Fault [NS 991 716] southwards to Guildiehaugh [NS 987 679], south-east of Bathgate. The lavas are mostly microporphyritic olivine-basalts of Dalmeny type, but very fresh basalts with conspicuous augite microphenocrysts around the disused Duncanseat Quarry [NS 985 683] are Hillhouse type, and on the west side of Raven Craig [NS 990 705] there is a rare flow of macrophyritic Dunsapie type. To the north, thick pyroclastic deposits extend up to the base of the Petershill Limestone, but south of the Knock [NS 991 712] the limestone rests directly upon lavas.

'Limestone Coal Formation'

Above the Petershill Limestone and its associated clastic sedimentary rocks (Jameson, 1987), lavas occur throughout the Limestone Coal Formation. In the south, around Bathgate, lava flows probably occupy 50 per cent or less of the formation but they increase in thickness and number northwards, so that north of Cairnpapple Hill [NS 986 716] they replace all but the highest beds, which contain worked coals. Still farther north, virtually the whole of this part of the succession, up to just below the Index Limestone, consists of lavas and minor pyroclastic rocks, referred to as the Linlithgow Lavas and Tuffs by Mitchell and Mykura (1962). To the north of the M9 motorway, sedimentary intercalations between the lavas become thicker and more numerous, and pyroclastic rocks become more common in the Bo'ness Coalfield. Productive, coal-bearing strata are interrupted by several groups of lavas, some of which have been given local names, the Muirhouses Lavas and the North Bank Lavas, in the adjacent Livingston district (Mitchell and Mykura, 1962).

Considerable detail of this part of the volcanic succession is given by Peach et al. (1910) and by Macgregor and Haldane (1933). The lavas are probably mostly olivine-basalts of Dalmeny type, although some of Hillhouse type have been recorded, particularly in the Craigmailing-Wairdlaw area [NS 996 726]. Some of these flows contain conspicuous nodules, composed mainly of augite, as in a small roadside quarry [NS 990 732] west of Wairdlaw. Pyroclastic deposits are particularly noticeable to the west of Linlithgow where a 15 m-thick section of grey fine tuff is exposed in a stream WNW of Preston House [NS 996 758] and where tuffs have been penetrated in several bore-holes. Tuffs and pyroclastic breccias exposed in the River Avon and in a side burn at Little Mill [NS 987 781] seem to be irregular in thickness, and in distribution, but generally consist of dark green, cross-bedded tuffs with 1 cm fragments of decomposed basalt. Some outcrops have larger, fresher blocks of basalt and some metre-sized, rounded clasts have been interpreted as bombs. Some calcareous pseudomorphs after fossil wood have been recorded. Nearby boreholes have penetrated up to 150 m of volcanic rocks and Cadell (1925) has suggested that this may be the site of a volcanic neck.

'Upper Limestone Formation'

Above the Index Limestone a persistent development of lavas, up to 40 m thick, is present between Kipps Hill [NS 986 738] and Bathgate. It has also been traced westwards in boreholes and mine workings as far as Barbauchlaw [NS 927 681] and Polkemmet [NS 934 640]. In boreholes and mines between Hilderston Farm [NS 968 711] and Mosside Farm [NS 975 670], the development of lavas is present between the Index and Orchard limestones (Macgregor and Anderson, 1923, fig. 3), but east of Gormyre [NS 974 729] it may extend upwards almost to the Calmy Limestone. Some of the flows on Kipps Hill are very fresh glassy basanites with well-developed columnar jointing.

To the north, between Bowden Hill [NS 976 745] and Cockleroy [NS 989 743], the continuation of these lavas is confused by sills of quartz-dolerite and WNW-trending faults and their outcrop appears to merge with lavas below the Index Limestone.

Farther north at a similar stratigraphical level, a decomposed basalt of Hillhouse type is exposed in the River Avon near Waulkmilton [NS 983 775] and this has been traced northwards in boreholes which record 6.7 m of basalt about 30 m above the Index Limestone. On the coast, records from shafts and former exposures around Snab Pits [NS 986 809], Kinneil indicate at least two flows, one at this level and one slightly higher.

Thin beds of tuff have been recorded both below and above the Orchard Limestone near Kinneil Mills [NS 977 783] on the River Almond; and a thick bed of green tuff, directly beneath the Calmy Limestone is well exposed in a wooded glen [NS 979 734] south of Lochcote Reservoir. Volcanic rocks also occur from above the Calmy Limestone to the base of the Castlecary Limestone in a borehole at Easter Jaw [NS 8718 7452]. The youngest recorded volcanic activity in the district occurs above the Castlecary Limestone in the base of the Passage Formation. On the south side of Bowden Hill [NS 979 744] a trench exposed 2.6 m of tuffs some 5 m above the top of the Castlecary Limestone and tuffs are recorded at this level in a borehole at Melonsplace [NS 9506 7425].

Conditions of eruption and deposition

The overall regional setting of the Bathgate Hills volcanicity has been described by Upton (1994) and a detailed account of the interaction between eruption, erosion, elastic deposition and carbonate precipitation in Lower Limestone Formation time is given by Jameson (1987). Jameson envisages the volcanic rocks accumulating above sea level to form islands surrounded by coastal plains, restricted lagoons and a variety of carbonate reef facies, which accumulated during longer periods of volcanic quiescence. This succession was terminated by subaerial exposure and erosion followed by renewed volcanic activity. The model accounts for the difficulties encountered in trying to correlate the various limestones within and adjacent to the volcanic succession, since many of them were probably only local developments on the fringes of ephemeral land areas (Smith et al., 1994).

Most of the earlier volcanic deposits accumulated at or close to sea level, probably on vegetated coastal plains, in coal-forming swampy conditions or in shallow restricted lagoons. This is well demonstrated by borehole sections through the basal, predominantly pyroclastic rocks which have numerous horizons of seatclay with rootlets and fossil wood, coaly strata, and other elastic sediments with shallow water sedimentological features. Carbonaceous shales and argillaceous carbonates in the Silvermine area [NS 990 716], which are interpreted as lagoonal by Jameson (1987), contain syn-sedimentary Pb-Zn mineralisation (Stephenson, 1983b). This, and the siliceous 'sinter' deposits in the freshwater East Kirkton Limestone are possible indicators of hydrothermal activity associated with the volcanicity.

Later, as the coastal lagoons became infilled by sedimentation and pyroclastic activity, or were overwhelmed by lava flows, the volcanicity became predominantly subaerial in the centre of the Bathgate Hills. Here, lava flows commonly have kaolinised or reddened tops and intercalations of sedimentary rocks are few. Elsewhere, however, in more distal areas such as Bo'ness and Bathgate which remained close to sea level, coal-bearing strata continued to accumulate in considerable thicknesses between eruptions and there is good evidence for interaction between lava flows and wet, unconsolidated sediment.

Eventually, as volcanic activity waned, a marine transgression spread over the whole area and, by the end of Upper Limestone Formation time, limestones such as the Calmy and Castlecary were deposited without interruption across the site of former volcanic islands.

Vents and plugs

Volcanic vents and plugs have not been recognised in the Falkirk district but several cut the West Lothian Oil Shale and Lower Limestone formations to the east of the main outcrop of the Bathgate Hills Volcanic Formation, in the northern part of the Livingston district (Sheet 32W). These are thought to have fed an eastward extension of the volcanic field now removed by erosion (Peach et al., 1910). Several of the vents appear to postdate the complex folding of the West Lothian Oil Shale Formation into which they are emplaced (Cadell, 1925).

Chapter 7 Intrusive igneous rocks

Alkali dolerite sills

Sills of alkali dolerite intrude the sedimentary succession below the volcanic rocks in the Livingston district. They are similar petrographically and compositionally to the lavas of the Bathgate Hills and could be coeval with them.

Within the Falkirk district, the only sill of this type crops out to the south of the volcanic rocks, over a distance of 8 km from Blackburn southwards to Rusha Farm [NS 992 609], and at Pate's Hill [NS 990 595] where the outcrop is displaced towards the west by faulting. The sill is emplaced conformably within the Lower Limestone Formation at a constant stratigraphical level, just below the Top Hosie Limestone. The sill is composite, with an upper layer of analcime-dolcrite (teschenite) overlying a basal picrite. The junction between the layers is sharp, but with no chill on either side, and is sinuous in places. The main distinction between the layers is in the relative proportions of olivine and plagioclase, both rock types having abundant analcime and little hornblende or biotite. Analyses are given in Peach et al. (1910, p.300, nos. I and II). The analcime-dolerite was formerly quarried for roadstone and the picrite (or leckstone') was used for the soles of baker's ovens on account of its unusually low thermal conductivity. Several quarries in the Blackburn area are now filled, but a quarry at Rusha Farm exposes about 6 m (1992) of analcime-dolerite overlying 4.5 m of dark greenish grey picrite. The analcime-dolerite is also exposed in the Breich Water, in a railway cutting [NS 989 620] at. Addiewell and in Longhill Burn [NS 989 598]; at the last locality the sill underlies baked, decalcified shale. A thin sill with margins of analcime-dolerite and a core of picrite was formerly recorded about 21 m below the main sill in the Rusha area (Peach et al., 1910).

An olivine-dolerite, formerly quarried at Boghall [NS 994 683], near Bathgate, and shown as a circular outcrop on the map, is probably an intrusion of some sort. Peach et al. (1910) record that a light coloured phase of this intrusion contained abundant acicular amphibole. The quarry is now completely filled and has been built upon.

Within the volcanic sequence, outcrops of particularly fresh rock with well-developed columnar jointing could be interpreted as contemporaneous sills within the lava pile. However, they could also comprise the more massive, central part of lava flows. The Hillhouse Sill, just within the Livingston district [NT 004 747], shows transgressive junctions with the sedimentary rocks. No other evidence of an intrusive origin has been noted in the district.

Quartz-dolerite dykes and sills

Quartz-dolerite has been intruded into the Carboniferous strata of the Falkirk district both as sills and as dykes, predominantly east--west to locally ENE-trending. They form part of a major suite of high-level tholeiitic intrusions extending throughout Scotland and into the North Sea (Walker, 1935; Macdonald et al., 1981; Russell and Smythe, 1983; Smythe et al., in press). On the basis of field relationships of the intrusions in other districts (Walker, 1933; Forsyth and Chisholm, 1977; Cameron and Stephenson. 1985) and of radiometric dates of 302 to 297 Ma, K-Ar whole-rock ages (Fitch et al., 1970; de Souza, 1979) the suite is generally accepted as being of late Westphalian to early Stephanian age. There are no extrusive equivalents. The geochemistry of the suite as a whole has been investigated by Walker (1965) and Macdonald et al., (1981), and was found to be dominated by high-Fe-Ti quartz-tholeiites which are similar to basalts erupted in areas of active lithostratigraphical extension (Macdonald et al., 1981). The possible continuation of the suite across the North Sea and into the Olso Graben of southern Norway suggests that extension may have occurred in response to lithostratigraphical separation along a proto-North Atlantic rift zone to the north-west of the British Isles (Russell and Smythe, 1983).

The quartz-dolerite is well exposed in and around Torphichen particularly on Gormyre Hill [NS 976 727], Cow Hill [NS 970 740], Bowden Hill [NS 976 745] and in the village of Torphichen itself [NS 967 723]. The sill is quarried in a number of places and is an important source of crushed rock aggregate.

The quartz-dolerite sills form part of the south-western margin of the Midland Valley Sill Complex of Francis (1982). The outcrop of this major sill is imperfectly annular and characteristically dips inward towards the centre. Francis suggested that the morphology and emplacement of the Midland Valley Sill were controlled by the shape of the pre-existing Carboniferous syn-sedimentary basin. The thickest parts of the sill occur within the centre of the Carboniferous basin, which had a syndepositional dip of up to 5° towards its centre at the time of emplacement. No obvious feeder dykes have been identified within the thickest central part of the sill. Francis concluded that emplacement was at least in part controlled by down-clip gravitational flow of the magma from a series of feeder dykes located on the flanks of the sill. These dykes extend above the level of the sill. Magma first accumulated in the bottom of the basin and from there advanced up-clip tinder pressure of head fed by the dykes (Plate 14).

The quartz-dolerite dykes form narrow, steeply inclined bodies which can be traced laterally for up to 10 km. The dykes were intruded along the prominent set of east-west-trending faults, with in many instances emplacement occurring more or less contemporaneously with fault movement (Smith et al., 1994). The Lenzie-Torphichen Dyke is intruded along the Slammanan Fault and the Midland Valley Sill is present at different stratigraphical levels on either side of the fault. Individual dykes are up to 50 m thick and are commonly offset in an en-echelon mariner. Contacts with the country rocks are typically sharp; however, gradational contacts with sandstone have been reported from boreholes (Stephenson, 1983b). Fine-grained margins are usually present and two separate intrusive phases have been recognised in one dyke cut by a borehole (Stephenson, 1983b). Country-rock xenoliths are rare within the dykes. Characteristic of the quartz-dolerites throughout the district are zones of alteration to 'white trap'. These zones of hydrothermal alteration are commonly closely associated with faults and frequently show traces of mineralisadon (including calcite, pyrite, baryte and occasional chalcopyrite), and are commonly accompanied by an impregnation of hydrocarbons (Peach et. al., 1910). It has been suggested that the alteration has been produced by volatiles released during the distillation of oil shales by the heat of the intrusions (Day, 1932).

The quartz-dolerite sills occur as broadly concordant sheets up to 120 m thick with locally transgressive dyke-like bodies which cut across the regional dip of the country rocks. These sills form prominent topographical features, for example at Cockleroy [NS 990 745] and Wairdlaw [NS 996 732], with typically brown coloured, spheroidal-weathering outcrops (Plate 15). A steeply inclined transgressive step within the Midland Valley Sill Complex extends from the eastern end of the sill outcrops east of Cockleroy southwards fin 5 km via the Knock [NS 991 712], to just east of East Kirkton Quarry [NS 990 690]. At Craigs [NS 995 703] a NNW-SSE-trending sill dips moderately steeply ENE and cuts across bedding within the overlying tuffaceous rocks with minor limestones of the Bathgate Hills Volcanic Formation. These rocks are disturbed and show signs of a weak thermal metamorphic overprint. A similar transgressive relationship is observed at the Knock, where a NNW-SSE-trending sill, clipping at approximately 60° ENE, cuts basaltic lavas (Plate 14).

The quartz-dolerites consist essentially of plagioclase, augite, pseudomorphs after (olivine or hypersthene, Fe-Ti oxides and a quartzo-feldspathic or glassy mesostasis. Secondary amphibole and biotite are locally present (S34699); (S38216). The rocks show varying degrees of alteration, from relatively fresh to completely decomposed, which resulted in the development of albite, carbonate, chlorite and sericite. The tholeiitic character of the parental magma is highlighted by the presence of two pyroxenes (S37718); (S38215), a siliceous mesostasis and the unstable nature of olivine, where present. The medium- to coarse-grained quartz-dolerites are characterised by the presence of ophitic to subophitic augite (S37619), intersertal quartz or quartz-feldspar intergrowths, and equidimensional Fe-Ti oxides. Pseudomorphs after olivine are typically rare or absent within these rocks, except within the finer-grained marginal rocks (S1668); (S43572). These finer-grained rocks have previously been referred to as 'tholeiites' (Walker, 1935; Francis et al., 1970; Forsyth and Chisholm, 1977), and distinguished from the coarser-grained quartz-dolerites on textural grounds. There is no distinction between the quartz-dolerites and 'tholeiites' on geochemical grounds, with both groups having crystallised from a similar quartz-tholeiite parental magma (Macdonald et al., 1981).

Chapter 8 Structure

The rocks at outcrop in the Falkirk district are of Carboniferous age and structures affecting these rocks date from the Carboniferous Period or later, but their location and orientation may have been influenced by antecedent structures at depth.

The main structure of the district consists of a broad open syncline which crosses the district from north to south and controls to a large extent the pattern of outcrop distribution. This structure is affected by two main sets of faults: an east-west set, some of which have been intruded by large prominent quartz-dolerite dykes, and a set with a northwest to south-east orientation. Faults with a NNE trend also occur locally. The principal elements of the structure are shown on (Figure 23).

There is at the present time no general agreement on the stress system which prevailed during deposition of the Carboniferous rocks and several hypotheses are current. Russell (1971) , Haszeldine (1984; 1988) and Stedman (1988) favoured conditions of east-west tension. A system of north-south tension was proposed by Leeder (1982), Leeder and McMahon (1988) and Bott et al. (1984). A period of lithospheric stretching followed by thermal subsidence during the Carboniferous with superimposed right-lateral strike-slip was proposed by Dewey (1982) and supported by Read (1988). In addition Gibbs (1987; 1989) has suggested that the pattern of faults indicates north-easterly extension on an array of north-westerly trending dip-slip faults between ENE-trending dextral strike-slip faults. Caledonoid structures were commonly reactivated during the Carboniferous, particularly in the southern part of the Midland Valley and in Ayrshire, but there is little direct evidence of such structures in the Falkirk district.

The principal structural controls on sedimentation were fault-controlled differential subsidence and the existence of thick piles of volcanic rocks in the lower part of the Carboniferous succession.

Differential subsidence

Macgregor and Manson (1935) and Richey (1937) noted the existence of 'a line of variation' in the thickness of the succession which extends into the district from the west. The line separates an area of generally thicker strata to the north from thinner strata to the south. The variation in the Falkirk district is not associated with a single fault at surface but is evident as a fairly abrupt increase in thickness. This change in thickness cannot be precisely located but data from borcholes indicates that it is in the Falkirk to Bo'ness area. The subparallel Banknock and Mungal faults which affect Middle Coal Measures strata may be the surface expression of later movements on a deep-seated structure controlling sedimentation.

In the Alloa district (Sheet 39E), the north-south Clackmannan Syncline is more or less coincident with the Kincardine Basin (Francis et al., 1970) with strata becoming thicker towards the centre of the basin. This structure extends south into the northern part of the Falkirk district and similar thickening of strata occurs towards its axis. The syncline to the south of Falkirk does not show the same degree of differential subsidence. There is a gradual increase in the thickness towards the north but there is little indication of any thickening of strata into the centre of the syncline.

The differences in thickness both between the areas north and south of Falkirk and from east to west in the syncline to the north of Falkirk are largely confined to the Namurian strata. There is little variation in thickness in the Lower Coal Measures strata north and south of Falkirk suggesting that differential subsidence in the Falkirk to Bo'ness area had ceased to operate by that time.

A small basin structure in the Harthill to Shotts area affecting Namurian strata persisted at least into Westphalian times and the greatest thickness of Lower Coal Measures strata in the district occurs in that area.

Folding

Clackmannan Syncline and Falkirk-Stane Syncline

The major structural element in the Falkirk district is the syncline with a north-south axis, commonly referred to as the Central Coalfield Syncline, which occupies most of the district. To the north of the River Carron the structure is known as the Clackmannan Syncline (Francis et al., 1970). The continuation of that structure southwards from Falkirk is called the Falkirk-Stane Syncline. The fold is asymmetrical with dips on the eastern limb up to 30°, but in the west dips rarely exceed 5°. The syncline closes to the south with very low northerly dips south of Shotts. The eastern limb marks an important structural lineament within the Midland Valley which extends in a shallow are from the Forth at Bo'ness to south of Addiewell. The lineament, called the Bo'ness Line by Read (1988), extends north of and south of the outcrop of the Bathgate Hills Volcanic Formation.

Salsburgh Anticline

The Salsburgh Anticline lies in the south-western part of the district and has a NW-SE-trending axis. The upper part of the Passage Formation is at outcrop in the core of the anticline south of Salsburgh and around Allanton. Strata dip between 5° and 15° on the south-west limb and about 6° on the north-east limb.

The thickness of strata in the Limestone Coal, Upper Limestone and Passage formations do not seem to vary across the fold. The Lower Coal Measures are attenuated and arenaceous in this area but this is not necessarily related to the anticline.

Gibbs (1989) interpreted this structure as an extensional ramp anticline with extension towards the northeast.

Folds at Culross

In the north-eastern corner of the district around Culross an anticline and syncline with north-east to south-west axes affect the Upper Limestone Formation outcrop on either side of the Kincardine Ferry Fault. Dips across the fold pair are fairly constant at 20° to 30°. The fold axes are about 1 km apart and plunge at a low angle to the south-west.

Folds between Whitburn and Hendry's Corse

In the south-eastern part of the district there are a few open folds with generally northerly axes. An anticlinal fold extends from near Springfield [NS 938 667] SSE to near Easter Longridge [NS 959 628]. The dips on either side of the axis are less than 5° and the effect of the fold is to increase the width of the Passage Formation outcrop around Whitburn.

South of Breich [NS 964 606] an anticline and syncline with north- to NNE-trending axes expand the width of the Limestone Coal Formation outcrop. Maximum dips on the flanks of the folds are about 10° and the axes are about 1.3 km apart. The folds are present south of the east-west fault which crosses Hendry's Corse [NS 970 576].

Fold at Rashiehill

On the western margin of the district, near Rashiehill [NS 84 73], there is a broad open anticline with an ENE-WSW axis plunging gently to the east which brings the Passage Formation to outcrop in the core of the fold. Dips to north and south are less 5°.

Faulting

East-west faults

Faults with an east-west orientation are common in the district. They tend to be laterally extensive, in some cases extending from one side of the district to the other. They have in the past been considered to be simple normal faults postdating Carboniferous deposition and predating or contemporaneous with the intrusion of the quartz-dolerite dykes and sills. However, Francis and Walker (1987) have shown that several faults with a similar orientation in Fife were active during Carboniferous deposition.

In the Livingston district (Sheet 32W) Kennedy (1944) showed that there was about 180 m of dextral displacement on the east-west Uphall Fault, and Dentith and Hall (1990) concluded that there was both normal and lateral displacement on faults in that area. Gibbs (1987; 1989) referred to fault patterns in the Midland Valley and explained them as due to north-easterly extension on an array of north-west-trending dip-slip faults linked to deep-seated dextral strike-slip faults.

In that part of the district which lies to the south of Falkirk, the evidence suggests that the east-west faults are normal faults which postdate deposition. The records show no significant variation in thickness in the strata on either side of the faults. However, north of Falkirk the strata thicken rather abruptly across the line which separates differential subsidence in the north from the less rapidly subsiding block to the south. This line may also separate east-west faults in the north which show synsedimentary movement from faults to the south which, in the main, do not.

The throw on the cast-west faults ranges up to a maximum within the district of about 300 m on the Carbrook Fault in the extreme north. At least four of the east-west faults north of Falkirk have throws exceeding 200 m. Farther south the throws tend to be less but the Muirhouse and Mountcow Faults have throws which locally exceed 150 m. The direction of throw may be to either the north or the south. Information from underground mining indicates that there are one or two instances of reverse displacement on the east-west faults. A reversed throw of about 15 m occurs on a fault north of Bo'ness close to the projected line of the Mungal Fault.

The orientation of the faults varies from about 070° (Mungal Fault), to about 100° (Kincardine Ferry Fault and Crofthead Fault), In some instances the east-west faults are shown on mine plans to curve round and adopt a north-west to south-east trend with the throw down to the north and east in some cases and down to the west and south in others.

Several of the faults have quartz-dolerite dykes intruded along them. The Slamannan Fault, with a southerly down-throw of up to 80 m is intruded by the Lenzie-Torphichen Dyke. The Westrigg Dyke accompanies a fault with a northerly downthrow of about 20 m and the Croy-Cumbernauld Dyke follows for part of its course the Candie Fault which downthrows 20 m to the north. Not all east-west dykes, however, coincide with faults.

The group of faults in a zone from Bonnybridge to Grangemouth, including the Banknock Fault, the Dennyloanhead Fault and the Mungal Fault with a number of shorter cross-faults, form a fault complex. Strata of the Passage Formation and the Lower Coal Measures dip away from the complex to the north and south, and Lower and Middle Coal Measures are preserved down-thrown between the faults. The net downthrow across the zone at the western edge of the district is to the south, but in the east around Grangemouth the throw is down to the north. The influence of a deep-seated structure in this area has been postulated earlier and it seems probable that the complex is the expression of post-depositional movement on a deep-seated fracture. The change in sense of throw along the fault may indicate a component of lateral displacement.

North-west to south-east faults

Faults with this orientation are a less prominent feature of the structure than the east-west faults, although they are quite numerous. They tend to be shorter and the throws are generally less than on the east-west faults. Anderson (1951) believed these faults were later than the east-west faults and suggested a Tertiary age. Mykura (1965) showed that, in Ayrshire at least, they were active in late-Carboniferous times, and Hall(1974) demonstrated the development of north-west-trending structures in the Tournaisian. The evidence for the age of the north-west faults in the Falkirk district is equivocal. They stop against east-west faults in some cases and cut across them in others. Similarly the quartz-dolerite sills appear in some cases to cross faults with no evident displacement but elsewhere the sill is faulted. There are also instances where the sill changes horizon along a line with this orientation.

In several places mining plans show an east-west fault curving round without a break to take up a north-west to south-east alignment. The Lower Drumgray Coal is thrown down to the north-east by such a fault on the south-west side of Falkirk and the Shotts Gas Coal is affected by a similar fault north of Carronshore [NS 890 835].

There is no evidence in the district which indicates movement during deposition. Episodes of movement on the east-west faults and at least some of the north-west faults coincided or overlapped and occured about the time of emplacement of the quartz-dolerite. There may also have been later displacement. The dolerite is dated 295 Ma (late Carboniferous or early Permian).

A group of north-west faults displace Upper Limestone Formation and Passage Formation strata to the north of Bonnybridge. These faults all throw down to the south-west, two of them with throws of over 100 m, and terminate against the Banknock Fault. In the southern part of the district faults with this trend seem to be particularly common in the Armadale area and on the flanks of the Salsburgh Anticline.

NNE–SSW faults

There are a number of faults with this trend in an area between Shotts and Harthill and also in an area north of Slamannan. They tend to be short normal faults throwing in either direction. The age relations are not explicit. Some faults displace the quartz-dolerite sills, others appear to stop against them. They are assumed to be of a similar age to the two main sets of faults.

Chapter 9 Geophysics

The Falkirk district is associated with prominent and complementary gravity and magnetic anomalies centred just west of Bathgate. The anomalies are not directly related to any exposed geological formation. Early crustal-scale refraction experiments (LISPB, Bamford et al., 1978) identified a distinct velocity structure for the Midland Valley with a strong refractor at a depth of about 8 km below OD and the Moho at a depth of about 35 km. This contrasted with the Highlands and Southern Uplands blocks to the north and south and supported the geological evidence that the Midland Valley was an exotic terrane (Bluck, 1984). Intermediate depth refraction experiments using quarry blast and controlled explosion sources explored the upper 10 km of the crust in the central Midland Valley (Davidson et al., 1984; Dentith and Hall, 1989). Exposed strata in the central and southern Midland Valley have seismic velocities less than 5.7 km s-1 so that observation of a high-velocity (6.0 km s-1) refractor on the refraction lines at depths of about 4 km was used to infer a shallow crystalline basement in the central Midland Valley. Shallow crystalline basement has also been suggested for the northern part of the Southern Uplands (Hall et al., 1983).

Gravity data

Bouguer gravity anomalies for the Falkirk district, reduced to OD at a density of 2.75 Mgm-3, are shown in (Figure 24a). Anomalies are less than zero in the southwest of the district over parts of the Westphalian outcrop. To the north of the district Bouguer anomalies also approach zero on the margins of the Kincardine Basin. Maximum anomalies are close to 20 mGal adjacent to the Slamannan Fault, north-west of Bathgate. The positive gravity maximum shows a marked WNW trend and appears to extend to the local positive anomaly over the volcanic centre at Dungoil [NS 634 845] in the Campsie Fells, to the north-west of the district.

Aeromagnetic data

Aeromagnetic data were collected in 1962 at a mean terrain clearance of 305 m along east-west flight lines spaced 2 km apart with north-south tie lines approximately every 10 km. The analogue data have been digitised and interpolated onto a grid at 0.5 km. The observed total field anomaly is shown in (Figure 24b) with simple nine-point smoothing to remove data noise. Maximum anomalies are about 500 nT (above a linear field for the UK) in an area west of Bathgate.

The main part of the Bathgate anomaly is subrectangular and associated with a strong horizontal gradient running north-south along the east side of the district and then westwards to Falkirk. A distinct NW-SE feature runs across the aeromagnetic anomaly parallel to the trend of one of the main sets of faults in the district.

Source of the Bathgate anomaly

The Midland Valley Sill occurs in Passage Group and Coal Measures strata to the south of the Slamannan Fault and predominantly in Namurian strata to the north (Francis, 1982). The Lenzie-Torphichen Dyke and similar dykes might be feeders for the Midland Valley Sill. On the south side of the Lenzie-Torphichen Dyke the sill is about 50 m thick but this increases to about 120 m beneath the Forth at Bo'ness. The sill itself cannot be the cause of the Bathgate anomaly.

It is significant that the thickest section of the Dinantian-Namurian lavas in the east of the district between Bathgate and Linlithgow corresponds approximately to the position of the gravity and magnetic anomalies. At outcrop the Bathgate Hills Volcanic Formation is about 600 m thick and it attains its highest known stratigraphical position about 6km north-west of Bathgate. In the Couston area [NS 94 71] west of Bathgate, the top of the formation is at a depth of about 200 m. This suggests that the lavas are related to the source of the anomalies. At the base of the Salsburgh No. IA Well (Falcon and Kent, 1960), lavas considered to be Devonian in age occur below 100 m of volcanic rocks of the Salsburgh Volcanic Formation. The Salsburgh and Bathgate Hills Volcanic formations are considered partly responsible for the Bathgate geophysical anomalies. Lavas are also present at outcrop near Carstairs at the base of the Carboniferous and may be related to a source in the Bathgate area.

Davidson et al. (1984) presented two models as possible sources for the Bathgate aeromagnetic anomaly along a north-south profile using the observed data. In one model a thick wedge of basaltic lava extends from the Namurian to depths of about 4 km, and in the other the magnetic data, after upward continuation to 2 km, were attributed to a deep intrabasement mafic intrusion with a top at about 12 km depth. They considered these models as end members in a series of possible solutions.

Powell (1970) suggested a body at a depth of about 4.8 km on the basis of the strong gradient in the regional aeromagnetic data. Gunn (1975) provided an approximate solution to a north-south profile of the aeromagnetic data assuming a prismatic source at a depth of about 9.9 km below the data level and suggested a granitic source comparable to the Distinkhorn intrusion.

Seismic refraction data and interpretations

The LISPB profile across the Midland Valley was interpreted in terms of a three-layer crust above a relatively deep Moho at 35 km (Bamford et al., 1978). A prominent feature of the crustal velocity section in the Midland Valley was a strong refraction from a layer with velocity greater than 6.4 km s-1 at depths of about 7 to 8 km. A reinterpretation of the LISPB data (Barton, 1992) suggested a more general increase in velocity from about 6.0 km s-1 beneath the Carboniferous and Devonian strata to about 6.4 km s-1 at a refractor at about 15 km depth.

Interpretation of three refraction lines using quarry blasts (Davidson et al., 1984) suggested a refractor of about 6 km s-1 across the central part of the Midland Valley (Line 1). Since exposed rocks in the south and centre of the Midland Valley have compressional wave velocities in the range 5.7–5.9 km s-1 the refractor was considered to represent acid to intermediate crystalline rocks. Although these velocities were considered to represent crystalline basement (Davidson et al., 1984), Devonian igneous rocks are a possible source of these velocities.

The southerly MAVIS-2 seismic refraction line (Conway et al., 1987; Dentith and Hall, 1989) crossed the Bathgate anomalies close to Avonbridge [NS 910 730] and was interpreted in terms of a velocity structure which showed little correlation with the observed gravity data. This suggested that the source of the anomalies may have high density but normal velocity. A pile of Carboniferous or Devonian lavas was the preferred interpretation. The final interpretation of the MAVIS-2 line (Dentith and Hall, 1989) inferred crystalline basement with a velocity close to 6 km s-1 at a depth of about 4 km along much of the central Midland Valley with high velocity basement at about 7.5 km depth.

Physical property data

The likely range of rock physical properties in the Falkirk district shown in (Table 4) are derived from published sources and BGS sampling. Where present, the aeolian sandstones of the Stratheden Group (Upper Devonian) and the Inverclyde Group (Dinantian) can produce a marked density inversion and these lithologies might occur at depth in a broad zone across the northern part of the district (Evans et al., 1988).

The mean magnetic susceptibilities of macroporphyritic and microporphyritic Markle and Jedburgh type lavas are similar (0.06 SI), although highest values (up to 0.12 SI) usually occur in Markle types. The Dinantian and Namurian basalts generally exhibit only weak Natural Remanent Magnetisation (Palmer et al., 1985). However, the late Carboniferous intrusive rocks have significant NRM. For example, Milton (1972) observed a stable NRM (declination 175°, inclination 15°) with intensities up to about 7 A m-1 in the Midland Valley Sill Complex.

Carboniferous sonic velocities are in the range 3.0–3.7 km s-1 (Davidson et al., 1984) with Dinantian lavas close to 4 km s-1. Near-surface velocities of Devonian lavas in the Ochil Hills are about 4.1 km s-1.

Geophysical interpretation

Deconvolution

Deconvolution is a procedure for estimating the depth and position of sources of gravity and magnetic anomalies based on the derivatives of anomalies seen in profiles and grid data. A simple form of deconvolution is the estimation of depth to source from the length of the straight slope section of individual anomalies. Slope, Euler and Werner deconvolution have all been used to examine the geophysical anomalies in the Falkirk district. A plot of Werner deconvolution results for aeromagnetic data along a north-south line [on grid line 293 km E] are shown in (Figure 25). The modelled data have been abstracted from the grid of aeromagnetic anomalies and smoothed to remove data noise. The cluster of solutions at about 40 km on the profile [NS 680 km N] indicates a depth of about 3 km for the northern boundary of the Bathgate source. The solutions for the steep gradients in the anomaly at about [NS 667 km N] (SSE of Bathgate) suggest a depth of about 2 km below OD.

Euler solutions for the gridded gravity data (Figure 24a) indicate depths of about 2 to 3 km for the north side of the structure identified by the east-west feature with a strong north-south gradient in the gravity field. The solutions for Euler deconvolution of the aeromagnetic data have been plotted in (Figure 24b), although the deconvolution was actually performed on the aeromagnetic anomaly after upward continuation to 0.2 km above observation level and reduction to the pole assuming normal magnetisation. Consequently the solutions do not plot over the maximum gradients in the observed data. Magnetic deconvolution solutions are also in the depth range of 2 to 3 km.

Seismic reflection data

Seismic data in the Midland Valley suffer from excessive cultural noise and from problems associated with high-velocity dykes, sills and lavas. However, inspection of unmigrated data can provide general ideas regarding structure. (Figure 26) shows picked unmigrated reflections from seismic line SRP 3 across the Bathgate anomalies. The location of the line is shown in (Figure 27) and the observed gravity and magnetic data along the line have been taken from (Figure 24a) and (Figure 24b). Reflections have not been related to geological horizons or traced across the section. Nevertheless, there appears to be a broad zone around CDP (common depth point) 400 m which reflections below about 1.0 s TWTT are absent. This zone corresponds well with the position of the Bouguer gravity and aeromagnetic anomaly maxima over the profile. At CDP 420 on the section, the velocity function suggests that 1.0 s TINT1 corresponds to a depth of 2148 m and 0.8 s TWTT to approximately 1540 m.

Profile modelling

A 2.5D model of the crust along a north-south profile has been constructed to test possible models of the Bathgate anomalies consistent with the seismic models of the Midland Valley and the deconvolution solutions. Data were taken from grids of Bouguer gravity anomaly reduced to OD at 2.75 Mgm-3 and observed aeromagnetic data at 305 m above terrain. The magnetic observation surface was approximated as the gridded topography plus the mean terrain clearance (305 m) with a slight smoothing factor to simulate flight surface.

The model shown in (Figure 27) is part of a whole crust model down to a depth of 40 km along National Grid line 293 km E from 600 km N to 760 km N. The section extends from just north of the Southern Upland Fault to north of the Ochil Fault. The Moho in the central Midland Valley was taken as 35 km depth above an upper mantle of density 3.30 Mgm-3. A high density lower crust (2.95–3.05 Mgm-3) below a depth of about 20 km is overlain by a high-velocity (> 6.4 km s-1) layer with assumed density of about 2.90 Mgm-3 and an upper surface at about 8 km depth. The intermediate (6 km s-1) layer between 4 and 8 km depth was modelled with a density of about 2.75–2.80 Mgm-3.

The Bathgate magnetic anomaly is modelled as about 1 km of Viséan to Namurian lavas intruded by a mass with density 2.85 Mgm-3 (possibly diorite or gabbro) extending to depth of about 8 km. The Bathgate Hills Volcanic Formation extends to within about 200 m of the surface in the Couston area [NS 94 71]in the region of the maximum magnetic anomaly. In the west of the district the Bathgate Hills Volcanic Formation overlies the Clyde Plateau Volcanic Formation in the Rashiehill Borehole (chapter 6) but no rocks of the latter formation were recorded in the Salsburgh No. 1A oilwell in the southwest. In order to explain the areal extent of the magnetic anomaly about 1 km of Lower Carboniferous lavas are postulated below the Bathgate Hills Volcanic Formation in the central part of the district. To explain the positive Bouguer gravity anomaly over the lavas of the Bathgate Hills Volcanic Formation, the lavas are intruded by a basic mass of density 2.85 Mgm-3. Assuming induced magnetisation, there is a mismatch of the aeromagnetic anomaly on the north side of the Bathgate structure. Incorporation of a small NRM (0.5 A m-1) with a NRM vector direction similar to that for the Midland Valley Sill significantly improves the fit of the model. This might imply an intrusive phase after the main extrusive activity.

The smaller anomaly close to the Ochil Fault is modelled as a minor diorite intrusion. Carboniferous rocks of the Clackmannan Group and the Coal Measures extend to a depth of about 2.2 km in the north part of the Falkirk district overlying an unknown thickness of Stratheden and Inverclyde groups. The Lower Devonian here is possibly a pile of andesitic lavas similar to the Ochil Hills.

Conclusions

Inspection of unmigrated seismic reflection profiles supports the results of deconvolution of gravity and magnetic data to suggest that the depth to the source of the Bathgate gravity and magnetic anomalies is about 2 to 3 km below OD. The general pattern of the outcrop of the Viséan to Namurian volcanic rocks in relation to the Bouguer gravity anomaly map in the Midland Valley is considered to reflect the close relationship between Carboniferous basement structures, volcanicity and sedimentation.

The mean magnetic susceptibility of basaltic Carboniferous lavas is about 0.06 SI but still insufficient to generate the observed 500 nT anomaly unless the exposed lavas of the Bathgate Hills Volcanic Formation thicken rapidly west of Bathgate to over 2 km. The preferred model of the linked gravity and magnetic anomalies involves a structural high trending WNW through the Falkirk district and extending beneath the Campsie Fells. This structural high has been a focus for Dinantian (Campsie Fells, Salsburgh, Bathgate) and Namurian (Bathgate) volcanic activity. In the Campsie Fells, olivine dolerite intrusions can he identified in the caldera area and are associated with local residual gravity anomalies. A similar model is proposed at Bathgate, with denser intrusive material penetrating the lava pile from considerable depths.

Chapter 10 Quaternary

No consolidated rocks younger than the Carboniferous or possibly early Permian are known in the Falkirk district, there being a significant gap in the geological record until the onset of glacial conditions during the Quaternary.

Evidence from deep oceanic cores, showing changes in microfaunal assemblages, oxygen isotope balance and carbonate levels, have been used as indicators of growth and decay of ice sheets (Ruddiman and Raymo, 1988). The amplitude of climatic variation increased significantly 2.4 Ma ago and continued throughout the Quaternary, that is the last 1.8 Ma, during which time Scotland experienced at least 11 and probably 16 major cold periods (Price, 1983). The number of glaciations to affect central Scotland during the Quaternary is not known, but there are believed to have been at least five ice ages in the last 120 000 years. There is definite, visible, sedimentary evidence of more than one ice sheet in parts of central Scotland. In the Falkirk district, however, the last major glaciation largely obliterated the evidence of earlier ice sheets, with the exception of the 'buried channels' of the Carron and Forth where boreholes indicate water-lain sediments underlying lodgement till.

Lithostratigraphy

Formal lithostratigraphical terms have not been used in the mapping of the Quaternary deposits in the district. However, this account does take note of the formal lithostratigraphy erected for the Clyde valley (Browne and McMillan, 1989) used in the memoirs for the Airdrie, Glasgow and Hamilton districts, and includes terms used in the Grangemouth area by Browne et al. (1984) and more recently by Browne et al. (1993) and Paul et al. (1995).

Summary of late Quaternary history

Applying evidence from elsewhere in central Scotland, it is possible to construct a Quaternary history of the Falkirk district. The onset of the Dimlington (Main late Devensian) Stadial, the event with the most far-reaching effects, happened some time after 29 000 BP (radiocarbon years before present) (Jardine et al., 1988), and reached its maximum severity 18 to 20 000 years ago (Boulton et al., 1991), by which time most of Scotland, including all of the Falkirk district, and much of England were covered by glaciers. The maximum thickness of the ice sheet in central Scotland is considered to have exceeded 1 km (Boulton et al., 1991, figs. 15, 16).

The main source of ice lay in the south-west Highlands. On the basis of evidence from drumlin orien tations, glacial striae and erratic trains (Peach, 1909; Burke, 1969; Shakesby, 1978), it can be shown that glaciers moved initially south-eastwards down the Forth valley and also, at the same time, eastwards in the Kelvin valley along the south side of the Campsie Fells; these hills were eventually overwhelmed as the two ice sheets expanded (Figure 28). In the southern part of the district, Highland ice, probably before the glacial maximum, coalesced with, or was deflected by, northwards-moving ice from the Southern Uplands, where the buildup of glaciers seems to have been slower. The terminus of the ice sheet in the North Sea is believed to be marked by a distinct west-facing scarp feature at the Marr Bank 60 km off the mouth of the Firth of Forth (Thomson, 1977; Stoker et al., 1985; Sutherland, 1984). This coincides with the eastern limit of the Wee Bankie Formation (Table 5), which is interpreted as a lodgement till.

The ice sheet withdrawal and persistence of cold climates probably took place over a period of several thousand years after the glacial maximum. This is indicated by arctic or subarctic marine faunas recovered from contemporaneous sediments in the estuaries of the Forth and Tay (Paterson et al., 1981; Browne et al., 1984). Local stages in the retreat of the ice sheet may be marked by several sand and gravel trains which cross the district in a broadly west to east direction, the most prominent of which runs from Denny through Polmont to Linlithgow. Hummocky morainic deposits, occurring in two fairly well-defined east-west belts in the neighbourhood of Slamannan and Avonbridge and south of Falkirk, may also signify stages in the ice-sheet recession. Evidence for the late withdrawal of the Forth glacier is indicated by the absence west of Queensferry of the Errol Beds or their offshore equivalent, the St Abbs Formation (Table 5), which were deposited in the Tay-Earn area and the lower Firth of Forth, probably before 13 500 BP (Paterson et al., 1981; Stoker et al., 1985). The distribution of the oldest marine deposits (Loanhead Formation, Table 5) at levels up to 44 m above OD (Ordnance Datum) in the Falkirk area provide evidence for the local relative sea level at about the time of initial deglaciation.

The numerous raised and buried shorelines of the Firth of Forth, which have been well documented by Sissons (1974b; 1976) and his co-workers, reflect the variation in relative sea level that occurred during and after the ice-sheet decay. The oldest and highest recognisable shoreline in east Fife (EF-1), is believed to date from about 16 000 BP (Andrews and Dugdale, 1970). Shoreline EF-6 is about 14 750 years old (Sissons, 1974b). The most conspicuous high-level littoral platform, named the 'Main Perth Shoreline' by Sissons and Smith (1965b), is believed to have originated around 13 500 years BP, when the retreating ice front stood in the neighbourhood of Stirling and relative sea level in the Falkirk area was around 31 m OD (Sissons and Smith, 1965b). This shoreline may have formed during a period of improved climate, when isostatic recovery of the land and eustatic sea-level rise were temporarily in balance. High-level alluvial terraces of the River Avon developed at about this time.

The district is thought to have become free of ice before 13 000 BP, at the onset of the Windermere Interstadial, during which relative sea level continued to fall till about 11 000 BP (Peacock et al., 1977, fig. 4), when it may have stabilised to form the 'Main Lateglacial Shoreline' at an elevation close to that of sea level today (Browne et al., 1984, p. 12; Sissons, 1966). This feature is associated with a widespread marine erosion surface which commonly is covered by a thin lag gravel layer in the Grangemouth-Bo'ness area (Bothkennar Gravel Formation, (Table 5)). The shoreline and associated platform features may have formed entirely within the Windermere Interstadial (Browne et al., 1984), or within the Loch Lomond Stadial (Sissons, 1966).

A return to very cold conditions brought about the onset of the Loch Lomond Stadial at about 11 000 BP. Valley glaciers formed in south-west Highlands, but none reached the Falkirk district. Consequently, there are no definable glacial deposits of this age in the district, although the prevailing periglacial conditions would undoubtedly have led to the creation of mass movement deposits such as screes, landslips and soliflucted matter. Early in the stadial, relative sea level may have fallen some metres below OD. However, at the acme of the Loch Lomond Stadial glaciation, relative sea level was several metres above OD. Three distinct and subsequently buried beaches developed (Sissons, 1966; 1969; 1972; Sissons and Smith, 1965a). The 'High Buried Beach' is intimately associated with the Menteith terminal moraine of the Forth Glacier.

A fairly rapid climatic improvement, marking the end of the Loch Lomond Stadial, commenced about 10 000 BP, accompanied by fluctuations in sea level. Sea level fell progressively with the formation of the 'Main' and 'Low Buried beaches', creating exposed mud flats over a large area of the estuary, on which peat subsequently accumulated. This organic deposit is known as the sub-Carse Peat.

The most significant Flandrian marine transgression commenced about 8500 BP, accompanied by the deposition of the widespread carse clays. The 'Main Post-glacial Shoreline' also developed during this period, between 7605 and 5830 BP on the basis of evidence from east Fife (Chisholm, 1971). Subsequently there was a staggered gradual fall in the marine limit back to its modern level.

On land during this time, alluvial terraces of the major rivers and streams formed, together with locally extensive deposits of blanket and basin peat, and a few lacustrine deposits accumulated in some of the hollows inherited from the glacial period.

Devensian topography

The major rivers of the district, which mainly flow eastwards, display a superimposed drainage pattern, as they clearly traverse the major structural elements which have a north-south trend. George (1974) alluded to a Neogene initiation of the river system. He also hypothesised on the primary drainage regime whereby the Kelvin originally flowed ENE via the valleys of the Bonny Water and 'lower Carron', with the upper reaches of the latter, together with the 'upper Endrick', forming a subsequent tributary. Also the 'upper Forth' flowed through Strathallan and the 'lower Forth' followed the valley of the River Devon (Figure 28).

Similar ENE orientations of the principal rivers in the southern half of the Falkirk district, suggest that they are also consequent streams. The River Almond, together with the upper part of the South Calder Water, follows an ENE trend, as does the River Avon with its tributary the Drumtassie Burn and the upper reaches of the North Calder Water. The sudden westwards diversion of the Avon at Linlithgow is most probably the result of an earlier glaciation, which blocked the valley north-east of Linlithgow. The original confluence with the Forth may coincide with the Black Burn below Blackness (Cadell, 1913; McAdam et al., 1993, map 2).

Overdeepened, drift-filled, rockhead depressions exist beneath the valleys of the Forth, Carron, Almond and Avon. Since none of the deposits infilling these depressions has yielded fossils, it is not known whether the sediments are preglacial, interglacial or late Devensian in age, although on the evidence of their shape the channels are likely to have been cut subglacially. The magnitude of the major rockhead channels and the lithology of the infill suggest that the features are not the product of a single glaciation. Lodgement till is commonly underlain by waterlain deposits, probably of fluvioglacial origin.

The Carron depression (Cadell, 1913; pp.85–87) is a 14 km-long trough running eastward from Bainsford [NS 89 82] and passing to the north of Bo'ness, having joined with the Forth trough in the vicinity of Grangemouth Docks (Figure 28). Rockhead is generally more than 70 m below OD along the centre line of the depression, but is much deeper north of Bo'ness where the drift thickness commonly exceeds 150 m. Most of Grangemouth lies above the south side of the Forth/Carron depression. Upriver from its confluence with the Carron trough, the Forth depression diminishes quickly and is a relatively weak feature compared with the Carron depression.

Cadell (1883; 1913) alluded to an additional 'channel' north of Preston Island [NT 006 852], citing evidence from mineworkings and bores sunk to investigate it during the nineteenth century, but no records of these have survived. Coal mining operations have often been frustrated by these depressions. Half a mile (800 m) offshore from Bridgeness [NT 015 815], mineworkings struck till at 174 m below OD, with the interface displaying a steep dip to the north. In the Carronshore Pit in 1829, running sand was struck about 73 m below surface (Croll, 1870). More recently, in the NCB Kinneil-Valleyfield colliery complex rockhead was encountered at 203 m below OD in the workings [NS 9983 8306] for the Cowdenbeath Seven Foot Coal. Approximately 2.3 km upstream from there, a borehole sunk in connection with a proposed extension to the Upper Hirst Coal workings, proved rockhead at 165.9 m below OD, beneath 161.5 m of superficial deposits.

Pre-Dimlington Stadial deposits

Direct evidence of earlier glaciations is lacking in the Falkirk district, but in the adjacent Airdrie district (Sheet 31W), there are several occurrences of multiple till sequences interbedded with waterlain deposits, for example at Chapelhall [NS 780 630] (Geikie, 1863; Clough et al., 1916) and Baillieston [NS 693 641] (Browne and McMillan, 1989). Indirect evidence of more than one glaciation is possibly afforded by drift sequences proved in the major bedrock depressions, where sediments underlying till may predate the last ice sheet. For example, boreholes along the line of the Carron depression have proved sand and gravel deposits underlying thick sequences of lodgement till.

Dimlington Stadial ice sheet

Evidence for the timing of the onset of the Dimlington Stadial, is available from two sites in western Scotland. At Sourlie in Ayrshire, radiocarbon dates in the range 2930 000 BPwere obtained from antler and plant remains in sediments sandwiched between two lodgement tills (Jardine et al., 1988); while at Bishopbriggs a woolly rhinoceros bone from a sand deposit underlying Baillieston Till was dated at 27 500 BP (Rolfe, 1966; Browne and McMillan, 1989). A poorly preserved molar tooth of Elephas primigenius was discovered approximately 12 m below the surface in a sand pit at Headswood [NS 827 819] in 1937 (Absalom and Henderson, 1947), but it has not been dated. Jardine et al. (1988) concluded that interstadial conditions existed at least in lowland Scotland between 33 500 and 26 000 BP.

The ice sheet built up initially in the western Highlands, and glaciers spread southwards and eastwards on to the lowlands, at first following the principal valleys, such as the Forth and Kelvin-Bonny/Carron alignment, but eventually the entire area was overwhelmed. The direction of ice movement can be gleaned (Figure 28) from the orientation of drumlins (Burke, 1969), glacial striae (Hall, 1815; Geikie, 1863; Richardson, 1877; Cadell, 1913; Macgregor and Haldane, 1933), and the distribution of erratic trains (Peach, 1909; Burke, 1969; Shakesby, 1978).

In the central part of the Falkirk district, where drumlins are particularly well developed, the preferred orientation swings from ENE-WNW in the west of the district to east-west around Bathgate and Linlithgow (Figure 28). In the higher ground south of Falkirk, between Auchengean [NS 857 770] and Maddiston [NS 940 765], the ice-sculpted till ridges are unusually large, several of them exceeding 3 km in length. Drumlins become increasingly rare towards the southern part of the district; this may be a reflection of the increasing influence of the Southern Uplands ice that appears to have been incapable of forming drumlins hereabouts. Very few exist south of the M8 motorway, except for an area around Hareshaw [NS 81 60], and at Longridge [NS 95 62] where there are two prominent linear features, although in the case of the latter, rock crops out at the surface (Macgregor and Anderson, 1923). In the southern part of the district, the clearest indication of the influence of Southern Uplands ice is given by striae exposed in the Leven Seat Sandstone Quarries [NS 94 58], oriented mainly NNE to north-east. This would accord with an ice sheet emanating from the hills to the south, and possibly being deflected eastwards towards the Firth of Forth.

The only other location where there is a deviation in the trend of glacial features from the ENE and easterly directions described above, is in the extreme north-west corner of the district around Torwood [NS 84 85], where the principal orientation of striae is from SSE to south-east. This almost certainly results from the deflection of the ice sheet by the mass of the Campsie Fells, as the general course of the Forth Glacier would have been ESE in this area.

Further evidence of ice movement is provided by erratic trains, the most distinctive here being that of the Lennoxtown essexite (nepheline monzo-gabbro) which has been traced from its source in an easterly direction across the Falkirk district within a strip bounded on the north by Denny and Larhert and on the south by Camelon (Peach, 1909). The train is obscured by the fluvioglacial and carse deposits south of Grangemouth, but has been detected between Linlithgow and Bo'ness (Figure 28). More recently, Shakesby (1978) confirmed Peach's findings as far east as Larbert, but he also detected a southerly deviation of the trace around Denny, which he attributed to the influence of the ice stream which flowed SSE from Stirling.

Glacial deposits

The principal deposit laid down by the ice sheet is lodgement (subglacial) till, which is present at surface over much of the district. Unless rock is exposed at surface, till is likely to be present almost everywhere, although it may be concealed by younger superficial deposits. Till is commonly thin or absent in areas of elevated terrain such as the Bathgate Hills, between Caldercruix and Kirk o' Shotts, west of Armadale, around Leven Seat and Torwood, and south of High Bonnybridge. Till thickness varies considerably. The thickest deposits are likely to be found in large drumlins and in buried channels. For example, Link Road M8/M9 Borehole No. 51 [NS 9514 7308] sunk through a drumlin at The Desert [NS 951 732] penetrated 53 m of drift, most of which was till, and another at Grangemouth refinery proved 61 m of till beneath 70 m of marine deposits.

Despite the large accumulations of lodgement till, conclusive evidence of multiple till sequences separated by waterlain deposits, has not been found in the district, unlike in the adjacent Airdrie district where up to three distinct lodgement tills have been described.

Lodgement till in the Falkirk district probably belongs to the Wilderness Till Formation (Table 5) as defined by Rose et al. (1988) and Browne and McMillan (1989, table 1), but the term has not been used in the mapping of the district. It is typically a very stiff, overconsolidated, fissured, sandy, silty, stony clay with clasts which are angular to well rounded in shape and range from granule up to boulder size. The colour is commonly dark grey or brownish grey, but may also be found in shades of blue through to black, the tone usually being influenced by the colour and lithology of the bedrock from which the till was derived. Within 1 to 2 m of the surface, the colour is usually brown, owing to weathering.

Hummocky morainic deposits comprising a sandy, silty, stony, diamict assemblage, exist in two quite narrowly defined east-west-orientated belts in the northern half of the Falkirk district (Figure 28). The southern outcrops have been mapped from Glenhove [NS 773 724] on the Airdrie district eastwards into the Falkirk district where they are mainly confined to the valley of the River Avon running from the western margin of the district at Fannyside Mill [NS 810 733] to Avonbridge. However, mounds of this material have been mapped as far cast as the north-western outskirts of Bathgate near Ballencrieff Mill [NS 964 696]. The northern occurrence features more disparate outcrops in an area stretching east from Lochdrum [NS 816 779] to Glen Village [NS 885 782] south of Falkirk. Both these deposits are assigned to the Lochdrum Member of the Wilderness Till Formation (Table 5).

The deposits commonly occur in mounds which are not consistent in shape, size or orientation. They can be circular, oval or arcuate in outline, they may be steep sided or gently sloping, and the maximum dimension can range from as little as 20 m to about 400 m. The form of the mounds is not dissimilar to the topography associated with severely kettled sand and gravel deposits. The orientation of the elongate mounds is very variable. In places, the long axes are parallel to the direction of ice movement, whereas elsewhere the main axes run transverse to it. Examples of the former can be seen at Wester Jaw [NS 851 739] and near Glen Village, and well-developed transverse mounds straddle the Avon valley at Thieves Hill near Jawhills [NS 815 734] (Plate 16), at North Bankhead [NS 891 734] and at Avonbridge. Several good examples partially obstruct the valley of the Glen Burn below Glenrig [NS 869 778].

Hummocky morainic deposits of the Lochdrum Member are distinguished lithologically from morphologically similar ice-contact deposits of sand and gravel by their diamict nature and the angularity of the clasts (Plate 17). The morainic material typically comprises mainly angular pebbles, cobbles and boulders of sandstone in a sandy silt matrix. There is almost no sign of sorting, although indications of debris flow are quite common in the rare sections that have been observed. North-west of Rashiehill [NS 840 730], hummocky morainic deposits appear to be closely associated with several small eskers and kames composed of sand and gravel, which was probably deposited penecontemporaneously.

The Lochdrum Member deposits would appear to be rare in central Scotland. They are almost certainly related to the Dimlington Stadial ice sheet and probably originated in an englacial or supraglacial environment. The trend of the two belts follows the direction of ice movement as displayed by striae and drumlins, namely north of east in the west of the district, and nearly due east farther east.

The sandstone clasts and much of the matrix appear to have been scoured from the outcrop of the Carboniferous Passage Formation on the western limb of the Central Coalfield syncline; in fact, the western limit of the deposit coincides with the western margin of the Passage Formation outcrop. The isolated mounds near Bathgate also coincide with the outcrop on the eastern limb of the syncline. But why the material is confined to two well-defined belts is not clear. It is noteworthy that the outcrops in the Avon valley appear to have been replaced in an easterly direction by glacial meltwater deposits, but similar deposits also occur to the west of Glenhove. Although this may be coincidental, it could indicate that the sand and gravel was laid down to the east of an ice front which stood in the vicinity of Avonbridge for some time. The hummocky morainic deposits are not sufficiently linear to suggest that they were lateral or medial moraines, but the transverse mounds described above may be indicative of terminal moraines deposited during minor stillstands of the retreating glacial front.

Glacial meltwater deposits

With the climatic change that heralded the end of the Dimlington Stadial, the ice front retreated as the Southern Uplands and Highland ice sheets downwasted. Initially, ice cleared from the highest ground in the district, namely the Campsie Fells and also, at an early stage, from the Bathgate Hills and the relatively high ground in the south.

Glaciofluvial deposits

Glacial meltwater deposits occur principally in a series of broadly east-west-trending belts. In the district there are three main belts with a fourth small area of sand and gravel around Pate's Hill [NS 990 595]; high maximum elevations, in the range 285 to 245 m OD, indicate, at least, an initially early phase of deposition (Figure 28).

Moderately extensive glacial meltwater deposits crop out between Allanton and Stane in the south of the district, with small patches occurring as far east as Fauldhouse. The deposits south of Fauldhouse in the vicinity of Headlesscross [NS 912 585] include several esker segments and display maximum elevations between 235 and 215 m above OD, which, in common with the Pate's Hill deposits, each demonstrates an easterly decline in altitude, suggesting meltwater flow from the ice-filled Clyde basin to the Firth of Forth. By contrast, the maximum elevations of the sand and gravel deposits occurring between Allanton and Stane, decline from about 257 m above OD near Springhill [NS 891 591] in the cast, to approximately 165 m above OD at Eastmains [NS 842 571] in the west, indicating drainage into Lake Clydesdale, where lacustrine clays of the Bellshill Formation (Table 5) are known at elevations of about 180 m above OD, declining north-westwards to 60 m above OD (Browne and McMillan, 1989, p.13).

Farther north around the M8 corridor and in the hilly ground between Caldercruix and Armadale, sand and gravel deposits are rare, indicating that ice wastage took place hereabouts without significant production of meltwater streams.

Between Avonbridge and Bathgate, sand and gravel deposits are quite extensively developed in a sinuous belt which clearly indicates that meltwaters were deflected southwards by the Bathgate Hills. However, maximum elevations of the deposits indicate that two meltwater systems were present. In the neighbourhood of Bathgate, the maximum altitude of sand and gravel deposits rises eastwards from about 125 m above OD at North Couston [NS 955 712] to 145 m above OD near Ballencrieff Toll [NS 976 701], increasing to 150 m above OD in Bathgate, and reaching 165 m above OD to the east of the district. Although these elevations increase eastwards, it is suggested that meltwaters ultimately escaped eastwards to the sea via the valleys of the Brox and Lochshot burns (tributaries of the River Almond), and that deposition coincided with a gradual or stepped retreat of the ice front which declined in altitude as it retreated westwards. However, in the valley of the River Avon, there is a gradual decline eastwards from about 155 m above OD at Fannyside Mill [NS 810 733] to 120 m above OD near Crawhill [NS 946 729], a distance of 13.5 km, which may be explained by rapid melting of a stagnant ice mass.

North-west of Ballencrieff Toll, where the deposits occur at a maximum elevation of about 145 m above OD, which is similar to the height of the watershed at the source of the Lochshot Burn, there is a distinct drop in altitude to the meltwater deposits near Dykeside [NS 967 703], which may indicate a resumption of drainage via the River Avon when the ice front had receded this far. Temporary damming of this valley somewhere between Westfield [NS 940 724] and Muiravonside [NS 969 757], either by ice, glacial debris or landslip, is indicated by deposits of glaciolacustrine silt and clay up to 13.4 m thick, extensively developed along a 3 km stretch of the valley of the Couston Water around North Couston [NS 956 712], at surface elevations between 120 and 125 m above OD.

The sand and gravel deposits in this belt between Slamannan and Bathgate are mainly in the form of mounds, indicating a dead-ice depositional environment, but a series of terrace remnants with locally well-developed back features flank the Avon valley between Avonbridge and Crawhill, at elevations up to 30 m above present river level. A 1.7 km-long beaded esker follows the valley of the River Avon near its source, north of Shielknowes [NS 828 728]. Another esker descends the valley side at Kaemuir Farm [NS 937 729] for about 300 mfrom an upper elevation of 135 m down to 125 m above OD. Several elongate mounds of sand and gravel bordering the alluvial plain of the Couston Water west of Hilderston Farm [NS 968 712], probably had a similar englacial or sub-glacial mode of origin. Moundy deposits of sand and gravel occur discontinuously between Crawhill and Easter Inch south of Bathgate. These features are particularly well displayed on Bathgate Golf Course [NS 98 68].

The most northerly, and by far the largest belt of sand and gravel deposits stretches from Denny and Bonnybridge through Camelon, Falkirk and Polmont to Linlithgow (Figure 28). This train of meltwater deposits is contiguous with those occupying the overdeepened valley of the Kelvin, crossing the watershed between this river and the Ronny Water at Kelvinhead [NS 757 785]. Sedimentological evidence from exposures at Headswood [NS 827 819], Avondale Sand Pit [NS 955 788] and Kettlestoun Mains [NS 988 763] all indicate easterly meltwater flow.

The Polmont esker (Plate 18), which once formed a prominent feature over a distance of 6.5 km, follows a sinuous course between Callendar Park [NS 900 793] and Haining Wood [NS 956 775], and confirms the direction of meltwater drainage towards the sites of Linlithgow and Linlithgow Loch, Near Gilston [NS 945 783] the esker bifurcates, with the northern branch running ENE towards Avonbank [NS 965 785], but only rare traces of these two branches remain, owing to extensive quarrying activity. The maximum elevation of the esker remains fairly consistent, at approximately 70 m above OD, but the highest recorded value, in excess of 75 m above OD, pertained to the most easterly recognisable esker segment, formerly located beside the railway line near Haining Wood. Earlier workers (Gregory, 1913: Peach ert Geikie et. al., 1879) described the esker as being up to eight miles (13 km) long, extending from the centre of Falkirk to east of the River Avon at Linlithgow. This is now difficult to corroborate owing to the development of Falkirk town centre, and there is no sign that it ever existed east of a former pit near Lathallan [NS 958 775]. Gregory (1913) described the sinuous and undulating course of the esker. He initially, and probably correctly, considered the concept of subglacial tunnels to explain the rise and fall of its base, but went on to reject that theory in favour of an ice-marginal mode of origin.

The sand and gravel deposits bordering the esker almost certainly postdate it and are probably proglacial or supra-glacial for the most part. East of Polmont the meltwater sediments were laid down over a pre-existing drumlin field which they only partially mask. The flanks and top, of a few of the drumlins have thinning-upward drapes of sand and gravel, including some very large drumlins, for example south of Avondale House [NS 955 792] at Myrehead [NS 963 777] (Plate 19) and north of Waukmilton [NS 980 777] with elevations of 64 m and 67 m above OD respectively. These levels are similar to the maximum altitudes of spreads of sand and gravel around Linlithgow and indicate deposition by glacial outwash when the surface of the ice sheet was al or above the level of the tops of the drumlins.

With continued retreat of the ice front, the Linlithgow 'channel' was abandoned in favour of a more direct route into the Forth, west of Bo'ness. Deposits of sand and gravel in the Denny and Bonnybridge areas occur at maximum elevations of approximately 50 m above OD. Whereas the sand and gravel in the valley of the Ronny Water is in continuity with the deposits in the Kelvin valley, those occupying the Carron valley between Denny and Dunipace are associated with numerous glacial meltwater channels which traverse the flanks of the Campsie Fells above Kilsyth and Banknock, and descend eastwards from the upper Carron valley. The distribution of the sand and gravel indicates that deposition probably took place marginally to the ice sheet with meltwaters being confined between the Forth glacier and higher ground to the south. Farther east, in the neighbourhood of the Hills of Dunipace [NS 837 818] and Bonnybridge, they merge with sand and gravel deposits of deltaic and estuarine origin which now cover large areas of Stenhousemuir, Larbert, Camelon and Grahamston (Browne, 1977).

Marine deposits

As the ice front retreated westwards glaciomarine clay and silt with subordinate seams of sand began to accumulate in and around the Firth of Forth. These were deposited by meltwater plumes emanating from the retreating ice front. The oldest estuarine deposits in the Grangemouth area were originally named the Loanhead Beds (Browne et al., 1984), which comprise brown to brownish grey or reddish brown, plastic silty clay, with laminae and thin beds of reddish brown clay. The deposit is locally thinly bedded and may display closely spaced colour lamination. The deposit also contains silty and sandy laminae and angular clasts up to 50 mm long, considered to be dropstones. Brown silty clays occurring at about 44 m above OD near Glenfuir House [NS 8617 7987] are also assigned to the Loanhead Formation (Browne et al., 1984; 1993; (Table 5)), and indicate that the marine limit at that time was well above the level of the Main Perth Shoreline (c.31 m above OD at Grangemouth), but below the extrapolated height of east Fife shoreline EF-6. Deposition of the Loanhead Formation therefore probably commenced well after 14 750 BP, on the basis of age determination by gradient, of the latter shoreline (Andrews and Dugdale, 1970; Sissons, 1974b). These deposits contain a restricted fauna, indicating unfavourable environmental conditions, although less severe than during deposition of the somewhat older Errol Beds of the Tay-Earn area (Paterson et al., 1981). The latter are not present in the Firth of Forth, probably owing to the later recession of the ice front in this area.

At Kinneil Kerse and around Bothkennar, the Loanhead Formation is overlain by the Kinneil Kerse Formation (Browne et al., 1984; 1993; (Table 5)), comprising grey, locally yellowish brown and greyish brown, laminated silty clay, with laminae and bands of silt and fine sand very common in places. Although they contain a more diverse fauna than the underlying formation, these beds are believed to reflect conditions which had become only marginally less harsh, The Kinneil Kerse Formation is only locally developed and is thought to be the product of lateral deltas entering the estuary from the Avon and Carron valleys.

Windermere (Late Glacial) Interstadial

The continuing fall in sea level was halted for a time while the ice front probably stood at about the position of Stirling. This led to the formation of the 'Main Perth Shoreline' at an elevation of about 31 m above OD (Sissons and Smith, 1905b). During this period, higher wave intensity resulting from more open-water conditions may have existed in the estuary. This could explain the non-sequence at the base of the Abbotsgrange Formation (Browne et al., 1984; 1993; (Table 5)), which is believed to have been deposited during this period. The existence of a discontinuity is reinforced by a borehole record at Grangemouth Docks [NS 9175 8326] showing the Abbotsgrange Formation deposits resting on till. Above the basal beds, which are quite sandy with clasts up to 80 mm, the Abbotsgrange Formation comprises black, grey and brownish grey, loose silts with numerous laminae and bands of tine sand and dark grey silty clay. The deposits are generally flat bedded, although ripple lamination occurs locally, indicating a shallower depositional environment than the older Loanhead and Kinneil Kerse formations, Pro-deltaic conditions probably prevailed at the mouth of the Carron-Ronny 'river'. In general the faunas recovered from this Formation indicate a transition to a more temperate climate. It is believed that during the deposition of the Abbotsgrange Formation, relative sea level eventually fell to an elevation close in that of present day, not long after 12 000 BP (Peacock et al., 1977; 1978).

Loch Lomond Stadial

Glacial conditions returned to Scotland during the Loch Lomond Stadial about 11 000 to 10000 BP. Glaciers advanced southwards from the Highlands into the Forth and Teith valleys but the terminal moraines are at least 25 km west or north-west of the district. However, the severe periglacial environment would have accelerated the formation of screes and mass movement deposits on land.

In the marine environment, a widespread erosion surface, backed in places by steep cliffs, was recognised by Sissons (1969), on the basis of bore- and auger-hole evidence. This feature, the 'Main Lateglacial Shoreline' (Sissons, 1974b), slopes east at 0.17 m/km. It lies at about OD at Grangemouth and 1 m above OD at Airth. Sissons thought the erosion surface was the product of wave and frost action, and has been correlated with the extensive wave-cut platform found on the west coast of Scotland (Sissons, 1974a). Gostelow and Browne (1980) showed that the buried eroded surface of the Loanhead Formation was overconsolidated locally. This, they suggested, might result from dessication caused by subaerial exposure under periglacial conditions down to a level of 9 m below OD. This explanation, however, was rejected by Sutherland (1985). The surface is commonly overlain by a thin bed of gravel, possibly a lag deposit, named the 'buried gravel layer' by Sissons (1969), and later the Bothkennar Gravel Formation (Browne et al„ 1984; 1993; Paul et al., 1995). The deposit usually consists of subangular to rounded clasts ranging in size from line gravel to boulder (Cadell, 1913) in a diverse matrix which can vary from loose sand to clayey sandy silt. The thickness of the deposit is commonly 0.5 to 2.0 m, but can reach 4.0 m.

The age of formation of the erosion surface and the overlying Bothkennar Gravel is disputed. Sissons (1974a; b) concluded that they formed initially during the later part of the Windermere (Lateglacial) interstadial, but mainly during the first half of the Loch Lomond Stadial. However, Browne et al. (1981) proposed that the required sea-level stability occurred when rapid eustatic rise balanced isostatic recovery, ideally during a period of climatic amelioration such as slightly earlier in the Windermere Interstadial, when a marked enstanc rise has been widely recognised in north-west Europe.

Paterson et al. (1981) maintained that during the Loch Lomond Stadial, sea level fell considerably below present, a view which is supported by the evidence of gullying to about 10 m below OD, and exceptionally to 28 to 32 m below OD at Grangemouth, marked by the base of the Letham and Claret formations (seebelow), In contrast, Sissons believed that sea level rose from the level of the 'Main Lateglacial Shoreline' to that of the 'High Buried Beach' which has been recognised in the western Forth valley (Sissons, 1966), without any suggestion of an intervening fall.

Flandrian

The climatic improvement that marked the end of the Devensian and the Loch Lomond Stadial was abrupt, with mean temperature rising by approximately 1° per decade (Coupe, 1977; Atkinson et al., 1987), This change coincided with a return of warm North Atlantic Drift waters to Scottish shores, resulting from a retreat of the oceanic polar front. The early Flandrian was characterised by adjustment to new geomorphological conditions. On land, the periglacial processes ceased, but rock slope failures and reworking by streams and debris flows, initiated during the Windermere Intel-stadial and Loch Lomond Stadial, continued to produce terraces, landslips and solifluction lobes. Offshore, major sea-level changes took place as a result of the complex interaction of glacio-isostatic rebound and eustasy. Generally sea level fell during the early and late Flandrian, butthe major transgression associated with the 'Main Postglacial Shoreline' (Plate 20) occurred in the middle Flandrian, although the exact timing of the maximum sea levels was dependent on location with respect to the centre of maximum isostatic uplift centred in the south-west Highlands.

Marine deposits

Deposits overlying the erosion surface associated with the 'Main Lateglacial Shoreline' in the Falkirk-Airth area, are considered by Browne et al. (1984), who named them the Lytham Beds, to be equivalent to the deposits of the 'Main' and 'Low' 'Buried Raised Beaches' of Sissons (1966; 1969). Where encountered in foundation hove-holes for the M876 motorway near Letham, the Letham Formation (Browne et al., 1984; 1993; Paul et al., 1995; (Table 5)) comprises up to 5 m of micaceous grey silt and sand, sandwiched between the Bothkennar Gravel and the sub-Carse Peat (see below). However, the underlying gravel is sometimes absent, and the Letham Formation rests with non-sequence on the eroded top of the Abbotsgrange Formation, for example at Grangemouth Docks.

Peat-forming vegetation grew on the emergent marine flats (Sissons, 1966; 1969; 1971b) of the 'Main' and 'Low Buried beaches'. The accumulation of' partly decayed vegetation as peat largely ended with the main Flandrian marine transgression about 8500 BP. Although the Sub-Carse Peat is widespread in the western Forth valley, it is much less well-developed in this district. The peat is typically up to 0.4 m thick, layered and of a compact, fibrous and woody texture. However, as at Flanders Moss, in the Larbert area, the peat is thick and appears to have continued to accumulate throughout this transgression.

The carse clays, or Claret Formation (Browne et al., 1984; 1993; Paul et al., 1995; (Table 5)), were laid down during the main Flandrian transgression which began about 8500 to 8150 BP and culminated at about 6500 to 6000 BP when relative sea level was at the position of the 'Main Postglacial Shoreline' (Paterson et al., 1981). The Claret Formation consists of grey, sulphide-rich, fossiliferous clayey silts and silty clays, with some silty and fine sand laminae. In the Carron valley the carse clays are interbedded with sand and gravel, for example at Larbert and Bainsford. Plant remains may be common and the deposit commonly has a fetid odour. Although usually soft, the deposit typically has a stiff, yellowish, weathered crust 1 m or so thick.

Shell middens, indicating human occupation along the former shorelines related to this transgression, are common, for example in the neighbourhood of Inveravon [NS 954 797] (Stevenson, 1948), and have furnished radiocarbon dates ranging from about 6000 to 4200 BP (Mackie, 1972).

Locally, the Claret Formation is overlain by the Grangemouth Formation (Browne et al., 1984; 1993; Paul et al., 1995; (Table 5)), which comprises soft, brownish black or grey, well-laminated silty clays and clayey silts, with many laminae and thin seams of fine sand. The beds also contain variable amounts of vegetable matter, including peaty bands, and the base of the deposit is commonly gravelly and shelly. The deposit is generally flat bedded, but locally it is steeply cross bedded and may represent the fill of intertidal channels. Fragments of Ostrea sp. from a bore at Bothkennar [NS 9142 8283], at an elevation of 1.29 m below OD, gave a radiocarbon date of 4025 BP. The faunal evidence indicates many similarities with conditions prevailing during deposition of the Claret Formation, with a continuing temperate climate and tidal flat conditions, but with shallower water and reduced marine influence as compared with the Claret Formation.

Fluvial deposits

The majority of rivers and larger streams have laid down alluvium during the Flandrian, but in many of them the accumulations are insignificant. The principal alluvial deposits are to be found in the valleys of the rivers Carron, Avon and Bonny Water, and to a lesser extent in the valleys of the Westquarter Burn, Couston Water, River Almond, Breich Water and South Calder Water.

The River Carron has created extensive terraces at up to three distinct levels, underlain by sand and gravel, produced largely by reworking of fluvioglacial deposits across which the river flowed. However, the highest of these terraces has an elevation in excess of 20 m before OD, and may therefore be pre-Flandrian in age.

Below Avonbridge, much of the valley of the Avon is incised, thus severely limiting the development of alluvium, the largest spreads of which are to be found in the vicinity of Whitecross. In the 10 km upstream from Avonbridge, the River Avon falls less than 20 m. Consequently alluvial deposits, although locally quite extensive, are predominantly fine-grained, chiefly comprising silt and commonly intimately associated with peat accumula­tion. The valley of the Bathgate Water around Whiteside [NS 970 680] and the upper reaches of the River Almond, where the gradients are also insignificant, contain similar fine-grained alluvial deposits.

Lacustrine deposits

Alluvium of lacustrine origin is not common in the district, being confined to closed, poorly drained hollows principally in areas where igneous rock has controlled the topography, for example west of Cockleroy [NS 990 745]. The deposits are similar to those described in the preceding paragraph, namely silt with lenses of sand or clay, and plant remains.

Peat

Deposits of blanket peat cover significant areas of the district, particularly to the south of Falkirk and to the west and south of Armadale and Whitburn. The total area of peat mapped during the resurvey probably accounts for between 10 and 15 per cent of the land surface of the district. Peat was formerly much more extensive, but large areas were cleared during the agricultural reclamation of moorland and the carselands along the Forth during the 18th century (Anon, 1845; Macgregor and Anderson, 1923). The sub-Carse peat has been described above.

Man-made deposits

Human modification of the landscape is widespread throughout the district. Mineral working has been the principal reason for extensive spreads of man-made deposits and disturbed ground, chiefly from the winning of coal. Bings (spoil heaps) are numerous and opencast mining of coal and fireclay has resulted in large areas of cut and fill, some of which are not now easily detectable. Other minerals which have been quarried in the district include dolerite for hard rock aggregate, sand and gravel, clay and mudstone for brickmaking, sandstone and limestone. Many of the quarry sites have been partially or completely backfilled with industrial, building or domestic waste.

Made ground also occurs in areas of former mining activity, beneath industrial sites and along the routes of major roads such as the M8, M9, M876 and A801, but is normally only a few metres thick, except beneath large tips and high embankments.

Along the margins of the Firth of Forth, extensive littoral areas have been reclaimed. Examples include the Longannet complex, Preston Island, Grangemouth Docks and Refinery (Plate 21), Kinneil Kerse and the Bo'ness foreshore (Cadell, 1913; 1925; Gostelow and Browne, 1986).

Quaternary biostratigraphy

A detailed analysis of the relationship between the lithostratigraphy and faunal assemblages of the late-Devensian and Flandrian estuarine sediments in the Grangemouth area was provided by Browne et al. (1984). They recognised seven principal lithostratigraphical subdivisions whose faunas provide evidence of a general progressive shallowing of the sea and a gradual transition from harsh arctic or subarctic temperatures to the boreal conditions now prevailing.

The lowest subdivision, the Loanhead Formation, contains a fragmented shallow-water but seaward-transported macro-fauna, restricted in both numbers and diversity. The molluscs include Retusa obtusa, Cerastoderma edule, Corbula gibba, Mytilus edulis, Nuculana pernula and Yoldiella lenticula. The microfauna include the foraminifer Elphidium clavatum and the ostracod Cytheropteron pseudomontrosiense. The palaeoenvironment suggested by the fauna is probably a deep polar sea of relatively low or variable salinity, made turbulent by calving glaciers.

In the Kinneil Kerse Formation there is an increase, especially in macrofaunal abundance and diversity, in the molluscs Hydrobia ulvae, Littorina obtusata, Retusa obtusa, Cerastoderma edule, Nuculana pernula, Yoldiella fraterna and Y. lenticula. In the microfauna the foraminifera include Ammonia batavus, Elphidium clavatum and Haynesina germanica, whilst Leptocythere spp. dominate the ostracods. Faunal evidence suggests there had been a slight, possibly fluctuating climatic amelioration since deposition of the Loanhead Formation. The mixture of estuarine or intertidal species with others more typical of deeper water suggests some tidal reworking.

The macrofauna of the Abbotsgrange Formation includes Omalogyra atomus, Skeneopsis planorbis and Abra sp., but there is a complete absence of exclusively cold-water molluscs. The microfauna includes the foraminifera Elphidium clavatum, Miliolinella subrotunda and Haynesina germanica, and the ostracod fauna decreases upwards in both diversity and abundance. Faunal interpretation involved a highly variable intertidal estuarine environment proximal to a fully marine water mass, with frigid temperatures continuing at first but later ameliorating to a more temperate climate.

Only a sparse macrofauna was obtained from the Bothkennar Gravel consisting of the cool-water molluscs Boreotrophon clathratus and Nuculana pernula, both of which could have been reworked from earlier late-Devensian deposits. No microfauna was obtained. Paul et al. (1995) interpreted the depositional environment as intertidal to shallow-water marine.

In the Letham Formation the fauna is typically dominated by Hydrobia ulvae, Retusa obtusa, Cerastoderma edule and Macoma balthica, but there are no cold-water molluscs. The fauna suggests an environment of tidal flats with varying salinity levels and a continuing temperate climate.

The most abundant molluscs in the Claret Formation includes Hydrobia ulvae, Abra sp Cerastoderma edule, Corbula gibba and Mysella bidentata. In the microfauna, the foraminifera include Ammonia batavus, Bulimina marginate, Haynesina germanica and Quinqueloculina seminulum. Ostracod faunas are of high variability and abundance. The fauna indicated a shallow, littoral, possibly intertidal, estuarine environment with proximity to a fully marine water mass, and with the temperate climate continuing to improve. Paul et al. (1992) proposed that the Claret Formation accumulated in water depths of less than 20 m.

The macrofauna of the Grangemouth Formation include the molluscs Retusa obtusa, Cerastoderma edule, Macoma balthica and Mytilus edulis. Of the microfauna, the foraminifera are dominated by Haynesina germanica, with Ammonia batavus and Elphidium williamsoni. Ostracod assemblages vary erratically in diversity and abundance but are dominated by Leptocythere spp. The fauna suggest shallow, estuarine, tidal-flat conditions of deposition, with a reduced marine influence and a temperate climate.

Chapter 11 Economic geology

The rocks and superficial deposits of the Falkirk district have been exploited for a wide variety of end uses, over several centuries. However, the extraction of minerals is now much less than at the height of the industrial revolution, and mineral working is now confined to natural and crushed aggregates, opencast mining of coal, fireclay, and mudstone for brickmaking, and stripping of peat for horticulture.

Energy sources

Coal

The majority of formerly economic coal scams occur in the Limestone Coal Formation and the Middle and Lower Coal Measures formations contained within the Central Coalfield syncline.

At least 16 named seams in the Limestone Coal Formation and more than 20 m the Coal Measures formations are known to have been worked in the district (Cameron et. al., 1989; Aitken et al., 1990). A limited number of coals in the Upper Limestone Formation and the Passage Formation have also been exploited. Deep mining ceased with the closure of the Polkemmet colliery in 1985. Coal working is now restricted to licensed opencast mines which have concentrated on scams in the Coal Measures. The largest opencast quarries in the district have been located on the outcrop of the basal Coal Measures, where 'fireclay' and 'brickclay' have been extracted in addition to coal, fbr example at Headlesscross [NS 890 575], Roughcastle [NS 850 795] and Northrigg [NS 955 668].

Oil shale

The first plant in Scotland to process oil shale was set up in Bathgate in 1851, utilising a cannel coal known as Bog-head Coal or Torbanite which occurred at the base of the Coal Measures over a small area on the Torbanchill Estate south-west of Bathgate. It gave an oil yield of 535 to 580 litres/tonne, but the deposit was exhausted within 12 years.

Oil shales belonging to the West Lothian Oil Shale Formation (formerly Upper Oil Shale Group) have been mined in the south-east of the district near its eastern boundary, between Boghall [NS 997 683] and Rusha Farm [NS 997 606]. The most extensive workings were in the Dunnet Shale, north of Addiewell [NS 99 62], and small areas have been mined for the Fells and Fraser shales. Production of oil shale ended in 1962.

Oil and gas

The potential within the Strathclyde Group of the oil shales and sandstones as source and reservoir rocks, respectively, has aroused sufficient interest m the past for the oil industry to sink exploratory wells in stumble structures in central Scotland. A bore put down through the Salsburgh Anticline gave a gas yield of 330 000 ft3/day and traces of oil, from a sandy facies below the Houston Marls (Falcon and Kent, 1960).

Coalbed methane

Potential methane extraction from coal seams in the Clackmannan Syncline has been described in Glover et al. (1993). The Coal Measures have too thin a cover and have been too extensively worked to merit serious consideration. Coalbed methane potential within Limestone Coal Formation strata, lying at depths greater than 600 m below surface, are believed to constitute the best prospect in the district.

Historically, the highest-ranked coal has come from the Denny area, where it is believed that a higher thermal gradient has been responsible for the improved coal rank. The quartz-dolerite sill has almost certainly had some influence on coal rank, but the effect of such intrusions on methane content is unknown. However, Glover et al. (1993) concluded that the overall coalbed methane potential in this area is low, with the best prospects likely to be found in the more deeply buried coal seams.

Peat

Peat covers over 10 per cent of the district, with the greatest concentrations in the country surrounding Slamannan, Kirk O'Shotts and Fauldhouse. Peat cover was formerly even greater, but considerable areas have been cleared in the process of land beneficiation, particularly during the 18th century (Anon, 1845; Macgregor and Anderson, 1923). In addition to local consumption as fuel, peat has been worked commercially at a number of localities, including Fauldhouse, Darnrig Moss [NS 86 75], Mosside Farm [NS 975 670] and Easter Inch Moss [NS 905 665], south of Bathgate. Currently, mechanical stripping of peat is taking place at Gardrum Moss [NS 890 755] (Plate 22), at two sites near Longriggend and at. Letham Moss [NS 88 86].

Bulk minerals

Hard rock aggregate

Quartz-dolerite sills have been the primary source of crushed rock aggregate in the district. At least 16 quarries of noteworthy size are known (Merritt and Elliot, 1984, Appendix D), but in 1903 only four were active. These were at Hillend [NS 823 673], Cairneyhill [NS 850 661], Duntilland [NS 845 635] and Tam's Loup [NS 885 639]. This resource is most commonly used in road construction and maintenance, either coated or uncoated. Other uses include fill, concreting aggregate, rock armour and gabions. Resources of quartz dolerite in the district are very considerable.

Sand and gravel

Resources of sand and gravel lie in a series of east-west belts and occur as glacial meltwater, raised marine and alluvial deposits (Browne, 1977; Cameron et al., 1977;McAdam, 1978). Commercial exploitation has been focused principally in the Denny-Falkirk-Polmont-Linlithgow area with some extraction between Westfield and Bathgate. Although sand and gravel deposits remain in the district, the resources are commonly either too thin, too fine grained or located where pits would he environmentally unacceptable.

The most intensive area of working lay between Denny and Falkirk, where the number of former pit sites exceeds 20. The last pit to close in this area, at Bonnyfield [NS 816 802], ceased working in 1991. Denny, Bonnybridge, Larbert, Camelon and Grahamston are mostly built on sand and gravel and have sterilised a significant resource. East of Falkirk, between Polmont and Linlithgow, sand and gravel has been worked at 20 localities, but only two are now active, at Avondale House [NS 957 788] and Avonbank [NS 961 785], Only small remnants of the Polmont Esker now survive in this area.

In the Westfield-Bathgate area, sand and gravel working is confined to one pit at North Couston [NS 953 711] (Plate 23), although in the past several other nearby deposits were worked. Sand and gravel has also been quarried in and around Bathgate, for example on the site of the golf course.

The only other deposits of glacial sand and gravel of noteworthy extent in the district, lie between Allanton and Static, but have only been worked on a minor scale. Alluvial sand and gravel deposits are of limited distribution and have only been worked in the district near Woodyett [NS 827 823] in the valley of the River Carron.

Sandstone

A number of sandstone beds in the district have heen worked for building stone, but the numerous quarries have all been inactive for many years. Sandstones suitable for freestone are poorly developed in the Lower Limestone Formation and only limited working of sandstone in the Limestone Coal Formation has occurred in the district. In the tipper Limestone Formation a sandstone up to 21 m thick (equivalent to the Bishopbriggs Sandstone of the Glasgow district) was formerly quarried at several localities. In Bo'ness, quarries existed at Maidenpark [NS 993 808] and Dealtfield [NS 988 811], the former supplying the stone the 'new' Bo'ness town hall built in 1907. Near Plean this sandstone was worked at Blackeraig Quarry at Muirmailing [NS 826 861].

Although sandstone is abundant in the Passage Formation, it is commonly too soft and coarse grained for dimension stone. However, it has been quarried at numerous localities on a small scale, fire example near East Whitburn Mains [NS 958 618], Birkhill [NS 973 701], Salsburgh [NS 825 6181 and Lochdrum [NS 818 782]. The only remaining working quarry in the Passage Formation produces silica sand at Leven Seat (see below).

In the Coal Measures, numerous sandstone horizons have been quarried in the past. Sandstone occurring above the Shotts Furnace Coal was worked near Fauldhouse at Falahill [NS 921 608] and Braehead [NS 921 607]; the latter was operating in 1923 (Macgregor and Anderson, 1923). Sandstones from other horizons were also worked at Fauldhouse, for example in Crofthead Quarry [NS 936 606] and near Stonehead [NS 935 619]. Sandstone was quarried alongside the Barbauchlaw Burn [NS 918 683]; [NS 929 691], WNW of Armadale. A sandstone below the Armadale Ball Coal, known as the Brightons Rock, was formerly quarried extensively near Brightons [NS 930 777] and Maddiston [NS 939 766], Sandstones situated above and below the Upper Drumgray Coal were formerly wrought from two large quarries adjacent to the Union Canal north-west of Glen Village [NS 872 792] ; [NS 876 792].

Silica sand

Certain sandstones of' the Passage Formation are typically soft, friable, open-textured and are composed predomiantly of quartz (Highley, 1977; MacPherson, 1986b). They have an optimum composition for moulding sand which nowadays does not require a natural hinder; artificial binders are being increasingly used in foundry work,

Although the outcrop of the Passage Formation is extensive in the district, it is commonly concealed by superficial deposits. Silica sand is produced from one quarry located at Leven Seat, where sandstone production has continued for over 70 years. The iron oxide content of the sandstone precludes its use for most types of glass manufacture ((Table 6)). It is not known whether purer sandstone, suitable for colourless glass manufacture, occurs elsewhere in the district, but glass sand from the same limitation is quarried just north of the Forth at Devilla Forest [NS 975 913].

Limestone

All the limestones which have been wrought in the district occur within the Upper and Lower Limestone formations and the uppermost part of the West Lothian Oil Shale Formation (Robertson et al., 1949). North-east of Bathgate, the East Kirkton and West Kirkton (Hurlet) limestones have both been quarried on a small scale near Limefield [NS 988 694], and the latter also at Addiewell [NS 994 024]. The overlying Petershill (Hillhouse) limestone is up to 18 m thick (MacPherson, 1986a) and has been quarried and mined almost continuously along its outcrop between Glenbare Quarry [NS 985 690] and Craigmailing [NT 094 722].

In the Upper Limestone Formation, the Calmy Limestone has been mined at Kinneil [NS 977 805] and in Carribber Glen [NS 969 752], and quarried near Leven Seat [NS 940 576]. The Castlecary Limestone was formerly mined at. Craigenbuck, near Inveravon 1959 801], near Tod's Mill [NS 969 785], in Carribber Glen, beneath Bowden Hill [NS 977 747], at Standhill [NS 968 673], near Longridge [NS 901 021] and at Leven Seat where limestone quarrying then mining lasted almost 200 years, before terminating in 1900 (Macgregor and Anderson, 1923). The Castlecary Limestone was the most extensively worked in the district, probably owing to its reputation for producing excellent lime (Geikie et. al., 1879).

Fireclay

Passage Formation strata, which include the most valuable refractory fireclays in the United Kingdom (Highley, 1982), crop ma widely around the rim of the Central Coalfield syncline, and underlie much of the district. Fireclays occur principally near the top and bottom of the Passage Formation and throughout much of the Coal Measures, although the more aluminous and refractory fireclays lie mainly below the position of the Upper Drumgray Coal (Merritt, 1985).

The Lower Fireclays of the Passage Formation, because of their high alumina content, were economically the most important (Table 6). They are thought to be over-bank deposits of a meandering river system, and are thus not true seatclays as they are not associated with coals. They were mined initially along the western outcrop of the Central Coalfield, but latterly the industry concentrated on the eastern outcrop where the quality was found to be better; a total of 12 mines were located between Birkhill and Leven Seat, with the Ballencrieff Mine [NS 964 695] being the last to close in 1985 (Merritt, 1985).

Fireclays associated with coal seams belonging to the Lower Coal Measures, have also been mined throughout the district, principally in the Armadale and Falkirk areas, but also near Allanton (Merritt, 1985).

Latterly, fireclay production has been confined to a number of opencast coal sites located within the outcrop of the Lower Coal Measures Formation where it is extracted in conjunction with coal. In 1993, for example, fireclay was being produced from quarries at South Roughcastle [NS 852 791] and Northrigg.

Brick clay and 'shale'

Various natural argillaceous materials have been used historically in the manufacture of bricks and tiles. In the past, composition bricks were made from till mixed with fireclay and colliery blaes at brickworks in the Bathgate, Denny, Falkirk, Fauldhouse and Shotts areas (Geikie et al., 1879; Macgregor and Anderson, 1923; Elliot, 1985). Clay of raised marine origin from Grahamston and glaciolacustrine silty clay from several pits in the valley of the Couston Water, were also used for brick and tile production.

Fireclay has traditionally been a raw material for bricks, as has mudstone, commonly obtained from coal bings where the carbon content is beneficial in reducing the amount of fuel required. With the decline of the coal mining industry, the availability of bing material for brick production has also diminished.

In recent years brick production in the district has migrated towards the quality end of the market. Two works at Lower Bathville [NS 942 677] in Armadale and one at Jawcraig [NS 851 752] all make facing and engineering bricks, although one also produces common bricks. Raw materials are mainly obtained from local opencast sites.

Metalliferous minerals

Ironstone

The Carron Ironworks [NS 880 825] utilized Carboniferous clayband ironstone from Bo'ness for the first time in 1760 (Cade11, 1913). Furnaces also operated at Kinneil and at Causewayend [NS 961 760] beside the Union Canal during the latter half of the 19th century, coinciding with the peak in local ironstone mining (Macgregor and Haldane, 1933).

Blackband and clayband ironstones were formerly mined extensively throughout the district (Geikie et al, 1879), but the principal centres were around Denny, Bo'ness and Armadale (Forsyth et al., 1982). Bedded ironstones were the main source of iron ore during the industrial revolution in Scotland, but production declined rapidly around the turn of the century.

Hilderston Silver Mine

The discovery of silver at Hilderston [NS 990 715] in 1606 resulted in intermittent mining activity for silver, lead and nickel between 1607 and 1898 (Cadell, 1925; Stephenson, 1983a; b). The silver lode, which unusually included native silver, was exhausted within a few years and the presence of nickel ore in the vein mineralisation was not recognised until about 1870 (Aitken, 1893). The mineral suite included niccolite, bravoite, annabergite, erythrite, native silver and galena, in a gangue comprising baryte, calcite and dolomite. Minor stratabound lead-zinc mineralisation has also been discovered in the same neighbourhood in the lower, argillaceous part of the Petershill Limestone (Stephenson, 1983b; Smith et al., 1994).

Groundwater resources

The presence of bedrock aquifers with poor to moderate hydraulic characteristics and, in modern times, an adequate surface water supply, has meant that only restricted groundwater development has taken place in the district. Boreholes have been used for abstracting groundwater for industrial as well as for public supply from the Denny, Falkirk and Linlithgow areas, principally from the Upper Limestone and Passage formations. In the southern part of the district, however, a greater volume of groundwater was pumped, but only because of the necessity to keep coal mines dewatered.

The rock units with the most favourable hydraulic characteristics are the Upper Limestone and Passage formations. The presence within them of a high proportion of sandstone units allows for the storage and transmission of groundwater in moderate quantities.

The Passage Formation has been investigated at Grangemouth, an area containing the thickest sequence of this unit. Here, a borehole 147 m in depth yielded 4.5 litres/ second of groundwater. This water proved to be of very high hardness which resulted in the abandonment of the borehole. Farther south, near Fauldhouse, a 330 m-deep borehole produces 5 l/s of water of generally good quality, but with a very high content of iron. The widespread area of outcrop of this formation and the soft and friable nature of the sandstone indicate that there is potential for further groundwater development. There is the likelihood, however, that poor water quality will be the most significant limiting factor in development.

The Upper Limestone Formation contains several thick sandstone units, particularly around Denny. Here, a number of boreholes were drilled to supply water to a paper mill. Two of these boreholes had excellent yields of 26 and 301/s, although others nearby were in the range 1 to 3 1/s. These demonstrate the variable nature of the aquifer even over small distances. There are no records of wells having been drilled into this formation in other parts of thedistrict although potential may exist for moderate yields from boreholes wherever the upper, sandier part of the formation occurs.

Average yields from individual boreholes of between 1 and 3 l/s have been recorded from boreholes in other parts of the Carboniferous sequence. For a period, Linlithgow was supplied with potable water from two boreholes which provided 1.2 and 1.8 l/s from both the Limestone Coal Formation and superficial deposits. Present-day use includes a number of boreholes drilled into Lower Carboniferous sediments and volcanic rocks for farm and domestic supply in the Bathgate Hills. However, poor water quality is a major restricting factor in groundwater usage in certain areas. High concentrations of sulphate and iron from Coal Measures groundwater mean that, in general, it cannot he considered for either potable or most industrial uses. Additionally, impermeable mudstones interbedded with sandstone units within the Coal Measures restrict movement of groundwater both vertically and horizontally. Data from work in the southern part of the district suggest that hydraulic conductivity within sandstone beds is of the order of 10-2 m/day.

Groundwater from Coal Measures and Limestone Coal Formation strata was, for many years, pumped from coal mines purely for dewatering purposes. Many mines had to pump water continuously, the amounts of water normally pumped varying from 30 to 55 1/s. A small number of pits in the Shotts and Harthill area were much wetter with up to 105 l/s pumped. All pits and mines are now abandoned, but a large amount of poor quality water remains in storage within old workings. There are places where the workings have been used as a receptacle for the disposal of liquors and oils, many of which were toxic at the time of emplacement. There is therefore a likelihood, particularly in the Fauldhouse area, that any abstraction of mine water will include these toxic wastes.

Water-bearing superficial deposits are not widespread. The buried channels present near Falkirk and Linlithgow contain the greatest storage of groundwater, but these are not laterally extensive and have limited potential as aquifers.

Information sources

Further geological information held by the British Geological Survey relevant to the Falkirk district is listed below. It includes published material in the form of maps, memoirs and reports and unpublished maps and reports. Also included are other sources of data held by BGS in a number of collections, including borehole records, mine plans, fossils, rock samples, thin sections, hydrogeological data and photographs. Searches of indexes to some of the collections can be made on the Geoscience Index System in BGS libraries. This is a developing computer-based system which carries out searches of indexes to collections and digital databases for specified geographical areas. It is based on a geographical information system linked to a relational database management sytem. Results of the searches are displayed on maps on the screen. At the present time (1995) the datasets are limited and not all are complete. The indexes which are available are listed below:

Details of geological information available from the British Geological Survey can be accessed on the BGS Web Home Page at: http://www.bgs.ac.uk

BGS Maps

Geology maps

The original geological survey was carried out at a scale of six inches to one mile scale by A Geikie, J Geikie and B N Peach and was published at a scale of one inch to one mile in 1875. The district was resurveyed between 1904 and 1924 at the six-inch scale by E M Anderson, F B Bailey, T O Bosworth, R G Carruthers, C T Clough, C B Crampton, G W Grabham, L W Hinxman, B Lightfoot, M Macgregor, H B Maufe, J S G Wilson and W B Wright and published at the one-inch scale in Solid and Drift editions in 1924. Copies of the fair-drawn maps of these earlier surveys may be consulted at the BGS library in Edinburgh.

The maps at six-inch or 1:10 000 scale covering wholly or in part in the 1:50 000 scale Sheet 31E are listed below, together with the surveyors' initials and the dates of the survey. The surveyors were: A M Aitken, M A E Browne, J I Chisholm, J M Dean, I H Forsyth, F H Francis, S M Jones, Knox, A D McAdam, S K Monro, I B Paterson, W A Read, D L Ross, R A Smith, D Stephenson and W Tulloch.

The maps are not published hut are available for consultation in the Library, British Geological Survey, Murchison House, Edinburgh, EH9 3LA, and also at Keyworth and the London Information Office, in the Natural History Museum, South Kensington, London. Dyeline copies may be purchased from the Sales Desk.

NS 85 NW

IBP

1982–1983

NS 85 NE

JIC, IBP

1982–1983

NS 86 NW

AMA, IHF, SMJ

1977–1985, 1989–1991

NS 86 NE

JMD, IHF, SMJ, RAS

1971, 1979–1981, 1988, 1989

NS 86 SW

AMA, IHF, SMJ

1978–1984, 1989–1990

NS 86 SE

JIC, JMD, IHF, SMJ, RAS

1969–1988, 1989

NS 87 NW

AMA, IHF, SMJ

1979–1981, 1989–1992

NS 87 NE

MAEB, WAR, DI,R

1969, 1979–1981, 1989

NS 87 SW

AMA, IHF, SMJ

1978–1984, 1989–1990

NS 87 SE

SMJ RAS

1979–1981, 1991

NS 88 NW

WAR

1952–1954

NS 88 NE

WAR

1952–1953

NS 88 SW

AMA, MAEB, IHF, WAR

1952–1954, 1979, 1981, 1989–1992

NS 88 SE

MAEB, WAR

1958–1959, 1981–1982, 1988

NS 95 NW

JIC

1968–1969

NS 95 NE

JIC

1968–1969

NS 96 NW

AMA, IHE

1987

NS 96 NE

AMA, IHF, DS

1981, 1987–1988

NS 96 SW

JIC DLR

1968–1969, 1987

NS 96 SE

JIC, DLR

1968–1969, 1987

NS 97 NW

MAEB, WAR, DER

1969, 1979–1981, 1989

NS 97 NE

AMA, MAEB, WAR

1964–1969, 1979–1981, 1988–1989

NS 97 SW

AMA, IHF

1981, 1987–1991

NS 97 SE

AMA, IHF, WAR, DS

1965–1981, 1987–1988

NS 98 NW

EHF, WAR

1951–1953

NS 98 NE

EHF

1951

NS 98 SW

MAEB, WAR

1958, 1981–1982, 1988

NS 98 SE

AMA, MAEB, WAR

1969, 1979–1981, 1988–1989

NT 06 NW

DER, WT

1957, 1991

NT 07 NW

RAS

1990

NT 07 SW

RAS

1990–1991

NT 08 NW

EHF, JR

1950, 1964–1965

NT 08 SW

ADM

1989

Applied geology maps

Sets of thematic maps prepared for land-use planning purposes are also available in parts of the district. These normally accompany a technical report but they can be obtained separately. The location of the Falkirk district in relation to the maps prepared for land-use planning is shown on (Figure 29).

Engineering geology maps

Geophysical maps

Geochemical atlases

Hydrogeological map

BGS books

General geology

Economic geology: coal, ironstone and oil shale

Land-use planning

Biostratigraphy

Bulk minerals

Hydrogeology

Geophysics

Engineering geology

Geothermal potential

Metalliferous minerals

Documentary collections

Borehole record collection

BGS holds collections of records of boreholes which can be consulted at BGS, Edinburgh, where copies of most records may be purchased. For the Falkirk district the collection consists of the sites and logs of about 5200 boreholes. Index information, which includes site references, for these bores has been digitised. The logs are either handwritten or typed and many of the older records are drillers logs.

Site exploration reports

This collection consists of site exploration reports carried out to investigate foundation conditions prior to construction. There is a digital index and the reports themselves are held on microfiche. For the Falkirk district there are presently (1995) about 680 reports.

Mine plans

BGS maintains a collection of plans of underground mines for minerals other than coal and oil shale. Plans held which fall within the district include the following:

Mineral worked

No. of plans

Fireclay

66

Limestone

11

Silver, lead, nickel

4

Ironstone clayband

12

Ironstone slatyband

12

Ironstone blackband

36

Coal abandonment plans are held by The Coal Authority, Mining Records Department, Bretby Business Park, Ashby Road, Burton-on-Trent, Staffs, DE15 OQD.

Material collections

Geological Survey photographs

About 70 photographs illustrating aspects of the geology of the Falkirk district are deposited for reference in the libraries at BGS, Murchison House, West Mains Road, Edinburgh EH9 3LA and BGS, Keyworth, Nottingham NG12 5GG; and in the BGS Information Office, Natural History Museum Earth Galleries, Exhibition Road, London SW7 2DE.

The photographs were taken at various times since 1951, but most are later than 1976. The photographs depict details of the various rocks and sediments exposed either naturally or in excavations and also some general views. A list of titles can be supplied on request. The photographs can be supplied as black and white or colour prints and 2 X 2 colour transparencies, at a fixed tariff.

Petrological collections

The petrological collections for the Falkirk district consist of several hundred hand specimens and thin sections. Most samples and thin sections are of the igneous rocks in the area. The sedimentary rocks are poorly represented. The collections are indexed on the basis of the one-inch geological maps, but much of the early part of the collection cannot at the moment be searched by National Grid reference.

Bore core collection

Samples have been collected from core taken from boreholes. At present (1993) there are over 1400 samples (hand specimens) from over 100 bores which are registered in the borehole collection.

Palaeontological collections

The collections of biostratigraphical specimens are taken from surface and temporary exposures, and from boreholes throughout the Falkirk district. The collections are working collections and are used for reference. They are not at present on a computer database.

References

Most of the references listed below are held in the libraries of the British Geological Survey at Murchison House, Edinburgh and at Keyworth, Nottingham. Copies of the references can be purchased from the Keyworth office subject to the current copyright legislation.

ABSALOM, R G, and HENDERSON, S M K. 1947. A tooth of Elephas primigenius from Headswood, Larbert, Stirlingshire. Geological Magazine, Vol. 84, 181–184.

AITKEN, H. 1893. The Hilderstone silver mine, near Linlithgow. Transactions of the Federated Institution of Mining Engineers, Vol. 6, 193–198.

AITKEN, A M, BROWNE, M A E, ROSS, D L, and SMITH, R A. 1990. Geology for land use planning: Falkirk-Grangemouth. British Geological Survey Technical Report, WA/90/56.

ANDERSON, E M. 1951. The dynamics of faulting (2nd edition). (Edinburgh: Oliver and Boyd.)

ANDERSON, F W. 1963. The Geological Survey bore at Rashiehill, Stirlingshire (1951). Bulletin of the Geological Survey of Great Britain, No. 20, 43–106.

ANDREWS, J T, and DUGDALE, R E. 1970. Age prediction of isostatic strandlines based on their gradients. Geological Society of America Bulletin, Vol. 81, 3769–3771.

ANON. 1845. The new statistical account of Scotland.

ATKINSON, T C, BRIFFA, K R, and COOPS, G R. 1987. Seasonal temperatures in Britain during the last 22,000 years, reconstructed using beetle remains. Nature, London, Vol. 325, 587–593.

BAMFORD, D, NUNN, K, PRODEHL, C, and JACOB, B. 1978. LISPB-IV Crustal structure of northern Britain. Geophysical Journal of the Royal Astronomical Society, Vol. 54, 43–60.

BAMFORD, D. 1979. Seismic constraints on the deep geology of the Caledonides of northern Britain. 93–96 in The Caledonides of the British Isles - reviewed. HARRIS, A C, HOLLAND, C H, and LEAKE, B E (editors). Special Publication of the Geological Society of London, No. 8.

BARTON, P J 1992. LISPB revisited: a new look under the Caledonides of northern Britain. Geophysical Journal International, Vol. 110, 371–391.

BLUCK, B J. 1984. Pre-Carboniferous history of the Midland Valley of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 75, 275–295.

BOTT, M H P, SWINBURNE, P M, and LONG, R E. 1984. Deep structure and origin of the Northumberland and Stainmore troughs. Proceedings of the Yorkshire Geological Society, Vol. 44, 479–495.

BOULTON, G S, PEACOCK, J D, and SUTHERLAND, D G. 1991. Quaternary. 503–543 in Geology of Scotland (3rd edition). CRAIG, G Y (editor). (London: The Geological Society.)

BRAND, P J 1977. The fauna and distribution of the Queenslie Marine Band (Westphalian) in Scotland. Report of the Institute of Geological Sciences, No. 77/18.

BROWNE, M A E. 1977. Sand and gravel resources of the Central Region, Scotland. Report of the Institute of Geological Sciences, No. 77/9.

BROWNE, M A E. 1986. The classification of the Lower Carboniferous in Fife and Lothian. 422–425 in Sedimentology and hydrocarbon potential of the Dinan tian oil-shales of northern Britain. Report of a meeting sponsored by the British Sedimentological Research Group. Scottish Journal of Geology, Vol. 22.

BROWNE, M A E, GRAHAM, D K, and GREGORY, D M. 1984. Quaternary estuarine deposits in the Grangemouth area, Scotland. Report of the British Geological Survey, Vol. 16, No. 3.

BROWNE, M A E, HARGREAVES, R L, and SMITH, I F. 1985. The Upper Palaeozoic basins of the Midland Valley of Scotland. Investigation of the geothermal potential of the UK (Keyworth, Nottingham: British Geological Survey.)

BROWNE, M A E, and McMILLAN, A A. 1989. Quaternary geology of the Clyde Valley. British Geological Survey Research Report, SA/89/1.

BROWNE, M A E, MENDUM, J R, and MONRO, S K. 1993. Geology. 1–17 in Central Scotland: land-wildlife-people. CORBETT, L, and DIX, N J (editors). (Stirling: Forth Naturalist and Historian, Stirling University.)

BROWNE, M A E, DEAN, M T, HALL, I H S, MCADAM, A D, and MONRO, S K. 1995. A review of the lithostratigraphy of the Carboniferous rocks of the Midland Valley of Scotland (Draft Interim Version - 23/3/95). British Geological Survey Technical Report, No. WA/95/25R.

BURKE, M J 1969. The Forth Valley: an ice-moulded lowland. Transactions of the Institute of British Geographers, Vol. 48, 51–59.

CADELL, H M. 1883. Notice of the surface geology of the estuary of the Forth round Borrowstounness. Transactions of the Edinburgh Geological Society, Vol. 4, 2–33.

CADELL, H M. 1913. The story of the Forth. (Glasgow: James Maclehose and Sons.)

CADELL, H M. 1925. The rocks of West Lothian. (Edinburgh: Oliver and Boyd.)

CALVER, M A. 1956. Die stratigraphische Verbreitung der nichtmarinen Muscheln in den penninischen Kohlenfeldern Englands. [The stratigraphic distribution of the non-marine mussels in the Pennine coalfield of England.] . Leaven?* der Deutschen Geologischen Gesellschaft, Vol. 107, 26–39. [In German.]

CALVER, M A. 1969. Westphalian of Britain. Compte Rendu 6me Congres International de Stratigraphie et de Geologie du. Carbonifere, Sheffield, 1967, Vol. 1, 233–254.

CAMERON, I B, AITKEN, A M, and Ross, D L. 1989. Geology for land use planning: Bathgate. British Geological Survey Technical Report, WA/89/19.

CAMERON, I B, and CHISHOLM J I. 1989. Solid geology of 1:10 000 sheet NS 96 SE. British Geological Survey Technical Report, WA/89/17.

CAMERON, I B, and CHISHOLM J I. 1990. Solid geology of 1:10 000 sheet NS 96 SW. British Geological Survey Technical Report, WA/90/58.

CAMERON, I B, and STEPHENSON, D. 1985. British regional geology: the Midland Valley of Scotland (3rd edition). (London: HMSO for British Geological Survey.)

CARRUTHERS, R G, CALDWELL, W, BAILEY, E M, and CONACHER, H R J. 1927. The oil-shales of the Lothians (3rd edition). Memoir of the Geological Surrey, Scotland.

CHISHOLM J I. 1971. The stratigraphy of the post-glacial marine transgression in N E Fife. Bulletin of the Geological Survey of Great Britain, Vol. 37, 91–107.

CHISHOLM J I, McADAM, A D, and BRAND, P J. 1989. Lithostratigraphical classification of Upper Devonian and Lower Carboniferous rocks in the Lothians. British Geological Survey Technical Report, WA/89/26.

CLOUGH, C T, HINXMAN, L W, WRIGHT, W B, ANDERSON, E M, and CARRUTHERS, R G. 1916. Economic geology of the Central Coalfield of Scotland, Area V, Glasgow East, Chryston, Glenboig and Airdrie. Memoir of the Geological Survey, Scotland.

CONWAY, A, DENTITH, M C, DOODY, J J, and HALL, J. 1987. Preliminary interpretation of upper crustal structure across the Midland Valley of Scotland from two east-west seismic refraction profiles. Journal of the Geological Society of London, Vol. 144, 865–870.

COOPE, G R. 1977. Fossil coleopteran assemblages as sensitive indicators of climatic changes during the Devensian (Last) cold stage. Philosophical Transactions of the Royal Society of London, Vol. B280, 313–340.

CROLL, J. 1870. On two river channels buried under drift, belonging to a period when the land stood several hundred feet higher than at present. Transactions of the Edinburgh Geological Society, Vol. 1, 330–345.

CURRIE, F D. 1954. Scottish Carboniferous goniatites. Transactions of the Royal Society of Edinburgh, Vol. 62, 527–602.

DAVIDSON, K A S, SOLA, M, POWELL, D W, and HALL, J 1984. Geophysical model for the Midland Valley of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 75, 175–181.

DAVIES, J H, and TRUEMAN, A E. 1927. A revision of the non-marine lamellibranchs of the Coal Measures, and a discussion of their zonal significance. Quarterly Journal of the Geological Society of London, Vol. 83, 210–259.

DAY, T C. 1932. Chemical analyses of white trap from Dalmeny, Granton, Weak Law, and North Berwick. Transactions of the Edinburgh Geological Society, Vol. 12, 189–194.

DE SOUZA, H A F. 1979. The geochronology of the Scottish Carboniferous volcanism. Unpublished PhD thesis, University of Edinburgh.

DEAN, M T. 1987. Carboniferous conodonts from the Lower and Upper Limestone Groups of the Scottish Midland Valley. Unpublished MPhil thesis, University of Nottingham.

DENTITH, M C, DOODY, J J, HALL J, and FLEMING, M. 1986. MAVIS: Upper crustal seismic studies in the Midland Valley of Scotland [Abstract]. Geophysical Journal of the Royal Astronomical Society, Vol. 85, 268.

DENTLIH, M C, and HALL, J. 1989. MAVIS - an upper crustal seismic refraction experiment in the Midland Valley of Scotland. Geophysical Journal International, Vol. 99, 627–643.

DENTITH, M C, and HALL, J. 1990. MAVIS: geophysical constraints on the structure of the Carboniferous basin of West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 81, 117–126.

DEWEY, J F. 1982. Plate tectonics and the evolution of the British Isles. Journal of the Geological Society of London, Vol. 139, 371–412.

DINHAM, C H, and HALDANE, D. 1932. The economic geology of the Stirling and Clackmannan coalfield. Memoir of the Geological Survey, Scotland.

ELLIOT, R W. 1985. Central Scotland mineral portfolio: resources of clay and mudstone for brickmaking. Open-file Report of the British Geological Survey.

EVANS, C J, KIMBELL, G S, and ROLLIN, K E. 1988. Hot dry rock potential in 'urban areas. Investigation of the geothermal potential of the UK. (Keyworth, Nottingham: British Geological Survey.)

FALCON, N L, and KENT, P E. 1960. Geological results of petroleum exploration in Britain 1945–1957. Memoir of the Geological Society of London, No. 2.

FALCONER, I D. 1906. The igneous geology of the Bathgate and Linlithgow Hills. Part 2. Petrography. Transactions of the Royal Society of Edinburgh, Vol. 45, 133–150.

FITCH, F J, MILLER, J A, and WILLIAMS, S C. 1970. Isotopic ages of British Carboniferous rocks. Compte Rendu 6e Congres International de Stratigraphie et de Geologie du Carbonifere, Sheffield 1967, Vol. 2, 771–790.

FORSYTH, I H. 1980. The Lingula bands in the upper part of the Limestone Coal Group (E1 Stage of the Namurian) in the Glasgow district. Report of the Institute of Geological Sciences, No. 79/16.

FORSYTH, I H. 1988a. Solid geology of sheet NS 86 NE. British Geological Survey Technical Report, WA/88/28.

FORSYTH, I H. 1988b. Solid geology of sheet NS 86 SE. British Geological Survey Technical Report, WA/88/29.

FORSYTH, I H. 1990a. Solid geology of 1:10 000 sheet NS 96 NE. British Geological Survey Technical Report, WA/90/55.

FORSYTH, I H. 1990b. Solid geology of 1:10 000 sheet NS 97 SE. British Geological Survey Technical Report, WA/90/54.

FORSYTH, I H. 1990c. Solid geology of 1:10 000 sheet NS 97 SW. British Geological Survey Technical Report, WA/90/34.

FORSYTH, I H. 1990d. Solid geology of sheet NS 96 NW. British Geological Survey Technical Report, WA/90/32.

FORSYTH, I H., and BRAND, P J. 1986. Stratigraphy and stratigraphical palaeontology of Westphalian B and C in the Central Coalfield of Scotland. Report of the British Geological Survey, Vol. 18, No. 4.

FORSYTH, I H, BROWNE, M A E, and JONES, S M. 1982. Planning for development: Falkirk and Grangemouth Project. Report of the Institute of Geological Sciences, No. NL 82/3.

FORSYTH, I H, and Cinsuotmi I. 1977. The geology of East Fife. Memoir-of the Geological Survey of Great Britain, Sheets 41 and part of 49 (Scotland).

FORSYTH, I H, HALL, I H S, and MCMILLAN, A A. 1996. Geology of the Airdrie district. Memoir of the British Geological Survey, Sheets 31W (Scotland).

FRANCIS, E H. 1956. The economic geology of the Stirling and Clackmannan coalfield, Scotland: area north of the River Forth. Coalfield Paper of the Geological Survey of Great Britain, No. 1.

FRANCIS, E H. 1982. Magma and sediment - 1. Emplacement mechanism of late Carboniferous tholeiite sills in northern Britain. Journal of the Geological Society of London, Vol. 139, 1–20.

FRANCIS, E H. 1991. Carboniferous. 347–392 in Geology of Scotland (3rd edition). CRAIG, G Y (editor). (London: The Geological Society.)

FRANCIS, E H, FORSYTH, I H. READ, W A, and ARMSTRONG, M. 1970. The geology of the Stirling district. Memoir of the Geological Survey of Great Britain, Sheet 39 (Scotland).

FRANCIS, E H, and WALKER, B H. 1987. Emplacement of alkali-dolerite sills relative to extrusive volcanism and sedimentary basins in the Carboniferous of Fife, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 77, 309–323.

GEIKIE., A. 1863. On the phenomena of the glacial drift of Scotland. Transactions of the Geological Society of Glasgow, Vol. 1, Pt 2, 1–190.

GEIKIE, A, PEACH, B N, and GEIKIE, J. 1879. Explanation of Sheet 31. Memoir of the Geological Survey, Scotland.

GEORGE, T N. 1974. The geomorphology of the Stirling Region. 30–46 in The Stirling Region. Timms, D (editor). (Stirling: The University of Stirling.)

GEORGE, T N, and 6 others. 1976. A correlation of Dinantian rocks in the British Isles. Special Report of the Geological Society of London, No. 7.

GIBBS, A. 1987. Development of extension and mixed-mode sedimentary basins. 19–33 in Continental extensional tectonics. COWARD, M P, DEWEY, J F, and HANCOCK, P L (editors). Special Publication of the Geological Society of London , No. 28.

GIBBS, A D. 1989. Stuctural styles in basin formation. 81–93 in Extensional tectonics and stratigraphy of North Atlantic margins. TANKARD, AJ, and BALKWILL, H R (editors). American Association of Petroleum Geologists Memoir, No. 46.

GLOVER, B W, HOLLOWAY, S, and YOUNG, S R. 1993. An evaluation of coalbed methane potential in Great Britain. British Geological Survey Technical Report, WA/93/24.

GOSTELOW, T P, and BROWNE, M A E. 1986. Engineering geology of the upper Forth Estuary. Report of the British Geological Survey, Vol. 16, No. 8.

GREGORY, J W. 1913. The Polmont kame and on the classification of Scottish kames. Transactions of the Geological Society of Glasgow, Vol. 14, 199–218.

GUNN, P J. 1975. Interpretation of the Bathgate magnetic anomaly, Midland Valley, Scotland. Scottish Journal of Geology, Vol. 11, 263–266.

HALL, S J. 1815. On the revolutions of the Earth's surface. Transactions of the Royal Society of Edinburgh, Vol. 7, 139–211.

HALL, J. 1971. A preliminary seismic survey adjacent to the Rashiehill borehole near Slamannan, Stirlingshire. Scottish Journal of Geology, Vol. 7, 170–174.

HALL, J. 1974. A seismic reflection survey of the Clyde Plateau Lavas in North Ayrshire and Renfrewshire. Scottish Journal of Geology, Vol. 9, 253–279.

HALL, J, and 5 others. 1983. Seismological evidence for shallow crystalline basement in the Southern Uplands of Scotland. Nature, London, Vol. 305, 418–420.

HASZELDINE, R S. 1984. Carboniferous North Atlantic palaeogeography: stratigraphic evidence for rifting, not megashear or subduction. Geological Magazine, Vol. 121, 443–463.

HASZELDINE, R S. 1988. Crustal lineaments in the British Isles: their relationship to Carboniferous basins. 53–68 m Sedimentation in a synorogenic basin complex: the Upper Carboniferous of northwest Europe. BESLEY, B M, and KELLING, G (editors). (Glasgow: Blackie and Son.)

HIGGINS, A C. 1985. The Carboniferous System: part 2 conodonts of the Silesian Subsystem from Great Britain and Ireland. 210–227 in A stratigraphic index of conodonts. HIGGINS, A C, and AUSTIN, R L (editors). (Chichester: Ellis Horwood Limited.)

HIGHLEY D E (compiler). 1977. Silica. Mineral Dossier Mineral Resources Consultative Committee, No. 18.

HIGHLEY D E (compiler). 1982. Fireclay. Mineral Dossier Mineral Resources Consultative Committee, No. 24.

HINXMAN, L W, CRAMPTON, C B, ANDERSON, E M, and MACGREGOR, M. 1917. The economic geology of the Central Coalfield of Scotland, Area II, Denny and Plean, Banknock, Carron and Grangemouth, Cumbernauld, Castlecary and Bonnybridge, Falkirk and Slamannan. Memoir the Geological Survey, Scotland.

HOWELL, H H, and GEIKIE, A. 1861. The geology of the neighbourhood of Edinburgh (1st edition). Memoir of the Geological Survey of Great Britain.

HUTTON, A N. 1965. Foraminifera of the Upper Limestone Group of the Scottish Carboniferous. Unpublished PhD thesis, University of Glasgow.

HUTTON, D H W. 1987. Strike-slip terranes and a model for the evolution of the British and Irish Caledonides. Geological Magazine, Vol. 124, 405–425.

JAMESON, J. 1987. Carbonate sedimentation on a mid-basin high: the Petershill Formation, Midland Valley of Scotland. 309–327 in European Dinantian environments. (Geological Journal Special Issue No.12). MILLER, J, ADAMS, A E, and WRIGHT, V P (editors). (Chichester: John Wiley and Sons Ltd.)

JARDINE, W G, and 5 others. 1988. A late Middle Devensian interstadial site at Sourlie, near Irvine, Strathclyde. Scottish Journal of Geology, Vol. 24, 288–295.

KENNEDY, W Q. 1944. Transcurrent movement exemplified by a fault in the West Lothian oil-shale field. Transactions of the Geological Society of Glasgow, Vol. 20, 287–290.

LEEDER, M R. 1982. Upper Palaeozoic basins of the British Isles - Caledonian inheritance versus Hercynian plate marginal processes. Journal of the Geological Society of London, Vol. 139, 479–491.

LEEDER, M R. 1988. Recent developments in Carboniferous geology: a critical review with implications for the British Isles and NW Europe. Proceedings of the Geologists' Association, Vol. 99, 73–100.

LEEDER, M R, and McMAHON, A H. 1988. Upper Carboniferous (Silesian) basin subsidence in northern Britain. 43–52 in Sedimentation in a synorogenic basin complex: the Upper Carboniferous of northwest Europe. BESLEY, B M, and KELLING, G (editors). (Glasgow and London: Blackie and Son.)

LOFTUS, G W F, and GREENSMITH, J T. 1988. The lacustrine Burdiehouse Limestone Formation - a key to the deposition of the Dinantian oil shales of Scotland. 219–234 in Lacustrine petroleum source rocks. FLEET, AJ, KELTS, K, and TALBOT, M R (editors). Special Publication of the Geological Society of London, No. 40.

LUMSDEN, G I, and WILSON, R B. 1979. Stratigraphical classification of the Carboniferous succession of central Scotland. Compte Rendu 8e Congres International de Stratigraphie et de Geologic du Carbonifere, Moscow 1975, Vol. 2, 27–36.

MACDONALD, R. 1975. Petrochemistry of the early Carboniferous (Dinantian) lavas of Scotland. Scottish Journal of Geology, Vol. 11, 269–314.

MACDONALD, R. 1980. Trace element evidence for mantle heterogeneity beneath the Scottish Midland Valley in the Carboniferous and Permian. Philosophical Transactions of the Royal Society of London, Vol. 280, 111–123.

MACDONALD, R, GOTTFRIED, D, FARRINGTON, M J, BROWN, F W, and SKINNER, N G. 1981. Geochemistry of a continental tholeiite suite: late Palaeozoic quartz dolerite dykes of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 72, 57–74.

MACDONALD, R, THOMAS, J E, and RIZZELLO, S A. 1977. Variations in basalt chemistry with time in the Midland Valley province during the Carboniferous and Permian. Scottish Journal of Geology, Vol. 13, 11–22.

MACGREGOR, A G. 1928. The classification of Scottish Carboniferous olivine-basalts and mugearites. Transactions of the Geological Society of Glasgow, Vol. 18, 324–360.

MACGREGOR, A G. 1960. Divisions of the Carboniferous on Geological Survey Scottish maps. Bulletin of the Geological Survey of Great Britain, No. 16, 127–130.

MACGREGOR, M, and ANDERSON, E M. 1923. The economic geology of the Central Coalfield of Scotland, area VI, Bathgate, Wilsontown and Shotts, with Braehead, Fauldhouse, Armadale and Harthill. Memoir of the Geological Survey, Scotland.

MACGREGOR, M, and HALDANE, D. 1933. The economic geology of the Central Coalfield, area III, Bo'ness and Linlithgow. Memoir of the Geological Survey, Scotland.

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. Transactions of the Institution of Mining Engineers, Vol. 89, 115–130.

MACKIE, E W. 1972. Radiocarbon dates for two Mesolithic shell heaps and a Neolithic axe factory in Scotland. Proceedings of the Prehistoric Society, Vol. 38, 412–416.

MACPHERSON, K A T. 1986a. Central Scotland mineral portfolio: limestone resources. Open-file Report of the British Geological Survey.

MACPHERSON, K A T. 1986b. Central Scotland mineral portfolio: special sand resources. Open-file Report of the British Geological Survey.

McADAM, A D, SMITH, R A, and ROSS, D L. 1993. Geology for land use planning: Livingston. British Geological Survey Technical Report, WA/92/37.

MCGILL, R A R, HALL, A J, BRAITHWAITE, C J R, FALLICK, A E, and ROLFE, W D I. 1990. Petrography and geochemistry of a Lower Carboniferous lacustrine hot-spring deposit, East Kirkton, Bathgate, Scotland. Proceedings of the 12th New Zealand Geothermal Workshop, 203–208.

McGILL, R A R, HALL, A J, FALLICK, A F, and BOYCE, A J. 1994. The palaeoenvironment of East Kirkton, West Lothian, Scotland: stable isotope evidence from silicates and sulphides. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 223–237.

MERRITT, J W. 1985. Central Scotland mineral portfolio: fireclay resources. Open-file Report of the British Geological Survey.

MERRITT, J W, and ELLIOT, R W. 1984. Central Scotland mineral portfolio: hard rock aggregate resources. Open-file Report of the British Geological Survey.

MILLER, J A, and BROWN, P E. 1965. Potassium-argon age studies in Scotland. Geological Magazine, Vol. 102, 106–134.

MILTON, J J W. 1972. A palaeomagnetic study of Permian and Carboniferous igneous rocks from the Midland Valley of Scotland. Unpublished MSc thesis, University of Newcastle on Tyne.

MITCHELL, G H, and MYKURA, W. 1962. The geology of the neighbourhood of Edinburgh (3rd edition). Memoir of the Geological Survey, Scotland, Sheets 32.

MONRO, S K, CAMERON, I B, and HALL, I H S. 1991. Geology for land use planning: Stirling. British Geological Survey Technical Report, WA/91/25.

MUIR, R O, 1963. Petrography and provenance of the Millstone Grit of Central Scotland. Transactions of the Edinburgh Geological Society, Vol. 19, 439–485.

MUIR, R O, and WALTON, E K. 1957. The East Kirkton Limestone. Transactions of the Geological Society of Glasgow, Vol. 22, 157–168.

MYKURA, W. 1965. The age of the lower part of the New Red Sandstone of south-west Scotland. Scottish Journal of Geology, Vol. 1, 9–18.

NEVES, R, GUEINN, K J, CLAYTON, G, IOANNIDES, N, and NEVILLE, R S W. 1972. A scheme of miospore zones for the British Dinantian. Compte Rendu 7me Congres International de Stratigraphie et de Geologic du Carbonifere, Krefeld, 1971, Vol. 1, 347–353.

NEVES, R, READ, W A, and WILSON, R B. 1965. Note on recent spore and goniatite evidence from the Passage Group, of the Scottish Upper Carboniferous succession. Scottish Journal of Geology, Vol. 1, 185–188.

NEVES, R, and 5 others. 1973. Palynological correlations within the Lower Carboniferous of Scotland and northern England. Transactions of the Royal Society of Edinburgh, Vol. 69, 23–70.

OWENS, B, and 5 others. 1977. Palynological division of the Namurian of northern England and Scotland. Proceedings of the Yorkshire Geological Society, Vol. 41, 381–398.

PALMER, J A, PERRY, S P G, and TARLING, D H. 1985. Carboniferous magnetostratigraphy. Journal of the Geological Society of London, Vol. 142, 945–955.

PARNELL, J. 1988. Lacustrine petroleum source rocks in the Dinantian Oil Shale Group: a review. 235–246 in Lacustrine petroleum source rocks. FLEET, A J, KELTS, K, and TALBOT, M R (editors). Special Publication of the Geological Society of London, No. 40.

PATERSON, I B, ARMSTRONG, M, and BROWNE, M A E. 1981. Quaternary estuarine deposits in the Tay-Earn area, Scotland. Report of the Institute of Geological Sciences, No. 81/7.

PATERSON, I B, and HALL, I H S. 1986. Lithostratigraphy of the late Devonian and early Carboniferous rocks in the Midland Valley of Scotland. Report of the British Geological Survey, No. 18/3.

PATERSON, I B, MACPHERSON, K A T, ARMSTRONG, M, and SMITH, E P. 1990. Geology for land use planning: Hamilton-Wishaw. British Geological Survey Technical Report, WA/90/30.

PAUL, M A, PEACOCK, J D, and BARRAS, B F. 1995. Flandrian stratigraphy and sedimentation in the BothkennarGrangemouth area, Scotland. Quaternary Newsletter, Vol. 75, 22–35.

PAUL, M A, PEACOCK, J D, and WOOD, B F. 1992. The engineering geology of the Carse clay at the National Soft Clay Research Site, Bo thkennar. Geotechnique, Vol. 42, 183–198.

PEACH, A M. 1909. Boulder distribution from Lennoxtown, Scotland. Geological Magazine, Vol. 46, 26–31.

PEACH, B N, and 6 others. 1910. The geology of the neighbourhood of Edinburgh (2nd edition). Memoir of the Geological Survey, Scotland.

PEACOCK, J D, GRAHAM, D K, ROBINSON, J E, and WILKINSON, I. 1977. Evolution and chronology of Lateglacial marine environments at Lochgilphead, Scotland. 89–100 m Studies in the Scottish lateglacial environment. GRAY, J M, and LOWE, J J (editors). (Oxford: Pergamon Press.)

PEACOCK, J D, GRAHAM, D K, and WILKINSON, I P. 1978. Late-Glacial and post-Glacial marine environments at Ardyne, Scotland, and their significance in the interpretation of the history of the Clyde sea area. Report of the Institute of Geological Sciences, No. 78/17.

POWELL, D W. 1970. Magnetised rocks within the Lewisian of Western Scotland and under the Southern Uplands. Scottish Journal of Geology, Vol. 6, 353–369.

PRICE, R J 1983. Scotland's environment during the last 30,000 years. (Edinburgh: Scottish Academic Press.)

RAMSBOTIOM, W H C. 1977. Correlation of the Scottish Upper Limestone Group (Namurian) with that of the north of England. Scottish Journal of Geology, Vol. 13, 327–330.

RAMSBOTIOM, W H C, and 6 others. 1978. A correlation of Silesian rocks in the British Isles. Special Report of the Geological Society of London , No. 10.

READ, W A. 1959. The economic geology of the Stirling and Clackmannan Coalfield, Scotland: area south of the River Forth. Coalfield Paper of the Geological Survey of Great Britain, No. 2.

READ, W A. 1961. Aberrant cyclic sedimentation in the Limestone Coal Group of the Stirling coalfield. Transactions of the Edinburgh Geological Society, Vol. 18, 271–292.

READ, W A. 1965. Shoreward facies changes and their relation to cyclical sedimentation in part of the Namurian east of Stirling, Scotland. Scottish Journal of Geology, Vol. 1, 69–92.

READ, W A. 1969. Fluviatile deposits in Namurian rocks of Central Scotland. Geological Magazine Vol. 106, 331–347.

READ, W A. 1981. Facies breaks in the Scottish Passage Group and their possible correlation with the Mississippian-Pennsylvanian hiatus. Scottish Journal of Geology, Vol. 17, 295–300.

READ, W A. 1988. Controls on Silesian sedimentation in the Midland Valley of Scotland. 222–241 in sedimentation in a synorogenic basin complex: the Upper Carboniferous of northwest Europe. BESLEY, B M, and KELLING, G (editors). (Glasgow and London: Blackie and Son.)

READ, W A. 1994. High-frequency, glacial-eustatic sequences in early Namurian coal-bearing fluviodeltaic deposits, central Scotland. Special Publication of the International Association of Sedimentology, Vol. 19, 413–428.

READ, W A, and DEAN, J M. 1978. High-alumina fireclays in the Passage Group of the Clackmannan Syncline, Scotland. Report of the Institute of Geological Sciences, No. 78/12.

READ, W A, and DEAN, J M. 1982. Quantitative relationships between numbers of fluvial cycles, bulk lithological composition and net subsidence in a Scottish Namurian basin. .Sedimentology, Vol. 29, 181–200.

READ, W A, and FORSYTH, I H. 1989. Allocycles and autocycles in the upper part of the Limestone Coal Group (Pendleian E1) in the Glasgow-Stirling region of the Midland Valley of Scotland. Geological Journal, Vol. 24, 121–137.

RICHARDSON, R. 1877. Notice of glaciated rock surfaces (displaying corals) near Bathgate, recently quarried away. Transactions of the Edinburgh Geological Society, Vol. 3, 108–109.

RICHEY, J E. 1937. Areas of sedimentation of Lower Carboniferous age in the Midland Valley of Scotland. 93–110 in Summary of progress of the Geological Survey for 1935. Part 2. (London: His Majesty's Stationery Office.)

ROBERTSON, T, SIMPSON, J B, and ANDERSON, J G C. 1949. The limestones of Scotland. Special Report on the Mineral Resources of Great Britain, Memoir of the Geological Survey of Great Britain, Vol. 35 (Scotland).

ROLFE, W D I. 1966. Woolly rhinoceros from the Scottish Pleistocene. Scottish Journal of Geology, Vol. 2, 253–258.

ROLFE:, W D I, and 5 others. 1994. The East Kirkton Limestone, Viséan, of West Lothian, Scotland: introduction and stratigraphy. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 177–188.

ROLFE, W D I, CLARKSON, E N K, and PANCHEN, A L (editors). 1994. Volcanism and early terrestrial biotas. Transactions of the Royal Society ofEdinburgh: Earth Sciences, Vol. 84, Parts 3 and 4.

ROSE, J, LOWE, J J, and SWITSUR, R. 1988. A radiocarbon date on plant detritus beneath till from the type area of the Loch Lomond Readvance. Scottish Journal of Geology, Vol. 24, 113–124.

RUDDIMAN, W F, and RAYMO, M E. 1988. Northern Hemisphere climate regimes during the past 3Ma: possible tectonic connections. Philosophical Transactions of the Royal Society of London, Vol. B318, 411–430.

RUSSELL, M J. 1971. North-south geofractures in Scotland and Ireland. Scottish Journal of Geology, Vol. 8, 75–84.

RUSSELL, M J, and SMYTHE, D K. 1983. Origin of the Oslo Graben in relation to the Hercynian-Alleghenian orogeny and lithosphere rifting in the north Atlantic. 457–472 in Processes of continental rifting. MORGAN, P, and BAKER, B H (editors). Tectonophysics, Vol. 94.

SHAKESBY, R A. 1978. Dispersal of glacial erratics from Lennoxtown, Stirlingshire. Scottish Journal of Geology, Vol. 14, 81–86.

SISSONS, J B. 1966. Relative sea-level changes between 10,300 and 8,300 BP in part of the Carse of Stirling. Transactions of the Institute of British Geographers, Vol. 39, 19–29.

SISSONS, J B. 1969. Drift stratigraphy and buried morphological features in the Grangemouth-Falkirk-Airth area, central Scotland. Transactions of the Institute of British Geographers, Vol. 48, 19–50.

SISSONS, J B. 1972. Dislocation and non-uniform uplift of raised shorelines in the western part of the Forth Valley. Transactions of the Institute of British Geographers, Vol. 55, 149–159.

SISSONS, J B. 1974a. Lateglacial marine erosion in Scotland. Boreas, Vol. 3, 41–48.

SISSONS, J B. 1974b. The Quaternary in Scotland: a review. Scottish Journal of Geology, Vol. 10, 311–337.

SISSONS, J B. 1976. Lateglacial marine erosion in south east Scotland. Scottish Geographical Magazine, 17–29.

SISSONS, J B, and SMITH, D E. 1965. Peat bogs in a post-glacial sea and a buried raised beach in the western part of the Carse of Stirling. Scottish Journal of Geology, Vol. 1, 247–255.

SISSONS, J B, and SMITH, D E. 1965. Raised shorelines associated with the Perth Readvance in the Forth valley and their relation to glacial isostasy. Transactions of the Royal Society of Edinburgh, Vol. 66, 143–168.

SMITH, A G, HURLEY, A M, and BIDDEN, J C. 1981. Phanerozoic paleocontinental world maps. (Cambridge: Cambridge University Press.)

SMITH, A H V, and BUTTERWORTH, M A. 1967. Miospores in the coal seams of the Carboniferous of Great Britain. Special Papers in Palaeontology, No. 1.

SMITH, R A, STEPHENSON, D, and MONRO, S K. 1994. The geological setting of the southern Bathgate Hills, West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 189–196.

SMITHSON, T R, CARRON, R L, and PANCHEN, A L. 1994. Wesilothiana lizziae from the Viséan of East Kirkton, West Lothian, Scotland, and the amniote stem. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 383–412.

SMYTHE, D K, RUSSELL, M J, and SKUCE, A G. 1995. Intracontinental rifting inferred from the major late Carboniferous quartz-dolerite dyke swarm of NW Europe. Scottish Journal of Geology, Vol. 31, 151–162.

STEDMAN, C. 1988. Namurian El tectonics and sedimentation in the Midland Valley of Scotland: rifting versus strike-slip influence. 222–241 in Sedimentation in a synorogenic basin complex: the Upper Carboniferous of northwest Europe. BESLEY, B M, and KEELING, G (editors). (Glasgow and London: Blackie and Son.)

STEIGER, R H, and JAGER, E. 1977. Subcommission on geochronology: convention on the use of decay constants in geo- and cosmochronology-. Earth and Planetary Science Letters, Vol. 36, 359–362.

STEPHENSON, D. 1983a. Hilderston mine, West Lothian: mining history and the nature of the vein mineralisation as deduced from old records. Open-file Report of the Institute of Geological Sciences. No. NL 83/4.

STEPHENSON, D. 1983b. Polymetallic mineralisation in Carboniferous rocks at Hilderston, near Bathgate, central Scotland. Mineral Reconnaissnce Report, Institute of Geological Sciences, No. 68.

STEVENSON, R B K. 1948 (for 1946). A shell-heap at Polmonthill, Falkirk. Proceedings of the Society of Antiquaries of Scotland, Vol. 80, 135–139.

STOKER, M S, LONG, D, and FYFE, J A. 1985. A revised Quaternary stratigraphy for the central North Sea. Report of the British Geological Survey, Vol. 17, No. 2.

SUTHERLAND, D G. 1984. The Quaternary deposits and landforms of Scotland and the neighbouring shelves: a review. Quaternary Science Reviews, Vol. 3, 157–254.

SUTHERLAND, D G. 1985. Reply to comments by M A E Browne on "The Quaternary deposits and landforms of Scotland and the neighbouring shelves: a review". Quaternary Science Reviews, Vol. 4, Pt 2, v-ix.

THOMSON, M E. 1977. IGS studies of the geology of the Firth of Forth and its approaches. Report of the Institute of Geological Sciences, No. 77/17.

UPTON, B G J. 1994. Regional setting of Carboniferous volcanism in the Midland Valley of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 209–212.

UPTON, B J G, ASPEN, P, and CHAPMAN, N A. 1983. The upper mantle and deep crust beneath the British Isles: evidence from inclusions in volcanic rocks. Journal of the Geological Society of London, Vol. 140, 105–121.

VARKER, W J, and SEVASTOPULO, G D. 1985. The Carboniferous System: part 1 - conodonts of the Dinantian Subsystem from Great Britain and Ireland. 167–209 in A stratigraphical index of conodonts. HIGGINS, A C, and AUSTIN, R L (editors). (Chichester: Ellis Honvood Limited.)

WALKDEN, G M, IRWIN, J R, and FALLICK, A E. 1994. Carbonate spherules and botr-yoids as lake floor cements in the East. Kirkton Limestone of West Lothian, Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 213–221.

WALKER, F. 1935. The late Palaeozoic quartz-dolerites and tholeiites of Scotland. Mineralogical Magazine, Vol. 24, 131–159.

WALKER, F. 1965. The part played by tholeiitic magma in the Carbo-Permian vulcanicity of central Scotland. Mineralogical Magazine, Vol. 34, 498–516.

WEIR, J, and LEITCH, D. 1936. The zonal distribution of the non-marine lamellibranchs in the Coal Measures of Scotland. Transactions of the Royal Society of Edinburgh, Vol. 58, 697–751.

WHYTE, M A. 1981. The Upper Brigantian (Lower Carboniferous) of central Strathclyde. Scottish Journal of Geology, Vol. 17, 227–246.

WHYTE, M A. 1994. Scottish Carboniferous fresh-water limestones in their regional setting. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 84, 239–248.

WILSON, M J, BAIN, D C, MCHARDY, W J, and BERROW, M L. 1972. Clay-mineral studies on some Carboniferous sediments in Scotland. Sedimentary Geology, Vol. 8, 137–150.

WILSON, R B. 1966. A study of the Neilson Shell Bed, a Scottish Lower Carboniferous marine shale. Bulletin of the Geological Survey of Great Britain, No. 24, 105–130.

WILSON, R B. 1967. A study of some Namurian marine faunas of central Scotland. Transactions of the Royal Society of Edinburgh, Vol. 66, 445–490.

WILSON, R B. 1989. A study of the Dinantian marine macrofossils of central Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 80, 91–126.

WOOD, S P, PANCHEN, A L, and SMITHSON, T R. 1985. A terrestrial fauna from the Scottish Lower Carboniferous. Nature, London, Vol. 314, 355–356.

Appendix 1Selected borehole and mine shaft information

This list includes the permanent record number, name, location, total depth and stratigraphical range of the selected boreholes and mine shaft sections that are referred to in this memoir. The sites and brief abstract logs of many of the bores and shafts listed are shown on the corresponding 1:10 000 geological maps listed in the History of Survey section. Copies of these records may be obtained from the British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA at a fixed tariff. Other non-confidential borehole records are held on open file in the Survey's archives.

Appendix 2 Author citations for fossil species

To satisfy the rules and recommendations of the international codes of botanical and zoological nomenclature, authors of cited species are listed below.

Carboniferous

Quaternary

Figures, plates, tables

Figures

(Figure 1) Outline geological map of the Falkirk district.

(Figure 2) Principal physical features and drainage of the Falkirk district.

(Figure 7)." data-name="images/P941462.jpg">(Figure 3) Sections of the Salsburgh No. 1A and Rashiehill boreholes. For locations see (Figure 7).

(Figure 7)." data-name="images/P941463.jpg">(Figure 4) Comparative vertical sections in the lower part of the West Lothian Oil Shale Formation. For locations sec (Figure 7).

(Figure 7)." data-name="images/P941464.jpg">(Figure 5) Comparative vertical sections in the upper part of the West Lothian Oil Shale Formation. For locations see (Figure 7).

(Figure 6) Geological map of the East Kirkton area.

(Figure 7) Outcrop of the Viséan formations with conjectural isopachytes for the Lower Limestone Formation.

(Figure 8) Comparative vertical sections in the Lower Limestone Formation. For locations see (Figure 7).

(Figure 9) Outcrop of the Limestone Coal Formation with isopachytes for the upper part.

(Figure 10) Comparative vertical sections in the Limestone Coal Formation showing local coal names.

(Figure 11) Outcrop of the Upper Limestone Formation with isopachytes in metres.

(Figure 12) Comparative vertical sections in the Upper Limestone Formation. For locations see (Figure 11).

(Figure 13) Outcrop of the Passage Formation with isopachytes.

(Figure 14) Comparative vertical sections in the Passage Formation; all are composite. For locations see (Figure 13).

(Figure 15) Outcrop of the Lower and Middle Coal Measures.

(Figure 16) Generalized vertical section of the Lower and Middle Coal Measures.

(Figure 17) Comparative vertical sections in the Lower Coal Measures in the northern part of the district. For locations see (Figure 15).

(Figure 18) Comparative vertical sections in the Lower Coal Measures south of the Banknock Fault and north of the Slamannan Fault. For locations see (Figure 15).

(Figure 19) Comparative vertical sections in the Lower Coal Measures south of the Slamannan Fault. For locations see (Figure 15).

(Figure 20) Comparative vertical sections in the Middle Coal Measures. For locations see (Figure 15).

(Figure 22)." data-name="images/P941480.jpg">(Figure 21) Stratigraphical position of the volcanic rocks in the lower part of the Dinantian sequence. For borehole locations see (Figure 22).

(Figure 22) Lateral extent of the Bathgate Hills Volcanic Formation. The conjectural lines are based on the outcrop and on scattered, unevenly distributed boreholes. Most boreholes are relatively shallow and volcanic rocks may be more extensive at depth.

(Figure 23) Principal stuctural features.

(Figure 24a) Geophysical anomaly maps a. Bouguer gravity anomalies for the Falkirk district and surrounding area reduced to 01) at a density of 2.75 Mg nr3, contour values in mGal. Lines QB-1, QB-2 are quarry blast seismic refraction profiles (Davidson et al., 1984). Also shown are the MAVIS lines (Dentith and Hall, 1989). Euler deconvolution solutions of the gridded gravity data are shown as colour bars, length proportional to depth. Line A-A' is the location of the Werner deconvolution solutions on Figure 25 and of the model profile in Figure 27. Dashed lines are seismic reflection profiles. The shaded area is the outcrop of the Carboniferous lavas from the 1:250 000 geological map.

(Figure 24b) Geophysical anomaly maps. b. Total field aeromagnetic anomalies for the Falkirk district and surrounding area observed at 305 m above terrain along east-west flight lines with contour values in nT. Dashed lines labelled SRP1 etc. are the locations of seismic reflection profiles. Euler deconvolution solutions of the gridded magnetic data after upward continuation by 0.2 km and reduction to the pole are superimposed as colour bars with length proportional to depth.

(Figure 25) Werner deconvolution solutions of observed aeromagnetic data along north-south line 293 kmE (line A-A' on (Figure 24a)(Figure 24b)). Observed profile and calculated derivative profiles have been smoothed with a nine point operator before deconvolution.

(Figure 26) Profiles of geophysical anomalies and picks of unmigrated seismic reflections seen in the southern part of seismic reflection profile SRP 3 west of Bathgate (for location see (Figure 24b). Coloured dashed line between about 300 and 550 indicates the postulated Bathgate-Campsie high.

(Figure 27) Gravity and aeromagnetic profiles and an integrated gravity and magnetic model along a north-south profile over the Bathgate structure (for location see (Figure 24a) and (Figure 24b). Observed data modelled to a depth of 40 km against a mean crustal density of 2.95 Mgm-3 and background magnetisation zero. SVF Salsburgh Volcanic Formation, BHVF Bathgate Hills Volcanic Formation. Model density and susceptibility shown for selected polygons.

(Figure 28) Distribution of Quaternary deposits and features.

(Figure 29) Location of the Falkirk district in relation to Geology for Land Use Planning projects in Central Scotland.

Plates

(Plate 1) The Firth of Forth, Grangemouth and Kincardine. View over the upper Forth estuary towards the 'Carse', Grangemouth, centre left, and Kincardine, centre right. The hills in the distance beyond Grangemouth are the Campsie fells and Gargunnock Hills, formed from lavas of the Clyde Plateau Volcanic Formation. On the right beyond Kincardine are the Ochil Hills with the Southern Highlands around Callander in the distance over the water. (D 5074).

(Plate 2) Antonine Wall near Rough Castle [NS 841 799], Bonnybridge. At its eastern end, east of Falkirk, the wall is located on the crest of the hack-feature of the Raised Reach. The position gave the advantage of elevation and outlook over the flat-lying carse land to the Roman forces defending the northernmost areas of the Roman occupation in the second century AD. (D5104),

(Plate 3) East Kirkton Quarry [NS 990 092], near Bathgate. The East Kirkton Limestone in the upper part of the West Lothian Oil Shale Formation is a laminated freshwater limestone. A unique and varied terrestrial assemblage of fossils have been collected from this site, including Westlothiana lizziae, a vertebrate fossil intermediate between amphibians and reptiles, (D 5094).

(Plate 4) East Kirkton Limestone. Cut surface of a hand specimen showing lamination and intraformational folding. (D 5097).

(Plate 5) Westlothiana lizziae Smithson and Rolfe. Fossil skeleton of the key linking form between amphibians and reptiles, popularly known as 'Lizzie'. The 20 cm long specimen was discovered in 1988 by the commercial collector, Mr Stan Wood. The specimen was purchased in July 1990 by the National Museums of Scotland (NMS G 1990.72.1), following a nationwide appeal. The fossil was found in the East Kirkton Limestone near Bathgate at the top of the West Lothian Oil Shale Formation in the Brigantian stage of the Upper Viséan. BGS is grateful to the Trustees of the National Museums of Scotland for permission to reproduce this photograph (by Glyn Satterley).

(Plate 6) South Mine Quarry (disused) north of The Knock [NS 991 711]. Upward-coarsening sequence from mudstone into sandstone overlying the Petershill Limestone, Lower Limestone Formation. There is a thin dyke of the quartz-dolerite suite in the gully on the left. (D 5092).

(Plate 7) Siphonodendron sp. A fasciculate (dendroid) coral colony from the Petershill Limestone in the Lower Limestone Formation, collected from the former Petershill Reservoir [NS 985 695]. (D 5114B).

(Plate 8) Leven Seat Quarry [NS 945 577]. Levenseat Sandstone in the lower part of the Passage Formation. The face is approximately 14 m high. The quartz sandstone is typically fine to medium grained and cream coloured. Fauldhouse is in the centre right and the Southern Highlands can be seen in the distance. (Composite from D 5100 and D 5101A.)

(Plate 9) Crown hole caused by fireclay mining. A large crown hole or 'sit' caused by the collapse of the stoop-and-room workings in the Upper Bonnybridge Fireclay in the Passage Formation [NS 828 776]. (D 5107).

(Plate 10) South Roughcastle Opencast Site [NS 852 790]. The workings are in the lower part of the Lower Coal Measures and the uppermost beds of the Passage Formation. A fault can be seen displacing strata at the right-hand end of the face. (D 5083).

(Plate 11).Old coal working, packed with waste material exposed in 1978 m Threeprig Opencast Mine 8351 6141, northwest of Slums. The mine, which took coal from the Lower Coal Measures, is now closed. (D 2739).

(Plate 12) Carboniferous fossils: Strathclyde and Clackmannan groups. 1 Tornquistia youngi X 10, E2079, Neilson Shell Bed, Rashiehill Borehole, c. 774.00 m. 2. Rugosochonetes speciosus X 3, E2091, Neilson Shell Bed, Rashiehill Borehole, c. 774.00 m. 3 Anthracoceras aff. glabrum X 1, GSE11149, above Orchard Limestone, East Saltcoats Borehole, 371.86 m. 4 Archaeocidaris sp. X 1, GSE7653, Petershill Limestone, Petcrshill Quarry. 5 Pierinopectinella eximius X 1, GSE7695, Lower Limestone Formation, Petershill Quarry. 6 Schellwienella rotundata? X 1, GSE14556, above Index Limestone, Ogilface Borehole, 445.16 m. 7 Phillipsia eichwaldi X 1.5, GSE8674, Lower Limestone Formation, Skolic Burn. 8 Pernopecten fragilis X 2, E2091, Neilson Shell Bed, Rashiehill Borehole, c. 774.00 m. 9 Aulophyllum aff. fungites X 1, GSE7745, Lower Limestone Formation, Silvermine - north mine quarry, Bathgate. 10 Schizodus cf. taiti X 1, EB8022, No. 1 Marine Band, Torwood Glen. 11 Sanguinolites aff. plieatus X 1.5, GSE12139, Limestone Coal Formation, Kinneil No. 34 Borehole, 344.04 m. 12 Lingula straeteni X 3, GSE12367, above Plean Limestone, Netherton Borehole, 286.21 m. 13 Aviculopecten regularis? X 3, GSE14839, above Castlecary Limestone, Levenseat Opencast No. 14 Borehole, 14.57 m. 14 Lonsdaleia floriformis X 1, PS1550, Petershill Limestone, Bathgate. 15 Liralingua wilsoni X 1.5, GSE12330, ?Main Hosie Limestone, Rashiehill Borehole, c. 734.00 m. 16 Posidonia corrugata X 3, GSE11856, below Top Hosie Limestone, Rashiehill Borehole, c. 713.16 m. 17 Productus aff. carbonarius X 1, GSE11903, No. 1 Marine Band, Torwood Glen. 18 Hibbertopterus scouleri (cast of skull) X 0.3, GSE13985, East Kirkton Limestone, East Kirkton Quarry. 19 Sanguinolites sp. X 1, GSE11745, No. 3 Marine Band group, Bonnyside No. 1 Mine, 187.12 m.

(Plate 13) Carboniferous fossils: Coal Measures. 1. Carbonicola pseudorobusta X 1, GSE13599, Lower Coal Measures, Mountcow No. 8 Borehole, 10.16; 2. Carbonicola cf. torus X 1.5, GSE13600, Lower Coal Measures, Mountcow No. 12 Borehole, 20.57 m. 3. Dunbarella sp. X 1.5, E3186, Vanderbeckei Marine Band, Polkemmet No. 1 Borehole, 25.37 m.4. Carbonicola bipennis X 1, GSE13558, Lower Coal Measures, Falkirk 'funnel. 5. Curvirimula trapeziforma X 5, GSE13661, Lower Coal Measures, Polmont No. 7 Borehole, 5.35 m. 6. Carbonicola aff. crispa X 1.5, GSE13939, Lower Coal Measures, Rougheastle Opencast Site. 7. Carbonicola cf. extenuala X 1.5, GSE10287, Lower Coal Measures, streamlet north of Auchengeean. Carbonicola aff. polmontensis X 1, GSE13573, Lower Coal Measures, Bonnyburn Mine lip.

(Plate 14) Quartz-dolerite intruded into the Bathgate Hills Volcanic Formation, The Knock [NS 991 717]. The quartz-dolerite is a steeply inclined, transgressive part of the Midland Valley Sill which at this point is orientated approximately north-south. The quartz-dolerite forms the flat-topped ridge running from the right middle ground obliquely left to the skyline. The rocky knoll on the skyline on the left is The Knock, pail of the sill. (D 5089).

(Plate 15) Quartz-dolerite in Cairneyhill Quarry [NS 852 660], Forrestfield, part of the Midland Valley Sill, showing onion-skin weathering. (D 5081).

(Plate 16) Hummocky glacial deposits at Thieves Hill [NS 819 731] (left) and Scar Hill (right), west of Slamannan. Irregular, commonly steep-sided, mounds lying generally transverse to the Avon valley probably comprise part of a terminal moraine complex. (D 5109).

(Plate 17) Section through hummocky glacial deposits, Glen Village [NS 8855 7814]. The section shows a rather clayey flow till overlying a more rubbly till with mainly angular cobbles mostly of sandstone. At the base of the exposure is a pale coloured predominantly sandy unit with deformation structures and silty or coal-rich lenses. (D 5098B).

(Plate 18) Esker, Callendar Park [NS 904 792], Falkirk. Section near the western limit of the ReddingPolmont esker, which can be traced eastwards for about 6 km to Lathallan. It consists of coarse gravel and sand. (D 5084).

(Plate 19) Drumlin field draped with sand and gravel, Myrehead [NS 963 777], Linlithgow. Thin deposits of fluvioglacial sand and gravel forming a discontinuous drape over drumlins with a strong east-west orientation. (D5113).

(Plate 20) Flandrian Raised Beach and cliff near Bo'ness. The church on the right and the Town Hall in the middle distance are situated on the Devensian Raised Beach. (D5085).

(Plate 21) Grangemouth Oil Refinery and Docks built on the Flandrian Raised Beach and reclaimed inter-tidal flats. The Flandrian shoreline and former seacliff lie below the line of trees in the middle ground. In the distance are the Southern Highlands and the Ochil Hills (on the right). (D 5079).

(Plate 22) Commercial peat workings, Gardrum Moss [NS 898 759], California. The peat deposits occupy shallow depressions between long drumlinoid ridges. (D 5112).

(Plate 23) Sand and gravel pit. [NS 953 713] at Coniston, near Bathgate. The workings are in fluvioglacial deposits. Much of the low-lying ground beyond the pit is underlain by glaciolacustrine silt and clay and was formerly worked for brick clay. Cairnpapple Hill, with the radio mast, beyond the pit, is on the outcrop of the Bathgate Hills Volcanic Formation, and Torphichen, partly visible in the left middle distance, is built on quartz-dolerite or the Midland Valley Sill. (D 5086).

(Front cover)Cover photograph. Linlithgow Place [NT 003 773] birthplace of Mary, Queen of Scots, situated on a promontory on the south side of Linlithgow Loch. The underlying rocks are basaltic lavas of the Bathgate Hills Volcanic Formation. (D5075. (Photographer F.I. MacTaggart)

Tables

(Table 1) Geological succession in the Falkirk district Inside front cover

(Table 2) Classification of the Carboniferous in Scotland.

(Table 3) Lithostratigraphical names: Lower Limestone Formation.

(Table 4) Rock physical properties in the Falkirk district.

(Table 5) Lithostratigraphy of the Quaternary formations. Note: age in brackets is in calender years.

(Table 6) Typical chemical analyses of (a) fireclay and (b) washed silica sand.

Tables

(Table 1) Geological succession in the Falkirk district Inside front cover

SUPERFICIAL DEPOSITS (DRIFT)

Quaternary

FLANDRIAN STAGE (10 000 BP to present)

Landslip Scree

DEVENSIAN STAGE

Loch Lomond Stadial (11 000 to 10 000 BP)

Peat

Alluvium

Lacustrine deposits

Tidal river deposits

Raised marine deposits

Windermere Interstadial (13 500 to 11 000 BP)

Glaciomarine deposits

Glaciofluvial deposits

Glaciolacustrine deposits

Dimlington Stadial (27 500 to 13 500 BP)

Hummocky glacial deposits

Till

Pre-Dimlington Stadial (> 27 500 BP)

Sand and gravel

Till

SOLID ROCKS

SOLID ROCKS

Generalised thickness (m)

Carboniferous

WESTPHALIAN

Coal Measures (Scotland)

Middle Coal Measures:

Sandstones, siltstones, mudstones, ironstones, coals and seatrocks

90+

Lower Coal Measures:

Sandstones, siltstones, mudstones, ironstones, coals and seatrocks

145–205

NAMURIAN

Clackmannan Group

Passage Formation:

Mainly sandstones and fireclays

100–350

Upper Limestone Formation:

Sandstones, siltstones, mudstones, marine limestones, a few thin coals and seatrocks

150–435

Limestone Coal Formation:

Sandstones, siltstones, mudstones, ironstones, coals and seatrocks

110–400

DINANTIAN

Clackmannan Group

Lower limestone Formation:

Sandstones, siltstones, mudstones, marine limestones, a few thin coals and ironstones

107–200

Strathclyde Group

West Lothian Oil Shale Formation

Mainly sandstones with siltstones, mudstones, limestones, oil shales, coals and seatrocks

500+

Clyde Plateau Volcanic Formation

Mainly basalts and hawaiites

DINANTIAN - NAMURIAN

Bathgate Group

Bathgate Hills Volcanic Formation

Basaltic lavas and assciatcd pyroclastic rocks

Salsburgh Volcanic Formation

Basaltic lavas and pyroclastic rocks

Intrusions

Vents, plugs, sills and dykes of alkali dolerite and quartz-dolerite, of Carboniferous age, cut the rocks of thedistrict

(Table 3) Lithostratigraphical names: Lower Limestone Formation.

Standard

Bo'ness

Fife

Bathgate Hills

Top Hosie

Carriden No. 1

Upper Kinniny

Wairdlaw

Second Hosie

Carriden No. 2

Mid Kinniny

Wairdlaw

Mid Hosie

Carriden No. 3

Lower Kinniny

Petershill

Main Hosie

Carriden No. 4

Seafield MB

Petershill

Milngavie MB

Carriden No. 4a

Mill Hill MB

Blackhall

Carriden No. 5

Charlestown Main

Tartraven

Craigenhill

Charlestown Green

Hurlet

Carriden No. 6

Charlestown Station

West Kirkton

(Table 4) Rock physical properties in the Falkirk district.

Density Mgm-3

Susceptibility SI

Velocity km s-1

Carboniferous

Westphalian

2.55

3.5–3.9

Namurian

2.55

Dinantian

2.60

Dinantian lavas

2.72

0.06–0.12

4.0–4.5

Devonian

Upper Devonian

2.45

4.0

Lower Devonian

2.65

4.0–5.0

Lower Devonian Lavas

2.70

0.03

4.0–5.0

Lower Palaeozoic rocks Ordovician-Silurian

2.73

0.0005

3.7–5.7

Intrusive rocks Olivine-dolerite

2.84

0.035

4.1

Ouartz-dolerite

2.80

0.022

5.6

Diorite

2.83

0.020

5.6

Gabbro

2.83

0.030

Andesite

2.75

< 0.010

(Table 6) Typical chemical analyses of (a) fireclay and (b) washed silica sand.

Fireclay (calcined) Weight %

Silica sand Weight %

1

2

3

4

5

SiO2

52,05

51.62

57.09

52.19

98.60

A12O3

49.39

43.39

37.02

42.52

2.20

Fe2O3

1.79

2.30

2.40

2,36

0.55

CaO

0.22

0.28

0.32

0.19

0.02

MgO

0.41

0.44

0.58

0.41

-

Na2O

0.05

0.19

0.12

0.05

0.05

K2O

0.29

0.35

0.84

0.68

0.02

TiO2

1,17

1.46

1.58

1.44

-

Loss on ignition

-

-

-

-

0.26