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Geology of the Morpeth district — brief explanation of the geological map Sheet 14 Morpeth

B Young and D J D Lawrence. Abridged from the Sheet Description by D G Woodhall

Bibliographic reference: Young, B, and Lawrence, D J D. 2002. Geology of the Morpeth district — a brief explanation of the geological map. Sheet explanation of the British Geological Survey. 1:50 000 Sheet 14 Morpeth (England and Wales).

Keyworth, Nottingham: British Geological Survey. Printed in the UK for the British Geological Survey by B&B Press Ltd, Rotherham

© NERC 2003 All rights reserved. Copyright in materials derived from the British Geological Survey's work is owned by the Natural Environment Research Council (NERC) and/or the authority that commissioned the work. You may not copy or adapt this publication without first obtaining NERC permission. Contact the BGS Intellectual Property Rights Manager, British Geological Survey, Keyworth. You may quote extracts of a reasonable length without prior permission, provided a full acknowledgement is given of the source of the extract.

(Front cover) Cover photograph: The imposing crenellated tower of Belsay Castle [NZ 0848 7855] is one of the finest surviving examples of a medieval border tower house. Adjoining it on the left is the roofless ruin of the Jacobean manor house. Both the castle and manor house are built of a medium-grained sandstone, quarried locally from a thick sandstone unit that overlies the Corbridge (Lower Felltop) Limestone of Namurian age (D5174). (Photographer T S Bain).

(Rear cover)

Notes

The word 'district' is used in this Sheet Explanation to denote the area included in the geological 1:50 000 Series Sheet 14 Morpeth. National Grid references are given in square brackets throughout this description. Unless otherwise stated, all lie within the 100 km square NZ.

Numbers preceded by the letter E refer to thin sections in the BGS collection; numbers preceded by the letters D and L refer to the BGS photograph collection.

Acknowledgements

This Sheet Explanation was abridged by D G Woodhall from the Sheet Description for the Morpeth district authored by B Young and D J D Lawrence. Full acknowledgements are to be found within the Sheet Description.

The grid, where it is used on figures, is the National Grid taken from Ordnance Survey mapping.

© Crown copyright reserved Ordnance Survey licence number GD272191/2002.

Geology of the Morpeth district (summary from the (Rear cover))

(Figure 1) Geological succession in the Morpeth district

The Carboniferous rocks of the Morpeth district form part of the Solway–Northumberland Trough, in which a comparatively thick succession of sediments accumulated between Alston Block in the south and the Southern Upland and Cheviot massifs in the north. Sedimentation was controlled by contemporaneous movement along major fault lines, notably the Stublick–Ninety Fathom Dyke System. This important structural line is likely to have been inherited from the Iapetus Suture, the line of closure of the former, Iapetus ocean along which the ancient continents of Laurentia and Avalonia collided.

The Carboniferous rocks of the district comprise a succession of rhythmic units of limestone, mudstone, sandstone and coal. Marine limestones are common in the lowest part of the sequence, the Liddesdale Group, but become thinner throughout the Stainmore Group and are absent in the Coal Measures. Coal seams, which are thin and comparatively scarce in the lowest beds, become thicker and more numerous in the Coal Measures.

Earth movements during Late Carboniferous– Early Permian times caused tilting and faulting, and dolerite of the Whin Sill —the original sill of geological science — was intruded at this period. Younger dolerite dykes were associated with the Tertiary volcanic centres of western Scotland and Northern Ireland.

Superficial deposits of Quaternary age were deposited during the last, Devensian, glaciation. Till is widespread with smaller areas of glaciofluvial and glaciolacustrine deposits. Postglacial and recent deposits include alluvium, river terrace deposits and peat.

Coal has been by far the most important mineral product of the district. Deep mining has now ended within the district leaving an indelible legacy on the landscape. Several other minerals have been worked and large-scale limestone quarrying continues today. The district's geology has a profound influence on a wide range of planning, engineering and environmental issues.

Chapter 1 Introduction

This Sheet Explanation provides a summary of the district covered by the geological 1:50 000 Series Sheet 14 Morpeth, published in solid and solid and drift editions in 2000 (Figure 1). A more comprehensive description can be found in the Sheet Description (Young and Lawrence, 2002), and detailed information can be found in individual Technical Reports.

The Morpeth district lies in south central Northumberland. Carboniferous rocks, deposited between about 340 and 300 million years ago, underlie land which rises very gradually westwards, from the gently undulating coastal plain bordering the North Sea to low (about 200 m) hills in the west. Drainage is entirely to the North Sea, principally by way of the rivers Wansbeck, Blyth and Pont, in the central and southern part of the district. Western and central parts of the district are predominantly agricultural with sheep and cattle farming on extensive areas of permanent pasture, passing eastwards into more extensive arable land use. The eastern part of the district forms part of the Northumberland Coalfield. Although deep mining has now ended, exploration for further reserves of opencast coal is understood to be in progress. Most colliery buildings have been demolished and spoil heaps landscaped. The ancient market town of Morpeth, at the northern extremity of the district, is today the administrative centre of Northumberland.

During early Carboniferous times the area that was to become northern England consisted of a series of fault-bounded blocks and basins that influenced sedimentation, particularly during the early Carboniferous. It was during this time that the Liddesdale Group was deposited; this is Dinantian to earliest Silesian in age and contains the oldest rocks in the district. Sandstones, siltstones and mudstones accumulated in an extensive, low-lying deltaic swamp, but repeated marine incursions spread shallow seas across the district in which limestone and some shale was deposited. This pattern of sedimentation was repeated many times and produced a distinctive cyclic succession of rocks known, from their extensive development in North Yorkshire, as Yoredale cyclothems. A similar pattern of sedimentation continued throughout the deposition of the overlying Stainmore Group (Namurian), but a significantly greater proportion of nonmarine sedimentary rocks is a consequence of the decreasing frequency and shorter duration of the marine incursions. By the end of Namurian times the overall depositional environment had changed to that of an upper delta plain. Coal Measure (Westphalian) deposition was characterised by the accumulation of thick deposits of peat, derived from forest swamps that developed widely on the emergent delta surface, which are seen today as coal seams. Progressive subsidence resulted in the periodic submergence of the swamps, the creation of lakes and the burial of the peat by mud, silt and sand. This cycle of events was repeated many times. Marine incursions were now infrequent and are represented only by mudstones with a marine or brackish fauna.

Further extensional movements during late Carboniferous to early Permian times led to the widespread intrusion, about 295 million years ago, of the dolerite that forms the Whin Sill; the sill is almost certainly present at depth beneath much of the district. A few basaltic dykes were intruded about 52 million years ago, during the early Palaeogene. Apart from these, there is no evidence in the district of rocks younger than the Carboniferous, and a major unconformity that spans a period of about 300 million years exists between the Coal Measures and widespread glacial and postglacial deposits of Quaternary age. The Quaternary glacial deposits date from the most recent of a series of major glaciations, when Northumberland was buried beneath a thick mantle of ice, mostly originating in southern Scotland and Cumbria.

History of survey

The results of the primary geological survey were first published as Sheet 105NW (Old Series) in 1892. A revision survey, undertaken between 1922 and 1937, was published as Sheet 14 Morpeth in 1955, and was reprinted twice, the last time in 1970. Small areas along the western, southern and eastern margins of the district were resurveyed between 1959 and 1983 as part of the revision survey of sheets 13 Bellingham, 20 Newcastle and 15 Tynemouth. Systematic revision of the coalfield areas of the district was begun in 1983 as part of a programme of surveys commissioned by the Department of the Environment to provide modern geological and thematic maps for the region, with particular attention directed towards aspects of land-use planning. Resurvey of the Liddesdale and Stainmore groups was carried out between 1994 and 1996. These modern surveys have incorporated a huge volume of new data including the results of extensive exploration for opencast coal resources, site investigations and some geophysical surveys. These and other relevant data sources are listed in Information Sources.

Chapter 2 Geological description

Carboniferous

Carboniferous rocks form bedrock in the whole of the Morpeth district (Figure 1), (Figure 2). Their classification is summarised in (Figure 3), where it is compared with previous classifications used in adjoining districts (Lebour, 1876; 1886; Frost and Holliday, 1980; Mills and Holliday, 1998).

The Liddesdale Group

The Liddesdale Group comprises a succession of typical 'Yoredale' cyclothems characterised by the repetition of beds of limestone, mudstone, sandstone and, locally, thin coals. Only the upper part (210 m) crops out in the extreme west of the district; the succession is shown in (Figure 4). The limestones are mainly less than 5 m thick, although the Great Limestone, included here within the group, is up to 16 m thick (Plate 1). Most are laterally persistent over many kilometres and reliable correlations may be made with the equivalent limestones throughout the Northumberland Trough and the Alston Block, to the south (Holliday et al., 1975). Typically, these limestones are markedly bituminous, medium to dark grey biomicrites and biosparites in which shell and crinoidal debris is generally common. The majority are well bedded with thin mudstone or calcareous mudstone partings conspicuous, especially in weathered faces. A rather irregular 'wavy' bedding is characteristic of the Great Limestone. Where drift cover is thin or absent the limestones commonly give rise to low scarp features with limestone brash locally abundant in the soil. The clastic sediments interbedded with the limestones in the Liddesdale Group usually form the major portion of each cyclothem, and typically comprise coarsening-upwards cycles from mudstone to sandstone. Calcareous mudstones, found immediately above some limestones, are normally overlain by mudstones with plant debris and ironstone nodules. These pass upwards, by intercalation into interbedded siltstone and sandstone, flaggy sandstone and eventually into massive, cross-bedded slightly feldspathic sandstone. Cross-bedding directions normally indicate derivation from the north or north-east. Some sandstones clearly occupy erosive, wash-out channels. The tops of some sandstones commonly take the form of seatearths, penetrated by carbonaceous rootlet traces and, where particularly siliceous, comprise beds of ganister. Thin coals occur above these seatearths at several positions, though they are typically laterally impersistent and have only locally proved to be workable on a very small scale.

The thickest and most persistent coal within the Liddesdale Group of the district is the Townhead Coal, generally about 0.15 m thick, which lies almost immediately beneath the Great Limestone (Figure 4). This coal and its sandstone seatearth are well developed in the south-west of the district where it has been worked.

Palaeontological studies of the Liddesdale Group in the district tend to substantiate a Brigantian (Dinantian) age for the Three Yard and Four Fathom limestones, and a probable lower Pendleian (Silesian) age for the Great limestone (Dean and Brand, 1998; Riley,1998a, b). In the limestones, macrofossils including corals, brachiopods and bivalves are locally conspicuous, especially on weathered faces. Microfossils include algae, foraminifera, ostracods and conodonts. A distinctive feature of the Four Fathom Limestone is the abundance, especially near the base, of beds rich in the alga Saccamminopsis fusulinaformis.

Stainmore Group

The Stainmore Group (Namurian), referred to as the Morpeth Group by Young and Lawrence (1998), crops out in western and central parts of the district (Figure 2).

The overall succession is summarised in (Figure 5). The maximum thickness is approximately 500 m, but there are local variations, especially where channel-fill sandstones are present. The group comprises a cyclical succession of thin limestones, mudstones, siltstones, sandstones and some thin coals. The limestones are generally thinner and comprise a smaller proportion of each cycle than in the Liddesdale Group. Clastic sediments, particularly sandstones, typically occupy a greater proportion of each cycle, and coals are rather more common and laterally persistent. However, the main lithologies of the Stainmore Group closely resemble those of the Liddesdale Group.

Limestones form a relatively small proportion of the Stainmore Group but are important stratigraphical markers, which allow correlation with adjoining districts. Most are less than 5 m thick and are today generally poorly exposed except in a few abandoned quarries. Like the limestones of the Liddesdale Group, those within the Stainmore Group are typically medium grey biomicrites and biosparites in which scattered shell and crinoid fragments may be seen locally, especially on weathered surfaces. Stainmore Group limestones appear to contain a rather greater proportion of clay and silt than those of the Liddesdale Group. Brown earthy weathering is common.

A large part of the Stainmore Group consists of sandstones (Figure 5); (Plate 2). Most are fine- to medium-grained, slightly feldspathic rocks that in most instances closely resemble those of the Liddesdale Group. They appear to have a characteristic sheet-like form and are apparently laterally extensive over several square kilometres. Some of these give rise to prominent landscape features, for example at Heugh Neb [0174 8108], Ingoe [0433 7540] and at Harnham [0740 8050].

The Stainmore Group of the Morpeth district is distinguished by a few much coarser grained, locally pebbly, sandstones that clearly occupy well marked, restricted channels. These sandstones include the Shaftoe Grits (Figure 5); (Plate 3), which appear to occupy a major erosive channel system, the course of which was determined by penecontemporaneous movement along precursors of a north-east-trending graben structure formed today by the South Middleton–Marlish and Hallington Reservoir faults. Within this graben the Belsay Dene, Corbridge, and Thornbrough limestone cyclothems have been removed by erosion along the channel system now occupied by the Shaftoe Grits.

Coals are more numerous and more laterally extensive in the Stainmore Group than in the Liddesdale Group. Several have been worked, though generally only on a small scale and in limited areas. The most widespread, and formerly most widely worked, is the Little Limestone Coal.

Zonally significant goniatites are rare, and only from the Great Limestone and beds in the limestone group above the Dalton Limestone are there more than single records. Consequently, direct comparison with Namurian basinal faunas is not possible.

The mudstones above the Great Limestone at Mootlaw Quarry, Matfen [NZ 023 754] have yielded a large fauna. This includes brachiopods, gastropods, bivalves, and crinoid material, which was listed and discussed by Dean and Brand (1998) and Riley (1998a, b). Of particular interest is the presence of goniatites that suggest the E1a Goniatite Zone. Macrofaunas above the Great Limestone up to the Corbridge Limestone show little variation, although the presence of Rugosochonetes speciosus especially above the Great Limestone helps to distinguish this part of the sequence. Above the Little Limestone, the marine beds are more sandy and species of Schellwienella and Serratocrista become more common. However, it is difficult to distinguish individual marine beds one from another on the basis of their contained macrofauna.

Throughout Northumberland a major macrofaunal change takes place at the Thornbrough Limestone with the incoming of an extensive marine fauna not previously recognised in Namurian strata in the region.

Miospores from mudstones shortly above this bed suggest it is very close to the boundary between the E1 and E2 goniatite zones (Owens, 1972). There are no recorded goniatites to recognise the basal Westphalian marine bands, although the bed correlated with the Quarterburn Marine Band of Durham has been accepted as the most likely correlative of the Subcrenatum Marine Band (Mills and Hull, 1968).

Coal Measures

The Coal Measures (Westphalian) crop out in the eastern part of the district (Figure 2) and consist of about 380 m of strata comprising cyclothems of mudstone, siltstone, sandstone, seathearth and coal (Figure 6). Many cyclothems are incomplete owing to their deposition in deltaic and lacustrine environments where local rather than regional factors determined lithologies. The base of the Coal Measures is that of the inferred position of the Subcrenatum Marine Band. The mudstones commonly include nodules and thin beds of ironstone. Marine mudstones tend to be darker grey, silty and contain large mica flakes. Sandstones are feldspathic with dominant quartz and subordinate feldspar. Two different geometric forms can be recognised in the sandstones. Sheet sandstones are generally less than 5 m thick, are fine to medium grained, thinly bedded with cross-bedding and with interbedded siltstone and mudstone at top and base. Channel sandstones may be up to 30 m thick, massively cross-bedded with a meandering ribbon shape in plan and with limited lateral extent. Their thickness is very variable. Their bases are generally erosive and in places they cut down through the underlying coals forming washouts in the seams. The two geometrical forms are not mutually exclusive and many are composite. Seatearths resemble other Coal Measures mudstones, but they show a complete lack of bedding and usually contain numerous plant roots. Ironstone nodules are common and sphaerosiderite is present locally. Dean and Brand (1998) have undertaken a review of British Geological Survey holdings of fossils from the Coal Measures rocks of the district.

Lower Coal Measures

The Lower Coal Measures comprise about 120 m of strata between the base of the 'Subcrenatum' and Vanderbeckei Marine bands. From the bottom upwards as far as the Marshall Green coals the succession is sandstone dominated, with impersistent thin coals and thin mudstones (Figure 7). The Marshall Green is the lowest coal to have been extensively worked. The impersistent thin Stobswood Coal is overlain throughout much of the district by a mudstone bed with a fauna indicative of the Stobswood Marine Band. Sandstone comprises much of the sequence from this marine band to the overlying Victoria and Brockwell coals. A geographically widespread, if faunally variable, mussel band known as the Victoria Shell Bed, occurs above the Victoria Coal. The thickness and quality of this increases north-eastwards across the district. The strata between the Three-Quarter and the overlying Busty coals is dominated by a thick, locally coarse-grained and conglomeratic, sandstone which forms the roof of the Three-Quarter Coal. Throughout much of the district the Beaumont Coal is overlain by a mudstone unit which contains a fragmental clayrock at its base (Richardson and Francis, 1971) succeeded by a distinctive shell bed containing a mussel–ostracod fauna termed the Hopkins Band (see Land, 1974, for origin of the name). The sequence up to the Vanderbeckei (Harvey) Marine Band contains a thick south-east-trending channel sandstone in the north of the district but is variable elsewhere, commonly with two thin impersistent coals.

Middle Coal Measures

The Middle Coal Measures are about 250 m thick and include the thickest and most persistent coal seams. The Vanderbeckei (Harvey) Marine Band consists of up to 1 m of very dark grey to black shale containing, predominantly, Lingula mytilloides. Massive sandstone occupies much of the sequence between the marine band and the Plessey Coal. Measures between this and the Northumberland Low Main Coal are variable in lithology and contain an intermediate thin coal, the Broomhill Main Coal (Plate 4). Two fossiliferous beds occur in places above the Plessey, the upper containing a prolific fauna and referred to as the Plessey Shell Bed. The measures above the Northumberland Low Main Coal, up to the Durham Low Main Coal, are variable both in lithology and thickness, ranging from as little as 2 m up to 27 m and with mussel bands and thin coals developed locally. Throughout most of the district the Durham Low Main Coal is overlain by a massive, cross-bedded, medium-grained sandstone, the Low Main Post, which in the south generally rests directly on the coal and provides an excellent roof for workings. The sandstone was quarried within the district. The mudstone overlying the Bottom Bensham Coal in the west of the district carries a mussel band, but the interval between the Bensham and the overlying Yard coal is dominated by a thick sandstone which in places has cut down through the Bensham Coal. North of Wolsington the Yard Coal is locally overlain by a thick sandstone. The thin Bentinck Coal has a fossiliferous mudstone forming its roof. Succeeding strata contain, in upward succession, the Metal, Five-Quarter and High Main coals. The strata between the High Main Coal and the Maltby (High Main) Marine Band is variable.

In the south of the district and near Bedlington, the High Main is itself overlain by a massive sandstone, the High Main Post. The Maltby Marine Band is overlain by a prolific mussel band. Strata above the Maltby Marine Band are exposed only in the south-east of the district. Up to six named coals are present in the sequence up to the Haughton (Kirkby's) Marine Band. This is characterised by an alternation of marine and nonmarine phases. The strata up to the overlying Sutton (Hylton) Marine band consist mainly of sandstone. The succeeding strata up to the Aegiranum (Ryhope) Marine Band (which forms the base of Bolsovian strata) is also dominated by massive, coarse-grained and locally pebbly sandstone with the thin Burradon Coal near its base.

Upper Coal Measureserlie

The Upper Coal Measures are inferred to crop out immediately north of the Ninety Fathom Dyke near Longbenton. These few tens of metres of measures are among the highest Westphalian strata in Northumberland. However, the basal Cambriense (Down Hill) Marine Band itself has not been proved within the district.

Intrusive igneous rocks

Permo-Carboniferous intrusions

Permo-Carboniferous intrusions are represented by quartz dolerite of the Whin Sill, the original sill of geological science, and a few associated dykes, which crop out in the extreme north-west of the district around Kirkwhelpington. From regional considerations, the sill is believed to underlie the whole of the district south-east of these outcrops. Aspects of the concealed areas of Whin Sill are discussed in the concealed geology section. The sill is intruded in the Liddesdale Group at various levels from beneath the Shotto Wood Limestone, between the Upper Bath-House Wood and Eelwell limestones, immediately beneath the Four Fathom Limestone, and at variable levels between the Four Fathom and Great limestones. It was proved in the Throckley Borehole [NZ 1456 6762] (NZ16NW/45), in the extreme south of the district. Here the sill is 38.5 m thick between the Great and Little limestones. Four boreholes in the Belsay and Black Heddon areas recorded Whin Sill dolerite between 1.2 and 2.3 m thick between the Little and Oakwood limestones. The small thickness of dolerite suggests these may be part of a thin upper leaf, with the main sill present at a greater depth. The dolerite in outcrop typically displays crudely developed columnar jointing, locally with dark brown spheroidal weathering of jointed blocks. In hand specimen, the dolerite is typically a fine-grained, dark grey rock, without obvious phenocrysts. A thin section of this rock (E71826) shows it to be composed principally of relatively fresh plagioclase, clinopyroxene and some opaque iron oxides with fairly common interstitial pockets of micrographic quartz-feldspar intergrowths (Beddoe-Stephens, 1998). A few phenocrysts of altered orthopyroxene occur in the dolerite cored in the Throckley Borehole.

Associated with the Whin Sill of Northumberland are numerous related dykes which may be separated into four discrete dyke echelons with a general north-east to east-north-east trend (Randall, 1980a, b). Dykes which form part of the St Oswald's Chapel Dyke Echelon cross the north-western part of the district.

Dolerite dykes are known to occupy the Hallington Reservoir Fault at several localities and it is possible that much, if not all, of this fault may be intruded by Whin Sill dolerite across the district.

Little is known of the contact metamorphic effects of the Whin Sill and its associated dykes in the district as there are very few exposures of the country rocks close to the intrusions. The Eelwell Limestone at Ivy Crag [NZ 0022 8445], on the south bank of the River Wansbeck at Kirkwhelpington, is recrystallised to a medium-grained marble adjacent to the sill. The composition of hydrocarbons in veins in the Great Limestone at the abandoned quarry [NZ 0170 7865] south of White House suggest thermal metamorphism (Creaney et al., 1980).

Palaeogene intrusions

Palaeogene intrusions are represented by a few west- to west-north-west-trending basic dykes that cut the Coal Measures. They have been quarried on a small scale locally and have been encountered in places in underground coal workings, though none is exposed today. These dykes form part of a large suite of dykes of the same general trend as elsewhere in northern England, which form part of a dyke swarm emanating from the Palaeogene igneous centre of Mull in western Scotland. Although differences in petrography have been noted between individual dykes they are all tholeiitic dolerites. They are typically olivine-free or olivine-poor plagioclase-clinopyroxene rocks, with the feldspar and pyroxene generally exhibiting an ophitic relationship, and with an intersertal texture and glassy mesostasis, which is usually devitrified or microcrystalline. Anorthite phenocrysts may be present. The longest mapped outcrop of a Palaeogene dyke in the district is that of the Coley Hill Dyke [NZ 1555 6810] to [NZ 1918 6746] in the North Walbottle and Westerhope area. This dyke is recorded as reaching 23 m in width locally. It was worked in a small quarry at Whindykes [NZ 1859 6760] where the adjacent Five-Quarter Coal was burnt to coke; there is no longer any exposure.

Structure

The Carboniferous rocks exhibit a gentle regional easterly dip rarely exceeding 10º. This comparatively simple structure is interrupted by a shallow syncline in the Tranwell–Saltwick area, south of Morpeth. Lawrence and Jackson (1986) noted a series of open, minor flexures within this structure, together with a minor east–west-trending anticline marking the southern limit of the folded strata south of Bells Hill [NZ 195 789].

Small-scale folds or 'rolls' are common within the Great Limestone and typically exhibit amplitudes and wavelengths of only a few metres, and fold length, measured along the fold axes, is usually of the order of a few tens of metres. The orientation of these folds typically varies from north–south to north-east–south-west. Shiells (1964) described a variety of such folds in the Great Limestone and other limestones throughout Northumberland.

The faults that intersect the Carboniferous rocks are mostly east-north-east-trending, but some trend east-south-east, especially in the eastern part of the district. In common with similar areas elsewhere, the degree and complexity of faulting within the Coal Measures outcrop in the district almost certainly reflects the very much larger volume of data for these rocks compared with that for the outcrops of the Stainmore and Liddesdale groups. The district is crossed, in the extreme south-east, by the east-north-east-trending Ninety Fathom Dyke. This forms part of the Ninety Fathom–Stublick Fault System that bounds the Northumberland Trough on its southern side, separating it from the structural unit of the Alston Block to the south. This fault throws down to the north at between 200 m and 280 m, and locally has a hade of up to 45º. There are other faults with a predominantly east-north-east trend, parallel to that of the Stublick–Ninety Fathom Fault. Several of these are traceable from the adjoining Bellingham district on the west and also continue eastwards into the Tynemouth district. Prominent amongst these is the Hallington Reservoir Fault that enters the district west of Kirkheaton. Dolerite dykes, which are part of the Whin Sill suite, are known to occupy this fault at several places along its outcrop. It is possible that much, if not the whole of this fault may have been exploited by this intrusion.

Faults within the Coal Measures mostly exhibit displacements of 25 m or less, but up to 70 m throws are recorded for a few faults. Many faults terminate against crossfaults, whereas others die out gradually as their throw reduces or as they pass into several fractures, commonly with opposing throws.

Concealed geology

Outcrop and borehole evidence from elsewhere in northern England and southern Scotland suggests that the Carboniferous strata exposed in the Morpeth district probably rest on Lower Palaeozoic sedimentary rocks that were deformed and metamorphosed during the Caledonian orogeny. A fundamental, broadly north-east-trending basement boundary beneath the district constitutes the Iapetus Suture, which marks the Caledonian collision boundary between terranes from the northern (Laurentian) side of the ancient Iapetus Ocean and those originating from its southern (Avalonian) side (McKerrow and Soper, 1989 and references therein). It is likely that the broad form of the Northumberland Trough (and in particular its faulted southern margin) is to some degree 'inherited' as a result of reactivation of the Iapetus Suture and associated thrusts (compare with Chadwick and Holliday, 1991).

There is a major sedimentary thickening across the Stublick–Ninety Fathom Fault System, between the relatively uplifted Alston Block to the south and the Northumberland– Solway Basin to the north (Chadwick et al., 1993, 1995). In the south-eastern corner of the district there is a deepening of the Caledonian basement from about 2000 m to almost 5000 m across the basin margin faults. Analysis of seismic reflection data indicates that a large part of the thickness variation in the Carboniferous sequence across the basin margin is the result of syndepositional fault movement. The importance of the basin margin structures is not evident from the Upper Carboniferous outcrop pattern, but is reflected in a strong gravity gradient across the Ninety Fathom Fault (see inset gravity map on geological 1:50 000 Series Sheet 14). Gravity data also indicate the presence of a cupola of the Weardale granite to the south of the district which is likely to have played a role in maintaining the rigidity and relative buoyancy of the Alston Block (Evans et al., 1988; Kimbell et al., 1989).

The Permo-Carboniferous and Palaeogene igneous intrusions within the district have a significantly higher magnetisation than the rocks they intrude, and give rise to distinct magnetic anomalies. The anomalies due to Palaeogene dykes in this district are typically east-south-east-trending and have a strong negative anomaly, whereas dykes of Permo-Carboniferous age are generally north-east-trending and have a positive anomaly; structures affecting the Whin Sill have a variety of responses depending on their geometry. The western limit of the south-east-dipping Whin Sill is marked by a pronounced magnetic anomaly in the north-west corner of the district.

Quaternary

Quaternary (drift) deposits mantle almost the entire Morpeth district and, except in a few places, mainly in the west and in some valley bottoms, largely conceal the underlying Carboniferous rocks. The unconformity which separates the solid and drift deposits in north-east England represents a very long period of geological history during which perhaps as much as 2000 m of Mesozoic strata, and some Upper Carboniferous rocks, were removed by erosion (Holliday, 1993). It is likely that the district experienced several periods of glaciation during the Pleistocene, though the deposits seen today date only from the latest (Late Devensian) glaciation. Any deposits formed during earlier glaciations have either been removed or recycled by subsequent glaciations.

Despite the widespread occurrence of drift deposits they are typically very poorly exposed. Information on their nature is derived largely from records of boreholes and temporary sections.

Rockhead surface

Borehole evidence suggests that the rockhead surface has an appreciably greater relief than the till plain that forms the present-day surface (Lawrence and Jackson, 1986, 1990). Pre-existing, possibly preglacial, valleys coincident with, or marginally offset from the present-day valleys of the Wansbeck, Catraw Burn, River Blyth, and Ouse Burn are largely infilled with glacial drift.

Glacial meltwater channels

Glacial meltwater channels, formed during de-glaciation, occur in places, and whereas some may have developed along pre-existing, possibly fault-controlled valleys many developed in response to local topography and ice cover during deglaciation.

Till

Till dominates glacial deposits, which cover more than 75 per cent of the district. It is in excess of 60 m thick in the Morpeth and Stannington areas (Lawrence and Jackson, 1990). Where unweathered, the till is typically a stiff, grey to greyish brown, silty, sandy or stony clay. Thin sand lenses and partings of sand, gravel, silt and clay are common throughout. Included cobbles and boulders consist chiefly of Carboniferous rocks, mainly sandstone with subordinate amounts of limestone, siltstone, mudstone, ironstone and coal. Dolerite, from the Whin Sill, is common, especially in the west of the district. More rarely a few far-travelled erratics are present. Greywacke sandstones and granites, derived either from south-west Scotland or the Lake District are sparingly present across much of the district. Volcanic rock types, derived from the Borrowdale Volcanic Group of the Lake District, are found throughout much of the south of the district. Cheviot volcanic rocks occur sparingly only in the north-eastern part of the district. A probable glacially transported sandstone 'raft' of this sort within a thick till sequence occurs north of Stannington [NZ 212 802], and much larger 'rafts', more than 270 m long, were found in the Tranwell and Glororum opencast coal sites [NZ 185 837]; [NZ 191 822] (Lawrence and Jackson, 1990). The district's largest known erratic occurs at Down Hill [NZ 005 684], east of Halton Red House, and consists of a glacially transported raft of Great Limestone up to 600 m across that forms a prominent low hill (Plate 5). The erratic must have been derived from outcrops at least 3 km distant to the north or west.

In places, the present-day surface of the till is moulded into a series of gentle, low, drumlin-like ridges with a generally east–west alignment, parallel to the direction of ice flow during the last glacial period.

The greater part of the till which mantles the area is largely an overconsolidated lodgement till, thought to be the product of a single Late-Devensian glacial episode. However, Lawrence and Jackson (1986, 1990) commented on the widespread occurrence of a distinct upper layer of till comprising mottled orange-brown and grey clay with a significantly lesser stone content. This they interpreted as an upper lodgement, ablation or flow till, a product of gelifluction or a postglacial weathering profile (Eyles and Sladen, 1981).

Glaciofluvial sand and gravel

Glaciofluvial sand and gravel is extensive along the River Wansbeck, in parts of the surrounding country downstream from Meldon Park [NZ 109 850], in the Ogle [NZ 137 788] and Kirkley Hall [NZ 150 772] areas, and around Eachwick [NZ 115 711] and Fawdon [NZ 227 696].

These deposits are commonly marked by irregular, hummocky, well-drained country, for example around Eachwick, Kirkley Hall and north of Meldon [NZ 119 841]. The sand and gravel usually rests on boulder clay and a spring line is common at the base. The deposits have also been encountered in a number of boreholes and trial pits (Lawrence and Jackson, 1986). The few exposures of these deposits are of fine- to medium-grained sand with silty and clayey interbeds, and with lenses and layers of pebble and cobble gravel up to 2 m thick.

As in the adjoining district (Mills and Holliday, 1998), the form and distribution of the sand and gravel deposits are consistent with deposition having taken place dominantly in a subglacial environment from seasonal streams and from bodies of water under wasting or stagnant ice. It is possible, however, that some of the deposits may have been laid down in ephemeral ice-impounded proglacial lakes.

Glaciolacustrine silt and clay

Glaciolacustrine silt and clay, usually laminated, stone-free and with intercalated very fine-grained sand lenses and partings, crops out in the valleys of rivers Blyth and Pont (Lawrence and Jackson, 1986). Similar sediments are also recorded in boreholes and trial pits in the Ponteland area. Other, apparently less extensive, occurrences of laminated silt and clay have been observed in cliff sections on the River Font [NZ 165 860], at Scotch Gill [NZ 1823 8610], west of Broad Law [NZ 155 799] and in site investigation boreholes west of Morpeth. Laminated silt and clay may be more widespread than indicated by known occurrences. Most of these sediments were probably deposited in subglacial and subaerial lacustrine environments in glacial and late-glacial times.

Postglacial and recent deposits

Postglacial and recent deposits accumulated during the warmer, wetter climate of the last 10 000 years. During this time the modern drainage pattern has developed. River terrace sands and gravels occur along the rivers Wansbeck, Font and Pont. A discontinuous veneer of sand and gravel overlying laminated clay, which flanks the River Blyth, probably also represents terrace deposits. Terrace surfaces lie between 3 and 10 m above present river level. In places a number of individual terraces are identifiable but no lateral correlations have been established. Isolated flat-topped features about 17 m above river level north-east of Buck Haughs [NZ 164 862] and west of Newminster Abbey [NZ 187 858] probably represent remanié terraces (Lawrence and Jackson, 1986). Alluvium occurs as narrow, discontinuous tracts flanking rivers and small streams throughout the district. The alluvial deposits do not usually exceed 3 m in thickness and consist generally of laterally variable clay, silt and fine sand. In the Wansbeck valley between Bothal [NZ 240 865] and Sheepwash [NZ 256 857] the alluvium appears to consist of sand and gravel (Lawrence and Jackson, 1990). Lenses of peat, or peaty clay may be present and gravel is common at the base. Alluvial fan deposits occur locally, where tributaries meet main streams; in each case small deltas of alluvial material, generally similar in composition to much of the nearby river alluvium, have accumulated. Lacustrine deposits infill small flats and hollows, throughout the district, notably at Prestwick Carr [NZ 190 740] and adjacent low ground near Ponteland. This lacustrine alluvium may reach in excess of 8 m in thickness, and comprises sand with pebbly, silty and clayey partings. Very small areas of Marine or estuarine alluvium occur in the Wansbeck valley north of Stakeford [NZ 273 858] and in the Blyth valley near Bedlington [NZ 276 819]. These deposits consist of silts, sands and gravels. Peat occurs in places, filling small hollows or the sites of former lakes, and is most extensive at Prestwick Carr [NZ 190 740] where it reaches a maximum proved thickness of 2.7 m (Lawrence and Jackson, 1986). Other significant peat accumulations include those adjacent to the River Blyth south of Cocklaw Walls [NZ 008 781], and south of Sandybraes [NZ 030 786] where up to 1.5 m of peat has been proved by augering. Peat has also been proved as beds and lenses within alluvial deposits encountered in several boreholes. Small mounds of tufa, up to 2 m high, are currently being deposited from lime-rich water adjacent to springs at Kirkharle [NZ 0114 8273] and on the north bank of the River Wansbeck [NZ 0111 8400], north-west of Little Harle. Blocks of hard tufa up to 1 m across occur at the former locality.

Made ground

Made ground, in the western half of the district, typically consists of small patches of waste rock and earth from quarry workings, but is extensive in areas around Mootlaw Quarry [NZ 020 755] where quarry waste is used to restore worked out areas of the quarry as part of a continuous programme of landscaping and reinstatement. Within the eastern half of the district worked out opencast coal sites are numerous. These have generally been backfilled and reinstated using waste rock previously excavated as overburden from the workings. In some places spoil from deep coal mine spoil heaps has been employed as backfill; other areas of deep mine coal spoil have been landscaped. Several old quarries have been filled with industrial and domestic waste.

Chapter 3 Applied geology

The Morpeth district includes part of the Northumberland and Durham Coalfield. Centuries of coal mining have had a profound influence on the social and economic history of the district and have left an indelible mark on the landscape. Deep mining of coal has now ended and, although in the past there has been considerable production from opencast mines, there is none at the present. Other mineral products include limestone, iron ore, building stone, sand and gravel, roadstone, and brick and refractory clay. Small trials have been made for lead ore. Limestone is today the only mineral product from the district.

Energy and mineral resources

By far the greatest coal production from the district was obtained from the Westphalian Coal Measures of the Northumberland Coalfield. Although thin coal seams are known within the Dinantian rocks of the district, these have been of minor economic significance. A few of the rather more numerous and thicker coals within the Namurian rocks have been worked on a modest scale in several parts of the district. In the Coal Measures at least 20 named seams are known to have been worked, many of them extensively. Several seams are over 1 m thick. A summary of important aspects of the coals of parts of the district, together with comments on the extent of extraction of individual seams, has been given by Lawrence and Jackson (1990). Throughout the coalfield, coal rank typically increases southwards in response to the higher geothermal gradients associated with the basement strata of the Alston Block, including the Weardale granite. Within the Morpeth district there is an overall increase in coal rank from relatively low in the north to medium rank in the south. Coals from this part of the Northumberland Coalfield were formerly important as household coals and for gas making. More recently they have supplied the power station market both locally and further afield and have, in addition, been blended with other coals for metallurgical and other uses.

Coal mining in this part of Northumberland can claim a long history, extending back over many centuries. However, all underground coal mining within the district has now ceased and, although resources of coal remain at depth, any resumption of underground working is considered extremely unlikely in the foreseeable future. Opencast extraction has also ceased but was important during the past half century; exploration for workable reserves has been undertaken recently.

The Coalbed methane potential of the Northumberland and Durham Coalfield is likely to be low due to low adsorbed methane, the extent of former mining and lack of thick cover (Glover et al., 1993).

A variety of industrial and bulk minerals within the district have been exploited, though today only limestone is regularly worked.

Most of the Visean and Namurian limestones have been worked on a very modest scale producing small amounts of lime mainly for nearby agricultural use. Small quarries, commonly with associated limekilns, may be seen throughout the district. Limestone quarrying today is restricted to one large quarry at Mootlaw, near Matfen [NZ 02 75]. Here the Great Limestone is worked as a source of crushed rock aggregate and as a sub-base for road construction. Much of the exposed outcrop of limestone has today been extracted and the worked ground landscaped. Further reserves are now being extracted beneath an increasing thickness of overburden comprising mainly Namurian mudstones and sandstones.

Dolerite of the Whin Sill provides a good roadstone, used widely in northern England, and was formerly worked at East White Hill Quarry, north of Kirkwhelpington [NY 9948 8576]. Small quarries were formerly worked in Palaeogene dolerite south of Bedlington [NZ 264 815] and on the south bank of the River Wansbeck [NZ 2127 8612] east of Morpeth. A resumption of dolerite quarrying within the district is unlikely.

A few sandstone quarries were formerly worked to provide stone for use both within and outwith the district. These include the quarries around Ingoe [NZ 038 748], at Harlow Hill [NZ 0775 6874], at Dalton [NZ 1140 7190], and at Rivergreen [NZ 1235 8405]. A Coal Measures sandstone formerly quarried at Hartford [NZ 241 800] is said to have provided stone for repairs to the Houses of Parliament and two London bridges. Another Coal Measures Sandstone, above the Haughton (Kirkby's) Marine Band and known locally as the Woodhorn Sandstone, was widely used in the past both as a building stone and for the making of grindstones, many of which were exported to Norway and Sweden (Lawrence and Jackson, 1990a). Considerable amounts of sandstone, some perhaps of sufficient quality to be used for building stone, remain within the district.

Mudstone and siltstone from the Coal Measures have been worked for brick materials, often as a by-product of coal mining, at several places in the Northumberland Coalfield. Further reserves of these materials may be workable in conjunction with opencast coal extraction. Some Quaternary deposits have been worked locally for brick and tile making. Lenses of relatively stone-free, possibly laminated, clay from within the complex glacial deposits which fill the buried valley of the Sleek Burn between Scotland Gate [NZ 250 840] and Red Row [NZ 273 838] were exploited (Lawrence and Jackson, 1990). Bricks and tiles were made from till at Capheaton [NZ 0355 8085] and from alluvium at Belsay [NZ 1130 7825]. A fine row of abandoned kilns remains at the latter site.

Sand and gravel has been worked, mainly on a small scale, from several small pits in the larger areas of superficial deposits.

Ironstone in the form of siderite mudstone ('clay ironstone') nodules is locally common within some Carboniferous mudstones, and is particularly abundant in parts of the Coal Measures. As in other British coalfields, it is likely that these ironstones were worked on a small scale from a very early date. Such ores typically contain up to about 25 per cent metallic iron and, although formerly workable, they are too low grade to attract economic interest today.

Trials for lead ore are known to have been made in two localities within the district; on the south bank of the River Wansbeck at Kirkwhelpington (Smith, 1923), and at Sandybraes, near Capheaton [NZ 0317 7904]. At the latter, small spoil heaps from what appear to be shallow shafts and adits contain a little galena and baryte together with dolerite.

Water resources

Water supplies have been traditionally based on groundwater, particularly in the valleys where springs and shallow wells have exploited the relatively shallow water table. These sources have now largely been abandoned in favour of mains water, and in places by deeper borehole supplies, most of which are still dedicated for private use. All the bedrock strata within the district are, to a greater or lesser degree, water bearing, although none comprises a regionally important or major aquifer. In general, groundwater flows from beneath the higher land to the west in an easterly direction towards the sea. The shallow coal workings and associated disturbed ground of the Coal Measures and parts of the Stainmore Group are likely to exhibit enhanced permeability with a potential for relatively rapid groundwater transport. Although groundwater in the Coal Measures was not a significant problem when the relatively shallow coal workings of the district were being mined, pumping was nevertheless required. There were also several boreholes sunk specifically to assist in dewatering. The most celebrated groundwater source is the group of boreholes, which includes the so-called Abbey Well source that supplies a bottled water and soft drinks plant at Morpeth. Groundwater chemistry in parts of the Coal Measures, along with issues into former mine workings, are typically highly alkaline. Elsewhere in the Coal Measures and Stainmore Group, the groundwater is typically of the calcium-bicarbonate type of near neutral acidity.

With the ending of deep coal mining within the district pumping from collieries has ceased. Water in abandoned coal workings reacts, in the presence of air, with pyrite within the coal and associated rocks, to produce highly ferruginous waters, commonly with a very low pH. Regional recovery of the water table may result in discharges to surface of such acid mine water which may cause serious pollution (see below).

Environmental geology

The range of geological materials within the district exerts an important influence on ground conditions and thus on civil engineering construction and land use. These materials can be divided into three groups: superficial deposits, bedrock and made ground. Local geological and topographical conditions may influence the development of landslipping and flooding.

The noncohesive superficial deposits provide adequate bearing capacity for most domestic or light industrial purposes. Where of low density (loose) they will have a lower bearing capacity. These deposits can be excavated relatively easily; they are diggable but trench supports may be necessary and dewatering may be required in excavations below the water table. When foundations are to be sunk in these deposits site investigation is required to determine their highly variable nature. Cuttings will require drainage measures to remove water from perched water tables and relieve relatively high water pressures in confined aquifers, such as sands and gravels overlain by less permeable clays, to avoid sagging or heave on excavation.

The bedrock in the district is strong with an adequate bearing capacity for domestic and light industrial structures using normal foundations. However, rock mass discontinuities such as joints and faults, and weathering or the presence of groundwater, will significantly reduce the strength of rock. Solution hollows may present a significant hazard in the limestones. These can result in subsidence and may contain abnormally high concentrations of radon gas. On the Coal Measures outcrop, instability should be anticipated associated with mining, for example subsidence, fault reactivation and the collapse of mine workings (Plate 6). Detailed site investigations are required.

Made ground includes backfilled quarries, landfill sites, abandoned opencast coal mines, waste sites, landscaped and disturbed ground. These display a wide range of geotechnical properties. Leachate plumes, solid and liquid contaminants, potentially explosive and noxious gasses and uneven ground settlement have implications for health and foundation construction. These sites should always be thoroughly investigated.

Landslides may occur where the slopes have been oversteepened, both naturally and artificially.

Flooding may follow the cessation of pumping in the deep mines; the regional recovery of the water table may result in acid mine water discharge.

It is essential prior to any development in mining regions that the extent and depth of any abandoned mining areas is determined accurately. However, this can be difficult to ascertain for the oldest workings. Particular hazards in these areas include subsidence, the discharge of acid minewaters from flooded workings, the presence of gases, and the existence of abandoned mine shafts and adits.

Subsidence, which may come about in part by the reactivation of pre-existing faults, may occur suddenly, or gradually and may be induced by such factors as changes in water levels, additional surface loading, vibration from traffic, further mining subsidence, or blasting. The discharge of acid minewaters from flooded workings is a likely consequence of the regional recovery of the water table after the ending of mine pumping; this can result in the discharge to surface of large volumes of acid water. Water may reach the surface in a variety of ways including through abandoned mine openings or boreholes, or through fissured ground. Such minewater can result in contamination to water supplies and rivers, the precipitation of heavy metal and/or iron oxide ochreous deposits and flooding of buildings.

Gases, notably methane but also including hydrogen sulphide, carbon dioxide and other gases or 'black damp' including 'stythe' a local name for a mixture of nitrogen and carbon dioxide may be generated in old workings. All of these gases may be trapped in old workings or porous rocks beneath an impermeable cover such as till. Discharge into the atmosphere can occur through natural fissures, shafts or adits, through collapsed old workings or through porous rocks such as sandstones. Such gas emissions may be more pronounced during periods of low atmospheric pressure. Rising water levels in old workings may displace gas accumulations. Where there is no continuous, impermeable cover the discharge of gases may take place over a wide area giving rapid dilution by the air. In these circumstances the gas emissions may pose little risk to health. In other situations where an impermeable seal, which normally confines volumes of gas, is breached potentially dangerous emissions may occur. The construction of boreholes, sewers and water pipes and other deep excavations can form pathways through which gases may readily pass and in which they may collect. Little information is available on radon concentrations in the district. However, in a recent national assessment Appleton and Ball (1995) considered the outcrops of the Liddesdale and Stainmore groups as areas of moderate radon potential; the Coal Measures outcrop was classified as an area of low to moderate radon potential though with local areas susceptible to moderate or high levels of radon emissions.

A large number of shafts and adits are recorded in the district, but it is likely that many more are present for which no records exist. Many old shafts may be inadequately filled or capped and may present significant hazards. Such abandoned mine entrances may act as pathways for gas and water emissions. The collapse of these openings is also possible. Advice on treatment of disused shafts and adits is available (National Coal Board, 1982).

In the context of nature conservation, a few sites are of interest, for their geological importance; they are designated as Sites of Nature Conservation Importance (SNCI). At the time of writing a number of these and other sites with significant educational value are under consideration for designation as Regionally Important Geological and Geomorphological Sites (RIGS). Details of these may be obtained from the Royal Society for Nature Conservation, The Kiln, Mather Road, Newark NG12 1WT. There are currently no sites designated as geological Sites of Special Scientific Interest (SSSI) within the district.

Information sources

Further geological information held by the British Geological Survey relevant to the Morpeth district is listed below. It includes published maps, memoirs and reports and open-file maps and reports. Other sources include 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 Data Index system in British Geological Survey libraries. This is a developing computer-based system that carries out searches of indexes to collections and digital databases for specified geographical areas. It is based on a geographic information system linked to a relational database management system. Results of the searches are displayed on maps on the screen. The available indexes are as follows:

• index of boreholes
• topographical backdrop based on 1:250 000 scale maps
• outlines of British Geological Survey maps at 1:50 000, 1:10 000, 1:10 560 scales and County Series maps
• chronostratigraphical boundaries and areas from British Geological Survey 1:250 000 scale maps
• geochemical locations
• aeromagnetic and gravity data observation locations
• land survey records

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

Maps

• 1:625 000
• United Kingdom North Sheet, Solid geology, 1979, Quaternary geology, 1977
• 1:250 000
• 55N 04W Borders, Solid geology, 1986 55N 02W Farne, Solid geology, 1988
• 1:63 360
• Sheet 9, Rothbury, Solid, 1934
• Sheet 15, Tynemouth, Solid and drift, 1934
• 1:50 000
• Sheet 8, Elsdon, Solid with drift, 1951 (reprinted 1993); Solid and drift, 1951 (reprinted 1993)
• Sheet 9, Rothbury, Solid and drift, 1977 Sheet 10, Newbiggin, Solid 1997; Solid with drift, 1997
• Sheet 13, Bellingham, Solid with drift, 1980, Solid and drift, 1980.
• Sheet 14, Morpeth, Solid and drift, 2000 Sheet 15, Tynemouth, Solid with drift, 1975 Sheet 19, Hexham, Solid, 1975
• Sheet 20, Newcastle upon Tyne, Solid and drift, 1992
• Sheet 21, Sunderland, Solid 1978; Drift 1978
• 1:10 000 and 1:10 560
• Details of the original geological surveys are listed on editions of the 1:50 000 or 1:63 360 geological sheets. Copies of the fairdrawn maps of these earlier surveys may be consulted at BGS libraries. Geological 1:10 000 and 1:10 560 scale National Grid maps included in whole or in part in the 1:50 000 scale Sheet 14 Morpeth are listed below, together with the initials of the geological surveyors and dates of survey. The surveyors were D W Holliday, D H Land, D A C Mills, G Richardson, J G O Smart, D B Smith, I Jackson, D V Frost, D J D Lawrence and B Young. The maps are not published, but have been deposited in the British Geological Survey libraries in Edinburgh and at Keyworth for public reference and may also be inspected in the London Information Office, in the Natural History Museum, South Kensington, London. Copies may be purchased directly from the British Geological Survey as black and white dyeline copies.

• Applied geological maps
• 1:625 000
• The geographical extent and geological rela- tionships of contamination from natural sources and mining areas is presented on national summary maps to accompany BGS Technical Reports, WP/95/1 to 4. These were prepared to aid the consideration of
• whether the areas affected by 'natural' and mine-related contamination may require consideration by planners, developers and other potential users, especially where new development or remedial work on land is planned.
• Methane, carbon dioxide and oil seeps
• Radon and background radioactivity from natural sources
• Potentially harmful elements from natural sources and mining areas
• Radon, methane, carbon dioxide, oil seeps and potentially harmful elements from natural sources and mining areas
• 1:25 000
• A set of thematic maps prepared for land-use planning is available for the Morpeth– Bedlington–Ashington area. These normally accompany BGS Technical Report, WA/90/14, 1990, but they can be obtained separately. Maps to accompany this report for NZ28/38 are as follows:
• solid geology
• drift geology
• rockhead elevation
• drift thickness
• made and disturbed ground
• shallow mining
• borehole and shaft sites
• engineering geology
• mineral and water resources and extraction (excluding coal)
• geological factors for consideration in land-use planning
• Maps showing structure contours and shallow coal workings accompany the BGS Research Report, 1986. Geology of the Ponteland–Morpeth district.
• 1:10 000
• A set of thematic maps prepared for land-use planning is available for the Ponteland– Morpeth area. These normally accompany the BGS Research Report, 1986 Geology of the Ponteland–Morpeth district, but can be obtained separately. For each of the component 1:10 000 scale maps, NZ17NE, NZ17SE, NZ18NE and NZ18SE the following thematic maps are available:
• Solid and drift geology
• Rockhead elevation
• Drift thickness
• Borehole and shaft sites*
• * There are insufficient boreholes sited on NZ17NE to justify the preparation of a separate map showing boreholes and shafts for that sheet; for this sheet all borehole and shaft sites are shown on the geological map.
• Geophysical maps
• 1:1 500 000
• Colour shaded relief gravity anomaly map of Britain, Ireland and adjacent areas, 1997 Colour shaded relief magnetic anomaly map of Britain, Ireland and adjacent areas, 1998
• 1:625 000
• United Kingdom (North Sheet) Aeromagnetic anomaly, 1972; Bouguer anomaly, 1981
• 1:250 000
• 55N 04W Borders, Aeromagnetic anomaly, 1981; Bouguer anomaly, 1981
• 55N 02W Farne, Aeromagnetic anomaly, 1978; Bouguer anomaly, 1978
• 1:50 000
• Geophysical Information Maps; plot-on-demand maps are available which summarise graphically the publicly available geophysical information held for the sheets in the BGS databases. Features include:
• regional gravity data: Bouguer anomaly contours and location of observations
• regional aeromagnetic data: total field anomaly contours and location of digitised data points along flight lines
• gravity and magnetic fields plotted on the same base map at 1:50 000 scale to show correlation between anomalies
• separate colour contour plots of gravity and magnetic fields at 1:125 000 scale for easy visualisation of important anomalies
• location of local geophysical surveys
• location of public domain seismic reflection and refraction surveys
• location of deep boreholes and those with geophysical logs
• Hydrogeological map
• 1:625 000
• England and Wales, 1977

Books

The various books, memoirs and reports relevant to the Morpeth district are listed in the reference section. Bulletins and reports, including BGS Technical Reports, are not widely available but may be purchased from the BGS or consulted at the BGS and other libraries.

The district lies within the Northern England area of the British Regional Geology series of publications (Taylor et al., 1971), which may be purchased at British Geological Survey and some other bookshops. Other aspects of the general geology can be found in British Geological Survey Memoirs (Fowler, 1936; Day, 1970; Land, 1974; Frost and Holliday, 1980), and Technical and special reports (Jackson et al., 1985; Lawrence and Jackson, 1986; Chadwick et al., 1995; Jones, 1996; Young 1998; Young and Lawrence, 1998). Petrological details appear in Bulletins of the Geological Survey of Great Britain (Harrison, 1968), Reports of the Institute of Geological Sciences (Dunham and Strasser-King, 1982) and Technical Reports (Beddoe-Stephens, 1998). There is biostratigraphical data in Technical Reports (Owens, 1972; Brand, 1987, 1989, 1990, 1991; Dean, 1996; Dean and Brand, 1998; Riley, 1998a, b). Mineral resource information occurs in BGS Economic Geology Memoirs (Dunham, 1990) and special reports (Smith, 1923). Information on non-mineral resources is present in Technical Reports (Glover et al., 1993; Harris, 1993) as is the case for that on Land-use planning (Lawrence and Jackson, 1990a, b; Appleton, 1995a, b; Appleton and Ball, 1995; Appleton et al., 1995). There is information on engineering geology in technical reports (Donnelly, 1998).

Geochemical atlases

The Geochemical Baseline Survey of the Environment (G-BASE) is based on the collection of stream sediment and stream water samples at an average density of one sample per 1.5 km2. The fine (minus 150 m) fractions of stream sediment samples are analysed for a wide range of elements, using automated instrumental methods.

The samples for southern Scotland and northern England were collected between 1977 and 1986. The results (including Ag, As, Ba, Be, Bi, B, CaO, Cd, Co, Cr, Cu, Fe₂O₃, Ga, K₂O, La, Li, MgO, Mn, Mo, Ni, Pb, Rb, Sb, Sn, Sr, TiO₂, U, V, Y, Zn, and Zr in stream sediments, and pH, conductivity, fluoride, bicarbonate and U for stream waters) are published in atlas form (Regional geochemistry of Southern Scotland and part of Northern England. 1993). The geochemical data, with location and site information, are available as hard copy for sale or in digital form under licensing agreement. The coloured geochemical atlas is also available in digital form (on CD-ROM or floppy disc) under licensing agreement. BGS offers a client-based service of interactive GIS interrogation of the G-BASE data.

Documentary collections

BGS holds collections of borehole and site investigation records, which may be consulted and copies purchased at BGS, Edinburgh. Index information for these boreholes has been digitised. The logs are either hand-written or typed and many of the older records are drillers' logs.

• Material collections
• Geological survey photographs illustrating aspects of the geology of the district are deposited for reference in the libraries at BGS, Edinburgh, and BGS, Keyworth. Sheet albums of the more recent photographs are also held in the BGS Information Office, London. The older photographs are in black and white; later photographs are in colour. They depict rocks and sediments in natural or man-made exposures, general views illustrating the influence of geology and examples of mining activity and its effect on the landscape. Copies of the photographs may be purchased as black and white or colour prints, and 50 3 50 mm transparencies.
• The petrological collections of BGS include a small number of rock specimens and associated thin sections from the district. Included are samples of limestone, mudstone, bitumen-bearing calcite and dolerite.
• BGS holds a collection of rock and biostratigraphical specimens from approximately
• 300 boreholes in the Morpeth district. In addition there are more than 1800 registered biostratigraphical specimens collected from surface outcrops, temporary exposures and boreholes throughout the district. For further information on, and access to, the macrofossil collections contact should be made with The Curator, Scotland and Northern England Group Palaeontology Unit, BGS Edinburgh.
• Other relevant collections
• Coal abandonment plans are held by The Coal Authority, Mining Records Department, Bretby Business Park, Ashby Road, Burton-on-Trent, Staffs, DE15 0QD.

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.

Appleton, J D. 1995a. Radon, methane, carbon dioxide, oil seeps and potentially harmful elements from natural sources and mining areas relevant to planning and development in Great Britain. British Geological Survey Technical Report, WP/95/4.

Appleton, J D. 1995b. Potentially harmful effects from natural sources and mining areas; characteristics, extent and relevance to planning and development in Great Britain. British Geological Survey Technical Report, WP/95/3.

Appleton, J D, and Ball, T K. 1995. Radon and background radioactivity from natural sources: characteristics, extent and relevance to planning and development in Great Britain. British Geological Survey Technical Report, WP/95/2.

Appleton, J D, Hooker, P J, and Smith, N J P. 1995. Methane, carbon dioxide and oil seeps from natural sources and mining areas: extent and relevance to planning and development in Great Britain. British Geological Survey Technical Report, WP/95/1.

Beddoe-Stephens, B. 1998. Petrography of dolerite dykes from the Morpeth district. British Geological Survey, Mineralogy and Petrology Short Report, No. M PS R/98/6.

Brand, P J. 1987. Report on the palaeontology of various N CB [British Coal] Opencast Executive boreholes drilled in the area of the deeper boreholes at Broad Law and Tranwell. British Geological Survey Technical Report, P D/87/315.

Brand, P J. 1989. Report on the biostratigraphy of selected boreholes drilled on National Grid sheets N Z28 and N Z38N W, S W examined in connection with the Morpeth Project 09A W. British Geological Survey Technical Report, WH/89/6R.

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Index to the 1:50 000 Series maps of the British Geological Survey

The map below shows the sheet boundaries and numbers of the 1:50 000 Series geological maps. The maps are numbered in three sequences, covering England and Wales, Northern Ireland, and Scotland. The west and east halves of most Scottish 1:50 000 maps are published separately. Almost all BGS maps are available flat or folded and cased.

(Index map)

The area described in this sheet explanation is indicated by a solid block.

British geological maps can be obtained from sales desks in the Survey's principal offices, through the BGS London Information Office at the Natural History Museum Earth Galleries, and from BGS-approved stockists and agents.

Figures and plates

Figures

(Figure 1) Geological succession in the Morpeth district.

(Figure 2) Simplified geology and structure of the district.

(Figure 3) Nomenclature and classification of Carboniferous rocks at outcrop in the Morpeth district.

(Figure 4) Stratigraphy of the Liddesdale Group.

(Figure 5) Stratigraphy of the Stainmore Group.

(Figure 6) Stratigraphy of the Coal Measures

(Figure 7) Coal seams of Coal Measures in the Morpeth district.

(Front cover) Cover photograph: The imposing crenellated tower of Belsay Castle [NZ 0848 7855] is one of the finest surviving examples of a medieval border tower house. Adjoining it on the left is the roofless ruin of the Jacobean manor house. Both the castle and manor house are built of a medium-grained sandstone, quarried locally from a thick sandstone unit that overlies the Corbridge (Lower Felltop) Limestone of Namurian age (D5174). (Photographer T S Bain).

(Rear cover)

(Index map) Index to the 1:50 000 Series maps of the British Geological Survey

Plates

(Plate 1) Synclinal fold in the Great Limestone overlain by undeformed mudstones, Mootlaw Quarry [NZ 0227 7537] (D5168).

(Plate 2) Sandstone between Corbridge and Thornborough limestones, Quarry Gardens, Belsay Hall [NZ 0840 7840] (D5175).

(Plate 3) Shaftoe Grits at Shaftoe Crags [NZ 0515 8163] (D5170).

(Plate 4) Brenkley Opencast Coal site: view down dip (east) of Coal Measures above the Plessey Seam [NZ 206 750] (D3623).

(Plate 5) Down Hill, a large glacially transported raft of Great Limestone [NZ 0030 6851] (L1979).

(Plate 6) Subsidence hollows above old pillar and stall workings, Brenkley [NZ 208 752] (D3729).

Figures

(Figure 7) Coal seams of Coal Measures in the Morpeth district