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Geology of the Huddersfield district. Sheet description of the British Geological Survey 1:50 000 Series Sheet 77 and Huddersfield (England and Wales)

By R Addison, C N Waters, J I Chisholm

Bibliographical reference: Addison, R, Waters, C N, and Chisholm, J I. 2005. Geology of the Huddersfield district. Sheet description of the British Geological Survey, 1:50 000 Series Sheet 77 (England and Wales). 67 pp.

Geology of the Huddersfield district. Sheet description of the British Geological Survey 1:50 000 Series Sheet 77 and Huddersfield (England and Wales)

Authors: R Addison C N Waters J I Chisholm. Contributors: C P Royles, R A Chadwick C Cheney, D E Highley K J Northmore, R M W Musson

Keyworth, Nottingham British Geological Survey, 2005. © NERC copyright 2005. ISBN 0 85272 497 7

The National Grid and other Ordnance Survey data are used with the permission of the Controller of Her Majesty’s Stationery Office. Ordnance Survey licence number 100017897 (2005).

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(Front cover) View of Halifax from Beacon Hill [SE 4103 4254] (Photograph Caroline Adkin; MN39864).

(Back cover)

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Acknowledgements

This Sheet Description was written by R Addison, J I Chisholm, and C N Waters. R A Chadwick and C P Royles contributed to the chapter on Structure and concealed geology. N J Riley identified Carboniferous fossils and G E Strong provided petrographical descriptions for the Carboniferous sandstones; C R Hallsworth determined the heavy mineral assemblages for selected sandstones. The chapter on Applied Geology was compiled from contributions written by K J Northmore on engineering geology characteristics and landslides, by D E Highley on mineral resources and by C Cheney on hydrogeological information. The report has been edited by K Ambrose and A A Jackson; figures were produced by P Lappage BGS Cartography, and page-setting is by C L Chetwyn.

We acknowledge the help provided by the holders of data in permitting the transfer of these records to the National Geosciences Records Centre, BGS Keyworth. We are especially grateful for the assistance provided by members of Local Authorities of Calderdale, Kirklees and the City of Bradford, the Coal Authority, Mineral Valuers Office, Environment Agency, British Rail and civil engineering consultants. The cooperation of landowners, and tenants and quarry companies in permitting access to their lands is gratefully acknowledged.

Notes

Throughout this report the word ‘district’ refers to the area covered by the geological 1:50 000 Series Sheet 77 Huddersfield, and ‘area’ refers to the named geological 1:10 000 Series maps, of which there are 35 covering the entire district (Figure 19).

National Grid references are given in square brackets; all lie within the 100 km squares SE and SD.

Borehole records referred to in the text are prefixed by the code of the National Grid 25 km2 area upon which the site falls, for example (SE12NW). The locations of all the boreholes referred to in the text, along with other selected significant boreholes, are shown in Chapter 7 Information Sources.

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 permission. Contact the BGS Intellectual Property Rights Section, British Geological Survey, Keyworth, e-mail ipr@bgs.ac.uk.

You may quote extracts of a reasonable length without prior permission, provided a full acknowledgement is given of the source of the extract.

Geology of the Huddersfield district—summary

The landscape of the Huddersfield district is dominated, in the west, by the upland moors and gritstone edges of the Millstone Grit. The Millstone Grit formed as deltaic sediments deposited at the mouths of large river systems flowing from the north about 320 million years ago. At first the rivers discharged into a deep, mostly marine basin that lay mainly to the south of the area under survey and the deltas only extended a short distance southwards. As sediments accumulated the deltas extended southwards far beyond the district, forming thick sheets of sand that are now evident as the sandstones which form the typical Pennine edges. The deposition of the sediments shows a marked cyclicity, believed to be controlled by regular, repeated rise and fall in sea level during the Carboniferous.

As the basin filled with sediment, the Carboniferous rivers flowed across a broad and very gently sloping delta plain upon which shallow freshwater lakes and mire swamps developed. In these environments were emplaced the deposits of the Coal Measures of the east of the district, typified by common and extensive coal seams, the buried and compressed remains of the mire-peats. It was the presence of the coal seams, fireclays, ironstone and building stone, most notably the Rough Rock Flags and Elland Flags, which provided the basis for major industries and led to the urban developments of Bradford, Huddersfield and Halifax.

Following the deposition of the Coal Measures no record is preserved of the geological evolution of the district over the intervening years, until the Quaternary Period, when Britain was invaded by the ice sheets of the Pleistocene glaciations. An early glaciation may be represented by minor remnants of sand and gravel deposited by meltwaters, that lie perched above and buried beneath the Calder floodplain or by patchy eroded till deposits outside the margin of the last glaciation. At the peak of the last glacial period the southern margin of the ice sheet lay across the district. In the north-east, which was covered by ice, a thin blanket of till remains. Scouring and erosion by meltwater rivers resulted in the formation of the deep, steep-sided valleys of the Calder and Colne and their many tributaries. In this period also, the steep slopes of mudstone below the gritstone edges were prone to landslips, some of which were of considerable extent.

The structure and concealed geology is described with reference to seismic and geophysical data that is available for the district.

A chapter on applied geologyprovides an insight into the Earth Science issues that are likely to affect planning and development. Legacies from the extraction of natural resources are the difficult foundation conditions and ground contamination of the coalfield areas. Other issues include slope stability, gas emission, water resources and conservation.

(Table 1) Geological succession of the district.

Chapter 1 Introduction

This Sheet Description provides a summary of the geology of the district covered by the geological 1:50 000 Series Sheet 77 Huddersfield published in a Solid and Drift edition in 2001. A simplified map of the bedrock geology is shown in (Figure 1), and the geological succession is summarised in (Table 1). A general description of the geology is provided by the Sheet Explanation for the 1:50 000 Series map, and detailed information can be found in the Technical Reports for the component 1:10 000 scale geological maps.

The district lies within the county of West Yorkshire and includes large areas of the Metropolitan Boroughs of Calderdale and Kirklees as well as small parts of the cities of Leeds and Wakefield in the eastern part of the sheet and Bradford in the north (Figure 2). The main centres of population are Huddersfield, Halifax and south Bradford but numerous towns such as Dewsbury, Brighouse, Batley, Cleckheaton, Heckmondwike and Mirfield are clustered around Huddersfield in the former coalfield area of the eastern part of the district. The western part of the district is more sparsely populated but towns such as Hebden Bridge, Sowerby Bridge, Ripponden and Slaithwaite lie in the sheltered valleys between the Pennine moorlands.

The bedrock (Figure 1) is composed entirely of sedimentary strata deposited during the latter part of the Carboniferous Period, about 323 to 311 million years ago (Gradstein and Ogg, 1996). The oldest strata proved in the Huddersfield district are the Namurian (Upper Carboniferous) Millstone Grit, a thick succession of interbedded sandstone, siltstone and mudstone with minor thin coal seams, fireclays and ironstones. The mudstone includes horizons that are rich in marine fossils and provide useful marker beds that enable the subdivision and correlation of the strata. It is inferred from geophysical evidence and regional successions, that Dinantian (Lower Carboniferous) limestones and mudstones lie beneath Namurian strata. The Millstone Grit crops out over most of the western part of the district where it forms the high moorlands of Blackstone Edge, Buckstones Moss, Soyland Moor, Great Manshead Hill, Withens Moor, Erringden Moor and Midgley Moor. The high silica and low lime and nutrient contents of the rocks produce poor acidic soils that support the characteristic Pennine vegetation of heather and sparse grass on a blanket of peat. The sandstones, such as the Rough Rock and Huddersfield White Rock, form dissected west-facing escarpments with extensive dip slopes reflecting the shallow easterly dip of the strata. The Millstone Grit is overlain by the Coal Measures, a succession of mudstone, siltstone and sandstone with subordinate coal seams fireclay and ironstone of Langsettian (Westphalian A) to early Duckmantian (Westphalian B) age. The Coal Measures crop out over the eastern part of the district and generally form lower ground although sandstones such as the Elland Flags and Thornhill Rock form imposing escarpments. The Coal Measures have yielded abundant minerals such as coal, fireclay, brickclay, pyrite, ganister, ironstone and dimension stone, which were worked from Roman times and supported significant development in the Middle Ages. In the 19th and 20th centuries mineral exploitation stimulated the early growth of the urban areas, and although mineral extraction is much reduced in scale, the fireclay, common clay, flagstone and dimension stone industries are still significant contributors to the local economy.

History of research

The district covered by Sheet 77 Huddersfield was originally surveyed on the 1:10 560 scale County Series sheets of Yorkshire by J C Ward, J R Dakyns, R Russell, C Fox Strangways, W H Dalton, J Lucas, E Hull and A H Green, and published on the 1:63 360 scale [Old Series] Sheet 77 SE in 1870 and 1874. The primary survey account of the geology of the district is given in a general description of the Yorkshire Coalfield by Green et al. (1878). The district was resurveyed on the 1:10 560 County Series sheets by D A Wray, J V Stephens, C E N Bromehead, W Edwards and W Lloyd in 1921 to 1925 and published as a Solid and Drift edition in 1927. Sheet 77 was reprinted in 1949 and 1963 and reconstituted, with minor amendments by H Johnson and E G Smith, to the 1:50 000 scale in 1978. The accompanying memoir for the district (Wray et al., 1930) provides a detailed account of the geology with descriptions of localities and regional variations.

This Sheet Description provides a summary of the geology with indication of amendments or additions to the existing memoir. It is based on a further resurvey carried out at 1:10 000 scale, mainly in the period 1993 to 1999. Some earlier work was carried out as part of the applied geological mapping of Leeds (part funded by the Department of the Environment), and was described by Lake et al. (1992). Parts of the Huddersfield Sheet in the northern part of the district were surveyed as part of the Bradford Geological Mapping Project; the Carboniferous and Quaternary stratigraphy and applied geology are described, with accompanying thematic maps and geological databases, by Waters et al. (1996b).

The second resurvey has used recent advances in Silesian geology to make amendments to previous surveys. Following the work of Ramsbottom et al. (1978), various workers have addressed regional and local aspects of the cyclicity (Holdsworth and Collinson, 1988), sedimentology (Bristow, 1988; Collinson, 1988; Guion and Fielding, 1988; Chisholm, 1990; Guion et al., 1995; Chisholm et al., 1996; Waters et al., 1996a; Hallsworth and Chisholm, 2000). The palaeontology of the Namurian and Westphalian has also been described (Trueman and Weir, 1946; Calver, 1968a, b; Eagar, 1947, 1952, 1956, 1974a, b; Eagar et al., 1985). Leeder (1982) provided insights into the regional structural history of the Carboniferous.

Other than during the geological surveys, the Quaternary deposits have received little attention from geological researchers. Works of note include Jowett and Muff (1904) on ‘glacial overflow’ channels and Raistrick (1934) on glacial retreat stages across the Pennines. Other minor work includes Simpson (1901), Wray (1915), and Woodhead (1917).

Chapter 2 Dinantian

Dinantian strata of the Pennine region were deposited during active rifting of the basement, so occupy a system of half-graben basins and tilt-block highs, with large variations in thickness and facies (Kirby et al., 2000). In the Huddersfield district they are entirely concealed beneath Namurian and Westphalian post-rift deposits and their lithology and structure have been interpreted from limited seismic information. They lie within the Huddersfield Basin (Lee, 1988) where interpreted depths to Caledonian basement increase steadily from less than 2000 m at the western edge of the district to over 3000 m in the east (Figure 3) and (Figure 4). Along the line of section, the Dinantian succession is interpreted to have a maximum thickness approaching 1400 m.

The Huddersfield Basin is deeper in the north-east where it includes the north-westerly extension of the Gainsborough Trough. It is bounded to the north-east by the Morley-Campsall line, a north-west-trending set of down to-the-south normal faults, to the north of which lies the Morley-Campsall High, part of the Askern-Spital High. The Morley-Campsall Fault, together with the South Craven and Askern-Spital faults, form part of a more extensive structure that lies along the south-west margins of the Furness-Ingleborough-Wash-Norfolk ridge (Wills, 1978) and probably separates regions of differing pre-Carboniferous basement geology (Kirby et al., 2000, p.21). The nature of this basement boundary has been discussed at length by Lake (1999) for the Wakefield district. To the west, the Huddersfield Basin is bounded by the structurally complex north-trending Pennine Line with north-north-west trending splay faults (Evans et al., 2002) that intersect the far south-west of the district. The Holme Fault (Lee, 1988) is a large, east-trending, down-to-the-north, syndepositional normal fault that lies about a kilometre to the south of the district. It forms the northern margin of the Holme High, a prominent Dinantian structural elevation characterised by basement depths in the range 500 to 1500 m (Kirby et al., 2000), and capped by Dinantian (possibly Courceyan to Arundian) limestones (Evans and Kirby 1999). As imaged on seismic data, these appear to extend northwards across the Holme Fault into the south-west corner of the district, where they form a massive build-up with an irregular top (Figure 4b). Parallel-bedded Dinantian strata of more basinal facies (presumed mudstone and interbedded limestone) onlap southwards against the undulating surface of the limestone build-up.

Chapter 3 Namurian

Namurian rocks crop out over much of the west of the district and occur at depth beneath Westphalian rocks in the east. They belong to the Millstone Grit Group, a lithostratigraphical unit comprising interbedded mudstone, siltstone and sandstone with minor coal seams. Only the sandstone is widely exposed. Seismic data suggest that the total thickness of Namurian strata in the district is about 1000 m, of which the highest 525 m are exposed at outcrop. Boreholes (Figure 5a) and (Figure 5b) suggest that this higher part of the Namurian succession shows little variation in thickness across the district from east to west, but some northward thinning into the Bradford district.

During the Namurian Epoch, approximately 320 million years ago, northern England lay within a large, actively subsiding basin connected to the sea. Rivers draining ultimately from lands to the north carried sediment to feed extensive deltas that built out into the basin. Coarser grained sediment, deposited in fluvial channels, levées, deltas and submarine fans, eventually lithified as sandstone, whereas mud and silt settled in areas of standing water and deeper marine environments, and lithified as fissile or massive mudstone and siltstone.

The Namurian Epoch is divided into seven stages (Table 2), which are in turn subdivided into chronozones (Ramsbottom et al., 1978). The boundaries of these chronostratigraphical subdivisions are recognised by the presence of diagnostic ammonoid (goniatite) faunas.

Millstone Grit Group

The Millstone Grit succession in the Pennine region consists of a series of sedimentary cycles (cyclothems), which are now generally believed to have resulted from sedimentation during cyclical glacio-eustatic variations in sea level, superimposed on subsidence of the basin (Leeder, 1988). Each cycle begins with mudstone, near the base of which are beds containing marine faunas. These marine bands range from a few centimetres up to 7 m or more in thickness, and each generally contains a distinctive and diagnostic faunal assemblage. They can be recognised regionally, and are important marker horizons. They are inferred to have been deposited at times of high global sea level. (Table 2) lists the principal bands present in the Pennine region. The marine mudstones commonly pass up into unfossiliferous mudstone and siltstone, and then into sandstone, each upward-coarsening unit representing an advance of the delta. Pelagic environments were therefore replaced by delta slopes, and finally by distributary channels of the delta top. The delta-top environments were colonised by plants, especially during times of lowered sea level, leading to the development of soils and deposits of peat. Once subjected to lithification the soil horizons became seatearth and the peats compacted to coal. This pattern of deposition was repeated with each rise and fall in sea level.

Depositional models have been provided by McCabe (1978) and Hampson (1997) for the Kinderscoutian part of the succession, by Wignall and Maynard (1996), Brettle (2001) and Brettle et al. (2002) for the Marsdenian, and by Bristow (1988) and Hampson et al. (1996) for the Yeadonian. Collinson (1988) has reviewed the sedimentation of the Millstone Grit as a whole.

The Millstone Grit exposed in the district comprises about 525 m of interbedded mudstone, siltstone and sandstone. The highest 500 m are also proved in boreholes (Figure 5a) and (Figure 5b). The sandstone units are generally similar to one another in their petrographical and sedimentological features, and are mainly distinguished by their position relative to the marine faunal bands described above. The sandstone nomenclature is broadly the same as that used during the previous survey, although some names have been changed to conform with those used in the adjoining Bradford district (Waters, 2000). The use of the terms ‘grit’ and ‘rock’ are maintained for sandstone names where usage is well established in the literature; grit and sandstone are considered synonymous in the following text.

Previous surveyors of the district used the term ‘Millstone Grit Series’ to include all the strata exposed below the Coal Measures. They divided their ‘Millstone Grit Series’ into four parts, mainly on the basis of goniatite faunas, and adopted the terms ‘Sabden Shales’, ‘Kinderscout Grits’, ‘Middle Grits’ and ‘Rough Rock Series’ (Wray et al., 1930). The three highest correspond in a general way to the stage names Kinderscoutian, Marsdenian and Yeadonian, which are used as the section headings in this account. The Sabden Shales exposed in the district are now included in the Kinderscoutian, but not separately named. A report on the outcrop area (Waters, 2001) provides the basis for most of the details described here.

Kinderscoutian strata (R₁)

Kinderscoutian strata are at least 230 m thick in the district, and include several thick sandstones. The lowest beds exposed are predominantly argillaceous and are seen in the north-west of the district in Hebden Water, Crimsworth Dean, the upper Calder valley, on Stoodley Pike and in the vicinity of Withens Clough Reservoir. In Halifax they were penetrated in Clark Bridge Mills borehole (Figure 5a).

Several sandstones have been mapped within the argillaceous succession. The lowest is an unnamed bed 5 to 10 m thick, which has been traced from Crimsworth Dean to Charlestown and Mytholmroyd. It ranges from very fine grained to very coarse grained or granular, and is generally upward-fining. Near Mytholm Church [SD 985 274] it has a strongly fluted base eroded into underlying dark siltstone.

At Crimsworth Dean about 70 m of mudstone interbedded with siltstone and very fine-grained sandstone lie between the unnamed sandstone described above and the Lower Kinderscout Grit. Three marine bands have been recorded. The oldest occurs about 7.5 m above the unnamed sandstone, and was described by Spencer (1898) and Bisat and Hudson (1943). Lloyd and Stephens (1927) and Wray et al. (1930, p.26) described two higher marine bands at Black Scouts. They are about 4.7 m apart, the upper lying about 20 m below the base of the Lower Kinderscout Grit. These two higher beds are classified provisionally as Reticuloceras reticulatum (R_1c) and are likely to be R_1c1 and R_1c2. The lowest bed had not yielded a diagnostic fauna.

The Todmorden Grit of the Rochdale district also lies in this argillaceous succession, as it is underlain and overlain by Reticuloceras reticulatum marine bands (Wright et al., 1927; Bisat and Hudson, 1943). Within the district it is a laterally extensive fine to coarse-grained sandstone. At Crimsworth Dean and at Parrock Wood the sandstone is estimated to be about 5 m thick whereas in the vicinity of Hebden Bridge and Mytholm it is up to 60 m thick and forms isolated crags at Horsehold Scout and Cat Scout. These may be cross-sections of infilled channels cut into unexposed siltstone (Chisholm, 1995). In the Hebden Water near Hardcastle Crags, a massive sandstone has a sharp erosive base showing load casts, tool marks and flutes, and is interpreted as the deposit of high-energy turbidity currents. It occupies north-south-orientated channels, which are inferred to be submarine features cut into the delta slope of the large Kinderscoutian fluviodeltaic system.

The succession between the Todmorden Grit and Lower Kinderscout Grit is dominated by silty micaceous mudstone and siltstone with thin beds of fine-grained sandstone. In the Withens Moor area [SD 975 223], Bisat and Hudson (1943) described a thick succession comprising about 46 m of fissile mudstone overlain by about 53 m of interbedded fissile mudstone, siltstone and subordinate sandstone, which they referred to as the Lower and Upper Todmorden Shales, respectively. In the Lower Todmorden Shales, they described the Spittle Clough Marine Band, which may equate with the highest of the Reticulocerasreticulatum marine bands (R_1c3). In the Upper Todmorden Shales they described the Healey Clough A Marine Band, about 7.5 m below the top of the shale, with Reticuloceras coreticulatum. If, as seems likely, this last is the R. coreticulatum Marine Band (see below) it would suggest that the great thickness of mudstone present here is a consequence of the lateral passage into mudstone of the main lower leaf of the Lower Kinderscout Grit.

The Lower Kinderscout Grit is exposed widely in the district and is formed of several interconnected leaves that show dramatic thickness variations. It is generally poorly sorted, medium to very coarse grained, locally granular and with small quartz pebbles; it is typically upward-fining, thickly bedded and cross-bedded. Individual cross-bed sets can be up to 15 m thick, as exposed at Hell Hole Quarry, Heptonstall (McCabe, 1977, fig. 5). The succession equates broadly with a group of three sandstones in the Bradford district, the Addingham Edge Grit, Long Ridge Sandstone and Doubler Stones Sandstone (Waters, 2000), but because of limited biostratigraphical control it has not proved possible to continue the Bradford nomenclature southwards into this district. Partings between sandstone leaves generally comprise grey siltstone and mudstone with thin, fine grained sandstone beds. The mudstones may contain marine faunas, the most notable being the Reticuloceras coreticulatum Marine Band (R_1c4), which underlies the highest leaf of the Lower Kinderscout Grit. This is recorded at outcrop in Paddock Beck, Crimsworth Dean (Waters, 2001), at Horodiddle, and underground in the water tunnel beneath Midgley Moor (Wray et al., 1930). The main sandstone leaves are commonly overlain by seatearths with thin coals, for example at Stoodley Pike and in the Noah Dale borehole (Figure 5a). East of Pecket Well [SD 9986 2893] a coal, up to 0.3 m thick, rests on the highest sandstone leaf and was worked locally.

Note that as a result of the identification of the Butterly Marine Band during this survey, the separation of the Upper and Lower Kinderscout Grits is made at a horizon higher within the grits than that used by Wray et al., (1930). As a consequence, the sandstone described by those authors as the lower leaf of the Upper Kinderscout Grit is referred to here as the upper leaf of the Lower Kinderscout Grit.

In the west of the district, in the Withens Moor area, the total thickness of the Lower Kinderscout Grit ranges from 5 to 75 m. Thinner sequences appear to occur where channelling at the base of the Upper Kinderscout Grit has cut below the level of the Butterly Marine Band and removed some of the Lower Kinderscout Grit. In the south-west of the district, around Blackstone Edge and Rishworth, there are two thick leaves of coarse-grained sandstone with a thin, fine-grained sandstone leaf at the top of the succession. The total thickness is estimated to be at least 90 m. In the Huddersfield area, in the Phoenix Mills borehole (Figure 5a), the Lower Kinderscout Grit is 84 m thick, consisting of at least four sandstone units from 3 to 27 m thick separated by mudstone bands up to 11 m thick. Two of these have yielded faunas that may represent the R_1c3 and R_1c4 marine bands. In Bower’s Mill Borehole (Figure 5b) the marine brachiopod Orbiculoidea was recorded just below the lowest sandstone.

Over much of the western part of the district, the lowest leaf is considerably thicker than the others but in the northwest this leaf thins both eastwards from Hebden Bridge and northwards from Cragg Vale [SE 005 233] towards Mytholmroyd. The base of the lowest leaf is exposed at Lumb Falls, Crimsworth Dean, where it comprises 3 m of medium to coarse-grained cross-bedded sandstone resting sharply on grey silty mudstone (Wray et al., 1930, plate III).

The highest leaf of the Lower Kinderscout Grit shows marked thickness variation in the north-west of the district. It is absent from the northern part of Luddenden Dean and north of Pecket Well, but is about 30 m thick along the southern edge of Midgley Moor. It appears to have an inverse relationship to the thickness of the main lower leaf.

The succession between the Lower and Upper Kinderscout Grits comprises up to 19 m of mudstone, siltstone and fine-grained sandstone with thin coals. In the south-west of the district, the succession is about 5 m thick, but is thin or absent in the Rishworth area. In the Mytholmroyd area the Upper Kinderscout Grit rests on, or a few metres above, the thin coal at the top of the Lower Kinderscout Grit. The thickest development is seen in the Noah Dale Borehole where the succession comprises three upward-coarsening cycles each about 6 m thick (Figure 5a) and consisting of coal and black mudstone overlain by dark grey mudstone and siltstone passing up into very fine grained sandstone. Similar cycles have been observed in detailed logs of the Manshead Tunnel boreholes (Figure 6). In places this interval includes a Lingula band designated as the Butterly Marine Band (Bromehead et al., 1933; Aitkenhead and Riley, 1996). This horizon has been recognised in the Manshead Tunnel boreholes and in boreholes in the Huddersfield area (Figure 5) and (Figure 6).

The Upper Kinderscout Grit as described here was referred to as the upper leaf of the Upper Kinderscout Grit during the previous survey of the Huddersfield district (Wray et al., 1930). It is equivalent to the High Moor Sandstone of the Bradford district (Waters, 2000).

The Upper Kinderscout Grit varies from very fine grained to very coarse grained with granules, and is crossbedded or massive; it is broadly upward-fining, becoming very micaceous and very thinly bedded towards the top. It shows marked variations in thickness, as in the Sowerby and Withens Moor areas where it ranges from 0 to 40 m, and may form two leaves. The top of the sandstone is marked typically by a ganister or other seatearth.

The thickest developments of the Upper Kinderscout Grit are in the Hebden Bridge, Withens Moor, Mytholmroyd and Sowerby areas, and comprise very coarse-grained sandstones, probably infilling a fluvial channel. Erosion at the base of this channel appears to have removed one or more leaves of the underlying Lower Kinderscout Grit. In the south-west, the sandstone is fine to medium grained throughout, micaceous and flaggy or very thinly bedded with common Pelecypodichnus. Boreholes in the Huddersfield area record up to about 20 m of sandstone, proved to be Upper Kinderscout Grit by the presence of the overlying Bilinguites gracilis Marine Band (Figure 5) and (Figure 6).

Marsdenian strata (R₂)

Marsdenian rocks outcrop over much of the western part of the district, notably at Midgley Moor, Sowerby, Outlane and Slaithwaite Moor. They comprise sandstone, mudstone and siltstone, with a total thickness proved in the district of up to 200 m.

The Bilinguites gracilis Marine Band (R_2a1) marks the base of Marsdenian strata. This marine band corresponds with that of Reticuloceras reticulatum mut α. of Bisat (1924) and Wray et al. (1930). These authors recognized local variations, with an early mutation and late mutation α. The latter, intermediate between mutation and mutation ß, is dominant in, and restricted to, the south and west of the district, including Dry Clough, Dean Head Clough and Hard Head Clough.

The marine band is typically underlain by a 2 to 3 m thick, upward-coarsening succession of micaceous silty mudstone, with abundant Cordaites, passing up through siltstone, to fine to medium-grained bioturbated sandstone with rare Sanguinolites, indicating deposition within a restricted marine environment. These measures are exposed at Castle Shore Clough and Dry Clough, Linsgreave.

The marine band varies from about 1.5 m thick in the south of the district, as exposed at Castle Shore Clough, to about 7 m thick in boreholes around Huddersfield and Halifax. The thickest development commonly occurs where the underlying Upper Kinderscout Grit is relatively thin. In these sections, the marine band comprises dark grey, finely laminated mudstone with the diagnostic B. gracilis, and with Dunbarella and Posidoniella commonly present near the top and base.

Regionally, up to three Bilinguites bilinguis Marine Bands (R_2b1, R_2b2, R_2b3) are recognised in the beds above the Bilinguites gracilis Marine Band, though in the Huddersfield district only one (presumed to be the middle one, R_2b2) commonly contains B. bilinguis. This is the band that lies immediately above the East Carlton Grit. B. bilinguis was called Reticuloceras reticulatum mutation ß (type form) by Bisat (1924) and Wray et al. (1930).

A lower marine band, containing early mutation ß, appears to equate to the R_2b1 band and occurs about 6 to 7 m above the Bilinguites gracilis band in the south-west of the district, as at Castle Shore Clough and Dry Clough. Assemblages of Lingula, marine bivalves and Planolites that occur in mudstone a few metres above the B. gracilis Band in some borehole sections (Figure 5) and (Figure 6) may also represent the R_2b1 band or, perhaps, the top part of the B. gracilis Marine Band.

The R_2b3 horizon may be represented in the Colne Road Mills Borehole (Figure 5a) by a band containing Reticuloceras sp. in mudstone about 23 m above the R_2b2 band. A 14.6 m-thick marine succession above the East Carlton Grit in Shaw’s Paper Mill Borehole (Figure 5b) probably represents a combination of R_2b2 and R_2b3.

The Readycon Dean Flags and East Carlton Grit are now defined as belonging to a single fluviodeltaic system, underlying the R_2b2 band (Brettle et al., 2002). Wray et al. (1930) equated the Readycon Dean Series in the south of the Huddersfield district with the Scotland Flags in the north. This interpretation was questioned by Wignall and Maynard (1996), who correlated the Readycon Dean Flags with the East Carlton Grit of the Bradford district, which lies beneath the R_2b2 band, and suggested that the Scotland Flags are younger, occurring above the R_2b2 band. This correlation is accepted here, and the name Readycon Dean Flags is restricted to a fine-grained component of the former Scotland Flags, interpreted as distal mouth-bar deposits, while the overlying coarser grained proximal mouth-bar and fluvial channel deposits of the same river system are referred to the East Carlton Grit. The name Scotland Flags is no longer used in the Huddersfield district.

The Readycon Dean Flags are limited to areas south of the Calder valley. They occur about 20 to 50 m above the B. gracilis Marine Band in the south and are up to 15 m thick. The flags comprise thin beds of very fine to fine-grained, micaceous, planar laminated sandstone interbedded with micaceous siltstone and silty mudstone; they are mapped where sandstone beds comprise over about 30 per cent of the strata present. These beds are well exposed at Tom Clough, Deanhead Clough and Cob Clough. The flags are 20 m thick in Bowers Mill Borehole (Figure 5b), whereas in Bankfield Mills (Mold Green) Borehole, Wray and Melmore (1931) recorded 34 m of sandstone and fissile sandy mudstone with ganister and a trace of coal at the top. In the south-west of the district, the East Carlton Grit forms a prominent escarpment on Rishworth Moor. It comprises a highly variable sandstone, typically fine to medium grained, micaceous, cross-bedded, ripple cross-laminated, and thinly planar bedded. It is estimated to be between 5 and 15 m thick in this area, and the base is usually gradational, as at Slaithwaite Reservoir.

In the Sowerby Bridge area, the sandstone is medium to very coarse grained and trough cross-bedded, varying in thickness from 8 to 26 m. The thicker figure was proved in the Stone Trough Brewery Borehole (Figure 5b) where a 20 m-thick sandstone is overlain by about 6 m of interbedded sandstone and mudstone with two coals, 0.15 and 0.3 m thick. A section in the sandstone at Sowerby Bridge Cemetery was described in detail by Wignall and Maynard (1996, fig.13).

The East Carlton Grit and Midgley Grit are separated by mudstone and siltstone, estimated to be 5 to 15 m thick in the south-west, increasing to up to 30 m in the south. In the north of the district the two sandstones are separated by a 20 m-thick succession which includes a further sandstone, inferred to correlate with the Woodhouse Flags of the Bradford district. The wide variation in thickness may reflect irregular levels of erosion at the base of the overlying Midgley Grit.

In the northern part of the Mytholmroyd area, the supposed Woodhouse Flags are 10 m thick. At Wainstalls, a 6 m-section comprises fine-grained micaceous sandstone, thickly bedded at the top, thinly bedded and laminated at the base. There are also exposures of fine-grained, flaggy, micaceous sandstone, thinly planar bedded or cross-bedded and with some Pelecypodichnus traces, along the southern margin of Midgley Moor.

The Woodhouse Flags are also believed to occur in the Noah Dale Borehole (Figure 5a) as a 17 m-thick succession of typically upward-fining beds of fine-grained sandstone to siltstone. The sandstones appear to be heavily bioturbated and the siltstones display common Olivellites traces. This sequence is interpreted as a proximal mouth-bar deposit, overlain with an erosional boundary by the Midgley Grit. It is possible that the Woodhouse Flags lie between the R_2b2 and R_2b3 marine bands, and that erosion above the flags has normally removed the higher band before deposition of the Midgley Grit.

The Midgley Grit (MgG) forms prominent escarpments in the district, such as Buckstones Moss, Slaithwaite Moor, Manshead End, Dog Hill, Pike End, Moselden Height (Plate 1) and Midgley Moor, the type locality. The name Pule Hill Grit, used by Wray et al. (1930) for the same bed in the south of the district, is no longer needed. In Lancashire the same sandstone is normally known as the Gorpley Grit, but the limited outcrop in the extreme southwest of the Huddersfield district on Blackstone Edge and at Denshaw has been named Midgley Grit to conform with the remainder of the sheet.

The Midgley Grit is estimated to be between 15 and 25 m thick in the southwest, up to 40 m in the south, but only 7 to 15 m at Midgley Moor. It is generally a coarse to very coarse-grained, quartzo-feldpathic sandstone that is cross-bedded to massive with common log impressions and mudstone intraclasts. The base of the sandstone is typically sharp and erosive. Internal erosion surfaces are also common.

Towards the south of the district, for instance at Bank Nook, beds of fine to medium-grained micaceous sandstone become more abundant. At Nether Wood large-scale cross-bedding is present in co-sets up to 4 m thick. At White Rock Quarry, the lower part of the succession is medium grained, tabular cross-bedded to massive, overlain with a sharp, erosive base by coarse-grained, thickly cross-bedded sandstone. In the Bankfield Mills (Mold Green) Borehole the Midgley Grit is 15 m thick, fine grained, and overlain by seatearth clay and a thin coal (Wray and Melmore, 1931). In the nearby Phoenix Mills Borehole, the sandstone is 21 m thick (Figure 5a).

In the south of the district, the Midgley Grit is divided into two leaves by a mudstone parting up to 7 m thick, as seen in the borehole at Albion Mills, Golcar (Figure 5b). At outcrop near Slaithwaite the mudstone parting has yielded a marine fauna including Lingula and bivalves (Wray et al., 1930, p.39). The fauna is probably referable to the Bilinguites eometabilinguis Marine Band (R_2b4). In the Bradford district, a Lingula band believed to be the same bed is found immediately above the Midgley Grit, and 1 to 2 m below the Bilinguites metabilinguis Marine Band (R_2b5). It is therefore probable that the upper sandstone leaf encountered in the Golcar Borehole is a local development only. It is well exposed at Golcar where it comprises about 5 m of fine to medium-grained well bedded sandstone.

Immediately above the Midgley Grit is a thin, unnamed coal, up to 0.3 m thick around Sowerby Bridge and Barkisland Mills [SE 066 197], where it was thick enough to have been worked (Wray et al., 1930).

The sequence between the coal on top of the Midgley Grit and the base of the Guiseley Grit is dominated by mudstone and micaceous siltstone between 5 and 25 m thick. At or near the base of the interval is the Bilinguites metabilinguis Marine Band (R_2b5), which has yielded faunas including Reticuloceras reticulatum mut. ß, late mut. ß and early mut γ. (Bisat, 1924; Wray et al., 1930). The marine band was seen during the current survey in Highlee Clough and was proved during the previous survey at Cupwith Hill, Blake Clough, and Butts Clough (Wray et al., 1930). The marine band is provisionally correlated with an occurrence in the Bankfield Mills and Phoenix Mills boreholes (Wray and Melmore, 1931; Figure 5a) where it serves to define the nomenclature of the sandstones. In the M62 road cut, Moselden Heights, the Midgley Grit is overlain by a 0.5 m thick claystone with abundant B. metabilinguis and Dunbarella, referred by Church (1994) to the R_2b5 band. A Lingula band near the top of Shaw’s Paper Mill borehole (Figure 5b), currently referred to the R_2b5 band, could belong to the R_2b4 band.

The Guiseley Grit was formerly referred to variously as Nab End Sandstone or Beacon Hill Flags in the Huddersfield district (Wray et al., 1930), but the name Guiseley Grit is now preferred. The sandstone in Nab End Quarries, the type locality of the Nab End Sandstone, is here considered to belong to the Midgley Grit. A sandstone mapped at this horizon in the extreme south-west of the Huddersfield district was formerly called by its Lancashire name, Hazel Greave Grit, but the term Guiseley Grit is now used in that area also.

The thickness of the Guiseley Grit varies from 5 to 22 m. It is typically fine to medium grained, flaggy and micaceous, cross-bedded and ripple cross-laminated. At Wham Quarry, the sandstone beds are interleaved with thin beds of laminated silty mudstone, the lowermost sandstone containing abundant Pelecypodichnus traces. The upper part of the Guiseley Grit is locally coarse grained, as at Marsh Quarry and Lumb Hill Quarry. In the central part of the Sowerby area, the sandstone forms prominent dip slopes, and has been worked in numerous small quarries.

A thin coal, the Lower Meltham Coal, is present locally on top of the Guiseley Grit. The sequence above, up to the base of the Huddersfield White Rock, is dominated by mudstone with the Bilinguites superbilinguis Marine Band (R_2c1) near the base. This was recorded (as Reticuloceras reticulatum mut. ) at Butts Clough, Rishworth (Bisat, 1924, and Wray et al., 1930), and it was proved in a section at Caty Brook, Wainstalls [SE 045 289] by Benfield (1969) who estimated that it lay about 15 m below the base of the Huddersfield White Rock. The Verneulites sigma Marine Band (R_2c2) (formerly the band of Gastrioceras sigma) was not noted during the current survey but was described by Wray et al. (1930) as occurring just above the R_2c1 band around Black Brook, Barkisland. It is probably present in the Fairweather Green and Sandoz boreholes, to the north of the district (Figure 5b).

In the vicinity of Slaithwaite, the mudstone above the marine bands contains an unnamed sandstone about 5 m thick. This, as exposed at Bank End [SE 0918 1553], is pale grey, micaceous, fine grained, planar bedded and ripple cross-laminated beds have sharp bases with small scours.

The Huddersfield White Rock sandstone of the district ranges from fine grained, thinly planar bedded and ripple cross-laminated, to medium to very coarse grained and cross-bedded. It forms prominent escarpments and long, even dip slopes to the west of Huddersfield, around Outlane Moor and Golcar. The name is used here for sandstones previously referred to as Warley Rock (Wray et al., 1930), and to replace the Lancashire name of Holcombe Brook Grit.

In the south of the district, the sandstone is 20 m thick, but around Outlane it occurs as two leaves and is up to 30 m thick. In the north, the sandstone is 10 to 15 m thick, forming a prominent feature on the eastern side of Luddenden Dean and a dip slope on Warley Moor. South of Mixenden it is exposed in the Hebble Brook valley where parallel bedded fine to medium-grained micaceous sandstone forms 5 m-high cliffs near Clough Bank Beck and Riding Bridge. The sandstone thins to the north, as shown by boreholes 11 and 12 in Bradford (Figure 5b).

Benfield (1969) described a complex of fluvial, deltaic and intertidal environments of deposition for the sandstone, and identified two main distributary channels, one north of Halifax and one west of Huddersfield. He inferred that the Huddersfield district was located on the northern side of a deltaic complex that advanced from east to west across the Pennine region. Around Golcar, channel sandstone rests with an erosive contact upon sandstone of mouth bar facies. In the Slaithwaite area, for example in Wild Brow Quarry, channel sandstone is underlain by intertidal sandstones. In the north of the district, at Caty Brook, a thinner, delta-flank succession was described by Benfield. Farther north, on Warley Moor, coarse-grained channel sandstone up to 12 m thick forms a prominent crag at Stony Edge.

Above the Huddersfield White Rock is a variable sequence up to 10 m thick of mudstone and siltstone with a thin sandstone and one or two thin coals (Figure 5a) and (Figure 5b). At outcrop in the present district the sandstone has normally been included in the Huddersfield White Rock, though it was distinguished as the Meanwood Sandstone in the Sandoz Borehole (Figure 5b) by Hudson and Dunnington (1938). The higher of the two coal seams, which lies at the top of this mixed sequence, is the Upper Meltham Coal. In the vicinity of Pole Hill a single seam of coal is about 0.3 m thick and was worked from bell pits and shafts. In the Sowerby Bridge area, the coal is proved to be 0.2 to 0.3 m thick. In the area around Halifax, Elland and Ovenden it rests on a thin seatearth directly overlying the Huddersfield White Rock, as in the Stone Trough Brewery Borehole (Figure 5b), whereas to the south-east of Sowerby Bridge it lies up to 9 m above the top of the Huddersfield White Rock.

Above the Upper Meltham Coal lies a thick succession of mudstone with several marine bands (Figure 5a) and (Figure 5b). The lowest 5 to 7 m of the mudstone lie below the Cancelloceras cancellatum Marine Band, so belong to the Marsdenian Stage. They contain two Lingula bands and a nonmarine bivalve fauna.

Yeadonian strata (Gl)

The base of rocks of Yeadonian age is defined at the base of the Cancelloceras cancellatum Marine Band (Gla1), which lies a few metres above the Upper Meltham Coal (see above). The Cancelloceras cumbriense Marine Band (Glb1) occurs some 10 to 35 m higher, the strata between the two marine bands being dominantly argillaceous. A thin sandstone is present in the interval at Phoenix Mills Borehole (Figure 5a).

The sequence between the C. cumbriense Marine Band and the base of the Rough Rock Flags varies greatly in thickness (Figure 5a) and (Figure 5b). In the Sowerby Bridge area, the succession is estimated to be about 35 m thick and includes a thin unnamed sandstone, which is up to 6 m thick in boreholes. The sandstone is partly exposed in Crawstone Clough, where 3.5 m of micaceous, laminated, fine grained sandstone are present about 28 m above the C. cumbriense Marine Band. The sandstone forms a minor feature on the slopes below the Rough Rock plateau between Greetland and Norland and at West Vale. Wray et al. (1930) named the sandstone Moorside Flags but erroneously described it as occurring below the C. cumbriense Marine Band. They further suggested that the Moorside Flags correlate with the Haslingden Flags of Lancashire. However, the sandstone exposed in Crawstone Clough is strongly micaceous, so differs lithologically from the Haslingden Flags (Collinson and Banks, 1975). A probable correlative of the Haslingden Flags occurs in the Denshaw area, at Bleakedgate Moor [SD 972 131]. The sandstone, estimated to be 5 m thick, is not exposed. Typically, in the Rochdale district (Sheet 76), the sandstone is fine grained and pale greenish grey (Wright et al., 1927; Collinson and Banks, 1975).

The Rough Rock Flags usually crop out on steep slopes below the capping of Rough Rock but also form large areas of dip slope at Ovenden Moor, Hunter Hill, Mount Tabor and Crosland Moor, although exposures are usually limited to quarry sections (Plate 2a). The total thickness of Rough Rock Flags is very variable, from 0 to 15 m in the Stainland area, but up to 30 m around Sowerby Bridge. Regional controls on the sedimentation of the Rough Rock Flags are discussed by Bristow (1988), who refers to them as having been deposited in lobate shallow water deltas, with a palaeocurrent flow toward the south and west. The lateral thickness variations noted above may have resulted in part from erosion by fluvial currents prior to Rough Rock deposition (Bristow, 1988).

The Rough Rock Flags comprise fine to medium grained micaceous sandstone, cross-bedded, planar laminated or ripple laminated. The flags lack the quartz pebbles common in the overlying Rough Rock. The base of the Rough Rock Flags is generally gradational from the mudstone that overlies the C. cumbriense Marine Band, with an upward increase in the thickness and frequency of siltstone and sandstone beds. The base is taken where sandstone beds form more than half the thickness of the section. The key section in the district is the Elland road cut, described in detail by Bristow and Myers (1989) and Jones et al. (2000). The lowest 7 m of strata are interbedded fine-grained micaceous sandstones and siltstones, in beds 0.3 to 2 m thick with planar lamination and wave modified current ripples. These are overlain by about 7 m of sandstone, which is medium grained, trough cross-bedded with some planar bedding, and bedsets that dip gently downcurrent, typically 0.2 m thick. Internal erosion surfaces are minor. The boundary with the overlying Rough Rock has been drawn at an erosion surface (but see below).

During this survey, because of poor exposure, it was not possible to separate the Rough Rock Flags from Rough Rock over much of the Stainland area. The distinction in boreholes is also generally unclear (Figure 5a) and (Figure 5b), though in some of the boreholes around Halifax, such as that at Stone Trough Brewery, a shale parting with a thin coal is taken to define the boundary.

The Rough Rock is the youngest sandstone of the Millstone Grit. The top of it was formerly identified as the top of the Millstone Grit (Wray et al., 1930). However, the top of the Millstone Grit Group is now regionally defined at the top of the Namurian Series, which is drawn at the base of the Subcrenatum Marine Band, a few metres above the top of the Rough Rock.

The Rough Rock comprises massive or cross-bedded feldspathic sandstone that is coarse to very coarse grained, but medium grained in places, with granules and small rounded pebbles predominantly of quartz. It forms prominent escarpments with extensive dip slopes, as at Ovenden Moor, Illingworth Moor, Halifax and Elland town centres, Norland Moor, Wholestone Moor and Crosland Moor. The total thickness of Rough Rock is estimated to be about 10 to 20 m in the Stainland area, up to 27 m in the Sowerby Bridge area and 33 m in Illingworth, Halifax.

Regional controls on the sedimentation of the Rough Rock are discussed by Bristow (1988), who refers to this sandstone as a widespread, multi-storey and multi-lateral fluvial sheet sandstone with a sharp, slightly channelled erosion surface at the base. It is interpreted as the deposit of a braided river, which in the Huddersfield area had a palaeocurrent flow direction towards the south.

Exposures in the Rough Rock are for the most part limited to quarry sections. The key section in the Huddersfield district is the Elland road cut (Plate 2b), described in detail by Bristow and Myers (1989) and Jones et al. (2000). Up to 18 m of Rough Rock are exposed, resting on Rough Rock Flags. The lower part comprises 5 to 12 m of mainly coarse-grained cross-bedded sandstone with common internal erosion surfaces. Note that Bristow and Myers (1989) refer to this unit as Rough Rock Flags, using the nature of large-scale bedforms as the distinguishing feature. However, the grain size and small-scale sedimentary structures suggest that it should be referred to the Rough Rock. Sets of trough cross-bedding are up to 1.5 m thick and traced for 150 m downcurrent. Palaeocurrent flow was towards the south-east. Bristow and Myers (1989) interpret these beds as fluvial channel deposits, probably of minor distributary channels.

The higher part of the Rough Rock here comprises up to 11 m of coarse to very coarse-grained sandstone with some granules and pebbles, and has a sheet-like geometry. There is a sharp erosional base, overlain by an intraformational conglomerate, which bears mudstone rip-up clasts. The sandstone shows large-scale trough cross-bedding that indicates a palaeocurrent direction towards the south-southeast. Bristow and Myers (1989) interpret this facies as a braided river deposit.

The Pot Clay and Pot Clay Coal overlie the Rough Rock. The Pot Clay, the seatearth to the coal, is a fireclay that was formerly extracted for bricks and pottery (Wray et al., 1930). The coal was of little value. It was recorded,

0.1 m thick, in the previous survey at the entrance to Queensbury Railway Tunnel at Holmfield and in a cut at the western end of Milk Churn Lane. In site investigation boreholes around Halifax the coal varies from 0.05 to 0.2 m thick, and rests on seatearth 1.5 m thick, which in turn rests on the Rough Rock.

The highest Namurian strata are thin fissile mudstones with a nonmarine bivalve fauna between the Pot Clay Coal and the base of the Subcrenatum Marine Band. The mudstone and its fauna were noted by Wray and Melmore (1931) in the Phoenix Mills Borehole, see also (Figure 5a), and the fauna was described in its regional context by Eagar (1953).

Key localities

Todmorden Grit

Crimsworth Dean Beck [SD 9899 3081], Hardcastle Crags [SD 9716 3064] and [SD 9717 3022], Colden Water [SD 9756 2821], Horsehold Scout [SD 9805 2670] [SD 9815 2683] and [SD 9825 2693], Cat Scout [SD 9881 2708](Table )

Lower Kinderscout Grit(Table )

Blackstone Edge [SD 9724 1666], Hell Hole Quarry, Heptonstall [SD 9856 2772], Horsehold Quarry [SD 9837 2690], Stoodley Pike [SD 9723 2420] to [SD 9725 2411], Derby Delph Quarry [SE 0165 1609] to [SE 0186 1613]' Holder Stones [SD 970 216]' Dove Lowe Stones [SD 974 205]

Reticuloceras coreticulatum Marine Band(Table )

Horrodiddle [SD 9771 3151]

Upper Kinderscout Grit(Table )

Green Withens Reservoir [SD 9958 1642], Slate Pit Hill [SD 9856 1791], Windy Hill Road cut, M62 [SD 977 147] to [SD 981 147], Higham Quarry [SD 9802 2448], Firth House Wood [SE 0619 1828]

Bilinguites gracilis Marine Band(Table )

Dry Clough [SD 9904 1774], Castle Shore Clough, M62 [SD 9759 1459], Dry Clough, Linsgreave [SD 9873 1351], Horse Hey Clough [SE 0012 1914]

Readycon Dean Flags(Table )

Deanhead Clough [SE 029 149], Slaithwaite Reservoir [SE 0748 1406], Mount Skip Quarry [SE 0131 2736], Nell Nook [SE 0285 2788], Upper Saltonstall [SE 0371 2844], Dodge Royd Wood [SE 046 222] to [SE 048 224], Highlee Wood [SE 0454 2110] to [SE 0456 2099], Cob Clough [SE 0428 1952], Tom Clough [SE 006 131](Table )

East Carlton Grit (‘Scotland Flags’)(Table )

Scotland Quarries [SE 032 267] Foster Clough Delphs [SE 0210 2731], Kitchen Clough [SE 0810 1345], Great Mount Quarries [SE 010 276], Slaithwaite Reservoir [SE 0748 1406], Sowerby Bridge Cemetery [SE 051 237]

Bilinguites bilinguis Marine Band(Table )

Foster Clough Delphs [SE 0210 2731], Green Withens Clough [SD 9972 1641]

Midgley Grit(Table )

Clock Face Quarry [SE 0466 1750 to SE 0481 1754], Moselden Heights Quarry [SE 044 162], Castle Quarries [SE 0281 1910], Butts Clough [SE 0416 1794], Only House Quarry [SE 0741 1847] to [SE 0735 1840], White Rock Quarry [SE 0668 177] to [SE 0675 1781], Crimble [SE 0870 1470], Nab End Quarries [SE 0167 2439] to [SE 0184 2446], Rough Hey Scar [SE 047 216]

Bilinguites metabilinguis Marine Band(Table )

Highlee Clough [SE 0478 2129], Cupwith Hill [SE 0340 1431], Blake Clough [SE 052 136], Butts Clough [SE 043 178]

Guiseley Grit(Table )

Pierhorne Clough [SD 972 135], Beacon Hill Quarry [SE 0416 1847], Wham Quarry [SE 0757 1833] to [SE 0756 1823], Raw Bank Quarry [SE 0676 1984], Marsh Quarry [SE 0598 2434]

Bilinguites superbilinguis Marine Band(Table )

Caty Brook, Wainstalls [SE 045 289], Black Brook, Barkisland [SE 070 201]

Huddersfield White Rock(Table )

Beestones Quarry, [SE 0689 1952], Longwood Brook [SE 0925 1767], Waterloo Quarry [SE 0712 1711], Euden Edge, Clough Head [SE 081 158] to [SE 088 151], Golcar School Quarry [SE 099 157], Wild Brow Quarry, High House Edge [SE 0945 1320], Caty Brook, Wainstalls [SE 045 289], Scar Wood, Milnsbridge [SE 105 158], Clough Bank Beck, Hebble Brook Valley [SE 0647 2781], Riding Bridge, Hebble Brook Valley [SE 0653 2720]

Cancelloceras cumbriense Marine Band(Table )

Crawstone Clough [SE 0758 2109]

Rough Rock Flags(Table )

Delph Hill [SE 0795 2392], Greetland Nook Quarry [SE 0657 2118], North Dean Quarry [SE 0776 2229], Eaves Top Wood [SE 0794 2007], Dean Top Delph [SE 0954 2158] to [SE 0962 2158], Elland Road Cut [SE 103 215]

Rough Rock(Table )

Rocking Stone Quarry [SE 0759 1610], Delph Hill [SE 0795 2392], Greetland Nook Quarry [SE 0657 2118], Eaves Top Wood [SE 0794 2007], Dean Top Delph [SE 0954 2158] to [SE 0962 2158], Woodside Quarry [SE 099 209], Wellfield Quarry [SE 118 144], Crosland Heath Quarries [SE 108 144], Elland Road Cut [SE 103 215]

Pot Clay Coal(Table )

Queensbury Railway Tunnel, Holmfield [SE 0880 2920], Churn Milk Lane [SE 0830 2775]

Chapter 4 Westphalian

Coal Measures, of Westphalian age, crop out over the eastern half of the district. Deposition of the Coal Measures took place in riverine and lake environments, with periodic of flooding by the sea. Coal seams developed from peat beds that formed in these poorly drained low-lying environments. The nature of sedimentation in the Coal Measures is described by Guion and Fielding (1988) and Guion et al. (1995). Chisholm (1990) provides a more specific description of depositional environments for the sequence between the 80 Yard (Upper Band) and Better Bed Coals in the central and south Pennine area.

Coal Measures Group

The Coal Measures Group is divided into Lower, Middle and Upper formations, of which the Lower Coal Measures and part of the Middle Coal Measures are present in the district (Table 3). These units are respectively of Langsettian (Westphalian A) and Duckmantian (Westphalian B) age. The Coal Measures rest conformably upon the Millstone Grit, the base being taken at the base of the Subcrenatum Marine Band. Biostratigraphic classification (Table 3) is based on stages defined by marine marker bands, and on nonmarine bivalve zones. These and other faunas are described by Calver (1968a, 1968b).

Wray et al. (1930) provided a valuable account of the Coal Measures in the Huddersfield district, with information on rock exposures that are no longer visible, and details of mineral workings (coal, fireclay, brickclay, sandstone) that were being actively pursued at the time of their survey. However, the stratigraphy used by these authors has been amended during the recent geological resurvey. In particular, the term Elland Flags is now used in a more restricted sense, and a miscorrelation of the Grenoside Sandstone with the Kirkburton Sandstone has been corrected (see below).

The Coal Measures present in the district consist of about 760 m of interbedded mudstone, siltstone and sandstone, with subordinate coal, seatearth and ironstone, deposited about 310 million years ago. Recent work has shown that the clastic sediments were transported into the Pennine area by large river systems that drained widely separated source regions, which had different palynological, geochemical and heavy mineral signatures (Chisholm et al., 1996; Leng et al., 1999; Hallsworth and Chisholm, 2000; Hallsworth et al., 2000). These differences have allowed changes of provenance to be determined, and it can be demonstrated that, for of the Elland Flags and sandstones below them, the sediments were derived mainly from the northern terrain that was the source of the sediments of the Millstone Grit. In contrast, the sediments that formed the overlying beds came mainly from a distinct source region that lay to the west. Among the ‘western’ beds in the Huddersfield district, four ‘northern’ sandstones have been identified: in ascending order these are Grenoside Sandstone, Kirkburton Sandstone unit 2, Linfit Sandstones; and a localised part of the Emley Rock.

The mudstones of the Coal Measures vary from grey to black, and from massive to fissile. Nonmarine bivalves are commonly present, and rarer marine faunas also occur (see below). Ironstone is present in many mudstones, generally as flat nodules a few centimetres thick. The mudstones are commonly overlain gradationally by siltstones. Siltstones are typically medium grey in colour and contain plant debris. They grade both vertically and laterally into sandstones and mudstones, and are commonly interbedded with both. Sedimentary structures include parallel lamination and ripple cross-lamination. Trace fossils may be present, particularly where siltstones and sandstones are interbedded. Upper Carboniferous trace fossils of the central Pennine area have been described by Eagar et al., (1985).

Sandstones commonly form positive, mappable, topographic features and are thus distinguished on the map from the mudstones and siltstones, which are shown as Lower or Middle Coal Measures (undivided). The sandstones vary from very fine to medium grained, and comprise subangular to subrounded quartz and feldspar with a variable mica content. They are grey when fresh, but weather to yellowish brown. Sedimentary structures include planar lamination, ripple lamination, cross-bedding and massive beds. Coalified plant fragments are common on bedding surfaces. Sandstones of ‘northern’ origin tend to be more micaceous, coarser grained, and less clayey than those of ‘western’ origin. A greenish grey colouration is evident in some sandstones, siltstones and mudstones of ‘western’ type.

Seatearth is the name given to soil profiles (palaeosols), which developed during periods of subaerial exposure and colonisation by plants. They are found in all lithologies, being referred to as ganister when developed in sandstone, and fireclay when formed in mudstone. They are characterised by the presence of rootlets, commonly Stigmaria. The soil-forming processes have generally destroyed primary sedimentary structures, and ironstone nodules in seatearths are commonly irregular in shape.

Coal seams are common and some are developed on a regional scale (Table 4). They vary laterally in thickness and composition, particularly by variation in the number and thickness of dirt partings present in the seam; seam splits are common. The coals are generally underlain by seatearths.

Marine bands are thin beds of black or dark grey mudstone with a marine fauna, and commonly overlie coal or seatearth. They are generally a few centimetres thick, but some may reach 2 or 3 m. They commonly grade upwards into mudstone and siltstone which may be unfossiliferous, or may contain nonmarine faunas. Marine bands represent flooding events that were controlled by world-wide changes of sea level, so can be recognised as marker horizons across large areas. Ten marine bands are recognised in the district. Most contain restricted faunas of foraminifera, conodonts, Lingula, or marine bivalves, but three (the Subcrenatum, Listeri and Vanderbeckei Marine Bands) contain rich faunas, with ammonoids diagnostic of their particular horizon. The nearmarine Low Estheria Band is also known in the district.

Lower Coal Measures

The succession is described in five parts. The first and lowest part (Figure 7) extends from the base of the Coal Measures to the horizon of the 80 Yard Coal and has many marine bands. The second (Figure 8) extends from the 80 Yard Coal to the Better Bed Coal and is dominated by sandstones. The third (Figure 9), fourth and fifth (Figure 10) extend from the Better Bed Coal to the base of the Vanderbeckei Marine Band and contain more abundant and thicker coal seams than the underlying parts.

Base of Lower Coal Measures to 80 Yard Coal

These measures (formerly known as the ‘Ganister Coal Series’) consist of a succession of upward-coarsening cyclic units that can be traced throughout the central and south Pennine region (Figure 7). The boundary between any two cycles is drawn at the top of a coal (or seatearth if the coal is absent). In Yorkshire the cycles have been named informally after prominent beds within them (Waters et al., 1996; Chisholm et al., 1996). Detailed sections in former brickpits near Huddersfield (Figure 11) and (Figure 12) have been described by Wilson and Chisholm (2002). The thickness of the interval varies from about 85 to 160 m in the district, with a maximum near Huddersfield, at the centre of the ‘Huddersfield sub-basin’ of the Pennine Basin of deposition. All the sandstones are of northern provenance.

The lowest unit (Soft Bed cycle) is about 35 m thick (21 to 45 m in boreholes), the base being drawn at the base of the Subcrenatum Marine Band, formerly known as the Pot Clay Marine Band. This is overlain by largely unfossiliferous mudstone although a nonmarine bivalve band has been recorded near to the top. The mudstone passes up into micaceous sandstone and siltstone of the Soft Bed Flags, which are laterally persistent but of very variable thickness. Typically, the flags vary from 0 to 8 m in thickness, but thicknesses of up to 13.5 m are recorded in the Halifax area where locally two leaves are present, or as much as 30 m around Huddersfield where the flags form extensive dip slopes in the western part of the town. The flags are rooty at the top and are overlain by thin seatearths below the Soft Bed Coal, the lowest worked seam in the district (Table 4). This coal is about 0.3 to 0.6 m thick, but only 0.1 to 0.3 m in the north. It is present throughout the district and was extracted from shallow workings during the 19th century and from deeper workings around Shibden Dale, Northowram and Southowram. It is well known from deep boreholes around Ravensthorpe in the south and Pudsey and Farnley in the north (Wray et al., 1930). The seatearth was worked for fireclay in a few places notably around Elland.

The overlying Middle Band cycle, which is about 15 m thick (4.5 to 17 m in boreholes), was described in its regional context by Eagar (1947, 1952, 1956) as the Soft BedBassy Mine Succession. The mudstone that makes up most of the cycle contains three nonmarine bivalve faunas and two interleaved Lingula bands, the Holbrook and Springwood Marine Bands. Above the mudstone is the Middle Band Rock, a laterally impersistent sandstone rarely over 5 m thick. It forms a prominent feature in the eastward-inclined dip slope on which Huddersfield town centre is built. It has been mapped at outcrop in the north of the district around Soil Hill and a number of site investigations around Halifax record about a metre of ganisteroid sandstone. At the top of the cycle the Middle Band Coal is extensive, but too thin to be worked except in the vicinity of Soil Hill, Queensbury.

Above the Middle Band Coal lies the Hard Bed cycle, a sequence about 10 m thick (7.5 to 13 m in boreholes) dominated by mudstone and capped by a thin, very local, sandstone and a persistent seatearth below the Hard Bed Coal. At the base is the Honley Marine Band, a Posidonia-Lingula fauna in dark mudstone in the roof of the Middle Band Coal. Nonmarine bivalves have been recorded at higher levels. The Hard Bed Coal, also known as the Halifax Hard Bed, is commonly about 0.6 m thick and was worked, together with its underlying seatearth, in all areas close to the outcrop. Its sulphurous nature made it unattractive for deeper exploitation although deep mining did take place around Rowley Hill (Wray et al., 1930) where the fireclay was also extracted. Around Halifax and Elland, pyrite nodules from within the coal were previously processed for sulphuric acid in copperas works.

The overlying Stanningley cycle is about 30 m thick (24 to 35 m in boreholes). At the base, resting directly on the Hard Bed Coal, is the Listeri Marine Band, which comprises up to about 1 m of black fissile mudstone with abundant Gastrioceras listeri, Dunbarella and Posidonia, overlain by about 2 m of mudstone with sparse marine bivalves and Lingula. The mudstone above the marine band is generally unfossiliferous, but the two Parkhouse Marine Bands, with marine bivalves and Lingula, have been detected in some sections about 5 and 8 m above the Hard Bed Coal. Nonmarine bivalves have been recorded at higher levels. The mudstone succession is commonly overlain by the Stanningley Rock (formerly called Hard Bed Band Rock), a laterally impersistent sandstone varying in thickness up to about 17 m. The sandstone is typically pale grey, fine to medium grained, micaceous, with roots at the top, and is overlain by a variable sequence of seatearths up to about 9 m thick, with one or two impersistent coals and minor sandstones. A coal seam within the seatearths is called the Hard Bed Band Coal; the seam that caps them is the 36 Yard Coal. The coals are too close to distinguish on the map, so are shown together, as 36 Yard Coal. The seatearths were widely worked along the outcrop, and the coals were worked with them in places.

Above the 36 Yard Coal is the 48 Yard cycle, which comprises a mudstone-dominated sequence usually about 10 m thick (9 to 23 m in boreholes), with a thin impersistent sandstone, the 48 Yard Rock, present in places at the top. An impersistent fauna of foraminifera or marine bivalves just above the 36 Yard Coal is the Meadow Farm Marine Band. A nonmarine bivalve band is recorded in the mudstone above. Except in the north around Shibden Head, the 48 Yard Rock is rarely seen; at Storth brickpit it was only 26 cm thick, very fine grained, and rooty. The cycle is capped by seatearth, overlain locally by the thin 48 Yard Coal.

The 80 Yard cycle is generally about 30 m thick (7.5 to 35 m in boreholes), mainly mudstone, with the thin but distinctive Amaliae Marine Band present in places about 3 m above the base and the Norton Mussel Band (Eagar, 1974a, 1974b) at a higher level. The marine band is about 2 to 5 cm thick, with Dunbarella ghosts, as in its better known development (as Tonge’s Marine Band) in Lancashire (Earp and Magraw, 1955). The mudstone grades up through siltstone to the 80 Yard Rock (Plate 3), a fairly persistent sandstone up to about 10 m thick that is overlain by seatearth and locally by the thin 80 Yard Coal.

80 Yard Coal to Better Bed Coal

The succession between the 80 Yard Coal and the Better Bed Coal is notable for its sandy nature and paucity of coal seams, throughout the central Pennine area (Chisholm, 1990; Figure 8). Within the district the interval varies in thickness from about 105 to 140 m. All sandstones in this sequence were called Elland Flags by Wray et al. (1930), but it is now recognised that three major divisions, or cycles, can be distinguished on the basis of the lithology and provenance of the sediments. The nomenclature of the sandstones has therefore been revised to reflect these differences (Chisholm et al., 1996). The name Elland Flags is now restricted to the sandstones in the lowest cycle, which are strongly micaceous and have been quarried extensively at Elland Edge and elsewhere. The sandstones in the two higher divisions are now known to correlate with the Greenmoor Rock and Grenoside Sandstone of the Sheffield area, so these names are extended into the Huddersfield district. It follows that the use of Greenmoor Rock as a synonym for Elland Flags (Bromehead et al., 1933) is no longer valid.

As with the underlying beds, each of the three cycles is named after a prominent sandstone within it. The Elland cycle is 60 to 80 m thick in the north of the district, decreasing to about 45 m in the south. Through most of the district it comprises up to 20 m of mudstone succeeded by about 50 to 60 m of fine-grained strongly micaceous sandstone, siltstone and mudstone interbedded in generally upward-coarsening units with burrowed or rooty tops. Coal is rare. All the clastic sediments are of northern provenance. At the base of the basal mudstone, resting on the 80 Yard Coal, is the horizon of the impersistent Langley Marine Band, which has not so far been found in this district. The overlying sandstones are the Elland Flags, a valuable source of tilestones and flagstones once widely worked both at surface and underground (Godwin, 1984). They still provide crushed stone and flagstone. South from Elland Edge (Plate 3), the sandstones become finer grained over a distance of about 7 km (Figure 13) continuing as a much thinner unit, the Benomley Siltstones, which are present at the south margin of the district (Chisholm, 2000a). Farther south again, the siltstones pass laterally into mudstone (Figure 8).

The Greenmoor cycle is of western provenance, and is distinguished by weakly micaceous lithologies with a greenish grey coloration. It is generally about 25 m thick in the north, but increases southwards, reaching about 60 m at the southern margin of the district. This thickening may be a response to the commensurate thinning of the Elland cycle. At the base of the cycle is a persistent bed of mudstone, about 10 to 30 m thick, the lower part of which is grey with greenish grey measures above, and this is overlain by a variable sequence of interbedded sandstone, siltstone and mudstone. The harder beds (very fine-grained sandstone and quartzose siltstone) form positive topographic features and are referred to as Greenmoor Rock. North of the Colne valley these beds are only 5 to 15 m thick, with one or two leaves of Greenmoor Rock, but to the south the thickness increases to 50 m, with up to five leaves of Greenmoor Rock. The horizon of the Burton Joyce Marine Band is thought to lie at the base of the cycle (Chisholm, 1990), although no marine fauna has yet been found at this level. One or two seatearths, with or without thin shaly coals, are present in the upper parts of the cycle; a local coal at the top of the cycle is equivalent to the Dib Hole Coal of Lancashire (Magraw, 1957). Sections in the north at Horton Bank reservoir, were described by Waters et al., (1996a) who recorded thin representatives of the Greenmoor Rock and Grenoside Sandstone separated by about 6 m of mudstone and siltstone that include a thin impersistent coal seam believed to be the correlative of the Dib Hole Coal.

The Grenoside cycle is generally about 25 m in thickness, increasing southwards to about 32 m at the southern edge of the district. It is of northern provenance (though the sediment entered the area from the east), and is distinguished from the Greenmoor cycle by its generally micaceous lithologies and lack of greenish grey coloration. At the base is a persistent bed of dark grey micaceous mudstone about 5 m thick, which locally contains a nonmarine bivalve fauna corresponding to the Daubhill fauna of Lancashire (Chisholm, 1990). Above the basal mudstone are some 20 m of interbedded micaceous sandstone, siltstone and mudstone capped by the seatearths of the Better Bed Coal. The sandstones are leaves of the Grenoside Sandstone. In the north these are fine to very fine grained, in one, two, or three leaves, but in the extreme south there is only one leaf, of fine to medium grain size, and up to 20 m thick. Sections at Lepton show that this leaf originates near the top of the cycle and cuts down southwards to rest directly on the basal mudstone in a feature described by Chisholm (1990) as the Thurlstone Channel.

The Better Bed Coal, also called Low Moor Better Bed, has a thick seatearth and lies up to 8 m above the top of the Grenoside Sandstone. It ranges in thickness up to 0.9 m and was widely worked underground and from opencast sites at Brighouse, Tong and Kirkheaton. Parts of the seatearth were also worked locally for refractory clay.

Better Bed Coal to Blocking Coal

These strata are about 180 m thick and, like the beds below, show an alternation of mudstone, siltstone and sandstone (Figure 9). However, they differ in that marine bands are absent, and individual upward-coarsening units are of limited extent. Also, coals are more common than in the beds below, and seam splits are common at some levels. Most of the clastic sediment is of western provenance, but northern sourced lithologies have been detected at two levels (see below).

In the south of the district the lowest beds were miscorrelated by the earlier surveys (Green et al., 1878; Wray et al., 1930; Bromehead et al., 1933) because the Kirkburton Fault at Kirkburton was wrongly thought to have a downthrow to the south-west, when in fact its downthrow is to the north-east (Chisholm, 2000b). As a result, about 60 m of the succession were omitted and the Grenoside Sandstone (which underlies the Better Bed Coal, see above) was thought to lie above the Black Bed Coal, and so to correlate with the bed now called Kirkburton Sandstone. The mis-correlation was not evident because both the Better Bed and Black Bed deteriorate in the south part of the district so that control from coal workings was lacking.

The interval between the Better Bed Coal and the Black Bed Coal is 35 to 40 m thick and generally consists of two upward-coarsening units. At the base of the lower unit, a black fissile mudstone with fish fragments is commonly present in the immediate roof of the Better Bed Coal. Sandstone in the lower unit is unnamed whereas that in the upper unit is known as the Thick Stone. Both are very fine grained and, though the Thick Stone may reach 20 m in thickness in the north, neither is persistent throughout the district. The thin and shaly Better Bed Band Coal overlies the lower sandstone. The Black Bed Coal, also known as the Low Moor Black Bed, is 0.2 to 1.8 m thick (usually 0.5 to 0.9 m) and was widely worked underground.

Between the Black Bed Coal and the Crow Coal lies a variable succession generally 10 to 20 m thick, with a variable number of sandstones collectively referred to as Kirkburton Sandstone (Chisholm, 2000b). In the north, the Black Bed is generally succeeded directly by dark grey mudstone that has yielded numerous fish remains, and by mudstone with ironstone bands, the Black Bed Ironstone (or Low Moor Ironstone) that was economically important and worked in the past around Low Moor and elsewhere. In the south, a variable thickness of sandstone, siltstone and mudstone (unit 1 of the Kirkburton Sandstone) rests on the coal. Palaeosols in these beds suggest that they lie in southward-thickening splits beneath upper leaves of the Black Bed Coal. Above the Black Bed Ironstone is a distinctive fine to medium-grained micaceous sandstone of northern provenance (unit 2 of the Kirkburton Sandstone), which has been widely recognised across the district by its lithology and heavy mineral signature. It is likely that this sandstone has, in places such as Norwood Green and Cockersdale, cut down to form the roof of the Black Bed Coal and has elsewhere formed local washouts (Wray et al., 1930). In the south, unit 3 of the Kirkburton Sandstone consists of an upward-coarsening sequence with a very fine-grained sandstone at the top, capped by a thin shaly coal which is assumed to be the Crow Coal of the northern part of the district. This last (also known as the 14 Yard Coal) contains many splits but locally reaches a thickness of up to 1.2 m and was worked in the north around Shelf.

Between the Crow Coal and the various components of the Beeston group of coals lies a sequence about 50 to 60 m thick. Two thin but widespread coals occur in the lowest 20 m or so, and in the north part of the district are named 22 Yard Coal and 32 Yard Coal. Above these coals the strata are commonly dominated by sandstones that include the Oakenshaw Rock, Shertcliffe Seatstone and Clifton Rock. None of these is well constrained stratigraphically (Wray et al., 1930), and the name Clifton Rock is now used as a general term for sandstones at this level. Among them is a distinctive pale coloured quartzitic and locally coarse-grained lithology, with a heavy mineral suite indicating western provenance (Chisholm et al., 1996). The quartzitic lithology is unique among beds of western origin (Hallsworth and Chisholm, 2000). The full lateral and vertical extent of the facies has not been determined, though it appears to account for most of the sandstones in the Crow to Beeston interval in the north of the district (Figure 9), but for only a proportion of them in the south.

The Beeston Group of Coals is loosely defined as a plexus of seams spread through some 10 to 40 m of strata, and derived by a complex series of splits and coalitions from the thick Beeston Coal of the Leeds area. In the north and centre of the district, it includes, besides unnamed seams, various leaves of the Shertcliffe Coal, while in the south it includes the Top and Low Whinmoor Coals, the Black Band (or ‘Beeston’) Coal and the Linfit Lousey Coal. In the north-east the Churwell Thin and Churwell Thick Coals are apparently split from the Top Beeston Coal (Lake, 1999), the Churwell Thick further splitting into the Shertcliffe Coal and Little Coal (Green et al., 1878). The various local names used in the past were not applied consistently across the district even during the period when the coals were being worked, as demonstrated by the sample of shaft sections shown in (Figure 9). The name Shertcliffe Coal was usually given to a workable seam up to 0.8 m thick, but not to the same seam everywhere. The Shertcliffe Coal was previously named the Lower Lousey Coal, the succeeding seam being termed the Upper Lousey (Green et al., 1878). Wray et al., (1930), adopting the name Shertcliffe Coal, described two seams above it that he named Low Lousey and Top Lousey. Clearly Wray’s Low Lousey Coal is the same as Green’s Upper Lousey Coal. To avoid confusion the thin seam that is the highest coal of the Beeston group (the Upper Lousey of Green et al., 1878 and the Low Lousey of Wray et al. 1930) is now termed the Linfit Lousey Coal. It is recognised and correlated on the basis of the distinctive Linfit Sandstone that overlies it. The name Top Lousey of Wray et al. (1930) is retained for the seam that lies above the Beeston Group of coals in the north of the district (the Lousey Coal of Green et al., 1878). The Linfit Lousey may be equivalent to the Churwell Thin coal in the north (Green et al., 1878). The Beeston Group of coals were widely worked underground and from opencast sites around Lepton. The Top Lousey Coal was extracted from opencast workings around Scholes, Hartshead Moor. Between the Beeston group of coals and the Blocking Coal are some 35 to 55 m of variable strata. The Linfit Lousey Coal is overlain by the Linfit Sandstone, a micaceous bed with a heavy mineral suite that suggests a northern provenance (Hallsworth and Chisholm, 2000). In the north, two thin coals have been named and were worked around Wyke. The lower seam is the Trub Coal; the upper is the Top Lousey Coal, which lies immediately under the Low Estheria Band. This consists of 10 cm of dark grey fissile mudstone with ‘Estheria’ and is an important regional marker horizon recorded in the Moorlands Mill Borehole and seen at outcrop in Jagger Park Wood, Shelf. In the south, the Low Estheria Band is present but coal seams are thin and have not been named. Thin and impersistent sandstone beds occur. The sequence that includes the Low Estheria Band is capped by the Blocking (Bed) Coal, sometimes referred to as the Silkstone Coal, which was widely worked and is reliably correlated across the entire coalfield. It ranges in thickness from 0.3 m around Denby Grange, to 0.7 m around Liversedge, Gomersal and Mirfield. It is thin in the north-east and also diminishes in thickness and quality south of Emley. The Blocking Coal was worked opencast at Hartshead Moor and Hunsworth, south of Bradford, and to a lesser extent, around Houses Hill Lepton. It is likely that the Top Lousey Coal is equivalent to the lower leaf of the Silkstone Coal of the Barnsley district, since the Low Estheria Band lies between the Low Silkstone and the Top Silkstone (Smith et al., 1973).

Blocking Coal to Middleton Little Coal

Unlike the preceding strata, the measures between the Blocking Coal and the Middleton Little Coal are consistent in their development across the district but vary in total from about 60 to 75 m (Figure 10). The roof measures of the Blocking Coal contain nonmarine bivalves and fish remains and a thin ironstone (a correlative of the Claywood Ironstone of Sheffield and Barnsley); a few metres higher in the sequence is a thin coal, the Blocking Rider Coal, which has similarly fossiliferous roof measures. Above the Blocking coals the Falhouse Rock is developed in one or two leaves of fine-grained sandstone, commonly interbedded with siltstone and very variable in thickness. It is 20 m thick at Falhouse (Green et al., 1878) but thins westwards to no more than a few metres around Lepton and Linfit and it is absent from colliery sections to the east. Farther north, it is about 15 m thick around Norristhorpe, Heckmondwike and East Bierley but it is absent from some intervening areas and in the north-east, adjacent to the Morley-Campsall Fault. Falhouse Rock sediments were deposited broadly central to the Gainsborough Trough, but the thicker sequences lie along a zone that follows a more southerly trend, oblique to the axis of the trough (Figure 16). The cycle that includes the Falhouse Rock is capped by the Middleton Eleven Yards Coal, which is usually about 0.3 m thick but may exceed 1 m; it is commonly split and lies about 16 to 22 m above the Blocking Coal or generally rather less in the south-east. It was worked over much of the district but in some areas was previously misidentified as the Wheatley Lime Coal.

The measures overlying the Middleton Eleven Yards Coal are generally about 6 to 12 m thick and, around Heckmondwike, Batley and Cleckheaton in the Spen valley, include a 3 to 4 m bed of fine-grained cross-bedded sandstone. These beds are overlain by the Wheatley Lime (Three Quarters) Coal which is generally well developed and worked over the entire area as a single coal up to 1 m thick. It is thin and poorly developed or absent in the north around Batley and Gomersal. The Wheatley Lime was extracted by opencast workings at Hartshead and Mirfield Moor and at Houses Hill, north-west of Grange Moor.

The Wheatley Lime Coal is overlain closely by a 2 to 10 m thick sandstone that forms marked features in Cleckheaton, Birkenshaw, East Bierley, Batley and Thornhill. The sandstone is thickest around Liversedge and Grange Moor, but is thin or absent around Gildersome and Upper Batley. Presumed downcutting of this sandstone has produced a washout in the seam about 500 m wide extending north to south between Thornhill and Overton (Wray et al., 1930). The measures above the Wheatley Lime vary in total thickness from about 12 m in the east to about 20 m in the west and commonly include a thin unnamed coal. They underlie the Middleton Main (New Hards) Coal, a widespread and consistently developed coal of former economic importance. This seam generally forms a single 1 to 1.8 m-thick bed but splits are common in the north around Gildersome. The seam is thinner to west of Dewsbury and is washed out to the east of there by a 10 m thick sandstone. South of the Calder, the seam is more uniform and generally about 1 m thick. Around Emley and Thornhill the base of the seam undulates forming swilleys in the coal.

The roof measures of Middleton Main Coal are commonly mudstone rich in nonmarine bivalves, fish remains and ostracods, and pass up into mudstone with thin sandstones and unnamed coals. The total sequence varies from about 16 m thick in the south to about 30 m thick in the north and is capped by the Middleton Little (Green Lane) Coal. This is a widespread seam of rather inferior quality that varies from about 0.2 m or less in the north and west, around Drighlington and Gomersal, to about 0.9 m in the east, around Thornhill, and 0.7 m in the south around Emley. It was worked in the north-east, around Gildersome, and in the south, around Emley. Contrary to statements of Wray et al., (1930) and Green et al., (1878), it is now believed to correlate with the Parkgate Coal of districts to the east and south (Lake, 1999).

Middleton Little Coal to Joan Coal

The Middleton Little Coal (Figure 10) is overlain by mudstone that contains nonmarine bivalves and fish remains and passes up into a very variable sequence that includes two significant sandstone units, the Lepton Edge Rock and the Birstall Rock, and a group of three coals, the Brown Metal Coals. Downcutting by elements of the Birstall Rock leads to washouts of the two upper coals of the group.

The Lepton Edge Rock (Figure 13) lies a few metres above the Middleton Little Coal and is generally a fine to very fine-grained sandstone, thinly bedded to flaggy and variable in thickness from 2 to 11 m. It is thickest around Gomersal where it forms a prominent hill top, but is thin or absent north-east of there around Gildersome. It is thinner and interbedded with mudstone and siltstone around Batley but thickens below Dewsbury to about 11 m or more of interbedded sandstone and siltstone. South-west of Dewsbury it is a 9 m-thick competent sandstone, but it is thinner and less competent around Grange Moor where it forms two small escarpments.

The coals that lie above the Lepton Edge Rock are collectively known as the Brown Metal Coals. Three seams are conventionally recognised, the First, Second and Third Brown Metal, the First Brown Metal being the uppermost. The succession in its typical development is exemplified by the shafts around Gildersome that show the three seams with separations of 5 to 7 m (Burgess, 1983, fig.2).

Over most of the area the Third Brown Metal is consistent in its development about 15 m above the Middleton Little Coal. It is generally about 0.3 m thick but deteriorates in quality to a carbonaceous mudstone in the area around Howley Park. It has been worked around Howden Clough in the north, in conjunction with the other Brown Metal Coals and in the south where it was commonly referred to as the Stone Coal, it is slightly thicker (0.5 m) and was worked separately around Moor Head west of Emley Moor. Around Emley Moor, it is overlain by sandstone that is continuous with the Birstall Rock, and it is subject to washout (Green et al., 1878) between Thornhill Lees and Savile Town. It is equivalent to the Low Fenton Coal of the Wakefield district (Lake, 1999), although correlations are not entirely certain.

The Second Brown Metal Coal (or Old Hards Coal) was formerly of high economic importance as a source of subanthracitic coal (Wray et al., 1930). At Emroyd Colliery, Thornhill Edge and around Grange Moor, the Second Brown Metal is washed out by sandstone of the Birstall Rock, the washout appearing in plan to have the form of a sinuous channel. North of the Calder, the Second Brown Metal extends into a split seam, previously termed the Two Yard Coal, which is effectively a combination of the Old Hards and the First Brown Metal. The two seams, in combination up to 1 m thick, are recorded in shafts around Gomersal Hill Top, White Lee, Birstall and Birkenshaw. The seams are washed out from areas along the north-east of Smithies Beck at Birstall, the washout extending southeast between Tong Lane End and Batley. The Second Brown Metal re-appears farther east as a thin remnant of the seam beneath the Birstall Rock in the Batley West End Shaft. North of there, at Howden Clough, a thick and fully representative sequence of the Brown Metal Coals was worked opencast. However, identification of the seams may be contentious. The opencast site record at Howden Clough refers to a tonstein about 0.2 m below the top of the lowest of three coals, all of which were assigned to the First Brown Metal Coal. Godwin and Calver (1974, p.428) state that in south Leeds a tonstein occurs within a seam designated as the Second Brown Metal. However, Lake (1999) preferred a correlation of this seam with the Third Brown Metal. If this is the case it would appear that all three Brown Metal Coals are represented at Howden Clough. The seams extend consistently north-west from Howden Clough to Drighlington and Cockersdale. When traced east from Cockersdale to Gildersome and thence towards Morley the partings between the three principal seams each gradually increases to about 8 to 10 m.

The term Birstall Rock (Figure 13) has been applied to any sandstone that overlies any or all of the Brown Metal Coals. The Birstall Rock attains its thickest development in the type area where it is about 30 m thick and consists of up to three leaves of white, cross-bedded fine-grained sandstone with clasts of mudstone and ironstone. From its thickest development in the type section, the Birstall Rock thins dramatically north and west so that it is not represented in sections at outcrop around Birkenshaw. It is absent from successions to the east at Howden Clough, and it is absent or thin in the north-east around Gildersome. The washouts of the underlying coals occur where the sandstone is thickest and has a coarser grain size. Sequences of sandstone up to 15 m thick are developed around Dewsbury and cause washouts in the underlying coals; the thickness of sandstone decreases north-east and south-west. To the southeast, at Inghams Bye Pit, Thornhill, a stacked sequence of sandstones over 16 m thick is developed entirely above the First Brown Metal. A third area of thick development of the Birstall Rock is found around Grange Moor where up to 16 m of sandstone may be present. Between Middletown and Grange Moor the sandstone that overlies the First Brown Metal thickens and cuts down progressively westwards, eroding the First Brown Metal and the Second Brown Metal and merging with the sandstone that overlies the Third Brown Metal.

The main deposition of the Birstall Rock and the washouts of the coals appear to lie along a southerly trending line and indicate a diversion from the accepted southeasterly flow of the fluvial systems proposed on the basis of cross-bedding measurements by Hallsworth and Chisholm (2000). Stacking of channel sandstones in the thick sequences indicates no simple relationship of deposition to differential compaction of sediments or tectonic control. Each thick sequence overlies a differently developed succession of coals and each lies within a different faulted compartment of the Gainsborough Trough.

The highly variable sequence that includes the Brown Metal Coals and the Birstall Rock, is capped by the more uniform and widespread Flockton Thin Coal. This seam is consistent in its development throughout the area north of the Calder where it comprises a lower leaf of 0.6 m separated by a dirt parting, 0.3 to 0.6 m thick, from an upper leaf of 0.2 m. South of the Calder the seam is rarely more than 0.5 m thick. It has been mined extensively underground throughout the district and was extracted by opencast workings in the south around Flockton, Thornhill Lees and Thornhill Edge and in the north at Gildersome Street.

The roof of the Flockton Thin Coal generally consists of fissile mudstone with bivalves and ostracods. These measures may be up to 5 m thick around Batley and Dewsbury. In the north, around Drighlington, and in the south around Emley, the coal is overlain directly by the Emley Rock, a fine-grained, medium-bedded, ripple-laminated sandstone that varies from 1 to 14 m thick. The rock is thickest in the south around Emley where it forms prominent escarpments and extensive dip-slopes, and around Drighlington in the north (Figure 13). In a number of sections the Emley Rock forms much of the cycle below the Flockton Thick Coal. This seam is generally composed of three persistent beds each varying from 0.2 to 0.4 m thick, and separated by dirt and mudstone partings. Over the entire district north of Flockton, the uppermost bed is predominantly a waxy cannel coal that was formerly economically important for its gas and oil content. The main seam was extracted from opencast workings along much of the outcrop south of the Calder, between Thornhill Lees, Thornhill Edge, Flockton and Emley. North of the Calder, opencast sites are limited to Gildersome Street and Upper Batley.

In the south-east around Flockton and Emley, and in the north around Batley and Bruntcliffe, the roof measures of the Flockton Thick Coal are composed of mudstone and ironstone bands with nonmarine bivalves and form the Tankersley Ironstone. The ironstone was extensively worked in medieval times and numerous bell pits and spoil heaps remain in the woods and pastures in the area east of Emley (Wray, 1929). The cycle is capped by the Joan Coal, a thin but widely developed seam of poor quality. It has rarely been mined subsurface although shafts around Bruntcliffe record up to 1.25 m of coal. Opencast workings at Gildersome Street and site investigations around Drighlington and Upper Batley, record a seam about 0.3 m thick lying about 10 m above the Flockton Thick Coal. South of the Calder the Joan Coal has been extracted from more extensive opencast workings around Thornhill Edge and Flockton where it is about 0.6 m thick and lies about 20 m above the Flockton Thick. It was worked underground around Flockton and east of Emley Moor.

Middle Coal Measures

The base of the Middle Coal Measures (the Duckmantian Stage or Westphalian B) is defined at the base of the Vanderbeckei (Clay Cross) Marine Band, which is developed in mudstone that immediately overlies the Joan Coal. The marine band, in this instance 1 m of mudstone containing Lingula, is recorded in boreholes immediately east of the district at Thornhill. From these records, it is inferred to lie beneath the alluvium between Thornhill and Healey. No other records of the marine band are known from the district although site investigations at Overthorpe record dark grey mudstone with shells at a horizon inferred to be above the Joan Coal. About 160 m of Middle Coal Measures strata crop out but are restricted to the eastern margins of the district (Figure 10). The only significant section of strata outcrops in the graben between the Staincliffe Fault and the Soothill Wood Fault (Lake 1999). Named and worked seams of the Middle Coal Measures of the district are listed in (Table 4).

The lowest cycle of the Middle Coal Measures includes the Thornhill Rock, which is exposed widely on the eastern margin of the district where it forms major escarpments with extensive dip slopes. It is a thick, medium-bedded, cross-bedded, fine-grained sandstone that has been quarried in a number of localities. It varies from a single leaf about 40 m thick around Batley and Bruntcliffe (Burgess, 1983) to up to four leaves of sandstone interbedded with mudstone with a total thickness of about 60 m around Gawthorpe. Thin, probably impersistent coals may occur within the mudstone interbeds, as around Batley, or occur below the base as at Earlsheaton. At Howley Park Quarry, a seatearth with a thin coal appear to fill channels in the top of the Thornhill Rock (Burgess, 1983). This poor seam is correlated with one of four thin coals lying between the Thornhill Rock and the Lidget Coal at Swillington in the Wakefield district (Godwin and Calver, 1974; Lake, 1999). The Lidget Coal is up to 0.4 m thick and, in sections where the Thornhill Rock is poorly developed, lies about 25 m above the Vanderbeckei Marine Band. However, it is recorded only in the narrow graben between splays of the Horbury Bridge Fault (Lake, 1999), to the south-west of Flockton.

Around Lower Soothill, between the Staincliffe Fault and the Soothill Wood Fault (Lake, 1999), the Lidget Coal is absent or may have been washed out by sandstone that effectively merges with the Thornhill Rock. Where both seams are present the strata between the Lidget and the Low Haigh Moor Coals are relatively sandy and reach about 26 m in thickness.

The Low Haigh Moor Coal is generally a single coal up to 0.7 m thick. It is known in the district in opencast workings at Hostingley, south-east of Thornhill, and it outcrops north of the Staincliffe Fault at Hanging Heaton, Dewsbury where it is separated from the Top Haigh Moor Coal by 7 to 10 m of sandstone and mudstone. Immediately to the north, around Lower Soothill in the former Solway opencast site, the Top and Low Haigh Moor Coals are mapped together, and occur as leaves of one split seam with a total thickness of 0.9 m.

The Haigh Moor Rock lies close above or rests directly on the Haigh Moor Coals. It is about 10 m thick and, in former quarries at Lower Soothill, consists of massive fine grained sandstone.

Above the Haigh Moor Rock, records of the Soothill Wood opencast sites indicate 40 m of measures that include the Swallow Wood Coal (a thin, split, worthless seam), 27 Yard Coal (0.4 m split seam), Gawber Coal (0.5 m split seam), Beck Bottom Stone Coal (0.7 m split seam) and Warren House (Gawthorpe) Coal (1.5 m split seam). Within these measures, between the Beck Bottom Stone Coal and the Warren House Coal, a 6 m thick sequence of thin sandstones and siltstones interbedded with mudstone represents the Horbury Rock.

Chapter 5 Quaternary

Quaternary deposits cover only a relatively small part of the district. The deposits include glacial till, glaciofluvial sand and gravel, and periglacial or postglacial deposits, such as head, peat, alluvium, alluvial fan deposits, river terrace deposits and landslips. This resurvey has largely confirmed the limits of the deposits as defined during the previous geological survey of the district.

Quaternary history

The landscape of the district results from the action of Pleistocene glacial processes on the subhorizontal, layered, Carboniferous sedimentary strata. Ice sheets invaded the Pennine region at least three times during the Pleistocene, although evidence for earlier glaciations in the Huddersfield district has been all but obliterated by subsequent erosion particularly during the more recent (Devensian) cold periods (Figure 14). Glaciofluvial sand and gravel on erosional benches perched some 40 m above the top of the present-day alluvium have been noted at Exley, near Elland, and Kirklees, (Davis, 1871–1877, Wray et al., 1930). These deposits, resting on a high erosion surface, presumably predate the erosion of the concealed river channels with their fill of late glacial deposits that underlie the present-day alluvium. The Exley and Kirklees sand and gravel deposits may therefore be of late Anglian or early Devensian age. Isolated patches of till on hills around Tong and Moor Head may represent eroded relicts of an older till but have not been differentiated in this work.

The valleys of the Rivers Calder and Colne lie over buried channels that are up to 12 m deep (Figure 15). The channels have U-shaped cross-sections, and are filled in part by glaciofluvial sand and gravel with interbeds of silt and clay. They were probably scoured by glacial meltwaters, and, if ages are reliable, dating of fossil remains from a silt interbedded within gravels at the Oxbow opencast site in the adjacent district (Gaunt et al., 1970) indicates that an initial deepening took place prior to the main late Devensian advance.

The main Devensian glaciation left deposits of till, a grey stony clay, on high ground in the north-eastern part of the district. Subsequently, the entire district was exposed to subarctic conditions south of an ice sheet that built up in the Lake District and southern Scotland during the latest Devensian cold stage. Under these conditions, freeze-thaw processes were active and resulted in the accumulation of a thick mantle of fractured rock and weathered debris. During warmer seasons both the till and the weathering products became unstable and flowed down slopes to form head deposits. Freeze-thaw action on bedrock strata initiated extensive landslips, especially where sandstone beds occurred, dipping outwards above steep mudstone slopes. Climatic fluctuations during the late Devensian were inferred by Keen et al., (1988) from faunal and floral variations at Bingley Bog in the Bradford district.

From the extent of the till deposits, it is inferred that the maximum southward advance of the Devensian ice sheet covered only the upland areas of north-eastern part of the district (Figure 14). However, because of seasonal and other cyclic variations in temperature, the position of the ice front would have been quite unstable with periodic local advances and retreats.

There is no compelling evidence in the district for the existence of a glacial lake during the Devensian, such as Lake Calder as proposed by Wray (1915) and Wray et al. (1930). Site investigations in the Calder and Colne valleys typically record a few metres of silty alluvium or clay resting on up to 10 m of sand and gravel with cobbles and boulders and with scattered beds of stony clay or silt. Laminated clays are rarely recorded from the district and then from only small, isolated deposits.

Many of the glaciofluvial deposits and alluvial gravels include erratics of Lake District origins (Davis, 1874; Spencer, 1896; Simpson, 1901). These have been used to infer the existence of ice lobes and glacial meltwater channels passing through the Walsden gap in Lancashire and entering the Calder drainage system by Todmorden (Jowett, 1914). The presence of Lake District erratics clearly indicates the ultimate derivation of the material, but detailed interpretation of pathways may be unreliable since the debris of earlier advances may be incorporated into later deposits. Jowett and Muff (1904) described glacial lakes in the Aire valley to the north of the Huddesfield district. One of these, ‘Lake Bradford’, was inferred to drain via overflow channels at Wibsey (Odsal) and Rooley, into the Spen valley. Glaciofluvial deposits around Oakenshaw were presumably deposited by these meltwaters. Following the Devensian glaciation, the modern drainage pattern became established, with alluvial deposition within the valleys of Calder and Colne, and associated tributary streams. Along the Calder west of Mirfield, terraces and their associated surface deposits were recognised (Wray et al., 1930), but not differentiated on the published maps. More recently Lake (1999) described two sets of terraces and deposits, 6 m and 3 m above the present alluvium of the Calder to the east of the Huddersfield district. The terraces represent fluvial depositional surfaces which have become isolated on valley sides due to incision of the river systems during the Flandrian. Alluvium represents the river deposits of the current floodplain.

Extensive, although thin, upland peat deposits accumulated on the moors in the west of the district. Landslips are a common feature of the district, occurring in both bedrock and Quaternary deposits. Some landslips may have been initiated during the late stages of the last Devensian cold period, although many are Flandrian in age, and some landslips are still active. Artificial (man-made) deposits are mostly associated with the Industrial Revolution and subsequent development of the district.

Glacial deposits

Till (formerly termed boulder clay) is an unsorted heterogeneous mixture (diamicton) of clay, silt, sand and erratic stones deposited from melting ice by various mechanisms, but without transportation or modification by running water. The main till deposits in the district form extensive, featureless spreads, generally less than 5 m in thickness. Price et al., (1984) recognised a number of different types of till in Wharfedale, including lodgement till, flow till, deformation till and melt-out till. Within the Huddersfield district, the paucity of natural sections and inadequacy of most borehole records precludes any similar differentiation. The deposits are generally restricted to the area around Buttershaw and Low Moor, south Bradford where they consist of weathered yellow stony clay, which is commonly encountered in site investigations.

Glaciofluvial deposits of sand, gravel and boulders occur as small isolated patches, around Mytholmroyd [SE 005 260], Holmfield [SE 084 285], Elland [SE 103 218], Clifton [SE 173 217], Oakenshaw [SE 175 280] and around Huddersfield town centre. They are present both in the valley floors and perched on valley sides. Deposits of similar appearance have been proved in boreholes to occur in the channels beneath the alluvium of the rivers Calder and Colne. The deposits may not all be of the same age or from the same source but all comprise sand and gravel with cobbles and boulders, and are locally bedded, with some thin, laterally impersistent beds of clay.

The perched deposits at Mytholmroyd [SE 005 260], Exley [SE 103 218] and Kirklees Park [SE 173 217] lie in each case some 35 to 40 m above the River Calder. At Mytholmroyd, unstratified sand and gravel deposits form an elevated sloping landform and contain mainly local clasts along with water-worn glacial erratic cobbles of granophyre, andesite, rhyolite granite and Silurian sandstone. They were originally inferred by Law and Simpson (1902) to be of glacial origin but re-interpreted by Wray et al. (1930) as having been deposited from glaciofluvial meltwaters that flowed from Lancashire, cutting gorges through the Pennines, to join the Calder. The deposit at Exley (Elland) contains cobbles and boulders and is less heterolithic than the Mytholmroyd deposit, while that at Kirklees Park is gravel composed of local clasts. The deposits on the lower ground around Elland are markedly heterolithic and appear to merge with the sand and gravel deposits that are continuous downstream from Elland through Brighouse, Mirfield, Dewsbury and Thornhill below the alluvium of the Calder. The base of the alluvial channel slopes gently and evenly from about 70 m above OD around Mytholmroyd to about 55 m OD at Elland and 22 m above OD around Savile Town, and the deposits are generally about 6 to 10 m thick. In profile the channel is rather flat based with steep sides that may be overlapped and concealed by the uppermost alluvial clay and silt.

The perched gravels of Exley and Kirklees were clearly deposited during a time of high flow draining to a high base level. The erosion and drainage of the concealed channel of the Calder took place later during a high-flow regime and to a lower base level than the system that deposited the perched gravels. The lower gravels around Elland and those of the channel fill were presumably deposited under conditions of waning flow and rising base level associated with climatic amelioration in the late Devensian. East of the district, a heterolithic gravel perched at around 50 m above OD, 40 m above the adjacent river near Rothwell, was inferred by Lake (1999) to be of a pre-Devensian age, probably Anglian, whereas he believed the channel deposits to be composite in age.

In the Colne valley at Huddersfield, small deposits of gravel lie at various levels above the present-day flood plain. The highest, at Hillhouse [SE 150 184], is 20 m above the alluvium level (Chisholm, 2000a, c). Others nearby, and downstream near Rawthorpe [SE 166 182], lie just above the floodplain and appear to be continuous with the gravels that underlie the alluvium. Wray et al. (1930) considered all to be of fluvioglacial origin, but was not clear whether they belong to the late Devensian or to an earlier stage.

Glacial meltwater channels with misfit streams cross the Aire-Calder catchment divide at Odsal and Rooley in south Bradford, flowing into the Spen. The meltwaters may be the source of glaciofluvial gravels around Oakenshaw.

Glacial to postglacial deposits

Head is a poorly consolidated deposit derived by downhill movement of drift deposits or weathered bedrock, under the influence of gravity. It may develop during periglacial solifluction and subsequent colluvial processes such as hill creep or hill wash that are locally still active. Head is an unsorted deposit, commonly a diamicton, the composition of which closely reflects that of the source material. The deposits may be difficult to distinguish from weathered bedrock or till, particularly in borehole records. Head is widespread throughout the district, but has been mapped only where it exceeds 1 m thickness, and where it is readily distinguishable from either weathered bedrock or till. The deposits have accumulated in hollows or at the base of steep slopes, such as below the scarp of the Midgley Grit in the upper Ryburn valley [SE 035 163].

Within the area of Namurian strata, extensive deposits of head, up to 9 m thick, have been mapped at Scammonden Water [SE 052 166], Ripponden [SE 045 205] and Norland Moor [SE 058 222]. There are thick deposits of head in the Hebden Bridge area, in Hebden Dale [SD 980 288] and the Calder valley [SD 995 270] where it is up to 19 m thick and consists of sandstone boulders in a sandy clay matrix. In the Hebble valley, north of Mixenden [SE 060 297], a 2 mthick gravel of mudstone fragments lies on the lower slopes below the Rough Rock escarpment. South-east of Mixenden [SE 065 283] and at Copley [SE 085 227], deposits over 5 m thick, of large boulders in a clay matrix described by Wray et al., (1930) as till, are here included as deposits of Head.

Head deposits are usually less common and less extensive in the parts of the district underlain by Coal Measures. However, extensive deposits are present north of Bradley [SE 168 215] and Lower Hopton [SE 195 197] and around Huddersfield town centre [SE 145 170], where boreholes indicate up to 5 m of stony clay.

Lacustrine deposits have been mapped in an enclosed hollow at Dalton Green [SE 171 168], east of Huddersfield, at a site described by Wray et al., (1930) as an abandoned meander of Lees Beck from which the remains of the auroch or wild ox (Bos primigenius) was reported. The deposit lies several metres above the Lees Beck alluvium and has now been classified as lacustrine. The bones are reported on fieldslips as having been discovered in the peaty soil and this suggests that the remains were from the youngest layers at the site. Wray’s description of the lithology (1930, p.133) is not clear, but he makes comparison with a site at Savile Town, where sandy loam with pieces of local sandstone are noted, and with sites at Thornhill Lees and Northorpe where terrace deposits are overlain by 1 to 2.5 m of clay. The Bos primigenius identification may be suspect, but since aurochs are reported from deposits ranging from pre-Devensian to Flandrian (Aitkenhead et al., 2002), a Flandrian age can be inferred for the deposits.

Landslides are a common feature of the district having developed where natural slopes are steep (usually in excess of 10º). Other contributory factors include the presence of deeply weathered or fractured, fissile mudstone (especially if particularly fine-grained), or a permeable water-bearing sandstone capping an impermeable mudstone (particularly if the dip is towards the valley axis), or the presence of springs or seeps (Plate 4a) and (Plate 4b).

Landslides are particularly common on the steep north or east-facing slopes of the major escarpments and this suggests that slope aspect may also be a contributory factor. These factors could be conducive to the initiation of new landslides or reactivation of existing ones, given the intervention of a de-stabilising mechanism such as excavation, loading, river erosion or significantly higher rainfall. Landslides of the Calderdale district were assessed by Hobbs (1997), by air photographic survey and field checking.

Landslides have occurred below escarpments of Kinderscoutian or Marsdenian sandstones in Luddenden Dean [SE 022 290], the Hebden valley [SD 987 293] Hebden Bridge [SD 980 273], Mytholmroyd [SE 005 265], Erringden Moor [SD 995 250], Rishworth Moor [SE 005 176], and Buckstones Moss [SE 005 145]. Landslides associated with the Rough Rock escarpment have occurred in the Hebble valley [SE 067 275], Norland Town [SE 072 225], Scapegoat Hill [SE 095 170] and Armitage Bridge [SE 128 140]. Landslides are less common on Coal Measure terrain, except on the escarpments of the Elland Flags in Shibden Dale [SE 095 275] and Ainley Top [SE 130 190] and on Grenoside Sandstone north of Norwood Green [SE 130 275] and [SE 137 278]. It may be significant that many of the landslides described lie where major sandstones overlie sequences of particularly fine grained fissile mudstone with marine bands.

Scree or talus deposits have been mapped on the steep slopes of the major escarpments of the Millstone Grit sandstone units. The deposits accumulated mainly as rockfalls from crags and consist of clast-supported sand, gravel and blocks, commonly over 3 m in length. The deposits themselves are up to several metres thick and may be intermixed with debris flow from rock-slides and hillwash. Because of this, deposits of scree may pass laterally into deposits of head and landforms of vegetated fossil scree may be indistinguishable from landforms of head. The principal areas of talus are below the crags at Buckstones Edge [SD 971 263], Hebden Dale [SD 973 300] to [SD 990 290], Henry Edge [SD 975 232], Crimsworth Dean [SD 990 303], Scar Wood [SE 082 235], Norland Moor [SE 055 217] and Lindwell [SE 093 220].

Postglacial deposits

River Terrace Deposits have been mapped only in the valley of the river Calder downstream from Mirfield. Lake (1999) described the Calder terraces and their deposits and has discussed their composite nature, describing occurrences of terrace gravels interstratified with laminated lacustrine clays of Devensian age, as well as occurrences of gravel with dated mid-Devensian remains (Gaunt et al., 1970). The deposits around Ravensthorpe, Thornhill Lees and Savile Town lie at elevations of 40 to 50 m above OD, up to 10 m above the alluvium of the present-day river, and consist of up to 2.5 m clay or sandy silt with lenses of gravel, resting on 2 to 5 m of interbedded sand and gravel. The deposits rest on a bedrock surface that forms a concealed sloping ramp that is steeper near the outer margin and toward the centre of the alluvial channel.

Alluvium forms wide, flat spreads in Calderdale and the Colne valley, where it usually consists of grey to greybrown silt and clay with lenses of sand, gravel and peat. Narrow discontinuous tracts of thin alluvium lie along the tributary streams, Hebden Water, Hebble Brook, Cragg Brook, Red Beck, Clifton Beck, Spen River and Hey Beck, along the northern side of the Calder, and Ryburn River, Black Brook, River Holme and Lees Beck flowing from the south. These deposits are typically heterogeneous and comprise brown silt and fine sand with lenses of gravel. Organic clay at the margins of the main flood plain probably represents deposits of former ox-bow lakes (Price et al., 1984). The alluvium of the main valleys of the Calder and Colne overlies deposits 8 to 10 m thick of sand and gravel that fill concealed channels. The deposits of the channels are indistinguishable from the lower beds of alluvium or from the sand and gravel of the terrace deposits described above. They may also include glaciofluvial deposits (see above).

Alluvial fan deposits have been recognised on the River Calder and Spen where minor tributaries meet the main rivers and are mostly of small extent. At Hopton Bridge [SE 208 188] there are sloping fans of clay, sand and gravel where the Valance Beck and the adjacent beck join the Calder. Near Hopton Bridge, surface layers of clay 1 to 2.5 m thick were formerly extracted for brick-making.

Peat forms extensive, thin veneers on the moorland areas in the south-west and north-west of the district, such as Buckstones Moss, Moss Moor, Rishworth Moor, Blackstone Edge, Soyland Moor, Withens Moor, Ovenden Moor, Warley Moor, Shackleton Moor and Spa Clough Head. Upland peat accumulated in areas of acid soils through the decomposition of dead plant material, under conditions of relatively low temperatures, poor aeration, water saturation and low evaporation. The cooler, wetter climatic conditions optimal for the formation of the peat pertained between 7500 and 2000 years BP when waterlogging of the soils killed the trees of the forest cover that are now preserved in the basal layers of the peat (Aitkenhead et al., 2002). Palaeolithic flint implements are recorded from thin sands below the peat while Neolithic flints are associated with the basal layer of tree debris (Wray et al., 1930). Advances in the peat cover in the post-Roman period, for instance covering the Roman road at Blackstone Edge (Wray et al., 1930), are inferred to have resulted from changes in agricultural practices (Aitkenhead et al., 2002).

On the relatively well drained, heather-covered, sandstone escarpments the peat rarely exceeds 1 m in thickness and in many places only a dark peaty soil is formed. On those generally poorly drained moorlands that are underlain by mudstone, the peat may be up to 3 or 4 m thick, or exceptionally, as at Blackstone Edge, up to 7 m thick (Wray et al., 1930). The distribution of the deposits was determined from aerial photographs, used in conjunction with field mapping. The extent of peat mapped during this resurvey is significantly reduced in comparison with that of the previous survey which included extensive areas of peat less than 1 m thick. In addition, since the time of the previous survey there has been active erosion to form a network of gullies, or ‘haggs’, up to 3 m deep as seen at Linsgreave Head [SD 980 218]. The peat was formerly worked in the west of the district, often with detrimental effects to the moorland habitats, for example Stake Hill [SE 02 33]. Peat working, heather burning and air pollution may all contribute to increased peat erosion and reduction in the extent of the deposits.

Artificially modified ground

The long history of industrial development in the district has left an extensive legacy of human modification of the natural environment. The man-made deposits shown on the map represent those that were identifiable at the date of survey. They were delineated by recognition in the field and by examination of documentary sources, in particular modern and historic topographical maps, aerial photographs and site investigation data. Only the more obvious man-made deposits can be mapped by these methods and the boundaries shown may be imprecise. Only deposits in excess of 100 m wide, and known to be broadly more than 1.5 m thick are shown.

Made ground represents areas where the ground is known to have been deposited by man on the natural ground surface. The main categories include: civil engineering constructions such as road and railway embankments and reservoir dams; spoil from mineral extraction industries such as colliery and quarry spoil; building and demolition rubble; waste from heavy industries such as foundry sand, slag from ironworks, ashes and cinders from textile mill boilers; domestic and other waste in raised landfill sites, including those occupying topographical depressions such as glacial meltwater channels at Odsal [SE 164 296]. The most extensive areas of made ground are in the main urban centres of Bradford, Huddersfield, Halifax and Dewsbury. In these areas the topographic features associated with specific areas of made ground, especially colliery spoil, have been smoothed over prior to development. Construction has commonly taken place on compacted rubble and deposits left by previous uses.

Infilled ground comprises areas where the natural ground surface has been removed and the excavation partly or wholly backfilled with man-made deposits. Mineral excavations and disused railway cuttings have been used in the district for the disposal of waste materials, and some quarries have been partly filled with spoil after the completion of mineral extraction. However, in most cases quarrying operations produced voids suitable for infilling with imported waste. The common types of fill include excavation waste, construction and demolition waste, domestic refuse and industrial waste. Where quarries and pits have been restored and either landscaped or built on, there may be no surface indication of the extent of the backfilled void. In such cases, the location of these sites is taken from archival sources, in particular old topographical and geological maps.

Worked ground and disturbed ground are shown on 1:10 000 scale geological maps but not on the 1:50 000 scale geological map. Worked ground is used to represent excavations that have remained open, for example in unfilled quarries and pits, excavations for roads and railways and general landscaping. Disturbed ground is indicated on maps where ill-defined surface mineral workings include a complex association of excavations and made ground, and in some cases subsidence induced by near-surface mineral workings. Sites include, for example, areas of bell pits and shallow mine workings at Coalpit Hills, Shelf [SE 120 294], and Low Moor [SE 167 287].

Chapter 6 Structure and concealed geology

In earliest Carboniferous times a collision-type orogenic belt developed south of the British Isles, on the south side of the closing Rheic Ocean. This is thought to have led to back-arc extension in areas north of the ocean with the development of a major Dinantian rift basin system in northern England. Extension was much diminished in Namurian and Westphalian times and a regional ‘post-rift’ or ‘sag’ basin developed. In latest Carboniferous times, final closure of the Rheic Ocean culminated in the Variscan Orogeny, with large-scale thrust and nappe emplacement in Belgium, northern France and southern Britain. On the foreland to the north of the Variscan fold belt, deformation was much less pervasive, and in northern England was largely restricted to basin inversion, with partial reversal of the some earlier Carboniferous basin controlling normal faults and associated hangingwall folding. Numerous minor faults also developed during this period. Subsequent to this, in Mesozoic and Cainozoic times, regional tilting was associated with subsidence of the North Sea Basin and imparted a gentle easterly dip to the eastern side of northern England, including the Huddersfield district.

Deep structure

The district lies on the eastern limb of the north-trending Pennine Anticline (Figure 16). Strata on this eastern limb have a general eastward dip of 2º to 5º. The structure of the Pennine Anticline has been described in detail by Evans et al. (2002) who concluded that the fold represents a positive inversion structure developed over a north-south basement fault, reactivated and subjected to oblique slip during northwest-directed Variscan compression.

The main deep structural elements of the district are shown in (Figure 16). Most of the district is underlain by the Dinantian Huddersfield Basin that lies between the Holme High, immediately south of the Huddersfield district, and the Askern-Spital High that underlies the extreme northeast of the district. The southern margin of the basin is defined by the Holme Fault, a down-to-the-north, normal fault with an estimated throw of about 1100 m at the base of the Dinantian (Kirby et al., 2000). Within the basin in the north-east, the Morley-Campsall Fault and the Denholme Clough Fault appear to be surface expressions of a pair of basement graben that forms the deepest part of the basin in a north-westward extension of the Gainsborough Trough. The Rishworth-Stainland Fault Zone appears to overlie other down-to-the-north, normal basement faults that trend, east-north-east from the Pennine Anticline towards the Morley-Campsall Fault. The maximum throws of the deep faults are in the order of 400 m at the base of the Dinantian. The Dinantian carbonate sedimentation of the Holme High may have extended northwards between the Holme Fault and the Rishworth-Stainland Fault Zone, particularly in the vicinity of the Pennine Anticline. The Todmorden Smash Belt (Wright et al., 1927) trends north-west parallel to the Morley-Campsall Fault in the western part of the district where it displaces the Pennine Anticline sinistrally (Evans et al., 2002), and was identified in deep seismic profiles by Kirby et al., (2000). In the area between the Todmorden Smash Belt and the Denholme Clough Fault no major faults have been interpreted on seismic profiles, and the top of the basement surface appears to slope smoothly to the south-east. The Askern-Spital High, north-east of the Morley-Campsall Fault, is part of the regional Furness-Ingleborough-Norfolk Ridge (Kirby et al., 2000).

Near-surface structure

Dips of up to 50º or more occur in the vicinity of major faults, such the Tong Fault, Bowling Fault, Kirkburton Fault and Rishworth-Stainland Fractures, but relatively minor faults such as the Fenay Bridge Fault may also have associated folds. One such major structure lies at Gildersome, south-west of the Tong Fault (Morley-Campsall Fault Zone) where the Elland Flags emerge from beneath some 160 m of younger strata, dipping away from the fault at 30º. Wray et al., (1930) describes a 500 m-wide anticline on the hangingwall block of the Bailiff Bridge Fractures, between Shelf and Bailiff Bridge. Chisholm (2000b) described folding parallel to and on the footwall of the Kirkburton Fault that he inferred to be compressional in origin.

Faults may occur as single discrete planes, or as zones up to several tens of metres wide containing several fractures. The portrayal of such a fault zone as a single line on the map is therefore a generalisation. As faults are rarely exposed in the district, their position may be based on the interpretation of topographical features, bedrock exposures, site investigation data and underground mining data. This evidence is rarely sufficient to locate the surface position of a fault precisely. In areas of thick and extensive superficial deposits, the positioning of faults relies almost entirely on projection from underground mining information.

The district has been affected by extensive faulting at surface; the dominant fault trends are north-west and north-east with less common but significant major east-west structures. The faults display dominantly normal and strike-slip displacement. The surface faults are considered to be late Carboniferous features, but the east-west trends may reflect control by earlier basement structures. Only the north-east and north-west-trending faults extend into Permo-Triassic strata to the east (Lake, 1999) indicating reactivation in Mesozoic times. Neogene (Miocene) compressive stresses may also have resulted in reactivation of many of the faults. Slickensides found on north-west-trending fault and joint planes are invariably subhorizontal. The main faults affecting Carboniferous strata are illustrated in (Figure 17) and described in (Table 5); the amount of downthrow at surface is estimated from field relations or, within the area underlain by Coal Measures, from mining data.

The Morley-Campsall Fault Zone, the Denholm Clough Fault-Cleckheaton Fractures (Figure 16), Bailiff Bridge Fractures and Rishworth-Stainland Fault Zone (Figure 17) appear to partition the district into areas with differing fault patterns.

The Rishworth Stainland Fault Zone is essentially a narrow graben structure developed above an east-west basement fault identified from seismic profiles by Kirby et al. (2000), parallel to the Holme High and Holme Fault (Figure 16). The zone extends eastwards as a graben along the Staincliffe Fault, which turns south-east to join the Roundwood-Thorntree Hill Fault Zone described by Lake (1999) in the Wakefield district.

North of the Rishworth-Stainland Fractures, a series of grabens or half grabens, including the Hipperholme Fault, Illingworth Fault and Rake Head-Soil Hill Fault, run east-west parallel to the Holme High. These faults extend eastwards to the Bailiff Bridge Fractures but die out to the west or swing south-west to intersect the Crow Hill Fault, part of the Todmorden Smash Belt. South of Halifax the half grabens of this array downthrow to the north; north of Halifax they downthrow to the south, effectively forming a broad, shallow structural low. The Illingworth Fault, and possibly the Rake Head-Soil Hill Fault, may extend as broken lineaments across the Gainsborough Trough.

The Tong Fault is one component of the Morley-Campsall Fault Zone that lies above a major line of partition within the basement (Kirby et al., 2000), and defines the north-east margin of the Gainsborough Trough (Figure 16). Kirby et al. (2000) indicates a basement fault on the south-west side of the Gainsborough trough, forming a graben with the Morley-Campsall Fault Zone. This fault broadly underlies the Denholme Clough Fault and Bailiff Bridge (northern part) and Cleckheaton Fractures.

Within the area of the Gainsborough Trough, between the Morley-Campsall Fault Zone and the Denholme Clough Fault and Cleckheaton Fractures, subordinate faults run east-south-east subparallel with the main faults or northeastwards at an obtuse angle; in the north a few faults trend east-west. The north-east orientation is consistent with sinistral transpression under regional shortening, oblique and anti-clockwise to the axis of the Gainsborough Trough, during Variscan inversion. This displacement is similar to the throw of the Pennine Anticline across the Todmorden Smash Belt as described by Evans et al. (2002). A number of the north-east-trending faults, including the Hunsworth Fault and Bruntcliffe Fault, occur with adjacent subsidiary faults, and form extensive but narrow grabens, well known from mine workings (Wray et al., 1930). Similar narrow grabens were noted by Lake (1999) in the Wakefield district.

To the south-west of the Gainsborough Trough, numerous splay faults, including the Mirfield Moor Fault and Roberttown Fault, diverge south-south-east from the Bailiff Bridge and Cleckheaton Fractures. These splays, mostly with downthrow to the north-east, effectively form a stepped margin to the basement trough. The named faults intersect and displace the Rishworth-Stainland Fractures around Mirfield, while other unnamed faults terminate against them. The trend of the faults may reflect local basement fabric or result from transpression within a local variation of the Variscan compressive field around irregular polygonal basement blocks.

There is some evidence for fault movement during Namurian and Westphalian sedimentation. Waters (2000) described thickness variations within the Millstone Grit across the Denholme Clough Fault (in the area of Oxenhope at the southern edge of the Bradford district) that suggested syndepositional movement on the fault during Kinderscoutian and Marsdenian times. This structure is contiguous with the Bailiff Bridge Fractures of the Huddersfield district (Wray et al., 1930). Variations in thickness of some Coal Measures sandstones, such as the Birstall Rock and Lepton Edge Rock, and coal seams such as the Middleton Little Coal and Brown Metal Coals, may indicate structural control of sedimentation. However, the influence on sedimentation of differential compaction of underlying strata or basin and channel morphology (Rippon, 1996) is difficult to eliminate from an assessment of structural controls.

Concealed geology

Subsurface data is restricted to a loose grid of seismic lines in the south-west quadrant of the district and a scattering of boreholes. In general, the seismic profiles are of reasonably high quality and provide reliable imaging down to the base of the Dinantian. Additional seismic data in the surrounding region enable the extrapolation of gross subsurface structure into the district. The boreholes are mostly quite shallow, commonly terminating in the Coal Measures, though a few penetrate into upper Namurian strata. Although no boreholes in the district reach the Dinantian succession, to the south of the district the Wessenden Borehole penetrated 600 m of Dinantian strata before intersecting epizonal green phyllites of possible Cambrian age at 1128 m (Merriman et al., 1993).

The structural architecture of the Dinantian rift system is discussed in Chapter 2 and structures within the basement and Dinantian strata are illustrated in (Figure 3) and (Figure 4).

Within the Huddersfield district, post-rift Namurian and Westphalian strata lie at outcrop and dip gently to the east over the Huddersfield Basin. Detailed subsurface mapping of the depth to the base of these units has not been made, except along the line of cross-section. Here the base of Westphalian strata locally reaches a depth of 300 m below OD. The base of Namurian strata is less well constrained, but is believed to exceed 1200 m below OD in places.

From the available data, there is no strong evidence in the district of basin inversion. Characteristic and unequivocal hangingwall folds above the larger normal faults are rarely seen, though the possibility of reverse movements along the steeply dipping fault splays from the Pennine Line has been inferred from seismic profiles (Evans et al., 2002). It may be that the district was not in general strongly affected by Variscan basin inversion: nevertheless, if more extensive seismic data were available, instances of fault reversal and related folding may well come to light.

Seismic interpretation

The southernmost 8 km or so of the cross-section on the published geological map are quite well constrained by surface information and depth-converted seismic data. The latter, calibrated by the Wessenden and Marsden boreholes in the Glossop district, provide satisfactory imaging down to Caledonian basement. North of this, the cross-section is constrained principally by outcrop information and boreholes. The section passes through the following key boreholes: Raistrick, Woodvale Mills, Brighouse and Moorlands Mill Birkenshaw. Important additional stratigraphical control is provided by the Wortley Borehole, some 500 m north-east of the north end of the section. A limited amount of detailed subsurface stratigraphical extrapolation has been attempted for the upper part of the Namurian succession. This was based on borehole information and thicknesses exposed in the southern part of the district. In the absence of other information, fault dips were assumed to be roughly 65º, with appropriate corrections made for vertical exaggeration and also for any obliquity to the line of section. The deeper part of the section is not so well constrained. Northward extrapolation from the seismically imaged part was carried out, based on the structural form of the shallower strata, with further control provided by regional extrapolation from seismic data to the north and east of the district (Kirby et al., 2000). This enabled the gross subsurface structural configuration to be constructed. Of necessity however, details of deep subsurface faulting are conjectural, and, in particular, Dinantian fault throws may well be conservative (for example the Morley-Campsall Fault may have a considerably greater displacement at base Dinantian level than shown).

Geophysical interpretation

The Bouguer gravity anomaly map, within the Huddersfield district (inset map Sheet 77 Huddersfield, Solid and Drift Geology), shows a strong north-south contour trend with a pronounced eastward decrease in Bouguer anomaly values in the western part, and a relatively flat-bottomed low in the eastern part. Gravity stripping (correction of the gravity field for the effect of the known Carboniferous rocks; information from A Walker, 1997) has shown that the eastward decrease cannot be entirely due to the lower density Carboniferous rocks in the Huddersfield Basin but is contributed to by higher density basement to the west and south. The change in basement density may well occur across the Pennine Line. Based on the absence of a magnetic response at the interface, J C Cornwell (personal communication, 2003) concluded that both the higher and lower density units are probably sedimentary in nature. West of the Pennine Line the major Bouguer anomaly high and a low are coincident with the Central Lancashire High and the Rossendale Basin respectively. North-east of the district, beyond the Askern-Spital High, Bouguer anomaly values decrease into the Harrogate Basin.

To the south of the district, an east-west zone of steep gravity gradients, with values decreasing to the north, clearly indicates the trend of the Holme Fault, a major Lower Carboniferous growth fault, marking the southern boundary of the Huddersfield Basin. To the south is the Holme High, a Dinantian shelf area of shallow-water carbonates (Evans and Kirby, 1999) but the rounded magnetic anomaly suggests that the high is underlain by a magnetic, possibly igneous, body (J C Cornwell, personal communication, 2003).

Magnetic anomaly map

The north-west-trending anomalies which cross the northeast corner of the district are closely associated with the Morley-Campsall-Askern-Spital Fault Zone and the parallel Denholme Clough Fault. The magnetic anomaly over the Morley-Campsall structure continues as far north as the Pendle Fault in north-west corner of the Bradford district, and persists for as much as 40 km to the south-east. The source of the anomaly is not known, but the form of the anomaly suggests the presence of a steeply dipping igneous body. (Waters, 2000).

The western and southern margins of the district are bounded by larger, longer wavelength magnetic highs. To the south there are coincident Bouguer gravity anomaly highs over the Holme High and Heywood High (see above). These anomalies form part of a belt of longand short-wavelength north-west and east-west-trending magnetic anomalies, which extends into the region of Charnian rocks in central England and beyond. Some of these anomalies are related to Lower Carboniferous (Dinantian) volcanic centres, while others are correlated to Lower Palaeozoic rocks such as the South Leicestershire Diorites and the Mountsorrel Granodiorites (Evans et al., 2002). A borehole south of the district, Wessenden, (SE00NE/7) drilled on the crest of the Holme High encountered basaltic rocks in the Dinantian succession.

The pronounced magnetic anomaly just beyond the south-west corner of the district lies close to the intersection of the Pennine Line and the Heywood-Holme Fault. Its form suggests a deep source, at least below the base of the Carboniferous, and J C Cornwell (personal communication, 2003) suggests that its geophysical properties are consistent with a granodioritic composition.

Earthquakes

Geological faults in this area are of ancient origin and are currently thought to be inactive. However, the district, in common with other parts of Britain, has been affected historically by minor earthquakes. None of the surface faults in the district can be correlated with the seismicity.

This area lies on the eastern flank of a zone of seismic activity running roughly north-east from Merseyside towards the Skipton area, on the western side of the southern Pennines. The largest earthquake in this zone (4.8 ML and a depth of focus of about 13 km) occurred on 30 December 1944 at Skipton, which is to the north of the Huddersfield district, but it was generally felt in this area (Musson, 1994). The largest earthquake close to the Huddersfield district was the Todmorden earthquake of 7 March 1972 (4.0 ML), (Tillotson, 1974). This event had an epicentre in the Todmorden-Bacup area and caused minor damage at Bacup, Chadderton, Middleton and Rochdale. In one case, a terrace house had to be evacuated. As with the rest of the UK, seismic activity in this area is due to reactivation of old deep structures that are favourably oriented with respect to the direction of maximum compressive stress associated with Atlantic ridgepush; identification of individual ‘active’ faults is not possible.

Chapter 7 Applied geology

This chapter provides a brief insight into the earth science issues that should be taken into account by planners, developers and other interested parties involved in planning and development processes. Geological factors have had a significant role in the industrial expansion of Huddersfield, Halifax, Bradford and neighbouring towns. Former mining and quarrying associated with the development of heavy industry have left areas of derelict land. By considering the natural and artificial ground conditions at an early stage in the planning process appropriate action may be taken to ensure that development is compatible with aspects of the site, and that necessary mitigation measures are taken prior to development. Geoscience information may also be used to identify opportunities for development, particularly in respect of leisure, recreation and protection of sites of nature conservation interest. The key issues, given below, were identified and discussed in detail by Waters et al. (1996b) as of particular significance in the Bradford Metropolitan District, which occupies part of Sheet 77 Huddersfield district. They are considered to be applicable to the whole of this district and include:

• mineral resources
• surface mineral workings
• engineering ground conditions
• subsidence risk due to undermining
• slope stability
• pollution potential and leachate movement
• gas emissions
• water resources
• conservation sites

Mineral resources

Mineral resources in the district are those minerals that can be won at or near to the surface, as the economics of underground mining are unlikely to be favourable in the future. The main factors hindering extraction are: significant thicknesses of overburden, including Quaternary and artificial deposits; sterilisation of resources by urban development; conflicts with other forms of land-use, and possible detrimental effects on the landscape. In addition, extraction of mineral resources can lead to problematical engineering ground conditions, depending on the types and methods of infilling, and can act as a constraint to future development of a site. The main sites of mineral extraction active at the time of survey are shown in (Figure 18).

Coal has long been mined in the district, perhaps as early as the 13th century. Mining probably reached its zenith in the late 19th century but there is no longer any coal production in the district today. Any future commercial interest in the coal resources of the area is likely to be confined to those that are suitable for opencast extraction. Such sites are limited in number and are likely to be small. The generally high relief of the area means that high overburden to coal ratios are likely to be encountered and, in addition, there are many physical limitations on the extent of possible sites due to surface developments such as roads, railways and urban areas. Some minor potential may remain where urban sites are being redeveloped.

Almost all of the coal seams have been mined in the past. Those coal seams that worked by opencast methods include: Warren House, Beck Bottom Stone, Swallow Wood, Top Haigh Moor, Joan, Flockton Thick, Flockton Thin, Brown Metals, Middleton Little, Middleton Main, Wheatley Lime, Middleton Eleven Yards, Blocking, Top Lousey, Linfit Lousey, Shertcliffe, Whinmoor, Black Bed, Better Bed, Hard Bed and Soft Bed. Deep mining ended in the late 1980s with the closure of the former British Coal deep mines at Caphouse, Denby Grange and Emley Moor. The Caphouse and Denby Grange collieries were connected underground in 1980-81 and the two mines merged. Mining operations ceased in 1987 with the exhaustion of reserves, but Caphouse Colliery has been converted into the National Coal Mining Museum of England. The workings date from at least 1789, and the colliery has the oldest coal mine shaft still in everyday use in Britain today.

Natural gas and oil are common as traces in the Carboniferous rocks of the district and during the 19th century oil was produced from the cannel coal portion of the Flockton Thick Coal. Natural gas has been encountered in boreholes penetrating Namurian and Westphalian sandstones at a number of sites around the Huddersfield urban area. In some instances, even within the last few decades, explosions have occurred when gas has been accidentally ignited in enclosed spaces. In historic instances gas under high pressure was intersected in Namurian sandstone traps (Wray et al., 1930) and boreholes drilled in the early 20th century were still seeping gas some 60 years later.

Fireclay formed the basis of an important extractive industry in Britain in the 19th and first half of the 20th centuries. Originally, fireclays were valued as refractory raw materials, because of their relatively high alumina and low alkali contents, and were widely used in the production of firebricks and other refractory goods. Subsequently they were also used in the manufacture of salt-glazed pipes, sanitaryware and pottery. Demand for fireclay for these applications has, however, declined markedly since the late 1950s, most notably for refractory use, where higher quality materials are now required. Salt-glazed pipes have also been replaced by vitrified clay pipes, which utilise Coal Measures mudstones. However, some fireclays have a relatively low iron content compared with other clays, and today they are principally valued for the production of buff-coloured facing bricks.

Fireclays are seatearths, the fossil soils on which coal forming vegetation once grew, and underlie most coal seams. Fireclays are, therefore, generally confined to coalbearing strata. There is no relationship between the thickness of a coal seam and its underlying seatearth, which is usually a thin bed (less than 1.5 m) consisting of unbedded mudstone with rootlets. However, seatearths include all grades of sediment from mudstone (seatclay) to sandstone (ganister). Ganisters, or high silica sandstones, are comparatively rare, but they were also formerly worked for the manufacture of silica refractories.

Today the term ‘fireclay’ is used to describe seat-earths or seat-clays that are of economic interest, and they are generally named after the overlying coal (Highley, 1982). They exhibit a wide range of mineralogical composition, but consist essentially of the clay minerals kaolinite and hydrous mica, together with fine-grained quartz in varying amounts. The relative proportions of each have a marked effect on the ceramic properties of the clay. Carbon and iron are present as impurities.

Until the advent of opencast coal mining during the Second World War, fireclay was produced mainly by underground mining. Mining declined rapidly thereafter, and today fireclay is obtained almost entirely as a by-product of opencast coal mining. The only surviving fireclay mine now operating in Britain is in the Shibden valley, near Halifax, where the Hard Bed fireclay is extracted. This unusual fireclay has been used for nearly 200 years in the manufacture of glasshouse pots — a refractory pot used for melting speciality glasses such as lead crystal glass. Fireclay from the Shibden mine is blended with similar clay quarried near Oxenhope, near Keighley. The Hard Bed fireclay is a siliceous clay (Table 6) with low alkali and iron content. The advantage of a siliceous clay with a low iron content is its ability to dissolve into the glass without causing contamination.

In the past fireclays have been worked at many horizons in the area, but the Shibden mine is the only fireclay operation that has been active for many years. The highly aluminous and refractory 36 Yard fireclay was mined until the 1980s at the Park Nook mine near Halifax, and the fireclay to the Hard Bed Band Coal was also mined at the Ashgrove No. 1 mine near Elland for the manufacture of salt-glazed pipes. The Hard Bed fireclay was extracted by opencast workings at Boothtown, Halifax. The Pot Clay fireclay that overlies the Rough Rock and forms the seatearth of the Pot Clay Coal was formerly worked extensively for the manufacture of common pottery and refractory products at Salendine Nook, Park Nook and Lockwood. The fireclay associated with the Better Bed Coal was formerly extracted along with the coal from opencast workings north of Tong and in the neighbourhood of Farnley. Around Cockersdale and Howden Clough fireclays were worked opencast in association with the Brown Metal Coals.

Brick clay and mudstone are used mainly in the manufacture of structural clay products, such as facing and engineering bricks, pavers, clay tiles and vitrified clay pipes. Of these brick manufacture consumes by far the largest tonnage. Clay may also be used as a source of constructional fill and for lining and sealing landfill sites. The suitability of a clay for the manufacture of structural clay products depends principally on its behaviour during shaping, drying and, most importantly, firing. This behaviour will largely dictate the final properties of the fired product including its strength, porosity (water absorption), durability and aesthetic qualities.

Small brickworks, mainly producing ‘common’ bricks from locally won raw materials, were formerly a common feature in many industrial areas of Britain. However, in the last two or three decades there has been a major rationalisation of the brick industry, which is now based on a small number of larger plants operated by a limited number of companies. With the demise of the ‘common’ brick, the main products are now high-quality facing bricks, engineering bricks and related products such as clay pavers.

Modern brickmaking technology is highly dependent on raw materials with predictable and consistent firing characteristics. In addition, while most brickworks were typically supplied from a single quarry adjacent to the plant, the trend is now towards using clays from a variety of sources and some clays, particularly fireclays, are transported long distances for brick manufacture. Blending different clays to achieve improved durability and a range of fired colours and aesthetic qualities is an increasingly common feature of the industry.

Mudstone occurs extensively in the area within the Millstone Grit and Coal Measures. The main constraint on the potential use are overburden to clay ratios, and carbon and sulphur levels. The last two are critical to firing performance. Excessive carbon can cause the interior of the ceramic product to ‘heart’ or turn blue as the carbon reduces iron oxides from the ferric to the ferrous state. In extreme cases, this can lead to ‘bloating’ as the gases generated within the body are trapped in a viscous glass, resulting in distortion of the product. These reactions are more likely to occur where fast-firing cycles are used, particularly in dense bodies produced by the extrusion process for shaping. Low carbon clays are, therefore, generally preferred with up to 1.5 per cent carbon generally acceptable. Maximum sulphur is about 0.2 per cent.

Clay bricks are produced at only one site in the area, the Calder Brickworks [SE 123 217], near Elland. Carboniferous mudstones from an adjacent quarry in the Lower Coal Measures are used as the sole feedstock for the manufacture of facing bricks by the extrusion process. On the extreme eastern boundary of the district, Middle Coal Measures mudstone overlying the Thornhill Rock is worked at the Howley Park quarry [SE 262 255] for the manufacture of facing and engineering bricks, and clay pavers. The adjacent brickworks just outside the district uses mainly the extrusion process for brick forming. Fireclays are imported on to the site for the manufacture of buff-coloured facing bricks, as are mudstones for the production of blue bricks, which are produced by firing the kiln under reducing conditions. Lower Coal Measures mudstones were until recently extracted at the Kirkheaton [SE 186 174] and Fenay Bridge (Spa Green) [SE 184 158] quarries and Mirfield Moor [SE 197 215] for the manufacture of facing bricks. Brick clay quarries provide important sites for landfill operations.

Sand and Gravel are defined on the basis of particle size rather than composition. In current commercial usage, the term ‘gravel’ is commonly used to define particles between 5 and 40 mm and the term ‘sand’ for material that is finer than 5 mm, but coarser than 0.075 mm. The principal uses of sand are as fine aggregate in concrete, mortar and asphalt. The main use of gravel is as coarse aggregate in concrete. Substantial quantities of sand and gravel may also be used for constructional fill.

The deposits of sand and gravel are accumulations of the more durable rock fragments and mineral grains, which have been derived from the weathering and erosion of hard rocks by, for example, river action. The properties of gravel, and to a lesser extent sand, largely depend, therefore, on the properties of the rocks from which they were derived, in this district, largely Carboniferous sandstone. However, river action is an effective mechanism for wearing away weaker particles, as well as separating different size fractions.

Sand and gravel resources in the district are relatively small, and limited to areas of alluvium, river terrace deposits and buried glaciofluvial deposits present in the Calder valley. Alluvial gravels have been worked until recently for aggregate around Ravensthorpe, in the Calder valley. The alluvium and river terrace deposits comprise silt and fine sand with gravel lenses. These deposits may be underlain locally by valley fill or glaciofluvial deposits, which in the Calder valley consist predominantly of gravel with sand lenses. However, many resources are now largely inaccessible as a result of extensive industrial developments.

Natural sands, derived from the weathering and erosion of rocks, are the most commonly used sources of fine aggregate for construction purposes. However, crushing and screening hard rocks to produce fine-grained materials can also produce sand. Fine aggregate produced in this way can be used as an alternative to natural sands. A number of the sandstone quarries in the area produce both fine and coarse aggregate in this way for the manufacture of reconstituted building stone and paving flags. Some of the sand is also sold for constructional use.

Sandstone is the principal mineral currently extracted in the district, and demand for this resource is likely to continue in the future. The sandstones of the Millstone Grit and Coal Measures of Yorkshire are marketed under the generic term ‘York Stone’. The main resources identified are those sandstones that have been worked historically (Plate 5), and are still being worked in the district, namely the Elland Flags, Thornhill Rock, Rough Rock, Rough Rock Flags, Midgley Grit and Scotland Flags. These sandstones occur at outcrop across much of the central and south-east of the district. At the time of survey, there were 18 working sandstone quarries in the district (Waters et al., 1996; Cameron et al., 1998) and numerous abandoned quarries. The sandstones are very resistant to attack by acid rain water, although they readily discolour from buff to black when exposed to polluted atmosphere. Subtle differences in colour, texture and natural markings provide a range of attractive building stones suitable for walling, paving and cladding. Coarse-grained sandstones (‘grits’), formerly worked for grindstones, pulpstones and millstones, are now worked for construction fill and occasionally for sand. In general, the sandstones are too weak, porous and susceptible to frost damage for them to be used for good quality roadstone or concrete aggregate. They may be used in road construction below the level of possible frost damage and for some of the less demanding concrete applications. The Elland Flags are used in the manufacture of concrete paving slabs and kerbs.

Peat occurs as a thin veneer across the upland areas of the district. Despite its thinness and limited extent, peat was formerly worked for fuel on a limited scale at Buckstones Moss [SE 00 14] and Slaithwaite Moor [SE 025 140]. The historic extraction of peat has had a detrimental impact on the environment, leaving patches of weathered sandstone that have poor potential for the re-establishment of vegetation. The peat is unsuitable for horticultural purposes.

Mine and quarry waste is present in many parts of the district; it has been little utilised to date. The inert nature of sandstone spoil makes it ideal for bulk-fill, in particular for the construction of road embankments. Colliery spoil, or mine stone, consists of mudstone, siltstone, sandstone, ironstone, waste coal and fireclay. Mine stone can be utilised as fill, although the use is limited and its placement requires control. Detrimental effects to concrete foundations may result from the decomposition of disseminated pyrite to iron sulphate. Waste coal or carbonaceous matter may generate methane and possibly undergo combustion unless precautions are taken to exclude air. Burnt mudstones are more suitable for bulk-fill purposes, as combustion has already removed the carbonaceous material from the spoil.

Ironstone occurs as nodules or thin beds of siderite (iron carbonate) within mudstone, principally in the Coal Measures. The main ironstone worked in the district, the Black Bed or Low Moor Ironstone occurs above the Black Bed Coal, and was formerly worked extensively around Low Moor, Bowling, Wyke and Scholes. The deposits are no longer of economic significance. The Tankersley Ironstone, which lies above the Flockton Thick Coal, was worked around Thornhill, Flockton and Emley.

Surface mineral workings

Former or active quarries or pits that have not been backfilled represent an important resource as they may:

• provide a suitable void for waste disposal
• be reopened as a source of minerals
• be developed as industrial sites
• be developed as local nature reserves for educational, recreational and environmental purposes

Such sites may be a constraint to development as steep rock faces may be unstable. The majority of open excavations are in sandstone, but former fireclay, sand and gravel and brickclay workings are also common. Most sites that are suitable for landfill have already been used, thus adding pressure to utilise any remaining quarries.

Engineering ground conditions

Important considerations relevant to construction and development are:

• suitability of the ground to support structural foundations
• ease of excavation
• use of the ground materials in engineered earthworks and fills

These issues are summarised for the main engineering geological units in the district in (Table 7) and discussed more fully for the Bradford district by Waters et al., (1996b). Foundation conditions are not only affected by the engineering properties of the bedrock and superficial deposits, but also by factors such as the geological structure, slope stability, the presence of undermining and the depth and degree of weathering. Variability of made ground, notably around landfill sites and areas of colliery spoil, may result in differential settlement, particularly in the urban and industrial areas. Colliery spoil may contain iron sulphides (iron pyrites) that are prone to oxidation and dissolution into sulphate-rich, acidic leachates, which may be harmful to concrete present in foundations or buried services. The oxidation process may also result in expansion and differential heaving of foundations constructed upon such deposits. Large volumes of quarry spoil are common in the district, and the areas affected may have poor foundation conditions if large cavities are present or material was deposited on steep slopes.

Subsidence risk due to undermining

The underground mining of coal, fireclay, ironstone and sandstone is no longer carried out in the district. However, mining was formally an important industry, in the area of outcrop of the Coal Measures in the east of the district, including much of urban Huddersfield, Dewsbury, and Bradford. Mining of coal of the Millstone Grit is also recorded at a few localities around Pecket Well, Scammonden, Barkisland and Pole Moor. Sandstone mining was largely limited to working of the Elland Flags, the history of which was reviewed by Godwin (1984). Underground mining of the flags took place around Hipperholme, Northowram, Southowram and Rastrick. Fireclay was worked underground around Ambler Thorne, Park Nook, Sunny Bank, Beacon Hill and Shibden Hall.

In areas of former mining the principal concerns relate to ground instability caused by the collapse of unsupported shallow workings. This may be evident as general ground subsidence or as the development of crown-holes. Structures straddling a fault may be susceptible to uneven settlement in areas prone to mining subsidence. Collapse of shaft fill, linings or cappings may also result in surface subsidence. A review of mining instability in the UK is provided by Arup Geotechnics (1991), which also provides information on the sandstone mining industry of West Yorkshire. Records of shafts and abandoned mines are held by the Coal Authority, who should be consulted prior to development in the former coalfield areas.

Slope stability

Development, particularly for housing, has been forced to extend beyond the prime flat lowland areas of the main valleys onto the steep valley sides. Construction on these steep slopes may encounter stability problems in areas of existing landslide, and where thicker head deposits have accumulated on the lower parts of the slopes (see Chapter 5 Quaternary: Glacial to Postglacial Deposits). In many cases, the landslides in the district developed in response to oversteepening of slopes during the last phases of glaciation, and the majority of the features may be considered currently inactive. However, renewed instability may occur if the slope is adversely disturbed by undercutting or top-loading, or if large volumes of water are introduced, such as may occur due to alteration of drainage patterns during development.

Pollution potential and leachate movement

Artificial (man-made) deposits may contain toxic materials as primary components or as products of chemical or biological reactions; these may migrate within the deposit and into adjacent permeable strata. Waters et al. (1996b) identified a number of industrial land-uses around Bradford which may also be associated with potential pollution in the Huddersfield district. Among the greatest concerns for potential pollution are old landfill sites; these are common within the district, particularly associated with former quarries and disused railway cuttings. Leachates from old sites may present particular problems where tipping was uncontrolled and where little attempt was made to prevent pollutant migration. The problems may more severe where sites occur within areas of faulted bedrock as the faults may provide possible pathways for leachate migration. Areas of former gasworks, chemical works, textile mills, iron and steel works, wire works, railway land and sewage works may all be associated with contamination.

Mine-drainage waters may be a concern in areas of disused coal workings, such as those occurring in the east of the district. Where mine drainage waters reach the surface, their high pH, iron precipitates and commonly elevated levels of manganese, aluminium and sulphate can result in the loss of riverine flora and fauna.

Other environmental problems associated with minewater rebound are outlined by Younger and Robins (2002) and include: pollution of aquifers, build up of ochre deposits in drainage systems, collapse of formerly stable mine workings and the hydraulic forcing of carbon dioxide from mine workings.

Leachate migration occurs where rain water or groundwater percolates through waste and becomes enriched in soluble components including inorganic, organic and microbial components. The resultant leachate may permeate into surface water and groundwater depending on factors such as the permeability of superficial deposits and bedrock adjacent to the site, presence of containment structures and depth of the unsaturated zone. Historically, landfill operations in the UK practised a policy of ‘dilute and disperse’ within uncontained sites. Such a method could potentially lead to reduction of water quality and consequently, newer landfill sites have tended to be engineered containment sites with treatment of leachates. In mining areas, leachate from mine waste tips may be a particular concern for many years after tip emplacement (Gandy and Evans, 2002).

Gas emissions

The main potential gas hazards in the area are associated with the accumulation of methane, carbon dioxide, carbon monoxide, and radon in poorly ventilated enclosed spaces such as basements or foundations. These gases may migrate considerable distances through permeable strata and accumulate within buildings or excavations. Joints, faults or broken ground resulting from subsidence, boreholes or mine workings may act as pathways for such gas migration. Methane is potentially explosive, may act as an asphyxiant and may cause vegetation die back. Carbon dioxide is toxic in high concentrations, may act as an asphyxiant and may cause vegetation die back. Carbon monoxide is potentially explosive and is toxic at low concentrations. Radon is potentially carcinogenic. Hazards associated with radon, methane, carbon dioxide and carbon monoxide are discussed fully by Hooker and Bannon (1993), Appleton (1995), and for the Bradford district by Waters et al. (1996b).

Mine gas may be generated in coal workings or from areas of colliery spoil, throughout the area of Coal Measures outcrop. The main gases present include methane, often referred to as firedamp, carbon dioxide, often occurring as blackdamp (a combination of carbon dioxide and nitrogen), and carbon monoxide.

Artificial (man-made) deposits, in particular landfill sites, may contain organic matter that can biodegrade to form methane and carbon dioxide. Landfill gas characteristics are discussed by Williams and Aitkenhead (1991) and Hooker and Bannon (1993).

Natural gas emissions may develop in response to burial, compaction and heating of marine sediments rich in micro-organisms. Dinantian and Namurian strata present beneath the district may provide a source, as in the case of the Abbeystead disaster caused by the explosion of methane probably derived from Millstone Grit carbonaceous mudstone (Health and Safety Executive, 1985). A number of instances have been recorded early in the 20th century of water boreholes that have intersected strata yielding methane (Wray et al., 1930, p.181), although in some cases a source from mine workings cannot be ruled out. Methane may also be generated in areas of marsh, peatlands, lakes or mill ponds associated with the textile industry.

Radon is a naturally occurring radioactive gas derived from rocks, soils and groundwater containing uranium and thorium. In the district, levels of natural uranium and thorium are generally low, although locally higher concentrations may be associated with marine bands, other carbonaceous mudstones and coal seams in the Millstone Grit and Coal Measures (Ball et al., 1991). Radon may also occur in higher concentrations in high permeability rocks, such as sandstone or sand and gravel deposits, present above a source.

Water resources

Much of the district is drained in a generally easterly direction by the River Calder and its tributaries including the Rivers Colne and Ryburn (Figure 2). North-east of the watershed running from Ovenden Moor through Queensbury and Birkenshaw, drainage is to the north towards the River Aire. The south-east corner of the district around Flockton and Emley drains south-eastward to the River Dearne.

Average annual rainfall is about 700 mm over areas of lower elevation in the east of the district, rising to a maximum of over 1400 mm over the high ground along the western margin of the district in the vicinity of Hebden Bridge. Potential annual evaporation is of the order of 550 mm.

The Millstone Grit and Coal Measures constitute complex multi-layered minor aquifers from which significant quantities of potable groundwater are obtained. Data of current groundwater abstraction, licence and water use for these aquifers are shown in (Table 8). Most of the groundwater abstracted is used for industrial purposes with only small quantities being used for private domestic water supplies. The use of groundwater for agricultural purposes is restricted to the Coal Measures outcrop in the east of the district. Only limited demand exists for supply in the more elevated, sparsely populated, moorlands underlain by the Millstone Grit. Public water supplies have traditionally been obtained from surface water reservoirs located on the high moorlands in the west of the district.

Much larger quantities of groundwater were formerly abstracted from the Millstone Grit than at present. In 1965, a total of almost 3 million cubic metres were abstracted from over 50 sources, predominantly to provide supplies of soft water for spinning and weaving mills and dyeworks. The decline in these industries led to a large reduction in demand for groundwater from the Millstone Grit. The total currently licenced for abstraction from the Coal Measures is similar to that abstracted in the early 1950s. Abstraction fell to 1.6 million cubic metres but rose again in more recent years at least partially due to a need to maintain supplies during periods of shortage or to reduce costs.

The Millstone Grit is a multi-layered aquifer in which the thick, massive grit and sandstone horizons effectively act as separate aquifers with the intervening mudstones acting as aquicludes or aquitards. The more important aquifer horizons include the Kinderscout Grit, the Midgley (or Pule Hill) Grit and the Rough Rock.

Groundwater storage and movement in the well-cemented grits and sandstones is predominantly through joints and fractures, with only minor contributions from the rock matrix. Borehole yields are dependent on the number and size of fractures encountered in a productive horizon. Many boreholes penetrate more than one productive horizon. The groundwater potential of the main water-bearing horizons is very variable, and some horizons may only be of local importance. Variation in yield between boreholes is highly variable even over short distances. Borehole yields from the Millstone Grit generally range from 4 to 72 m3/h, and although low yields are by no means uncommon, dry boreholes are rare. Water level drawdown in response to pumping is only rarely quoted in available records but is highly variable. Under particularly favourable conditions yields may range up to 120 m3/h. Initial yields are not, however, always sustainable, sometimes declining with time as storage is depleted by pumping. Water levels are occasionally artesian, overflowing at surface. The abundant springs in the district are frequently located at boundaries between sandstones or grits and mudstone horizons.

Yields of up to 23 m3/h have been obtained from the Kinderscout Grit in the district (Gray et al., 1969), although yields of between 2.5 and 12.5 m3/h are more common. Many boreholes that penetrate the Kinderscout Grit also penetrated other Millstone Grit aquifer horizons and depths therefore tend to be greater than in other districts. At Clark Bridge Mills, Halifax (Figure 5a) a 500 m borehole penetrating the sequence from the Rough Rock to the Kinderscout Grit, obtained a yield of over 27 m3/h. Although the record gives no indication of the quantities contributed by each of the water-bearing horizons, it is probable that the required yield could not be obtained from the shallower horizons.

The Huddersfield White Rock is a very good aquifer beneath and to the south of Huddersfield (particularly in the Armitage Bridge-Honley area) but yields decline rapidly to the east as the sandstone thins (Wray et al., 1930). Yields of over 17 m3/h have been recorded in the Greetland area. Many boreholes also penetrate either the Rough Rock above, or the Guiseley Grit-Beacon Hill Flags or Midgley Grit-Pule Hill Grit below the Huddersfield White Rock. Of these, bores penetrating the Rough Rock yield up to 15 m3/h, while those penetrating the deeper aquifers yield generally up to 5 m3/h or exceptionally 19 m3/h.

The Rough Rock is arguably the most consistent aquifer horizon in the district. Particularly good yields (40 to 110 m3/h) are obtained to the east of Halifax and in the Bradford area, where boreholes often overflow at surface, having penetrated the confined aquifer horizon (Gray et al., 1969). In the Huddersfield and Holmfirth areas, the Rough Rock generally contains fewer fractures. Consequently, while some boreholes have yielded considerable quantities of soft water others penetrate relatively unfractured rock, are low yielding and require deepening to penetrate the Huddersfield White Rock in order to obtain a satisfactory supply. There is a general trend of decreasing yield with increasing thickness of Coal Measures overburden; yields vary from 23 to 6 m3/h where overburdens are 24 and 170 m, respectively (Gray et al., 1969).

In view of the highly variable nature of the Millstone Grit aquifer and the interrelationship between the number and size of water-bearing fractures and yield, transmissivity is likely to vary considerably even over relatively short distances.

Few comprehensive chemical analyses are available for the Millstone Grit, let alone for specific horizons within the group. Water from the various aquifer horizons within the Millstone Grit has commonly been regarded as very soft. In consequence, these groundwaters were in considerable demand for use in the spinning and weaving mills, and in the numerous dye works associated with the woollen and cloth industry in the area (Wray et al., 1930). Groundwaters of the Millstone Grit generally have hardness ranges from 30 to 250 mg/l, with chloride concentrations generally less than 70 mg/l. Recorded sulphate concentrations are predominantly less than 100 mg/l and invariably less than 150 mg/l. Iron concentrations only rarely exceed 1 mg/l.

The hardness of groundwaters from the Rough Rock varies from about 70 to 170 mg/l, mainly due to carbonate hardness (Gray et al., 1969). Water from a single borehole located at Deighton near Huddersfield [SE 1694 1949] was mineralised to an abnormal degree with a chloride ion concentration of 2300 mg/l, a total dissolved solid content of 4384 mg/l and a total hardness of 355 mg/l (as CaCO₃).

The Coal Measures also form a complex multi-layered minor aquifer. Argillaceous strata predominate, acting as aquitards or aquicludes, isolating the few thick sandstone horizons that effectively act as discrete aquifers. Coal Measures sandstones are generally fine grained, very well cemented, hard and dense and in consequence possess very little intergranular (primary) permeability or porosity. Groundwater storage and movement occurs predominantly within and through fractures and fissures in the sandstones. The lateral extent of sandstone horizons is only rarely greater than 150 km2, commonly thinning to the east of the outcrop area (Gray et al., 1969; Rae, 1978). Although jointing is commonly present in sandstone horizons their interconnection may be poor and sandstones at depth can be dry despite the presence of joints (Holliday, 1986). Rae (1978) considered that the sandstones were generally unlikely to yield significant amounts of water at depths of more than 200 m, due to this effect. The reduction in permeability is compounded by decrease in intergranular porosity and permeability with depth, due to increased cementation, an increased weight of overburden and compaction (Gray et al., 1969).

Sandstone outcrop areas are generally small, limiting the amount of recharge that can infiltrate to individual sandstone units. Extensive faulting splits otherwise continuous sandstone horizons into disconnected isolated fault-bounded blocks, to which no direct recharge can occur. Initial high yields frequently decline substantially due to the depletion of aquifer storage by abstraction, which exceeds the limited quantity of direct or indirect aquifer recharge.

The widespread mining of numerous coal seams has largely disrupted natural hydrogeological conditions of the Coal Measures by the creation of open shafts, roadways and galleries, as well as collapsed, goaf-filled, disused workings and greatly enhanced fracturing of strata due to mining subsidence. These features have created hydraulic continuity between layers that were previously isolated and, in some places, between aquifer horizons and flooded disused workings. This modification of hydrogeological conditions was sufficiently extensive for Banks (1997) to consider the Coal Measures to be ‘an anthropogenically enhanced aquifer’. The early widespread development of coal mining and attendant mine drainage pumping is likely to have made development of groundwater resources in the Coal Measures difficult due to the lowering of water levels, as well as widespread contamination of water quality due to mining and associated industrial activities. In addition large quantities of water were readily available for industrial use from pumped mine drainage. Water supply wells and boreholes are not, therefore, generally numerous.(Table )

In the Bradford area, mainly due to their considerable thickness, the Elland Flags are by far the largest source of groundwater, exceeding the quantities obtained from the Rough Rock and Huddersfield White Rock (Waters et al., 1996). Groundwater has also been abstracted from the Elland Flags at Brighouse where a yield of 127 m3/h was obtained from a borehole of 250 mm diameter. The Clifton and Birstall rocks and many of the other sandstone horizons of the Lower Coal Measures have also been used in the district, as has the Thornhill Rock of the Middle Coal Measures in the east of the district. Boreholes rarely penetrate only one sandstone and it is commonly difficult to identify specific aquifer horizons. Initial good yields, including artesian overflows, commonly decline with time, the decline being related to the quantity of water abstracted (Gray et al., 1969). Considerable yields can sometimes be obtained from boreholes penetrating flooded disused coal workings, although water quality may be poor.

Calculated transmissivity values for bail and pump test data for ten boreholes penetrating the Elland Flags in the Bradford area provided an average value of 204 m²/d (Waters et al., 1996).

Groundwater chemistry data for Coal Measures sources in the district is sparse. Shallow groundwater in the Coal Measures is generally of good quality, but hard and predominantly of calcium bicarbonate type. The limited data available suggest that water chemistry is quite variable, with chloride concentrations ranging from 20 to 120 mg/l. Recorded sulphate concentrations are generally less than 80 mg/l, with iron only rarely exceeding 1 mg/l. An analysis of Coal Measures hydrochemical data from the Huddersfield and Leeds area provided hardness values of between 200 and 500 mg/l (as CaCO3), with chloride and sulphate concentrations of less than 100 and over 100 mg/l, respectively (McGinily, 1993). Groundwater quality may decline with increasing depth down dip, mainly due to increasing chloride concentrations, as is the case in the nearby Leeds district (Marsland, 1975). Groundwater abstracted from disused mine workings may also be of inferior quality, tending to have elevated concentrations of sulphate and iron due to the oxidation and dissolution of pyrite. Coal Measures waters are only occasionally strongly alkaline or ferruginous. Such springs (or spas) existed at Lockwood near Huddersfield and Slaithwaite in the Colne valley and were used in the early 19th century for medicinal purposes, but are long disused (Wray et al., 1930).

Superficial Deposits such as boulder clay in the vicinity of Bradford and alluvial deposits along the valley of the River Colne and its tributaries, are predominantly impermeable. Although sand and gravel deposits do occur within the alluvial deposits, they do not appear to have been used for water supply to any great extent, and cannot be considered to constitute a significant aquifer in the district.

Conservation sites

Many of the sites described in this account may be important for earth science research and teaching and for recreational purposes, and of these many are in disused quarries and pits. There is increasing pressure to use such excavations for landfill, particularly those near to urban centres. Some of the localities have been designated as a Sites of Special Scientific Interest (SSSI) because of their special geological character, including Crimsworth Dean [SD 988 300], Derby Delph Quarry [SE 017 162] and Elland Bypass Cutting [SE 119 202] (English Nature, 1993; Cleal and Thomas, 1995). Additional locations have been recognised by the local authorities and conservation groups as having special geological importance and have been designated as Regionally Important Geological Sites (Table 9).

Information sources

Further geological information held by the British Geological Survey relevant to the Huddersfield District is listed below. It includes published material in the form of maps, memoirs and reports and unpublished material, including maps, reports and other sources of data held by BGS in a number of collections. Searches of indexes to some of the collections can be made on the Geoscience Index System in BGS libraries and on the BGS web site http://www.bgs.ac.uk. At the present time (2005), the datasets are limited and not all are complete. The indexes available are:

• index of boreholes
• topographical backdrop based on 1:250 000 scale maps
• outline of BGS maps at 1:50 000 and 1:10 000 scale and 1:10 560 scale County Series
• chronostratigraphical boundaries and areas from BGS 1:250 000 maps
• geochemical sample locations on land
• aeromagnetic and gravity data recording stations
• land survey records

Maps

Geology maps

• 1:1 500 000
• Tectonic map of Britain, Ireland and adjacent areas, 1996
• 1:625 000
• Solid geology of the United Kingdom (South Sheet), 2001; Quaternary geology, 1977
• 1:250 000
• 53N 04W Liverpool Bay, Solid geology, 1978 53N 02W Humber-Trent, Solid geology, 1983
• 53N 04W Liverpool Bay, Quaternary geology, 1984
• 1:50 000 and 1:63 360
• Sheet 68 Clitheroe (Solid 1960; Drift 1975) Sheet 69 Bradford (Solid; Solid & Drift) 2000 Sheet 70 Leeds (Solid & Drift 2003)
• Sheet 76 Rochdale (Solid 1967; Drift 1974) Sheet 77 Huddersfield (Solid & Drift) 2002 Sheet 78 Wakefield (Solid & Drift) 1998 Sheet 85 Manchester (Solid 1975; Drift 1970) Sheet 86 Glossop (Solid & Drift 1981)
• Sheet 87 Barnsley (Solid & Drift 1976)
• 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 the BGS Library, Keyworth.
• The maps covering the 1:50 000 Series Sheet 77 Huddersfield are listed below (Table 10) together with the surveyor’s initials and the date of survey. The surveyors were: R Addison, I C Burgess, J I Chisholm, R G Crofts, C G Godwin, R D Lake, M T Dean, M S Stewart, A J Wadge, and C N Waters. The maps are not published, but are available for public reference in BGS libraries in Keyworth and Edinburgh, and the London Information Office in the Natural History Museum, South Kensington, London. Uncoloured dyeline copies are available for purchase from BGS Sales Desk; some sheets are available in a digital format. (Figure 19) shows the location of these sheets with respect to the principal local authorities in the district.

Geophysical maps

• 1:1 500 000
• BRITISH GEOLOGICAL SURVEY. 1997. Colour shaded relief gravity anomaly map of Britain, Ireland and adjacent areas. SMITH, I F, and EDWARDS, J W F (compilers). 1:1 500 000 scale (Keyworth, Nottingham, United Kingdom: British Geological Survey.)
• BRITISH GEOLOGICAL SURVEY. 1998. Colour shaded relief magnetic anomaly map of Britain, Ireland and adjacent areas.
• ROYLES, C P, and SMITH, I F (compilers). 1:1 500 000 scale (Keyworth, Nottingham, United Kingdom: British Geological Survey.)
• 1:625 000
• Aeromagnetic map of Great Britain (and Northern Ireland), South Sheet, 1965
• Bouguer anomaly map of the British Isles, Southern Sheet, 1986
• 1:250 000
• Aeromagnetic anomaly, Liverpool Bay, 1978
• Aeromagnetic anomaly, Humber-Trent, 1977
• Bouguer gravity anomaly, Liverpool Bay, 1978
• Bouguer gravity anomaly, Humber-Trent, 1977

Geochemical atlases

• 1:250 000
• Point-source geochemical data processed to generate a smooth continuous surface presented as an atlas of small-scale colour classified digital maps
• Geochemical Survey Programme data are also available in other forms including hard copy and digital data.

Hydrogeological map

• 1:625 000
• Sheet 1 (England and Wales) 1977
• 1:100 000
• Southern Yorkshire and adjoining areas (Sheet 12), 1982
• Groundwater Vulnerability Map, South Pennines (Sheet 11); prepared by the Soil Survey and Land Research Centre and BGS for the Environment Agency.

BGS books and reports

• British regional geology: the Pennines and adjacent areas. Fourth edition. 2002.

Memoirs, Sheet Explanations (SE) and Sheet Descriptions (SD)

• Sheet 69 Bradford and Skipton, 1879* and 1953
• Sheet 69 Bradford (SE and SD), 2000
• Sheet 70 Leeds, 1950*
• Sheet 70 Leeds (SE and SD), 2003.
• Sheet 78 Wakefield (Sheet 78), 1940*
• Sheet 78 Wakefield, 1999
• Sheet 68 Clitheroe and Nelson, 1961*
• Sheet 77 Huddersfield and Halifax, 1930*
• Sheet 85 Manchester and the South East Lancashire coalfield, 1927*
• Sheet 86 Holmfirth and Glossop, 1933*
• Sheet 87 Barnsley, 1947
• Sheet 76 Rossendale Anticline, 1927*

Technical reports

Technical reports relevant to the district are arranged below by topic. Most are not widely available, but may be purchased from BGS or consulted at BGS and other libraries.

• Geology
• (Table 10) shows the reference number for the technical reports covering the geology of individual or combined 1:10 000 scale geological sheets.
• Geology and land-use planning
• Parts of the district are covered by the following BGS Technical Reports and accompanying thematic geological maps dealing with land-use planning and development.
• Geological background for planning and development in the City of Bradford Metropolitan District. British Geological Survey Technical Report, WA/96/1.
• Geology and land-use planning: Morley-Rothwell-Castleford. British Geological Survey Technical Report, WA/88/3.
• Leeds: a geological background for planning and development. British Geological Survey Technical Report, WA/92/1.
• Mineral resources
• Information on mineral resources is available from BGS, Keyworth.
• Engineering geology
• Information on engineering geology is available from BGS, Keyworth.
• Geophysics and Deep Geology
• Kirby et al., (2000) provides information on the structural evolution and geometry of the Craven Basin and adjacent areas, including the Huddersfield district.(Table )
• Biostratigraphy
• Details of internal British Geological Survey biostratigraphical reports are available from BGS, Keyworth.
• Sedimentology
• HALLSWORTH (1994) provides information on heavy minerals and provenance of Millstone Grit and Coal Measures sandstones.
• HALLSWORTH, C R. 1994. Mineralogical evidence for variations in provenance of the Millstone Grit and Lower Coal Measures of the Bradford District. British Geological Survey Technical Report, WH/95/200R.
• Strong, G E has produced three internal reports detailing the petrography of Carboniferous sandstones.

Documentary collections

Boreholes and shafts

Borehole and shaft data for the district are catalogued in the BGS archives (National Geosciences Records Centre) at Keyworth on individual 1:10 000 scale sheets. For the Huddersfield district the collection consists of the sites and logs of about 10 000 boreholes, for which index information has been digitised. Boreholes and shaft sections cited in the text and selected boreholes in and adjacent to the district are listed in (Table 11). For further information contact: The Manager, National Geosciences Records Centre, British Geological Survey, Keyworth, Nottingham NG12 5GG.

Mine plans

BGS maintains a collection of plans of underground mines for minerals other than coal, mostly for sandstone and fireclay.

Geophysics

Gravity and aeromagnetic data are held digitally in the National Gravity Databank and the National Aeromagnetic Databank at BGS Keyworth. Seismic reflection data is available for the south and central parts of the district.

Hydrogeology

Data on water boreholes, wells and springs and aquifer properties are held at BGS, Maclean Building at Wallingford.

BGS Lexicon of named rock unit definitions

Definitions of the named rock units shown on BGS maps, including those shown on the 1:50 000 Series Sheet 77 Huddersfield are held in the Lexicon database. Information on the database can be obtained from the Lexicon Manager at BGS Keyworth. The database can be consulted on the BGS Web site: http://www.bgs.ac.uk.

Material collections

Palaeontological collection

Macrofossils and micropalaeontological samples collected from the district are held at BGS Keyworth. Enquiries concerning all the macrofossil material should be directed to the Curator, Biostratigraphy Collections, BGS Keyworth.

Petrological collections

Hand specimens and thin sections are held in the England and Wales Sliced Rocks collection at BGS Keyworth. A collection database is maintained. Further information, including methods of accessing the database and charges and conditions of access to the collection is available on request from BGS Keyworth.

Borehole core collection

Samples and entire core from a small number of boreholes in the Huddersfield district are held by the National Geosciences Records Centre, BGS, Keyworth.

BGS (Geological Survey) photographs

Copies of photographs used in this report are deposited for reference in the BGS Library, Keyworth. Colour or black and white prints and transparencies can be supplied at a fixed tariff.

Other relevant collections

Coal abandonment plans

Coal abandonment plans are held by The Coal Authority (for address see below).

Groundwater licensed abstractions, Catchment Management Plans and landfill sites

Information on licensed water abstraction sites, for groundwater, springs and reservoirs, Catchment Management Plans with surface water quality maps, details of aquifer protection policy and extent of Washlands and licensed landfill sites are held by the Environment Agency.

Earth science conservation sites

Information on the Sites of Special Scientific Interest present within the Huddersfield district is held by English Nature.

Addresses for data sources

• Mine plans; coal, ironstone and fireclay
• Copies of all known abandonment plans are held by the Mining Records Office, Coal Authority, 200 Lichfield Lane, Berry Hill, Mansfield, NG18 4RG, Telephone 01623 638 233. These plans are held by the Coal Authority in the public domain, but are not available for reference at BGS.
• BGS hydrogeology enquiry service; wells, springs and water borehole records.
• British Geological Survey, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire, OX0 8BB. Telephone 01491 838800. Fax 01491 692345.
• BGS London Information Office at the Natural History Museum Earth Galleries, Exhibition Road, South Kensington,
• London SW7 2DE Telephone 0171 589 4090
• Fax 0171 584 8270
• British Geological Survey (Headquarters) Keyworth, Nottingham NG12 5GG Telephone 0115 936 3100
• Fax 0115 936 3200
• Web Site http://www.bgs.ac.uk

References

Most of the references listed below are held in the Library of the British Geological Survey, Murchison House, Edinburgh, and at Keyworth, Nottingham. Copies of the references can be purchased subject to current copyright legislation. BGS Library catalogue can be searched online at: http://geolib.bgs.ac.uk

AITKENHEAD, N, BRIDGE, D MCC, RILEY, N J, and KIMBELL, S F. 1992. Geology of the country around Garstang. Memoir of the British Geological Survey, Sheet 67 (England and Wales). (London: HMSO.)

AITKENHEAD, N, and RILEY, N J. 1996. Kinderscoutian and Marsdenian successions in the Bradup and Hag Farm boreholes, near Ilkley, West Yorkshire. Proceedings of the Yorkshire Geological Society, Vol. 51, 115-125.

AITKENHEAD, N, BARCLAY, W J, BRANDON, A, CHADWICK, R A, CHISHOLM, J I, COOPER, A H, and JOHNSON, E W. 2002. British regional geology: the Pennines and adjacent areas (Fourth edition). (Keyworth, Nottingham: British Geological Survey.)

APPLETON, J D. 1995. Potentially harmful elements 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.

ARUP GEOTECHNICS. 1991. Review of mining instability in Great Britain. Report to the Department of the Environment, Arup Geotechnics, Ove Arup and Partners. (London: HMSO.)

BALL, T K, CAMERON, D G, COLMAN, T B, and ROBERTS,P D. 1991. Behaviour of radon in the geological environment: a review. Quarterly Journal of Engineering Geology, Vol. 24, 169-182.

BANKS, D. 1997. Hydrogeochemistry of the Millstone Grit and Coal Measures groundwaters, south Yorkshire and north Derbyshire, UK. Quarterly Journal Engineering Geology, Vol. 30, 237-256.

BENFIELD, A C. 1969. The Huddersfield White Rock Cyclothem in the central Pennines. Proceedings of the Yorkshire Geological Society, Vol. 37, 181-187.

BISAT, W S. 1924. Carboniferous goniatites of the north of England and their zones. Proceedings of the Yorkshire Geological Society, Vol. 20, 40-124.

BISAT, W S, and HUDSON, R G S. 1943. The Lower Reticuloceras (R1) goniatite succession in the Namurian of the north of England. Proceedings of the Yorkshire Geological Society, Vol. 24, 383-440.

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Figures, plates and tables(Table )

Figures

(Figure 1) Solid geology of the Huddersfield district.

(Figure 2) Principal physical features of the district.

(Figure 3) Principal early Carboniferous (synextensional) structures of north-west England, map and cross-section (after Kirby et al., 2000). ArF Alport Fault; BaF Barnoldswick Fault; BoL Bowland Line; CAF Clitheroe — Abbeystead Fault System; DeF Dent Fault; DVF Darwen Valley Falt; HBF Heridge — Bradshaw Fault; HeF Heywood Fault; HoF Holme Fault; KeF Kendal Fault; MCF Middle Craven Fault; MoCF Morley — Campsall Fault; NCF North Craven Fault; PeF Pendle Fault System; eL Pennine Line; SCF South Craven Fault; ThF Thorley Fault; WF Winterburn Fault; WhF Whitewell Fault.

(Figure 4) Dinantian platform carbonates of the Holme High. a. Areal e tent and total thickness of platform carbonate over the Holme High (after Evans and Kirby, 1999). b. Cross-section based on seismic reflection profile across the Holme High shows the main unreflective Arundian platform carbonate build-up. More reflective successions are interpreted as basinal facies (courtesy of Enterprise Oil plc) (after Evans and Kirby, 1999).

(Figure 5a) Millstone Grit: correlation of selected boreholes in and adjacent to the Huddersfield district. All sandstones are of northern provenance.

(Figure 5b) Millstone Grit: correlation of selected boreholes in and adjacent to the Huddersfield district. All sandstones are of northern provenance.

(Figure 6) Correlation of boreholes along the line of the Manshead Tunnel (after Waters, 2001).

(Figure 7) Typical sections from the base of Coal Measures to the 80 Yard coal horizon. Marine Bands: AM Amaliae; HL Holbrook; HN Honley; LP Lower Parkhouse; LS Listeri; MF Meadow Farm; SMB Subcrenatum; SP Springwood; UP Upper Parkhouse.

(Figure 8) Typical sections from base of Coal Measures between the 80 Yard and Better Bed coals. Surface sections based on BGS technical reports (Chisholm, 2000a, b). HBJ horizon of Burton Joyce Marine Band; HL horizon of Langley Marine Band; TC Thurlstone channel

(Figure 9) Typical borehole and shaft sections of Coal Measures between the Better Bed and Blocking coals. Seam names within the Beeston group of coals are those applied locally.

(Figure 10) Generalised sections of the Coal Measures between Blocking Coal and top of the exposed succession in the Huddersfield district. Based on map margins for 1:10 000 scale sheets.

(Figure 11) Elland quarries: detailed sections illustrating the succession of sandstone, coal and marine bands (after Wilson and Chisholm, 2002).

(Figure 12) Geology of the Elland quarries, with location of sections shown in ((Figure 11)) (after Wilson and Chisholm, 2002).

(Figure 13) Distribution of principal named sandstones of the Lower Coal Measures with respect to the faults at the surface and the basement (basement faults after Kirby, 2000).

(Figure 14) Glacial and glaciofluvial deposits of the Huddersfield district within the regional setting (after Aitkenhead et al., 2002). Distribution of the deposits is generalised from 1:50 000 scale digital data.

(Figure 15) Superficial deposits and rockhead contours of the Calder valley around Dewsbury.

(Figure 16) Principal early Carboniferous structures of the district and main near-surface faults.

(Figure 17) Main faults affecting the Carboniferous strata of the district.

(Figure 18a) Active mines and pits of the Huddersfield district, 2000.

(Figure 18b) Active sandstone quarries of the Huddersfield district, 2000.

(Figure 19) Location of 1:10 000 scale maps within Sheet 77 Huddersfield.

Plates

(Front cover) View of Halifax from Beacon Hill [SE 4103 4254] (Photograph Caroline Adkin; MN39864).

(Plate 1) Booth Wood Reservoir viewed from the north-west [SE 020 160]. The M62 motorway passes on the southern side of the reservoir below the escarpment of the Midgley Grits (GS 1300)

(Plate 2a) Rough Rock and Rough Rock Flags. Massive coarse-grained sandstone of the Rough Rock over finer grained cross-bedded sandstone of the Rough Rock Flags in old quarries on Crosland Moor, Linthwaite [SE 107 146] (GS 1302).(Table )

(Plate 2b) Rough Rock and Rough Rock Flags. In the road cut at Elland [SE 102 215], the base of the Rough Rock lies at the base of the paler coloured massive beds roughly one third from the top of the section (GS 1301).

(Plate 3) Elland Edge [SE 120 125] is capped by the Elland Flags (Lower Coal Measures). An old brickpit at the foot of the slope shows a section of grey mudstone from just above the 36 Yard Coal up to the base of the 80 Yard Rock (three pale layers at the top of the face) (GS1253).

(Plate 4a) Landslide. Pike End, Rishworth [SE 028 174] (GS 1303).(Table )

(Plate 4b) March Hill, west of b March Haigh Reservoir, viewed from the north-west [SE 008 132] (GS 1304).

(Plate 5) Shaw’s quarry (1926), Crosland Hill. Rough Rock freestone used for building locally and elsewhere. View looking east [SE 1176 1478] (A3600).

(Back cover)

Tables

(Table 1) Geological succession of the district.

(Table 2) Marine bands of the upper parts of the Namurian of Western Europe (after Riley et al., 1995).

(Table 3) Classification of Westphalian strata in the Pennine Basin, based on Ramsbottom et al. (1978) and Powell et al. (2000). Units known to be present (in whole or in part) in the Huddersfield district are shown in bold.

(Table 4) Former use and thickness of named coal seams and thickness of inter-seam strata.

(Table 5) Principal named faults in the district with an indication of the approximate maximum downthrow at surface.

(Table 6) Typical chemical analysis of the Hard Bed fireclay.

(Table 7) Engineering geological characteristics of the rocks and soils in the district.

(Table 8) Licenced abstraction data for the Huddersfield district, 2000 (derived from data provided by the Environment Agency, North East Region).

(Table 9) Regionally important geological sites.

(Table 10) Component 1:10 000 scale maps, technical reports, and survey details of Sheet 77 Huddersfield.

(Table 11) Boreholes and shaft sections cited in the text and selected boreholes in and adjacent to the district are listed alphabetically, together with their National Grid Reference, BGS registered number (1:10 000 scale quarter-sheet number) and total depth.

Tables

(Table 1) Geological succession of the district

(Table 2) Marine bands of the upper parts of the Namurian of Western Europe (after Riley et al., 1995)

(Table 4) Former use and thickness of named coal seams and thickness of inter-seam strata

(Table 5) Principal named faults in the district with an indication of the approximate maximum downthrow at surface

(Table 6) Typical chemical analysis of the Hard Bed fireclay

(Table 8) Licenced abstraction data for the Huddersfield district, 2000 (derived from data provided by the Environment Agency, North East Region)

(Table 9) Regionally important geological sites

(Table 10) Component 1:10 000 scale maps, technical reports, and survey details of Sheet 77 Huddersfield

(Table 11) Boreholes and shaft sections cited in the text and selected boreholes in and adjacent to the district are listed alphabetically, together with their National Grid Reference, BGS registered number (1:10 000 scale quarter-sheet number) and total depth