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Structure and evolution of the East Midlands region of the Pennine Basin : subsurface memoir

Pharaoh, T.C.; Vincent, C.J.; Bentham, M.S.; Hulbert, A.G.; Waters, C.N.; Smith, N.J.P.. 2011 Structure and evolution of the East Midlands region of the Pennine Basin : subsurface memoir. Nottingham, UK, British Geological Survey, 144pp.

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Abstract/Summary

sedimentary history of the eastern part of the English Midlands (hereafter referred to as the region) emphasising the structure and evolution of the Carboniferous basins. It is the fourth in the Subsurface Memoir series of the British Geological Survey, following the Northumberland– Solway Basin (Chadwick et al., 1995), the Craven Basin (Kirby et al., 2000) and south-west Pennine Basin (Smith et al., 2005), and forms a sequel to a previously published subsurface study of the Mesozoic basins of England and Wales (British Geological Survey, 1985a). The region includes areas of high urban population density, contrasting with pastoral countryside and fenland (Figure 1). The cities of Nottingham, Leicester, Lincoln and Peterborough are the principal conurbations, but much of north Nottinghamshire and South Yorkshire bear the legacy of industrialisation following development of the concealed Yorkshire–Nottinghamshire coalfield. The geology of the region (Figure 2) is superficially simple. Carboniferous strata of the southeastern part of the Pennine Basin dip eastward beneath a cover of Permian and Mesozoic strata. This description belies the complex structure and stratigraphy of the Carboniferous basins however; rapid stratigraphical variation occurs where the Carboniferous strata onlap onto the Anglo–Brabant Massif in the south of the region. Early Palaeozoic strata have very limited outcrop, and are mainly known from deep boreholes. Deformation of the rocks occurred during a number of tectonic episodes, producing structures that control their nature and distribution. The surface and near-surface geology have been described in the British Geological Survey 1:50 000 Series maps and memoirs (Appendix 1). This account examines the deeper parts of the Permian– Mesozoic and, in particular, the Carboniferous successions, in greater detail than in earlier publications. Over 2000 seismic reflection profiles have been interpreted, and some 500 deep boreholes studied during the course of this work, and the results are synthesised in the accompanying 1:625 000 scale structure contour and isopach maps (Appendix 3) and associated text figures. This account provides both a regional review and an explanation of these maps and figures. The Carboniferous rocks of the region have long been of economic significance. Coal has been worked for centuries. Prior to the 1960s, only limited investigation of the concealed geology was possible, mainly through coal exploration and extraction, and oil exploration. The National Coal Board (NCB) established a sophisticated system for coal seam identification and correlation using geochemical methods. This was combined with biostratigraphical information from marine bands to yield a very detailed lithostratigraphical correlation of the Coal Measures. The region has experienced several phases of hydrocarbon exploration: immediately following the First World War; just before and after the Second World War, when drilling was mainly on the edges of structural highs recognised from gravity anomalies; in the 1950s and 1960s, with the widespread application of seismic techniques; in the 1970s and 1980s, using 2D reflection seismic data of increasingly high fold; and since 1995, using 3D reflection seismic. The 2D data are variable in fold of stack (12 to 60) and data quality (poor to good). The acquisition of the hydrocarbon exploration seismic data, in combination with Coal Authority high resolution seismic data over more localised areas, has resulted in an extensive network of seismic reflection profiles (Figure 3), except across the Anglo–Brabant Massif (Figure 4) and in the main conurbations. This account relies heavily on these data. The 3D data are now becoming available through release, but were not extensively used during the mapping programme. A few examples of these data are however included as figures. All phases of exploration have involved the drilling of deep boreholes which, together with surface exposures, provide stratigraphical calibration. Depth conversion of interpreted seismic data to produce the structural maps was complicated by a number of factors, including the variable age of the data and the quantity and quality of the data. Horizons mapped from the seismic data in two-way-travel-time (TWTT) were converted to depth using velocity functions based on depths and times in key boreholes. Particular attention was paid to the depth conversion of the early Carboniferous interval, due to the known variation of Tournaisian and Visean lithologies (and thus interval velocities) at crop and in boreholes in surrounding basins (i.e. platform carbonates and basinal mudstone facies)

Item Type: Publication - Book
Programmes: BGS Programmes 2010 > Geology and Landscape (England)
ISBN: 9780852726716
Additional Information. Not used in RCUK Gateway to Research.: Available from the BGS Sales Desk Tel: 0115 936 3241 Fax: 0115 936 3488 email sales@bgs.ac.uk http://www.geologyshop.com
Date made live: 20 Jun 2011 14:00
URI: http://nora.nerc.ac.uk/id/eprint/14487

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