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Geology of the Newbury district and part of the Abingdon district : sheet description for the British Geological Survey 1:50 000 Series Sheet 267 and part of Sheet 253 (England and Wales)

By Don Aldiss, Andrew Newell, Richard Marks, Peter Hopson, Andrew Farrant, Katherine Royse, John Aspden, David Evans, Nigel Smith, Mark Woods and Ian Wilkinson

Abstract

This report describes the geology of the Newbury district and the southern part of the Abingdon district, including most of the Berkshire Downs and adjacent portions of the valleys of the River Kennet and its tributaries. Together with a printed geological map of the Newbury district at 1:50 000 scale, it was produced as part of the BGS Regional Mapping Programme. A geological map at 1:50 000 scale covering the catchments of the River Pang and the River Lambourn, together with adjacent portions of the Chalk escarpment to the north, is also available from BGS as a print-on-demand product. This was produced as part of the infrastructural information provided for the LOCAR (Lowland Catchment Research) Project, under the NERC Thematic Programme.\ud The introduction describes the topographical and geological setting of the area. Subsequent chapters describe the bedrock (or ‘solid’) geology, the superficial (or ‘drift’) geology and the geological structure. They are followed by a section on Applied Geology. The final section, Information Sources, lists all the BGS publications relevant to the district and gives information on how to gain access to BGS collections and databases, including borehole records and geophysical, geochemical and geotechnical data.\ud Most of the area is underlain by the Upper Cretaceous Chalk Group, which forms the downlands (Cover picture). The Lower Cretaceous Upper Greensand and Gault, and a small area of the Jurassic Kimmeridge Clay, occur in the north. The Upper Greensand Formation also appears from beneath the Chalk to form inliers in the south-west of the district, in the core of anticlinal folds aligned with the Vale of Pewsey. At depth, the area is partly underlain by a thin discontinuous Lower Greensand sequence, attenuated Jurassic and Triassic successions, Westphalian-aged deposits of the Berkshire Coal Basin, and thin Tournaisian/Visean and thick Devonian strata resting on Lower Palaeozoic basement.\ud Overlying the Chalk, the southern part of the district includes the western end of the Palaeogene (Tertiary) outcrops of the synclinal London Basin. The Palaeogene succession extends from the Lambeth Group (mostly made up of clays and sands of the Reading Formation, with a thin basal Upnor Formation) up into the London Clay Formation (Thames Group), which in this district includes relatively thick beds of sand and some pebble gravels within the usual clays.\ud The bedrock formations are commonly obscured by superficial deposits of Quaternary age. These include river terrace deposits at nine identified levels (including the ‘plateau gravels’ of previous terminology); alluvial deposits, peat and tufa forming the modern river flood plains; clay-with-flints and sand forming a residual cover over the higher parts of the downs; and head (solifluction deposits) on slopes and valley floors in most parts of the district. Areas of worked ground, made ground, infilled ground and landscaped ground have also been delineated.\ud Landslides occur locally on the Palaeogene formations around Newbury. Other potential geological hazards in the area include cambering and valley bulge, ground heave, subsidence, flooding and radon emission. The possibility of risk from these factors should be taken into consideration in any construction or land development project.\ud The most important natural mineral resources in the area are water and aggregates (sand and gravel). In the past, clay, chalk, flint and peat were exploited on a small scale.\ud Figures and plates appear at the end of the report

Publisher: British Geological Survey
Year: 2010
OAI identifier: oai:nora.nerc.ac.uk:16117
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