Geology of the Greywell Area, Basingstoke, Hampshire
Total Page:16
File Type:pdf, Size:1020Kb
Geology of the Greywell area, Basingstoke, Hampshire. Geology and Landscape Programme Commissioned Report CR/12/104. BRITISH GEOLOGICAL SURVEY GEOLOGY AND LANDSCAPE PROGRAMME COMMISSIONED REPORT CR/12/104. Geology of the Greywell area, Basingstoke, Hampshire. A R Farrant The National Grid and other Ordnance Survey data © Crown Copyright and database rights 2012. Ordnance Survey Licence No. 100021290. Keywords Report; Chalk, Basingstoke, Palaeogene. National Grid Reference SW corner 471000 151000 Centre point 472300 1514000 NE corner 474000 152000 Map Sheet 284, Basingstoke Bibliographical reference FARRANT, A R 2012. Geology of the Greywell area, Basingstoke, Hampshire. British Geological Survey Commissioned Report, CR/12/104. 15pp. 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 [email protected]. You may quote extracts of a reasonable length without prior permission, provided a full acknowledgement is given of the source of the extract. Maps and diagrams in this book use topography based on Ordnance Survey mapping. © NERC 2012. All rights reserved Keyworth, Nottingham British Geological Survey 2012 BRITISH GEOLOGICAL SURVEY The full range of our publications is available from BGS shops at British Geological Survey offices Nottingham, Edinburgh, London and Cardiff (Welsh publications only) see contact details below or shop online at www.geologyshop.com BGS Central Enquiries Desk Tel 0115 936 3143 Fax 0115 936 3276 The London Information Office also maintains a reference collection of BGS publications, including maps, for consultation. email [email protected] We publish an annual catalogue of our maps and other publications; this catalogue is available online or from any of the Environmental Science Centre, Keyworth, Nottingham BGS shops. NG12 5GG Tel 0115 936 3241 Fax 0115 936 3488 The British Geological Survey carries out the geological survey of email [email protected] Great Britain and Northern Ireland (the latter as an agency service for the government of Northern Ireland), and of the surrounding continental shelf, as well as basic research projects. Murchison House, West Mains Road, Edinburgh EH9 3LA It also undertakes programmes of technical aid in geology in Tel 0131 667 1000 Fax 0131 668 2683 developing countries. email [email protected] The British Geological Survey is a component body of the Natural Environment Research Council. Natural History Museum, Cromwell Road, London SW7 5BD Tel 020 7589 4090 Fax 020 7584 8270 Tel 020 7942 5344/45 email [email protected] Columbus House, Greenmeadow Springs, Tongwynlais, Cardiff CF15 7NE Tel 029 2052 1962 Fax 029 2052 1963 Maclean Building, Crowmarsh Gifford, Wallingford OX10 8BB Tel 01491 838800 Fax 01491 692345 Geological Survey of Northern Ireland, Colby House, Stranmillis Court, Belfast BT9 5BF Tel 028 9038 8462 Fax 028 9038 8461 www.bgs.ac.uk/gsni/ Parent Body Natural Environment Research Council, Polaris House, North Star Avenue, Swindon SN2 1EU Tel 01793 411500 Fax 01793 411501 www.nerc.ac.uk Website www.bgs.ac.uk Shop online at www.geologyshop.com CR/12/104; Final Last modified: 2012/10/19 13:22 Contents Contents ........................................................................................................................................... i 1 Introduction ............................................................................................................................ 1 2 Bedrock Geology .................................................................................................................... 3 2.1 Seaford Chalk Formation ................................................................................................ 4 2.2 Newhaven Chalk Formation ........................................................................................... 4 2.3 Lambeth Group ............................................................................................................... 5 2.4 Thames Group ................................................................................................................ 5 3 Superficial Geology ................................................................................................................ 6 3.1 Alluvial deposits ............................................................................................................. 6 3.2 Clay-with-flints ............................................................................................................... 6 3.3 Head ................................................................................................................................ 6 4 Geological Structure .............................................................................................................. 7 5 Conclusions ............................................................................................................................. 8 References ...................................................................................................................................... 8 FIGURES Figure 1. Existing 1:50 000 scale bedrock geological map for the Greywell area based on the 1897 six-inch survey. Base map ©Ordnance Survey; Licence No. 100021290. ..................... 2 Figure 2. Existing 1:50 000 scale bedrock and superficial geological map for the Greywell area. Base map ©Ordnance Survey; Licence No. 100021290. ......................................................... 2 Figure 3. Revised geological line-work for the Greywell area superimposed on the OS 1:25 000 map. Base map ©Ordnance Survey; Licence No. 100021290. ................................................ 3 Figure 4. Summary of evolving stratigraphic nomenclature of the Chalk Group in England (Hopson, 2005). ........................................................................................................................ 4 Figure 5. Revised geological map of the Greywell-Odiham area. Base map ©Ordnance Survey; Licence No. 100021290. ........................................................................................................... 9 Figure 6. Revised geological map of the Greywell-Odiham area (as per Figure 5) superimposed on the published geological map. Base map ©Ordnance Survey; Licence No. 100021290. 10 i 1 Introduction This report gives a brief account of the geology of the Greywell area near Basingstoke, Hampshire. The Greywell area lies approximately 8 km east-south-east of Basingstoke, and is located on the 1:50 000 scale geological map sheet 284 (Basingstoke). The area was last completely mapped during the six-inch survey of the Basingstoke district, which was published in 1897 (Figures 1 and 2). A partial revision of the Chalk outcrop was undertaken in 2007 by K A Booth, but did not include the Palaeogene outcrop. The published geological map is based on the 1897 six-inch survey of the Basingstoke district (Figures 1 and 2). Consequently the map does not show the new Chalk lithostratigraphy, nor is the bedrock related to modern topographical contours. Thus there is considerable uncertainty in the location of the Chalk- Palaeogene contact in the Greywell area. As part of a groundwater modelling investigation in the Whitewater River catchment, focussed on the Greywell pumping station, BGS was asked by the client (Jacobs Engineering) to undertake a partial revision of the Basingstoke geological map sheet around the Whitewater valley. The present survey was commissioned to obtain additional field data and combine that with borehole records and topographic data to provide a more accurate indication of the Chalk– Palaeogene boundary. The area between Up Nately, Greywell, North Warnborough and Odiham was resurveyed in mid September 2012 by A R Farrant, in particular focussing on the Chalk– Palaeogene boundary, including a zone up to 0.5 km either side of the contact. Superficial deposits were also mapped, but no additional boreholes or sections were excavated or logged. Existing BGS records including old field-slips, borehole records and historic maps, along with information on the Greywell Canal Tunnel from the Surrey & Hampshire Canal Society (see http://www.basingstoke-canal.org.uk/engineering/tunnels.htm) were also used in the compilation of the new line work. Fieldwork was undertaken by a standard walkover survey with a soil auger. The new line-work is shown in Figures 3, and also in Figures 5 and 6 at the end of the report. 1 London Clay Fm Reading Fm Upper Chalk Figure 1. Existing 1:50 000 scale bedrock geological map for the Greywell area based on the 1897 six-inch survey. Base map ©Ordnance Survey; Licence No. 100021290. River Terrace deposits Alluvium Clay-with- flints Figure 2. Existing 1:50 000 scale bedrock and superficial geological map for the Greywell area. Base map ©Ordnance Survey; Licence No. 100021290. 2 Figure 3. Revised geological line-work for the Greywell area superimposed on the OS 1:25 000 map. Base map ©Ordnance Survey; Licence No. 100021290. 2 Bedrock Geology The bedrock geology of the Greywell area can be conveniently subdivided into three main units; the Late Cretaceous Chalk Group and the overlying Palaeogene Lambeth and Thames groups. The Chalk in the Basingstoke area can be subdivided into nine formations (Hopson, 2005; Aldiss et al., 2012),