The stratigraphical framework for the Palaeogene successions of the London Basin, UK Open Report OR/12/004 BRITISH GEOLOGICAL SURVEY OPEN REPORT OR/12/004 The National Grid and other Ordnance Survey data are used The stratigraphical framework for with the permission of the Controller of Her Majesty’s Stationery Office. the Palaeogene successions of the Licence No: 100017897/2012. London Basin, UK Key words Stratigraphy; Palaeogene; southern England; London Basin; Montrose Group; Lambeth Group; Thames Group; D T Aldiss Bracklesham Group. Front cover Borehole core from Borehole 404T, Jubilee Line Extension, showing pedogenically altered clays of the Lower Mottled Clay of the Reading Formation and glauconitic sands of the Upnor Formation. The white bands are calcrete, which form hard bands in this part of the Lambeth Group (Section 3.2.2.2 of this report) BGS image P581688 Bibliographical reference ALDISS, D T. 2012. The stratigraphical framework for the Palaeogene successions of the London Basin, UK. British Geological Survey Open Report, OR/12/004. 94pp. 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. 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This framework report provides detailed descriptions for units occurring in the onshore area of the London Basin and adjacent parts of East Anglia. Existing names are used wherever appropriate, although where unit names have not previously existed or are unsatisfactory, the report proposes revisions. Acknowledgements The author would like to thank current and former BGS colleagues for helpful discussion and suggestions, in particular R A Ellison, D C Entwisle, P M Hopson, C N Waters and I T Williamson, who advised on parts of this document and who created many of the Lexicon entries on which it draws. Outside BGS, Dr Jackie Skipper, Dr Chris King, D P Page and T Newman are thanked for helpful comments and discussions, and for the provision of documentation, some unpublished. The report was reviewed within BGS by David Entwisle and Richard Ellison, who contributed significantly to its accuracy. The author has benefited from the sight of various unpublished documents, including an incomplete draft description of the Upper Palaeogene of the London Basin, dated 1998, by Richard Ellison, Ian Williamson and Chris King; a provisional stratigraphical framework for the Palaeogene and Neogene rocks of the onshore areas of the Hampshire Basin, the London Basin and East Anglia, dated July 2003, by Robert Knox and Chris King; and advanced drafts of parts of a Geological Society of London (GSL) Special Report on the stratigraphy of the British Palaeogene and Neogene by Chris King. Many details have been drawn from the latter report, especially of inferred environment and age of deposition. However, sections of the latest draft of the GSL Report was received on 30 August 2011, just as work on this BGS report was drawing to a close. This late draft of the GSL Report was subject to review and so liable to be altered further before publication. The present BGS report therefore does not take full account of this latest version of the GSL Report, especially in respect of the proposed formal naming of subdivisions in the Woolwich and Reading formations. Production of this report was funded by the Standards and Best Practice Project (formerly the Geoscientific Standards and Nomenclature Project). This report has been compiled on behalf of the BGS Stratigraphy Committee, and reflects a degree of pragmatism and compromise. It is believed to provide a workable scheme within which any new data and subdivision can be accommodated. If users of this document discover inconsistencies or factual errors in the specifications given for the various lithostratigraphical units, they are encouraged to notify The Chairman, BGS Stratigraphy Committee, British Geological Survey, Keyworth, Nottingham, NG12 5GG (email [email protected]). i OR/12/004; Version 1.0 Last modified: 2012/03/08 12:58 Contents Foreword ......................................................................................................................................... i Acknowledgements ......................................................................................................................... i Contents .......................................................................................................................................... ii 1 Introduction ............................................................................................................................ 1 1.1 Scope of the report .......................................................................................................... 1 1.2 Comparison with the Geological Society of London Special Report on the Tertiary .... 1 1.3 Palaeogeography and depositional basins ...................................................................... 2 1.4 Stratigraphical frameworks ............................................................................................. 3 1.4.1 Chronostratigraphy ...................................................................................................... 4 1.4.2 Biostratigraphy ............................................................................................................ 4 1.4.3 Magnetostratigraphy .................................................................................................... 4 1.4.4 Stable-isotope stratigraphy .......................................................................................... 4 1.4.5 Radiometric dating ...................................................................................................... 5 1.4.6 Tephrostratigraphy ...................................................................................................... 5 1.4.7 Cyclic stratigraphy ...................................................................................................... 5 1.4.8 Sequence stratigraphy ................................................................................................. 5 1.5 The BGS Lexicon of Named Rock Units ....................................................................... 5 1.6 Conventions .................................................................................................................... 6 2 An introduction to the Palaeogene Groups of southern England and some terminological conventions ........................................................................................................... 7 2.1 Palaeogene Groups in southern England ........................................................................ 7 2.2 ‘Lower London Tertiaries’ ............................................................................................