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A contribution to the Sheet Explanation of the Ipswich district (Sheet 207):

Integrated Geosurveys (Southern ) Programme Internal Report IR/05/007

BRITISH GEOLOGICAL SURVEY

INTEGRATED GEOSURVEYS () PROGRAMME INTERNAL REPORT IR/05/007

A contribution to the Sheet Explanation of the Ipswich district (Sheet 207): Cretaceous

M A Woods

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 Licence No:100017897/2004.

Keywords

Cretaceous, Formation, , , Biostratigraphy, Chronostratigraphy.

Bibliographical reference

WOODS, M A. 2004. A contribution to the Sheet Eplanation of the Ipswich district (Sheet 207): Cretaceous. British Geological Survey Internal Report, IR/05/007. 10pp.

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. © NERC 2004. All rights reserved Keyworth, Nottingham British Geological Survey 2004 BRITISH GEOLOGICAL SURVEY The full range of Survey publications is available from the BGS British Geological Survey offices Sales Desks at Nottingham, Edinburgh and London; see contact details below or shop online at www.geologyshop.com Keyworth, Nottingham NG12 5GG The London Information Office also maintains a reference ? 0115-936 3241 Fax 0115-936 3488 collection of BGS publications including maps for consultation. e-mail: [email protected] The Survey publishes an annual catalogue of its maps and other www.bgs.ac.uk publications; this catalogue is available from any of the BGS Sales Shop online at: www.geologyshop.com Desks. The British Geological Survey carries out the geological survey of Murchison House, West Mains Road, Edinburgh EH9 3LA Great Britain and (the latter as an agency ? 0131-667 1000 Fax 0131-668 2683 service for the government of Northern Ireland), and of the e-mail: [email protected] surrounding continental shelf, as well as its basic research projects. It also undertakes programmes of British technical aid in geology in developing countries as arranged by the Department London Information Office at the Natural History Museum for International Development and other agencies. (Earth Galleries), Exhibition Road, South Kensington, London SW7 2DE The British Geological Survey is a component body of the Natural Environment Research Council. ? 020-7589 4090 Fax 020-7584 8270 ? 020-7942 5344/45 email: [email protected]

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Foreword

This report constitutes a contribution to the Sheet Explanation of the Ipswich district (Sheet 207).

Acknowledgements

Anglian Water and A F Howland Associates generously provided site investigation data on the Chalk of the Ipswich district. C J Wood and T. Wright provided data and advice on the biostratigraphical and lithostratigraphical classification of the Chalk of the Ipswich district.

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Contents

Foreword...... i

Acknowledgements...... i

Contents...... ii

Summary ...... iii

1 Cretaceous...... 1

References ...... 3

FIGURES

FIGURE 1. The exposed and probable concealed Chalk Group stratigraphy of the Ipswich district. FIGURE 2. The stratigraphical ranges of key Chalk Group outcrops in the Ipswich district (not to scale).

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Summary

This report describes the Cretaceous stratigraphy of the Ipswich district (Sheet 207), and forms a contribution to the Sheet Explanation of Sheet 207.

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1 Cretaceous

For much of the the Ipswich district formed part of the Anglo-Brabant Landmass, covering large parts of East Anglia, the London area and extending eastwards into continental . The oldest Mesozoic strata in the Ipswich district are the mudstones of the Gault Formation, which represent the flooding of this landmass by a marine transgression at the end of the Lower . The Gault does not crop out in the Ipswich district, but occurs at depth in a borehole at Combs [TM 0427 5625], where 3.35 m were proved. Deeper boreholes at Harwich [TM 260 329] and Weeley [TM 148 218], in the adjacent Colchester district, show 6.7 m and c. 23 m of Gault respectively above Palaeozoic strata. In the Upper Cretaceous, large rises in sea level allowed marine deposition to extend across nearly the whole of the UK, represented by the deposits of the Chalk Group. The group underlies the whole of the Ipswich district, but only crops out in the flanks of the Gipping Valley north of Bramford, in the small tributary valley between Needham Lake and Coddenham, and in two small areas near Offton and Somersham. Across much of the district the Chalk is concealed by Palaeogene and Quaternary deposits, but data from boreholes and sporadic outcrops permit investigation of its stratigraphy. At least 250 m of Chalk were proved in the Combs Borehole, and to this can perhaps be added a further 45 m based on outcrops in the Gipping Valley and site investigation boreholes beneath Ipswich town (Figure 1). Chalk is typically a very fine-grained, white , predominantly composed of the disaggregated skeletal remains () of tiny planktonic algae that flourished in the seas of the Upper Cretaceous. The Chalk Group is composed of almost pure in the form of low magnesian calcite, except the lower part, which contains up to 30% clay. , clay-rich horizons (marls), beds of indurated, mineralised chalk (hardgrounds), and coarsely bioclastic chalk horizons also occur, and some of these are geographically extensive marker- horizons and have been recognised on the resistivity log of the Stowlangtoft Borehole [TL 9475 6882] in the adjacent Bury St. Edmunds district (Bristow, 1990; Figure 1). Traditionally, a tripartite classification has been applied to the Chalk Group (Lower, Middle and Upper Chalk), based on the development of feature-forming beds of hard chalk. In southern England this classification is now superseded by that of Rawson, Allen & Gale (2001), which recognises two subgroups and up to nine formations within the Chalk Group. East Anglia belongs to the so-called 'Transitional Province', recognising that the Chalk of this region shows features that are intermediate between the distinct Chalk Group stratigraphies of southern and northern England (Mortimore, Wood & Gallois, 2001; Rawson et al., 2001). The extent to which southern England Chalk Group nomenclature can be applied to East Anglia is still unclear. In the Ipswich district, it seems likely that the stratigraphy of the concealed succession and some of the exposed succession is analagous to southern England. However, there are lithostratigraphical differences in part of the exposed succession that warrant a modified nomenclature (Figure 1; see below). The probable stratigraphy of the unexposed part of the Chalk Group can largely be determined from the BGS Stowlangtoft Borehole. This borehole is about 12 km NNW of the north-west corner of Sheet 207, and many features of its core and resistivity log can be compared with logs from boreholes in southern England. On this basis, it seems likely that the Ipswich district is underlain by representatives of the following formations (in ascending stratigraphical order): West Melbury Marly Chalk, Zig Zag Chalk, Holywell Nodular Chalk, New Pit Chalk, Lewes Nodular Chalk and Seaford Chalk (Figure 1).

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Outcrops in the Gipping Valley show that the exposed part of the Chalk Group can be divided into two formations, the Newhaven Chalk overlain by the Culver Chalk. The Newhaven Chalk forms the bulk of the outcrop succession (Figure 2), and mainly consists of very poorly flinty chalk, lacking conspicuous marl seams. Macrofossils are generally rare, except for occasional specimens of the belemnite Gonioteuthis, and an oyster-rich bed with abundant Pseudoperna boucheroni (Woods non Coquand, 1859) and inoceramid shell fragments (Platyceramus and Sphenoceramus) seen near the bases of the successions at Needham Quarry [TM 0940 5395] and in one of the two pits at Little Blakenham [TM 1086 4910]. Outcrops in the Gipping Valley mainly belong to the O. pilula and basal G. quadrata zones (Figure 2) (Wilkinson, 2004), but in Ipswich, site investigation boreholes proved up to 55 m of the formation, including the U. socialis and M. testudinarius zones. Because the Newhaven Chalk of the Ipswich district appears so distinct from the typical flinty and marl-bearing Newhaven Chalk of southern England, it is herein named the Blakenham Member, with its stratotype section in the large quarry at Great Blakenham [TM 1161 4986]. The member is similar to the Margate Member of Robinson (1986), but much less flinty, and future work in East Anglia might justify designation of formational status. The Culver Chalk forms the top of the succession at Claydon Quarry [TM 1363 4966] and in many of the Ipswich town site investigation boreholes. The formation contains regularly developed medium and large nodular flints with moderately common remains of the echinoid Echinocorys. In the Ipswich boreholes, the formation is associated with the belemnite Belemnitella, also recorded in historical accounts of outcrops at Coe's Pit, Bramford [TM 12917 48141] and Claydon [TM 1319 4943] (Boswell, 1927). The locally abundant record of Belemnitella was the basis for the historical identification of B. mucronata Zone chalk in the Ipswich district (Boswell, 1927), but new biostratigraphical data shows that these occurrences of Belemnitella are within the lower part of the G. quadrata Zone, and are most probably correlative with the local abundance of this belemnite at the base of the Culver Chalk Formation in southern England (e.g. Bailey, Gale, Mortimore, Swiecicki & Wood, 1983, fig. 3; Mortimore, 1986, fig. 20).

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References

Most of the references listed below are held in the Library of the British Geological Survey at Keyworth, Nottingham. Copies of the references may be purchased from the Library subject to the current copyright legislation.

BAILEY, H W, GALE, A S, MORTIMORE, R N, SWIECICKI, A & WOOD, C J. 1983. The - stages of the United Kingdom, with particular reference to southern England. Newsletters on Stratigraphy, 12, 29-42. BRISTOW, C. R. 1990. Geology of the country around Bury St Edmunds. Memoir of the British Geological Survey, England & Wales (Sheet 189). BOSWELL, P G H. 1927. The Geology of the country around Ipswich. Memoirs of the Geological Survey. Sheet 207 (England & Wales). MORTIMORE, R N. 1986. Stratigraphy of the Upper Cretaceous White Chalk of Sussex. Proceedings of the Geologists' Association, 97, 97-139. MORTIMORE, R N, WOOD, C J & GALLOIS, R W. 2001. British Upper Cretaceous Stratigraphy, Geological Conservation Review Series, No. 23, Joint Nature Conservation Committee, Peterborough. RAWSON, P F, ALLEN, P & GALE, A S. 2001. The Chalk Group - a revised lithostratigraphy. Geoscientist, 11, 21. ROBINSON, N D. 1986. Lithostratigraphy of the Chalk Group of the , southeast England. Proceedings of the Geologists' Association, 97, 141-170. WILKINSON, I P. 2000. A preliminary foraminiferal biozonation of the Chalk Group (In preparation for the Holostrat Project: Upper Cretaceous). British Geological Survey Internal Report, IR/00/13, 21pp.

WILKINSON, I P. 2004. from the Chalk of the Gipping Valley, Ipswich. British Geological Survey Internal Report, IR/04/077.

3 FIGURE 1 150 200 250 100 50 0

Thickness (m)

Grey Chalk White Chalk Subgroup . Traditional

(*: noprecise correlationwiththeS 'Lower Chalk' 'Middle Chalk' 'Upper Chalk' Subdivisions The exposedandprobable concealedChalkGroup stratigraphy of theIpswichdistrict.

CENOMANIAN CONIACIAN Stage A. jukesbr cortestudinarium M. testudinarius Mytiloides C. guerangeri Macr ? M. geslinianum G coranguinum P M. mantelli . quadrata U. socialis U. anglicus . ( N. juddii M. dixoni O. pilula T Zones S. . lata ofossil M. ) M.

plana ownei spp. Holywell Zig Zag New Pit Nodular Melbury Nodular Seaford Chalk Culver Chalk Lewes Chalk Chalk Marly Chalk Chalk F Chalk W Newhaven Chalk o rm est a ti Blakenham Member on

Stowlangtoft Quarry S

(immediately above borehole) towlangtoft Bor (Bury S District) S 16 inchresistivitylog t Edmunds Marls Plenus towlangtoft Borehole T towlangtoft Borehole isimplied) otternhoe S Cambridge [TL in southernEngland. comparisons withboreholes based onresistivitylog the S Formational interpretationsof ehole 94756882] Series Brandon Chalk Rock towlangtoft succession tone T op Rock V olviceramus involutus Outcr

Ipswich town site investigation boreholes Ipswich District ops &Bor

* Combs [TM 0427 5625] eholes (NB: age of youngest Chalk in borehole not known) Gipping Valley outcrops ? Felixstowe districts the Colchester * Weeley [ TM 148 218] Key Bor

* Harwich [TM 260 329] eholes in

* Stutton [TM 1500 3340] and

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n Key: e w k e flint a l N Belemnitella B ( Gonioteuthis (*U. anglicus) Echinocorys Sphenoceramus 18 and Platyceramus M. testudinarius oysters new range data historical range data

FIGURE 2. The stratigraphical ranges of key Chalk Group outcrops in the Ipswich district (not to scale). *: U. anglicus Zone not proved in the Ipswich district