This report describes the biostratigraphical age determinations of a suite of Chalk samples from

1:50K Sheet 267. Foraminifera indicate that Cenomanian to Santonian chalks are present

Wilkinson, I.P.

English

NERC Open Research Archive

     Foraminifera from the Chalk of the Newbury area (1:50K sheet 267)    Internal Report IR/03/023        BRITISH GEOLOGICAL SURVEY INTERNAL REPORT IR/03/023   Foraminifera from the Chalk of the Newbury area (1:50K sheet 267) I. P. Wilkinson  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 GD 272191/1999 Key words Biostratigraphy; Foraminifera; Late Cretaceous. Bibliographical reference WILKINSON, I.P.. 2003 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267). British Geological Survey Internal Report, IR/03/023.  5pp.  © NERC 2003  Keyworth, Nottingham   British Geological Survey   2003 The full range of Survey publications is available from the BGS Sales Desks at Nottingham and Edinburgh; see contact details below or shop online at  www.thebgs.co.uk The London Information Office maintains a reference collection of BGS publications including maps for consultation. The Survey publishes an annual catalogue of its maps and other publications; this catalogue is available from any of the BGS Sales Desks. The British Geological Survey carries out the geological survey of 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 its basic research projects. It also undertakes programmes of British technical aid in geology in developing countries as arranged by the Department for International Development and other agencies. The British Geological Survey is a component body of the Natural Environment Research Council.  Keyworth, Nottingham NG12 5GG BRITISH GEOLOGICAL SURVEY  0115-936 3241 Fax 0115-936 3488 e-mail: sales@bgs.ac.uk www.bgs.ac.uk Shop online at: www.thebgs.co.uk Murchison House, West Mains Road, Edinburgh EH9 3LA  0131-667 1000 Fax 0131-668 2683 e-mail: scotsales@bgs.ac.uk London Information Office at the Natural History Museum (Earth Galleries), Exhibition Road, South Kensington, London SW7 2DE  020-7589 4090 Fax 020-7584 8270  020-7942 5344/45 email: bgslondon@bgs.ac.uk Forde House, Park Five Business Centre, Harrier Way, Sowton, Exeter, Devon EX2 7HU  01392-445271 Fax 01392-445371 Geological Survey of Northern Ireland, 20 College Gardens, Belfast BT9 6BS  028-9066 6595 Fax 028-9066 2835 Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB  01491-838800 Fax 01491-692345 Parent Body Natural Environment Research Council, Polaris House, North Star Avenue, Swindon, Wiltshire SN2 1EU  01793-411500 Fax 01793-411501 www.nerc.ac.uk  IR/03/023 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267).   Contents Contents...........................................................................................................................................i Summary .........................................................................................................................................i 1 Introduction ............................................................................................................................2 2 Sample details and conclusions .............................................................................................2 2.1 MPA51398  PMH3629 34909 64215.................................................................................2 2.2 MPA51399  PMH3630 34942 67174.................................................................................2 2.3 MPA51400  PMH3631 35385 63451.................................................................................2 2.4 MPA51401  PMH3632 35147 63831.................................................................................3 2.5 MPA51402  PMH3633 35735 63831.................................................................................3 2.6 MPA51403  PMH3634 35469 64042.................................................................................3 2.7 MPA51404  PMH3635 36799 66152.................................................................................3 2.8 MPA51405  PMH3636 37934 61791.................................................................................3 2.9 MPA51406  PMH3637 37850 61904.................................................................................3 2.10 MPA51407  PMH3638 ...................................................................................................4 2.11 MPA51408  PMH3639 37508 62252 .............................................................................4 2.12 MPA51409  PMH3640 ...................................................................................................4 2.13 MPA51410  PMH3641 37314 62978 .............................................................................4 2.14 MPA51411  PMH3642 37980 66782 .............................................................................5 2.15 MPA51412  PMH3643 ...................................................................................................5 2.16 MPA51413  PMH3644 ...................................................................................................5 2.17 MPA51414  PMH3645 ...................................................................................................5 2.18 MPA51415  PMH3646 38535 62576 .............................................................................5 2.19 MPA51416  PMH3647 ...................................................................................................5 2.20 MPA51417  PMH3648 ...................................................................................................5 2.21 MPA51418  PMH3649 ...................................................................................................6 2.22 MPA51419  PMH3650 ...................................................................................................6 2.23 MPA51420  PMH3651 39793 62085 .............................................................................6 2.24 MPA51421  PMH3652 39748 66361 .............................................................................6 2.25 MPA51422  PMH3653 ...................................................................................................6 2.26 MPA51423  PMH3654 39091 67067 .............................................................................6 3. References ...............................................................................................................................6 Summary This report describes the biostratigraphical age determinations of a suite of Chalk samples from 1:50K Sheet 267.  Foraminifera indicate that Cenomanian to Santonian chalks are present.  i IR/03/023 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267).  1 Introduction A suite of chalk samples from the Newbury area was examined for calcareous microfaunas (foraminifera) in order to determine the biostratigraphical ages. Comparison with other localities in southern England was carried out to relate the foraminiferal assemblages to the new lithostratigraphical framework for the Chalk.  2 Sample details and conclusions The full listing of the species present in each sample is held on file in the Biostratigraphical Records of the BGS held in Keyworth. National Grid References throughout this report refer to 100 km quadrant SU. The foraminiferal zonation used herein is that of Wilkinson (2000).  2.1 MPA51398  PMH3629 34909 64215 The majority of species are long ranging.  However, Cibicides beaumontianus, Stensioeina granulata granulata and a specmen tentatively assigned to Stensioeina granulata polonica were recorded.  No members of the cristata-usakensis lineage were present.  Zone BGS17i or 17ii is suggested.  A position in the upper Seaford Chalk, but probably no higher than the Barrois Sponge Bed (and lateral equivalents) is indicated.  2.2 MPA51399  PMH3630 34942 67174 The presence of Gavelinella cristata together with Bolivinoides strigillatus, Stensioeina granulata perfecta and Stensioeina excsculpta exsculpta places the fauna within the upper part of zone BGS18 (subzones iii or iv).  However, the absence of Rugoglobigerina pilula, Archaeoglobigerina cretacea, etc suggests a position below BGS 18iv.  BGS18iii places the sample in the lower (but not basal) Newhaven Chalk, and a position within the upper part of the U. socialis to lower part of the M. testudinarium macrofaunal zones is inferred.  2.3 MPA51400  PMH3631 35385 63451 Species such as Gavelinella baltica, Tritaxia pyramidata, Gavelinella berthelini, Arenobulimina anglicus and Gavelinella intermedia indicate a position within the the Cenomanian (i.e. stratigraphically no lower than zone BGS1).  The presence of Marsonella ozawai refines this to zones BGS1 to BGS2 (H. carcitanese to lower M. saxbii macrofaunal subzones), but the absence of Pseudotextulariella cretosa suggests the fauna is from BGS1 (H. carcitanense) rather than BGS2. Whether BGS 1 or 2, the lower part of the West Melbury Chalk is inferred.   2 IR/03/023 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267).  2.4 MPA51401  PMH3632 35147 63831 Planktonic taxa dominate the foraminiferal asssemblage.  These include keeled Marginotruncana pseudolinneana, M. marginata and Dicarinella imbricata.  Unkeeled Hedbergella brittonensis and Whiteinella aprica also occur.  Benthonic foraminifera are rare, but include Globorotalina michelinianus and Gyroidinoides nitidus.  The presence of G. michelinianus indicates a stratigraphical position no lower than the 'middle' part of the New Pit Chalk (base of BGS10), but Marginotruncana pseudolinneana does not enter the record until a little higher (Base BGS 11) in the upper part of the New Pit Chalk.  The dominance of long-ranging species and absence of biostratigraphically confined taxa means that the fauna could be as high as the Lower Lewes Chalk (within the lower part of zone BGS12) at which point D. imbricata becomes extinct.  2.5 MPA51402  PMH3633 35735 63831 Stensioeina granulata polonica and Reussella szajnochae praecursor have a concurrent range in zone BGS17iii and basal 18i.  The absence of Gavelinella cristata and G stelligera suggests a position in the former rather than the latter zone.  Stratigraphically, the concurrent zone of the two foraminifera is immediately below Peake's Sponge Bed (and lateral equivalents) in the highest M. coranguinum Zone.  2.6 MPA51403  PMH3634 35469 64042 Gavelinella stelligera, Gavelinella cristata, Stensioeina exsculpta exsculpta and Reussella szajnochae praecursor are present, placing the sample in BGS 18 or possibly the very basal part of BGS19.  The presence of a single fragment tentatively assigned to Vaginulinopsis scariformis, and the absence of taxa such as Stensioeina granulata perfecta, Bolivinoides spp, etc Rugoglobigerina pilula etc makes a position in BGS18ii and above unlikely.  BGS18i seems most likely and the basal Newhaven Chalk is suggested, although the very highest Seaford Chalk (i.e. immediately below Peake's Sponge Bed) can not be ruled out entirely.  2.7 MPA51404  PMH3635 36799 66152 Gavelinella cristata, Stensioeina granulata perfecta, Stensioeina granulata granulata, Stensioeina exsculpta exsculpta and Rugoglobigerina pilula places the sample within zone BGS18iv or very basal BGS19 (equating with the basal U. anglicus Zone to basal O. pilula zone).  A position within the 'middle' part of the Newhaven Chalk is inferred.  2.8 MPA51405  PMH3636 37934 61791 Foraminifera are very rare, poorly preserved and mainly long-ranging planktonic species.  No biostratigraphical conclusions can be drawn.  2.9 MPA51406  PMH3637 37850 61904 Although the foraminiferal association is more diverse compared to MPA 51405, species are long-ranging and of little biostratigraphical usefulness.  Perhaps significant is the absence of  3 IR/03/023 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267).  species of Stensioeina, which are consistently present in BGS14 and above (i.e. within the Seaford Chalk and above).  The foraminifera are no older than BGS 10, characterised by the inception Globototalites michelinianus, in the New Pit Chalk.  However, further refinement is not possible with certainty.  Gavelinella sp. C of Bailey (PhD thesis) is apparently confined to the M. cortestudinarium macrofauna Zone (Foraminiferal zone A of Bailey, PhD thesis).  Although not a satisfactory criterion to base a biostratigraphical conclusion, its presence here may indicate the upper part of the Lewes Chalk.  This is supported by the presence of a single fragment tentatively assigned to Osangularia cordieriana, a species that appears for the first time at about the East Cliff Marls (and lateral equivalents), in other words, close to the Lewes/Seaford Chalk boundary.  2.10 MPA51407  PMH3638  Registered but not examined for foraminifera at this time.  2.11 MPA51408  PMH3639 37508 62252 Gavelinella cenomanica, Gavelinella baltica, Gavelinella intermedia and Plectina mariae are frequent to common in the sample, indicating a Cenomanian age.  This can be further refined by the presence of Plectina cenomana and Rotalipora cushmani, both of which are confined to the upper part of the stage.The former first appears at the base of zone BGS4 (inermis macrofaunal zone) and the inception of the latter is at the base of BGS4iii (acutus macrofaunal zone).  Rare specimens tentatively assigned to Lingulogavelinella globosa, if correctly identified, may indicate the presence of BGS6, although other species that would be expected in that zone are not present.  The assemblage can thus be placed within BGS4iii (-BGS6) and the Zigzag Chalk is inferred.  2.12 MPA51409  PMH3640 Registered but not examined for foraminifera at this time.  2.13 MPA51410  PMH3641 37314 62978 The concurrent range of Stensioeina exsculpta exsculpta and Lingulogavelinella arnagerensis places the association within zone BGS14 to BGS17ii (coranguinum macrofaunal zone) and the Seaford Chalk is inferred.  The former species first appears between the Upper East Cliff Marl and the Hope Point Marl (and lateral equivalents) and ranges through to the basal Campanian.  The latter species appears within the Turonian and disappears from the record a little above Whitaker's 3" Flint (and lateral equivalents).  This age determination can be tentatively refined. Archaeoglobigerina bosquensis, a rare and patchily distributed species (which reduces its biostratigraphical usefulness somewhat) apparently has its inception within the uppermost Coniacian (within BGS 16).  Reussella kelleri, a long ranging Lazarus species, is generally absent in the coranguinum Zone, below Whittaker's 3" Flint.  If this holds true here, then stratigraphically the best fit is immediately above the latter flint band (basal BGS17ii).  The Seaford Chalk is thus indicated and a position within the 'middle' part of the formation seems possible.   4 IR/03/023 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267).  2.14 MPA51411  PMH3642 37980 66782 The presence of Gavelinella cristata and Stensioeina granulata perfecta places the lowest possible stratigraphical position immediately above Peake's Sponge Bed (and lateral equivalent).  Their inception marks the base of foraminiferal zone BGS18 and subzone BGS18ii respectively.  Stensioeina granulata granulata is also present suggesting a position no higher than BGS18iii, although the absence of species belonging to the genus Bolivinoides suggests the position is not as high as that.  BGS18ii ('mid' socialis macrofaunal zone) and BGS18iii ('upper' socialis to testudinarius macrofaunal zones) indicate that the sample was taken from the lower (but not basal) part of the Newhaven Chalk Formation.  2.15 MPA51412  PMH3643 Registered but not examined for foraminifera at this time.  2.16 MPA51413  PMH3644 Registered but not examined for foraminifera at this time.  2.17 MPA51414  PMH3645 Registered but not examined for foraminifera at this time.  2.18 MPA51415  PMH3646 38535 62576 The occurrence of Lingulogavelinella arnagerensis places the assemblage stratigraphically no higher than immediately above the Whitaker's 3" Flint (in the upper part of the Seaford Chalk).  Stensioeina exsculpta exsculpta indicates a position above the East Cliff Marls.  A more refined age determination is not possible, although the presence of frequent specimens of Reussella kelleri suggests the assemblage came from immediately above the Whitaker's 3" Flint.  This last suggestion must be treated with caution.  Reussella kelleri is a 'Lazarus' species which is generally absent in the lower part of the Seaford Chalk (lower part of the coranguinum Zone) below Whitaker's 3" Flint Band.  2.19 MPA51416  PMH3647 Registered but not examined for foraminifera at this time.  2.20 MPA51417  PMH3648 Registered but not examined for foraminifera at this time.   5 IR/03/023 Foraminifera from the Chalk of the Newbury area (1:50K sheet 267).  2.21 MPA51418  PMH3649 Registered but not examined for foraminifera at this time.  2.22 MPA51419  PMH3650 Registered but not examined for foraminifera at this time.  2.23 MPA51420  PMH3651 39793 62085 Foraminifer are not common in the sample. Stensioeina granulata polonica is the zonal index for BGS17 (upper part of the coranguinum Zone).  The species appears first at the Chartham Flint (and lateral equivalents)and ranges up to Peake's Sponge Bed.  Rare specimens of Reussella kelleri suggests that the sample of the sample may be from above the Whitaker's 3" Flint (and lateral equivalents), although this conclusion is only tentatively made (see MPA51415).  The upper part of the Seaford Chalk is indicated.  2.24 MPA51421  PMH3652 39748 66361 Gavelinella cristata, Stensioeina granulata perfecta, Stensioeina granulata granulata, Gavelinella stelligera, Reussella kelleri were among the species recorded from the sample.  Specimens of Bolivinoides, Rugoglobigerina pilula, Archaeoglobigerina cretacea and other species characteristic of higher stratigraphical levels were not present.  This suggests that the assemblage is of BGS18ii age ('mid' socialis Zone) in the lower, but not basal, Newhaven Chalk.  2.25 MPA51422  PMH3653  Registered but not examined for foraminifera at this time.  2.26 MPA51423  PMH3654 39091 67067 Gavelinella cristata, Stensioeina granulata perfecta, Reussella szajnochae praecursor, Gavelinella stelligera formed the largest part of the assemblage. This suggests that the assemblage is of BGS18ii age ('mid' socialis Zone).  Species of Bolivinoides were not found, but very rare, poorly preserved specimens tentatively assigned to Stensioeina exsculpta gracilis and Rugoglobigerina pilua were noted.  If they are correctly identified and in situ, then the age of the association would be stratigraphically slightly younger (BGS18iv; U. anglicus Zone).  The association is no younger than very basal BGS19i (pilula macrofaunal zone).  The Lower, but not basal, Newhaven Chalk is indicated. 3. References 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.  6 

Foraminifera from the Chalk of the Newbury area (1:50K sheet 267)

http://nora.nerc.ac.uk/id/eprint/527493/1/IR03023.pdf

Foraminifera from the Chalk of the Newbury area (1:50K sheet 267)

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