The mid Cretaceous of north-east England : macrofauna, microfauna, sedimentology, stable isotope geochemistry and correlation with sections in southern England and north-west Germany.

Francis. Mitchell, Simon
(1993) The mid Cretaceous of north-east England : macrofauna, microfauna, sedimentology, stable isotope geochemistry and correlation with sections in southern England and north-west Germany. PhD thesis, University of Liverpool.

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The lithostratigraphy of the mid Cretaceous of north-east England (Speeton, South Ferriby and Hunstanton) is revised and a number of new terms are introduced. The following formations are accepted: Speeton Clay Formation, Skegness Clay Formation, Sutterby Marl Formation, Langton Sand Formation (new), Carstone Formation, Hunstanton Red Chalk Formation, Speeton Chalk Formation (new) and Welton Chalk Formation. The Ferriby Chalk Formation is rejected as it includes the Red Chalk which has always been treated historically as a separate unit. New members (Buckton and Bempton members) are introduced for subdivision of the Welton Chalk Formation. The detailed macrofossil biostratigraphy of the late Barremian to Lower Turonian is presented and the age of the various lithostratigraphic units determined. A biostratigraphic framework is employed that relates the traditional ammonite zonation with other macrofossil zonal schemes (belemnites, inoceramids, brachiopods) and a large number of bioevents. The Speeton Oay Formation ranges in age from the Berriasian to the Lower Albian inclusive (previous ages including the Middle and Upper Albian are based on fallen material from the Red Chalk). The Hunstanton Red Chalk Formation ranges from the Middle Albian to the early Lower Cenomanian. The Speeton Chalk ranges from the early Lower Cenomanian to the late Upper Cenomanian. The Welton Chalk ranges in age from the late Upper Cenomanian into the Turonian. The microfaunal (foraminifera and ostracoda) biostratigraphy of the Upper Barremian to the late Middle Cenomanian is studied in detail. The foraminiferal succession at Speeton differs from the successions in the Anglo-Paris Basin and shows affinity with the successions in the Southern North Sea Basin and north-west Germany. A correlation between the detailed macrofossil and microfossil biostratigraphies is demonstrated and a revised foraminiferal zonation proposed. The ostracod succession is of high biostratigraphic value in the Aptian, but the diachronous appearance of many species renders ostracods less valuable for correlation in the Albian. In the Cenomanian ostracods are largely excluded for paleeoecological reasons. Detailed correlations of the succession at Speeton with successions on the East Midlands Shelf, in the Anglo-Paris Basin, Southern North Sea and north-west Germany are demonstrated. In the Cenomanian the chalks at Speeton are distinctly rhythmic and a total of forty-three rhythms can be correlated bed-for-bed between Speeton and the Anglo-Paris Basin by using key marker horizons. The distribution of regionally important erosion surfaces and calcarenitic chalks is used to construct sea-level charts for the mid-Cretaceous. Stable isotopes of carbon and oxygen have been studied from the late Lower Cenomanian to the early Turonian at Speeton. During this interval al3c excursions are directly associated with the initial flooding surfaces following sequence boundaries. A detailed study of the rnid-Cretaceous foraminiferal palreoecology of north-east England is undertaken and a number of assemblages related to water depth and different watermasses are recognised. The watermasses reflect changes in oceanic circulation either promoting or restricting the passage of warm Tethyan derived currents into the North Sea via the Polish Trough. A study of the macrofaunal palaeoecology recognises the existence of events when characteristic faunal elements appear. These events are invariably related to sea-level fluctuations and the relative positioning of watermasses, with the influx of cold water faunas at the times of the development of a North Sea Watermass. Appendix 1 presents paleeontological results. A number of new species of macroand microfossil are formally described, while many other forms are left under open nomenclature. A detailed analysis of belemnite biometries is provided and their biostratigraphic value demonstrated. Appendix 2 provides detailed descriptions of all the sections studied in north-east England as many of these are difficult to access and poorly exposed.

Item Type: Thesis (PhD)
Depositing User: Symplectic Admin
Date Deposited: 23 Oct 2023 11:00
Last Modified: 23 Oct 2023 11:11
DOI: 10.17638/03176185
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