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Regional Studies: Stratigraphy, Tectonics and Volcanism |
1 Millennia Ltd, Unit 3, Weyside Park, Newman Lane, Alton, Hampshire GU34 2PJ, UK
2 Laboratory of Palaeobotany and Palynology, University of Utrecht, Heidelberglaan 2, 3584 CS Utrecht, The Netherlands
3 The Lexis Group, Albion House, 9 Albion Avenue, Blackpool, Lancashire FY3 8NA, UK
Detailed study of the aquatic palynomorph assemblages, particularly dinoflagellate cysts, from the type-Thanetian and related sections in southeast England has enabled a detailed biostratigraphic and sequence biostratigraphic analysis to be carried out. The base of the Thanetian Stage at Pegwell Bay lies above the base of the Alisocysta margarita (Ama) biozone; the overlying type-Thanetian is assigned to the Apectodinium hyperacanthum (Ahy) and Apectodinium augustum (Aau) biozones. The base of the Ypresian succession is drawn at the base of the Harwich Formation at Lower Upnor corresponding to the base of the Glaphyrocysta ordinata (Gor) biozone. The Wetzeliella astra (Was) biozone is characteristic of the lower London Clay Formation at Herne Bay. Five Thanetian and three Ypresian sequences are identified through consideration of dinoflagellate cyst palaeoecology and sedimentological evidence. Deepening and shallowing trends enable transgressive and highstand systems tracts to be identified. The maximum flooding surfaces are identified and correlated into the North Sea Basin (Central Graben) as a series of eight primary condensed sections, two of which (characterized by the Areoligera and Apectodinium acmes) are of a second-order scale (the other six are third-order). Lowstand system tracts are represented onshore by a series of seven unconformities (type 1 sequence boundaries) with the amount of missing time below biozonal resolution. A single type 2 sequence boundary is also evident in the Ypresian succession at Wrabness. The unconformities may be correlated into more distal locations in the North Sea Basin where lowstand sandstone deposition is characteristic.
