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Regional Studies: Stratigraphy, Tectonics and Volcanism |
British Geological Survey, Keyworth, Nottingham NG12 5GG, UK
Apectodinium (Costa & Downie 1976) Lentin & Williams 1977, a genus of wetzeliellioid dinoflagellate cyst, has been widely reported from the Upper Paleocene (Thanetian) and lowermost Eocene of the UK North Sea and from onshore UK and continental Europe. Its distinctive appearance and common occurrence have led to the selection of members of the genus as index species in a number of dinoflagellate cyst zonation schemes covering the Upper Paleocene and Lower Eocene, e.g. by Costa & Downie (1976), Heilmann-Clausen (1985), Costa & Manum (1988), Powell (1988, 1992) and Schröder (1992).
Powell (1988) suggested that, when working with cuttings, the first downhole occurrence (FDO) of Apectodinium augustum (Harland 1979) Lentin & Williams 1981 can be used as a good approximation to the top of the Paleocene. The lowermost occurrence of the genus was reported by Costa & Downie (1976) as occurring at a level equivalent to the base of the late Paleocene calcareous nannoplankton biozone NP9 of Martini (1971) in NW Europe. This was referred to as the ‘Base Apectodinium Datum’ by Powell (1988). However, several authors have reported the occurrence of Apectodinium spp. at lower stratigraphic levels. Jan du Chêne et al. (1975) recorded Apectodinium spp. (as Wetzeliella) in samples assigned to biozones NP5 to NP8 from Haute-Savoie, France. Powell et al. (1993) reported an early (pre-NP9) occurrence of the Base Apectodinium Datum in Thanetian strata at Herne Bay in Kent, within the Reculver Silts Member below the Reculver Tabular Band. These beds were assigned to biozone NP8 by
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