A reassessment of the stratigraphy of DSDP HOLE 117A Rockall Plateau: implications for the Palaeocene-Eocene boundary

DSDP Hole 117 A provides one of the critical data points in the COSTA & MÜLLER (1978) correlation between the NW European dinoflagellate cyst zonation and the standard nannofossil scheme of MARTINI (1971), because information previously published on this sequence indicated that the base of the Wetzeliella astra Zone coincides with the base of Zone NP 10. On this basis COSTA & MÜLLER (1978) suggested that the base of the W. astra, Zone be used to mark the base of the Eocene in NW Europe. A reinvestigation of the material has shown, however, that neither the base of NP 10 nor the base of the W. astra Zone can be positively identified at the site. Until the relationship between these zones is more fully known, therefore, the base of the Eocene in NW Europe cannot be accurately determined on the basis of the currently accepted dinoflagellate cyst biostratigraphy.