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Abstract: Chronostratigraphic Applications of Pliocene and Lower Pleistocene Dinoflagellates and Acritarchs in the North Atlantic Region

Head, Martin J. and Norris, Geoffrey - University of Toronto

Several Deep Sea Drilling Project (DSDP) holes with excellent magneto-stratigraphic and biostratigraphic control have been analyzed for their dinoflagellate and acritarch content. Results confirm the applicability of dinoflagellates and acritarchs for high resolution biostratigraphy of the Pliocene. DSDP Hole 603C, situated on the lower continental rise off New Jersey, has an essentially complete Pliocene and lowermost Pleistocene sedimentary record. DSDP Hole 610A, in the Rockall Trough, eastern Atlantic, has an almost complete section spanning middle lower Pliocene through lower Pleistocene. Ocean Drilling Program Hole 646B in the Labrador Sea offers a third point of comparison.

Biostratigraphically useful events recognized for the lower lower Pliocene include the highest occurrences (HO) of Pyxidinopsis pastilliformis and Cristadinium diminutivum; for the middle lower Pliocene include lowest occurrence Corrudinium sp. 1 of de Vernal and Mudie 1989, highest persistent occurrence (HPO) of Reticulatosphaera actino-coronata, and the HO of Cyst type 1 of de Vernal and Mudie 1989; and for the upper lower Pliocene include the HPO of the Batiacasphaera micropapillata / B. minuta complex. The lower upper Pliocene (Gauss magnetochron) is characterized by the highest occurrences of many taxa including Edwardsiella sexispinosa and Invertocysta tabulata. The upper upper Pliocene is marked by the HCO of Cymatiosphaera? invaginata.

Some magnetostratigraphically-calibrated dinoflagellate events can be recognized within the Plio-Pleistocene of the southern North Sea basin where they improve the chronostratigraphy of these imprecisely-dated, restricted marine deposits.

AAPG Search and Discovery Article #90933©1998 ABGP/AAPG International Conference and Exhibition, Rio de Janeiro, Brazil