Biostratigraphic and paleoenvironmental interpretation of the Goban Spur region based on a study of calcareous nannoplankton.

Abstract

The nannoplankton stratigraphy of Leg 80 (Goban Spur and adjacent Porcupine Abyssal Plain) is summarized. Oldest sediments overlying Hercynian basement are lower to middle Barremian (Site 549). On the ocean crust (Site 550) the oldest strata are upper Albian. The Barremian syn-rift sediments are separated from the post-rift sediments (Albian) by an unconformity representing a 12Ma hiatus. The distribution of nannoplankton assemblages makes it possible to reconstruct a curve of relative surface water temperature for the Tertiary. Latitudinal differentiation of the assemblages has become more pronounced since the Oligocene, and particularly since the middle Miocene. The beginning of the glaciation in the N hemisphere about 2.7-2.5Ma ago is indicated by the disappearance of discoasters and the occurrence of ice-rafted material. The Quaternary sequences are characterized by alternations of nannoplankton-rich (interglacial) and nannoplanton-poor (glacial) layers.-from Author