Abstract:
In 1985 the ODP ship JOIDES Resolution recovered a core from the center of the Labrador Sea (LS). Both piston and drill cores from ODP site 647A (WD-3861m), on the southern margin of the Gloria Drift, recovered a Quaternary record which was approximately 100m thick, and based on paleo-magnetic measurements, the base of the section was 1 Ma (base of the Olduvai interval). Three water masses flow through and converge here--the Eastern North Atlantic current which flows west and then south through LS, the Denmark Strait (DS) overflow water which flows out of the south out of Norwegian Sea and western North Atlantic current which comes from the Arctic through Baffin Bay. However during glacial periods water from the North is restricted as well as the Eastern N. Atlantic flow. These variations can be detected using benthic and planktic foraminiferal assemblages from these sections. The interglacial stages (OIS stages, 1, 5, 7, 9, 11, 13, 15, 17, and 19 (all interstadials) were largely dominated by the benthic foraminifera Epistominella exigua, Nuttallides umbonifera, and Pullenia subcarinata. During the glacial periods Uvigerina peregrina was common, reflecting the lower oxygen conditions during glacials. The Antarctic species, N. umbonifera, had not been reported previously in the N. Atlantic. Starting in OIS 5, the Arctic species, Stetsonia arctica, became a subdominant species and occurred intermittently from this section to the 100m mark for the first in both interglacial and glacial sections. At the top of the Olduvai a species typically associated with Antarctic bottom water, Eponides weddellensis, appears for the first time and becomes a dominant species to the base of the section, signaling a major shift in water masses near the Plio-Pleistocene boundary.