Foraminifera and stable isotope record of ODP Leg 105 sites

Faunal and stable isotopic data in Sites 646 and 647 provide a ~0.9-Ma paleoclimatic and paleoceanographic record for the Labrador Sea, that is supported by a floral record for the past ~0.3 Ma. At both sites, most glacial stages generally are dominated by polar fauna and flora with low species diversity. Although minor occurrences of subpolar species also were observed in lowermost parts of several glacial stages in Site 646, the faunal classification of Ruddiman and Mclntyre (1976) suggested the presence of polar ecological water masses in the area during most of the glacial periods. In several glacial stages at Site 647, both the faunal and floral data indicate that early periods were marked by subpolar and transitional ecological water masses. The interglacials are characterized by a polar fauna at Site 646 and by polar and transitional faunas and floras at Site 647. However, several interglacial stages in Site 646 include a subpolar flora, in contrast to a planktonic foraminifer fauna similar to that found in the glacial stages. The occurrence of subpolar water masses in several glacial isotopic stages indicates significant northward advection of warmer waters into the Labrador Sea during the early glacial periods, which provided a corridor of oceanic warmth extending from mid- to high latitudes and contributed an additional source of moisture for continental ice-sheet growth. Similar conditions also were documented in the northwest Labrador Sea, Grand Banks, and the North Atlantic.