Late Quaternary sedimentation in the western north Atlantic: stratigraphy and paleoceanography
Abstract A detailed analysis of stratigraphic indices was undertaken to study paleoclimatic change in the western North Atlantic. Three stratigraphic indicators — carbonate content, Globorotalia menardii , and Uvigerina peregrina — were tested in ten radiocarbon dated cores from the North American continental margin. Of these, carbonate content appears to be most accurate. Carbonate content exhibits two major increases from late glacial time to the present; estimated ages of the average of the mid-point of these increase are 13 200 B.P. and 8600 B.P. An absolute chronology was established down fifteen cores using these stratigraphic indicators and the radiocarbon dates. Sea-surface temperature (SST) estimates derived from planktonic foraminifera were mapped at 2000-yr intervals from 2000 B.P. to 14 000 B.P. SST warms rapidly from 12 000 to 8000 B.P., reaches a maximum between 8000 and 6000 B.P., and gradually cools after 6000 B.P. Bottom waters were monitored with Uvigerina peregrina and dissolution indices. The disappearance of Uvigerina suggests that the water type it lives in (low O 2 ?) started to thin from both the top and bottom by 13 000 B.P. and by 7300 B.P. had disappeared. Fragmentation of planktonic foraminifera was used as an index of dissolution. In most cores dissolution was intense during late glacial time, lessened during early postglacial time and resumed in the late postglacial.