Comparison of ice-rafted debris and physical properties in ODP Site 1094 (South Atlantic) with the Vostok ice core over the last four climatic cycles

Abstract

Visual counts of ice-rafted debris (IRD), foraminifera, and radiolaria were made for ∼1500 samples in Site 1094 spanning the last four climatic cycles (marine isotope stages 1–11). Most, but not all, of the IRD variability is captured by whole-core physical properties including magnetic susceptibility and γ-ray attenuation bulk density. Glacial periods are marked by high IRD abundance and millennial-scale variability, which may reflect instability of ice shelves in the Weddell Sea region. Each interglacial period exhibits low IRD and high foraminiferal abundance during the early part of the interglacial, indicating relatively warm sea-surface temperatures and reduced influence of sea ice. IRD increases and foraminiferal abundances decrease during the latter part of each interglacial, indicating a return to more glacial-like conditions. Glacial terminations I and V are each characterized by a step-wise reduction in ice-rafting punctuated by a brief pulse in IRD delivery and reversal in δ 18O. The coarse fraction of the sediment is dominated by ash and radiolaria, and the relative abundance of these components is remarkably similar to the concentration of Na + in Vostok. Each of these variables is believed to be controlled mainly by sea-ice cover, thereby providing a means for sediment–ice core correlation.