Digitized records of optical desnity in many North Atlantic cores exihibt rapid changes from lighter to darker extrems, typically within less than 200 years, at the 5d/5e, 5b/5c and 4/5 boundaries. In cores from DSDP site 609 the changes from lighter to darker color coincide with increasing in relative abundance of Neogloboquadrina pachyderma (l.c.), with increases in abundances of lithic grains and with decreasing in carbonate content. The rapid changes to dark color, therefore, are climate-driven and correspond to a lowering of seas surface temperatures and to increases in amounts of ice rafted debris relative to biogenic carbonate. At the 5d&4c boundary, delta18O in N. pachyderma (l.c.) increases abruptly with the change to darker sediments as expected for cooler sea surface temperatures. At the 4/5 boundary, however, delta18O decreases with the change to darker sediment and cooler sea surface temperatures, suggesting that a layer of fresh surface water was present in the North Atlantic at that time.

Supplement to: Bond, Gerard C; Broecker, Wallace S; Lotti, Rusty; McManus, Jerry F (1992): Abrupt color changes in isotope stage 5 in North Atlantic deep sea cores: implications for rapid change of climate-driven events. In: Kukla, G J & Went, E (eds.), Start of Glacial. Global Environmental Change, NATO ASI Series I, Vol. 3, Springer, Berlin, Heidelberg, New York, 3, 185-205