(Table 1) Planktonic foraminiferal communities at DSDP Holes 94-609B and 94-609
The planktonic foraminifers in 124 samples from Holes 609 and 609B have been analyzed quantitatively to see whether oceanographic events in the late Miocene and early Pliocene (6.5-4.0 Ma) are reflected in the distribution of individual species. Major changes in sea-surface temperature and bottom-water circulation are postulated, mainly on the basis of the coiling-direction ratios in Neogloboquadrina pachyderma (Ehrenberg) and a dissolution index. A cool interval peaking at around 6.2 Ma was followed by climatic fluctuations, possibly indicative of glacial cycles, before a general warming in the Pliocene. Intense dissolution of CaCO3 at this site on both sides of the Miocene/Pliocene boundary is inferred to have resulted from the presence of Antarctic Bottom Water, and an influx of less aggressive North Atlantic Deep Water is indicated at the actual boundary. These climatic and oceanographic changes are tentatively linked to the Messinian salinity crisis in the Mediterranean.