(Table 1) Distribution of planktonic foraminifera in the Paleocene/Cretaceous section of DSDP Hole 93-605

Analysis of planktonic foraminifers from Section 605-66-1 established the Cretaceous/Tertiary (K/T) boundary between 68 and 73 cm. Comparison with the detailed zonation established at El Kef, Tunisia, indicates that some of the section may be missing, probably because of drilling disturbance. The preservation of the planktonic foraminifers is generally good, particularly in the basal Paleocene section. However, extensive dissolution and the many broken specimens render quantitative estimates unreliable. There were no microtektite-like spherules to suggest a layer rich in extraterrestrial components, as have been found in most complete pelagic K/T boundary sections. The better preservation of Paleocene foraminiferal test in this core and in many other DSDP cores from other basins is probably due to a change in oceanic carbonate chemistry exactly at the K/T boundary. This may have been caused by a temporary and almost complete disappearance of carbonate-fixing organisms at the boundary.