Whole-rock oxygen and carbon isotope stratigraphy of the Paleogene and Cretaceous/Tertiary boundary in Hole 807C

Abstract

Whole-rock δ18O analyses of the Paleogene and Upper Cretaceous succession at Ocean Drilling Program Hole 807C suggest the presence of hiatuses between 876.95 and 894.47 mbsf and between 1138.82 and 1149.94 mbsf. The δ13C data show a pronounced positive excursion between 1130 and 1180 kbsf that corresponds to the positive δ13C values characteristic of the Paleocene. Despite the stratigraphic breaks in the section, the δ18O data show a systematic increase between 1360 mbsf and the hiatus between 876.95 and 894.47 mbsf, which is consistent with previous suggestions of long-term climatic cooling through the Paleogene. The Cretaceous/Tertiary transition is apparently complete in this section and is of remarkable thickness. The expanded nature of this portion of the succession is probably the result of secondary depositional processes. High-resolution sampling across this boundary may reveal detailed structure of the δ13C decline associated with the extinctions that mark the termination of the Cretaceous. -Authors