The foraminiferal isotopic record across the Eocene/ Oligocene boundary at Deep Sea Drilling Project Site 540.

Abstract

An enrichment occurs in 18O of about 0.5-0.8%o in both benthic foraminifers and surface-dwelling planktonic foraminifers between the latest Eocene and early Oligocene. This early Oligocene maximum is followed by lower 18O values. A 1.2%o d13C decrease in both benthic and planktonic foraminiferal data occurs from the late Eocene to the late Oligocene. There is a correspondence of the 13C signal to deep-sea records; however, the amplitude of this change is greater than previously seen in deep-sea cores, possibly as a result of proximity to terrestrial sources of carbon.-from Authors