Late Eocene- Oligocene oxygen- and carbon-isotope record from South Atlantic Ocean, Deep Sea Drilling Project Site 522.

Abstract

A gradual enrichment of 0.5 per mille in the delta18O record of the benthic but not the planktonic foraminifers occurs during the late Eocene. This enrichment is believed to reflect changing bottom-water conditions at Site 522. During the earliest Oligocene a more abrupt enrichment of 0.5 per mille in delta18O occurs in both the benthic and the planktonic records. This early Oligocene shift is interpreted as an increase in average global ice volume. High-resolution isotopic analyses of one lower Oligocene core yield suggestive but inconclusive evidence of the presence of high-frequency fluctuations in the oxygen-isotope record. In conjunction with faunal and floral data, the isotopic data from Site 522 indicate that isotopic temperature scales must be adjusted to account for global ice volume during the Oligocene.- from Authors