High resolution stable isotope and carbonate variability during the early Oligocene climate

Abstract The rapid global increase in benthic foraminiferal δ18O in the early Oligocene (~33.6 Ma) has been taken to imply the first appearance of large, permanent ice sheets on Antarctica, possibly coupled to deep sea cooling and/or Northern Hemisphere ice growth. This oxygen isotope shift is accompanied by a reorganization of the global carbon cycle, identified by a δ13C increase that slightly lags the glacially-mediated δ18O transition. Here, we present a new record of the early Oligocene climate transition from the subtropical South Atlantic Ocean. To investigate climatic and carbon cycle variability in the transition from the early Paleogene “greenhouse ” into the Oligocene “icehouse ” world, we have developed carbonate content, coarse fraction, and benthic foraminiferal carbon and oxygen stable isotope records for the earliest Oligocene at Ocean Drilling Program (ODP) Site 1263. These records represent the highest-resolution reconstruction of the Eocene/Oligocene from the Atlantic basin to date, and provide us with a unique opportunity to investigate the fine-scale interplay of glaciation and the global carbon cycle