Oligocene Biomarker Temperature Estimates from ODP Hole 154-929A and DSDP Hole 75-516F

Site 516 (paleolatitude ~ 36°S) and western equatorial Atlantic Ocean Drilling

Project

Site 929 (paleolatitude ~ 0°), combined with a compilation of existing SST records and climate modeling. In this relatively low CO2 Oligocene world (~300-700 ppm), warm climates similar to those of the late Eocene continued with only brief interruptions, while the Antarctic ice sheet waxed and waned. SSTs are spatially heterogenous, but generally support late Oligocene warming coincident with declining atmospheric CO2.

This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO2 and/or ocean gateways, and is only partially explained by current climate models. Though the dominant climate drivers of this enigmatic Oligocene world remain unclear, our results help fill a gap in understanding past Cenozoic climates and the way long-term climate sensitivity responded to varying background climate states.