The Middle Eocene Climatic Optimum: a multi-proxy record of paleoceanographic changes in the South Atlantic (ODP Site 1263)

The Middle Eocene Climatic Optimum (MECO) is one of the major and less understood short-term Cenozoic climatic perturbations. The MECO (~40 Ma) interrupted the overall cooling trend of the middle Eocene with a global and transient (~500 Kyr) temperature increase in surface and deep ocean waters (Bohaty et al., 2009). It is recorded globally in pronounced negative δ13C and δ18O values in marine carbonates and coeval shallowing of the CCD (Bohaty et al., 2009). In order to better understand the character of warming, CCD changes, and ecological disruption of this event, we are in the process of producing a high resolution, multi-proxy study on ODP Site 1263 sediments. Site 1263 (South Atlantic, ~2000 m paleodepth) presents a continuous and expanded record of the MECO event. In order to investigate ocean floor paleoenvironmental modifications across the MECO we are developing a record of benthic foraminiferal assemblages in the ≥63 μm size fraction. We will also measure oxygen and carbon stable isotopes on species-specific benthic and planktic foraminifera in order to evaluate difference between surface and deep-water temperature changes, the character of water-column stratification, and potential impacts on export productivity. Organic biomarkers will also be investigated in conjunction with carbonate analyses. TEX86 indices will be applied to evaluate SST patterns and relationships to bulk and foraminiferal δ18O records, higher-plant n-alkanes will be measured to investigate possible links between warming and perturbations of the hydrological cycle. We thus will provide the first integrated, high resolution record of surface and deep-ocean environmental changes and effects on biota across the enigmatic MECO. Bibliography Bohaty et al. (2009). Coupled greenhouse warming and deep-sea acidification in the Middle Eocene. Paleoceanography 24.