Planktic foraminiferal stable-isotopes across the EECO: investigating the coupling between temperature and the exogenic carbon pool (ODP Site 1263, Walvis Ridge)

The Late Paleocene - Early Eocene warming trend is characterized by a gradual temperature rise of 5-6°C resulting in the Early Eocene Climatic Optimum “EECO”. This warming trend was punctuated by several “hyperthermals”, geologically brief (<200kyr) episodes of extreme warmth. Recently, a new, ~4.7 million year long, high-resolution benthic foraminiferal stable isotope record of ODP Site 1263 has been presented, which confirms the presence of hyperthermals during and at the termination of the EECO as was previously found for ODP Site 1258. Also, the record reveals a highly significant linear relationship between ∂18O and ∂13C for these events, similar as for their early Eocene counterparts. This indicates a strong coupling between global warming and the release of isotopically light carbon into the ocean-atmosphere system throughout the EECO. Whilst the coupling ∂18O and ∂13C remains stable on short-term time scales, this is not the case for the long-term trend. At ~52 Ma, when a rapid 13C enrichment in carbon data is not accompanied by changes in the oxygen record. Possibly, enhanced carbonate and organic carbon burial rates may be responsible for this shift due to a temporary reduced efficiency of the biological pump. To test this hypothesis, we will present our (preliminary) stable isotopic results of two planktic foraminiferal species derived from the same samples of ODP Site 1263, which portray changes in surface water (Acarinia ssp.) and thermocline waters (Subbotina ssp.).