CREATING AN EXTENSIVE, MULTI-SPECIES PLANKTIC ISOTOPE RECORD AT A MIDDLE EOCENE HIGH LATITUDE SITE

The Eocene (~34-56 Ma), a warm epoch resulting from particularly high greenhouse gas concentrations, is often used as an analog for Earth’s anticipated climate. Of particular interest is how biogeochemical cycles such as the biological carbon pump functioned under these greenhouse conditions. Few sites have the excellent fossil preservation needed to use traditional biological pump proxies like multi-species carbon isotopes in planktic foraminifera. This project focuses on five samples from one such site in the North Atlantic, Expedition 342 Site 1408 at 41° 26.3'N, that span the middle Eocene (planktic foraminiferal Zones E9 through E13). In total, 20 macroperforate species across 11 genera (Acarinina, Catapsydrax, Globigerinatheka, Globoturborotalita, Guembelitrioides, Hantkenina, Morozovelloides, Orbulinoides, Praemurica?, Subbotina, and Turborotalia) have been analyzed from these samples for stable carbon and oxygen isotopes in up to six narrow sieve size fractions. Analyzed taxa span a range of water column depths and include measurements from never-before-analyzed Praemurica? lozanoi and Globigerinatheka barri. Surprisingly, initial measurements have produced δ¹³C results within one per mille of measurements made on the same genera in Tanzania, a much lower latitude site than Site U1408. Carbon isotope gradients between surface and deeper dwelling species increase in the sample dated from Zone E12, suggesting greater remineralization in the surface ocean during this period of global warmth. Ultimately, we hope this data will provide new insights into carbon cycling in the Eocene.