Monday, April 02, 2018, 12:15PM - 1:15PM
CIRES & INSTAAR
SEEC room S228 (Sievers Conference Room)
The Pliocene is the most recent time interval in Earth history when global climate was significantly warmer than the present, and as such is considered a potential analog to future climate conditions. Reconstructions from geochemical proxies argue for a mean El Niño-like state during the Pliocene, which is posited to have terminated with the closure of the Central American Seaway (CAS) ~2.8 Ma. However, such interpretations are largely predicated upon the oxygen isotope (δ18O) and Mg/Ca composition of planktic foraminifera belonging to the mixed-layer dwelling species Trilobatus sacculifer with the underlying assumption that the shells are well preserved and geochemically homogeneous. In reality, most T. sacculifer shells are an aggregate mixture of primary, reproductive, and diagenetic calcites that formed under different physiological and/or environmental conditions. Here, I will present novel results from in situ analysis of Pliocene-aged shells of T. sacculifer from the western equatorial Pacific and Caribbean. The resulting seawater δ18O records indicate that the Early Pliocene West Pacific Warm Pool was saltier than modern and the Caribbean attained modern sea surface salinities by 5.2 Ma. These results are consistent with the proposed Pliocene mean El Niño-like state and suggest that either CAS closure had no effect on Caribbean sea surface salinities or that CAS closure predated 5.2 Ma.
Free and open to the public.