Neogene biotic response and macroevolutionary history in the Western Pacific Warm Pool region: preliminary results of deep-sea ostracods from IODP Expedition 363

Abstract

International Ocean Discovery Program Expedition 363 aims to document the Neogene climate changes and their mechanisms in the Western Pacific Warm Pool on millennial, orbital, and geological timescales. We have been investigating deep-sea ostracods from different sites (including IODP Sites U1482A, U1483A, U1485A, and more sites under investigation) from this expedition to reveal biotic response to these climatic changes as well as macroevolutionary history. Our preliminary results from core catcher samples (one per 5 cores) show that ostracod abundance is much higher in the upper 10–15 cores. It is equivalent to Early–Late Pleistocene depending on the sites. In Site U1482A, certain ostracod genera such as Bythocypris and Agrenocythere occur only in the upper 10 cores of the Early Pleistocene–Present. In contrast, Krithe and Argilloecia occur continuously throughout the cores 1–55 covering from the Late Miocene to the present. Although we should carefully evaluate a possibility of sampling artifact because of low ostracod abundance in the lower cores below 10, it gives us a working hypothesis, i.e., a biotic and environmental change may occurred at around the Pliocene-Pleistocene boundary in Site U1482A, that merits further evaluation with additional samples. Full results will be presented in the conference with additional data.