The relationship between tectonics and ostracods: ostracods faunal changes under a subduction initiation system in the Tasman Sea

Abstract

Middle Eocene to Pleistocene ostracod faunal assemblages were reconstructed from marine sediment cores obtained in International Ocean Discovery Program (IODP) Expedition 371 Sites U1506, U1508, and U1510 in the Tasman Sea. The Tasman sediment cores are characterized by a regional Eocene-Oligocene unconformity. Recent geological surveys have suggested that the unconformity was possibly tectonic-driven. We discovered abundant neritic ostracods in Eocene and Oligocene sequences whereas the present water depths of all sites are deeper than 1000 meters. Preliminary results show that the signals of uplifting and subsidence varied across time and space, and that the scale of vertical movements is over 500 meters. Beta diversity assessment indicates high heterogeneity of neritic ostracod diversity under the uneven topographic fluctuations in the Paleogene. The later colonization pattern of deep-sea ostracods suggests that the modern deep oceanic setting in the Tasman Sea was probably established around 25 Ma. Future studies will focus on the influence of the paleogeographic changes, especially the subsidence and subsequent development of deep ocean communication, to evolutionary processes of the deep-sea organisms.