[M-IS18] Paleoclimatology and paleoceanography

[MIS18-P17] Oligocene paleoceanography in the context of the Antarctic ice sheet changes

★Invited Papers

*Hiroki Matsui¹ (1.Graduate School of International Resource Sciences, Akita University)

Keywords:Oligocene, Antarctic ice sheet, Planktic foraminifera

Earth's climate has changed from greenhouse to icehouse during the Cenozoic era, and the Oligocene is a transitional period from 34 Ma to 23 Ma. After the appearance of the Antarctic ice sheet at the Eocene/Oligocene boundary, its ice sheet repeatedly developed and decayed during the early Oligocene and decayed during the late Oligocene, and again developed at the Oligocene/Miocene boundary. Investigating paleoceanography in the context of the above ice sheet changes allows better understanding of the Oligocene (and Cenozoic) climate system. However, because of the appearance and growth of the Antarctic ice sheet, Oligocene species diversity is generally low, hampering the detailed understanding of the paleoclimatic changes. Similarly, widespread hiatus and unconformity have been recognized for the Oligocene, resulting in the small number of continuous records. In this presentation, Oligocene paleoceanographic records are reviewed to discuss the influence of the Antarctic ice sheet changes. Focusing on fossil assemblages such as planktic foraminifera and calcareous nannofossil, and on sea surface temperature records, current understanding and outlook of Oligocene paleocenography are summarized.