[M-IS17] 古気候・古海洋変動

[MIS17-34] 白亜紀の温暖期から寒冷期への移行期に認められた深海循環の逆転

*大河原 秀祐¹、海保 邦夫¹、池原 実² (1.東北大学大学院理学研究科、2.高知大学海洋コア総合研究センター)

キーワード：白亜紀、深海循環、底生有孔虫、炭素同位体比、酸素同位体比

Globally warm climates from the Albian to the Coniacian were followed by cool climates from the Campanian to the Maastrichtian. Although deep-sea circulation is related to global climate, this relationship remains unclarified in the Cretaceous. This paper reconstructed deep-sea circulation during the middle to late Cretaceous using carbon and oxygen isotopes from benthic foraminiferal tests at 1,000-2,000 m paleowater depth in the Pacific, Indian, North Atlantic, South Atlantic, and Southern Oceans. The carbon isotope data showed that the water masses in the Pacific and Indian Oceans were newer than those in the North Atlantic during the early Cenomanian and Coniacian, but the reverse occured during the OAE 2, the mid-Campanian, and the Maastrichtian. Deep-sea temperature determinations based on the oxygen isotope data showed that the reverse of the global deep-sea circulation characterized the transition from the warm to the cool period. Based on the current understanding of the relationship between deep-sea circulation and temperature during the Paleocene-Eocene Thermal Maximum, the sources of the warm-water circulation culminated at the OAE 2 wheras the cool-water circulation derived from the middle-low latitudes and high latitudes.