Orbital obliquity cycles recorded in Kuroshio Current region, eastern Asia, around Plio–Pleistocene boundary

Global climate underwent a period of significant cooling at the Plio–Pleistocene Transition (∼2.6 Ma). The influence of this change on the Kuroshio Current region in the Pacific Ocean, off eastern Asia, is not well known. In this study, we clarify temporal changes in the paleoenvironment under the i...

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Bibliographic Details
Published in:Quaternary science reviews 2016-05, Vol.140, p.67-74
Main Authors: Iwatani, Hokuto, Kondo, Yasuo, Irizuki, Toshiaki, Iwai, Masao, Ikehara, Minoru
Format: Article
Language:English
Subjects:
Brackish
Kuroshio
Marine
Orbital obliquity cycle
Ostracoda
Plio–Pleistocene
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Summary:Global climate underwent a period of significant cooling at the Plio–Pleistocene Transition (∼2.6 Ma). The influence of this change on the Kuroshio Current region in the Pacific Ocean, off eastern Asia, is not well known. In this study, we clarify temporal changes in the paleoenvironment under the influence of the Kuroshio Current during the late Pliocene and early Pleistocene using high-resolution faunal proxy records of fossil Ostracoda (Crustacea). The study unit is the Ananai Formation in the southeastern region of Shikoku, southwest Japan. The modern analog technique (MAT) is employed for the quantitative estimation of paleo-bottom water temperatures (PBWTs) and paleo-water depth (PWD) during the deposition of the formation. Ostracode MAT results show PBWT fluctuations during warmest and coldest months, with values of 16°C–20 °C and 12°C–16 °C, respectively, and a PWD of 70–140 m, reflecting sea-level oscillations. Moreover, the PBWT in the coldest month is 3 °C–4 °C lower than present-day water temperatures at the same shallow water depths. Temporal changes in these paleoenvironmental variables based on MAT are in good agreement with global oxygen isotope records. Orbital obliquity cycles with 41-kyr periodicity are recorded for the first time in an onshore section in the Kuroshio Current region at the Plio–Pleistocene boundary interval. •More than 150 ostracode were identified from the Plio–Pleistocene Ananai Formation.•MAT results showed fluctuations of PBWTs in the warmest and coldest months, and PWD.•Reconstructed environmental variables correspond to 41-kyr orbital obliquity cycles.•PBWTc was linked with the Kuroshio intensity as a result of global cooling.
ISSN:0277-3791
1873-457X
DOI:10.1016/j.quascirev.2016.03.025