1994 Fiscal Year Final Research Report Summary
Deep water circulation change in the Northwest Pacific during the Late Quaternary
| Project/Area Number |
05640517
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Stratigraphy/Paleontology
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| Research Institution | Kochi University |
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Principal Investigator |
YASUDA Hisato Kochi Univ., Dept.of Geology, Associate Prof., 理学部, 助教授 (90175646)
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| Project Period (FY) |
1993 – 1994
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| Keywords | benthic foraminifera / deep water circulation / Pacific / Philippine Sea / Mariana Basin / Caroline Basin / Antarctic Bottom Water / glacial-interglacial |
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| Research Abstract |
The change of deep water circulation in the Northwest Pacific resulted from benthic foraminiferal faunal changes of two cores is summarized as followed :
In the West Mariana Basin, the frequency abundance of Nuttallides umbonifera, which is the representative species of the Antarctic Bottom Water (AABW), is mutually related with the oxygen isotope curve (カ180). It indicates the strong correlation the intensity of circulation with the ice volume. On the other hand, Pseodoparrella sp. has the opposite correlation with カ180. These suggest that the North Atlantic Deep Water (NADW) was active in the warm period such as interglacial and postglacial times, and the AABW was also activated by the intensified NADW,and carried to the West Mariana Basin through the Yap-Mariana junction. In the glacial time, the NADW stopped, and as the result the deep water circulation of the world was weakened. The West Mariana Basin was occupied by the peculiar deep water.
In the West Caroline Basin (KH92-1 3PC) , benthic foraminiferal fauna is represented by Epistominella exigua-Ioanella pusilla assemblage, and that dosen't have the major faunal change during the late Quaternary. E.exigua is relatively abundant in the glacial time. These faunal composition and trend of abundance in benthic foraminifers are also observed in the Ontong Jave Plateau, and this may be the general tendency in the Pacific Ocean. E.exigua is considered to be closely related with the Circum Polar Deep Water (CPDW) , and the glacial deep water has abundant E.exigua. These indicate that the origin of glacial deep water may be the antarctic circumpolar area.
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