1988 Fiscal Year Final Research Report Summary
Study of latest Cretaceous Radiolarian Assemblage and the faunal change in northern Japan
| Project/Area Number |
62540592
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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 | Hokkaido University |
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Principal Investigator |
IWATA Keiji Faculty of Science, Hokkaido University, 理学部, 助手 (60002226)
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| Co-Investigator(Kenkyū-buntansha) |
JOUR Fac.Sci , (KATO,Yukihir)
JOUR Fac.Sci , (IWATA,Keiji.)
WATANABE Yasushi Geological Survey of Japan, Sapporo Branch, 研究員 (90358383)
NAKAMURA Koji Faculty of Science, Hokkaido University, 理学部, 教授 (40000822)
EARTH Scienc 41, 教授
UOZUMI Satoru Faculty of Science, Hokkaido University (20000763)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Hakobuchi Group / Hidaka Supergroup / Yubetsu Group / Nemuro Group / Upper Cretaceous / Radiolarian Biostrtigraphy / 化石群集変遷 |
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| Research Abstract |
The authors investigated especially the radiolarian biostratigraphy of the Hakobuchi Group of Nakatonbetsu region in the northern Hokkaido. As a result, two radiolarian zonations of the latest Cretaceous System - Protoxiphotractus perplexus zone (early - middle Campanian) and Chlathrocyclas gravis zone (late Campanian - early Maastrichtian) were established. The former zone corresponds to Amphipyndax enesseffi zone and the latter corresponds to Amphipyndax tylotus zone of the Upper Cretaceous in the Tropical Pacific Oceans and the southwestern Japan. The fanual difference between the Hakobuchi Group and the Hidaka Supergroup was distinguished. Namely, amphipyndax enesseffi and A. tylotus assemblage were found in the Hidaka Supergroup, but these assemblages were completely absent in the Hakobuchi Group. Faunal difference among the Hakobuchi Group, Hidaka Supergroup, and the Upper Cretaceous Systems in the southwestern Japan suggests differences of paleogeography and accumulation sites of sediments9 Abrupt decline of late Cretaceous radiolarians was detected in the Hakobuchi Group, but some genera of Cretaceous type persist into the early Paleocene epoch.
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