白亜系の国際対比の今後の発展に向けて

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Recent works of restoration on the Cretaceous ocean-surface current direction and temperature distribution, atmospheric circulation, hurricane pathways, storm depositional system, rainfall patterns, etc. are reviewed. The characteristic features of the Japanese Cretaceous excluding that of the Hokkaido area are mentioned: non-marine sediments of fluviatile, lacustrine, and brackish-water environments are frequently interfingered with marine equivalents which involve index species of ammonites and other groups, so that biostratigraphic works on the Japanese Cretaceous play an important role in the interregional correlation between the European standard and the continental deposits in Eastern Asia. The necessity of the geological considerations on the correlated areas, e.g. the occurrence of the geologic bodies in the framework, should be emphasized especially on the interregional correlation in mobile belts. The Lower Cretaceous faunas in Japan were predominantly of tropical or subtropical tethyan elements. During Hauterivian (?) and Barremian times, however, there was boreal influence in some areas. The distribution of the boreal or subboreal ammonites in these times can be explained by the paleo-current directions, through these away across a part of Siberia, after the paleogeographic consideration. In the late Cretaceous the circum north Pacific lands had been connected in most times, so that the close affinity of the dinosaur fauna in the East Asia with that in the North America is observed, while some discrete ammonite faunas in the circum north Pacific sea are recognized. According to the biostratigraphic consideration, in the early Cretaceous time northeast Japan probably was somewhat southerly located or was confronted with more northerly detouring warm current, while southwest Japan was more northerly situated as a part of the Asiatic continental margin.
日本地質学会の論文
1985-03-30

白亜系の国際対比の今後の発展に向けて

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