South Kitakami Region: An allochthonous terrane in Japan

要旨

The pre‐Cretaceous geology of the Japanese Islands may be interpreted as an accretion complex in which many terranes of several origins are juxtaposed and a number of allochthonous blocks are involved. The South Kitakami and Abukuma regions of northeast Japan, and probably also Silurian and Devonian blocks in the Kurosegawa fault zone and the border fault zone of the Hida metamorphic terrane, are the allochthonous blocks. The stratigraphic sequence and paleobiofacies of the regions are similar to each other, and their lithologic characters are of continental affinity, but, however, are quite different from those of the other terranes having oceanic characters. The South Kitakami and Abukuma regions have been fragments of a lost continent, less remotely situated to Gondwana during the middle Paleozoic, and may have drifted and incorporated with the other part of the Japanese Islands before late Mesozoic to early Tertiary igneous activity.

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