北海道の中生界 : 層序・年代とその意義(<特集>日本の中・古生界研究の発展と現状)

概要

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Since the end of the 1970's, many new informations about stratigraphy and age of the Mesozoic in Hokkaido have been accumulated. These data are very important to examine the geologic history of Hokkaido. This paper referred to stratigraphy, age, facies, correlation and tectonic setting of the Mesozoic in Hokkaido, as summarized below. i) "Meso-Paleozoic systems" of the Oshima-Rebun Belt are melange formed during the late Jurassic. ii) The Cretaceous granites and volcanogenic rocks in the Oshima-Rebun Belt are considered to represent the products of an active island arc. iii) The Cretaceous tectonic setting of the Sorachi-Yezo Belt was a residual forearc basin (Yezo Group) floored by a trapped oceanic crust (a greater part of the Sorachi Group). The trap of the oceanic crust is probably caused by a jump of plate boundary that took place toward the earliest Cretaceous from the Oshima-Rebun Belt to the western margin of the Hidaka Belt, iv) The Hidaka Supergroup which is correlative with the upper part of the Sorachi Group and Yezo Group is mainly melange presumably partially resulting from westward and partially from eastward subductions. v) The Yubetsu, Saroma and Nakanogawa Groups which are correlative with the upper part of the Yezo Group are forearc deposits connected with eastward subduction.
地学団体研究会の論文
1985-01-25