沃川地向斜帯と飛騨変成帯

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The Ogecheon geosynclinal belt in the Korean Peninsula trends northeast to southwest, that is, along so-called Sinian direction. The belt is bounded by the Gyeonggi massif to the north and the Yeongnam massif to the south, both of which are composed of Precambrian rocks. The Ogcheon belt is divided into two parts; northeastern part consisting of unmetamorphosed Paleozoic sedimentary rocks (Josen and Pyeongnan Systems) and southwestern part of crystalline schists and phyllites which are called the Ogcheon System. The geologic age of the latter has not yet been solved. Some insist its Precambrian origin, while others suppose the Paleozoic (and partly Mesozic) origin. The recent discovery of Archaeocyatha of Cambrian age and Ordovician conodont from the Ogcheon System are important for age-consideration. One of supporting evidences for Precambrian age is the existence of tillite in the Hwanggangri Formation of the Ogcheon System. However, according to writers' observation at the type locality in Hwanggangri district it is not tillite but a kind of olistostromes; derived probably from norhteastern unmetamorphosed part. In Southwest Japan, the Hida metamorphic belt, Hida marginal tectonic belt and Mino-Tamba belt are distributed from north to south. HIROI (1981) divided the Hida metamorphic belt into the Precambrian Hida gneiss region of main mass and the late Paleozoic Unazuki zone of the outer marginal part. The Hida marginal tectonic zone is now assigned to as a serpentinite melange zone which involves middle to upper Paleozoic formatins and crystalline schists. After reviewing recent progress on the geology of South Korea and Southwest Japan, the writers attempted to reconstrut a paleogeographiy of these areas and discussed their mutual relation on the basis of acid igneous activities, tectonic movements and regional metamorphism, in reference to the paleomagnetic reconstruction by SASAJIMA (1981). It seems probable that the Ogcheon belt corresponds to the Unazuki and Hida marginal tectonic belts. The Yeongnam massif seems not to extend further eastward or be overthrusted by the Hida belt and the Hida marginal tectonic belt.
日本地質学会の論文

沃川地向斜帯と飛騨変成帯

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