上部古生層に賦存する粘土層の地質学的意義並びにこれに関連する諸問題

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In the Fukuji district of the Hida massif, both Carboniferous and Permian deposits are well developed and are divided into two groups by IGO (1956-1957)^<7, 8)> : namely, the lower or Ichinotani group and the upper or Sorayama group. The Ichinotani group consists of fossiliferous limestone and intercalates several red clay beds ; Fusulinid fossils occur throughout. IGO recognized six fusulinid zones in the lime-stone, which in ascending order are ; Millerella-, Profusulinella-, Fusulinella-, Fusulina-, Triticites-, and Pseudoschwagerina-zones, and also that clay beds are (a) between the Profusulinella and Fusulinella zones, (b) within the Fusulinella zone, (c) between the Triticites and Pseudoschwagerina zones. These clay beds are lateritic materials (Terra rossa), and must be regarded as lateritized products of the underlying limestone. On the contrary, the Sorayama group (Parafusulina-Neoschwagerina zones?) consists of remarkable conglomerate (Osobudani conglomerate) and agglomeratic schalstein or volcanic conglomerate (Murakami conglomerate). In North China Cambro-Ordovician deposits are distributed widely in mountains everywhere, and the Upper Paleozoic formation (Carboniferous and Permian deposits) rests on it with paraunconformity to form important coal fields. The Cambro-Ordovician deposits are marine, consisting of thick layers of limestone and dolomite. But the Upper Paleozoic formations are terrigenous marine or terrigenous or inland deposits, and may be subdivided into five formations, which in ascedning order are, Pench-, Taiyuani-, Shansi-, Shihhotze-and Shiechienfeng formations. The Penchi and Taiyuan formations are terrigenous marine deposits, and the formations later than the Shansi formation appear to be terrigenous or inland facies. The Upper Paleozoic formation in South China distributes generally in the South of the Yantze River and is continued intermittently from the Lower Paleozoc formation and shows the development of marine facies. The sedimentary facies of the Upper Paleozoic formation in North China is strikingly different from those of South China. The Ore deposits in the Upper Paleozoic formation are coal, aluminous shale, hardclay, soft clay, iron ores and etc. The mode of occurrence of these deposits will be stated for the convenience to suppose the sedimentary environment. The aluminous shale comprise two layers, namely, "A" bed and "G" bed (of SAKAMOTO, 1924)^<20)> and the former occurs at the base of the Shihhotze formation, and the latter in the base of the Upper Paleozoic formation and iron ores are accompained with "G" bed, and are commonly known as iron ores of the Shansi type. Hard or soft clay (Kaolinite) beds occur in many different horizons from "A" bed and "G" bed of aluminous shale. Aluminous shale and the hard or soft clay beds are reworked lateritic materials in the Upper Paleozoic era in North China, and are the largest of all known ore beds of aluminous hydroxide and Kaolinite in the world. This is due to the fact that this region, in the Upper Paleozoic era, formed an extensive sedimentary basin of an epeirogenic type with the most gentle crustal movement in the world. Judging from the above mentioned criteria, the following shall be noticed. The sedimentary environment of the Ichinotani group in the Fukuji district, Hida massif, was not accompanied with orogenic movement, but with the nature of a gentle epeirogenic movement. Consequently, the reexamination of the meaning of the Chichibu or Honsyu geosyncline in the Upper Paleozoic era is an important subject for discussion of the origin of the Japanese Islands. The complete regression of the sea, which once widely covered all of North China, at the end of the Sakmarian is shown by the unconformity at the base of the Shansi formation. The unconformity dividing the marine formation and the terrigenous formation in North China has important meaning, and the author (1951)^<24)> gave name of "the Chiaotsuo movement" to the movement at that time. In South China, a distinct unconformity is seen between the Lungtan formation, yielding Gigantopteris nicotianaefolia and the Maokou limestone, yielding Neoschwagerina and Yabeina, and there was the age of volcanic activity and granite intrusion. J. S. Lee (1931)^<15)> called the orogenic movement at that time in South China "the Tungwu movement". The unconformity of the base of the Lungtan formation in South China is regarded as of the same age with the unconformity shown by "A" bed of aluminous shale in North China as already stated. In short, a remarkable change of sedimentary facies was brought by the Chiaotsuo epeirogenic movement, and a powerful disturbance occurred by the Tungwu orogenic movement during the Permian period in China. The same stratigraphical relation occurs also in the Japanese Permian deposits, and the effect of the crustal movements happened in China are wide. Looking over the Permian deposits in Japan as a whole, the sedimentary facies, as containing the Usuginu conglomerate in the Kitakami massif, the Osobudani conglomerate and volcanic conglomerate of the Sorayama group in the Fukuji district, Hida massif, and its corresponding conglomerate in many other places which transits from the Parafusulina zone to the Yabeina zone, became remarkably different since the time of the Chiaotsuo movement.
東北大学の論文
1960-05-05

著者

小貫義男
東北大学理学部地質学古生物学教室

上部古生層に賦存する粘土層の地質学的意義並びにこれに関連する諸問題

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