地球科学

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In the south-western Japan, the neogenic geological provinces are divided into four; the Hokuriku, the Sanin, the Setouchi and the Nankai provinces. Of these provinces, the Hokuriku and the Sanin provinces have a marginal character of the geosynclinal basin, the Setouchi province having been formed in one stage of the development of the former provinces. The volcanisms in space and time are divided into as follows; 1.) The acid and a little alkaline (semi-alkaline) volcanism in the terrestrial condition before the formation of the Hokuriku and the Sanin sedimentary basins. (Cretaceous ? to the lowest Miocenc-F1 of the letter nomination.) 2.) The initial basic volcanism under the submarine conditions characterized by tholeiite at the first stage of depression in the Hokuriku and the Sanin sedimentary basin, (middle Miocene-F2 of the letter nomination.) 3.) The acid and intermediate volcanisms nearly contemporaneoous with the formation of the first Setouchi basin.-palaeogeographically in the age of the maximum transgression-(middle Miocene-F3 of the letter nomination.) 4.) The basic to acid volcanisms characterized by hypersthenic rock series contemporaneous with the upheaval of the inland area.-the formation of the Setouchi volcanic series-(upper Miocene-G of the letter nomination.) 5.) The final volcnism of alkaline and semi-alkaline character probaly corresponding to the warping of the crust. 6.) The Quaternary to Recent volcanisms a little rich in alkalies related to the north-southern trend of the geologic structure.-the formation of the Daisen Volcanic series- In correlation with the Cenozoic formations in the northeastern Japan, it is supposed that the differences in the geohistory between the northeastern Japan and the southwestern Japan become clear in the middle Miocene-G of the letter nomination-, judging from the processes of volcanisms and crustal movements.

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In Japan and seiner Umgebung sind zwei junge Orogene in Tatigkeit. Eines ist langs der Kette Marianen-Japan-Kamtschatka, and anderes fangs der Kette Formosa-Okinawa-Kyusyu. Die Arbeit enthalt kurze Zusammenfassung des Wissens urn diese Zonen. Abb. 1-2.: Geophysikalische Verhaltnisse. Abb. 3. Links: Linien gleiches Werts des θ=SiO2-47(Na2O+K2O)/Al2O3 (indessen SiO2 in Gewichts-% and die anderen in Molekular-%) aus den Analysen der Ergussgesteine. θ=20-30: schwach atlantischer Charakter θ=30-35: schwach pazifischer Charakter θ=35-40: stark pazifischer Charakter Rechts: Linien gleiches Werts der Tiefenlage des Bebenherds unter der Erdoberflache (nach K. WADATI, 1935) Abb. 4. Obere Kurve: Profil langs der Kammlinie der submarinen Schwellen und der japanischen Inseln. Untere Kurve: Profil langs der Bodenlinie der Tiefseegraben. Die Zonen sind auch durch jungtertiare geologische Ereignisse gekennzeichnet, die im anderen Artikel behandelt werden.

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