On the geological Relation of Japan to Indochina, Kwansi and Kwantung with special reference to the southwestern Wing of the Akiyoshi orogenic Zone

Abstract

A critical review is presented here on the geology of Indochina and adjacent territories of South China on the basis of Fromaget's work, 1941, and many other papers mostly by Chinese geologists.
1) It is suggested that this part of the Chichibu geosyncline was probably brought to existence by the fragmentation of the Microurkraton on the southeastern side of the Cambrian Yangtze basin into the Indosinia and the Reinan-Fukien mass before the Ordovician period.
2) A series of the crustal movements accompanied by the pre-Uralian plutonism through which the lateral sides of the part was disturbed and consolidated, is called here the Kwansi orogenic cycle, in the honour of Dr. Ting's Kwansi disturbance which was paroxys mal in the cycle.
3) It is noteworthy that the intrageosynclinal volcanism migrated from Northeast Japan in the Carboniferous and older to Indochina in the Permo-Triassic period.
4) The early Triassic or possibly older embryonic folds developed in the middle and late Triassic periods into the Akiyoshi orogenic zone which was a uniaxial anticlinorium in Japan, but in west Tonkin triaxial Bruchflaten to which the Nappe of the R. Noire and basic intrusives of Thanh hoa at its possible Wurzel are added. The Schollenüberschiebung of Northeast Tonkin on Southeast Tonkin along the Lansong tectonic line is a remarkable feature in East Tonkin.
5) A few comments are given on the age of the mouvements majeurs by Jacob, and it is noted that it is possible to be a little older than Noric.
6) The early and late Jurassic ingressions and later historical 'events are briefly outlined.