三江褶皱系主印支褶皱幕的再认识

本文根据三江地区三叠纪地层时代,划分与对比,接触关系,沉积建造,构造变形特征,岩浆侵入和火山喷发活动等,进行了详细的分析讨论,认为三江褶皱系属印支期褶皱,其主褶皱幕发生在中三叠世与晚三叠世卡尼期之间。

RECONSIDERATION OF THE MAIN INDOSINIAN FOLDING PHASE OF THE SHANJIANG FOLD SYSTEM

The Shanjiang fold system ia a part of the Indosinian geosynclinal fold region of the Tethys-Himalaya Tectonic Domain in southwestern China,which was determined to be generated by the lndosinian folding movement firstly by Ren Jishun et al. （1964. 1966）. who pointed out that the main folding phase is represented by unconformities between the Carnian and Norian of the Late Triassic. Authors’s recent surveys show that the main folding phase is mainly marked by unconformities between the terminal Middle Triassic and the Late Triassic Carnian. The most pronounced localities of the unconformities are in the Jinshan River and Lancang River eugeosynclinal zones. Hore the Lower-Middle Triassic is composed of a considerable thickness of arenaceous-pelitic and volcanic- sedimentary flysches,which are characterized by repeated rhythms,complex structures and generally undergoing metamorphism. The volcanic rocks exhibit the features of oceanic island-arc rocks,which,together with syntectonic igneous rocks,constitute an Indosinian tectono-magmatic belt that extends discontinuously for 1000 km. However,Upper Triassic Carnian and post-Carnian strata are all represented by sandstones,shales and carbonate rocks,showing the nature of a stable platform cover. Angular unconformities beween the Middle and Upper Triassic are found in some places.