下扬子区中晚元古界沉积建造特征、构造运动及其演化

下扬子区中上元古界,可以分为四个构造层次.中元古界早期构造层,为一套巨厚的地槽型火山碎屑岩及砂泥质复理石建造,形成于1900-1400Ma;中元古界晚期构造层,为滨海——浅海——半深海砂泥质复理石建造.形成于1400-1000Ma;晚元古界早期构造层,为山前凹地或山间盆地磨拉石堆积,形成于1000-800Ma;晚元古界晚期(震旦系)构造层,则为砂泥质、硅质、碳酸盐岩夹冰碛砾岩建造,形成于800-600Ma.这些构造层之间不同形式的接触关系都代表着不同性质的构造运动,九岭群和修水间的修水运动,形成扬子准地台的雏型;上溪群和历口群邓家组间的祁门运动是形成扬子准地台的主褶皱幕;历口群铺岭组和震且系间的休宁运动,只使地壳抬升.这些不同性质的构造运动,也是推动地质历史演化的主要动力.

THE FEATURES OF SEDIMENTARY FORMATION, TECTONIZATION AND EVOLUTION OF LOWER YANGTZE AREA DURING MIDDLE-LATE PROTEROZOIC

The middle-upper Proterozoic of lower Yangtze area can be divided into four structural layers: the first one, formed at early stage of middel Proterozoic (1900-1400Ma), was characterized by a suit of geosyncline pyroclastic rocks and flysch formation; the second one, formed at later stage of middle-Proterozoic (1400-1000Ma), having taken sand and pelitic flysch formation as the key, showing that the sedimentary environment was from littoral facies to neritic facics to bathyal facies; the third one, formed at early stage of later-Proterozoic (1000-800Ma), was belong to molasse formation accumulated in foredeep or intermountain basin; the last one, Sinian structural layer was formed at later stage of later-Proterozoic (800-600Ma) and was consisted of sand, pelitic and silicious carbonatite and moraine-breccia.The contact relationship between above mentioned structural layers represented differ-ent tectonization, such as, Xiushui movement between Jiuling Group and Xiushui Group made Yangtze paraplatform form embryo. Main folding phase of Yangtze paraplatform was formed by Qimen orogeny which existed between Shangxi Group and Dengjia Formation of Likou group and Sinian caused the crust uplift. These different tectonization are main motive force of geological historical evolution.