AN ANALYSIS OF THE LATE TRLASSIC SEDIMENT AND BASIN OF WUCUN-YISHAN AREA IN ZHONGDIAN, YUNNAN

The Late Triassic strata are well developed in Wucun-Yishan area of Zhongdian. A complete sedimentary basin was formed between the margin of Zhongza Massif and Ganzi-Litang connection belt. The 3 parallel controlling faults of zhongdian, Geza and Militang divide this basin into the Wucun Delta of platform margin of Zhongza Microcontinent, the Hagong fault sag back-arc, the Shudu volcanic flysch basin and the Niru forearc slope(basin) from west to the east. The various distinctive sediments are deposited in these 4 structural facies regions, which have different structures of basic stratigraphic sequence, different biological assemblages and sedimetary facies characteristics and show the basin experienced 2 periodic depression-rising-depression-rising evolution processes.