SEDIMENTARY FEATURES AND STRATIGRAPHICAL CORRELATION OF LATE TRIASSIC STRATA IN THE EAST OF NORTHERN QIANGTANG BASIN DEPRESSION

The Late Triassic Tumengela, Jiezha and Batang groups in the Northern Qiangtang area are distributed in the south and north sides of Geladandong Mountain, between the southern part of Jinshajiang suture belt and front uplift, in a strap trending northwest. Based on the 1/250000 regional geology survey, the biota appearance, lithologic assemblage and sedimentary environments are analyzed. The three groups can be well correlated with similar characteristics. The groups were formed in shallow water in the southern part of the area and deep water in north. In the south part next to the central uplift of Qiangtang basin, the strata are dominated by sandstone for the abundant terrigenous supply;while at Quemocuo in the north, because of insufficient terrigenous supply and rich fossils such as bivalve and ammonites, the groups are dominated by mudstone and limestone, forming in shelf sea. To the north next to Jinshajiang suture belt, volcanic activities were frequent. In fact, they are sediments in different tectonic positions within a same tectonic unit during a same geological time.