Research On The Upper Triassic And Its Sedimentary Characteristics On The South And East Margins Of The Junggar Basin

The upper Triassic stratum of the Junggar Basin’s eastern and southern margin is known as Xiao Quangou group. According to the research of sections in the eastern and southern margin of the Junggar Basin, we observed the upper Triassic rock types, sedimentary structures and combinations of features, analyzed the type of depositional facies, subfacies and microfacies, and then concluded the characteristics of depositional environment of the Junggar Basin’s eastern and southern margin in late Triassic.The upper Triassic sections in the eastern and southern margin of the Junggar Basin is well-developed, have abundant depositional marks and obviously characteristics of depositional facies. The sedimentary environment of these sections is continental. The main typies of depositional facies are fluvial facies, delta facies and lacustrine facies. Majority of fluvial facies in study area are braided fluvial delta facies and meandering fluvial delta facies. Delta facies formed by flow into lake are braided river delta and meandering river delta. Moreover, most of the depositional facies in the southern margin of Junggar Basin are meandering river and meandering fluvial delta, and in the eastern margin, the depositional facies are braided river and braided river delta.In our research of the Junggar Basin’s eastern and southern margin, we learned the development, sedimentary characteristics and sequence stratigraphy of upper Triassic strata. Furthermore, we can reshape the geography of ancient sedimentary late Triassic eastern Junggar Basin: in the Junggar Basin’s southern, Bogda Mountains uplift in lower rate and terrain in these part is flatten, then meandering river and meandering fluvial delta facies of Huang Shanjie and Hao Jiagou groups are formed in this area. In the same time, Karamori Mountain uplift rapidly, and formed unconformable bed and "agate conglomerate" deposition of braided fluvial facies in the bottom of Hao Jiagou group. Therefore, the terrain in Junggar Basin’s eastern part is steep in the north and flat in the south.