Study On High-resolution Sequence Stratigraphy Of The Permian In The South And East Margin Of The Junggar Basin

This paper is based on the project of field geological investigation and sedimentary characteristics research of Permian-Jurassic in the south and east margin of Junggar Basin. Combined with previous stratigraphic and sedimentary data, this paper studies the Permian sedimentary characteristics and its geotectonic implications in the area through field outcrop section measurement and indoor data analysis.The main contents of the dissertation are as follows:1. Through the in-depth study of four measured stratigraphic section, the complete Permian stratigraphic sequence in the southern and eastern margin of Junggar Basin is established.2. According to the identification results of the rugose corals, fusulinids fossil, it is believed that Shirenzigou formation in the southern margin of Junggar Basin should belong to late Carboniferous epoch instead of early Permian.3. Through analysis of rock types, sedimentary structure and fossiliferous characteristic, this paper categorized the Permian in southern and east margin of Junggar Basin into three major types, namely the common developed braided fluvial facies, braided river delta facies and lake facies. and also the terrigenous detrital shallow coastal facies only found in lower permian series on south margin of Junggar Basin.4. Different level sequence identification marks have been established according to the study of outcrop high-resolution sequence stratigraphy of Permian in south and east margin of Junggar Basin. All the sections have been divided into short-term base-level cycle( the fifth sequence), intermediate-term stratigraphic cycle,( the forth sequence), long-term datum plane cycles( the third sequence). Permian in south margin of Junggar Basin has been divided into 7 third sequence, and Permian in east margin of Junggar Basin has been divided into 2 third sequence.5. Comprehensive stratigraphic frame and depositional framework of Permian in southern and east margin of Junggar Basin have been formed through section comparison. Combined with previous documents, 3 sedimentary paleogcographic maps were compiled using epoch as a unit.6. Comprehensive research of stratum and sedimentary characteristics of Permian in southern and east margin of the basin. It is believed that there are evident differences between the deposition history in south and east area. Firstly, the start time of uplift in sides of mountain are different, east is a residual basins in early Permian, in middle Permian the seawater completely out and evolved into depressive basin, and develops thick layer oil shale, indicating that Bogda Mountains uplift has not yet started at this time; Karameh mountain, on the northeastern of the Junggar Basin, has already bagun uplift since the early Permian, which caused the lack of early Permian strata on eastern margin of the basin and extensive development of coarse clastic sediments of post-brained river-brained river delta phase. Secondly, mountain uplift rhythm between the southern and eastern margin in Permian is different, the differences of mountain uplift history of the evolution between basin south of Bogda Mountains and north of the Karameh mountain are basic reasons to cause the differences of filling succession, lithology, sedimentary thickness on both sides of sedimentary basin in Permian.