Sedimentary Characteristics Study Of The Ziniquanzi Formation In The Southern Margin Of Junggar Basin

The Ziniquanzi formation is a rock-stratigraphic unit that belongs to the Southern Margin of Junggar Basin. With the direction of sedimentological theory and a systematic open field geological survey, selected 5 outcrops from west to east in the Southern Margin of Junggar Basin, which all have a fully-developed characteristics of Ziniquanzi formation. The names of these outcrops are Tuotuo,North Trench of Areqin, Ziniquanzi, Dong Trench and River of Hutubi, and made Ziniquanzi and Dong Trench outcrops as the emphasis of this paper for their thicker sedimentary and complete-development formation.On the basis of geological formation measurement, lithological description and sampling of above 5 outcrops, and integrated the open-field lithological characters, sedimentary phenomena, and structure analysis, this paper did research for various samples, including their granularity analysis, petrographic thin-section analysis, trace elements chemistry analysis, we found that: the sandstone of Ziniquanzi formation mainly is lithic graywacke with matrix supporting and calcite cement, and lithic arkosic wacke, which have a serious Metasomatism phenomenon. Sieve analysis showed the grain size accumulation curves mostly were linear model or three stage model. These models reflect ancient tubidity current deposit and traction current deposit. The main Lithologic characters in open field of Ziniquanzi formation are calcitic-argillaceous cementation conglomerate and reddish brown argillaceous siltstoue. There are some dispergated calcium nodules in certain layers. We can see sedimentary structure such as channel lag deposit, imbrication, gravel arrangement and so on. This paper discovered that there are two sedmentation types in the Southern Margin of Junggar Basin Ziniquanzi formation, i.e., alluvial fan deposit and braided river deposit facies, meanwhile identified 5 kinds of sedimentary subfacies and 8 species of sedimentary microfacies. During the depositional period of Ziniquanzi formation, paleoenvironment and paleoclimate analysis show that deposition occurred in a fresh water environment and climate were heat and drought. Calcium nodules layers are closely related to drouth period of Ziniquanzi formation.