Study On Microfacies And Sediment Environment Of Middle Permian Shenshan Formation In Zha Laite Area, Inner Mongolia Zhalaite

Zhalaite is located in North part of the central Daxinganling in inner Mongolia. Its geotectonic position is in the northeast of Halixi foldbelt at middle and late period, and in the north of the boundary between Siberian plate and Sino-Korean plate. Based on the stratigraphic geology,lithostratigraphy and biostratigraphy,in this article we mainly discussed the cross section of Shenshan formation of Tabenmaodu and Chaganchulu in Zhalaite, compared the Longjiang section, Wujiatun section, Xizhumuqinqi section, Erlianhaote section and Zhesi section, and comprehended lithofacies alteration and Sedimentary features in Siberian plate Boundary.Tabenmaodu section and Chaganchulu section was represented as the Shenshan formation section. According to abundant field work, and particular measurement, the lithology of Benmaodu section are mainly consist of limestone with sandstone, silt-sandstone, porphyritic tuff lava and andesite-porphyrite. The thickness is more than 850m。In the west section of east Tabenmaodu, zoolites are rich in the limestone formation, which can determine the geologic times and can be used to compare the stratum. Biogenic reef were well developed on the top. According to the research,the organic matter are founded in the zoolites, therefore oil reservoirs are well developed, in which oil and gas are generated and preserved. It can be a new aim for oil and gas exploration. In Chagenchulu formation, sandstone are developed in the lower section. The thickness are more than 500m. For the research, around this section we studied another section. Zoolites are rich in limestone, especially the well preserved multiseptata.According to the analysis of the two sections, combined with abundant of fossil data, based on"stratum guide of china and its instruction", we reasonably divided Shenshang formation into small sections. and exactly matched every period, which have never done before. We also set up a standard column of middle Permian formation in Zhalaite area, which can guide us to divide the distribution of Permian lithofacies papleogeography in east Inner Mongolia. From the data: amalgamation of Paleo-Asian Ocean between North China plate and Siberian plate occurred two times. During the amalgamation depression happened in Carbonic to Permian. According to the comparison between Shenshan formation and others Permian formation, with the method of Sedimentary facies, in Permian continental sea are appeared in the depression. Carbonate reservoirs of stable table type, active type rift reservoirs and continental fault basin reservoirs developed in this area. The sedimentary thickness of Xiwuzhumuqinqi formation and Damaoqizhesi formation is much larger than it of Shenshan formation in Zhalaite and Wujia formation in Keyouqi, therefore the ocean trough was closed from east to west.