Study On Carbonate Microfacies And Sedimentary Environment Of Upper Jurassic Tukari Formation In Doma Area Of Tibet

The paper relies on 1: 50000 regional geological mapping project.The paper studies the carbonate microfacies of the Upper Jurassic Tuoakai Formation in Duma Township,Shuanghu County,Tibet.The lithology of this strata is a set of carbonate rocks with a small amount of clastic rocks.The study of its sedimentary facies and microfacies is of great significance for the correct understanding of paleogeographic evolution of Bannu Ocean.By collecting field outcrop section data and regional geological data,combined with observation and analysis of rock thin section,and adopting the method of microfacies analysis,the microfacies types and sedimentary environments of carbonate rocks of the Upper Jurassic Tukari formation in Doma Township,Shuanghu county,Tibet were studied,and eight types of carbonate microfacies were classified.That is bioclastic micrite microfacies(MF-1),conglomeratic crumbs micrite microfacies(MF-2),micritic calcirudite microfacies(MF-3),sparry calcirudite microfacies(MF-4),sparry calcarenite microfacies(MF-5),bioclastic sparry calcarenite microfacies(MF-6),sparry oolitic limestone microfacies(MF-7),andbioclastic oncolite(MF-8)and Colluvial rocks(MF-9);on this basis,according to the rock characteristics and microfacies combination types,the Tukari formation is a typical carbonate platform facies,it can be divided into 4 sedimentary subfacies,that is carbonate restricted platform,open platform,platform edge shallow,and platform foreslope.On the basis of the phase sequence,water cycle and the significance of the tectonic evolution of this set of carbonate rocks are discussed.