Microfacies Of Carbonate Rocks And Organic Evolution For Near The Permian-Triassic Boundary In Yibin Area

The core and petrology characteristics(especially the biometric) are carefully researched with the Zk1501 drilling of Xianfeng mining district in Yibin area of Sichuan province, and petrologic features, carbonate microfacies type and vertical change of biological combination are explored of the basis of near Permian- Triassic boundary in the south of Sichuan province in this article. Analyzed the relationship of biological changes with to restore the sedimentary characteristics on Yangtze carbonate rocks in central region and the evidence of the deposition and biological events happened in the Permian to the Triassic period of transition has been defined from the perspective of sedimentary petrology and biostratigraphy.Seven kinds of carbonate sedimentary facies belt and thirteen kinds of carbonate microfacies are identified on the stratum of near Permian- Triassic boundary in the south of Sichuan province, mainly by the big shell foraminifera algal dust grain limestone, raw crumb grain of marl, mud limestone, pyritic shell grain of marl, Microbial calcium rock, born sparry grain limestone, etc.The true is discovered that different microfacies types constituted the sedimentary facies belt in research area, it reflects process that the sedimentary-lagoon and swamps of the restricted platform from Permian evolve to parallel unconformity surface- platform in shallow water- gentle slope in the lagoonlagoon in the gentle slope of early Triassic.According to the core sequence and 21 slices after grinding out, the paper count 384 foraminifera and select 109 shell which is complete and easy to identify as the research object in it by polarized light microscope. And the foraminifera are identified with a total of 66 species, 10 families, 17 genera and 4 orders.The δ18O from layer 3 began to 9 in slowly rise, the beginning of the 10 layer, the δ18O began to more rapid rise, reflects the Early Triassic climate became dry and water salinity increases. The change accurately reflects the climate change from warm and humid to hot and dry process.By lithology and combination of biological characteristics, the paper discussed the Permian- Triassic stratigraphic boundary with regional and global comparative, which is located in the main with extinction.