Stratigraphic Classification And Correlation Of Nanhua System In Sichuan Basin And Its Surrounding Areas

This article classified and correlated the stratigraphic of Nanhua System inSichuan basin and its surrounding areas by theoretical guidance of high resolutionsequence stratigraphy and measuring geological section, analyzed of seismic dataand drilling data, geological logging, laboratory experiments. the outcome ofprevious studies we get the following main results:The study area can be divided into three subarea by characters of depositionand Lithology combination: Kangdian subarea, Qinling-Dabie Mountainssubareathe, Hunan-Chongqin-Guizhou Subarea. Kangdian subarea is the product ofbasin deposition, with the thickest part of4000-5000m.It developed overflowfacies,basalt-dacite and volcaniclastic rock； Qinling-Dabie Mountains subareadeposited river-ice lake and glacial-lake tillite and A small amount of volcanicclastic rock. Hunan-Chongqin-Guizhou Subarea developed shallow-deep water bayor lagoon deposits with black carbonaceous manganese killas. Nanhua system isdivided into two medium-term cycles, MSC1(from Liantuo to Datangpo Formation)and MSC2(from Nantuo to Doushantuo Formation)and Doushantuo Formationcan be used for regional stratigraphic correlation. On this basis, it analyzed thelithology of strata and correlated each formations.Based on the further study,it isbelieved that the sedimentary environment of the Liantuo formation belongs tolacustrine—fluvial system, and Datangpo formation belongs to deep-waterreducing environment,additionally, the set of coarse-grained rocks from Guchengand Nantuo Formations were deposited in continental glacial environment. Andthis paper discussed the features of deposition and tectonic evolution: Yangtzelandmass separated from Huaxia continental between the period of earlyproterozoic to late, and ancient Huanan ocean had been forming. Jinning-Sibaomovement made the ancient Huanan ocean begin to close between the period oflate proterozoic to early neoproterozoic. The neoproterozoic rift basin of southChina began to develop from the end of the early neoproterozoic.