Southwestern Yunnan Gengma Gute Si Phase Of Stratigraphic Sequence Recovery And Basin Evolution

Changning-Menglian zone always is hot area, where oversea and Chinese geologists study tectonic evolution of Paleozoic Tethys ocean. By the long term researching, study degree is evidently advanced because of new discovery and ideal is continuously brought forward. But there are many different ideals and comprehensions among different scholars and experts about tectonic feature, scale and evolutive history of sedimentary prototype basin in Changning-Menglian zone.The article reconstructs the stratigraphic sequence and series in middle segment of Changning-Menglian zone, by systemic researching data and study in 1:250,000 Lincang Sheet regional geological survey, especially to Permian Nanpihe formation holostratotype section. Nanpihe formation, established by previous researcher, has been decomposed as follows: Devonian Wenquan formation, Manxin formation, Carboniferous Pingzhang formation and Carboniferous-Permian Guangse formation in this article duo to a series revolutionary advance in lithostratigraphy, biostratigraohy and sedimentary petrography. The entity of different stage in Paleozoic Tethys evolution and sedimentary environment, period and relationship each other of each lithostratigraphy has been found out, the study accurately reconstructs stratigraphic sequence, basin pattern and tectonic setting of Paleozoic Tethys evolution stage in study area, by correlating and study lithostratigraphy, feature of sequence, biostratigraohy, chronostratigraphy, sedimentary environment and tectonic setting.In researching area, middle segment of Changning-Menglian basin can be divided into Genma passive continental margin (in west), middle ocean basin (Guangse area) and east continental margin. Author thinks that Paleozoic Tethys Ocean successively evolved based on the Proto-Tethys, Niujingshan-Ganlongtang ophiolite tectonic melange is a subduction zone duo to Paleozoic Tethys Ocean closed in Indo-China stage in west Yunnan Province, Changning-Menglian zone is main oceanic basin of Paleozoic Tethys Ocean. The revolution of Paleozoic Tethys Ocean in west Yunnan Province don't accord with Wilson cycle, it experienced successively expanding stage, rapidly expanding stage, forming oceanic basin stage, oceanic crust subduction stage and ocean-land translation stage.