Study On Characteristics Of Stratum And Sedimentary Of Ordovician Sedimentary Strata In Wandian Area Of Facies West Yunnan

On the tectonic unit,the study area belongs to TeTi-Himalayan tectonic belt,existing between Gangwana and Laoya mainland.Also,in the east of the study area,there is a foreland basin called Lanping and Simao.It is Yangzi Island and the western margin of arc basin system of Changning melange belt in the middle of the study area.There is east edge of Baoshan block near the west of the study area.Additionally,it is China southwest plate kinematics,dynamics and plate margin orogenic and ideal research area of diagenesis and mineralization.The Ordovician strata of Wandianba area is a part of the west of Changning,Menglian belt,Baoshan,Zhenkang territory.The stratum continuous exposure,that place is a good carrier to study the Ordovician sedimentary environment.This article is in yunnan baoshan-longling area such as Wandianba,Mengtong street five regional geology and mineral resources survey,on the basis of field work,through collecting predecessors' research in this area and adjacent area data and lower devonian in this study area exposed to the Laojianshan Shidian Pupiao Renheqiao formation completed after the data analysis and research.Based on the predecessors' research results,the sedimentary facies of the Ordovician strata and the evolution of sedimentary environment in the Wandian area,mainly in the following:First,It is found that the Ordovician strata in the Wandianba area of western Yunnan are all clastic.Secondly,Based on the comprehensive study of the sedimentary facies of Ordovician strata in the Bayindian area: The sedimentary environment of the Laojianshan formation is the coastal facies,divided into intertidal zone and tidal zone;The sedimentary environment of the Shidian formation is shallow sea shelf,transitional zone;the sedimentary environment of the Pupiao formation is the shallow continental shelf,Shore outer shed;The sedimentary environment of the Renheqiao formation is the basin basin phase.Integrated Ordovician tectonic evolution analysis sedimentary environment evolution: Baoshan-Zhenkang block regional depression,Continuous deposition of Ordovician to Zhongzhi retaining system then area uplift.Late Cambrian mainly for a shallow sea-open platform phase silt-mud and carbonate deposition,then the late Cambrian late sea level began to decline,Early Ordovician late began a new round of transgression,and in the middle of the Renhe Bridge formation to reach the largest sea surface,finally into the stable deposition of high water level system tract.Finally,Only the Laojianshan formation preserved the sequence of retreat In the study area,the rest of the Shidian formation and Pupiao formation basically for the sea into the structure,so indicating that the study area of the Ordovician in addition to the Laojianshan formation experienced a complete seawater advance and retreat process,finally the Shidian Formation and the Pupiao Formation experienced only theexpansion of the early transgression of the Ordovician,the process of submerged at the edge of the ancient land and the stagnation.