Continental Basins' Sedimentary Characteristics And Structural Control Of Wan Dian-Feng Qing Area In Western Yunnan Since Mesozoic

The area?Wandian-Mengtong-Fengqing?of research is located in the southern part of the“Sanjiang”tectonic zone,across the Baoshan-Zhenkang land parcel on the eastern of Gondwana,Changning-Menglian tectonic belt and the Yangtze block on the western of Laurasia,which is the ideal research site for studying of the kinematics and dynamics of the southwestern plate and the edge orogeny of the plate.In this paper,according to the data collected from the field of three regional geological and mineral resources survey in Longling area,Baoshan,Yunnan.Based on the theoretical study of the previous related regions,starting from the sediments of the basin,the stratigraphic and sedimentological theories of stratigraphy and sedimentology are applied to analyze the characteristics of stratigraphic deposition?J₂m,E₁mg,N₂m,Q?and sedimentary filling characteristics of continental basins in the study area since Mesozoic,restore the paleocurrent direction,discuss the temporal and spatial evolution law of the sedimentary basin.Based on the characteristics of sedimentary gravel composition,particle size,psephicity and separation,the source area direction,transport distance and source area of the sediments are studied.And the relationship between the sedimentary and regional tectonic evolution of continental basin in the study area since Mesozoic is discussed.The area?Wandian-Mengtong-Fengqing?of research began to accept continental deposits since Middle Jurassic.The shallow sea facies deposits and continental river deposits developed in the Mengga group?J₂m?of Wandian-Fengqing area,West Yunnan,confirmed that the sedimentary environment of this period has changed to the sea and land interactively.The Papaya River group?E₁mg?developed molasse formation and continental clasolite.The Mangbang group?N₂m?developed fluvial facies and lacustrine facies?containing pyroclast?clastic rock formation?N₂m?.The Quaternary?Q?sediments are mainly glacial deposits,alluvial deposits and residual sediments,and develop to the terraced and alluvial fan geomorphologic types.The uplift of the Nujiang River fault zone affected the regional structure and deposition since Middle Jurassic,the inner continental rift area on the west side of the Baoshan-Zhenkang block was the main source area.The uplift of the Lancang River fault zone on the east side affected the regional structure and deposition in Paleogene,and the object source was bidirectional.During the period of Jurassic-Quaternary,the geological tectonic evolution in the region can be summarized into five stages,namely continentization stage?J₂?,intracontinental orogenic stage?J3-K?,thrust and deformation stage?E-N1?,strike-slip and pull-apart stage?N₁-N₂?,plateau formation stage?N₂-Q?.In the Middle Jurassic period,the study area was deposited in the continental basin of the west of the mengtong fault zone,with the nature of volcanic fault basin.In the Paleo-Miocene,the study area was affected by the squeezing effect,forming the prototype of the modern mountain and developing the intermountain sedimentary basin.In Pliocene,the study area developed volcanic stacking fault basin.Since the Quaternary period,the research area has presented a basin-mountain coupling model of three mountains and two basins?Wandian basin and Mengtong basin?,there is also a strike-slip basin?Fengqing county and calley?.