Characteristics Of Structural Deformation And Mechanisms For Intracontinental Deformation Of Northern Sichuan Basin

Micangshan and Dabashan thrust belt was developed in the northern Sichuan basin which was influenced by the extrusion from north to south driving by Qinling Orogenic belt,and there developed several detachment in the studing area which makes the deformation even more complicated,Therefore,study on the geometry and kinematics and tectonic evolution around the Micangshan and Dabashan thrust belt is significant to the intracontinental orogenesis and oil-gas exploration in the foreland thrust belt.For the research of geometry and kinematics,we use outcrop data,seismic profile combined with fault related fold theory to abtain the deformation geometry,by using axial surface analysis to all faults which developed in the Micangshan and Dabashan thrust belt,finally,recover the tectonic evolution of he Micangshan and Dabashan thrust belt respectively,by using the structural balance principle.We discoverd all the deformation time which recorded by Micangshan and Dabashan thrust belt using unconformity,Magnetic stratigraphy,growth strata and fission track annealing,then combined with the deformation feature which was analysis before,the tectonic evolution of the Norhern Sichuan Basin was abtained.Although the Micangshan and Dabashan thrust belt all influenced by the Qinling orogenic belt,there is much defference in deformation feature.Micangshan thrust belt is characterized as multi-detachment which influenced by detachment which developed in the Sinian and Triassic Jialingjiang Formation,structure wedges are developed in the deep,duplex was developed in the mid,and because of the Jialingjiang Formation detachment,monocline was developed in the shallow.The Dabashan thrust belt was divided into northern and southern which boundaried by Zhenba fault,thrust nappe deformed at the northern Dabashan thrust belt which close to the Qinling Orogenic belt.And the southern Dabashan thrust belt characeterized as multi-detachmen deformation which is similar to the Micangshan Thrust belt,but because of the exist of the Siluran detachment,two sets of duplex was developed in the southern Dabashan thrust belt.By doing research of kinematics feature around Micangshan and Dabashan thrust belt,all fault were collected by the detachment,and the displacement was transfered from deep to shallow,and from mountain to basin.By doing some Chronological analysis around Micangshan and Dabashan thrust belt,Combined with the study of geometry-kinematics around Micangshan and Dabashan thrust belt,the tectonic evolution of northern Sichuan basin was obtained.The northern Sichuan basin was experienced six stages:before the Leikoupo deformation deposited,the structre was relatively stable,characterized as marine deposit,mid-late Triassic,the oceanic crust closed because of the subduction of the plates,continental sedimentary deposited,the oceanic crust totally closed,continent-continent collision happened,the norhern of north Dabashan thrust began to deformed,the late Early Cretaceous-early Late Cretaceous,because of continuous extrusion caused by Qinling Orogenic belt,the north Dabashan thrust belt deformed completely,Zhenba fault began to rupture,and the duplex deformed in the Micangshan thrust belt,Early Paleocene(60Ma),large-scale uplift was happened in Micangshan thrust belt which characterized by the wedge deformed,and the south Dabashan thrust belt began to deformed southward extending,about 40-12Ma,by the influenced of Tibet Plateau uplift,south Dabashan thrust belt deformed southward extending continueously.