Sedimentary Sequence,Provenance Analysis And Tectonic Evolution Of Late Mesozoic In Tianshifu Basin,Eastern Liaoning

Since the Mesozoic,the North China Craton has experienced huge lithospheric thinning,large-scale magmatic rock activities,and polymetallic mineralization.Various types of sedimentary basins have developed along with strong structural deformation.The eastern Liaoning region is located in the northeast of the Craton.Previous studies have focused on mineralogy,magmatic rock geochemistry and chronology,and structural deformation.However,the research on sporadic small Mesozoic basins in central Liaodong is relatively weak.Filling records as a direct response to tectonic activities has become an excellent window for studying the structural evolution of the area.In this paper,the Master Tian Basin in central Liaodong is selected as the main research object,which is composed of closely adjacent small basins such as Tianshifu,Jianchang,Saima and Aiyang.The basin is mainly filled with a set of Early Middle Jurassic volcanic-clastic rocks.Through field geological survey,measured typical stratigraphic profiles and combined regional data,the stratigraphic sequence of the Tianshifu Basin was studied,and sedimentary facies analysis was conducted.The Lower Jurassic Beimiao Formation and Changliangzi Formation are a set of volcanic rocks and conglomerates,respectively.The sedimentary strata composed of sandstone and shale with coal seam are volcanic eruption facies and alluvial fan-braided river-lake marsh facies;the Middle Jurassic is a regionally important coal-bearing stratum,including Zhuanshanzi Formation,Dabao Formation,three The ridges are all represented by multiple conglomerate,sandstone and shale sedimentary cycles with finer grain size and thinner layer thickness,which are alluvial fan-braided river-lake marsh facies;the Upper Jurassic Xiaodonggou Formation consists of conglomerate,The sandstone and shale are composed of sedimentary cycles with finer grain size and thinner layer thickness,which are alluvial fan-braided river-lake marsh facies.Based on the systematic statistics and measurement of the gravel composition and the shingled gravel in each group of the Middle Jurassic,the provenance analysis of the basin was carried out,and the gravel components in the Middle Jurassic conglomerate were mainly quartzite and quartz.The main sources of sandstone andsome granites and metamorphic rocks correspond to the Neoproterozoic(Yongning Formation,Diaoyutai Formation and Qiaotou Formation),paleoproterozoic granite,Liaohe Group and granite gneiss in the Neo-Archean.There is a local composition of carbonate rock gravel,which may come from the Early Paleozoic(Cambrian and Ordovician)or older strata.The paleocurrent research shows that the Middle Jurassic paleocurrent generally has a trend from east to west,and the source area of the basin's sediments may be located on the east side of the basin.Combined with the latest research and understanding,through previous work and combing the regional structure,the evolution history of the basin and the significance of regional structure are discussed.It is believed that the currently isolated small basins in the Tianshifu area may initially be connected,formed in an extruded tectonic setting,and experienced the emplacement destruction and separation of the Saima thrust nappe structure and the Guanmenshan rock mass around the early Cretaceous.The formation and reconstruction of the basin are unified with the regional structural evolution.