The Structures Of The West Margin Of Dengzhangzi Basin In Southern Lingyuan,Western Liaoning Province

Yanshan orogenic belt region on the northern margin of the North China Craton started the continental intraplate tectonic deformation since the late Paleozoic era.Through the geological mapping and tectonic style of the western marginal structural belt of the Dengzhangzi Basin in the south of Lingyuan,western Liaoning,the author determined the deformation sequence and superposition transformation relationship of the two phases of fault and folds.A model that can explain the evolution of the tectonic belt in the area is proposed,which helps building the overall pattern and dynamic mechanism of the deformation in the Yanshan orogenic belt.The Lingyuan area in the east of the Yanshan orogenic belt is a relatively complex area of the Yanshan structural belt.The structure of the western margin of the Dengzhangzi Basin in the south is a representative area in the complex structure of the area.There are two different tectonic styles in the north and south,each retaining two structural periods..There are two stages of tectonic deformation in the north:(1)the near-west-westward extrusion developed along the Weishuangzhuang Formation in the Jixian County,and the west-to-east flat-slope-flat thrusting tectonics;(2)In the second phase,from the west to the east,there was a reverse fault in the left-lateral strike slip.The first stage of the thrust nappe structure system was modified to make the original pattern fold,and the east side of the fault plateau in the lower strata.The Jixian County was reversed from the Hongshuizhuang Formation,the Tieling Formation,the Qingbaikou Formation Xiamaling Formation,the Jingeryu Formation,and the Cambrian strata.In the overlying strata of the eastern fault,the Jingxian Tieling Formation,the Qingbaikou Siamaling Formation and the Jingeryu Formation,and the Cambrian strata diverted eastward due to the second-stage transformation.There are also two stages of tectonic deformation in the north:(1)the west-westward extrusion of the Xiakaling Formation along the Qingbaikou Formation and the westward-to-eastward thrusting of the flat-slope-flat thrusting tectonics;(2)In the second phase,from the west to the east,there was a reverse fault along the left-lateral strike slip,and the first stage of the thrust nappe system was modified to make the original pattern wrinkle,and the eastern thrust of the original thrust nappe structure.the Wumishan,Tieling formations,Cambrian and Ordovician stratas are dipping eastward,resulting in a unique ?new covers old? thrust style.The time of occurrence of the two-phase structure is based on the U-Pb dating results of the pyroxene andesite in the Shuiquangou Formation and in the Dengbianzi west marginal structure at the same time.The dating results of the Andesites in the Laoshan Formation over the tectonic belt in the later period.The time that the structure takes place can be roughly limited to 230.4±3.1Ma?160±6Ma,which is a certain time range from the Late Triassic to the Middle Jurassic.