The Characteristics Of The Caledonian Basin Prototype And Later Reformation In The Southern Margin Of Ordos

The southern margin of Ordos is located between the Ordos platform and the ancient Qinling ocean in the early Paleozoic.It is a transitional sedimentary structural transition zone,widely distributed in the lower Paleozoic with large sedimentary thickness and various sedimentary types.Based on the study of the stratigraphic structure and structural characteristics of the early Paleozoic in the block,this paper will discuss the basin prototype from Cambrian to Ordovician and the later basin structure.In order to reveal the Caledonian structural changes in the south of Ordos Basin and to discuss its later reconstruction features,the paper makes a detailed observation of the structural and sedimentary phenomena of the outcrops in the Caledonian period in the south of Ordos Basin,and interprets a large number of seismic data in the covering area,so as to carry out research on the Cambrian structural characteristics and sedimentation in the south of Ordos Basin:The results show that the basin properties have changed greatly in Caledonian period in the southern margin of Ordos.The Cambrian Early Ordovician is a passive margin stable cratonic epicontinental basin,mainly developed as carbonate platform facies deposition.The Majiagou period in Ordovician is mainly located in the margin extensional back arc rift trough basin,with marginal slope on the outer side and Limited sea or gypsum salt on the inner side Lake environment;Late Ordovician may be controlled by the back arc basin related active continental margin collision back arc residual marginal sea basin,mainly developed continental margin rift trough deposition.In the late stage of basin evolution,from the late Caledonian to the Early Hercynian,the lower Paleozoic in the southern margin of Ordos suffered thrusting and compression,forming folds,then weathering and denudation,forming weathering crust on the top of Ordovician;from the Indosinian to the early Yanshanian,the southern margin of Ordos was in the stage of deep burial and reconstruction;in the late Yanshanian,the study area suffered thrusting and compression again,which was mainly strong During the Himalayan period,with the formation of the Weihe graben,the Weibei uplift was uplifted and the southern margin of the basin was uplifted and eroded,so that the lower Paleozoic was widely distributed along the outcrop of the southern margin of the Weibei uplift.