| Wibei area is located in the south of Ordos basin,where different tectonicunits converge.It has undergone multi-stage tectonic activities and intensepost-reformation in the Mesozoic and the Cenozoic,which caused its structuralcharacteristics complica-ted and the Mesozoic strata denudated incompletely orcompletely.Directing by the principle of “overall,dynamic,comprehensive”,differentiateof stru-ctural unit,differentiate structural phase and analysis of structural characteristics.Furth-ermore,Meso-Cenozoic structural evolution and post-reformationin Weibei area are di-scussed.Based on previous researeh,the region showed only tectonic uplift in IndoChines-e epoeh,and the degree of tectonic deformation was relatively weak.Yanshan epoch was the main period of the tectonic deformation in Southern Ordos region,the region of interest not only inherited and strengthen the tectonic features of Indo-Chinese movement,and formed relatively eomplete foldedthrust fault.The region was in the str-ike-slip and extensional tectonic setting in Himalayan epoeh,formed the half and fau-lted Weihe basin,which was 1imitedby the normal fault.This paper systemically neatened and researched the gravity and magnetimeasure-ment data in study area.It used this data and combined with drilling,geology,electric-al and seismic results in the study area.The results showedthat gravity and magneti--c field with the basic features-boundaries by Chengcheng-Huangling and Binxian-Ch unhua,itdivided into the west,central andeast.According to significant differences onno-rth-south and east-west,Weibei uplift can be divided into 6 tectonic units,such as Yijun-Huanglong rampzone,Tuqiao-Zhaojin fault fold belt,Bincounty-Lingtai fold belt,Linyou-Yongshou fold belt,Yao county-Cheng cheng fault,fold belt,Heyang-Chengchenf ault-uplift belt.According to tructural sequences,deformation characteristics,stratigraphic contact relations and the data of fission track,after the Mesozoie and Cenozoicin Weibei area can be divided into there exist periods of tectonic uplifts,theyoccurred in earl Creta-ceous,late Cretaceous and Eocene to Oligocene.Combined with the study of stratigra-phic characteristics,sedimentary features andtectonic deformation,it wassuggested that Weibei uplift had experienced asignificant late reformation,which constituted the main part of the Ordos basin,and generally accepted deposition before the end of early Cr-etaceous.The tectonic uplift time of Weibei uplift can be divided into the overall uplift stage inlate Cretaceous and fault block tilted stage after Eocene to Oligocene.In the end,aceording to structural characteristics,sedimentary characteristies,estimat-eion of erosion thickness,development process of Weibei uplift,settlement charaeterist-ics of Weibei basin,and regional tectonic setting,the structural evolution and reformat-ion of Weibei area in Meso-Cenozoic are discussed preliminary.Its tectonic evolutio-n controlled by the Mesozoic and Cenozoic uplift of Qinling Orogenic belt and Cenozoic rifting of Weihe graben. |
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