Tectonic Characteristics Of Wulungu Depression,North Margin Of Junggar Basin And Its Relationship With Hydrocarbon

Orogenic activity of Central Asian Orogenic Belts(CAOB)had ended by the end of the late Paleozoic,signaling the intra-plate evolution stage,a lot of evidence showed CAOB experienced tectonic deformation during Mesozoic-Cenozoic.Yet understanding tectonic deformation during Mesozoic-Cenozoic remains controversial.The Junggar Basin(JB)in Northwestern China is located in southwestern CAOB.The Northern Junggar is bounded by the Kelameili Mountains to the southeast and Qinggelidi Mountains to the northeast.The Cenozoic strata in the basin are intact and the Mesozoic-Cenozoic deformation can be found in the Wulungu step-fault zone.Therefore it is an ideal place to study this deformation.In this paper,on one hand,study the structure characteristics of Wulungu Depression and recover the deformation characteristics of the thrust system in the Hongyan Step-Fault Zone by means of structural analysis.On the other hand,in accordance with the "point-line-face" method using the existing Wulungu wells to study the sedimentary characteristics during Mesozoic.So that the evolution characteristics of Wulungu Depression can be restricted by this two aspects.It also has great significance in revealing the tectonic evolution characteristics of northern Junggar Basin.The research results are as follows:1)The tectonic style is similar in the different segments of Wulungu Depression:the boundary faults divide the Hongyan step-fault zone and Suosuoquan sag.Two sets of structural layers can be identified on the section:tectonic wedge on the bottom and imbricated structure style on the upper.Many sets of slip layers and multiphase deformation can be identified.The boundary faults have the characteristics of multiphase activities.2)During Triassic-Cretaceous period,Wulungu Depression mainly deposited a system of river-delta-late and sometimes alluvial fan is deposited.In the early Triassic,Wulungu Depression has not fully connected with Luliang Uplift,during this period,Wulungu Depression belongs to the intercontinental depression.Since the Late Triassic,Wulungu Depression formed the unified catchment basin with Luliang Uplift,the boundary faults of Hongyan step-fault zone started to thrust.During this period,Wulungu Depression belongs to the foreland basin and the fore deep probably located in the footwall of boundary faults that near the Hongyan step-fault zone.3)Faults on the step-fault zone of the northern margin of the Junggar Basin have experienced revival movement in different degrees since the Cretaceous.This represents a kind of resurrection of episodic activity.The mechanism of the thrust fault is basement-involved,in combination with triangle shear fold.Thrust activity lasted for a long duration,and can continue into Cenozoic.The intercontinental convergence between the India-Asian blocks played an important role in the reconstruction of the landform and Cenozoic deformations in Xinjiang areas,NW China.