| Since Cenozoic,the continuous collision between Indian plate and Eurasian plate has reactivated the South Tianshan Mountain.The complex rejuvenated foreland basins and fold thrust belts including Kuqa depression formed in the northern margin of Tarim basin.Due to its various structural types and rich oil and gas resources,the western Kuqa depression has been widely emphasized,while the eastern part has been rarely addressed.The study on the structural characteristics,the temporal and spatial differences of deformation and the influencing factors in the eastern Kuqa depression will be helpful to reveal the overall structural characteristics of Kuqa depression.It can be used to understand the relationship between the Meso-Cenozoic intracontinental structural deformation and basin-mountain coupling in western China,as well as the oil and gas exploration in Kuqa depression.This paper takes the eastern Kuqa depression as the research object.Based on the field geological survey,well and seismic data,the structural deformation characteristics and main influencing factors in the eastern Kuqa depression are analyzed by means of structural modeling,structural balance restoration and physical modeling experiments.We set up a segmented structural geological model,so as to shed new lights on oil and gas exploration.The main achievements are as the followings.(1)The eastern Kuqa depression can be divided into Tugeerming segment and Yiqikelike-Yaken segment.The structural style of Tugeerming segment is relatively simple.It is an anticline as a whole,which is controlled by the high angle pre-existing basement fault.The Cenozoic structural deformation is limited in the hanging wall of pre-existing fault,and it has the characteristics of overstep propagation.The high point of anticline migrates northward.The Yiqikelike-Yaken segment is characterized by multiple anticlines,basement-involved deformation behind and thin skin detachment ahead,delamination deformation and piggyback propagation.(2)In the eastern Kuqa depression,there are Tugerming paleo-uplift,Yiqikelike paleo-uplift and Kelasu paleo-uplift.Among them,the Yiqikeleke paleo-uplift and Kelasu paleo-uplift are Cretaceous paleo-uplift.The Tugeerming paleo-uplift has undergone multiple phase of tectonic activity respectively during late Permian,late Cretaceous and late Paleogene.The seismic thickness trend method is used to restore the thickness of strata denudation in the eastern Kuqa depression since Mesozoic.The late Cretaceous is a strong tectonic activity period with a wide range of denudation.The denudation at the late Paleogene is limited to the ancient uplift area of Tugerming.Through the restoration by structural balanced cross-sections,the formation and evolution of the Tugerming and Yiqikelike-Yaken sections are analyzed,and the different structural migration processes of the two sections are described.(3)Structural analysis and structural physical modeling experiments indicate that the pre-existing faults and the gypsum distribution are two important factors affecting the spatial-temporal differences of structural deformation in the eastern Kuqa depression.The pre-existing basement faults will be reactivated preferentially in the later tectonic movement,restricting the deformation to their hanging walls.However,if there is a good detachment layer,the structural deformation will transfer forward.As a result,the Tugerming section in the eastern Kuqa depression shows overstep propagation.On the other hand,due to the existence of thick gypsum beds of Jidike Formation(Miocene),the structural deformation is transferred to the basin interior,forming the East Qiulitage anticline and Yaken anticline. |
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