Structural Modeling Of The Huangling Anticline And Its Peripheral Structural Belt

The deformation process and deformation mechanism of intracontinental structures are hot topics in current structural geology researches.Huangling anticline is located at the northern margin of the South China Block and the interaction position of the multi-directional tectonic lines.It is an important window for studying the intracontinental structural deformation of the South China Block,and it is an important oil-gas exploration belt.Therefore,it is of great theoretical and practical significance to study the structural modeling of the Huangling anticline and its adjacent area.On the basis of summarizing the previous researches,this paper analyzed the regional geological data and interpreted the newly acquired seismic profiles in Huangling area.With the lightening of the fault-related fold theory,the geological structure and kinematic models of Huangling anticline and its adjacent structural units have been put forward.The understanding of the genetic model of the Huangling anticline and its adjacent areas has been proposed.The main conclusions of this aticle are as follows.(1)The Huangling anticline is dominated by the superimposed tectonic wedges.The floor front-thrust fault is a detachment layer in about 20 km depth,and the roof back-thrust fault is the fault connecting the shale layer in Silurian and floor front-thrust fault with an eastward dipping slope.The floor front-thrust fault is the roof back-thrust fault of the underlying structural wedge,and the roof back-thrust fault is the Silurian shale layer.The kinematic model of the Changyang-Zhangjiahe anticline is superimposed structural wedges.The Xianglongshan anticline is deformed as the combination of the fault bend fold and structural wedge.The structural deformation of the southern and northern limb of the Zigui syncline is mainly caused by thrust wedging,and the sloping of the western limb is caused by the duplex structure.The Xiannüshan fault is a multi-phase active fault,and it is not a main fault in Huangling area.The formation of the Yichang slope and the western limb of the Dangyang syncline originated from the formation of the Huangling anticline,and the eastern limb of the Dangyang syncline was controlled by the structural wedge movement,accompanied by the deformation of the base rocks.(2)There are four key tectonic transformation periods of Huangling anticline and its adjacent structural units: the Late Triassic,the Late Jurassic,the later period of the Early Cretaceous to the Late Cretaceous,and the late period of the Paleogene.(3)In the Late Triassic,uplifting is the main way that the deformation occurred in the Huangling area;in the Late Jurassic,a strong intra-continental deformation occurred in the Huangling area.With the clockwise rotation of the South China Block and the activity of the peripheral structural belts in the early stage of the Late Jurassic,the structural wedge in the deep part of the Huangling anticline serves as a way for the basement material extrusion eastward of the South China Block,and the Huangling anticline formed in the area that limited by the peripheral structural belts,and then the further activities of the structural belts around the Huangling anticline led to the formation of the Changyang anticline,the Xianglongshan anticline,and the sloping of the southern limb of the Zigui syncline.In the later period of the Early Cretaceous,the extrusion in north-south direction caused the formation of the Shennongjia anticline in the southern Daba thrust belt and the sloping of the northern limb of the Zigui syncline.The extension in west-east direction in the Huangling area caused the uplift of the Huangling granite and the formation of Yuan'an graben.The Dangyang syncline underwent a stretching deformation at the same time.During the late period of the Paleogene,with the occurrence of the Himalayan tectonic movement,the periphery of the Huangling anticline suffered a transition from the extension to extrusion in westeast direction.The Changyang anticline and the Xianglongshan anticline formed a structural nose and the Zhangjiahe anticline formed as an inverted fold.The Yuan'an graben and Dangyang suffered another structural inversion,and the structural pattern of the Huangling anticline and itsadjecnt area has basically formed.(4)The structure and evolution history of the Dangyang anticline is simple,and this struactural unit has a great potential for the oil and gas exploration.