Structure characteristics and genetic mechanism of extensional faults in Cheduba accretionary wedge-slope basin,Myanmar
YANG Songling1, XIE Jielai2
1. Research Institute of Exploration & Development Technology, CNOOC International Ltd, Beijing 100028, China; 2. SPG Secretariat of CPS, BGP, CNPC, Zhuozhou, Hebei 072751, China
Abstract:In recent years,as a kind of rare oil/gas-bearing basin,accretionary wedge-slope basins have been paid more and more attention to.At present,exploration and research on this kind of basin is relatively less,so its complex structural features,especially the genesis of the complex fault system,have been debating.There are a lot of seismic and geological data about the Cheduba accretionary wedge-slope basin,which provide a basis for study-ing the tectonic characteristics and fault genesis of the basin.Based on the regional geology and under the guidance of the idea of “vertical (tectonic) layers and lateral (segments) blocks”,firstly the fault type is defined in different stages; then the genetic mechanism of the extensional faults that are nearly parallel to the orientation of the accretionary wedge structural belt is discussed.This solves the contradiction between geological understanding and stress.On this basis,a new induced extension model of normal fault development is proposed,and three group of faults with different properties are identified in the Cheduba accretionary wedge- slope basin: S-N compressional faults,NE-SW extensional-transregional faults and NW-SE extensional faults.Controlled by oblique subduction of the ocea-nic crust of the Indian plate to the West Myanmar microplate,the compressive stress field perpendicular to the trench formed S-N compressional faults,and resulted in large-scale thrust activities,the shear stress parallel to the trench formed regulatory NE-SW extensional or transregional faults under the regional right-lateral strike-slip effect and the extensional stress field induced by different horizontal motion components during the activities of the accretionary wedge compression thrust fault zone in the front and back edge of the slope basin resulted in NW-SE extensional faults.The findings of this study are references to other accretionary wedge-slope basins.
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