THE YITONG GRABEN-THE STRUCTURAL FEATURES AND EVOLUTION OF A STRIKE-SLIP FAULT BASIN

The Yitong Graben is a Tertiary petroliferous strike-slip fault basin developed on the Hercynian fold basement.It has long and narrow asymmetric graben structure.Its fault structure is complex,developing normal-slip faults and reverse-slip faults.The compound superimposed structure formed by the joint action of tenso-shearing and compresso-shearing is its main structural pattern.The formation and evolution of the graben includes initial fault depression,main fault depression and renew action three stages. During the formation of the graben,the inhomogeneous distribution of stress due to the restriction of boundary faults resulted in differential subsidence between east and west and uplift and sag interval change from south to north within the graben,the depocenter and the subsidence center migrating with different faulting stages.