Interbeded Salt-related Structural Deformation And Its Controlling Factors In The Keshen Structural Belt Of The Kuqa Depression

Two fault systems are developed in the Keshen structural belt of the Kuqa Depression: the basement-involved Kelasu major fault and the secondary detachment faults in the footwall of the major fault.The Kelasu major fault was formed under the Jurassic extension background and inversed in the late Miocene extrusion period,producing forward imbricate structure in the footwall.The trend of salts is thinning gradually from north to south in the Keshen structural belt is regular,which is to the trend of faults activity weakening gradually from north to south.The salts can be partially thinned by internal flowing when the fracture effect under salts is weak.However,the salts can be partially thickened by internal stacking when the fracture effect under salts is strong.Latest drilling and logging data indicate that the Paleogene Kumugeliemu Formation is composed of 4 interlayers.The interbeded ductile layer models are devised to physically simulate the structural evolution.Physical modeling results show that the bottom ductile layer is pierced by faults from sub-salt strata,absorbing a large number of thrust displacements.This layer also pierce overlying sand interlayer into top ductile layer,but the deformation range of it is relatively small and only concentrated in the compression side.The deformation of sand interlayer is mainly dominated by dense folds,which is even broken locally.Its intensive thickening usually occur in the footwall of the sub-salt faults with prominent thrust displacements,which is controlled by violent thrusting.As it is the only brittle interlayer,the deformation range of sand interlayer is mainly controlled by displacement of the sub-salt faults.The top ductile layer is a significant decollement,and have intensive deformation and displacement.Diapir arching promotes fold deformation in the upper-salt strata.The top micro glass bead layer bends and flows,aggregating in the compression side and diapirs.A series of interbeded ductile layer experiments with various factors furtherindicate that the overlying strata thickness,pre-existing diapir,double interbeded ductile layers and thicker top ductile layer have different controlling roles on salt-related structure deformation,evolution,etc.All above are important controlling factors on deformation in the Kelasu and Quele areas of the Kuqa Depression.