Abstract: Overburden deformation can be fully or partially decoupled from basement faulting through viscous flow of salt during thick-skinned extensional salt tectonics.Conceptual modeling suggests that whether deformation is fully or partially decoupled is largely controlled by the balance between the rates of salt flow and space creation.When salt flows fast enough to fill the extensional space created in both basement and cover,overburden deformation is fully decoupled from basement faulting.Conversely,when space is created faster than it is filled by salt flow,the deformation is partially decoupled.Analytical modeling indicated that salt flow in sediment-starved basin was mostly controlled by the thickness of the salt layer,salt viscosity,and thickness of overburden sediments.Moreover,space creation was mostly controlled by slip rate along the basement fault (thus regional extension rate) and by the length of the subsiding basement hanging wall.Thick salt layer,low salt viscosity,slow extension,and a short basement hanging wall all favored decoupling of the overburden from basement.Conversely,thin salt layer,high salt viscosity,rapid extension and a long subsiding basement hanging wall could cause partially decoupled deformation.Synkinematic deposition affected the thick-skinned extensional salt tectonics mostly during partially decoupled deformation.Thicker sediments above the basement of hanging wall can trigger sedimentary differential loading,causing salt to flow from above the basement hanging wall toward the basement footwall and enhancing forced folding above the basement fault.

Key words: thick-skinned extension, salt tectonics, overburden structure, analytical modeling, structural geology

摘要： 理论分析表明,盐撤量与拉伸造成的空间之间的平衡是决定拆离滑脱形变完全与否的控制因素.当盐撤量大于同期形成的拉伸空间时,上覆层发生完全拆离滑脱形变;反之,则发生非完全拆离滑脱形变.分析模拟表明,盐层越厚、岩盐粘滞度越小及上覆前构造层越厚,盐撤量就越大,完全拆离滑脱形变过程持续得也越久;区域拉伸和基底断层位移速率越大及基底断层下降盘越长,完全拆离滑脱形变过程的持续时间就越短.

关键词: 厚皮拉伸, 盐构造运动, 上覆层构造, 分析模拟, 构造地质学