库车褶冲带博孜敦底辟新生代盐构造变形期次:来自盐动力层序的证据

Evolution of Cenozoic Salt-related Structures of Bozidun Salt Diapir,Kuqa Depression:Evidence from Halokinetic Sequences

盐动力层序是指被动盐底辟周缘发育的一套角度不整合地层,是识别盐盆地早期被动底辟的标识。库车地区盐构造由于被上新世区域大规模挤压事件显著破坏,其古新世–中新世的早期演化过程尚存在争议。本文首次将盐动力层序的研究方法运用在库车地区盐构造研究中,并通过对库车褶冲带的博孜敦盐底辟进行野外观察、地层恢复、地震解译后发现,库车地区博孜敦盐底辟南西翼渐新统–中新统发育一套与盐底辟活动相关的沉积层序,小层序之间以角度不整合为界,但随着远离底辟地层之间的接触关系很快变为整合接触,符合直立状复合型盐动力层序的模型。由此认为,库车地区早期被动盐底辟发育,盐构造的演化变形可分为两个期次:早期被动底辟期(渐新世–上新世早期)与后期挤压改造期(上新世–现今)。通过对比物理模拟结果与地震资料解译结果认为,库车地区早期被动底辟作用很可能受控于始新世以来的冲积扇沉积加载作用。

Occurrence of halokinetic sequences is regarded as the mark for early passive diapirism in salt basins. The evolution of salt structures in the Kuqa Depression of the Tarim Basin has long been debated, because partly the strongly remolded of the salt structures during the regional shortening. The latest method of halokinetic sequences, field sections, high-resolution seismic data and satellite images are used to study the Bozidun salt diapir, the second largest diapir in the Kuqa Depression, and results show that angular unconformities were preserved within the Oligocene to Miocene beds southwest of the Bozidun salt diapir, and the contact facies changed quickly from disconformable to conformable with increasing distance from the diapir, forming a typical composite halokinetic sequences stack. We thus conclude that the early passive diapirism was developed in the Kuqa Depression and the dynamics of salt structures in the Kuqa Depression could be divided into two stages,（a） the passive diapirism during Oligocene to Miocene led to the formation of the salt diapirs, and（b） the Pliocene to present shortening caused by the regional compression that reshaped all pre-existing salt diapirs.