西昆仑山前和田-柯克亚挤压构造带新生代变形时序及其地质意义

摘要

The uplift of the West Kunlun Mountains led to the development of the Cenozoic fold and thrust belt in eastern section of the piedmont of West Kunlun ranges. This paper focuses on the growth strata and sedimentary pattern of the fold and thrust belt to constrain the uplift time of the West Kunlun Mountains. There are three set of growth strata along the Keliyang-Fusha structural belt in the piedmont of West Kunlun Mountains. The first set of growth strata which deposited in the front limb of Kedong structure started at Middle Miocene, the second one deposited in the back limb of Kekeya anticline since Early Pliocene, and the third one deposited in the front limb of Kekeya anticline in Late Pliocene. It is evident that the Kekeya anticline began tectonic deformation since Pliocene, and the second growth strata were related to this anticline. It displayed“anti-fanning”shape, which is characterized by the break-forward sequence. On the other hand, geological age of growth strata in the Hetian’nan anticline (south Hetian anticline) is the Middle Miocene. Therefore, the Hetian-Kekeya structural belt began deformation since Middle Miocene too. Combined with the wedge shape sediment of the Cenozoic fold and thrust belt in eastern section of the piedmont of West Kunlun, we infer that the Western Kunlun Mountains uplift from Miocene, while the intensive uplift stage of Western Kunlun Mountains began at Pliocene.%受西昆仑山抬升挤压的影响，西昆仑山前东段发育褶皱冲断带，最新反射地震资料显示该地区发育了多套新生代的生长地层。本文利用这些生长地层数据分析了和田-柯克亚挤压构造带的变形时序，并且结合新生界的沉积形态探讨了西昆仑山的挤压隆升时间。研究结果表明，西昆仑山前和田-柯克亚挤压构造带西段的克里阳-甫沙构造发育三期前列式的生长地层：第一期在甫东构造东端始于中新世中期安居安期；第二期从上新世早期在柯克亚背斜后翼沉积；第三期在上新世晚期沉积于柯克亚背斜前翼，揭示柯克亚背斜变形时间，并且第三期构造变形将第二期生长地层旋转变形为“反向扇形”的形态，第二期生长地层形成由翼部向背斜顶部逐渐增厚、下部地层向上部产状变陡的奇怪现象。另一方面，和田南背斜的生长地层也从中新世中期开始沉积，因此西昆仑山前和田-柯克亚挤压构造带的变形时间始于中新世中期。结合西昆仑山前东段新生代褶皱冲断带区域剖面中显示的从中新世开始、向盆地内减薄的沉积楔形体，作者认为西昆仑山中新世中期开始，挤压隆升作用已经扩展到山前和田-柯克亚挤压构造带。