西南天山新生代隆升-剥露过程的沉积-构造响应

Tectonic-Sedimentary Response of Cenozoic Uplifting and Exhumation in the Southwestern Tianshan

西南天山山前新生代沉积反映了天山的隆升-剥露过程。通过巴雷公岩体南侧的山间盆地内新近系苍棕色组(N_2~1c)和砾岩组(N_2~2-Q_1)l中的砾石成分进行统计,并对天山山前的构造变形进行初步研究,结果显示砾石成分主要为碎屑沉积岩类,含有少量碳酸盐岩砾石和变质岩砾石,且变质岩砾石主要出现在砾岩组内(N_2~2-Q_1)l,基本未见花岗岩砾石。这一结果表明在上新世晚期-第四纪早期,巴雷公岩体还没有被剥露出地表,直到Q_1砾岩组沉积之后才隆升-剥露到地表。西南天山山体的构造变形特征表明,西南天山强烈的逆冲推覆构造是山体隆升-剥蚀的动力来源。通过对岩体隆升和地表隆升的分析,认为西南天山的地貌特征是在晚更新世才开始快速形成的。

The Cenozoic sediments on the piedmont of southwest Tianshan recorded the processes of uplift and erosion of the Tianshan Mountains.Pebbles of the Cenozoic conglomerate in the Cangzongse(N1 2 c)and Liyan(N2 2-Q1)l Formations in the foreland basin near the Baleigong pluton and structural deformation of the basin are investigated in this study.The results show that the components of pebbles are mainly clastic sedimentary rocks and a small amount of carbonate rocks and metamorphic rocks,however,the metamorphic pebbles are mainly found in the Liyan(N2 2-Q1)l Formation.It is worth noting that there is no granite pebbles in the Cenozoic conglomerate,which indicates that the Baleigong pluton had not been exposed until the late Pleistocene.Field survey of the structural deformation demonstrated that the thrust structure in the southwestern Tianshan Mountains are the dynamic source of uplift.Based on the analysis of rock uplift and surface uplift,the southwest Tianshan Mountains were shaped since the Late Pleistocene.