青藏高原中新世构造岩相古地理

    Miocene tectonic lithofacies paleogeography of the Tibetan Plateau

    • 摘要: 系统分析青藏高原新生代中新世50余个沉积盆地的类型、构造背景、岩石地层序列,对青藏高原中新世构造岩相古地理演化特征进行分析和探讨。中新世,青藏高原海相沉积已经全面退出,全部转为陆相沉积,约23Ma时高原及周边不整合面广布,标志高原整体隆升。塔里木、柴达木及西宁-兰州、羌塘、可可西里等地区主体表现为大面积的构造压陷湖盆沉积。约17.2Ma左右,阿尔金山显著隆升,使柴达木盆地西叉沟一带再无生物礁灰岩出现,且在盆地西部出现了短暂的沉积间断。这一时期,柴达木盆地西部开始进入湖退期,而东南部则快速湖进;同时,大约17.7Ma索尔库里山间盆地初始凹陷形成。另外,高原腹地五道梁-沱沱河盆地受南部唐古拉山的挤压抬升,在16Ma左右结束了五道梁组的沉积,在可可西里—唢呐湖一带则再次凹陷接受唢呐湖组沉积,形成高原腹地的大型压陷湖盆。13~10Ma期间,藏南南北向断陷盆地的形成,是高原隆升到足够高度开始垮塌的标志;约8Ma以来,高原东北部几乎所有湖盆均进入湖退期,普遍出现冲积扇、辫状河和水下扇砂砾岩堆积。

       

      Abstract: Based on a systematic analysis of the types of 50 Miocene sedimentary basins as well as their tectonic settings and lithostratigraphic sequences in the Tibetan Plateau, the authors investigated the evolution of the Miocene tectonic lithofacies paleogeography in the Tibetan Plateau. During the Miocene, marine sedimentation of the Tibetan Plateau was quitted completely, and changed into terrestrial deposition completely. At ca. 23Ma, the unconformities between the plateau and the surrounding areas were widespread, that marked the overall uplift of the plateau. The main bodies of Tarim, Qaidam, Xining-Lanzhou, Qiangtang, and Hoh Xil areas were characterized by large-area tectonic compressive lacustrine basin deposits. At ca. 17.2Ma, the Altun Mountains were uplifted evidently and, as a result, there was no more reef limestone in Xichagou area of Qaidam Basin. In the west of the basin, there existed short deposition disconnection. From this time, the west part of Qaidam Basin began to show lacustrine regression, but the southeast of the basin began to show lacustrine transgression quickly. At ca 17.7Ma or so, the initial sag of the Suoerkuli intermontane basin was formed. Moreover, Wudaoliang-Tuotuohe basin of the plateau hinterland was uplifted due to the compression of southern Tanggula Range. At ca. 16Ma, the deposition of the Wudaoliang Formation was finished, and Hoh Xil-Suolahu sag was formed again together with the generation of Suolahu Formation, producing large compressional lacustrine basins in the plateau hinterland. At about 13-10Ma, the formation of NS-trending faulted basins in south Tibet, such as the formation of Jilong basin, Musitang basin and Pulan basin, was the mark that the plateau was uplifted to its peak and began to collapse. Since about 8 Ma, in the northeast of the plateau, almost all lacustrine basins entered into the stage of regression, and there was sandy conglomerate accumulation of alluvial fan, braided river and subaqueous fan.

       

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