Sedimentary Evolution of the Qinghai-Tibet Plateau in Cenozoic and its Response to the Uplift of the Plateau

We have studied the evolution of the tectonic lithofacies paleogeography of Paleocene- Eocene, Oligocene, Miocene, and Pliocene of the Qinghai-Tibet Plateau by compiling data regarding the type, tectonic setting, and iithostratigraphic sequence of 98 remnant basins in the plateau area. Our results can be summarized as follows. （1） The Paleocene to Eocene is characterized by uplift and erosion in the Songpan-Garze and Gangdise belts, depression （lakes and pluvial plains） in eastern Tarim, Qaidam, Qiangtang, and Hoh Xil, and the Neo-Tethys Sea in the western and southern Qinghai-Tibet Plateau. （2） The Oligocene is characterized by uplift in the Gangdise--Himalaya and Karakorum regions （marked by the absence of sedimentation）, fluvial transport （originating eastward and flowing westward） in the Brahmaputra region （marked by the deposition of Dazhuka conglomerate）, uplift and erosion in western Kunlun and Songpan-Garze, and depression （lakes） in the Tarim, Qaidam, Qiangtang, and Hoh Xil. The Oligocene is further characterized by depressional littoral and neritic basins in southwestern Tarim, with marine facies deposition ceasing at the end of the Oligocene. （3） For the Miocene, a widespread regional unconformity （ca. 23 Ma） in and adjacent to the plateau indicates comprehensive uplift of the plateau. This period is characterized by depressions （lakes） in the Tarim, Qaidam, Xining-Nanzhou, Qiangtang, and Hoh Xil. Lacustrine facies deposition expanded to peak in and adjacent to the plateau ca. 18-13 Ma, and north-south fault basins formed in southern Tibet ca. 13-10 Ma. All of these features indicate that the plateau uplifted to its peak and began to collapse. （4） Uplift and erosion occurred during the Pliocene in most parts of the plateau, except in the Hoh Xil-Qiangtang, Tarim, and Qaidam. The continuous uplift and intensive taphrogeny in the plateau divided the original large basin into small basins, deposition of lacustrine facies decreased considerably, and boulderstone accumulated, indicating a response to the overall uplift of the plateau. Here, we discuss the evolution of tectonic lithofacies paleogeography in Cenozoic and its response to the tectonic uplift of the Qinghai-Tibet Plateau in relation to the above characteristics. We have recognized five major uplift events, which occurred during 58-53 Ma, 45-30 Ma, 25-20 Ma, 13-7 Ma, and since 5 Ma. The results presented here indicate that the paleogeomorphic configurations of the Qinghai-Tibet Plateau turned over during the late Miocene, with high elevations in the east during the pre-Miocene switching to high contours in the west at the end of Miocene.

Division of tectonic-strata superregions in China

The continent of China is grouped into Pan-Cathaysian blocks,Laurasia and Gondwana Continental margins and relics of three oceans-Paleoasian,Tethys,and Pacific as a whole.In detail,the continent of China grew up by coalescence of three blocks or platforms (North China,Tarim and Yangtze)and eight orogenic belts (Altay-Inner Mongolia-Daxinganling,Tianshan-Junggar-Beishan,Qinling-Qilian- Kunlun,Qiangtang-Sanjiang,Gangdise,Himalaya,Cathaysia,Eastern Taiwan)during the processes of oceanic crust disappearance and acceretionary-collision of continental crusts.In the orogenic belts,six convergent crustal consumption zones (Ertix-Xar Moron,South Tianshan,Kuanping-Foziling,Bangong co-Shuanghu-Nujiang-Changning-Menglian,Yarlung-Tsangpo,Jiangshao-Chenzhou-Qinfang)have been distinguished.Correspondingly,the strata of the continent of China are subdivided into 17 tectonicstrata superregions,which tectonically belong to three blocks or platforms,six convergent crustal consumption zones and eight orogenic series,respectively.This division is based mainly on differences of tectonic environment and tectonic evolution among blocks,zones and belts,including the timing of when the oceanic crusts transferred into continental crusts,the paleobiogeographic features,and the types of strata.