青藏高原新生代构造岩相古地理演化及其对构造隆升的响应

在系统分析青藏高原新生代98个残留盆地类型、形成构造背景、岩石地层序列的基础上, 对青藏高原古新世—始新世、渐新世、中新世及上新世构造岩相古地理演化特征进行了讨论: (1)古新世—始新世: 松潘—甘孜和冈底斯带为大面积构造隆起蚀源区.塔里木东部、柴达木、羌塘、可可西里地区主体表现为大面积的构造压陷湖盆-冲泛平原沉积.高原西部和南部为新特提斯海.(2)渐新世: 冈底斯—喜马拉雅和喀喇昆仑大范围沉积缺失, 指示上述地区大面积隆升.沿雅江自东向西古河形成(大竹卡砾岩).西昆仑和松潘—甘孜地区仍为隆起蚀源区.塔里木、柴达木、羌塘、可可西里地区主体表现为大面积构造压陷湖盆沉积.塔里木西南部为压陷盆地滨浅海沉积.渐新世末塔里木海相沉积结束.(3)中新世: 约23 Ma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18~13 Ma高原及周边出现中新世最大湖泊扩张期.约13~10 Ma期间, 藏南南北向断陷盆地形成, 是高原隆升到足够高度开始垮塌的标志.(4)上新世: 除可可西里—羌塘、塔里木、柴达木等少数大型湖盆外, 大部分地区为隆起剥蚀区.由于上新世的持续隆升和强烈的断裂活动, 使大型盆地的基底抬升被分割为小盆地, 湖相沉积显著萎缩, 进入巨砾岩堆积期, 是高原整体隆升的响应.高原从古近纪的东高西低格局, 经历了新近纪全区的不均衡隆升和坳陷, 最终铸就了西高东低的地貌格局, 青藏作为一个统一的高原发生了重大的地貌反转事件. 

Evolution of Tectonic Lithofacies Paleogeography of Cenozoic of Qinghai-Tibet Plateau and Its Response to Uplift of the Plateau

By doing an integrated research on the types of 98 remnant basins, tectonic setting and lithostratigraphic sequence, we studied the evolution of tectonic lithofacies paleogeography of the Paleocene—Eocene, Oligocene, Miocene and Pliocene of Qinghai-Tibet plateau, dividing it into four stages: (1) The Paleocene to Eocene characterized by an uplift and erosional area in Songpan—Garzê and Gangdisê, depressed basins (lakes and pluvial plain) in eastern Tarim, Qaidam, Qiangtang and Hoh Xil, and Neo-Tethys sea in western and southern Qinghai-Tibet plateau; (2) The Oligocene characterized by an uplift area in Gangdisê-Himalaya and Karakorum (marked by the absence of the sediments), rivers (originated from east and flew to west) in Yarlung Zangbo Jiang (marked by the deposition of Dazhuka conglomerate), an uplift and erosional area in western Kunlun and Songpan-Garzê, and depressed basins (lakes) in Tarim, Qaidam, Qiangtang and Hoh Xil. Besides, it is also featured with a depressed littoral and neritic basin in southwestern Tarim and the termination of marine-facies deposition at the end of the Oligocene; (3) The Miocene characterized with the widespread of regional unconformity in the plateau, the overall uplift of the plateau in its adjacent area ca. 23 Ma, depressed basins (lakes) in Tarim, Qaidam, Xining-Nanzhou, Qiangtang, Hoh Xil, lacustrine-facies deposition expanding to its peak in the plateau and its adjacent area ca. 18—13 Ma, and the formation of south-north fault basins in southern Tibet ca. 13—10 Ma, all indicating that the plateau uplifted to its peak and began to collapse; (4) The Pliocene characterized by an uplift and erosional area in most part of the plateau except in Hoh Xil-Qiangtang, Tarim and Qaidam. The continuing uplift and intensive fault in plateau elevated and divided the original large basin into small basins. The lacustrine-facies deposition prominently shrank and boulderstones accumulated, indicating a response to the overall uplift of the plateau. The plateau, which was higher in east and lower in west in physiognomy in the Paleogene, experienced a process of uneven uplift and sag in the Neogene and finally became higher in west and lower in east in physiognomy. This process indicates that a great physiognomy-reverse event happened in the Qinghai-Tibet plateau.