青藏高原古近纪-新近纪隆升与沉积盆地分布耦合

根据在高原及邻区近7年完成的1∶250000地质填图资料,划分出青藏高原及邻区古近系-新近系残留盆地共92个.沉积范围大且序列完整的盆地分布在高原周缘和腹地.在高原的南、北和东缘,沿区域性大断裂带分布许多走滑拉分盆地.古新世—始新世海相地层仅分布在藏南和新疆叶城地区.藏南半深海-深海沉积沿江孜-萨嘎-郭雅拉-桑麦一线分布,其海水东浅西深,西部为活动型,反映新特提斯洋闭合的时间从东向西变新,地壳抬升首先开始于东侧.晚白垩世隆起区主要分布在研究区东北部,高原总体地貌格局为东北高,西南低.古新世—始新世出现了腾冲-班戈、库牙克-格尔木新的隆起带,西昆仑隆起带向东拓展,祁连隆起带加宽,松潘-甘孜隆起区范围向东有所萎缩.渐新世期间,冈底斯和喜马拉雅带掘起,昆仑-阿尔金-祁连的进一步隆起,造成了整个高原的周缘为山系、而腹地为盆的宏观地貌格局.中-上新世期间,冈底斯和喜马拉雅带、喀喇昆仑-西昆仑地区进一步较大幅度隆起;高原从渐新世及其以前的东高西低格局,经历了中新世—上新世全区的不均衡隆升和拗陷,最终在上新世末铸就了西高东低的地貌格局,青藏做为一个统一的高原发生了重大的地貌反转事件.青藏高原新生代的隆升过程以多阶段、不均匀、非等速为特征,具有强烈的时空差异性.

Coupling between the Uplift of Qinghai-Tibet Plateau and Distribution of Basins of Paleogene-Neogene

Recent effort on comprehensive geological mapping in the Qinghai-Tibet plateau and adjacent regions permits recognition of 92 remnant sedimentary basins filled with the Paleogene-Neogene sediments. The relatively large basins with complete Paleogene-Neogene sequences are seen around the margins and at central part of the plateau. Most of the slip-pull basins are distributed along the major faults in the southern, northern, and eastern margins of the plateau. The marine Paleogene-Neogene successions are limited to the southern Tibet and the Yecheng area of Xinjiang. Both the subabyssal and abyssal sequences are exposed at the Gyangze, Saga, Guoyala and Sangmai areas. The deep-water facies successions outcrop in the west, while the shallow-water facies sequences in the east, indicating the closure of the Neo-Tethys Ocean occurring earlier in the east and then in the west. Tectonic uplift of the Qinghai-Tibet plateau occurred first in its eastern part. During the Late Cretaceous, tectonic uplift of the Plateau occurred in its northeastern part and configuration of the Plateau was characterized by paleo-highs in the northeast and depressions in the west. In Paleocene-Eocene interval, the Tengchun-Bange and Kuyake-Golmud areas experienced local tectonic uplifting; the West Kunlun uplift zone broadened easterly; the Qilian uplift zone broadened southerly; the Sunpa-Ganzi uplift zone shrank easterly. The Oligocene configuration of the Plateau was characterized by mountain chains rising along its margins and sedimentary basins occurring in the central part because of tectonic uplifts of the Gangdise and Himalaya blocks. In the same time, the Kunlun-Arjin-Qilian uplift zones have broadened southerly and northerly. In contrast, the expended uplift zones of the Gangdise, Himalaya, Karakorum, and Kunlun blocks feature the paleogeographic contours of the Qinghai-Tibet Plateau during the Miocene-Pliocene. As a result, the paleogeographic configurations of the Qinghai-Tibet Plateau turned over during the Cretaceous-Pliocene transition, with high contours in the east in the pre-Oligocene switching to the high contours in the west at the end-Pliocene. The uplift of the Qinghai-Tibet Plateau during Cenozoic is episodic and the uplifts of various blocks within the Plateau are different in space and time.