Subsidence analysis of the Cenozoic Lunpola basin, central Qinghai-Tibetan Plateau
青藏高原中部新生代伦坡拉盆地沉降史分析

The Cenozoic Lunpola basin is located in the Bangong-Nujiang sutures (BNS) between Lhasa and Qiangtang terranes of central Qinghai-Tibet Plateau. Together with other continental basins in the sutures, Lunpola basin which deposits two Eocene-Miocene formations of Niubao and Dingqing reflects the re-activation of BNS. Despite the later erosion and extensive Quaternary coverage, large-scale drilling exploration since the 1950s provides fundamental data base for the study of the regional tectonic and sedimentary basin evolution. To reconstruct the subsidence history of Lunpola basin, 1 measured and 11 drilling sections were backstripped in this study. Subsidence curves indicate that the basin was characterized by two distinct phases of subsidence and a slow uplift phase. The initial rapid subsidence occurred in the Eocene, during which Niubao Formation was deposited in a shore-shallow lake environment of half-graben which was formed by fracture of upper crust in the regional extension with sinistral strike-slip. Slower subsidence which is consistent with heat conduction following the mechanical extension took place in Oligocene along with deposition of Dingqing Formation in a semi deep-deep lake environment, and the subsidence center migrated towards the north-east in this period. At the same time, in the compression settings produced by northward subduction of the Indian plate thermal subsidence gradually weakened and ended prematurely. The basement began to uplift in Burdigalian Miocene, basin was compressionally deformed, and eventually formed the present tectonic framework.