Discovery of the large-scale paleo-weathering crust in the Qiangtang basin, northern Tibet, China and its significance

Recently, a new paleo-weathering crust occurred at the top of Carboniferous and Permian strata and Xioachaka Formation, was discovered in the North Qiangtang depression, central uplift and the South Qiangtang depression during field investigation of petroleum geology, indicating a regional distribution. New geologic survey indicates that the weathering and erosion are various in different stages. During the Late Permian, most part of the South Qiangtang and central uplift regions was uplifted into a land and subjected to the weathering and erosion, and then a paleo-weathering crust was formed widely at the top of the Longge and Lugu Formation. By the Late Triassic, most part of the North Qiangtang region was also uplifted into a land and subjected to the weathering and erosion, and then a large weathering and erosion region, including the North Qiangtang depression, central uplift and the South Qiangtang depression, was formed. After a short erosion process (especially for the Xiaochaka Formation), these paleo-weathering crusts were overlapped by the Nadi Kangri volcanic-volcaniclastic rocks and corresponding sediments. The discovery of large-scale paleo-weathering crust is important for assessing petroleum geological conditions in the Qiangtang basin and the overall significance of basin evolution.