Neogene drainage reorganization of Longzhong Basin driven by growth of the northeastern Tibetan Plateau: A Sr isotope hydrological perspective

The Tibetan Plateau uplift has significantly influenced Asian geomorphic and climate patterns. Drainage evolution across the plateau and its surroundings as the consequence of such changes in landscape and climate provides an opportunity to understand the growth of the Tibetan Plateau. However, the evolution history of major drainage areas around the Tibetan Plateau is largely unknown. Here, we reconstructed the evolution of drainage patterns of the Cenozoic Longzhong Basin in the northeastern Tibetan Plateau since the India-Asia collision using palaeo-water solute Sr-87/Sr-86 ratio records from its subbasins. Higher solute Sr-87/Sr-86 ratios of the Lanzhou and Xining Basins and their consistent temporal variations before ca. 22 Ma as well as lower solute Sr-87/Sr-86 ratios in the Linxia Basin collectively indicate a relatively steady drainage pattern of the integrated Longzhong Basin. A diverse evolution of the solute Sr-87/Sr-86 ratio in the Lanzhou and Xining Basins after ca. 22 Ma suggests that there was a drainage reorganization, characterized by the division of one into multiple catchment centres, in response to the growth of the northeastern Tibetan Plateau. Subsequently, the identical solute Sr-87/Sr-86 ratios in the Lanzhou and Xining Basins were further approached at ca. 16 Ma, and the rise in the solute Sr-87/Sr-86 ratios of the Linxia and Tianshui Basins occurred at ca. 9-8 Ma, indicating two subsequent changes in solute composition induced by the middle Miocene uplift and late Miocene dust expansion, respectively. Our reconstructions of Cenozoic hydrological evolution in the Longzhong Basin indicate accelerated basin segmentation and drainage adjustment with solute change in response to the growth of the northeastern Tibetan Plateau during the Neogene.