Paleogeographic and tectonic evolution of Mesozoic Qiangtang basins (Tibet)

Reconstructing the Mesozoic paleotectonic and paleogeographic evolution of marine Qiangtang basins is essential for understanding the evolution of diverse Tethyan oceanic seaways and pre-Cenozoic mountain building in the Tibetan Plateau, with significant implications for hydrocarbon exploration. The geological knowledge of these basins is, however, largely incomplete. Here we illustrate new geological mapping, stratigraphic, structural, sedimentological, and provenance data collected along a >40-km-long, well exposed cross-section of the Biluoco fold-thrust belt in South Qiangtang, together with a compilation of regional data from the Qiangtang, Amdo, and Hoh-Xil terranes. We also provide refined biostratigraphy and chronostratigraphy of the exposed successions in the Biluoco type area. Newly achieved information indicates that the North Qiangtang and South Qiangtang basins evolved independently during the Mesozoic. The South Qiangtang basin started to subside by the Late Triassic and closed by the Late Jurassic. In contrast, sedimentation in the North Qiangtang basin commenced in the latest Early Jurassic and ended in the latest Jurassic. The Qiangtang basins received sediments from volcanic rocks exposed in the central Qiangtang and Hoh-Xil terranes since the Late Triassic, whereas Paleozoic strata in the Central Qiangtang mountain range were the primary source of detritus for the North Qiangtang basin in the early Middle Jurassic and for South Qiangtang basin in the Late Triassic and Middle Jurassic. Middle to Late Triassic volcanism and convergence associated with the closure of Paleo-Tethys within the Hoh-Xil and central Qiangtang terranes resulted in the topographic uplift of the central and northern Qiangtang regions. The Jurassic development of Qiangtang basins and their final inversion were controlled by the dynamics of the northward-subducting Bangong-Nujiang oceanic slab, microcontinent accretion to South Qiangtang, and Lhasa/Qiangtang collision.