A branch of the Paleo-Tethys Ocean once separated the north China plate from the south China plate. However, the mode of closure of the northeastern Paleo-Tethys Ocean during the Late Paleozoic to Early Mesozoic has been debated. One reason for this debate is that the collisional suture zone was later buried by large-scale thrust faults in the southern Qinling-Dabieshan orogen, which made it difficult to reconstruct the amalgamation of the supercontinent in central China. New regional geologic mapping provides stratigraphic and structural constraints on the mechanism of this ocean closure. Our results indicate that dextral transpressional suturing in the southern Qinling-Dabieshan foreland fold-thrust belt resulted in the formation of the northern Yangtze foreland basin, where the stratigraphy precisely shows the time-transgressive closure of the ocean, and the orogenic sediments shed over 1000 km westward from eastern China to the closing Paleo-Tethys. Therefore, we propose an oblique subduction model to describe the closure of the Paleo-Tethys Ocean. Our findings suggest that prolonged slab pull during the oblique subduction of the oceanic plate continued to drive deep continental subduction, thereby forming high-and ultrahigh-pressure metamorphic rocks and leading to sustained ocean closure.

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The formation and evolution of an intracontinental basin triggered via the subduction or collision of plates at continental margins can record intracontinental tectonic processes. As a typical intracontinental basin during the Jurassic, the Qaidam Basin in western China records how this extensional basin formed and evolved in response to distant subduction or collisional processes and tectonism caused by stresses transmitted from distant convergent plate margins. The Jurassic evolution of the Qaidam Basin, in terms of basin-filling architecture, sediment dispersal pattern and basin properties, remains speculative; hence, these uncertainties need to be revisited. An integrated study of the stratigraphic succession, conglomerates, U-Pb geochronology, and Hf isotopes of detrital zircons was adopted to elucidate the Jurassic evolutionary process of the Qaidam Basin. The results show that a discrete Jurassic terrestrial succession characterized by alluvial fan, braided stream, braided river delta, and lacustrine deposits developed on the western and northern margins of the Qaidam Basin. The stratigraphic succession, U-Pb age dating, and Hf isotope analysis, along with the reconstructed provenance results, suggest small-scale distribution of Lower Jurassic sediments deposited via autochthonous sedimentation on the western margin of the basin, with material mainly originating from the Altyn Tagh Range. Lower Jurassic sediments in the western segment of the northern basin were shed from the Qilian Range (especially the South Qilian) and Eastern Kunlun Range. And coeval sediments in the eastern segment of the northern basin were originated from the Quanji massif. During the Middle-Late Jurassic, the primary source areas were the Qilian Range and Eastern Kunlun Range, which fed material to the whole basin. The Jurassic sedimentary environment in the Qaidam Basin evolved from a series of small-scale, scattered, and rift-related depressions distributed on the western and northern margins during the Early Jurassic to a larger, extensive, and unified depression occupying the whole basin in the Middle Jurassic. The Altyn Tagh Range rose to a certain extent during the Early Jurassic but lacked large-scale strike-slip tectonism throughout the Jurassic. At that time, the North Qaidam tectonic belt had not yet been uplifted and did not shed material into the basin during the Jurassic. The Qaidam Basin experienced intracontinental extensional tectonism with a northeast-southwest trend throughout the Jurassic in response to far-field effects driven by the sequential northward or northeastward amalgamation of blocks to the southern margin of the Qaidam Block and successive accretion of the Qiangtang Block and Lhasa Block onto the southern Eurasian margin during the Late Triassic−Early Jurassic and Late Jurassic−Early Cretaceous, respectively.

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