[Objective]The Neoproterozoic strata in the Tarim Basin record the breakup of the Rodinia supercontinent and basin evolution history. Robust constraints on their stratigraphic ages are crucial for reconstructing the tectonic-sedimentary processes of the Tarim Basin during the Rodinia supercontinent cycle. Although previous studies have been conducted on the Neoproterozoic strata in the Tarim Basin, controversies remain regarding the depositional ages and sources of key stratigraphic horizons of the southwest Tarim Basin. [Methods] In this study, sedimentary analysis was conducted on the Late Neoproterozoic Yutang section in the Tieklik block of southwest Tarim Basin, which includes the Qingbaikou System Sukuluoke Formation, Nanhua System Yalaguzi Formation, Bolong Formation, Kelixi Formation, Yutang Formation, and Sinian System Kurkake Formation. Five clastic rock samples were collected from three key stratigraphic units from the Qingbaikou to Sinian Systems for compositional analysis of clasts and zircon morphology, as well as detrital zircon U-Pb dating. [Results] Based on previous stratigraphic ages, the Late Neoproterozoic stratigraphic ages have been redefined: (1) The maximum depositional age of the Qingbaikou System Sukuluoke Formation is 739.2±8.9 Ma, and its depositional age is redefined to be 740-720 Ma; (2) The maximum depositional age of the Nanhua System Yalaguzi Formation is 725±10 Ma, while the depositional ages of the Bolong Formation, Kelixi Formation, and Yutang Formation are defined as 720-700 Ma, 700-660 Ma, 660-645 Ma, and 645-635 Ma, corresponding to the Sturtian glaciation, interglacial stage, and Marinoan glaciation, respectively; (3) The maximum depositional age of the Sinian System Kurkake Formation is 677.1±9.3 Ma, and its depositional age is constrained to 635-585 Ma based on the deep-water shelf fine-clastic deposits after glacial ablation. [Conclusion] Integrated results of clast composition, zircon morphology, and detrital zircon U-Pb age spectra reveal distinct provenance change in the southwest Tarim Basin. During the Qingbaikou Period, detrital zircon ages exhibit bimodal peaks at ~780 Ma and ~1,880 Ma, indicating mixed sources from both the Tarim craton and Tianshuihai terrane. In contrast, Nanhua-Sinian strata show a unimodal peak at ~780 Ma, reflecting stable source from the Tarim craton. This provenance shift suggests tectonic separation of the Tianshuihai terrane from the Tarim craton. The structural-sedimentary evolution of the southwest Tarim Basin is interpreted as follows: during the Qingbaikou Period, isolated NE-trending rift basins developed in the southwest Tarim Basin, which was controlled by the Rodinia supercontinental breakup; During the Nanhuan Period, these isolated rifts were gradually interconnected through enhanced subsidence and sediment routing, which was influenced by sustained Rodinia supercontinental breakup, far-field effects of the subduction of the ocean along the northern Tarim margin, and global glaciation; During the Sinian Period, the basin was inherited the Nanhua structural patterns, and transferred from rifting basin to depression basin.
DownLoad: