Crustal development of the eastern Tibetan Plateau preceding and post India-Asia continent-continent collision: Insights from terrestrial ‘redbed’ basins in the Yidun Arc Terrane

Abstract:

Understanding the spatial crustal configuration and temporal evolution of the pre-Cenozoic ancestral Tibetan Plateau is essential to accurately model the Himalayan-Tibetan orogenic system. The eastern Tibetan Plateau contains several terrestrial ‘redbed’ basins within the Yidun Arc Terrane (YAT) that preserve a Mesozoic sedimentary record of YAT post-accretionary tectonism, and a Cenozoic sedimentary record influenced by terrane collisions to the south, including arc magmatism and re-activation of inherited structures in response to strike-slip translation and far-field deformation. The West and East Ganzi basins in the northern YAT formed in a compressional tectonic setting and basin fill records a detrital zircon signature indicative of provenance from Precambrian and Paleozoic rocks of the Zhongza Massif and local Mesozoic Yidun arc plutons. The West and East Ganzi basins may be isolated flexural basins associated with the collision of the YAT and the Gondwana-derived Qiangtang Terrane with the Lhasa block during the Jurassic-Early Cretaceous time. Structural analysis shows that the West and East Ganzi basin strata have deformational phases associated with additional Mesozoic terrane collisions, far-field reactivation deformation associated with the India-Asia collision, and Late Cenozoic strike-slip deformation associated with growth of Tibetan Plateau. The Jawa and Mula basins located in the YAT to the southeast of the West and East Ganzi basins contain similar basin fill and structural features; however, both the Jawa and Mula basins contain a Cenozoic zircon population, establishing a maximum depositional age of ~41 Ma for both basins. The Jawa and Mula basins formed as small isolated basins associated with Early Cenozoic far-field deformation related to the India-Asia collision. Analyses of these four basins, along with recent study of Mesozoic deposits in the Qamdo basin of the eastern Qiangtang area to the west, shows that the southeastern Tibet plateau region experienced significant Late Mesozoic-early Cenozoic tectonism before the India-Asia collision; this record highlights Mesozoic crustal heterogeneity that influenced the late Cenozoic uplift evolution of the modern Tibetan Plateau.