Late Eocene-Oligocene High Relief Paleotopography in the North Central Tibetan Plateau: Insights From Detrital Zircon U-Pb Geochronology and Leaf Wax Hydrogen Isotope Studies

摘要

The knowledge of provenance and paleoelevation of late Cretaceous-Cenozoic terrestrial basins is crucial in discriminating different topography growth models for Tibetan Plateau. The Hoh Xil Basin is located in the north central Tibetan Plateau, and its thick sediments provide an excellent record for investigating the growth history of Tibetan Plateau. Here we present an integrated study by applying detrital zircon U-Pb geochronology and leaf wax n-alkane hydrogen isotope analysis to the Yaxicuo Group in the Tuotuohe subbasin of the southern Hoh Xil Basin. Maximum depositional age from the youngest detrital zircon U-Pb ages, along with previous palynological data, indicates that the Yaxicuo Group was deposited during late Eocene-Oligocene. Provenance analysis shows that the Yaxicuo Group was mainly sourced from the northern Qiangtang and Songpan-Ganzi terranes. Detrital zircon age spectra of the Yaxicuo Group samples show 33-50 Ma age group in the Tuotuohe subbasin, which is distinctive from those in the Erdaogou subbasin to the north, suggestive of formation of watershed within the Hoh Xil Basin and the tectonic transition from foreland to hinterland basin. The most negative leaf wax hydrogen isotope value yields an estimate of paleoelevation of similar to 4 km, which records the high elevation of the source regions in the northern Qiangtang. We argue that sedimentary record of the Yaxicuo Group with the interpreted transition from foreland to hinterland basin is the result of the northward propagation of the upper crustal shortening, which in combination with other deep processes caused the surface uplift of the Hoh Xil Basin.