Single-grain multi-technique dating of sediments: a new approach to study the uplift and exhumation of the northeastern Tibetan Plateau

The northeastern Tibetan Plateau experienced a pulsed, polyphase topographic growth during the Cenozoic. The Cenozoic sediments from its surrounding intracontinental basins (i.e. Ningnan Basin) record the information on the erosion of source rocks induced by the tectonic activities in the margin of the Plateau. Besides, the outward growth of the Tibetan Plateau was progressively north-northeastward, and the source-to-sink sedimentary routing systems were deeply affected, with substantial modifications of the primary river paths through time. The variation scheme of the source-to-sink system related to several episodes of the topographic growth of the Tibetan Plateau and the tectonic activities remains to be clarified. The multi-proxy chronological analysis provides a powerful tool to link the age populations of detrital minerals with the source rock type. Low-temperature thermochronometers are sensitive to the thermal events involving the upper 3 – 5 kilometers of earth crust, which represents a useful technique for quantifying significant episodes of burial and exhumation. High-temperature thermochronometer unravels the crystallization and/or high-grade metamorphic event. In this study, we present a provenance study based on fission-track and U-Pb double dating of detrital apatite from samples of a composite Oligocene to Pliocene stratigraphic section. In contrast to a primary provenance from the Western Ordos Block during the Oligocene, the Miocene sediments mainly were derived from the recycling of Mesozoic successions that occur along the northwestern Haiyuan fault, recording its continuous activation since the Miocene. Furthermore, our AFT age data unravels a fast-cooling event during the Late Miocene, related to the ~ca. 10 exhumation of the transpressional uplifts (i.e. Liupan mountains) along the Haiyuan fault zone. The variation in sediment provenance patterns since the Miocene indicates a change in focused erosion, associated with multiple stages of rock uplift and tectonic deformation caused by strain propagation from the Himalayan collision zone towards the northeastern margin of the plateau. This project also presents apatite fission-track data of sediments from river terraces and the modern Yellow River. These data, integrated by zircon U-Pb dating and sedimentary characterization from literatures, illustrate the river system reorganizations along the northeastern margin of the Tibetan Plateau since the Middle Miocene. More in detail, our study proves that the present-day Yellow River was basically already formed in the Late Pliocene, with the primary contribution of sediments derived from the Huangshui River catchment. In the end, we realize that the Yellow River sediments were also likely to be suspended and dampened by the Liujiaxia Reservoir, which, in turn, influenced the downstream erosion regime and sediments provenance pattern.