Insights into paleoelevation and paleo-drainage change in northern Tibet from the Late Cretaceous to late Oligocene

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Abstract
The Tibetan Plateau has drawn significant research attention for its complex formation and uplift processes. While central and southern Tibet have been relatively well studied, northern Tibet remains less explored. This study integrates zircon and calcite U-Pb dating, detrital zircon analysis, and stable and clumped isotope analyses to refine the chronostratigraphy, paleoelevation, and paleo-drainage change in the Fenghuoshan Basin. U-Pb dating of a volcanic tuff from the lower Fenghuoshan Group yielded an age of 65–64 Ma. The volcanic tuff is underlain by detrital zircon age populations of 81 Ma and 75 Ma, as well as limestone ages of 79–77 Ma, which collectively supports a revised depositional onset of ca. 80 Ma for the Fenghuoshan Group. Clumped isotope analyses from the Erdaogou area reveal extremely high temperatures (>150 °C), which makes those samples unsuitable for paleoelevation reconstruction. However, paleosol carbonate nodules found in the northernmost part of the Erdaogou area provide a more reliable proxy. Using an updated moisture mixing model, we estimate a Late Cretaceous period paleoelevation of 1260 m (+740/−870 m) at ca. 80 Ma. Furthermore, the integration of new detrital zircon data with previous provenance and paleoelevation data reveals a transition from a single northern sediment source originating from the Tanggula Mountains during the Late Cretaceous to contributions from the double flow of the Fenghuoshan Basin in the early Oligocene. This suggests the initial emergence of a topographic configuration similar to the present-day landscape in at least the early Oligocene.

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