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Low elevation of the northern Lhasa terrane in the Eocene: Implications for relief development in south Tibet

The uplift history of Tibet is crucial for understanding the geodynamic and palaeoclimatologic evolution of Asia; however, the pattern of plateau uplift through space and time remains unresolved. We use stable isotope data from palaeosol carbonates to reconstruct the Eocene (~46 Ma) elevation of the Tangra Yum Co region (northern Lhasa terrane). The difference between the oxygen isotopic compositions of the studied palaeosols and Eocene surface water near the source of the Indian monsoon indicates a palaeoelevation of 2590 (+730/−910) m for Tangra Yum Co (present altitude: ~4600 m). A similar palaeoaltitude is obtained by comparing our data with modern soils and taking past environmental changes into account. Combining our results with published palaeoelevation estimates for Tibet suggests significant relief (~2 km) during the Eocene, when a low‐lying basin in the northern Lhasa terrane was bounded by the Qiangtang and Gangdese mountain belts to the north and south respectively.