Reconsidering the uplift history and peneplanation of the northern Lhasa terrane, Tibet

Abstract

The elevation history of the Tibetan Plateau promises insight into the mechanisms and dynamics that develop and sustain high topography over tens of millions of years, as well as the contribution of uplift-related erosive flux to Cenozoic global cooling. The elevation history of the center and northern margin of the plateau have been historically less well-constrained than the southern margin. A diverse suite of techniques, each with their own biases and uncertainties, yield discrepant mid-Cenozoic elevation estimates (0–5 km). We reconstruct Paleogene to Miocene elevations of the Lunpola basin on the northern Lhasa terrane, the southernmost crustal block of the Tibetan Plateau, using stable isotope paleoaltimetry and clumped-isotope paleothermometry on lacustrine and pedogenic carbonates, integrated with previously published compound-specific n-alkane-derived hydrogen isotopes. Paleo-elevation estimates for the Lunpola basin (∼3.1–4.7 km) demonstrate that the northern edge of the Lhasa Block attained high elevation prior to ∼24 Ma and potentially by the Early Eocene (<48 Ma). Our results allow for the possibility that the entire Lhasa Block was composed of extremely thick continental crust at the initiation of India-Asia collision, rather than restricting the extent of thick crust to the Linzizong volcanic arc (“Lhasaplano” model) or Gangdese Mountains, and also refutes studies invoking a low elevation interpretation based on higher oxygen and compound-specific δD isotope values. Better constraints on depositional ages in the Lunpola basin are needed to refine the early Cenozoic elevation history along the Bangong-Nujiang suture zone. Finally, we posit that interpretations of proxy data can be biased by incomplete or selective sampling, and propose multi-proxy, intrinsically cross-disciplinary studies to resolve inconsistent interpretations from otherwise unrelated proxies.