Quantitatively Tracking the Elevation of the Tibetan Plateau Since the Cretaceous: Insights From Whole-Rock Sr/Y and La/Yb Ratios

Abstract

Crustal thickness, elevation, and Sr/Y and (La/Yb)(N) of magmatic rocks are strongly correlated for subduction-related and collision-related mountain belts. We quantitatively constrain the paleo-elevation of the Tibetan Plateau since the Cretaceous using empirically derived equations. The results are broadly consistent with previous estimates based on stable isotope and structural analyses, supporting a complex uplift history. Our data suggest that a protoplateau formed in central Tibet during the Late Cretaceous and was higher than the contemporaneous Gangdese arc. This protoplateau collapsed before the India-Asia collision, during the same time period that elevation in southern Tibet was increasing. During the India-Asia collision, northern and southern Tibet were uplifted first followed by renewed uplift in central Tibet, which suggests a more complicated uplift history than commonly believed. We contend that a broad paleovalley formed during the Paleogene in central Tibet and that the whole Tibetan Plateau reached present-day elevations during the Miocene. Plain Language Summary Paleo-elevation is an important factor in understanding the mountain building processes. Strong correlations are observed between crustal thickness, elevation, and Sr/Y and (La/Yb)(N) of magmatic rocks for both subduction-related and collision-related mountain belts. We established empirical equations derived from modern examples and applied them to constrain the paleo-elevation evolution of the Tibetan Plateau since the Cretaceous. Our calculated results are broadly consistent with previous estimates based on stable isotope and structural analyses and document a complex uplift history. In central Tibet, a proto-plateau with an elevation >3,000 m was formed during the Late Cretaceous and was higher than the Gangdese continental arc in the south. This protoplateau collapsed at the same time as the southern Tibet plateau (Lhasaplano) was uplifted prior to the India-Asia collision formed before the India-Asia collision. During the India-Asia collision in the Cenozoic, northern and southern Tibet were uplift first, followed by uplift of central Tibet. A paleovalley was formed in central Tibet during the Paleogene and elevations of the whole Tibetan Plateau similar to the present-day were achieved during the Miocene.