Revised paleoaltimetry data show low Tibetan Plateau elevation during the Eocene.

Area of Science:

• Paleoclimatology
• Geophysics
• Isotope Geochemistry

Background:

• Oxygen isotope paleoaltimetry is a common method for reconstructing paleotopography.
• Previous studies suggested the Tibetan Plateau reached its current elevation by the Eocene (~40 million years ago).
• Atmospheric and hydrological changes can influence oxygen isotope ratios in precipitation, potentially biasing paleoaltimetry reconstructions.

Purpose of the Study:

• To assess the influence of Eocene paleogeography and climate on paleoelevation estimates derived from oxygen stable isotopes.
• To determine the applicability of stable isotope paleoaltimetry methods in Eocene Asia.
• To reconcile conflicting data on Tibetan Plateau elevation during the Eocene.

Main Methods:

• Utilized an isotope-equipped general circulation model (GCM).
• Simulated Eocene atmospheric and hydrological conditions.
• Compared model outputs with existing paleoelevation proxies.

Main Results:

• Simulations indicate that increased convective precipitation, air mass mixing, and widespread aridity in Eocene Asia invalidate stable isotope paleoaltimetry.
• Oxygen isotope data are likely biased due to these factors.
• Model-data comparison suggests the Tibetan Plateau had low to moderate elevations (<3000 meters) during the Eocene.

Conclusions:

• Stable isotope paleoaltimetry methods are not applicable for reconstructing Eocene Tibetan Plateau elevations.
• The Tibetan Plateau's significant uplift likely occurred later than the Eocene.
• Reconciles oxygen isotope data with other geological and paleontological proxies indicating lower Eocene elevations.