Evaluation of leaf wax δD and soil brGDGTs as tools for paleoaltimetry on the southeastern Tibetan Plateau

Abstract The orogenic history of the Tibetan Plateau (TP) and surrounding mountain rangescontinues to be a major source of disagreement among geologists, particularly concerning the uplift modelsfor the Cenozoic evolution of the TP and estimates for when the highest and largest plateau on Earth reached its current elevation. Quantitative reconstructions of past elevation from geologic samples are necessary to document the uplift history of TP and examine the interactions between tectonic-relief and climate over geological time-scales. Several studies establishing lipid biomarker-based paleoaltimetry based on leaf waxδD values and brGDGTs have been reported in recent years for the TP and surrounding regions, but have yet to be synthesized into a regional framework for paleoelevation determination and uncertainty analysis. Here we report new leaf waxδD and brGDGTs data developed from surface soil samples along an elevation transect spanning ~1250–3900 m.a.s.l in the Hengduan Mountains on the southeastern edge of the TP. We find that the abundance-weighted mean leaf waxδD ( n -C 27 , n -C 29 and n -C 31 ) values ( δ D wax) lapse ratesdetermined for the Hengduan Mountains and for five other nearby study locations are statistically indistinguishable, and can be combined to provide a regional δ D wax lapse rateof −1.97 ± 0.04‰ (1 σ )/100 m for use in regional paleoelevation studies across the southeastern TP. We also find a strong correlation (R 2  = 0.71) between brGDGTs and elevation-dependent mean annual air temperature, which contributes to a number of studies in the region that support the use of fossil brGDGTs as a paleoelevation proxy. Our results reveal that δ D waxand brGDGTs for the Hengduan Mountains provide similar empirical uncertainty in paleoelevation reconstruction, with standard errors of elevation estimation ( SE ) of ±483 m (±1 σ ) and ± 394 m (±1 σ ), respectively. We propose a paleoaltimetric approach that combines δ D waxand brGDGT data, in order to derive paleoelevation estimates with lower uncertainties. In the Hengduan Mountains data set, the approach yields a SE (±286 m; ±1 σ ) that is 27–40% lower than when δ D waxvalues and brGDGTs are applied separately.