Validating the potential application of δ2Hwax and soil brGDGTs in paleoelevation estimates on the southern slopes of the Himalaya

Paleoelevation reconstructions of the Himalayan mountains and Tibetan Plateau have been a focus of geoscientists, as they can improve our understanding of the temporal evolution of climate, biodiversity, and ecosystems. Although a few approaches for paleoelevation reconstruction have been developed in the past decades, each method has inherent strengths and weaknesses, and the uplift histories of the Tibetan Plateau based on different proxies differ considerably. Therefore, developing novel approaches and applying multidisciplinary methods to reconstruct paleoelevation is badly needed. Plant leaf wax δ2H (δ2Hwax) and brGDGTs-derived indices (MBT, MBT' or MBT'5ME) show potential for tracking environmental changes along elevation transects. However, few studies have verified the reliability of the coupled δ2Hwax-brGDGTs-derived proxies for paleoelevation reconstructions. In addition, many elevation transects studied so far were dominated by different water vapor sources, which may influence the relationship between these two proxies and elevation. In this study, δ2Hwax and brGDGTs were analyzed in topsoil along an elevation transect between 971 m and 5307 m asl (above sea level) near Mt. Annapurna, on the southern slopes of the Himalaya. With the large elevation contrast of 4336 m, and the small horizontal span (40 km), this transect is an ideal place to further evaluate the potential of δ2Hwax, MBT'5ME, and coupled δ2Hwax-MBT′5ME proxies for local paleoelevation reconstruction. The results showed that both δ2Hwax and MBT'5ME proxy indices decreased significantly with increasing elevation, suggesting that both proxies were reliable in paleoelevation estimates. Moreover, the coupled δ2Hwax-MBT′5ME proxy showed greater potential for paleoelevation estimates than the single δ2Hwax or MBT'5ME proxies. This study highlighted the great potential of the coupled δ2Hwax-MBT′5ME proxy in paleoelevation estimates, as this dual proxy can improve the correlation coefficients (R2) and reduce the uncertainties (RMSE) in paleoelevation estimates over a wide area of the globe. In addition, in order to effectively constrain the influence of environmental factors on these proxies, it is necessary to have a thorough understanding of the climatic and environmental background when applying the two proxies for paleoelevation.