Quantifying Elevation Effects on δ ¹³ C, δ ¹⁸ O, and Clumped Isotope (Δ ₄₇ ) in Modern Terrestrial Carbonates From the Southeastern Tibetan Plateau: Implications for Paleoelevation Reconstruction

Abstract Carbonate stable isotope paleoaltimetry, including clumped (Δ 47 ) and oxygen (δ 18 O w ) isotopes, is extensively applied across the Tibetan Plateau. However, traditional archives such as lacustrine and soil carbonates typically require extensive sedimentary basins, which are not always available, especially in erosion‐dominated regions. This highlights the critical need for more accessible archives to diversify the options available for paleoelevation reconstruction. Widespread terrestrial carbonates such as tufas and speleothems offer a promising alternative, but their utility is often complicated by disequilibrium isotope effects from rapid CO 2 degassing. Therefore, a systematic evaluation of these non‐equilibrium archives is critically needed before they can be reliably applied to paleoelevation reconstruction. This study presents δ 13 C, δ 18 O, and Δ 47 data from modern tufas and speleothems along a 0–3,500 m elevation transect in the Yunnan region, the southeastern margin of the Tibetan Plateau. We find that despite being influenced by disequilibrium effects, site‐averaged Δ 47 values exhibit a robust positive correlation with elevation, yielding a temperature lapse rate (−5.2 ± 0.4°C/km) consistent with the regional modern air temperature lapse rate (−5.1°C/km), confirming temperature as the primary control on Δ 47 variations. Furthermore, carbonate‐derived δ 18 O w values show a strong negative correlation with elevation above 1,100 m, reflecting Rayleigh fractionation of oxygen isotopes during precipitation. The broader applicability of these relationships was further evaluated by reconstructing the elevations of Holocene carbonate coatings from the southeastern and central Tibetan Plateau. This study validates the potential of tufas and speleothems as alternative paleoelevation archives and establishes a foundational framework for their application in the Tibetan Plateau.