Climatic controls on leaf wax hydrogen isotope ratios in terrestrial and marine sediments along a hyperarid-to-humid gradient.

The hydrogen isotope composition of leaf wax biomarkers (δ2 H wax) is a valuable tool for reconstructing continental paleohydrology, since it serves as a proxy for the hydrogen isotope composition of precipitation (δ2 H pre). To yield robust palaeohydrological reconstructions using δ2 H wax in marine archives, it is necessary to examine the impacts of regional climate on δ2 H wax and assess the similarity between marine sedimentary δ2 H wax and the source of continental δ2 H wax. Here, we examined an aridity gradient from hyperarid to humid along the Chilean coast. We sampled sediments at the outlets of rivers draining into the Pacific as well as soils within catchments and marine surface sediments adjacent to the outlets of the studied rivers and analyzed the relationship between climatic variables and δ2 H wax values. We found that apparent fractionation between leaf waxes and source water is relatively constant in humid and semiarid regions (average: - 121 ‰). However, it becomes less negative in hyperarid regions (average: - 86 ‰) as a result of evapotranspirative processes affecting soil and leaf water 2 H enrichment. We also observed that along strong aridity gradients, the 2 H enrichment of δ2 H wax follows a non-linear relationship with water content and water flux variables, driven by strong soil evaporation and plant transpiration. Furthermore, our results indicate that δ2 H wax values in marine surface sediments largely reflect δ2 H wax values from the continent, confirming the robustness of marine δ2 H wax records for paleohydrological reconstructions along the Chilean margin. These findings also highlight the importance of considering the effects of hyperaridity in the interpretation of δ2 H wax values and pave the way for more quantitative paleohydrological reconstructions using δ2 H wax. [ABSTRACT FROM AUTHOR]