Variability in effective moisture inferred from inclusion fluid δ18O and δ2H values in a central Sierra Nevada stalagmite (CA)
Barbara E. Wortham, Isabel P. Montañez, Peter K. Swart, Hubert Vonhof, Clay Tabor
Abstract
The oxygen isotopic composition of stalagmites is widely used to infer regional changes in terrestrial surface temperatures and precipitation dynamics. The stalagmite δ18O values, however, record the influence of multiple environmental conditions (e.g., temperature, precipitation source and amount) as well as in-cave physicochemical processes and possible disequilibrium precipitation effects. The δ18O and δ2H values of fluids entombed in stalagmites as inclusions have the potential to be robust proxies of paleo-precipitation δ18O and δ2H. Here we analyze the inclusion-fluid δ18O and δ2H values for a stalagmite from a central Sierra Nevada foothill cave, McLean's Cave, to reconstruct changes in effective moisture (precipitation – evaporation) in the region over the last deglaciation (20–13 ka). The results demonstrate high variability in inclusion-fluid δ18O and δ2H values and further suggest that the δ18O and δ2H values have several intervals driven by disequilibrium dis oxygen isotopic fractionation. These findings demonstrate that effective moisture was likely lower during past warm periods in comparison to some colder periods, consistent with other stalagmite calcite-based paleoclimate records from the southwestern United States.