Speleothem Isotope Records and Precipitation Dynamics in the Peruvian Andes

Speleothems are valuable proxies of paleoclimate due to their ability to preserve isotopic signatures; thus, speleothems can record past changes in precipitation and climate. However, the degree to which surface climate signals are preserved in cave drip water, and ultimately the stalagmite, is uncertain. This study presents data from a Pacapacuain cave in the tropical Peruvian Andes that evaluates how accurately meteoric water isotope compositions (δ¹⁸O) signals are transmitted through the karst system. The results show strong seasonal variability in precipitation δ¹⁸O, with lower values found consistently in the wet season, which reflects the amount effect. Cave drip water δ¹⁸O remained constant for the four years of study and did not reflect the seasonal patterns that are seen at the surface, but did match average precipitation from the rainiest months. Additionally, cave drips off speleothems were a fraction of the total surface rainfall and lagged peak precipitation months on the order of 2-3 months. The results suggest that water is stored within the epikarst or does not reach the cave until large amounts of seasonal rainfall. Understanding these processes is crucial in being able to accurately interpret speleothem records and reconstruct past monsoon variability in the tropical Andes.