Trace element partitioning controls on cave drip water compositions through prior calcite and aragonite precipitation

Abstract

Speleothem trace element records can provide seasonal resolution climate reconstructions, but the interpretation can be challenging. Aragonite samples are understudied compared to calcite samples, despite that aragonite has 10x higher uranium concentrations and thus provide excellent dating precision. Here we present a high-resolution dataset of drip water trace elements (calcium, magnesium, strontium, barium, uranium) that are commonly affected by prior carbonate (calcite / aragonite) precipitation, a process often driven by effective rainfall. Our data suggest that prior calcite and aragonite precipitation can occur at the same drip site complicating the interpretation of strontium and uranium concentrations in aragonite speleothems. However, both processes can be distinguished with the "Sinclair test" through the trendline analysis of logarithmic relationships. Furthermore, our data show that aragonite speleothems slowly growing under relatively constant conditions are ideal to record variations in prior carbonate precipitation with its barium concentrations, independent from the prior carbonate precipitation mode. The Barium to Calcium ratio is an ideal proxy for studying rainfall-driven prior carbonate precipitation in slow growing aragonite speleothems, suggests a high-resolution geochemical study of drip water samples from Grotte de Piste, Morocco.