Deciphering speleothem trace element records: a combined fluorescence imaging-laser ablation approach

Abstract:

While time-resolved speleothem isotopic records have proven tremendously successful in proxying paleotemperatures, hydrological conditions and ice sheet dynamics, the interpretation of trace element signatures in stalagmites has remained relatively underexplored. With the improvement in laser ablation and ICP technologies, the analysis of trace elements is increasingly precise, especially in combination with reaction cells that allow for the analysis of elements such as phosphorus. Here, we characterize and interpret trace elements signatures from a speleothem suite from Asturias, Spain, using a combination of (1) confocal laser scanning (fluorescence) microscopy and (2) laser ablation ICP-MS mapping. We demonstrate pronounced lateral variation in trace element content in addition to regular seasonal variations, as well as morphological anomalies that may hinder the interpretation of LA-ICP-MS data. We stress the importance of prior fluorescence imaging on stalagmites, and demonstrate the pitfalls of 1-D trace element analysis.