Developing LA-ICP-MS Data Set In Stalagmites As Paleoclimate Indicators: Case Of Anjokipoty Cave, Northwestern Madagascar

Stalagmites contain numerous proxies that can be used for paleoclimatology. Their readiness to preserve geochemical information and near-continuous growth pattern gives them the capacity to reveal seasonal to decadal chronology resolution. Common geochemical proxies include stable isotopes of oxygen (δ18Oc) and carbon (δ13Cc), which are chronologically constrained using U-Th dates. However, these proxies may be influenced by various factors, making their interpretation more challenging. These influences can include, but are not limited to atmospheric chemistry, bedrock lithology, prior calcite precipitation (PCP), overlying vegetation/soil, and secondary alteration of aragonite into calcite. To help better interpret these conventional stable isotope proxies, we added trace element data that were generated using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). LA-ICP-MS analysis can be used to rapidly collect trace elements with high spatial resolution in stalagmites and the records can be used as paleoclimate indicators. Here, we developed a LA-ICP-MS dataset using stalagmite MAJ-1 from Anjokipoty Cave, collected from Northwestern Madagascar. In this specific study, the LA-ICP-MS counts were calibrated with the concentrations of trace elements obtained from EPMA spot analyses to convert the counts to concentration values. Two parallel line scans were run along the growth axis of MAJ-1 and then averaged to amend possible lateral trace element concentration variability. Previously collected U-series dating has been used to create an age model of MAJ-1, which covers approximately 147 years BP (where BP= before present, and present= 1950). Our most important finding suggests that uranium concentrations in stalagmites can be used as a proxy for rainfall. We also find that strontium, barium, and uranium concentrations can be used as proxies for PCP and paleohydrology. This high-resolution trace element data set can potentially lead to more information on paleoclimatic variation trends and interpretations about seasonal wetting and drying over the last quarter millennium.