Spatial distribution of paleoclimatic proxies in stalagmite slabs using laser-induced breakdown spectroscopy

The spatial distribution of paleoclimatic proxies in stalagmite slabs using laser-induced breakdown spectroscopy (LIBS) has been performed in this study. Stalagmites from different locations in the north of Spain were cut and analyzed along the main growth axis by LIBS. For comparative purposes, powders drilled from along the growth axis were also analyzed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Advantages of LIBS include fast analysis of long stalagmite sections at atmospheric pressure, lateral resolution in the mm range and no sample preparation beyond having optical access to the stalagmite section to be inspected. Mg/Ca and Sr/Ca intensity ratios are of major interest for paleoclimate applications. An excellent agreement between the Mg/Ca intensity ratios measured in LIBS and in ICP-AES was observed. Sr/Ca trends were well matched only in high Sr stalagmites. Also, this work reports the employment of detrital layers as paleoclimatic proxies in speleothems by LIBS. Large concentrations of Si and Al are indicative of flood events inside the cave.