Speleothem Formation and Composition in Hot and Cool Cave: Assessing the reliability of paleoclimate archives in high CO2 environments

Calcareous speleothems such as stalagmites are important Quaternary continental archives of past climate due to their physical and chemical properties that record hydrologic, atmospheric, and environmental cycles. The reliability of speleothems as paleoenvironmental records may be dependent on the cave conditions in which they form. Many studies have been conducted on stalagmites forming in standard cave conditions, but few have assessed the effect of high cave air temperature and CO2 on stalagmite formation and composition. This study presents mineralogical and geochemical data from a hot cave (Culebrones Cave) with high cave air CO2 concentrations and a nearby cool cave with ambient CO2 concentrations in northern Puerto Rico to examine the effects of differing cave atmospheres on stalagmite formation and on the preserved paleoenvironmental information. The stalagmites are analyzed with layer counting techniques, microscope imaging, radiometric dating, and stable isotope and trace element techniques. The results indicate the differences in the cave environments are due to physical and biological factors and that the internal atmosphere in the cave has an important effect on the formation and composition of the hot cave stalagmites.