Quantifying carbon isotope disequilibrium during in-cave evolution of drip water along discreet flow paths

• Published in: Geochimica et cosmochimica acta 2019-01, Vol.244, p.182-196
• Main Authors: Mickler, Patrick J., Carlson, Peter, Banner, Jay L., Breecker, Daniel O., Stern, Libby, Guilfoyle, Amber
• Format: Article
• Language: English
• Subjects: C isotopes; Non-equilibrium; Speleothem
• ISSN: 0016-7037; 1872-9533
• DOI: 10.1016/j.gca.2018.09.027

Paleoclimate reconstructions that use speleothem proxy data have increased our understanding of terrestrial climate change, but gaps remain in our understanding of in-cave processes that influence speleothem chemistry. The δ13C values of speleothem calcite are typically influenced by kinetic isotope effects that operate during CO2 degassing and calcite precipitation. Therefore the identification and quantification of these isotopic effects is important in interpreting speleothem stable isotope records. Here we studied the change in water chemistry and δ13C values of dissolved inorganic carbon (DIC) along discreet flow paths at multiple drip sites in Inner Space Cavern, central Texas. We quantified the extent to which the water remains in C isotopic equilibrium during flow along speleothem surfaces as CO2 degasses and calcite precipitates. Two locations in the study cave that have long in-cave flow paths were examined to determine the geochemical evolution and its driving processes along these paths. At each location cave water was sampled at two points 1–2 meters apart along each flow path. Among the key spatial changes observed is a