Carbon Isotope Chemostratigraphy and Paleoclimatology of Hensel Formation Paleosols in Kimble County, Texas

The Cretaceous Hensel Formation located in Kimble County, Texas is an understudied unit that could benefit from stable isotope research designed to improve age constraints, provide regional to local paleoclimatological information, and improve our overall understanding of the Cretaceous greenhouse climate. Four key localities were observed, described, and sampled for lab analyses of stable isotopes: the Basal Conglomerate locality, the Big Paleosol locality, the Gentry Creek Locality, and the Upper Fines locality at the top of the section. Through chemostratigraphic correlation between δ13C isotope methodologies completed in this study (ranging from -28.15‰ and 19.62‰ δ13C vs. VPDB) and existing carbon isotope records from Phelps et al. (2015), the age of the Hensel Formation was constrained to the Albian Stage of the Cretaceous (~105 million years ago). Using key isotope data gathered from this study, combined with data from an MS Thesis by White (2009), estimates of mean annual precipitation (MAP) and mean annual temperature (MAT) reveal a warm dry climate analogous to the modern-day subtropical desert biome. Paleobarometric data were also gathered, with accepted pCO2 values (ranging from 148.6 ppmV to 566 ppmV) being similar in relation to stomatal indices of paleobarometric records around the Albian stage.