Laura S. Ruhl, University of Arkansas at Little Rock, Earth Sciences, Bentonville, AR, United States, Micheal T. Kee, University of Arkansas at Little Rock, Earth Sciences, Little Rock, AR, United States, Robert B. Jewell, University of Kentucky, Center for Applied Energy Research, Lexington, KY, United States and Erik D. Pollock, University of Arkansas, Stable Isotope Lab, Fayetteville, AR, United States