After a short literature review, I am not finding any papers that mention measuring organic C and N isotopes and concentrations in samples that are primarily gypsum. If anyone can point me to a reference to get started, I would appreciate it.

Marilyn Fogel

Dr. Marilyn L. Fogel, 
Wilbur W. Mayhew Professor of Geo-Ecology
Director of the Environmental Dynamics and Geo-Ecology Institute
Dept. of Earth Science/Environmental Science
University of California Riverside
900 University Ave.
Riverside, CA 92521
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Phone: 209-205-6743