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Aliphatic and Aromatic Biomarkers of the New Albany Shale, Illinois Basin


The New Albany Shale from the Illinois Basin is an organic-rich source rock deposited during the Middle and Upper Devonian to Lower Mississippian. This unit extends through eastern Indiana, western Kentucky, and western Illinois with the deepest part of the basins in southeastern Illinois. In this study, biomarkers were analyzed using gas chromatography-mass spectrometry to understand the geological history, conditions during deposition, and sources of organic input. Fifteen samples were taken from nine cores varying in maturity (0.39 to 1.4 Ro%), TOC (3.0 to 11.6 wt%.), and depth (outcrop to -4000 feet). Steranes, hopanoids, and n-alkanes ratios were calculated to identify geochemical trends across the basin. Two biomarkers found within immature samples of New Albany Shale, crocetane and gammacerane, provide valuable information on the geologic history of the New Albany Shale. Crocetane indicates the presence of methanogenic and/or methanotrophic archaea and the presence of gammacerane suggests a stratified water column, likely due to a hypersaline depositional environment (Sinninghe Damsté et al., 1995).