PRESERVATION POTENTIAL OF BIOMARKERS FOR PALEOENVIRONMENTAL INVESTIGATIONS OF PERMIAN RED-BED EVAPORITES

The Nippewalla Group of southern Kansas is comprised of Permian red-bedded hematite-stained evaporites, including gypsum and anhydrite, and siliciclastic rock like sandstone, siltstone, and shale. Originally these rocks were thought to represent marine deposition, but more recently they have been reinterpreted as non-marine rocks formed in an environment marked by ephemeral saline lakes and salt pans, on the basis of their sedimentology, stratigraphy, and mineralogy. Often, fossils are used to further delineate and define a paleoenvironment, but there are not macrofossils preserved in the Nippewalla Group, likely as the environment was too harsh for animals. However, in the modern, similar environments are known to host a wide variety of microorganisms, often extremophilic Bacteria and Archaea. The molecular compounds produced by microbes can, under the correct circumstances, be preserved for 100s of millions of years. However, it has been hypothesized that iron-rich evaporites are unlikely to preserve organic compounds; they contain abundant hematite, indicating oxidizing conditions, which are not favorable to preserve organic molecules.

Nonetheless, we were able to extract organic molecules preserved in bedded gypsum collected in the Blaine Formation of the Nippewalla Group. To our knowledge, this is the first time that ancient biomarkers have been extracted from within gypsum, although previous studies have found geologically-preserved biomarkers in marls found in gypsum evaporite sequences, and have also identified biomarkers of living microbial communities hosted in endoevaporitic gypsarenites. The biomarkers we identified show some similarities to these previous studies, and also provide hope that these rocks can indeed preserve the record of the microbial community, and may be able to provide further paleoenvironmental context to the formation of the mid-Continent red beds.