Preservation Potential of Permian Gypsum Beds, Nippewalla Group, USA

Abstract

ABSTRACT During the Permian, what is now southern Kansas and northern Oklahoma was a drying inhospitable environment, as evidenced by the extensive red-beds and evaporites of the Nippewalla Group. Due to the fact that animals could not live in much of this extreme environment, there is a lack of a traditional fossil record in these units. Thus, this study focuses on detecting biomarkers, the chemical traces of organisms. The red-beds and gypsum were analyzed in order to assess their biomarker contents. Geochemistry similar to that found in the Nippewalla Group has been hypothesized to prevent the preservation of biomarkers due to the presence of hematite, which indicates oxidizing conditions. Due to these circumstances, a series of methods were used to investigate the detection of biomarkers. Thin sections of each rock and mineral sample, as well as two thick sections, were prepared in order to investigate the presence of fluid inclusions and any preserved organic matter through the use of fluorescence microscopy. The extractable organic matter and the total organic carbon (TOC) were also analyzed, allowing for the identification of n-alkanes, hopanes, methyl-hopanes, nor-hopanes, and isoprenoids, pristane and phytane, mostly within the gypsum. The presence of these biomarkers indicate that they can be preserved in oxidizing conditions, at least in the presence of gypsum, as it is likely the key factor to the biomarkers sustainability. The gypsum contained a number of fluid inclusions where organic material could be preserved. Also, the gypsum could create microenvironments and provide a barrier between the surrounding oxic environment and the inner anoxic environment. Understanding the preservation potential of gypsum is important as biomarkers can provide paleoenvironmental insight into the environmental conditions of the Permian. They can also provide clues to possible preservation pathways within the gypsum on Mars as the paleoenvironment of the Nippewalla Group was similar to the environment on Mars based on mineralogy and sedimentology.