MICROBIAL INFLUENCE ON PYRITE AND IRON OXIDE IN THE PRAIRIE BLUFF FORMATION, STARKVILLE MISSISSIPPI

The objective of this study was to determine if microbes were associated with pyrite, gypsum, and iron oxide found in the Prairie Bluff Formation in Starkville, Mississippi and if so, to determine if associated chemical processes contributed to the formation of these minerals. Gray to black nodules (1-3 cm) were composed of quartz and calcite, and burrows (10-100 cm) were delineated by layers of iron oxide, gypsum, and pyrite. Students collected samples in the field and prepared them for XRD analysis, SEM, confocal, and petrographic microscopy. In the collected samples, chains of bacilliform bacteria were discovered as well as fungal hyphae >10 microns wide, bacilliform microbes and filamentous bacteria <5 microns wide. Organic matter was abundant in the form of fungal filaments, bacilliform microbes, and amorphous desiccated organic matter. Evidence of dissolution was also abundant throughout all the samples. Dissolution seemed to be associated with abundant microbial material and seemed to be greater along marked zones. Organic substances likely played a role in dissolution and probably contributed to precipitation; however, the results are inconclusive as to whether or not organic matter played a role in crystallization.