Organic biomarkers in active and fossil travertine deposits
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Clues regarding the past history of microbial life on Earth may be deciphered from carbonate rocks given knowledge of the preservation potential of biosignatures. Toward this end, active and fossilized microbial mats from Jackson Mountain travertine ridge (Nevada) were analyzed for grain fabrics, mineralogy, stable isotope compositions, and organic biomarkers within the context of a facies model to better understand preservation in carbonate hot springs. Three distinct facies were recognized for active springs: 1) vent, 2) proximal slope, and 3) distal slope. Facies had similar ´C values for bulk biomass indicative of a C3 fixation pathway; however, microbial phospholipid fatty acid and hydrocarbon biomarkers varied in composition. The dominant attributes of fossil deposits were similar to the active springs, however the abundance of biomarkers varied. This study demonstrates that numerous attributes of fossil hot springs can be used to identify specific environmental conditions and microbial communities present during travertine deposition.