Organic and inorganic stable isotopes of lacustrine carbonate sediments are commonly used in reconstructions of ancient terrestrial environments. However, different carbonate fabrics can form contemporaneously by localized processes within a single lake. Microbes and hydrology alter the chemistry of their local environments, which can overprint the broader environmental signal preserved in the carbonate record. In this work, we explore the susceptibility of different lacustrine carbonate facies to early diagenetic and <i>in situ</i>microbial processes. To do so, we characterize geochemical and stable isotopic variability of carbonate minerals, organic matter, and water within one modern lake (Great Salt Lake, UT) within the context of seasonal and site-specific 16S rRNA amplicon sequencing community profiles. We find that facies equivalent to ooid grainstones provide time-averaged records of lake chemistry that are resistant to alteration by microbial activity, whereas microbialite, intraclasts, and carbonate mud are more susceptible to local microbial influence and hydrology. Further, we find localized occurrences of clumpedisotopic disequilibrium in the near subsurface likely driven by local microbial metabolism (e.g. sulfur cyclers) during authigenic carbonate precipitation. Our findings provide a framework for leveraging carbonate facies-specific C, O, and clumped isotope records in ancient lakes to reconstruct both regional hydroclimate and local microbial ecology.<br/>

Leveraging the carbonate record from regional hydroclimate to microbial ecology

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.