Leveraging the carbonate record from regional hydroclimate to microbial ecology

Org. and inorg. 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 hydrol. alter the chem. 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 in situmicrobial processes. To do so, we characterize geochem. and stable isotopic variability of carbonate minerals, org. 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 equiv. to ooid grainstones provide time-averaged records of lake chem. that are resistant to alteration by microbial activity, whereas microbialite, intraclasts, and carbonate mud are more susceptible to local microbial influence and hydrol. Further, we find localized occurrences of clumpedisotopic disequil. in the near subsurface likely driven by local microbial metab. (e.g. sulfur cyclers) during authigenic carbonate pptn. 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 ecol.