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Published September 2020 | Supplemental Material
Journal Article Open

Carbonate facies-specific stable isotope data record climate, hydrology, and microbial communities in Great Salt Lake, UT


Organic and inorganic stable isotopes of lacustrine carbonate sediments are commonly used in reconstructions of ancient terrestrial ecosystems and environments. Microbial activity and local hydrological inputs can alter porewater chemistry (e.g., pH, alkalinity) and isotopic composition (e.g., δ¹⁸O_(water), δ¹³C_(DIC)), which in turn has the potential to impact the stable isotopic compositions recorded and preserved in lithified carbonate. The fingerprint these syngenetic processes have on lacustrine carbonate facies is yet unknown, however, and thus, reconstructions based on stable isotopes may misinterpret diagenetic records as broader climate signals. Here, we characterize geochemical and stable isotopic variability of carbonate minerals, organic matter, and water within one modern lake that has known microbial influences (e.g., microbial mats and microbialite carbonate) and combine these data with the context provided by 16S rRNA amplicon sequencing community profiles. Specifically, we measure oxygen, carbon, and clumped isotopic compositions of carbonate sediments (δ¹⁸Ocarb, δ¹³C_(carb), ∆₄₇), as well as carbon isotopic compositions of bulk organic matter (δ¹³C_(org)) and dissolved inorganic carbon (DIC; δ¹³C_(DIC)) of lake and porewater in Great Salt Lake, Utah from five sites and three seasons. We find that facies equivalent to ooid grainstones provide time‐averaged records of lake chemistry that reflect minimal alteration by microbial activity, whereas microbialite, intraclasts, and carbonate mud show greater alteration by local microbial influence and hydrology. Further, we find at least one occurrence of ∆₄₇ isotopic disequilibrium likely driven by local microbial metabolism during authigenic carbonate precipitation. The remainder of the carbonate materials (primarily ooids, grain coatings, mud, and intraclasts) yield clumped isotope temperatures (T(∆₄₇)), δ¹⁸O_(carb), and calculated δ¹⁸O_(water) in isotopic equilibrium with ambient water and temperature at the time and site of carbonate precipitation. Our findings suggest that it is possible and necessary to leverage diverse carbonate facies across one sedimentary horizon to reconstruct regional hydroclimate and evaporation–precipitation balance, as well as identify microbially mediated carbonate formation.

Additional Information

© 2020 John Wiley & Sons Ltd. Issue Online: 19 August 2020; Version of Record online: 20 March 2020; Manuscript accepted: 27 February 2020; Manuscript revised: 17 January 2020; Manuscript received: 14 November 2019. MI would like to thank Usha Lingappa for assistance in performing DNA extraction and amplification, and initial bioinformatics. MI also thanks Chi Ma for assistance with SEM imaging, and Nathan Dalleska for use of the Caltech Environmental Analysis Center, and valuable insight in designing dissolved ion analytical protocols for GSL brines. MI thanks John Eiler for use of clumped isotope facilities at Caltech and discussions of data quality and isotopic disequilibrium. MI and KS thank Brett Davidheiser‐Kroll and Andrew Chan for assistance in measurements made in the CUBES‐SIL facility and Camsizer analyses. Sampling at Great Salt Lake was carried out under permits to CF from the State of Utah Department of Natural Resources Division of Forestry, Fire and State Lands (No. 42000074) and Antelope Island State Park. Funding for this work was provided by NSF EAR #1826850 to ET and KS and #1826869 to CF. MI acknowledges financial support from the Barr Foundation.

Attached Files

Supplemental Material - gbi12386-sup-0001-supinfo.docx

Supplemental Material - gbi12386-sup-0002-tables2.xlsx

Supplemental Material - gbi12386-sup-0003-tables5.xlsx

Supplemental Material - gbi12386-sup-0004-tables6.xlsx

Supplemental Material - gbi12386-sup-0005-tables7.xlsx


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