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

Authors
  • Ingalls, Miquela1, 2
  • Frantz, Carie M3
  • Snell, Kathryn E1
  • Trower, Elizabeth J1
  • 1 Department of Geological Sciences, University of Colorado, Boulder, CO, USA.
  • 2 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA.
  • 3 Department of Earth & Environmental Sciences, Weber State University, Ogden, UT, USA.
Type
Published Article
Journal
Geobiology
Publisher
Wiley (Blackwell Publishing)
Publication Date
Sep 01, 2020
Volume
18
Issue
5
Pages
566–593
Identifiers
DOI: 10.1111/gbi.12386
PMID: 32196875
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

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., δ18 Owater , δ13 CDIC ), 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 (δ18 Ocarb , δ13 Ccarb , ∆47 ), as well as carbon isotopic compositions of bulk organic matter (δ13 Corg ) and dissolved inorganic carbon (DIC; δ13 CDIC ) 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 )), δ18 Ocarb , and calculated δ18 Owater 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. © 2020 John Wiley & Sons Ltd.

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