Great Salt Lake (Utah) Microbialite δ¹³C, δ¹⁸O, and δ¹⁵N Record Fluctuations in Lake Biogeochemistry Since the Late Pleistocene

Abstract

Extensive lacustrine microbialite deposits exposed along the shores of Great Salt Lake (GSL), Utah preserve a rich continental paleoenvironmental record. Newly‐reported microbialite carbon and oxygen stable isotope ratios in carbonate, nitrogen isotope ratios in organic matter, and organic matter radiocarbon ages archive paleolake hydrological and biogeochemical changes from the late Pleistocene through the Holocene. Positive correlations between δ18O and δ13C in ∼15 – 7.6 cal ka microbialite carbonate are consistent with a hydrologically closed‐basin lake with fluctuations in volume, chemistry, and associated changes in lake primary production. The δ15N of microbialite bulk organic matter (5 – 18 ‰ versus AIR) shows that the balance between nitrogen fixation and assimilation of dissolved inorganic nitrogen has varied significantly. Inverse δ18O and δ13C correlations in combination with high δ15N in some carbonate deposits may imply periods of higher salinity and stable lake stratification similar to modern GSL conditions. We compare our C and O data sets with Pleistocene Lake Bonneville carbonate stable isotope records and demonstrate progressive development of spatially‐isolated hydrological basins during the shift to warmer and drier conditions in the Holocene.

Microbially influenced lacustrine carbonates: A comparison of Late Quaternary Lahontan tufa and modern thrombolite from Fayetteville Green Lake, NY

“…Warmer climate during the Holocene could potentially have altered the biogeochemical cycling of nitrogen within the lake or microbialite communities resulting in a stronger signal from water column nitrate reduction. In general, the δ 15 N values of the WDL tufas are consistent with organic matter produced in a lacustrine, aquatic environment (Talbot, ), such as that observed in Fayetteville Green Lake (Shields, ) and in recent and modern microbialites from Great Salt Lake (Newell et al, ).…”

“…Radiocarbon ages of calcium carbonate in Lahontan deposits may be inaccurate due to the reservoir effect (low initial 14 C/C ratios in lake water or from groundwater influx) or by addition of modern carbon during diagenesis (Benson, ). In order to minimize the potential inaccuracy of age dates from the reservoir effect, age dating of the organic residual fraction preserved in the carbonate may be used to provide a more accurate age date (Brook, Railsback, & Marais, ; Ghinassi et al, ; Newell et al, ). In one sample from each site, both the organic C and carbonate were measured in order to evaluate the potential discrepancy between these dates (Brook et al, ).…”

“…Although microbialite depositional environments are diverse, actively accreting microbialites in modern lakes share similar textural characteristics and are typically associated with photosynthetic microbial communities such as cyanobacteria and diatoms (Chagas et al, ). Lake sediments, and carbonates in particular, preserve a variety of geochemical proxies that may be used for reconstruction of lake paleoenvironments (e.g., Newell, Jensen, Frantz, & Vanden Berg, ; Yang et al, ). Modern microbialites have been demonstrated to capture geochemical signals related to water balance variability in Laguna Negra, Argentina (Buongiorno, Gomez, Fike, & Kah, ), and microbialites from the Great Salt Lake, Utah, have been used to interpret biogeochemical fluctuations during the Pleistocene (Newell et al, ).…”

Domes, Rings, Ridges, and Polygons: Characteristics of Microbialites from Utah’s Great Salt Lake

“…This paper provides an introduction to the basic morphology of these unique structures and how local environmental conditions, as well as periods of exposure and erosion, contribute to growth location, grouping, shape, size, orientation, and internal structure. Several other research groups are exploring other important aspects including mineral precipitation mechanisms Pace et al, 2016), biogeochemistry/microbiology (Lindsay et al, 2016;Baxter, 2018), and possible age of formation and paleoenvironmental record (Newell et al, 2017;Vennin et al, 2019).…”

8200‐year growth history of a Lahontan‐age lacustrine tufa deposit

“…Porous freshwater carbonates known as tufas are observed in a variety of sizes (up to about 100 m tall and 0Á5 km 2 in area at Pyramid Lake) and morphologies in the Lahontan-age lake basins of the western United States; they have routinely been used for reconstructing palaeolimnological conditions (e.g. Benson et al, 1996;Petryshyn et al, 2016;Newell et al, 2017). However, tufa may form in a variety of lacustrine depositional environments, each of which may be geochemically distinct (Della Porta, 2015).…”