Early Holocene Great Salt Lake, USA

Abstract

Shorelines and surficial deposits (including buried forest-floor mats and organic-rich wetland sediments) show that Great Salt Lake did not rise higher than modern lake levels during the earliest Holocene (11.5-10.2 cal ka BP; 10-9 14 C ka BP). During that period, finely laminated, organic-rich muds (sapropel) containing brine-shrimp cysts and pellets and interbedded sodium-sulfate salts were deposited on the lake floor. Sapropel deposition was probably caused by stratification of the water column -a freshwater cap possibly was formed by groundwater, which had been stored in upland aquifers during the immediately preceding late-Pleistocene deep-lake cycle (Lake Bonneville), and was actively discharging on the basin floor. A climate characterized by low precipitation and runoff, combined with local areas of groundwater discharge in piedmont settings, could explain the apparent conflict between evidence for a shallow lake (a dry climate) and previously published interpretations for a moist climate in the Great Salt Lake basin of the eastern Great Basin.

Microbialite response to an anthropogenic salinity gradient in Great Salt Lake, Utah

“…Adding to the effects of salinity, mirabilite deposits on the lake bottom or in the subsurface from past extreme drought conditions contribute to salinity and nutrient supply to GSL (Anderson et al, 2014;Oviatt et al, 2015), perhaps influenced by the faults cross-cutting the lake bottom ( Fig. 1A) (Velasco, Bennett, Johnson, & Hreinsdóttir, 2010).…”

“…While the abundance of ions is higher in the NA than the SA, the composition of ions is similar between these two areas (Domagalski, Orem, & Eugster, ). Adding to the effects of salinity, mirabilite deposits on the lake bottom or in the subsurface from past extreme drought conditions contribute to salinity and nutrient supply to GSL (Anderson et al., ; Oviatt et al., ), perhaps influenced by the faults cross‐cutting the lake bottom (Fig. A) (Velasco, Bennett, Johnson, & Hreinsdóttir, ).…”

“…Other than the most extensive Northern Hemisphere glaciations which formed the larger Lake Bonneville, the current GSL area (Fig. 1A,B) and its characteristics are likely similar to what they have been the last 780 ka (Oviatt, Madsen, Miller, Thompson, & Mcgeehin, 2015;Oviatt, Thompson, Kaufman, Bright, & Forester, 1999) or even longer (Charles Oviatt, pers. comm).…”

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

“…During the Pleistocene, lake systems in the Great Basin of the western U.S. fluctuated in response to glacial and interglacial cycles, and varied in size and chemistry from deep freshwater lakes to shallow hypersaline systems (e.g., Benson et al, ; Oviatt et al, ). During the latest cycle in this series, Lake Bonneville and GSL have integrated hydro‐climatological variations for the eastern Great Basin since ∼30 cal (calendar years) ka (e.g., Benson et al, ; Currey, ; Gilbert, ; Oviatt, ; Oviatt et al, ). During this period, Lake Bonneville size responded to Northern Hemisphere climate fluctuations including multiple large transgressive and regressive periods, followed by regression to GSL levels between 15 and 13 cal ka (Figure ) (Oviatt, ).…”

“…GSL levels have also fluctuated, although to a lesser magnitude, through the Holocene. The last major transgression was the Gilbert episode (to ∼1,295 m asl) during the Younger Dryas (∼11.5 – 11.6 cal ka) (Oviatt et al, ), and the lake has regressed at least once to ∼1,274 m asl (Bouton et al, ; Currey, ; Murchison, ), which is lower than the historic lake low stand of 1277 m asl achieved in late 2016. The modern low stand is due in part to anthropogenic water diversion, thus the prehistoric low stands may indicate conditions much drier than today, and could be associated with the mid‐Holocene climate optimum (Dean et al, ).…”