Microbialites and Microbial Mineralization in the Great Salt Lake, Utah

Abstract

The Great Salt Lake (GSL) is host to extensive microbialite deposits that, at least in some regions of the lake, host an active mixed community of cyanobacteria, algae, microbial heterotrophs, sulfate reducers, insect larvae, and other organisms. The macrostructure, interior structure, and microfabrics of the microbialites are highly variable in different locations, and the chemical, physical, and biological mechanisms of their formation is an area of active research. Understanding the processes and environments that form different microbialite structures (and microstructures) is critical to the interpretation of the extensive putative microbialite fabrics in pre-salt deposits. Here, we present the results and ongoing research of Weber State University undergraduate students working on projects focused on different aspects of carbonate precipitation in GSL. A thorough analysis of carbonate geochemistry in the vicinity of “active” microbialites at Ladyfinger Point on Antelope Island was completed, including a study analyzing the influence of the calcium-charged, brackish groundwater that seeps through the microbialites at Ladyfinger Point. Preliminary results suggest conditions locally supersaturated for aragonite, implying that at this location modern aragonite precipitation can occur abiogenically. In addition, laboratory experiments with modern microbialite surface communities suggest that the biological community does not appreciably facilitate carbonate precipitation, although it may serve as a template for mineralization. Additional analyses are being done to assess the genetic and enzymatic capacity of the microbialite surface and interior microbial communities to facilitate carbonate precipitation. Finally, biocementation experiments are being carried out to assess the capacity of GSL microbial communities to cement the ooid sands of GSL. The latter experiment is part of a larger investigation of Microbially Induced Calcite Precipitation (MICP) in local sediments and rocks of economic interest, including rocks of the Uinta Basin. MICP has been shown to enhance oil recovery in porous rocks. Permeability measurements from MICP experiments with GSL ooid sands and porous Uinta Basin rocks of economic interest will also be presented here.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018