Great Salt Lake, Utah: A Natural Laboratory for Assessing Potential Geobody Dimensions, Reservoir Architectures, and Controls in Lacustrine Carbonate Systems

Abstract

Great Salt Lake represents the largest known lacustrine carbonate deposystem in the world and provides a unique opportunity to assess carbonate sedimentation as a potential analogue for many ancient basins. Located in an arid environment, the hydrologically-closed and recently dissected lake has limited siliciclastic input, limited groundwater recharge, no significant hydrothermal input, and its waters are at saturation or supersaturated with calcium carbonate. An aragonite ooid and microbialite-dominated carbonate lacustrine environment predominates and covers over 4,000 square kilometers. Continuing research reveals that microbial bioherms populate more than ¼ of the existing lake floor and occur as dispersed to laterally-connected forms, ranging from centimeters to over 2m in diameter, with relief up to 1.5m. They are extensively developed on topographic highs, occurring on the footwalls of small faults and in shoaling areas, and indicate a sensitivity to water depth and associated factors such as wave energy, light availability, substrate type, and sedimentation. Ooid shoals dominate many shorelines and the supra-littoral zones are commonly veneered by oolitic intraclast breccias. A rock-filled causeway limits the supply of fresh water available to the north part of the lake causing halite precipitation and the cessation of microbialite development at salinities approaching 26%. Great Salt Lake is a high energy, ramp-margin system and predicting what might enter the stratigraphic record is highly speculative. Preservation potential of microbial deposits in the lake depends, in large part, on the hydrologic balance. The present ooid-microbialite sediment veneer could be preserved under salt, pelagic sediments, or eroded during an extended lowstand. Comparisons of benthic and sub-bottom lithologies north and south of the causeway provide clues as to possible methods of preservation or destruction for microbialite deposits in modern and ancient lacustrine carbonate deposystems.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017