--> Exploring Utah's Other Great Lake: What Great Salt Lake Can Tell Us About Ancient Lake Uinta

AAPG Pacific Section and Rocky Mountain Section Joint Meeting

Datapages, Inc.Print this page

Exploring Utah's Other Great Lake: What Great Salt Lake Can Tell Us About Ancient Lake Uinta

Abstract

Many similarities exist between the modern Great Salt Lake and Eocene Lake Uinta, the latter of which is recorded in the lacustrine deposits of the Green River Formation in the Uinta Basin, Utah. Characteristics of both lake environments include shallow-water ramp margins that are susceptible to rapid, widespread shoreline changes, as well as comparable water chemistry and temperature ideal for microbialite growth and formation/deposition of associated carbonate grains. In particular, comparisons were made regarding: 1) the often discontinuous nature of microbialite formation, 2) the origin of pustular grains found between microbialite heads, 3) the formation of unique, crystal-like structures on the tops of microbialite domes, and 4) the formation of giant, thickly layered microbialites. In addition, we have explored how cold water springs and microseeps might be a critical component in microbialite formation in both modern and ancient settings. Several processes at Great Salt Lake that influence unique microbialite formation were also explored including: 1) desiccation of saline-saturated muds and the formation of microbialite ridges, 2) erosion processes that facilitate the creation of strange microbialite ring structures, and 3) the preferential formation of microbialites on the outer edges of large desiccation polygons. These features, yet to be formally recognized in the Green River Formation, give insights to the multitude of processes involved in microbialite morphology. Since lacustrine facies and microbialites can act as excellent hydrocarbon reservoirs (e.g., the West Willow Creek oil field in the Uinta Basin produces from a Green River Formation microbial buildup/mound), it is important to develop a better understanding of modern microbialite formation as a basis for understanding ancient microbial carbonate reservoirs in Utah and worldwide.