Microbialites
Microbialites are organic sedimentary lake or marine deposits that can indicate distinctive types of oil potential and reservoirs. Microbialites take several forms: thinly layered (stromatolites), clotted (thrombolites), spherical (oncolites), and precipitated from mineral-rich springs (tufa or travertine). The hypersaline environment of Utah’s Great Salt Lake is ideal for forming microbial mats, stromatolites, thrombolites, and other porous carbonate structures. Core samples from other areas in the state such as the Eocene-age Green River Formation display ancient examples of microbialites
Microbialites in Utah
Great Salt Lake is ideal for stromatolite formation and is home to some of the most extensive reefs of living stromatolites on Earth. The lake’s briny environment precludes organisms that would ordinarily graze or browse on nutritious stromatolites or burrow and bore into them. Additionally, a lack of animals minimizes stirring of sediments from the lake bed that would otherwise blanket stromatolites from sunlight. The absence of plants and scarcity of other algae on the lake floor also reduce competition for nutrients and space. They are most observable when lake level is near average elevation (4,200 feet) or lower and after planktonic algae have been grazed out by brine shrimp, making the water more transparent.
The lacustrine Eocene-age Green River Formation in the Uinta Basin, Utah, contains excellent examples of microbial carbonates—stromatolites, thrombolites, and grainstones—which can serve as analogues for highly productive nonmarine microbial reservoirs worldwide. The West Willow Creek field produces oil from a small microbial mound within the Green River Formation—the only such known field in the Uinta Basin. Microbialite heads often consist of stromatolitic crusts with thrombolitic internal characteristics. Oncolites are another significant component to the microbial system. The entire Skyline 16, Federal No. 15-24B from the West Willow Creek field, and other cores containing microbial carbonates, are available for examination at the Utah Core Research Center.
Antelope Island Flyover
The shallow waters of Bridger Bay, on the northwestern tip of Antelope Island in the Great Salt Lake, support extensive microbial carbonate formation, especially in the north-northeast portion of the bay near Egg Island. Lake levels in the fall of 2014 were near 60-year lows, giving unprecedented access to the microbial structures. Characterizing the microbialites of Bridger Bay can inform interpretations of similar deposits in the ancient rock record, including potential petroleum reservoirs.
Publications, Abstracts, and Presentations
Microbial Carbonate Reservoirs and Analogs from Utah
Thomas C. Chidsey, Jr, David E. Eby, Michael D. Vanden Berg, and Douglas A. Sprinkel
UGS Special Study 168
Unexpected abundance and diversity of phototrophs in mats from morphologically variable microbialites in Great Salt Lake, Utah
Mert Kanik, Mason Munro-Ehrlich, Maria Clara Fernandes-Martins, Devon Payne, Kathryn Gianoulias, Lisa Keller, Alexander Kubacki, Melody R. Lindsay, Bonnie K. Baxter, Michael D. Vanden Berg, Daniel R. Colman, Eric S. Boyd
Domes, Rings, Ridges, and Polygons: Characteristics of Microbialites from Utah’s Great Salt Lake
Michael D. Vanden Berg, The Sedimentary Record, March 2019
Petrography and characterization of microbial carbonates and associated facies from modern Great Salt Lake and Uinta Basin’s Eocene Green River Formation in Utah, USA
from Microbial Carbonates in Space and Time: Implications for Global Exploration and Production
Characterization of Microbialites in Bridger Bay, Antelope Island, Great Salt Lake, Utah
Michael D, Vanden Berg, Thomas C. Chidsey, Jr., Davis E. Eby, and Wayne Kelln
Presented at the International Limnogeology Congress 2015, June 15-19, 2015, Reno, NV.
Marine Microbial Carbonate Facies, Fabrics, and Petroleum Reservoirs in Utah
by David E. Eby, Thomas C. Chidsey, Jr., and Douglas A. Sprinkel
Presented at the Rocky Mountain/Cordilleran Section Meeting of Geological Society of America, May 18-20, 2014, Bozeman, MT.
Modern and Ancient Microbial Carbonates in Utah, U.S.A.: Examples from Great Salt Lake and the Uinta Basin’s Tertiary (Eocene) Green River Formation
by Thomas C. Chidsey, Jr., David E. Eby, Michael D. Vanden Berg
Presented at The Geological Society (London) Microbial Carbonates in Time and Space: Implications for Global Exploration and Production Symposium, June 19-20, 2013, London, England.
Microbial Carbonates in Cores from the Tertiary (Eocene) Green River Formation, Uinta Basin, Utah, U.S.A.: Analogues for Non-Marine Microbialite Oil Reservoirs Worldwide
by Michael D. Vanden Berg, David E. Eby, Thomas C. Chidsey, Jr., and Michael D. Laine
Presented at The Geological Society (London) Microbial Carbonates in Time and Space: Implications for Global Exploration and Production Symposium, June 19-20, 2013, London, England.
Microbial Carbonates from Core and Outcrop, Tertiary (Eocene) Green River Formation, Uinta Basin, Utah
by David E. Eby, Thomas C. Chidsey, Jr., Michael D. Vanden Berg, and Michael D. Laine
Presented at the American Association of Petroleum Geologists Annual Convention, April 22-25, 2012, Long Beach, CA.
