Temporal and Spatial Variations in Lacustrine Depositional Controls from the Middle to Upper Green River Formation, Central and Western Uinta Basin, Utah

Leah Toms, Lauren Birgenheier, and Michael Vanden Berg
1059 East 600 South, Apartment 5, Salt Lake City, UT

Upstream and downstream climatic and tectonic controls on fluvial-lacustrine systems contribute to the fluctuation of sediment and water entering lake basins. In addition, the relative balance between these controls affect the spatial distribution of deposited sediments and the resulting stratigraphic architecture seen in outcrop and core. The stratigraphy preserved in the lacustrine Eocene Green River Formation provides key insights into the evolution of ancient Lake Uinta and the controls influencing sediment deposition and facies distribution. Specifically, this study characterizes the sedimentology and stratigraphy of the middle to upper Green River Formation (C marker to the Horsebench Sandstone) from outcrop and core in Gate Canyon, south-central Uinta Basin, and Indian Canyon, western Uinta Basin. The examined sections were deposited during the hyperthermal events that followed the Paleocene-Eocene Thermal Maximum, allowing specific investigation of how climate change may have influenced facies distribution, stratigraphic architecture, and lake evolution. Detailed outcrop and core descriptions along with paleocurrents, X-ray fluorescence data, and thin sections in both the central and western portions of the basin reveal distinct suites of facies from each region. The central portion of the basin contains both siliciclastic and carbonate facies whereas the western portion of the basin contains primarily carbonate facies with zones of saline mineral deposition. The lack of siliciclastic deposits near Indian Canyon suggests a much lower terrestrial sediment supply and a more profundal, hypersaline environment. In addition, littoral microbialites and carbonate grainstones present near Gate Canyon are largely absent to the west. This data suggests variations in the dominant depositional processes controlling each area. Overall, this study seeks to link these regions to provide a more comprehensive understanding of the evolution of Lake Uinta, highlighting the spatial and temporal changes in upstream and downstream controls across the basin.

AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62^nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013