Paper No. 7
Presentation Time: 10:30 AM

DEPOSITIONAL ENVIRONMENT OF THE WANAKAH FORMATION IN THE WESTERN COLORADO REGION: AN ANALOG STUDY FOR LACUSTRINE PETROLEUM SYSTEMS


DEPRIEST, Keegan, Physical and Environmental Sciences, Colorado Mesa University, Grand Junction, CO 81501, POTTER-MCINTYRE, Sally L., Parkinson Lab - Geology Department, Southern Illinois University, 1259 Lincoln Drive, Carbondale, IL 62901, BORAAS, Marisa, Dept. of Geosciences, Colorado State University, 400 University Ave, Fort Collins, CO 80523 and ASLAN, Andres, Department of Physical and Environmental Science, Colorado Mesa University, 1100 North Avenue, Grand Junction, CO 81501, depriestkl@gmail.com

The Jurassic Wanakah Formation is exposed in western Colorado and functions as a seal that overlies the permeable Entrada Sandstone. Previous studies assign either a marine or lacustrine depositional environment to the unit; this study tests the hypothesis of a hypersaline lake origin. Petrography, QEMSCAN, XRD, whole rock analysis and stable isotopes are used to evaluate the petrography, mineralogy, and geochemistry to document lateral lithofacies variability and construct a regional stratigraphic cross-section. Sedimentary and petrophysical properties within the Wanakah Formation in western Colorado suggest a hypersaline lake system that records subaqueous deposition, meters-thick horizons of gypsum precipitation, saturated and exposed paleosol development and fluvial and shoreline sandstones. Lateral variability on an outcrop-scale within the Wanakah Formation suggests that any petroleum system that includes lacustrine units must be evaluated on a fine scale to ensure a comprehensive picture of the system.