The area discussed is in the S.-Central Uintah County and N.-Central Grand County, Utah. Seven shallow core holes were drilled in the area to evaluate the oil-shale beds of the Mahogany Zone and to determine the approximate position of the 15-ft isopach for the oil-shale sequence with an average yield of 15 gal of shale oil per ton. Sandstone beds immediately above and below the Mahogany Zone also were cored in order to sample those beds that contain bitumen. The cores were examined and described and cores from sequences containing appreciable amounts of kerogen or bitumen were assayed by the Fischer retort method. The core drilling was done by Wildcat Drilling Service, Inc. of Montrose, Colo., and the assaying was done by the Colorado School of Mines Research Institute, Golden, Colo.