A previously reported time-stratigraphic framework suitable for evaluating stratigraphic changes in the deeply buried oil shales of the Piceance Creek basin was developed by correlating lithologic and oil yield data. This Bureau of Mines report summarized the major features of the framework and explains some of the terminology applied to the Green River Formation. In cores from the central part of the basin, 3 major lithologic zones are recognizable: (1) a basal freshwater shale unit equivalent to the Garden Gulch and Douglas Creek Members; (2) a middle unit, the Parachute Creek Member, composed of dolomitic oil shales; and (3) an upper clastic unit, the Evacuation Creek Member. The Parachute Creek Member contains the major part of the oil shale resource. In the north central part of the basin the lower part of the Parachute Creek Member includes an evaporite sequence characterized by a unique suite of saline minerals. The time-stratigraphic framework is essential for understanding the vertical and lateral variability of the oil shale resource and the distribution of the saline minerals.