Institution: | aU.S. Geological Survey, MS 980, Denver Federal Center, Lakewood, CO 80225, USA;bPonderosa Associates, 130 Miners Dr., Lafayette, CO 80026, USA;cU.S. Geological Survey, MS 963, Denver Federal Center, Lakewood, CO 80225, USA;dEOG Resources, 420 Throckmorton, Fort Worth, TX 76102, USA |