Selected samples of the Green River Formation, Colorado Core Hole No.1, were analyzed to aid characterization and understanding of the genesis of the oil shales of the Piceance Creek Basin, Colorado. About 120, 2-4 inch samples from the Parachute Creek and Garden Gulch Members were analyzed for 18 major and minor elements, 12 selected trace elements and quantitative mineral content. About 70 samples were scanned, perpendicular to the bedding, by electron microprobe to determine semiquantitative elemental microstratigraphy of nine selected elements.