The Piceance Basin forms a geologic structural basin, and is the source of commercial oil and gas production. Separated from the Uinta Basin by the Douglas Creek Arch, both basins formed during the Laramide Orogeny, and are bounded by the Charleston-Nebo thrust fault, the Uinta Basin boundary fault, and the Grand Hogback monocline. According to the USGS Uinta-Piceance Assessment Team, The black-shale facies of the Green River Formation is the main petroleum system of Tertiary age whereas the Mahogany zone of the Green River Formation is a minor component. The Cretaceous Mancos Group and equivalent rocks are the main source of Cretaceous oil and a major contributor of gas in the basin, whereas the Upper Cretaceous Mesaverde is a lesser contributor of oil but a significant source for gas. Ferron Sandstone coals are known to be a source of coalbed methane. The most prominent source of oil from Paleozoic rocks is the Permian Phosphoria Formation.