The Coso Formation is a geologic formation in the Coso Range of the Mojave Desert, in Inyo County, California.USGS.gov: "Age of the Coso Formation, Inyo County, California"
It preserves fossils dating back to the Neogene period. It yields fossil remains of many species of mammals, including of Equus simplicidens, the Hagerman Horse.
See also
List of fossiliferous stratigraphic units in California Paleontology in California
References
Bibliography