Charles Warren Merriam 1963 The Inyo Mountains near Cerro Gordo comprise strongly folded and faulted sedimentary rocks ranging in age from Ordovician to Middle Triassic. These were intruded by granitic bodies, aplite dikes, and by innumerable andesitic and dacitic dikes of later age. Though largely nonfoliated, the sedimentary rocks have undergone varying degrees of contact and hydrothermal metamorphism productive of hornfels, calc-hornfels, phyllite, and quartzite. application/pdf 10.3133/pp408 en United States Government Printing Office Geology of the Cerro Gordo mining district, Inyo County, California reports