Pre-Carboniferous Paleozoic Rocks in Central Chihuahua, Mexico: GEOLOGICAL NOTES

Abstract

Nearly 2,000 ft. of pre-Carboniferous rock ranging in age down to and including the Early Ordovician have been discovered. This rock has undergone considerable structural deformation, predominantly folding, but regional metamorphism has not proceeded further than recrystallization of the limestone. In the southeastern part of the range, an estimated 2,000 ft. of Pennsylvanian and Permian rock has been found, much of it Wolfcampian. The total thicknesses of Paleozoic rocks exposed in Texas at Marathon, Shafter, Van Horn, and El Paso, and in Chihuahua at Mina Plomosas are listed. In the Plomosas vicinity as at El Paso both thickness and composition indicate shelf deposits. The Plomosas formation near Mina Plomosas is about 5,000 ft. thick, including about 4,000 ft. of Paleozoic and 1,000 ft. of Jurassic rock. The Pb and Zn deposits are in the Jurassic part.