Geology and Paleontology of the Permian Area Northwest of Las Delicias, Southwestern Coahuila, Mexico

The Valle de Las Delicias, lying near the geographic center of Mexico, affords outcrops of Permian rocks more than 10,000 feet thick. The entire sequence can be measured in each limb of a truncated syncline. Although predominantly sedimentary, the succession includes much volcanic material in the form of agglomerate and graywacke, as well as thin lava flows and at least two great sills. The sedimentary beds are all marine and are abundantly fossiliferous at many horizons, ammonites and fusulines being exceptionally well preserved.