Marine Paleozoic Rocks of Mexico

Abstract

Rocks of all Paleozoic systems are present in Mexico and, from north to south, are distributed in several basins: Sonora-Pedregosa basin (including the postulated Palomas-Villa Ahumada platform), Chihuahua basin, main Paleozoic geosyncline and Tlaxiaco subbasin, and Chiapas-Guatemala basin. The maximum known thickness of Paleozoic strata is estimated to be about 3,500 m. Data are too few to make reliable and detailed isopach and lithofacies maps of the Mexican Paleozoic. Sections studied and measured to date indicate that, of all the systems, the Silurian is the most poorly represented. Early Devonian strata are unknown. The Cambrian and Ordovician Systems are developed best in northern Mexico, but fossiliferous Cambrian, Ordovician, and Carboniferous strata recently were discovered for the first time in Oaxaca, southern Mexico. The Mississippian, Pennsylvanian, and Permian are the most widespread Paleozoic systems. Most Paleozoic rocks in which fossils are preserved were deposited in shallow-water environments. Deeper water lithofacies have been found in strata of middle and late Paleozoic ages, and their predominance in eastern Mexico suggests that the seas of those times were open toward the Gulf of Mexico. The paleogeographic maps show the relations between the basins and platforms of the southern United States and their equivalents in northern Mexico. Paleozoic strata are drilling objectives in some areas of Mexico, particularly in the north-central part.