ABSTRACT

The Parras Basin, in southern Coahuila and western Nuevo Leon, Mexico, contains on the order of 17,500 feet (5300 meters) of Late Cretaceous (Gulfian) and Tertiary (Midwayan) calcareous - arenaceous - argillaceous sediments which were deposited in a shallow, subsiding basin between the present area of the Sierra Madre Oriental in the south and the Coahuila Platform on the north.

The sediments of the Parras Basin were deformed during Paleocene or Eocene times by the same forces which effected the adjacent Sierra Madre Oriental. Three areas of differing deformational intensity and characteristics were developed in the basin--1) an area of broad, open, domal folds in the north and east; 2) an area of broad, open, elongated folds in the southeastern segment; and 3) an area of tight, elongated, partly overturned folds in the more constricted western portion of the basin. The duration of the orogenic stresses is unknown, but subsequent uplift of the folded and faulted basin area occurred, exposing the sediments to vigorous erosion.