Abstract
The disposition of the Ouachita-Marathon orogenic belt as it extends through west Texas into Mexico has been the subject of diverse interpretations. However, an explanation developed earlier for the general shape of the Ouachita-Marathon orogenic belt in the southern United States, which was based on the relation of craton margin to direction of Paleozoic plate motion, is adequate to account for the belt's puzzling disposition upon entering Mexico. It is suggested that crustal thickness, gravity, and geologic data indicate that the orogen follows the shape of the craton margin, which swings around a reentrant south of the Marathon region and extends southward into Mexico. In Mexico the orogen apparently ends in association with the westernmost of the Ouachita-Marathon zones of transform offset.
