Correlation of Eocene rocks of the northern Rio Grande rift and adjacent areas--Implications for Laramide tectonics
— Spencer G. Lucas

The oldest Tertiary rocks in the northern Rio Grande rift are of Eocene age. These rocks—the Galisteo, El Rito, and Blanco Basin Formations— represent continental sediments that were shed from complex uplifts and deposited by rivers in adjoining basins as the result of an essentially amagmatic basement deformation, the Laramide orogeny (Chapin and Cather, 1981; Lucas and Ingersoll, 1981). For many years, the age of the basal Tertiary rocks in the northern Rio Grande rift was imprecisely known. However, recent stratigraphic, vertebrate paleontological, and sedimentological studies now permit a more refined correlation of these units, a correlation that suggests that there was a middle Eocene pulse of Laramide deformation in northern New Mexico. This paper reviews these recent studies, presents a revised correlation of the Eocene rocks of the northern Rio Grande rift, and briefly discusses the implications of this new correlation for the Laramide tectonic history of northern New Mexico.