Mesozoic stratigraphy of the Laguna-Grants region
— Charles H. Maxwell

Good exposures and vistas of most of the Mesozoic stratigraphic units, which are present in the southeastern part of the Colorado Plateau, crop out along the San Jose valley and along I-40 from Laguna to Grants, New Mexico. Along this route, the section starts with the Triassic Chinle Formation near Mesita (fig. 1), progresses through the Jurassic formations to Cubero, then through the Upper Cretaceous Dakota Sandstone and Mancos Shale, and back through the section to the Chinle at Grants. Cretaceous units above the Mancos Shale crop out in the regions north of Laguna and Grants, and Permian units are exposed in the region south of Grants. Typical outcrop characteristics are visible along I-40 and on the mesas which flank the San Jose valley. This valley is roughly parallel to some major facies changes in the Jurassic and Cretaceous rocks and to three areas of truncation of underlying units by angular unconformities, all of which are discussed in the following pages.

 

This region has been studied for more than 100 years (Dutton, 1885; Herrick, 1900; Hunt, 1936; Pike, 1947; Silver, 1948; and many more). Detailed geologic map coverage for the Laguna-Grants area is shown on Figure 1.