Some relationships among folds, faults and mid-Tertiary igneous rocks near Gallup, northwestern New Mexico
— Marvin L. Milgate

Field relationships of folds, faults and intrusive igneous rocks near Gallup, New Mexico suggest a mid-Oligocene (about 31 my ago), northeasterly structural trend that might prove useful in analyzing structural and tectonic elements of the southeastern Colorado Plateau. The trend consists of extensional features, an assemblage of faults and minette dikes and plugs imposed across northwest-trending folds of ostensible Laramide age (about 75 to 40 my). A mid-Oligocene stress field containing a northwest-southeast minimum principal stress direction is indicated. A diatreme discovered south of known minette outcrops is tentatively included in the Twin Cones volcanic field (Hackman and Olson, 1977), within the minette province of Shoemaker (1956). Assuming age compatibility, the diatreme occurrence extends the volcanic field about 3.6 km to the southeast.