New Mexico Geological Society
Fall Field Conference Guidebook - 40
Southeastern Colorado Plateau
Orin J. Anderson, Spencer G. Lucas, David W. Love and Steven M. Cather, eds., 1989, 345 pages.
Our volunteer field trip committee again has targeted a geologically interesting and scenic region. The journey begins on the alluvial fans west of the Sandia Mountains, across the Rio Grande to the first stop in the Rio Puerco fault zone, then to sandstone pipes in the Jurassic rocks west of Mesita, on to the spectacular setting of Acoma Pueblo and hence north to the Cretaceous-Jurassic contact and with a final stop southeast of Grants on NM-117, just south of I-40, to examine Jurassic-Cretaceous strata overlooking the Quaternary malpais. Day 2 begins on the west side of Cebolleta Mesa at the Sandstone Bluffs overlook and southwest to an aggregate pit to see structures related to the Hickman fault zone, then southwest to Techado where the Tertiary Baca Formation overlies the Cretaceous Moreno Hill Formation with an extensive paleoweathering zone at the contact. Then to the major stop of Moreno Hill on the southern margin of the Colorado Plateau to discuss structure and physiography, the Salt Lake coal field, and to note at the outcrop the contrast with the Cretaceous strata to the north in the Zuni Basin. A fitting climax is stopping at the D. Y. Mountain ancient -Zuni holy-place ruins of Dowa Yalanne to discuss the outcropping Jurassic rocks. On the third day, after an evening in Gallup, the conference goes a short distance to the east to see the structure and stratigraphy of the Hogback, then south to the Carbon No. 2 coal mine to discuss coal stratigraphy. After a stop south of Gallup along NM-602 to see the Bidahochi Formation, we continue south and then northeast to the magnificent exposures along the Hogback at Upper Nutria where the Glorieta, San Andres, Chinle, Entrada, Zuni-Cow Springs, Dakota, Mancos, Tres Hermanos, Pescado, Gallup and Crevasse Canyon units are spectacularly exposed, as well as the structures related to the Hogback. Then on the way eastward around the southern flank of the Zuni Mountains through Ramah to the final stop at Bandera Crater we travel northeast to Grants and join I-40 back to Albuquerque.