New Mexico Geological Society
Fall Field Conference Guidebook - 36
Santa Rosa-Tucumcari Region

Spencer G. Lucas and Jiri Zidek, eds, 1985, 344 pages.

On 22 September 1853, Jules Marcou spent four hours studying the stratigraphy and paleontology of an isolated butte he called Pyramid Mountain, an outlier of the Llano Estacado about 13 miles southwest of the present site of Tucumcari. Marcou's subsequent publication of his studies, particularly his assertion that the strata under most of the western plains of North America are of Jurassic age, initiated a scientific debate that lasted almost 40 years. It also put the geology of east-central New Mexico on the scientific map. 132 years later, east -central New Mexico is still on that map as one of the classic Mesozoic terranes of western North America. This guidebook, and the field conference it elucidates, explore this terrane and the challenging problems it poses for the stratigrapher, paleontologist and sedimentologist.

The first-day road log is from Santa Rosa to Bull Canyon, Ragland, Tucumcari, Ute Dam, Mosquero and Trementina. This tour of the plateaus and canyons east and northeast of Santa Rosa emphasizes (1) Triassic and Jurassic stratigraphy; (2) the Ogallala Formation on the Llano Estacado; (3) the history of geological study of east-central New Mexico, especially the works of Jules Marcou; (4) the stratigraphic relationships of the Triassic of east-central New Mexico and the Dockum Group of western Texas and (5) the history of the Canadian River.

The second-day road log is from Santa Rosa to Newkirk, Variadero, Trujillo, Las Vegas, Tecolotito, Anton Chico, Dilia and back to Santa Rosa.This tour visits the canyons and plateaus north of Santa Rosa with a focus on (1) the Chinle Formation, especially the Cuervo Membe; (2) Jurassic and Cretaceous stratigraphy along the Las Vegas Plateau and southeastern flank of the Sangre de Cristo Mountains and (3) Permo-Triassic stratigraphy.

The third-day road log is from Santa Rosa to Sumner Lake, Fort Sumner, Vaughn, Pastura and Vegas Junction. This trip visits the plains and valleys south of Santa Rosa and focuses on (1) the Santa Rosa Formation; (2) Quaternary stratigraphy and sedimentation in the Upper Pecos Valley and adjecent areas; (3) karst and solution subsidence; and (4) Permian stratigraphy.

Papers from this guidebook are available for download from the NMGS website.