First-day road log from Las Cruces to Derry Hills and Mescal Canyon in the Caballo Mountains
— Greg H. Mack, Timothy F. Lawton, and Katherine A. Giles

The first day of the field conference follows a route from Las Cruces to Truth or Consequences along 1-25. The goal of the first day is to examine parts of the Paleozoic and Mesozoic sedimentary sections and discuss depositional environment and basin evolution. The first stop is in the Derry Hills, where the Pennsylvanian Magdalena Group and Permian Abo Formation are exposed in a late-rift (latest Miocene-Pliocene) fault block. We will examine the uppermost formation of the Magdalena Group, the Bar B Formation, whose mixed carbonate and siliciclastic facies will be placed in the context of sequence stratigraphy. At the end of the foot log traverse, the basal part of the nonmarine Abo Formation is exposed. The Magdalena Group and Abo Formation at this location were deposited on the western margin of the Orogrande Basin, one of the major north-trending basins of the Ancestral Rocky Mountains deformational belt. Dramatic thickness changes, intraformational unconformities, and the presence of conglomerates in the Magdalenaa and Abo provide important insight into the tectonic history of the basin.

The afternoon stop in Mescal Canyon, east of Truth or Consequences is devoted to examination of Upper Cretaceous sliliciclastic sedimentary rocks. These exposures, which represent the most complete Upper Cretaceous section in southern New Mexico, include the Dakota, Mancos, Tres Hermanos, D-Cross, Gallup, and Crevasse Canyon Formations. A variety of shallow marine, shoreline, and nonmarine depositional environments are represented and are arranged into two large-scale transgressive-regressive cycles, which will be placed in the context of sequence stratigraphy. The Mescal Canyon section will be compared to sections in the San Juan Basin and farther north and will be discussed in the context of the evolution of the Sevier fold and thrust belt and the complementary Western Interior foreland basin.