Second-day road log, from Santa Fe to Pecos, Rowe, Bernal, Romeroville, and Mineral Hill
— Paul W. Bauer, Christopher G. Daniel, Spencer G. Lucas, James M. Barker, and Frank E. Kottlowski

Today's tour from Santa Fe to Las Vegas traverses much of the stratigraphic section, from 1.7 billion year old gneisses to Cretaceous shales of the Raton Basin. Our stops will emphasize (I) the geometry and kinematics of the Picuris-Pecos, Garcia RanchBorrego, and Tijeras-Caiioncito fault systems, (2) Early Proterozoic metamorphic rocks of the southern Sangre de Cristo Mountains, (3) environmental concerns and remediative efforts along the Pecos River, (4) Paleozoic stratigraphy, (5) Laramide faults and folds, (6) the Mesozoic section on Glorieta Mesa, and (7) the Cretaceous rocks of the Raton Basin.

From Santa Fe, we proceed eastward on 1-25 across Quaternary-Tertiary deposits and high geomorphic surfaces into the southernmost Proterozoic rocks of the Sangre de Cristo Mountains. At Stop I, east of Cafioncito, granitic and tonalitic gneisses that appear to have intruded mafic country rock as the crust was being actively deformed, were later extensively faulted and fractured during Phanerozoic tectonism. Three major fault systems, the Tijeras-Caiioncito, Garcia Ranch-Borrego, and Picuris-Pecos, all intersect near Stop 1. The timing and nature of the displacement across these fault systems will be our primary focus. The faults have a complex movement history and ongoing studies are debating the timing and kinematics of faulting. As many as six or seven episodes of fault activation (and reactivation), ranging in age from Proterozoic to Neogene, have been suggested.

We continue eastward to Pecos, then tum northward where the Pecos River has exposed the great unconformity between Paleozoic sedimentary strata and Early Proterozoic rocks of the Pecos complex. At Stop 2, we examine the deformed 1.7 Ga Windy Bridge tonalite, discuss Paleozoic stratigraphy and tectonics of the southern Sangre de Cristo Mountains, and consider environmental problems along the Pecos River associated with long-abandoned mining operations at the Pecos Mine.

The road log next takes us southward down the Pecos River, past Pecos National Historical Park, towards Glorieta Mesa, where we ascend the mesa to examine the Artesia/Moenkopi Formation (formerly Bernal Formation) disconforrnity at Stop 3. We rejoin 1-25 eastward to Stop 4, near Bernal, where we will discuss the Lower Permian Sangre de Cristo Formation, the Permian-Triassic disconformity, and the Laramide-age Bernal fault. As we continue northward on 1-25, we travel up-section, crossing a variety of Laramide faults and hogbacks until encountering Cretaceous shales of the Raton Basin. The Laramide-age "Crestone hogback" at Stop 5 consists of steeply west-dipping Permian to Cretaceous strata that mark the boundary between the Sangre de Cristo Mountains and the flat-lying rocks of the Las Vegas sub-basin of the Raton Basin. Just north ofRomeroville, we exit westward towards Mineral Hill for the final stop of the day, a spectacular vista of the southern Sangre de Cristo Mountains.