New observations and tectonic inferences on the Mississippian-Lower Pennsylvanian strata in the Sierra Nacimiento-San Pedro Mountains-Jemez Mountains, north-central New Mexico
— Karl Krainer and Spencer G. Lucas, [eds.]

Abstract—In the Sierra Nacimiento, Jemez Mountains, and San Pedro Mountains of northern New Mexico, the Proterozoic basement is locally overlain by a thin succession of sedimentary rocks of Mississippian age. The succession is divided into the Arroyo Peñasco Formation that is 7.5–34 m thick in the studied sections and the overlying Log Springs Formation (9.2–13.5 m thick). The Arroyo Peñasco Formation is divided into the Del Padre and overlying Espiritu Santo Members. The Del Padre Member is thin and composed of poorly sorted, subangular, quartz-rich sandstone, indicating deposition in a fluvial environment. Microfacies of limestone of the Espiritu Santo Member indicate deposition in a shallow marine depositional setting. Foraminifers at Lion Spring indicate a Tournaisian (Kinderhookian-Osagean) age of the Espirtu Santo Member. The Arroyo Peñasco Formation is unconformably overlain by the Log Springs Formation (Serpukhovian/upper Chesterian), which is composed of nonmarine red beds. At Log Springs, the Log Springs Formation is unconformably overlain by the Lower
Pennsylvanian (Morrowan) Osha Canyon Formation. Limestones of the Osha Canyon Formation are composed of microfacies (rudstone,packstone, rare floatstone) that indicate deposition in a shallow, normal marine environment of moderate to high water turbulence. At Lion Spring, the Log Springs Formation is overlain by the Middle Pennsylvanian Sandia Formation; the Osha Canyon Formation is absent. At Soda Dam, the Sandia Formation rests on the Log Springs Formation, which overlies the Arroyo Peñasco Formation, and the Osha Canyon Formation is absent. This distinct unconformity at the base of the Sandia Formation, which at many places rests on Proterozoic basement, marks the onset of tectonic activity of the Ancestral Rocky Mountain orogeny.