Tectonics and metamorphism of the El Oro gneiss dome near Mora, north-central New Mexico
— Antonius J. Budding and J. C. Cepeda

The area under consideration is a part of the Sangre de Cristo Mountains between Mora on the north and Rociada on the south. The rocks dealt with in this article are of Precambrian age; the overlying Paleozoic rocks and extensive cover of Quaternary alluvium will not be discussed in detail.

 

Precambrian rocks are exposed widely in the Sangre de Cristo Mountains of New Mexico. Between the latitudes of Santa Fe and Mora, and west of the Picuris-Pecos fault (Miller and others, 1963), the exposed rocks are nearly all Precambrian in age, but east of the fault, an extensive cover of Phanerozoic rocks obscures the Precambrian rocks to a great extent. The Precambrian outcrops near Mora, that form the basis of this study, are part of a discontinuous belt of Precambrian rocks that includes the Rincon Range and the El Oro Mountains, and continues to south of El Porvenir. The present study is re- stricted to the Precambrian of the El Oro Mountains and adjacent Precambrian terrain between Mora and Rociada.

 

The general elevation of this area is between 2,150 and 2,600 m (7,100 and 8,500 ft). The area of Precambrian exposures is characterized by sharp peaks, ridges and narrow canyons. Vegetation, which can be quite dense on north-facing slopes, includes pinon and ponderosa pine, Douglas fir, aspen, and scrub oak. The higher parts of the mountains have a dip-slope topography, cut, on the gently dipping upper Paleozoic rocks, which unconformably overlie the Precambrian. The major valleys are flat or gently sloping, and are underlain by Quaternary and possibly older valley fill.