From abstract: Mafic and ultramafic xenoliths in the Western United States are present in volcanic rocks ranging from lamprophyric to dacitic in composition and are found in every major tectonic province from the Coast ranges from California to the Great Plains. Xenoliths from 68 localities are described here, but new localities are being discovered, and much remain to be learned about their distribution with respect to the tectonic and geophysical framework of the Western United States.

From abstract: The La Jencia fault is a recently reactivated late Cenozoic basin margin structure of major proportions that forms the western margin of the Rio Grande rift, which borders the eastern sides of the northern Magdalena Mountains and the southern Bear Mountains in central New Mexico. Stratigraphic throw on the fault has not been determined, but Precambrian rocks of the Magdalena Mountains are uplifted a minimum of 800 m (meters) above the adjacent basin floor, below which lie a thick section of upper Cenozoic basin-fill deposits. Most of the implied displacement is probably Neogene in age.