Cenozoic rocks of New Mexico are wholly continental in origin and contrast markedly with most pre-Cenozoic deposits. Extensive stratigraphic and paleontologic work facilitates correlations and paleoenvironmental reconstructions; less extensive sedimentologic and petrologic studies allow detailed reconstructions of dispersal patterns and provenance locally. The accompanying papers summarizing recent research on the Cenozoic of New Mexico provide many new insights concerning paleontology, sedimentology, stratigraphy, and tectonics.
The Cenozoic history of New Mexico can be divided into three phases on the basis of plate-tectonic events affecting the southwestern United States and styles of deformation, magmatism, and sedimentation in local areas. The Paleocene and Eocene were characterized by amagmatic basement deformation (Laramide orogeny), resulting in complex uplifts and basins, followed by widespread beveling. Massive outpourings of intermediate to silicic volcanics characterized much of the state during the Oligocene. The Neogene (Miocene to Holocene) has been characterized by extensional tectonics and bimodal volcanism, best expressed by the Rio Grande rift. Local sedimentary and paleontologic histories of the numerous Cenozoic basins of New Mexico reflect these regional tectonic processes.