Brief summary of the Tertiary geologic history of the Rio Grande rift in northern New Mexico
— Kim Manley

The Rio Grande rift of Colorado and New Mexico can be divided into a series of structural basins. Within one of these basins (the San Luis Valley), from the New Mexico state line southward, is the Taos Plateau (Fig. 1). Adjoining it to the south is the Espanola Basin. The boundary between is marked by the termination of the Taos Plateau volcanic field and the presence of a basement ridge (Cordell, 1978) crossing the rift from the Picuris Range, through the Precambrian exposure at Cerro Azul, to the La Madera area (Fig. 2).

This paper presents an overview of the Tertiary history of the Taos Plateau, the northernmost Espanola Basin, and parts of the adjacent Tusas Mountains to the west and the Sangre de Cristo Mountains to the east.