Cenozoic tectonic evolution of the Las Cruces area, New Mexico
— William R. Seager

The Las Cruces area (Fig. 1) is within the Rio Grande rift, both in the original restricted sense described by Bryan (1938) and Kelley (1952), and in the broader sense suggested by Chapin (1971). The present topography is dominated by intrarift uplifts and basins of late Cenozoic age, but these are super-imposed upon a variety of older, very different tectonic features of middle Tertiary and Laramide age. My objective in this article is to describe important tectonic elements of different ages to illustrate the evolution of tectonic styles and patterns through the Cenozoic.

Published work and unpublished ideas of many geologists were drawn from in assembling this summary. Among these, studies by Darton (1928), Dunham (1935), Kelley and Silver (1952), Kottlowski (1953, 1960) De Hon (1965), Reeves (1969), Ruhe (1967), Gile, Hawley and Grossman (1970), Dane and Bachman (1965), Bachman and Myers (1968), and Hawley and Kottlowski (1969) were used to supplement map-ping by Seager and others (1971), Clemons and Seager (1973), Seager and Hawley (1973), Seager, Clemons and Hawley (1975), Clemons (1975), Seager (1975), and Seager and Clemons (1975). Unpublished data from and discussions with John Hawley, C. E. Chapin, R. E. Clemons, W. E. Elston, F. E. Kottlowski, J. M. Hoffer, E. M. P. Lovejoy, LeRoy Corbitt, Clyde Wilson, and L. H. Gile comprise a basis on which much of the tectonic evolution of the area is interpreted.

Three major stages in the evolution of the area are recognized: Laramide uplift, middle Tertiary (Eocene-Oligocene) volcano-tectonics, late Tertiary (Miocene-Holocene) volcanism and rifting.