Development and deformation of Quaternary surfaces on the northeastern flank of the Jemez Mountains
— Charles D. Harrington and Aldrich, Merritt J., Jr.

The eastern Jemez Mountains volcanic pile overlies the western margin of the Espanola Basin, one of three en-echelon basins forming the central portion of the Rio Grande rift. The Jemez Mountains have served as a major source of volcanics (between approximately 13 and 0.13 m.y. ago; Gardner and Goff, this guidebook) and volcaniclastic materials (from approximately 10 m.y. ago to present) into this portion of the basin. The local basin dynamics therefore reflects not only regional tectonic events related to the development of the central rift, but also the more localized volcanic and tectonic pulses within the Jemez Mountains. During the Pliocene and Quaternary, a sequence of erosional surfaces developed along the northeastern flank of the Jemez Mountains. Their surfaces slope away from the mountains and grade toward the axial streams (Rio Chama or Rio Grande) of the Espanola Basin.

Studies of the Quaternary development of the Espanola Basin include investigations by Bryan (1938), Manley (1976), Kelley (1979), and Dethier and Manley (in press). In this paper we present a progress report on a tectonic—geomorphic study of an area west of Hernandez, New Mexico, in the northeastern Jemez Mountains—northwestern Espanola Basin (Fig. I).