Pliocene and Quaternary stratigraphy, soils, and tectonic geomorphology of the northern flank of the Sandia Mountains, New Mexico: implications for the tectonic evolution of the Albuquerque Basin
— Sean D. Connell and Stephen G. Wells

We use geologic mapping, stratigraphy, and soil morphology of Pliocene and Quaternary deposits along the northwestern flank of the Sandia Mountains, central New Mexico, to interpret the late Cenozoic tectonic evolution of the eastern margin of the Albuquerque basin. The relative activity of basin-margin and intrabasinal faults is evaluated by cataloguing offset of piedmont and fluvial deposits that are unconformable with the syn-rift basin fill of the Santa Fe Group. The piedmont associated with western and northern flanks of the Sandia Mountains marks a transition between the northern Albuquerque and Santo Domingo sub-basins. The distribution of piedmont and Santa Fe Group basin-fill deposits records basinward migration of fault activity across a 6.5-km east step in the rift-margin, resulting in increased relief and subsequent dissection of older basin fill on the hanging walls of the Placitas and San Francisco faults. Along this transition, the piedmont is deeply dissected and exposes some of the oldest rift-basin fill and pre-rift rocks. South of this transition, along the relatively steep and linear western front of the Sandia Mountains and Rincon Ridge, the piedmont is only slightly dissected, and middle Pleistocene and Holocene deposits typically bury Santa Fe Group and older deposits. According to Russell and Snelson (1990,1994), the northern Albuquerque basin is controlled by a major, mostly buried, west-dipping, listric-normal fault named the Rio Grande fault. Their Rio Grande fault began during the late Miocene as the locus of rift-border faulting migrated basinward, resulting in displacement of 4-6 km of Cenozoic basin fill. Stratigraphic and geomorphic evidence does not support the presence of such a throughgoing, large-displacement structure in the study area. We interpret basinward migration of normal faulting as only a local feature, created in part, by the prominent east step between the Santo Domingo and northern Albuquerque sub-basins.