Memoir 29—Geology of Sandia Mountains and vicinity, New Mexico

By V. C. Kelley and S. A. Northrop, 1975, reprinted 1982, 1995, , 136 pp., 4 tables, 92 figs., 2 appendices, 4 sheets.

Comprehensive coverage of rocks and formations, structure, paleontology, stratigraphy, geologic history, and mineral resources. Discusses caves and artifacts, historical geologic surveys and early mining operations; also includes such environmental problems as landslides and earthquakes. Contains a topographic map, structure map, structure sections, and color geologic map.

The Sandia Mountains area is dominated by an eastward-tilted fault block that stands imposingly above the deep Rio Grande trough on the west. Structural relief from uplift to trough is as much as 6 mi; into the basins to the east and northeast relief is 2.5–5 mi. The most unusual structure of the area is the Tijeras rift belt bounding the uplift on the southeast. This belt, 2–3 mi wide, 16 mi long, trending northeastwards, consists mainly of two longitudinal parts: a southwestern folded graben and a northeastern horst. Tijeras rift belt is principally a Laramide feature as are a few other faults along the eastern flank of the late Tertiary Sandia uplift.

Precambrian rocks, prominent in the bold western fault scarp, consist of granite, gneiss, schist, quartzite, and greenstone. Sedimentary rocks range in age from Mississippian to Cretaceous within and immediately flanking the mountains. Thick sequences of early and late Tertiary sediments lie in order above the Cretaceous in the Hagan Basin northeast of the uplift. The section is 16,000 ft thick exclusive of the late Tertiary and Quaternary trough-filling Santa Fe Formation.

The long east- to northeast-tilted homocline from the Sandia uplift into the Hagan Basin contains most of the formations of central New Mexico, and is the most complete sequence in the state. Stratigraphic units consist of 1) marine Mississippian and Pennsylvanian shelf beds, 2) continental Permian, Triassic, and Jurassic red beds formed under flood-plain, evaporitic, lacustrine, and eolian environments, and 3) intertonguing marine and flood-plain Cretaceous beds of the Rocky Mountain geosyncline.

The Sandia Mountains area covers 400 mi² within six 7.5-min quadrangle east and northeast of Albuquerque. The Sandia Range is the dominant feature, but part of the Manzanita Mountains south of US-66, Tijeras Basin, Monte Largo (east of the Sandias), Hagan Basin (northeast of the Sandias), and an edge of the Rio Grande depression are all included in the geologic map and text. Two principal highways, Intestate 40 (including US-66) and NM-14 roughly quarter the area. Additionally, NM-44 crosses the northern part of the mountains and provides access to the crest.

The area contains most of the significant Paleozoic to Cenozoic stratigraphic units and a varied representation of the Precambrian rocks of central New Mexico; important stratitectonic relationships are observable there that bear on the understanding of the origin of the Rio Grande depression and of the Sandia Mountains. The area is particularly important to Albuquerque, the major city of New Mexico, with respect to environment, recreation, urban development, and esthetics.