Geologic map of the Rio Puerco quadrangle, Bernalillo and Valencia Counties, New Mexico

The Rio Puerco quadrangle is located southwest of Albuquerque in central
New Mexico and covers part of the western part of the Isleta Reservation.
The U.S. Geological Survey, the New Mexico Bureau of Geology and Mineral
Resources, and the University of New Mexico have conducted geologic
mapping on the Isleta Reservation and vicinity as part of the Middle Rio
Grande Basin Project. The map area contains surficial deposits, calcic
soils, fluvial deposits of the Rio Puerco, deposits of the Santa Fe Group,
and three volcanic fields. The area is characterized by predominantly
north-trending normal faults with generally down-to-the-east movement.

Post-Santa Fe Group deposits are composed of surficial deposits
(Pleistocene-Holocene) and fluvial deposits of the Rio Puerco
(Pleistocene-Holocene). The surficial deposits are divided into eolian,
alluvial, colluvial, and landslide deposits. The fluvial deposits of the
Rio Puerco consist of four terrace and present channel deposits.

The Santa Fe Group is divided into lower and upper parts. The lower part
of the Santa Fe Group is exposed near the southwestern corner of the study
area where deposits consist of reddish-brown mudstone and sandstone
correlated to the Popotosa Formation (Unit 1) of Lozinsky and Tedford
(1991). They interpreted deposition of the unit in a basin-floor playa
setting. The Popotosa Formation is in fault contact to the east with
deposits of the upper Santa Fe Group. The upper Santa Fe Group is derived
from major tributary fluvial systems (ancestral Rio Puerco Puerco and
possibly the Rio San Jose drainages) draining the adjacent Colorado
Plateau and Sierra Nacimiento and correlated to parts of Kelley's (1977)
Ceja Formation of the Santa Fe Group and equivalent to Machette's (1978)
Sierra Ladrones Formation, Connell's Arroyo Ojito Formation (Connell and
others, 1999, and Maldonado's lithofacies of the Isleta Reservation
(Maldonado and Atencio,1998a, b). The group also locally includes a fine-
grained unit (lower Pleistocene) referred to here as the sand, silt, and
clay of Chavez Grant (Qsc). The Ceja Formation of the Santa Fe Group as
defined here is divided into the following units in descending
stratigraphic order: (1) upper sand and gravel unit (upper Pliocene), (2)
middle silt, sand, and clay unit (upper Pliocene), and (3) lower sand and
gravel unit (Pliocene).

The three volcanic fields in the map area are: (1) basalt of Cat Hills,
dated at 98-110 ka and composed of seven lava flows and four cinder cones;
the flows overlie calcic soils that overlie the upper sand and gravel unit
of the Ceja Formation; (2) lava flow of Cat Mesa, dated at about 3 Ma and
interfingers with the upper part of the Ceja Formation; (3) diabase of
Mohinas Mountain, dated at 8.3 Ma (Baldridge and others, 1987) and
intrudes the Popotosa Formation.

Numerous high-angle faults cut the area but are mostly buried. The faults
generally trend north but deviate to the northwest and northeast. The
major normal faults are the Cat Mesa and Mohinas Mountain faults.