Upper contact of Meseta Blanca sandstone member of Yeso formation revised--Yeso formation here divided into two members, Meseta Blanca sandstone member (at base) and Los Vallos member (named in this report) at top. Los Vallos constitutes the bulk of Yeso formation. Meseta Blanca underlain by Abo formation; Los Vallos overlain by Glorieta sandstone member of San Andres formation. Meseta Blanca areally extended into Socorro and Valencia Cos, NM, Orogrande and San Juan basins; generally mappable in Valencia Co, but thins to south and not generally mappable south of Monte de Belen, Socorro Co, Orogrande basin. Los Vallos member underlies west Los Vallos and forms the lower slopes of east face of Sierra Lucero in a broad belt extending from west edge of area in T5N into head of Carrizo Arroyo, Valencia Co, San Juan basin. Still farther north forms floor and slopes of wide inner valley of Santa Fe Arroyo and head of Garcia Arroyo. Small outcrops near Monte de Belen in tributaries of Red Tanks Arroyo. Yeso is of Permian age. Measured sections, cross sections, geologic map.

Source: GNU records (USGS DDS-6; Denver GNULEX).

A new member, Torres member, named. Yeso formation divisible into two mapped units: 1) the Meseta Blanca sandstone member at the base; and 2) the overlying undifferentiated Torres, Canas, and Joyita members. Meseta Blanca overlies Abo formation. Joyita, the uppermost member, underlies Glorieta sandstone member, basal member of San Andres formation. Yeso mapped at southwest and south-central to northeast part of area in Socorro Co (Orogrande basin) and in Torrance Co (Estancia basin). Cross sections. Of Leonard, Early Permian age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Named as the basal member of the Yeso formation. Type section designated in sec 3, T16N, R2E, near Canon and area to north in Canon de San Diego grant, Sandoval Co, NM in the San Juan basin. Source of geographic name not stated. Mapped in southeast part of map area. Geologic map; cross sections. Overlies Permian? Abo formation. Underlies the newly named San Ysidro member of Yeso. Intertongues with Abo to north and tongues into Cutler formation in vicinity of Senorito Canyon in Sandoval Co. Consists of light-orange or red, tangentially cross-bedded [sandstone]. Weathers to rounded and overhanging cliffs. Ranges from 0 to 390 ft thick. Assigned a Permian age.

Source: GNU records (USGS DDS-6; Denver GNULEX).

Sandstones named Meseta Blanca Sandstone Member of the Yeso Formation in the Nacimiento Mountains north of Albuquerque, NM, Sandoval Co, San Juan basin, are equivalent to Permian De Chelly Sandstone of the Cutler Group in Zuni Mountains and Defiance uplift, McKinley and Valencia Cos, San Juan basin. The De Chelly and the Meseta Blanca are flat-bedded and thinly bedded siltstone or very fine sandstones that were deposited in a subaqueous and probably marine environment. Term De Chelly has precedence over Meseta Blanca. Regional use of one name will clarify relationship of the De Chelly and the Yeso. Cross sections. [Author suggests preference for De Chelly, but does not abandon Meseta Blanca.] Yeso treated as a unit restricted by removal of De Chelly-type sandstones from it.

Source: GNU records (USGS DDS-6; Denver GNULEX).