Formations in ascending order above an unnamed basal Wolfcamp formation are the Abo, Yeso, Glorieta, and San Andres. Relations across the state are shown by three cross sections.

The Abo consists of red and brown thin-bedded shales and medium-bedded sandstones, with arkoses; it shows ripple marks, mud cracks, salt casts, cross-bedding, tracks and remains of vertebrates, and plant impressions; it is non-marine. The thickness is about 650 feet near Socorro and increases to 900 or 1,000 feet near Alamogordo.

The Yeso consists of gypsum, pink and light-colored silts and sands, and limestones. Limestone increases from less than 6 per cent in the Zuni Mountains to more than 25 per cent in the Sacramento Mountains. Some of the members can be traced for scores of miles. The formation is mainly marine in origin. The thickness is about 620 feet at the type locality near Socorro and increases to more than 1,100 feet near Alamogordo.

The Glorieta is a clean light-colored heavy-bedded medium-grained resistant sandstone 135 feet thick at Rowe on Glorieta Mesa. It is about 70 feet thick east of Socorro

End_Page 907------------------------------

and thins to a feather edge in the San Andres and Sacramento mountains. It is probably marine in origin.

The San Andres is gray to pale-buff medium- to heavy-bedded limestone about 350 feet thick at the type locality in Rhodes Canyon. It thins to 20 feet on Glorieta Mesa and disappears north; its relations to the overlying Permian southeast are not well understood. A sand zone in the lower part is traceable from the Zuni Mountains to Hondo Canyon 225 miles southeast. At the north the San Andres is overlain by pink silts and sands of unknown age.

End_of_Article - Last_Page 908------------