PENNSYLVANIAN FORMATIONS IN THE RIO GRANDE 813 
formation is a limestone conglomerate the pebbles of which were 
derived from the underlying Madera beds. Above this, as seen in 
the hills east of Socorro, is a coarse red granitic quartzite conglomerate. 
The thickness of the red sandstone division varies from 400 to 800 
feet. Overlying these beds occur alternating strata of yellow, pink, 
and white sandstones and shales with lenses of gypsum and a subor- 
dinate amount of limestone. In places the gypsum is massive and 
reaches a thickness of 140 feet. The total thickness of this forma- 
tion ranges from 500 to 1,000 feet. ‘The uppermost division of the 
Manzano group consists for the most part of gray limestone in which 
an abundant fauna occurs. These beds are well developed in the 
mountains east of Socorro and southward in the San Andreas Moun- 
tains east of Engle, but were not observed on the west side of the Rio 
Grande. According to Lee this limestone is not present in the Sandia 
Mountains. The total thickness of the formation is. from 300 to 
500 feet. Several miles northeast of Socorro, and in plain sight from 
this place, are a number of minor elevations called the Coyote Buttes. 
At this locality the Manzano beds are well exposed in the west face 
of the hills, the strata dipping sharply to the northeast. The red 
sandstones of the lower division occur on the west of the Magdalena 
Range south of Kelly and along the east side of the Black Range from 
Fairview south to Kingston. The overlying beds were not observed 
in the Black Range region. 
Heretofore these red-sandstone formations have been at times 
confounded with the Red Beds supposedly of Permian and Triassic 
age, but according to Dr. Girty,t who has made a study of the fossils 
collected from them by Mr. Willis T. Lee, of the Survey, they are 
undoubtedly Upper Carboniferous and correspond in their relations 
to the upper part of Richardson’s Hueco formation in Texas and the 
Aubrey in the Grand Canyon region. 
In the Mount Taylor region, sixty miles west of the Rio Grande, 
there are 1,200 feet of Upper Carboniferous red and yellow sandstones, 
according to Dutton, who identified them with the Aubrey and used 
that name for them. 
Nomenclature—While there have been published a great many 
papers relating to the region under consideration, very little detailed 
t Personal communication. 
