PENNSYLVANIAN FORMATIONS IN THE RIO GRANDE 809 
are thin-bedded limestone and dark-blue shale. Occasionally, a thin 
bed of sandstone may be seen. At Kingston, on the east slope of the 
Black Range, the basal beds consist of about 300 feet of dark-blue 
and gray limestone in thick beds with thin shale partings. ‘The 
upper portion has about the same thickness and consists chiefly of 
blue and drab shale interstratified with several limestone formations 
varying from fifteen to twenty feet in thickness. Resting uncon- 
formably upon the shale formation are the red sandstones and shales 
of the Manzano group. 
At Palomas Camp, in the Black Range, twenty-five miles north 
and a little west of Hillsboro, the county seat of Sierra County, and 
two miles east of Hermosa, the Rio Palomas has cut a gorge 1,000 feet 
deep through the sedimentary formations. The walls of the canyon 
are nearly vertical and consist almost wholly of blue and gray lime- 
stone of the Magdalena group. The lower half of the escarpment 
consists of limestone and shale in about equal development, while 
the upper portion is made up of hard, massively bedded gray lime- 
stone. About half-way up the cliff a few thin beds of quartzite appear 
interstratified with limestone. The overlying Red Beds of the Man- 
zano group, together with some of the upper beds of limestone, have 
been removed by erosion at this point, but the red sandstones occur 
in considerable development a short distance to the northwest. 
In the Caballos Mountains, about twenty-five miles east of Hills- 
boro, the group is represented chiefly by limestones, with some shale 
beds in the basal part, as at Hermosa, but we are unable to give details 
of the formation at this locality. They were observed resting with 
apparent conformity upon other limestones considered to be of Lower 
Carboniferous age, while below these, and separated from them by a 
thin bed of the Percha shale (Devonian), is a heavy development of 
limestone (goo ft.) belonging to the Mimbres formation (Ordovician). 
The data at hand concerning these formations in Sierra County are 
insufficient to warrant an attempt to subdivide the group. The char- 
acter of the beds at Hermosa suggests the twofold division observed 
farther north, and in connection with the character of the formations 
in adjoining districts indicates a gradual transition in sedimentation 
from shallow-water conditions at the north to deeper waters toward 
the south. With the progress of time the entire region apparently 
