Art. V.] Herrick, Geology of New Mexico. 107 
lead to give rise to productive mines. The ore concentration 
may be ascribed to the influence of the San Pedro crater and 
affords a beautiful illustration of the relation of metamorphism 
from local vulcanism to ore assemblage. On the west the limits 
of the Carboniferous are marked by an abrupt or even precipi- 
tous drop to the area of the valley occupied by a stream flow- 
ing north into the Rio Grande north of Bernalillo. Here the 
red sands and shales ascribed to the Jura-triassic lie in confused 
dip, the fragments being faulted in various senses. The Carbon- 
iferous again appears in irregular patches on the west side of the 
stream nearly horizontal in position and obviously forming frag- 
ments once continuous with the Sandia block. The whole area in 
this sheet east of the mountains and south of the Galisteo creek 
is an alluvial valley and seems to be underlaid by the Carbonifer- 
ous and possibly some of the later strata. It is the only part 
of this sheet that promises to afford artesian water and should 
such wells prove successful this beautiful valley will become the 
garden of the territory. 
5 , 
THE GEOLOGY OF SOUTH MOUNTAIN. 
The clustre of peaks by the above name is at the southern 
end of the series of rather isolated mountains lying east of the 
Sandias and faces the extensive valley forming the eastern part 
of the sheet. From this valley it rises abruptly and the granite 
core soon breaks through the fringe of sedimentary strata at 
the base, and rises in bare crags to over 8000 feet. A lobe of 
the valley to the eastward passes westward immediately to the 
south of the mountain giving to it an isolated appearance from 
all directions, though to the west it extends in a series of lower 
hills of granite, schist and gneiss nearly to the town of San 
Antonito. About the eastern base there are perhaps a hundred 
feet of red sandstone "which probably is of Jura-triassic age. 
These strata dip away from the main peak at a slight angle. 
To the west it is the Carboniferous limestone that skirts the 
base. These limestone strata extend far up the western foot 
hills and are much titled and faulted. The north and south vah 
