GEOLOGY OF TE WHITE SANDS OF NEW MEXICO 117 
The eastern escarpment of the Andreas is bold and irregular 
in the extreme but the fault which created it seems to have been 
wavy so that a crenulated or sinuous aspect is presented to the 
plain. The granite in some instances seems to have escaped in 
pinnacled or columnar form and throws off the restraining influence 
of the stratified rock to appear in jagged peaks. This is partic- 
ularly true in the Organ Mountains where, however, there must 
be added the influence of a later trachytic overflow. Our exam- 
ination of the San Andreas was cursory but was sufficient to show 
that the thickness of the stratified series is greater than in the 
Sandias and Manzanos. The lower portion is composed of 
quartzites and silicious shales which may be compared with the 
quartzites in the Manzanos. Above this is a large series of gray 
cherty limestones and quartzites of an entirely different texture 
and appearance. This has baffled our search for fossils in the 
Andreas and the Caballos where it is also well developed but, 
fortunately, we have been able to discover in the upper part of 
this series on the eastern side of the salt plain fossiliferous bands 
which place the age beyond doubt. Spirifer Grimesi, Leptaena 
rhomboidalis and other well-known Burlington brachiopods are 
associated with crinoids of that period in great abundance. 
Some of the bands are practically composed of the débris of the 
crinoids. 
Above the Burlington there seems to be a hiatus, for the 
next species encountered are distinctively Coal Measure forms 
and the sequence from this on to the top is as in the ranges 
farther north though there seems to be a tendency for the lime- 
stone to encroach on the sandy elements and for the individual 
components to thicken toward the south, a fact which we inter- 
pret as indicating deep-sea conditions. 
Attention has elsewhere been called to the method of occur- 
rence of the copper found so widely scattered through these 
ranges. It was shown that the deposits of copper which have 
attracted so much attention were formed in veins that extend 
from top to bottom of the sedimentary series but do not seem to 
cut the granite, at least to any depth or with any regularity. 
