176 
The American Geologist. September, iyo4 
continuous in the same straight Hne to the north, for the 
Oscuro mountains, which are almost the direct northward 
continuation of the San Andres, form the other hmb of the 
anticline, dipping east instead of west, there being a region of 
sharp flexture about a short axis or pivot near the north end 
of the San Andres, giving rise to the Little Burros mountains. 
North end of San Andres Range. 
The conditions reoresented in this little sketch are of suffi- 
cient interest to permit a remark. It would appear to the 
casual observer that the Oscuro and San Andres mountains, 
separated by the Mocking Bird pass, ^orm part of the same 
system, but even hurried geological examination reveals the 
fact that the dip is in opposite senses and that the region of 
the pass is a part of neither the Oscuro nor the San Andres 
system but forms a distinct element. When compared with 
the Oscuros it is faulted so that the ba^e of the Carboniferous, 
or at least the granite contact which is some 1500 ft. above 
the plain in the south end of the Oscuros, drops in the Little 
Burros to, and in some places below, -he general level. What 
is more surprising is the fact that a part of the north end of 
the San Andres is involved in this Little Burro mass. The 
f^ult represented north of Capitol peak has not been studied 
closely and may not extend through the range as represented. 
At any rate, the Carboniferous hills of the Little Burro block 
