Jeuiez — Albuquerque, N. Mex. — Regan. 73 
many miles in a north and south direction ; and often shows 
a thousand feet of displacement. This uplifted tongue of lava- 
capped Eocene strata is the southern prolongation of the 
Cochiti range. 
At no place where examined did rocks older than Tertiary 
lie upon the flank of this range ; but it is said that on the east 
side, which part was not visited, Cretaceous and even earlier 
stratified rocks are found. The faulting of the Eocene on the 
south of the range and the elevating of the same, indicates 
that these mountains were re-elevated after the close of that 
epoch. 
The Plateau. — Turning now to the main plateau of the 
Jemez mountains, the writer will state that he has visited but 
little of it. This plateau is often spoken of as the basaltic pla- 
teau, but the basalt seems to be more on the flanks of the 
mountain than on the plateau. The central portion of the 
plateau, like that of its extended rim, is feldspathic porphyry 
(granite). On this, in the Valle Grande country, there is at 
least 400 feet of rhyolyte in situ over which is tufa varying 
in thickness from forty to a h'undred and forty feet in its 
original position. Pelada is the culminating point in these 
mountains. 
The San Dia Mountains. — To use the words of professor 
Jenks- "The central core or axis of the San Dias is generally 
granite, a metamorphic or changed rock of Archean age." The 
San Dias are everywhere capped with Carboniferous strata. 
Sedimentary Deposits. 
The sedimentary deposits of this region, beginning with 
the Carboniferous, are : 
Carboniferous. 
There are two Carboniferous districts ; one in the 
San Dia uplift, the other in the arch of the Jemez uplift. 
The former was not examined closely by the writer, except at 
a point north of Tejon where several specimens of Prodnctns 
punctatus were found. The Carboniferous of the Jemez moun- 
tains is patchy. Th,e patches flank the mountains within the 
arch from near Jamez peak to the vicinity of the soda dam. 
They have an altitude of about 7000 feet at their upper term- 
inus. The formation in the southern patch reaches as far east 
