FRAMEWORK OF ARIZONA 
239 
throughout the area of Arizona fall easily into satisfactory place 
like so many dominoes. Not a single incongruous element reveals 
itself. It is further demonstrated that the great Aubreyan series 
of limestones, which in the southern Rocky Mountains rests di¬ 
rectly upon the pre-Cambrian crystallines, is laid down upon an old 
peneplanal surface, which to the southwest bevels all the various 
Paleozoics down to Cambric levels. Thus, the Cambric, Ordovicic, 
Siluric, Devonic and Mississippian rocks must have originally ex¬ 
tended over the southern Rocky Mountain tract, and hence this 
area could not have been a continental island throughout all the 
long span of Paleozoic time, as is so often urged. 
Fully one-half of Cambric time in southwestern United States 
is unrepresented by deposition. All of the Early Cambric, and a 
considerable portion of Mid Cambric sediments, are missing; and 
a major unconformity marks the base of the Paleozoic section of 
this region. The Cambric sequence of the Grand Canyon, to which 
sole attention is usually given, is very incomplete. There are en¬ 
tire provincial series missing at the top, doubtless once present 
here, as they now are in the southeastern part of the state, in 
the Chiricahua Range, but long since removed through erosion, 
and perhaps peneplanation, during Ordovicic and Siluric times. 
Proneness to give new sets of names to the rocks of every min¬ 
ing camp results in a copious and tedious synonomy among forma- 
tional titles without the compensatory advantages of careful delimi¬ 
tation, and the terranes themselves thus escape close correlation. 
Owing to neglect to take into account the terranal significance of 
the later epochs of erosion suggested parallelism of the several 
Cambric formations is mainly erroneous and badly needs a new 
start with something more than flimsy reconnaissance as a basis. 
Cambric serial terminology of New Mexico is strictly applic¬ 
able to Arizona. Both states have many included formations yet 
unnamed. 
Ordovicic rocks are poorly represented in Arizona land. They 
are now absent over all the central part of the state. They may 
have once spread over an ancient Colorado Dome, but if they did, 
all concrete evidences of the circumstance are now removed, be¬ 
cause of the prodigious erosion and, possibly, peneplanation of 
the region in times immediately preceding the Siluric, and also the 
Devonic Periods. In the eastern part of the state about 400 feet 
