244 
FRAMEWORK OF ARIZONA 
regions. If the two are considered together, as parts of a single 
province, the Supaian succession would then correspond to the 
Productive coal measures of the East — probably representing 
the thick Arkansan series on the south side of the Ozarks. Al¬ 
though the typical Supaian section of the Grand Canyon region 
does not afford workable coal deposits and even presents few 
traces of the mineral fuel, deposits of good coal actually occur in 
the southeastern part of the state, in the Chiricahua Mountains, as 
first announced by Dumble many years ago, a fact indicating 
that the formation is really part of the Coal Measures. 
The remnantal coal measures of the Chiricahua District have 
a counterpart in New Mexico where, northeast of Socorro, isolat¬ 
ed patches of coal and associated measures containing typical coal 
plants are known as the Alamito shales. Doubtless these coal 
measures were once extensively developed in the Southwest; but 
the tremendous peneplanation which this region suffered imme¬ 
diately before the great limestone formations were laid down 
swept away all but a few lingering traces. 
The Aubreyan series of limestones, a thousand feet or more in 
thickness, constitutes the chief surface rock of the Colorado Dome. 
The section becomes thicker towards the east, until, in eastern 
New Mexico, it attains in the Hueco limestone a measurement of 
over 3,000 feet. This giant plate of limestone flanks the southern 
Rocky Mountains. In Kansas it is probably approximately, if 
not exactly, represented by the interbedded limestones and shales 
composing the Missourian and Oklahoman series. If so, it is 
traceable quite to the Mississippi River. To the westward of 
Arizona this limestone extends far into Nevada where it assumes 
different names. 
The minor, or formational, units are probably as well exhibited 
in the Grand Canyon as anywhere else in the region. 
The Aubreyan limestone plate seems to rest at the Grand Can¬ 
yon in strict conformity upon the beds beneath. No other rela¬ 
tions are recorded. Appearances here are somewhat deceptive. 
In reality a notable hiatus exists at the base of this series. An ‘ 
erosional interval becomes more and more noticeable to the east¬ 
ward until all of the Paleozoics, Proterozoics, and Archezoics are 
brought into touch with it. Such erosion is not, perhaps, on so 
vast a scale as at first sight might appear, since other orographic 
