FRAMEWORK OF ARIZONA 
247 
Ransome) is not reported from the eastern field; nor is the ex¬ 
tensive upper portion of the section, together with an undetermin¬ 
able thickness which has been removed through recent erosion, 
probably represented in Texas. If the Ransome title Cintura is 
to be retained for any part of the Comanchan series in Arizona, 
it will have to be severely restricted to the uppermost beds, those 
above the thick sandstones of the Bisbee section. These sand¬ 
stones will probably be found to represent the capping of the Cerro 
de Muleros, west of El Paso, and could doubtless be advantag¬ 
eously designated the Muleros sandstone, numbers 10 and 11 of 
the Bose section. 
Scarcely one-tenth of this maximum section of 5,000 feet and 
over is strictly thalassic deposition, so that, in considerating the 
taxonomy of the Comanchan succession, it cannot possibly be re¬ 
garded more than a provincial expanse and hence an ordinary 
standard series. With the wealth of organic remains which the 
terranes carry there are few rock sections that would yield more 
satisfactory and constructive results in the differentiation of the 
faunal zones. 
In northern Arizona, and over the southern Rocky Mountain 
regions. Early Cretacic time is a period of profound erosion. 
When deposition again sets in it is with a heavy deposition of shore 
materials. The basal Dakotan series is one of the remarkable 
sandstones of the world. There are few other sandstones known 
which are so extensive. In one single layer its lowermost mem¬ 
ber extends from the Grand Canyon to Lake Superior, a distance 
along its southern outcrop of 2,000 miles. 
As displayed in the Arizona country the Dakotan series does 
not present the incomparable, massive sandstone that characterizes 
much of its range elsewhere. Conglomerate beds are common at 
the base. At Pyramid Butte, the conglomerate is exceptionally 
well marked, and this name is attached to this phase. Shales and 
coals occur in the formation. Besides these two phases other beds 
come in in the neighboring states, so that the entire sequence as¬ 
sumes an importance stratigraphically that the massive, single bed 
might not readily indicate. Plant remains are the most abundant 
forms of life. 
The Coloradan series, of the eastern slope of the Rocky Moun¬ 
tains, appears to be represented on the west side by thick sections 
