130 
UTAH PENEPLAINS 
and the Great Plains surface is not due entirely to orographic 
movements, as Davis contends, but that it is partly, perhaps, the 
result of erosional activities under the peculiar stimulus of aridity. 
In view, then of the known complexities of recent diastrophic 
oscillations over the Rocky Mountain tract, the erosion peculiarities 
of excessively dry climate, and the multiplex character of plana- 
tion effects the adjustment of the Great Plains surface to the 
Summit Plain is entirely precluded as both too simple and too 
recent. 
The terreplein of the Mesa de Maya lies about 3500 feet above 
the present general plains-surface. It is 2000 feet above the 
Raton plain which marks the base of the Tertic column; and 
6000 feet above the Corazon peneplain and the Dakotan sand¬ 
stone, at the bottom of the Cretacic section. The Mesa de Maya 
plain is preserved only in a few very restricted flats between 
Trinidad and Raton. 
The Raton Range, of which the Mesa de Maya is a part, is a 
long, narrow mountain ridge disposed at right angles to the Rocky 
Mountain axis. It extends from the Rocky Mountain front to the 
Texas line a distance of 130 miles, the crest having a gradient 
of one per cent, or 50 feet to the mile. In this distance from 
the Rockies the flatness of the top, as displayed by the Mesa de 
Maya is soon lost. The Maya plain doubtless bows upwards be¬ 
fore the Front Range is reached in the same way as does the 
Corazon unconformity plain. This being the case the level of the 
Maya planation over the mountains is something more than a mile 
above the Rocky Mountain summit. Its normal position is high 
above the tops of Long and Pike Peaks. It cannot be adjusted 
to the Summit flats, above which the peaks mentioned rise. 
The position of the Raton level and the base of the Tertic 
beds is more easily traced westward along the Raton Range than 
the crestal flat of the Maya. Like the Corazon unconformity 
the old Raton plain also turns up against the Rockies. Although 
not strictly parallel with the Corazon peneplain the Raton sur¬ 
face doubtless follows it closely in bending over the Cordilleran 
folds. Its position over the crest of the Rocky Mountains is 
still well above the summit of Long Peak. 
Like the Mesa de Maya planation the Raton plain cannot be 
brought into accord with the Summital Plain. 
