DAVIS: THE PLATEAU PROVINCE OF UTAH AND ARIZONA. 9 
escarpment they are overlaid by evenly bedded horizontal calcareous 
strata. 
Wind action in an ancient desert seems more competent than any 
other agent to produce the observed structures, but we could not discover 
any critical and decisive proof of this suggestion. It would be difficult 
to select a more attractive problem in structural geology than would be 
_ offered to a student who should trace this extraordinary formation around 
its outcrops in the White cliffs until some demonstrable conclusion as to 
its origin should be reached. The dissection of the Jurassic platform 
back from the cliffs by obsequent, south-flowing streams gives abundant 
opportunity for viewing the curious structure of the sandstones. The 
little valley that our road followed southward gathers the drainage from 
a small area of open surface on the lower Cretaceous strata, gradually 
sinks below the Jurassic platform, and eventually joins the valley of 
Kanab creek near the ragged frontal escarpment. The cliffs, seemingly 
a good thousand feet in height, and the isolated dome-like outliers in 
front of them present long, smooth slopes of bare rock on which the lines 
of cross-bedding are beautifully and delicately engraved. The sandstone 
is so uniformly resistant that its slopes have no well-defined benches such 
as are usually developed in the weathering of horizontally stratified 
masses. Joints also have little influence here in guiding denudation. 
The cliffs have no ornamentation in the way of narrow clefts and slender 
pinnacles ; their contours sweep in curves of large radius, and even the 
smallest of the outstanding buttes are of imposing size. The sandstone 
seems to disintegrate chiefly grain by grain, for there is usually little 
coarse talus at the base of the massive cliffs. 
The canyon of Kanab creek through the Jurassic platform is followed 
by two basaltic flows that seem to proceed from a small cone a few miles 
to the north. The older flow, thirty or forty feet thick, forms a bench 
about eighty feet above the present valley floor where we saw it, and ends 
near the frontal escarpment. The younger flow forms the stream bed, 
where it is often buried in sand and gravel : it extends about a mile fur- 
ther south than the older one. 
Kanas Canyon. — The Triassic platform, with an altitude of 6000 
feet and a frontai relief of 1200 feet, is the southernmost of the great 
terraces by which the descent is made from the High plateaus to the 
broad upland in which the Colorado canyon is cut. Its frontal escarp- 
ment is known as the Vermilion cliffs, of which a characteristic view is 
given in Plate 2 B. The deep trench worn by Kanab creek through 
the Triassic platform is locally known as Kanab canyon, not to be con- 
