86 GEOLOGY. 
In all that portion of New Mexico passed over by our party I saw no other rocks immediately 
overlying the variegated marls than such as I regarded as the equivalents of those given in the 
preceding section. From the Moqui villages to Santa Fé the line of junction of these two 
formations was visible on almost every part of our route; and while I do not feel at liberty to 
enter upon the mooted question of the geological age of the superficial strata on the Llano 
Estacado, a region I have never visited, I am compelled to say that west of the Rio Grande the 
yellow sandstones overlying the red and white gypsiferous marls and calcareous sandstones (the 
upper portion of the variegated maris) belong to the Cretaceous series, and are identical with 
those just described. 
As far as we progressed north of the Moqui villages we were travelling upon the strata forming 
the cliffs on which they are built. The valleys of erosion which traverse the plateau every- 
where expose its structure, permitting the different formations to be readily distinguished, even 
at a distance of thirty or forty miles. 
At Camp 96, the point where we turned back, the view down one of these valleys, which 
leads toward the Colorado, was particularly interesting. Its smooth surface, tinged with green 
by a sparse growth of Artemisia and Ephedra, was bounded for several miles by the cut edges of 
the Cretaceous sandstones on which we stood. The erosion then reached the surface of the Marl 
series, and thence to the distance of forty or fifty miles we could see walls and pinnacles of red 
and white rising abruptly from the green plain, producing the peculiar scenery of the Painted 
Desert. At a greater distance we could trace the outlines of lower mesas, growing less and less 
distinct, till eighty miles away the view was bounded by the lofty line of the snowy mesa first 
seen from Camp 72. This mesa fills sixty degrees of the horizon from this point, and termi- 
nates in the awful precipice overhanging the Little Colorado, sharply defined and grand even 
at this distance. Toward the northeast the Cretaceous rocks, after continuing for several miles 
nearly horizontal, were seen to rise rapidly and cover the flanks of a line of hills—spurs of the 
first of the Rocky mountain ranges. Eastward our view covered a large part of the country 
lying between us and Fort Defiance, and showed everywhere a geological structure similar to 
that prevailing in our immediate vicinity. South and southeast we overlooked the entire extent 
of the Painted Desert and the valley of the Little Colorado, beyond which rose the snowy 
summit of the San Francisco mountain, still a grand and beautiful object, though separated from 
us by an interval of a hundred miles. All that was wanting to fill up that interval to the level 
of a line drawn from our position to the base of the San Francisco mountain had been removed 
in the formation of this great valley of erosion—a much grander monument of the power of 
aqueous action than even the stupendous cafion of the Colorado. 
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ig. 22.—DISTANT VIEW OF GREAT WHITE MESA, FROM NEAR CAMP 96. 
_ Upper Cretaceous strata.—Some miles north of Camp 96 a mesa wall rises to a height 
which we estimated at something like twelve hundred feet. It occupies 30° of the horizon in 
that direction, and shows bold, nearly perpendicular faces, both in profile and in front. These 
are pure white in color, and reflect the sunlight like snow. Compelled by the want of water, 
with extreme regret we turned our backs upon this interesting geological feature, leaving its 
