GEOLOGY OF MOQUI COUNTRY. 77 
throughout the Painted Desert, and usually caps the walls of sandstone already described, to 
the deep red of which its lighter colors afford a strong contrast. As these marls occupy so 
large a part of the country traversed by our party between the Little Colorado and Rio Grande, 
I shall have occasion frequently to refer to them. 
On our way to the Moqui villages we passed through a region singularly favorable for accu- 
rate geological investigation; where there is no vegetation to impede the view; where the 
strata are entirely undisturbed, and are cut by valleys of erosion, in the wall-like sides of which 
every inch of the series may be examined. In this journey we ascended in the geological 
scale from the summit of the Carboniferous to the base of the Cretaceous series. Of this inter- 
val there is no portion of which the exposures are not as complete as could be desired, nor is 
there any part that was not as carefully examined as seemed necessary to learn all it had to 
teach. While we had constantly to regret the absence of fossils, which alone can form reliable 
guides in establishing the subdivision of the great group of rocks occupying this space, the 
continuity and physical characters of the strata were on that account the more carefully noted. 
These rocks of themselves form a great mesa; and on this, fifty miles from its southern edge, 
rises another, which, singularly enough, is composed of the members of a different geological 
formation, the Cretaceous; and when we had ascended that we could overlook at one view all 
the space separating us from the carboniferous limestone west of the Little Colorado.* 
Fig. 19.—sgcTIoN OF MESA BETWEEN THE LITTLE COLORADO AND MOQUI VILLAGES, 
4 
0. 
= SS aeeaee ae  e Sls oe ee eee 
oS oes — ot eae ae 
Little Coloradh 
~ Lum j.68. 
| 
| 
rf 
es F ex eS 
or meal, asf Eee TERE SE ek SSG ee Mie aTW NG Im F, 
i Manipee sete grat are ak See errr eee ae yey 
Cer mre re rt Ft OES PTE re pf ie a ee 
« Lower cretaceous strata, 6 Variegated marls. c Red sandstones, d Carboniferous limestone, 
In the absence of more numerous and characteristic fossils, with all the data in our posses- 
sion, we were only able to make two or at most three divisions of the strata intervening 
between the Carboniferous limestone and the Chalk. Of these, the first and lowest is the 
group of red sandstones already described. The second is that of the variegated marls, a 
formation which has an aggregate thickness of about fifteen hundred feet, and is remarkably 
uniform in composition from bottom to top. It consists of red, blue, green, orange, purple, 
white, brown, lilac, and yellow marls, interstratified with bands of purple, bluish-white, or 
mottled magnesian limestones, most numerous toward the base. In some localities these marls 
are sufficiently indurated to deserve the name of soft calcareous sandstones. The only fossils 
observed in them are silicified trunks of coniferous trees, which are highly characteristic of 
the lower half of the series, being found abundantly wherever it is exposed. The variegated 
marls contain gypsum everywhere—near the Colorado in smaller quantities, toward the Rio 
Grande in immense masses. 
Upon the marls, and separating them from the first of the overlying Cretaceous sandstones 
at the Moyuis villages, is a stratum of lignite, or impure coal, which, in its partings of clay, 
contain an interesting group of fossil plants closely allied to Jurassic species of Europe. This 
is not a constant member of the series; and whether it should be given a distinct place in the 
geological scale, or should be regarded as belonging to the Cretaceous group above, or to the 
variegated marls below, cannot at present be determined, but I am inclined to the latter view, 
and am disposed to regard it as an index of the geological age of a part at least of that series. 
*The geological structure of this region will be comprehended at a glance by reference to the accompanying wood cut, 
