84 GEOLOGY. 
that upon which it rests. Its broken edge has here an altitude of about five hundred feet, 
composed exclusively of Lower Cretaceous strata. few miles further north additions are 
made to it by accessions of other, but similar, members of the same geological series, until a 
thickness of from seven to eight hundred feet is attained. Preserving such characters, this 
Lower Cretaceous mesa extends over a large area northwest, north, and east of the point where’ 
we ascended it. With the exception of valleys of erosion cut down to the formations below, it 
stretches continuously to the Great Colorado on the northwest, and to the Rio Grande on the 
east. How much of the area within this angle is occupied by it is as yet unknown; for a wide 
territory towards the north is still unexplored, but we traversed enough of this district to see 
that the Lower Cretaceous strata cover a larger space on our route than those of any other 
formation. 
On the way from Santa Fé to Fort Leavenworth we were for nearly half the distance travel- 
ling on a continuation of these rocks; and there seems good reason to suppose that they form 
the geological substratum of much the greater part of the country bordering the Rocky moun- 
tains between the 35th and 40th parallels. They extend, as we know, with more or less inter- 
ruption, in a broad belt, along the eastern bases of the mountains far northward into the British 
possessions. 
From the fossils collected in the country bordering Grand and Green river by Dr. Schiel, as 
well as from his description of its geological structure, (Pacific Railroad Report, vol. II, p. 101,) 
it is apparent that the Cretaceous strata, as well as those of the variegated marls, are visible 
over a considerable area on the route of Captain Beckwith north of the Moqui country; and 
there is little doubt that the formations passed over by us in this region are continuous to and 
beyond the mouth of Grand river. 
Lower cretaceous mesa wall, Moqui villages. 
The cliffs, on the summits of which the Moqui towns are perched, are composed of the 
following strata: 
t. 
1. Soft coarsd yellowin sanmutone- isa... 5s sec. cee ck pees go Sam eegee as "95 
~. Creen shale - +--+ «+c. teehee ose ee ee re es babes + see Vee Ce ee cm © 12 
3. Blue shale with pinnules of Newropteris angulata.--... sdyigdnaleioaemays 3 Apeieiny amines gf : 1 
4. Lignite -.--...--. OO ee EN a no ne asin on edn mien 18 
Be ee NAS... vs ue a atin ee ea 6 eo oe Wieck nae oe te ke a ee 2 
6. Cellular sandstone -------. Pg take Tare pas ee ee at ad Oks AGG cas .o 5 be eae bes ent 5 
3, Brown torrovinows shale. ..->...c..s.5<-0.. Piea by oe sos okk Los cake Pea 4 
