412 Ward — Geology of the Little Colorado Valley. 



Of the painted cliffs, considering the little that is known of 

 them, there seems to be nothing more to say. In looking at 

 these cliffs from a distance it is seen that they are overlain by 

 a white formation, the nature of which it is important to con- 

 sider. Before we had visited the region, so as to obtain a close 

 view of them, it was natural to suppose that they might consti- 

 tute Jurassic limestones and that the Triassic system might 

 terminate at the line which separates them from the variegated 

 sandstones. But upon close examination this was found not to 

 be the case, and these white rocks were found to consist of 

 sandstones often very pure and cross-bedded, with scarcely any 

 admixture of marl. These without question constitute the sum- 

 mit of the Triassic system in this region. They are, however, 

 not always white, or at least in some places, as for example in 

 the vicinity of Tuba City, they are underlain by a still thicker 

 bed of soft brown sandstone, which is somewhat argillaceous 

 and easily worn by the wind, forming chimney buttes and ruins. 

 This bed has a thickness along the headwaters of the Moen- 

 copie Wash of about 200 feet and is overlain at the highest 

 points by the white sandstones to a thickness. of 100 feet more. 

 These sandstones are very porous and all the waters that fall 

 in that region immediately pass through them, but as they 

 approach the summit of the much harder and firmer beds that 

 constitute the lower portions of the series these waters are 

 arrested and come out in the form of springs, sometimes almost 

 of small rivers, along the crest of the cliffs above the Moen- 

 copie Wash. It is on one of these springs that the little Mor- 

 mon town of Tuba City is located, and this is true also of Moa 

 Ave, Willow Springs, and other settlements in that country. 

 Still farther back the Cretaceous lignites and limestones lie 

 unconformably upon these uppermost sandstones of the Trias, 

 and the Jurassic is wanting altogether. 



The following columnar section of the strata of the Little 

 Colorado Valley will make the above descriptions more clear. 



DESCRIPTION OF THE SECTION. (See page 413.) 



Feet 



1. Argillaceous shales 100 



2. Calcareous shales 100 



3. Argillaceous shales _ 200 



4. Sandstones _____ 10O 



5. Argillaceous shales 200 



Total thickness of Moencopie beds 700 



Feet 



6. Shinarump Conglomerate 800 



7. Variegated marls 400 



8. Sandstones 100 



9. Limestone ledge 20 



10. Mortar beds 80 



11. Calcareous marls __ _ _ 200 



Total thickness of the Shinarump 1,600 



Feet 



12. Orange red sandstone _ _ 100 



13. Variegated sandstones 800 



14. Brownsand stones 200 



15. White sandstones. __ 100 



Total thickness of Painted Desert beds.. 1,200 

 Total thickness of Trias 3,500 



