482 CROSS AND HOWE — RED BEDS OF SOUTHWESTERN COLORADO 



cross-bedded sandstones (200 feet) and white massive sandstones (100 

 feet) form the top of the section studied. 



No doubt the Shinarump group of Ward is in large degree equivalent 

 to the Shinarump of Powell, Dutton, and others, as developed in the 

 Plateau country of Utah, and the vertebrate fauna of the Le Roux beds 

 serves to correlate them with the lower Dolores strata containing the 

 same fauna ; but, until the unconformity reported by Ward at the base 

 of the Moencopie beds has been traced sufficiently to demonstrate the 

 importance of the stratigraphic break it indicates, further correlation of 

 the Moencopie strata is difficult. It is reasonable to suppose that the 

 base of the Moencopie is actually the base of the Triassic section, and 

 that deposition began in Arizona much earlier than in southwestern 

 Colorado. On the other hand, it may be that the belodont fauna will 

 be found at horizons lower than the base of the Le Roux beds. If the 

 Moencopie beds are Triassic the stratigraphic break below them accounts 

 for the absence of strata equivalent to the Permian of Kanab valley found 

 by Walcott and to be referred to in the next section of this discussion . 



The lower 900 feet of the Painted Desert beds of Ward may plausibly 

 be referred to the Vermilion Cliff, or upper Dolores sandstone, while the 

 brown and white sandstones above probably represent a part of the 

 White Cliff, or the La Plata sandstone. 



THE PLATEAU SECTION OF SOUTHERN UTAH 



Sections of other investigators. — Having practically traced the Red beds 

 and overlying formations of the Jura from the San Juan mountains to 

 the Grand and Colorado rivers and having tentatively correlated them 

 with formations of the Zuni plateau and the Little Colorado valley, we 

 will now cross the Grand canyon and compare the original sections of 

 the Plateau country, described by Powell, Gilbert, and Dutton, with those 

 which have been studied more in detail in outlying portions of this great 

 stratigraphic province. 



Divisions established by Powell. — The formations with which we are now 

 dealing occur in most wonderful development as the steps between the 

 Tertiary high plateaus and the Carboniferous plain through which the 

 Grand canyon has been cut. This succession of terraces and bounding 

 cliffs, often compared to an open book of geological history, exhibit the 

 major divisions of the stratigraphic section in such perfection that Powell 

 naturally drew upon the descriptive terms of this region for the names 

 he was the first to confer. Powell called one great group of strata " the 

 Shinarump," the name meaning u the weapons of Shinav," the wolf-god, 

 and referring to the huge petrified tree trunks which are so common in 

 the formation. To the succeeding divisions the terms " Vermilion Cliff" 

 and " White Cliff" were given from the great scarps which face the Grand 



