514 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



The Le Roux beds are principally variegated marls, argillaceous and calcareous, followed 

 upward by sandstone, limestone, with flint fragments, and at the top more calcareous marls. 



Fossil wood occurs all through the Shinarump group and none is found beyond it. The 

 petrified forests occur within the Le Roux beds and the vertebrate remains were only found in 

 these strata. Bones and fossil wood were found together in many places. 



The "Painted Desert beds" of Ward follow the Le Roux beds and consist of sandstones. 

 The lowest stratum, 100 feet thick, is soft, friable, highly argillaceous, and of orange color. 

 Above this come 800 feet of variegated sandstones, regularly stratified and briUiantly colored. 

 Brown 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 a 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 wiU 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. * * * 



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

 Vermihon Chff or upper Dolores sandstone, while the brown and white sandstones above probably 

 represent a part of the White Cliff or the La Plata sandstone. 



A detailed description of these formations is given by Ward.^"®* 

 In northern Arizona and southern Utah Permian and Triassic strata are sepa- 

 rated by an unconformity as determined by Walcott.®** (See p. 484.) Cross "^J 

 gives a detailed section by Walcott of the Jurassic and Triassic of this region, which 

 may be summarized as follows : 



Section of Jurassic and Triassic formations in the Kanai Valley, Utah. 



White and red sandstone and shale, more or less gypsiferous with a variable conglomerate bed Feet. 



(1-7) 745 



Magnesian limestone intercalated with sandy shale, fossiliferous near the top (8-12) 215 



White Cliff sandstone (13) 585 



Vermilion sandstone (14) 650 



Red and gray, often massive sandstone with some shale beds ( 15-20) 950 



Red and gray sandstone with shaly partings, carrying carbonized fragments of wood (21-22) 235 



Thin-bedded and massive sandstone with, shale layers, fish teeth and other fossils (23-25) 100 



Reddish-brown and greenish friable sandstone and shale (26-29) 860 



Gray conglomerate and sandstone (30) 50 



[4, 390] 



The numbers in parentheses refer to Walcott's detailed section as given by 

 Cross and serve to distinguish the beds on which Cross ^^^^ comments as follows: 



In this Kanab section it is evident that Nos. 1 to 12 inclusive, aggregating 960 feet in 

 thickness, represent the upper Jurassic group called the Flaming Gorge by Powell. No. 13 is 

 the White Cliff sandstone, considered as the lower Jurassic in this discussion but placed by 

 Powell in the Trias. Mr. Walcott comments in his notes upon the absence of a sharp line 

 between this sandstone and that below it. Reasons why an apparent transition at this horizon 

 is natural have been presented. This thickness of the vermilion-colored sandstone, 14 of the 

 section, was found to vary from 600 to 700 feet on opposite sides of the valley where the section 

 was made, a variation which may possibly be due to erosion. 



