CORRELATION OF FORMATIONS 481 



It is now manifestly important to determine the stratigraphic relations 

 of the horizon or zone in which this well marked vertebrate fauna occurs, 

 and upon this point Ward (42) made very valuable studies, although it 

 is still difficult to correlate his data with the more general statements of 

 earlier observers concerning other localities. 



The vertebrate fauna discovered by Ward occurs near the middle of 

 a section some 3,500 feet in thickness, all of which is assigned to the 

 Trias. Ward divides this section into three parts. At the base are the 

 41 Moencopie beds," 700 feet in thickness, consisting chiefly of dark 

 reddish-brown, soft, laminated argillaceous shales, nearly destitute of 

 silica [quartz], highly charged with salt and gypsum." Some calcareous 

 beds grade into white impure limestone. No fossils were found in the 

 Moencopie beds, and Ward states that " the whole series, wherever the 

 contact can be found, always rests in marked unconformity upon the 

 underlying Paleozoic rock (Upper Aubrey)." Upon these facts and the 

 observed transition into overlying Shinarump beds, Ward argues that 

 the Moencopie beds are not upper Paleozoic, as believed by " certain 

 geologists " not named. This seems to mean that they can not, in his 

 opinion, be considered equivalent to the fossiliferous " Permian beds " 

 found by Walcott in Kanab valley, or to the " Permian " of the Zuni 

 plateau. 



Succeeding the Moencopie come 1,600 feet of variable strata called by 

 Ward the Shinarump. Within this he distinguishes 2 formations, each 

 800 feet thick, the lower being the " Shinarump conglomerate " and the 

 upper the " Le Roux beds." 



The Shinarump conglomerate of Ward is by no means all conglomer- 

 atic. His concise characterization is as follows : " Conglomerates and 

 coarse, cross-bedded sandstones, with clay lenses interstratifled with 

 gray argillaceous shales and variegated marls." 



In fact, the marls become locally most prominent in zones which are 

 elsewhere strongly conglomeratic. 



The Le Roux beds are principally variegated marls, argillaceous and 

 calcareous, followed upward by sandstone, limestone, with flint frag^ 

 ments, 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 brilliantly colored. Brown, 



