484 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



With reference to the supposedly Permian equivalents of the Cutler formation 

 in the Zuni Plateau, New Mexico (I 12), Cross derives his information from Button^' 

 and, after describing Newberry's section of the same region, says : 



The "Saliferous sandstones" of Newberry's report Button divides into three formations. 

 At the base is a formation 450 feet thick, mainly "sandy shales, containing gypsum and selenite 

 in abundance, with here and there thin bands of limestone." At some unspecified horizon in 

 this formation Dutton found "several specimens of Bakewellia and an attenuated form of 

 MyaUna." On this ground he correlates these beds with the Permian of the Kanab Canyon 

 district, where Walcott had discovered a more extesinve fauna. "The Permian beds are dis- 

 tinguished for their dense and highly variegated colors — chocolate, maroon, dark brownish reds 

 alternating with pale, ashy gray, or lavender colors." 



The Permian strata thus described are overlain by "a very coarse, almost conglomeratic 

 sandstone," some 50 feet in thickness, which Dutton correlates unhesitatingly with the "Shina- 

 rump conglomerate " (a particular conglomerate within the Shinarump group), referring to the 

 fact that it is persistent and uniform in aspect wherever it appears throughout the plateau 

 country of Utah and Arizona. He does not further describe it in this report. 



Following Walcott, the conglomerate thus identified as the Shinarump in the Zuni Plateau 

 is. considered by Dutton as the basal stratum of the Trias. 



After discussing the Triassic of Button's section, Cross ^^^^ continues : 



Beneath the Trias in the Zuni district is Dutton's Permian, lithologically a typical Red 

 bed formation. That would correspond to the Cutler formation in stratigraphic position; but 

 other factors enter into the problem at this point and render any definite suggestion of such a 

 correlation premature. Below the Zuni Permian comes the Aubrey group, and beneath the 

 Cutler occurs the Hermosa formation (ignoring the uncertain Rico beds), both Aubrey and Her- 

 mosa carrying Pennsylvanian invertebrate faunas. Dr. G. H. Girty informs me, however, that 

 these faunas are not known to have a single species in common, and the equivalence of the two 

 fossiUferous formations is therefore by no means to be assumed, though their stratigraphic 

 position seems to be the same. 



In northeastern Arizona, according to Ward,**^^ the Moencopie formation rests 

 in marked unconformity on the underlying Paleozoic strata (Aubrey group) and 

 is therefore not to be classed as upper Paleozoic (Permian) . Ward therefore placed 

 the Moencopie in the Triassic, but later work by Darton^**''' tends to place it in 

 the Permian. 



In the northwestern part of Arizona is the Kanab Plateau, traversed by Kanab 

 Canyon, which leads from the north to the Grand Canyon of the Colorado. Here 

 Walcott ^*^ determined the presence of Permian strata. He says: 



The Permian group terminates above with ripple-marked, banded reddish-brown and 

 chocolate-colored arenaceous shales and sandstone. A plane of unconformity by erosion sepa- 

 rates it from the overlying Shinarump conglomerate, which is considered as the base of the 

 lowest Mesozoic group. It is undoubtedly of Triassic age, but, as yet, this has not been 

 determined by paleontological evidence in the Colorado Valley. 



The chocolate arenaceous shales give way below to drab or lavender-colored arenaceous 

 and gypsiferous marls and shales, that pass, naidway of the group, into reddish-brown shales 

 of the same general character. A thin stratum of impure limestone is intercalated in this bed 

 44 feet above the summit of the lower division and 15 feet above a band of impure shaly lime- 

 stone. Tliis band of limestone is of variable thickness and character and forms the base of the 

 upper division. Numerous fossils occur in it and the associated arenaceous layers. 



The summit of the lower division was slightly eroded antecedent to the deposition of the 

 limestone. The upper bed is a reddish-brown gypsiferous marl that becomes more arenaceous 

 below, finally passing into a sandstone that rests on the chocolate and cream-colored limestone 



