DISCUSSION OF AGE OF FORMATIONS 493 



than it did several years ago . . . that the Kaibab limestone is of 

 the same geologic age" (that is, -undoubted Permian). Schnchert^^ 

 maintains the Permian age of this formation still more strongly, saying 

 ^^that the Kaibab limestone is of early Permian age is now admitted by 

 most American stratigraphers. This view, however, has been attained 

 rather from its field relations than through a study of its marine fossils." 



Throughout Europe the Permian is characterized by a fauna very simi- 

 lar in its general composition to that of the Ivaibab. It contains, in 

 abundance, representatives of the brachiopods Pro ductus, Athyris, 

 Chonetes, Spinferina, and the Orthidce; of the pelecypods, AUorisma, 

 Schizodus, Pseudomonotis, Bakewellia, and Aviculopecten, and the last 

 representatives of the trilobites in the genus PhilUpsia. TJJiough 8pirifer 

 is very abundant in the European Permian, its absence from the Kaibab 

 would argue, if anything, a later rather than an earlier age for this 

 formation. 



The red shales and sandstones of the Supai formation, with their 

 characteristic cross-bedding, mud-cracks, and raindrop impressions, indi- 

 cate a terrestrial deposit under arid conditions. Such aridity is similarly 

 indicated in the heavily cross-bedded Coconino sandstone, with evidence 

 that much of it is of wind origin. In the midst of the shallow sea con- 

 ditions of the Kaibab limestone (indicated by the fauna and by the 

 presence of varying amounts of quartz grains up to a pure sandstone) ^^ 

 occur the red, gypsiferous shales of the middle Kaibab, also indicating 

 arid terrestrial conditions. Evidences of aridity increase with the Moen- 

 kopi and higher beds. Such prolonged aridity is an additional evidence 

 that these beds were deposited during the almost world-wide aridity of 

 Permian and Triassic times. 



The Permian age of the Kaibab limestone is thus indicated by the evi- 

 dence of wide-spread and prolonged aridity, by the absence of many 

 typical Pennsylvanian species, by the presence of forms characteristic of 

 the Permian of Europe, of that of the Mississippi Valley, and to a less 

 degree of the Guadalupian Permian of Texas (see also "Notes on 

 species"). It is further indicated by the paleobotanical evidence of the 

 Permian, or uppermost Pennsylvanian, age of the underlying upper Supai 

 formation. 



MOENKOPI FORMATION 



The Moenkopi of the type locality at Moenkopi Wash, north of Tanners 

 Crossing, was, in the field, apparently traced westward to the Virgin 

 River, in Utah. The rapid changes in lithologic character and in thick- 



a Op. cit, p. 348. 



22 H. W. and F. H. Shimer : Am. Anthropol., vol. 12. 1910, p. 248. 



