348 Sohtichert — Carboniferous of Grand Canyon of Arizona. 



surely arc if one but could attain the place. One looks 

 and loans, struggles and hopes, and most of the time is 

 distracted by the grandeur of the rocks. Among them 

 one sits and ponders his environment and becomes pain- 

 fully aware of his insignificance. 



Kaibab Limestone. 



The brink of the Grand Canyon between the Bright 

 Angel and Hermit trails is made by the Kaibab lime- 

 stone, here about 560 feet thick and of a light buff color 

 (see fig. 1). In this region the formation is not very 

 rich in fossils, but a few are always to be seen and about 

 ten species can be easily gotten. The common ones are 

 sponges, Composita subtilita, and Productus occidentalis, 

 and rarely one finds MeeJcella pyramidalis. As the Kai- 

 bab fauna is fairly well known, and as there are better 

 places for it than about the El Tovar Hotel, not much of 

 the writer's time was devoted to collecting it. On the 

 Bright Angel trail, the brink begins at bench mark 6866 

 feet above sea level ; at bench mark 6575 fossils are not 

 rare, and here may be had, among others, Productus 

 ivesi and Meekella pyramidalis, both characteristic spe- 

 cies of the Kaibab formation. This lower part of the 

 Kaibab is full of bands and nodules of diagenetic flint, 

 some of which include sponges. The formation passes 

 without break through a narrow transition zone of inter- 

 bedded limestone and sandstones into the Coconino sand- 

 stone. In the Shinumo quadrangle 1 to the west the transi- 

 tion into the Kaibab is even more gentle, showing clearly 

 that these two formations belong to one unbroken cycle 

 of deposition. To the southeast the Kaibab appears to 

 thin somewhat and becomes thinner bedded and impure 

 through the introduction of sand. 2 



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, for 

 these in several forms are very much like those of the 

 Pennsylvanian. The fauna as collected by Noble in the 

 Shinumo quadrangle is listed by Girty 3 and he here 

 correlates the Kaibab limestone with the Manzano group 



1 L. F. Noble, U. 8. Geol. Survey, Bull. 549, pp. 70-71, 1914. 

 2 H. H. Robinson, U. S. Geol. Survey, Prof. Paper 76, 1913. 

 3 Noble, op. cit., p. 71. 



