Schuchert — Carboniferous of Grand Canyon of Arizona. 359 



nian, and the lower part Mississippiau. Gilbert 8 and Lee 9 

 report Pennsylvanian fossils from the upper beds of the Red- 

 wall. But Gilbert's 'Red wall group,' in the Kanab division, 

 includes 500 feet, at least, of what I have been calling basal 

 Supai jn the Kaibab division. As one goes west, toward the 

 region where Gilbert and Lee got the fossils, there is introduced 

 more and more limestone in what I call basal .Supai, and it is 

 massive limestone like the Redwall. This Pennsylvanian lime- 

 stone is qbove the horizon where the erosional break appears to 

 be in the Kaibab division of the canyon. 



' ' In Bass Canyon the lower 500 feet of the Supai are alternat- 

 ing massive blue crystalline limestone with bands and nodules of 

 red chert, red shale, and red sandstone. In one limestone bed I 

 saw sections of cup corals and braohiopods. This indicates that 

 the basal Supai beds are in part marine in origin. Yet there is 

 gypsum present, red shales with sun-cracking and ripple-marks, 

 and maroon layers with septaria nodules. May we not have had 

 here an alternating of marine and fresh-water flood-plain 

 conditions ? 



"The whole middle Supai — all the great cliff -makers — is made 

 up of huge layers of fine cross-bedded sandstones with partings 

 of red shale and red shaly sandstone. This part of the Supai, as 

 you say, is certainly a unit. I noted the rain-prints, ripple- 

 marks and sun-cracks. I also saw several horizons of intra- 

 formational conglomerates, one of them beyond a doubt a 

 scoured and filled rain channel. I agree with you that this 

 part of the Supai is a terrestrial deposit." 



The fossils collected by Gilbert and Lee, and above 

 referred to, have been examined by Girty, 10 who reports 

 on them as follows : 



"At Yampai . . . were obtained: Derby a (f), Composita, 

 Aviculopecten, Myalina aff. M. meliniformis and 31. congeueris 

 and Edmondia (f). These fossils indicate a Pennsylvanian or 

 'Coal Measures' age." 



That the earlier Pennsylvanian sea was widespread in 

 the Colorado Plateau country is shown by its unmis- 

 takable presence in the San Juan area of southeastern 

 Utah. Here between Goodridge and Bluff, Gregory 11 

 and Woodruff 12 report many local faunae with Myalina 

 subquadrata, Spirifer rockymontanus, S. cameratus, 

 Hustedia mormoni, Productus nebrascensis, P. cora, 

 Marginifera muricata, M. ivabashensis , Chonetes meso- 



8 G. K. Gilbert, op. cit., p. 178. 



W. T. Lee, IT. S. Geol. Survey, Bull. 352, p. 15, 1908. 



10 Noble, op. cit., p. 67. 



11 H. E. Gregory, U. S. Geol. Survey, Bull. 431, p. 19, 1911. 



12 E. G. Woodruff, ibid., Bull. 471, pp. 83-85, 1912. 



