THE BASIN PROVINCE 153 



Schuchert regards the Coconino sandstone as, in part at least, formed 

 from wind-blown sand derived from the north and northwest: 



[This sand] " should be expected in near-shore deposits of Permian time because 

 of the then prevalent arid climates. The eolian sand, it appears, has been blown 

 into rivers that have brought it from a long distance to the northward and out of 

 it in the course of transportation has been washed or blown almost all other dis- 

 integrated rock material than the quartz. * * *" [The conclusion as to the origin 

 of this sandstone reached by the writer while in the field is that it represents the 

 material of a large delta of continental deposit laid down under constant but 

 probably local sheets of water that were evidently entirely fresh. The Coconino 

 may be the deposits of dunesands swept from the north into a series of basins or 

 fresh-water lakes like the present fresh- and brackish-water lakes on the outer 

 borders of the Nile delta.] 



"That the Coconino sandstone invaded to the southward a land composed 

 of the Supai formation is shown not only in the very different nature of these 

 underlying strata and the sharp contact between them, but especially in the 

 fact that the surface of the Supai has many vertical solution joints now filled 

 with the Coconino sands." 



On page 352 Schuchert makes the suggestion that 



"It may well be that the marine Kaibab limestone and the Coconino sand- 

 stone toward the east change finally into desert dune deposits and that the De 

 Chelly is the time equivalent of more or less of the Moenkopi, Kaibab, and Coco- 

 nino formations. 



"In the Upper Supai have been found plant remains which David White has 

 determined as Callipteris cf. sp. C. conferta; Walchia cf. W. gracilis; Gigantopteris ? 

 cf. Sphenophyllum." 



David White, in a letter quoted on page 354 of Schuchert's article, says : 



"The condition of preservation of the fragments is so bad that caution is 

 necessary in basing conclusions of any kind on the material submitted. How- 

 ever, the presence of Gigantopteris, Walchia, and probably of Callipteris, if my 

 tentative generic identification of the latter is correct, points to the Lower 

 Permian age of the flora. * * * In any event, it appears probable that the flora, 

 when it is better known, will be found to indicate a level not below the highest 

 stage of the Pennsylvanian." 



Schuchert notes the occurrence of these plants further east in Arizona 

 and concludes: 



"It should be noted that these fossils are found immediately above a marked 

 erosional unconformity. If, therefore, we give full significance to this uncon- 

 formity, and with it bolster up White's provisional conclusions as to the age of 

 the plants, the upper 290 feet of the Supai are to be referred to the Permian 

 system." 



