308 BROOKS AiSTB KINDLE PALEOZOIC ROCKS OF UPPER YUKOJSi 



sented by a series of conglomerates, argillites, and sandstone usually 

 carrying more or less lignite. This formation, first described by Spun, 

 has been correlated with the coal-bearing rocks of the Kenai peninsula, 

 called the Kenai formation. The correlation is based both on the litho- 

 logic similarity and stratigraphic sequence and on the evidence of paleo- 

 botany. As this paper treats chiefly of the Paleozoic rocks, the various 

 problems connected with the distribution of the Kenai formation will not 

 be here discussed. It has been shown by Collier^^'- and confirmed by Arthur 

 Hollick that the Kenai of the lower Yukon includes not only Tertiary, 

 but also some Cretaceous beds — that is, it represents an unbroken sequence 

 from the Upper Cretaceous through to the Tertiary. While a similar 

 sequence has not yet been established on the upper river, it is by no means 

 impossible that such may exist. Dr P. H. Knowlton, who is the author- 

 ity on the Kenai plant remains, assigns them to the Upper Eocene or 

 Arctic Miocene, as it sometimes has been called, with the reservation, 

 however, that in some cases they may include some Upper Cretaceous 

 beds. 



The Kenai of the upper Yukon embraces rocks of rather divergent 

 character. In some instances the rocks are well indurated, being made 

 up of hard conglomerate, sandstones, and sandy and clayey shales or 

 slates, while in others the sandstones are almost unconsolidated and the 

 argillites very little indurated. This local divergence in lithologic char- 

 acter sometimes makes the identification of the Kenai formation difficult 

 when paleontologic evidence is lacking. The friable phase of this forma- 

 tion is easily differentiated from the other conglomerate-bearing terrains, 

 but the indurated conglomerates, sandstones, and shales are often very 

 similar to the rocks here called the Kation Elver formation. It is quite 

 possible, therefore, that on the accompanying map some Kenai beds may 

 be included with the Nation Eiver, and, on the other hand, that some of 

 the beds mapped as Kenai may in part belong to the Carboniferous. 

 Mr Prindle, who has studied the Tertiary of the Seventymile basin, states 

 that the indurated phase of the Kenai and the friable phase are there 

 found close together. 



The thickness of the Kenai formation was not determined by our 

 observations. It probably varies much locallj^, and in some instances may 

 attain a thickness of several thousand feet. In others it may be meas- 

 ured in hundreds of feet. 



The Kenai formation has usually been described as occurring in local 



i3t Arthur J. Collier : The coal resources of the Yukon. Bulletin no. 218, U. S. Geo- 

 logical Survey, p. 17. 



