CARBONIFEROUS 297 



I'roductus aff. Iconinclcianus Veni. Camarophoria margaritovi Tschern. 



I'rodnctus aff. porrectus Kiit. ? Aviculipcctot 2 spp. 



Uarginifera ? aff. splendens Norwood Fish tooth, 

 and Pratten. 



"This fauna is uulike anything known in central and eastern North America, 

 and appears to be rather closely allied to that of the Gschel-stufe of the Ural 

 mountains. Probably the fauna of the Hueco, Weber, and Aubrey formations 

 of western United States will be found more or less closely related. In Alaska 

 it has been collected also in Pybus bay and on Kuiu island." 



Lots 14 and 15 represent the limestone in its typical development, 

 while the limestone which furnished lot 22 is associated with beds of 

 igneous origin. The limestone, which is of Upper Carboniferous age, 

 terminates the Paleozoic section in the Upper Yukon region. The suc- 

 ceeding strata in the section were not observed in direct superposition, 

 but a series of argillites, with one or more limestone beds, is believed to 

 hold this position. A collection of fossils was made in this series half a 

 mile above the mouth of Nation river, from a limestone about 15 feet in 

 thickness. A species of Halobia is the most abundant fossil in this col- 

 lection. Dr T. W. Stanton refers the fauna provisionally to the Triassic. 

 If this provisional determination is correct, the Upper Carboniferous 

 limestone of the Yukon section is limited above by rocks of Triassic age. 



The Carboniferous rocks above described show practically no meta- 

 morphism, and are in strong contrast in this respect to all the older rocks 

 of the Yukon except the uppermost member of the Devonian. It is also 

 noteworthy that, with the single exception of the pyroclastics found with 

 the Upper Carboniferous limestone at Glenn creek, there is no evidence 

 of igneous activity during the deposition of the Carboniferous sediments 

 of the upper Yukon. 



The Carboniferous terrains of the iipper Yukon are thrown up into a 

 series of broad, open folds, but some of the formations when studied in 

 detail are found to have suffered intense cross-folding, which has resolved 

 itself into many minor crenulations. This is beautifully shown in the 

 cliffs of Calico bluff. Here a rock face nearly 1,000 feet high exposes 

 the beautifully banded slates and limestones, which are intensely crumpled 

 in a direction nearly at right angles to the axis of the anticline of whicli 

 the bluff forms a western limb. The writers are indebted to Mr C. L. 

 Andrews, of Eagle, for the accompanying photograph showing these cren- 

 ulations (see plates 18 and 19). 



Spurr'"' included in his stratigraphic column a group of gray limo- 



"" J. E. Spun- : Geology of the Yukon gold district. Eighteenth Annual Report, U. S. 

 Geological Survey, part Hi, pp. 109-175. 



