702 



INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



Miocene under tlie name Nulato sandstone. This conclusion seemed to be further supported 

 by fossils from sandstone which were d-etermined as Miocene. The stratigraphic position of the 

 coal-bearing beds of the Yukon will be considered below, but it will be noted that so-called 

 Kenai of the Yukon embraces beds as divergent in age as the Upper Cretaceous and the upper 

 Eocene. The stratigraphic work of Collier <^ in 1902, followed by that of Hollick in 1903 and the 

 studies of their collections by Stanton and Knowlton, have yielded ample proof of the Upper 

 Cretaceous age of both the Nulato sandstone and the underlying coal-bearing beds. * * * 

 Near Nulato there seems to be exposed a conformable series, consisting of sandstones, shales, 

 and conglomerates, wliich represent continuous sedimentation from the middle of the Cre- 

 taceous to the. Upper Eocene. 



Schrader's Koyukuk report '' makes mention of Lower Cretaceous fossils in an impure 

 limestone, associated with volcanic rocks, which outcrop near the sixty-sixth parallel, and to 

 the south of these of an impure limestone wliich carried Upper Cretaceous fossils, but assigned 

 the Nulato sandstone to the Miocene. 



Collier ^^^ gives the following description and tabular arrangement of the Cre- 

 taceous and Tertiary of the region: 



The Upper Cretaceous is represented near Xulato by sandstones, conglomerates, and dark- 

 colored shales, which outcrop along the river at intervals for about 100 miles. These have in 

 part yielded a marine invertebrate fauna of Upper Cretaceous age, as determined by Stanton. 

 Fossil plants were found in the same general horizon and were assigned by Dr. Knowlton to the 

 Upper Cretaceous. It is evident, therefore, that these beds include both marine and fresh- 

 water deposits. The fresh-water beds carry coals of commercial importance. The Cretaceous 

 beds have undergone considerable deformation but are not metamorphosed and, in fact, are 

 only slightly indurated. 



The succeeding horizon is made up chiefly of sandstone and conglomerate, with some shale. 

 It is called the Kenai series and is of upper Eocene age. These beds usually carry abundant 

 plant remains, which show them to be of fresh-water origin. The Kenai series has been named 

 from its typical occurrence on Kenai Peninsula and has been identified in various other parts of 

 Alaska. It occurs in isolated areas on the Yukon near the boundary and near Rampart and is 

 more extensively developed near Nulato. On the upper river it unconformably overlies various 

 horizons below the Upper Cretaceous, but near Nulato its relation to the Upper Cretaceous 

 seems to be one of conformity. The Kenai beds are, as a rule, little disturbed, but in some 

 localities they have suffered considerable deformation. The Kenai is the great coal-bearing 

 horizon of Alaska. Its coals are usually characterized by the presence of fossil resin, or amber. 



Provisional tabular statement of Yukon stratigraphy. 



a Bull. U. S. Geol. Survey No. 213, 1903. 



5 Twenty-first Ann. Kept. U. S. Geol. Survey, pt. 2, 1900, pp. 476^77. 



