EARLIEE TERTIARY (EOCENE AND OLIGOCENE). 789 



and neither the lithologic character of the beds nor the fossils which they contain are sufficiently 

 distinctive to make it possible to recognize with certainty the complete stratigraphic succession. 

 The presence of two easily recognized horizons, the arkose and the conglomerate, give 

 distinctive character to two parts of the stratigraphic column. The arkose, with its associated 

 coal, is restricted in area! distribution to the region north of Bering Lake, and the conglomerate 

 to the region south of the lake. Between these regions are areas of no outcrops, and none of 

 the beds of either region can be recognized with certainty in the other. 



Section north of Bering Lake. 



Tokun formation: Feet. 



a. Sandstone 500 



6. Shale with thin, flaggy sandstones and with occasional calcareous concretions 2,000+ 



Kushtaka formation: 



c. Arkose with many coal beds and with some shale and sandstone 2,500 ± 



Stillwater formation: 



d. Shale and sandstone 1,000+ 



Section south of Bering Lake. 



Katalla formation: • Feet. 



e. Conglomerate and conglomeratic sandstones interbedded with shale and sandstone 2,500 



/. Flaggy sandstone 500± 



g. Soft shale with calcareous concretions and with bed of glauconitic sand near base 2,000 



Ji. Sandstone 1,000 



'i. Soft shale 500+ 



The succession in each of these sections may be assumed as reasonably correct, although 

 there is a possibility that the thicknesses are too great because of there having been repetition 

 of the less characteristic beds by faulting. The correlation of the beds of one section with 

 those of the other rests at present upon evidence which is incomplete and unsatisfactory and 

 must be regarded as suggestive rather than conclusive. It is probable that one of two corre- 

 lations is true: The shale and sandstone of the Stillwater formation (d) may overlie the con- 

 glomerates (e) of the KataUa formation with a concealed interval of unknown extent between 

 them, or a and i may be identical with h and i. In the former case the conglomerates underlie 

 the coal field; in the latter case the coal underlies all, or nearly all, of the entire region under 

 . discussion. The stratigraphic and structural field evidence proves nothing either way but 

 suggests, as the most probable relation, that the entire section north of Bering Lake overlies 

 the section south of the lake. 



The Tertiary rocks contain fossils at many localities, but they are usually poorly preserved 

 or not characteristic. They consist chiefly of leaves and of marine MoUusca, but include also 

 a few echinoids, Crustacea, fish, and fresh or brackish water MoUusca. 



The paleontologic evidence may be summarized as follows: " 



1. The marine MoUusca from the sandstone of the Tokun formation are either so poorlv 

 preserved as not to admit of specific identification or belong to undescribed species.* They 

 are almost certainly Miocene, but can not be definitely correlated with any known Miocene 

 faunas of other regions. 



2. The plants from the coal-bearing rocks include poorly preserved individuals which 

 suggest species of the Kenai formation of Cook Inlet, generally considered to belong in the 

 upper Eocene or Oligocene. The best-preserved specimens, however, represent species which 

 are not known in the Kenai and which are suggestive of later Tertiary age. There is no positive 

 evidence that the exact equivialent of the Kenai occurs in this region. 



o Data furnished by W. H. Dall and Ralph Arnold on the MoUusca, by P. H. Knowlton on the plants, and by 

 W. B. Clark on the echinoids. 



6 This statement applies to all the faunas of this region. 



