126 ALASKA GEOLOGY 



received a name, having been called Yakutat by Russell 

 in 1 89 1. 1 This name, therefore, applies to the strata at all 

 the localities. 2 



AGE 



All that could hitherto be said concerning the age of the 

 slate of the vicinity of Kadiak was that it is older than the 

 Cenozoic, and that it is unconformably overlain, in some 

 instances at least, by strata of early Miocene or Oligocene 

 age. As it has an aspect denoting considerably greater age 

 than the unquestionable Jurassic rocks underlying the Cen- 

 ozoic deposits at other points along the southern coast of the 

 peninsula, and as the only mollusk found in it was believed 

 to be of the genus Posidonomya, whose known range does 

 not extend above the Jurassic, both Dall and Hyatt sug- 

 gested that the age of the slates is Triassic or older. 



Dall says of them, 3 referring particularly to the ex- 

 posures studied by him on Woody Island: "The fossils 

 found are very few; one, apparently a Posidonomya, the 

 only bivalve; a singular organism like a flattened Den- 

 talium, but probably a worm tube; and an alga which 

 Professor Knowlton identifies with Eichwald's Chondrites 

 heeri were the most conspicuous. It is not improbable 

 that these slates are of Triassic age, but a final determina- 

 tion will require more prolonged study." 



In the same report, page 907, Hyatt says of the sup- 

 posed Posidonomya, which had been referred to him and 

 which is described in this paper as Inoceramya concen- 

 trica, " I should think it might be Triassic or older, but 

 there is no solid basis for this opinion." 



The quoted opinions were influenced perhaps by Fisch- 



1 An expedition to Mount St. Elias, Alaska, by Israel C. Russell : Nat. Geog. 

 Mag., vol. in, p. 167. 1891. 



The statements in this paragraph, as well as other data concerning forma- 

 tions and localities, are on the authority of Mr. Gilbert. 



'Report on coal and lignite of Alaska, by W. H. Dall: i?th Ann. Rept. U. 

 S. Geol. Survey, Pt. I, p. 872. 1897. 



