126 
ALASKA GEOLOGY 
received a name, having been called Yakutat by Russell 
in 1891. 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 Dali and Hyatt sug¬ 
gested that the age of the slates is Triassic or older. 
Dali 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. hi, p. 167. 1891. 
2 The statements in this paragraph, as well as other data concerning forma¬ 
tions and localities, are on the authority of Mr. Gilbert. 
3 Report on coal and lignite of Alaska, by W. H. Dali: 17th Ann. Rept. U. 
S. Geol. Survey, pt. 1, p. 872. 1897. 
