PACIFIC COAST, YAKUTAT TO ALSEK RIVER. 83 
md perhaps in part to the early Mesozoic era. Two distinct series 
lave been differentiated, and the existence of a third is suspected on 
.he evidence of material brought out from behind the range by glaciers, 
rhe two oldest of these series are considerably metamorphosed. The 
roungest is but little altered. All of them have been intensely and 
somplexly folded and have been broken by overthrusts and tension 
aults to such a degree that the structural features are most intricate. 
FORMATIONS. 
METAMORPHIC COMPLEX. 
The material brought out from the area of the interior ice fields by 
he Yakutat and Alsek glaciers comprises a large variety of such 
netamorphic and igneous rocks as hornblende schist, greenstone, 
gneiss, marble, granite, diorite, and porphyries. No similar rocks 
vere observed in place at any point in the Coast Range by the writer, 
uid, as they are distinctly more altered than the two other series 
>bserved, it is believed that they belong to a still older group of 
ormations. a 
SCHISTOSE SEDIMENTARIES. 
The lowest canyon of Alsek River exhibits a fine section of meta- 
norphosed sedimentary rocks lying in vertical isoclinal folds. The 
lection is incomplete at both ends and the relations of the rocks are 
is yet unknown. The portion of the series there exhibited consists 
argely of quartzose schists and phyllites — the metamorphic deriva- 
tives of alternating graywackes, quartzites, and slates. On account 
)f the rapid alternations in the composition of the original deposits, 
he initial bedding of the rocks is still fairly distinct, and it happens 
hat the schistosity is in most places parallel to this bedding. Through- 
>ut the exposure numerous small quartz veins and stringers traverse 
he schists. None of these, however, was found to contain valuable 
ninerals. 
YAKUTAT SERIES. 
The Yakutat series has been described in detail by several geolo- 
gists 6 ' who have studied the rocks about Yakutat Bay. Subsequent 
exploration shows that the greater part of the Coast Range to the 
east, at least as far as the east side of the Yakutat Glacier, consists of 
a From observations on the shores of Russell Fiord, Tarr infers that the green schists and gneisses are 
tratigraphicnlly continuous with schistose graywackes and slates similar to the second series of the 
> resent paper (unpublished evidence, 1905). 
b The use of the word series is not in accordance with the Survey rules of nomenclature, but is a tem- 
>orary expedient only, to be abandoned as soon as sufficient detailed work is done to permit the sub- 
livision of the rocks to which it is now applied. 
c Russell, 1. C, Nat. Geog. Mag., vol. 3, 1891, pp. 167-170. Emerson, B. K., Harrhnan Alaska Expe- 
lition, vol. 4, 1904, pp. 49-50, 125-146. Tarr, R. S., and Martin, Lawrence, Bull. Geol. Soc. America, 
rol. 17, 1906, p. 33. 
