GENERAL GEOLOGY 
47 
is lithologically like the Kadiak slates containing the fos¬ 
sils here under discussion. It will be difficult for a long 
time to separate these nearly barren beds, which are con¬ 
nected by many lithological similarities, into a Triassic 
and a Jurassic series, and I have therefore left the name 
6 Vancouver Series’ to cover them all, with the limits of 
usage given it by Dr. Dawson. 
SITKA 
The prevailing rock about the town of Sitka is a black 
slate, often greatly crumpled and jointed. 
A very interesting and characteristic rock of this series 
is the tuffaceous greywacke found in typical development 
at the mouth of Indian River, near Sitka, and elsewhere 
at many places on the island. It has the aspect of a firm 
dark massive coarse sandstone, in which many of the grains 
consist of fragments of other rocks. 
A slide cut from the rock at the mouth of Indian River 
(203) proves it to be fine-grained indurated tuff, contain¬ 
ing many clastic quartz grains, together with shattered frag¬ 
ments of black carbonaceous shale, of a hyalopilitic andesite 
groundmass, and of a darker ophitic eruptive, probably ba¬ 
salt. It may be thought of as the product of explosive 
eruptions, which shattered and mingled several kinds of 
volcanic rocks with the sands and fragments of the muddy 
beds, the clastic ingredients being indurated by the heat 
of the eruptions in which they were involved, like the 
modern shell marls enclosed in the tuffs of the Pribilofs, 
already described. 
The beds at the mouth of Indian River were examined 
with care. The massive tuffs contain many small angular 
fragments of the black slate, which grow larger toward an 
adjacent area occupied by shattered slates in which the 
fissures are filled by small injected mud veins of the tuff 
which accompanied the eruptions. The dip and strike 
