GENERAL GEOLOGY 
55 
determined by a few fossils to be Carboniferous. In both 
regions these sedimentary rocks occupy but small areas 
as compared with the eruptive rocks which have cut and 
altered them, and it is interesting that the post-Carbonif- 
erous igneous rocks are of the same type at these widely 
separated localities. We may call them a tonalitic series, 
from the most prevalent variety. 
From the most southern point touched on Vancouver 
Island to Plover Bay in Siberia we found large areas of 
granitic rocks. Granite proper is abundant, especially 
along the whole length of the White Pass Railroad 
and around Sitka and the Reid Glacier. A far more 
abundant and characteristic rock is a biotite-tonalite of 
light color, coarse, even, granitoid texture, and very rich 
in titanite. This continues through Fraser Reach, Gra¬ 
ham Reach, Grenville Channel, and Chatham Sound, and 
around the Muir Glacier. Various porphyries and basic 
rocks — diorite-gabbro and diabase — are associated with 
the tonalite, but in a very subordinate way. 
These rocks are wanting along the coast north of Skag- 
way up to Port Clarence, but reappear in great force on 
the Asiatic coast around Plover Bay, and are apparently 
in place on St. Lawrence Island. 
The Vancouver Series, which extends along the whole 
coast from Vancouver to Bering Strait, seems to be of 
Triassic or early Jurassic age. It is a formation of shale, 
with subordinate sandstone and almost no limestone. 
There are very few igneous rocks connected with the 
Vancouver Series. These are all basic and have a ten¬ 
dency to change into serpentine. The pyroxenite at Far- 
ragut Bay, near Fort Wrangell, the serpentinized diabase 
at Landlocked Bay, and the diabase dike at Gladhaugh 
Bay, in Prince William Sound, are examples, as also per¬ 
haps the serpentinized pyroxenite from the cones seen 
across the tundra at Port Clarence, north of Cape Nome. 
