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. 



