4 8 



1,500 feet (450 m.) on Kuiu island. A large part of the 

 Tertiary sediments may have been subsequenly removed 

 by erosion. The next important event in the geologic 

 history was the development of the ice sheet which covered 

 the entire district. Its retreat left the topography in 

 essentially the present form. After the retreat of the ice 

 some basaltic sheets were locally erupted. 



In this brief sketch of the geologic history of South- 

 eastern Alaska many details have been omitted, but 

 many more details are still required before the history can 

 be written with even a first approach to completeness. 

 Many of the conclusions reached are still tentative and 

 merely the best that can be drawn from the existing 

 evidence. On the accompanying maps only six subdivi- 

 sions are recognized, the entire Paleozoic being grouped as 

 a unit; likewise the Mesozoic, the Tertiary, and the 

 Quaternary. It should be noted that the greenstone 

 black slate series apparently includes formations ranging 

 from upper Carboniferous to Jurassic in age. This finds 

 expression in the term "Vancouver series" which is used 

 in British Columbia. 



Miles and ANNOTATED GUIDE. 



Kilometres 



o m. Prince Rupert. — After leaving Prince Ru- 



O km. pert and passing Dundas island on the left, and 

 Port Simpson, 25 miles (40 km.) on the right, 

 the route of the excursion enters Dixon entrance 

 and crosses the International Boundary line 

 into Southeastern Alaska. On the right is 

 Portland inlet and Portland canal, one of the 

 largest fiords on the Pacific Coast. Portland 

 canal cuts almost entirely through the Coast 

 Range batholith and extends practically to its 

 eastern flank. Mineral deposits have been 

 discovered along this eastern contact of the 

 batholith in Canadian territory both at the head 

 of Portland canal and near Observatory inlet. 

 Several bands of sedimentary rocks, included 

 in the Coast Range batholith, are also heavily 

 mineralized and promise well as ore producers. 

 Dixon entrance is one of the few exposed 

 parts of the inland passage, and at certain times 



