No. 4.] DAWSON — BRITISH COLUMBIA. 241 



NOTE ON SOME OF THE MORE RECENT CHANGES 

 IN LEVEL OF THE COAST OF BRITISH COLUM- 

 BIA AND ADJACENT REGIONS. 



By George M. Dawson, Assoc. R.S.M., F.Gr. S. 



The elevation of the Cascade or Const Range of British Co- 

 lumbia, and the parallel range of Vancouver Island, must have 

 taken place to a great extent, though probably not entirely, in 

 post cretaceous times. On the upturned and denuded edges of 

 Cretaceous rocks, in the interior of British Columbia, re>t nearly 

 horizontal beds, which appear to be of Miocene nge, and which 

 piss upward into the great sheets of volcanic material, with 

 which the whole interior plateau must at one time have been 

 covered. The sedimentary Miocene beds seem to have been 

 formed in fresh-water lakes, produced peihapsby interruption of 

 the drainage by mountain elevation, which there is evidence 

 to show, may have continued to some small extent even in post- 

 miocene times. The country cannot have been so low at this 

 period as to admit the sea to the interior plateau, but appears to 

 have been depressed to a small extent, as marine tertiary beds, 

 probably of this age, are found along the coast above the present 

 sea-line. No Pliocene deposits have yet been recognised, and 

 it was probably during this period, with the haul standing at 

 least 900 feet higher than at present, that the deep river valleys 

 or canons now forming the remarkable system of fjords by which 

 the coast is dissected, were cut out. These fjords are very gene- 

 rally in their sheltered upper reaches over 100 fathoms in depth, 

 often over 150 iathoms, and probably in many cases over 200; 

 though in most of them the actual- depth has only been ascer- 

 tained in a few places. When they open on the broader water- 

 ways, where the strong tides of the Pacific coast run with greater 

 power, they are iound to be silted up, and blocked with bars and 

 banks; the water being generally shoalest where the water 

 stretches are most extensive. This is especially noticeable on 

 the west coast of Vancouver Island. The ice which can be 

 shown to have filled these fjords during the glacial period, must 

 have deepened them and altered their forms to some extent, but 

 probably in a degree quite inconsiderable when compared with 

 their pre-ghicial excavatien. 



