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It is generally conceded by all who have worked in the 

 central part of British Columbia that the development of 

 the plateau features of the interior were initiated by long 

 continued erosion acting throughout Eocene times. The 

 enormous amount of material eroded during this period 

 must have been carried away by streams and deposited 

 elsewhere, and the only considerable development of Eocene 

 beds in that part of the continent is found in the delta 

 of the Fraser river and in the neighbouring parts of the State 

 of Washington. The structure of these beds indicates 

 clearly that they were laid down as delta deposits in an 

 estuary of the sea; while in shape they have here a deltoid 

 arrangement with the apex of the delta pointing up Fraser 

 valley towards the lower end of the canyon. The shape of 

 these Eocene deposits suggests that the stream, which 

 carried the material of which they are composed, had its 

 outlet at or near the lower end of the present canyon and 

 it is probable that the course of that stream was along the 

 present course of the river at least as far as the Interior 

 Plateau region. This evidence, however weak, is the first 

 that we have of any stream existing along the present 

 course of the Fraser river. 



However, G. M. Dawson, who has studied the history 

 of Fraser river above the canyon, reached the conclusion 

 that the course of the river, as it exists to-day in the plateau 

 region, was only defined since the deposition of certain 

 flat-lying Miocene or Oligocene beds, through which the 

 river now cuts. Those beds however could have been 

 deposited in a lake or an expansion of the river where still- 

 water conditions prevailed along its course. 



The selection of the course of the stream along its 

 present lines has been governed largely by the structure of 

 the rocks through which it flows. For example, for 8 miles 

 (12-8 km.) below Lytton it flows in a band of Lower 

 Cretaceous rocks which have been down faulted against 

 the granite rocks and beyond this it follows closely the con- 

 tact of these Lower Cretaceous rocks with the underlying 

 Palseozoic formation as far as North Bend. Also, in the 

 gorge below this, though the trend of the valley is in the 

 main due south, in detail the course of the stream has 

 two well defined directions which correspond to two lines 

 of weakness in the granite rocks in which it is cut. These 

 two lines of weakness strike N. 20° E. and N. 15 W. Below 

 the gorge also the valley is carved out along structural 



