W. A. Johnston — Delta of Fraser River. 451 



of Fraser river north to Pitt lake, the surface of which is 

 largely below the level of high tide and, therefore, may 

 be in part considered as belonging to the Recent delta 

 of the Fraser. A considerable part of the filling of this 

 area, however, is stratified clay deposited during the 

 period of uplift of the land, and parts of the delta area 

 above New Westminster are a few feet above sea-level. 

 It is probable, therefore, that the great part of the delta 

 deposits of the Fraser, above New Westminster, were 

 formed during the period of uplift following the final 

 retreat of the Pleistocene glaciers from this region, 

 and that the great part of the delta deposits below New 

 Westminster have been formed during Recent time when 

 the sea and land had their present relationship or very 

 nearly so. 



The delta is building out into fairly deep water in the 

 strait of Georgia, and in structure presents the forms 

 characteristic of a high-grade delta. The fore-set beds 

 are well developed and extend from the 3-fathom line to 

 about the 30-f athom line, and have an average dip of about 

 10 degrees. Below the 30-fathom line the beds slope 

 more gradually seaward, the 100-fathom line being 

 reached at from 1 to 2 miles from the outer edge of the 

 sand banks, which form the seaward part of the delta. 

 The sand banks are in large part exposed at low tide and 

 extend seaward on an average of 4 to 5 miles from the 

 higher delta land which is diked. The delta is building 

 out into fairly deep water in spite of the facts that the 

 river is tidal for a considerable distance above its mouth, 

 with a mean tidal range of 6.4 feet and a maximum range 

 of 15 feet at its mouth, and that the seaward front of the 

 delta is swept by fairly strong tidal currents. The 

 out-building occurs because of the dominance of the river 

 currents over the tidal currents. The flood-tidal currents 

 in the strait of Georgia run north and are the dominant 

 tidal currents. They have the effect of giving the larger 

 part of the subaqueous front of the delta a smooth, curved 

 outline lacking the finger-like projections characteristic 

 of many deltas. The steep under-water face of the delta 

 is a characteristic feature and extends along the whole of 

 the seaward front of the delta from the highland area of 

 Point Grey on the north to the highland area of Point 

 Roberts on the south, a distance of 14 miles. 



The thickness of the Recent delta is known approxi- 



