344 



Practically the whole of the delta is believed to be 

 floored by stratified rocks of Eocene age, which are referred 

 to in the literature as the Puget group. They consist of 

 only slightly disturbed conglomerates, sandstone, shales and 

 some lignite, laid down in an estuary as delta deposits of 

 the ancient Fraser river. They have an estimated thick- 

 ness in this region of about 3,000 feet (914 m.),and contain 

 a variety of plant remains from which their age has been 

 determined. This formation contains the fire clay deposits. 



Overlying the Eocene beds are unconsolidated deposits, 

 of glacial and post-glacial origin, which were laid down 

 either sub-glacially or at the glacial front during the period 

 of ice recession. These lie at elevations as high as 400 feet 

 (122 m.) above sea level and consist of sands, gravel and 

 boulder clay. They form broad, flat-topped plateaus 

 which were at one time joined together and formed the 

 post-glacial delta of the river. Elevation of the land 

 relative to the sea, however, has taken place since, enabling 

 the river to cut into the older delta so that now only 

 detached remnants of it are to be found. This process of 

 deepening is related to the strong terracing of the upper 

 part of the Fraser valley. The stream is forming a modern 

 delta in the lower part of its course at the present time, and 

 this delta is gradually being pushed seaward into the Gulf 

 of Georgia. 



Summary of Geological History of Fraser Delta. 



The history of the delta as far as our present knowledge 

 allows us to read it may be summarized as follows: 



1. Post-Lower Cretaceous revolution, followed by the 

 development of an estuary, probably by erosion, where the 

 delta of the Fraser river now is. 



2. Deposition in the estuary of material derived by 

 erosion from the interior, and carried down by the ancient 

 Fraser river in Eocene times, forming the Eocene delta. 



3. Gradual but continuous removal of much Eocene 

 material in succeeding Tertiary times. 



4. Glacial period. 



5. Formation of Glacial delta by deposition of glacial 

 material during the closing stages of the Glacial period. 



6. Post-Glacial uplift resulting in the cutting down and 

 removal of much of the glacial delta deposits. 



7. Formation of modern delta at the mouth of the 

 stream. 



