390 Johnston— Imbricated Structure in River-gravels. 



also shown, in places, in comparatively fine gravel as in 

 fig. 1. This figure shows a section of river gravels in 

 the bed of Trent river, at Campbellford, Ontario. The 

 largest pebbles in the section are about 8 inches in diame- 

 ter. The direction of the current was from right to left. 

 Imbrication of the pebbles is not well shown because of 

 the fineness of much of the material, but the pebbles have 

 a fairly uniform dip in an upstream direction and lie with 

 their longer axes in the direction of the current. The 

 face of the section is vertical except in the lower part 

 which is talus. 



Fig. 2 shows a vertical section of Tertiary conglome- 

 rate exposed on the south side of Burrard inlet near 

 Vancouver, British Columbia. Imbricated structure is 

 fairly well shown in the conglomerate and shows that it 

 was formed from river gravels. It is therefore non- 

 marine. The section is an east-west one, and the stream 

 which deposited the gravel flowed west, that is, from left 

 to right in the section. The conglomerate beds have a 

 general dip of 10 to 15 degrees towards the south. As 

 the depositional dip must have been in the direction of 

 the current, the dip towards the south is structural. 

 Imbricated structure may be occasionally used, therefore, 

 both to distinguish marine from non-marine deposits and 

 for structural purposes. 



