226 



Kilometres with northeasterly dip. As one goes westward 

 he descends in the series and finds the limestone 

 becoming increasingly charged with sills of 

 orthogneiss and aplite. Near the 47th mile- 

 post the limestone is apparently underlain 

 by a massive quartzite interrupted by films and 

 thin beds of coarse muscovite schist. This 

 may represent a siliceous member of the Salmon 

 Arm formation or else the younger Chase 

 quartzite. The coarseness of the mica schist 

 and the massiveness of the lowest beds of lime- 

 stone are explained by the thermal metamor- 

 phism exerted by the abundant sills. In the 

 southeastern slope of Bastion mountain across 

 the lake, the coarse, glittering (Salmon Arm) 

 mica schists cut by many granitic sills pass up 

 gradually into a fine-grained metargillite almost 

 free from intrusives, and the latter rock is 

 conformably overlain by the normal, fissile 

 Sicamous limestone. 



One of the best exposed sections of the Shus- 

 wap series is that exhibited as a great monocline 

 from Canoe point, along the western shore of 

 the lake, to Cinnemousun narrows, 23 kilometres 

 distant. Green schist and massive limestones, 

 corresponding to the youngest recognized mem- 

 bers of the Shuswap series, are found near the 

 narrows and at the top of this northerly- 

 dipping monocline. The rocks on the opposite 

 shore of the lake, north of Sicamous, are 

 largely orthogneisses and have attitudes usually 

 quite different from those of the monoclinal 

 section. The valley of this part of the main 

 lake therefore seems to be located on a fault 

 with downthrow on the west. 



From the limestone band just west of Sicamous 

 to the 56th mile-post the line crosses the Salmon 

 Arm schists injected with many sills and dykes 

 of orthogneiss, pegmatite and aplite. 



At 56-2 miles (90 -4 km.) a large rock-cutting 

 shows a coarse porphyritic syenite, which crops 

 out again at the southwestern base of Bastion 

 mountain nearly due west, across the lake. 

 This rock appears to be a peripheral phase of 



