230 



Kilometres basin was closed by a thick valley glacier at the 

 time of silt deposition. The valley was similarly 

 dammed by a large, local glacier entering from 

 the valley of the North Thompson. Through- 

 out the distance from Shuswap nearly to 

 Kamloops — 50 kilometres — the valley of the 

 South Thompson was thus laked, and fine, 

 white silt was accumulated to depths greater 

 than 120 metres. 



Nine kilometres beyond Shuswap station, 

 the western contact of the granite is reached. 

 It is here intrusive into the rocks of the Nicola 

 series, in which the valley of the South Thompson 

 river is sunk for a distance of 19 kilometres 

 (102 mis. to 118 mis.) 



The first rocks of this series to be crossed 

 constitute a thick well-stratified body of hard 

 sandstones and fine-grained strata shown to be 

 in part bedded volcanic ash, but probably in 

 part true argillites. Subordinate volcanic brec- 

 cias of basic composition are interbedded. 

 The whole forms the youngest local phase of 

 the Nicola series conformably overlying the 

 massive lavas of the Triassic, and is itself either 

 upper Triassic or Jurassic in age. The dips 

 here range from 6o° to 8o° to the east, indicating 

 an apparent thickness of more than 2,000 metres 

 for this stratified member. 

 104 m. Just beyond Pritchard siding is its (lower) 



168.6 km. contact with the very massive lavas of the 

 Triassic Nicola series (see p. 145). These can 

 be well seen in dark coloured bluffs across the 

 river. Their structure is extremely difficult 

 to decipher. Pyroclastic beds are rare; thick 

 flows (and sills?) of basaltic lava are dominant. 

 Wherever the dips can be observed they are 

 steep, generally 50 to 90 , with strikes ranging 

 from N.-S. to N.W.-S.E. 



To right and left the distant summits are 

 capped by Tertiary basaltic lavas (Kamloops 

 group) with associated fresh-water sandstones. 

 These have low dips and overlie the more 

 massive, more deformed, and more altered 

 Triassic volcanics unconformably. 



