243 



disturbances took place, uplifting and deforming the early 

 Tertiary formations. This orogenic movement brought 

 about vigorous erosion, and a great volume of the early 

 Tertiary rocks was swept away. Volcanic activity broke 

 forth on a grand scale in the early Miocene,* and great 

 thicknesses of basaltic lavas, agglomerates, breccias and 

 tuffs (Kamloops volcanics) spread over large areas. Crustal 

 warping took place probably in the late Miocene and 

 threw the flat-lying Kamloops volcanics in places into 

 broad anticlinal domes and synclinal basins. Con- 

 tinued erosion in the Pliocene brought the whole belt to a 

 stage of late maturity and local peneplanation. Wide 

 and shallow, trough-like valleys were formed. At the 

 close of the Pliocene or beginning of the Pleistocene, regional 

 uplift took place, and the major streams deeply incised 

 themselves within the uplifted erosion surface. During 

 the Pleistocene, the Cordilleran ice-sheet advanced and 

 retreated, leaving much drift. At least two distinct 

 periods of valley glaciation and alluviation followed the 

 retreat of the ice cap. The disappearance of glacier ice 

 from the valleys increased the eroding activity of the 

 streams which began the dissection of the alluvial gravels, 

 sands and silts. This process of dissection, still active, 

 was probably further aided by regional uplift. 



* Dr. R. A. Daly prefers to give weight to the available paleontological evidence 

 which tends to assign the Kamloops and Tranquille formations to the Oligocene. 

 The time of their warping is accordingly to be described as the interval between the 

 late Oligocene and the Pliocene period; and their extensive denudation is ascribed 

 to work performed through practically all of post-Oligocene time. 



ANNOTATED GUIDE. 



(Savona to Lytton.) 



Miles and 

 Kilometres. 



25-3 m. Savona — Altitude 1,158 ft. (352-9 m.). On 



Savona mountain which may be seen to the 



40-7 km. south of the town, occurs a thick section of the 



(from Kamloops volcanic group. 



Kamloops) In descending order it is approximately as 

 follows : — 



