io8 



Kilometres railway is here on the south side of the river, but 

 soon crosses back to the north, and after passing 

 Bradshaw, reaches the town of Hedley at the 

 mouth of Twentymile creek. 



107 m, Bradshaw. — 



172 km. 



112 m. Hedley — Alt. 1,650 ft. (502 m.). 



165-7 km. 



GEOLOGY OF THE REGION ABOUT HEDLEY. 



GENERAL DESCRIPTION. 



Physiography. The Hedley district [2,] lies in the 

 Interior Plateau region of southern British Columbia 

 on the western flank of the Okanagan range of mountains, 

 which is an elongation of the Cascade Mountain system. 

 The plateau occupies the whole of the central part of 

 British Columbia, and is characterized in its upper levels 

 by wide flaring valleys separating broadly rounded or 

 almost flat topped summits which merge together in an 

 almost level sky line, having an elevation in this part of 

 about 6,000 feet (1,827 m.) above sea level. Into the 

 surface of the plateau the master streams have entrenched 

 themselves to a depth of 2,000 feet (609 m.) or more, 

 and now occupy steep sided valleys, which have been 

 modified by valley glaciation to produce the characteristic 

 U-shape typical of Similkameen valley. 



To the long erosion period following the Laramide up- 

 lift is due the uniformity of level of the upper surfaces of 

 the region, while the entrenchment of the streams in the 

 deep valleys is attributed to the period following the uplift 

 of the Interior Plateau and Cascade mountains in late Plio- 

 cene times. A topographic break, occurring about the 

 4,000 foot (1,219 rn.) contour in the grade of the small 

 streams and projecting spurs entering the Similkameen 

 valley, is used as evidence in support of the idea that the 

 degree of uplift in this region during Pliocene times was 

 at least 2,500 feet (762 m.). 



The efTects of both continental and valley glaciation 

 are apparent throughout the region. On the upper levels 

 continental glaciation has accentuated the maturity of 



