90 



The hills immediately behind the road-house 

 at Yukon Crossing, consist of dark greenish 

 andesitic rocks which appear to be somewhat 

 extensively developed in that locality. Below 

 Yukon Crossing, 5 and 6 miles respectively 

 (8 and 9-6 km.), Merritt and Williams creeks 

 join the Lewes on its left limit. Up these 

 creeks and within a distance of 3 miles (4 • 8 km.) 

 from the river, a number of copper claims 

 have been located and have been more or less 

 developed [12]. The rocks throughout the 

 Williams and Merritt Creeks area, and for 

 several miles at least down the Lewes, are 

 mainly much altered, dark green, sheared 

 eruptives and granitic rocks. The older sheared 

 members have a pronounced schistose structure 

 and belong to the older pre-Ordovician rocks. 

 These have been here so extensively invaded 

 by the granitic intrusives, that the two appear 

 to be about equally extensive in this vicinity. 



Hoo-che-koo bluff [28, p. 144B-146B], which 

 is situated on the right limit of the river about 

 11 miles (17-5 km.) below Yukon Crossing, 

 and which is the abrupt face of an isolated 

 hill against which the river washes, consists 

 of a grey, slightly porphyritic, felspathic rock 

 which is interbedded with fine grained, nearly 

 black argillite. These rocks are much fractured 

 and distorted, and probably are of lower Paleoz- 

 oic age. 



Below Hoo-che-koo bluff for about 25 miles, 

 (40 km.) the few rock exposures along the 

 river consist mainly of diabase or diorite and 

 diabase agglomerates. About 10 miles (16km.) 

 above Selkirk some greyish granite outcrops, 

 which in places contains large porpyhritic 

 feldspar crystals. This granite is similar to 

 that in the vicinity of Williams and Merritt 

 creeks, and is probably related to the Coast 

 Range granitic intrusives. 



Commencing about 6 miles above Selkirk, 

 the Tertiary basalts are again developed, and 

 from there extend downstream for over 30 miles 

 (48 km.) Several superimposed flat-lying flows 

 occur, giving rise to a wide basalt plateau. 



