78 



side of the lake, belong to the Laberge Jura- 

 Cretaceous series, and consist dominantly 

 of conglomerates, sandstones, shales, gray- 

 wackes, and tuffs. [13, pp. 30-35. Also see 

 included map of " Braeburn-Kynocks Coal 

 Area"]. 



Terraces are quite conspicuous along the 

 lake in places, and occur at various elevations 

 up to 350 feet (100 m.) above the water. These 

 are similar to the terraces noted along Lake 

 Bennett and at other points south of White- 

 horse, and have had a similar origin. Corres- 

 ponding terraces may be seen in many places 

 along Lewes and Yukon rivers between Lake 

 Laberge and Dawson. 



The valley walls on both side s of Lake 

 Laberge to near the level of the general upland 

 show evidence of pronounced glacial activity, 

 the rock surfaces in many places, particularly 

 along the eastern side of the lake being so 

 smoothed, polished, and striated that it 

 is difficult to walk over them. 



170 m. Lower Laberge — A broad prominent depres- 



272 km. sion, the Ogilvie valley, joins Lake Laberge 

 at its extreme northwestern corner, and is 

 evidently the valley thiough which Lewes 

 river flowed in pre-Pleistocene time. During 

 the glacial period it became so filled with gravels, 

 sands, silts, etc., that after the retreat of the 

 ice the river was forced to find a new outlet. 

 The river at the lower end of the lake now 

 turns to the northeast and breaks through 

 an opening in the hills on that side, and to 

 Hootalinkwa, at the mouth of Teslin river, 

 does not follow any marked valley, but flows 

 through a confined depression among irregular 

 lumpy hills, seldom over 1,000 feet (300 m.) 

 above the river. This stretch of river, which is 

 about 30 miles along (48 km.) and is locally 

 known as Thirtymile river, has a general 

 trend somewhat east of north, is very tortuous, 

 and is characterized by its swift, beautifully 

 clear water, — the lake above acting as a huge 

 settling tank from which the water emerges 



