378 THE GLACIAL LAKE AGASSIZ. 



ou the east and nortli were merged in one, and the ontflow from the lake so 

 formed passed south tlu'ough the Tiger Hills to Langs Valley i;ntil that 

 channel was cut down nearly to 1,350 feet. During this stage of a contin- 

 uous lake east and north of the Brandon Hills, this independent part of 

 Lake Agassiz, before it was merged with the main body of this lake by the 

 recession of the ice from the east end of the Tiger Hills, received an exten- 

 sive delta, already described as the highest portion of the Assiniboine delta 

 in the vicinity of Brandon and Kemnay, consisting partly of modified drift 

 from the retreating ice and partly of fine sand and silt brought by a stream 

 then flowing east from the Lake Souris delta along the Big Slough. The 

 tribute of the latter is spread over an area of several square miles south- 

 west of Kemnay, and upon it are raised the conspicuous dunes of sections 

 6 and 7, township 10, range 20. With the retreat of the ice northward 

 from Treherne, the Brandon lake was lowered nearly 100 feet to the level 

 of Lake Agassiz in its Herman h stage. For a short time the Souris prob- 

 ably continued to flow southeastward through Langs Valley until the 

 deposition of the alluvium, perhaps 10 or 15 feet thick, brought into that 

 valley by Dunlops Creek, 4 miles east of the elbow of the Souris, raised a 

 barrier a few feet higher than the g'ap that had been cut through the Tiger 

 Hills north of the elbow, whereby the river was turned through this gap, 

 which it has since eroded 100 to 150 feet deeper. 



The modified drift and alluvium that form the plain of coarse gravel 

 and sand sloping eastward from Kemnay to Brandon and reach along the 

 north side of the Assiniboine to Douglas were pi'obably deposited mostl)' 

 while the barrier of the waning ice-sheet stretched from the Tiger Hills to 

 Riding Mountain, inclosing on its west side a lake that afterwards became 

 the bay of Lake Agassiz covering the Assiniboine delta, but was then held 

 about 100 feet above Lake Agassiz, to which it outflowed by the way of 

 Langs Valle}^ and the Pembina. Tlie deposition of this highest part of the 

 Assiniboine delta, lying above the Herman hh beach obsei'ved in Brandon, 

 appears to have been in progress tlirougli a consideral)le period, beginning 

 when this Brandon glacial lake was held at an elevation of about 1,400 

 feet, and continuing while it was lowered nearh" 150 feet. During this 

 time the Brandon Lake had three outlets: first, from its two j)arts, respec- 



