1:02 .1. B.TYRRELL — POST-TERTIARY DEPOSITS OF MANITOBA. 



Deposits oj Isolated Glaciers. — Afterthe final retreat of the general con- 

 tinental glacier, relatively small neves remained on the tops of sonic of the 

 higher elevations that had previously been overridden, and small glaciers 

 flowed outwards from them down valleys of various depths. The Duck 

 mountain shows many evidences of having passed this intermediate stage of 

 local glaciation. It is a high table-land, the summit of which rises '_\7<)»> 

 feet above the sea, or 2,000 feet above Lake Winnipeg, and consists entirely 

 of Cretaceous clays overlain by a great thickness of unstratified till and 

 transported bowlders, most of the latter being Archean gneisses and schists. 

 From the summit of the mountains several large valleys carry the super- 

 fluous drainage outwards to the various surrounding waterways. The strati- 

 fied deposits in these valleys are in many cases overlain by unstratified till. 

 The valleys are also blocked by small local moraines, behind which in some 

 cases the valleys are terraced as high as the tops of the moraines, while in 

 others the rivers that formerly occupied them have been permanently di- 

 verted into other channels. 



Thus we would appear to have in this area three distinct bowlder clays, 

 two formed by the continental glacier moving southward, and the third or 

 upper formed by local glaciers existing at the same time that the great post- 

 glacial hikes filled all the adjacent depressions. 



Drumlins. ( )ver the great portion of the plains drumlins have not been rec- 

 ognized, possibly in part because in the press of other work they have not been 

 looked for sufficiently; hut. in the northern portion of Lake Winnipegosis 

 many excellent examples are to be seen. They here form groups of narrow, 

 very much elongated elevations in the till, rising in islands a few feel above 

 the sin lace of the lake, and are generally thickly covered with transported 

 bowlders of gneiss and limestone. A very casual glance at these group- of 

 islands will serve to show that they are structurally different from neighbor- 

 ing one- underlain by rock and on which the bowlders have been shoved by 

 the ice. There is do Bign of any rock in place and the stones are not all of 

 constant lithological character, a- is generally the case where the rock is 



close to the -urrace, hut they are t rue transported bowlders, differing as widely 

 from each other a- crystalline gneiss and coralline limestone. The Islands 



are also formed with their long axes parallel to the direction of the glacial Btrise 

 In i lie vicinity. 



Tin-: Aqueoi - I >i posi re. 



Interglacial Deposits. As has been already shown, the evidence- of a re- 

 currence of glacial conditions and the intervening temperate era uear the 

 northwestern limit of the glaciated area have no room for doubl that the 

 glacier retired tor a considerable time from the greater pan of the western 

 prairie region ; and perhaps during this interglacial period conditions may 



