328 Revieus — Geological Survey of Canada. 



along the escarpments of some of the plateaux that the older rocks 

 are shown. The basal glacial beds are stratified sands and gravels 

 overlain by Boulder-clay, and this in places is covered by drift 

 gravels. In some of these latter there are masses of the Tar-sands, 

 which have been transported by the glacier, and Mr. McConnell 

 discovered portions of this material on the plateau summit of Birch 

 Mountain, which could only have been derived from the exposures 

 in the Athabasca Valley at a lower level of many hundreds of feet. 

 Accompanying the report of this district are several photographs, an 

 index map, and sections. 



Another elaborate and interesting report is that by Mr. J. B. 

 Tyrrell on North- Western Manitoba, including portions of the 

 adjacent districts of Assineboia and Saskatchewan. The oldest rocks 

 of this district are Silurian, mainly limestones and dolomites, with 

 characteristic fossils of Niagara age, which are shown near the 

 mouth of the Saskatchewan on the west side of Lake Winnipeg, and 

 also along the eastern shores of Lakes Winnepegosis and Manitoba. 

 On the western borders of these lakes there is an extended belt of 

 Devonian rocks, from 400 to 500 feet in thickness : the lower portion 

 of these are red shales, which are overlain by thick beds of dolomites 

 containing numerous fossils, amongst others the well-known brachio- 

 pod String ocepJialus Burtini, and these are succeeded by limestones 

 and shales of Upper Devonian age. Brine springs are met with in 

 certain areas of the Devonian, west of L. Winnepegosis. 



As in the Saskatchewan region, 500 miles further west, there is 

 here also a tremendous break in the geological succession, so that 

 the Devonian rocks are immediately succeeded by Cretaceous shales 

 and sandstones, of which the country to the west of the lake region 

 is mainly formed. The lowest beds are Dakota sandstones, about 

 200 feet thick ; these are overlain by verj'^ dark shales of Benton age, 

 about 180 feet in thickness, followed by grey calcareous marls or 

 shales, occasionally passing into limestones, belonging to the Niobrara 

 division. These beds contain numerous Foraminifera, amongst which 

 Globigerina cretacea is the most conspicuous species. Some layers 

 are largely composed of the microscopic prisms of disintegrated 

 shells of Inoceramus. The scales, teeth, and bony fragments of 

 fishes are likewise abundant in these Niobrara shales, and Mr. 

 Tyrrell discovered a thin band or bone-bed largely made up of 

 these remains, which yielded on analysis 37 per cent, of phosphate 

 of lime. Above the Niobrara beds are the grey soft shales of the 

 Pierre division, which occupy the higher lands of the Riding, Duck, 

 and Porcupine mountains, and reach a thickness of about 1000 feet. 

 Some of these shales are highly siliceous, and they contain numerous 

 Eadiolaria, which have been determined by Dr. Riist. 



The harder rocks round the lakes of this district show very 

 distinctly the glacial strias, the direction of which ranges for the 

 most part to the west of south. As an instance of the way in which 

 the course of the glacier has overridden the slope of the country, 

 Mr. Tyrrell records the occurrence of large boulders of Dakota 

 sandstone which have been carried to a level of 450 feet above that 

 of the parent rock, the nearest bed of which is 40 miles distant. 



