153 



TABULAR RESUME. 



The major events in the geological history of this 

 region so far as they have been interpreted may be sum- 

 marized as follows: — 



Time. Event. 



Keewatin Protracted vulcanism, with minor deposition 



of banded iron formation and other obscure 

 sediments. 

 Unconformity, erosion and probably batholithic intrusion. 



Lower Huronian Deposition of conglomerate, greywacke and 



slate with contemporaneous vulcanism. 



Laurentian Orogenic disturbance of Keewatin and Lower 



Huronian rocks, with intrusion of granite 

 batholiths. 

 Great unconformity; peneplanation. 



Keweenawan Deposition of conglomerate, sandstone and 



dolomite; later intrusion of diabase sills. 



Ordovician Marine submergence and deposition of impure 



limestone in the western part of the region. 

 Unconformity. 



Pleistocene Glaciation, formation of glacial lakes, ice 



retreat. 



ANNOTATED GUIDE. 



Winnipeg to Nipigon. 



BY 



W. H. Collins. 



Miles and . ; 



Kilometres. 



o m. Winnipeg — Altitude 763 ft. (232-7 m.). For 



o km. 55 miles (88 km.) east of Winnipeg the railway 



pursues a direct course across flat prairie coun- 

 try, almost treeless for the first 25 miles (40-2 

 km.), but becoming more and more thickly 

 forested as the Pre-Cambrain shield is ap- 

 proached. This is the bed of glacial Lake 

 Agassiz. The slight amount of excavation 

 required by railway construction in this alluvial 

 plain, whose local relief does not exceed 20 feet 

 '6-5 m.), nowhere exposes the Ordovician 

 bed rock. It only shows from one to four feet 



