Appendix III 



Geology of the Area* 



The region is a very typical Archsan or Pre-Cambrian area, near 

 the southern margin of the great Canadian Shield or Northern Pro- 

 taxis of the North American continent, which stretches with almost 

 unbroken continuity to the borders of the Arctic ocean. Ordovician 

 strata, which survive as evidence of the transgression of the Palae- 

 ozoic sea from the south occur as isolated outliers of various sizes and 

 shapes. They form conspicuous steep-faced hills of horizontally 

 stratified rocks in the townships of Lake, Methuen, Burleigh and 

 Harvey, in the south-west angle of the Bancroft sheet. To the south 

 of Stony lake, the northern portions of Dummer and Smith townships 

 are underlain lay the main body of the Ordovician, which forms the great 

 plain stretching southward to lake Ontario and beyond. 



The line of contact between the highly inclined crystalline rocks 

 of the Pre-Cambrian and the horizontal Umestones and sandstones of 

 the Palsebzoic is marked by a very distinct and abrupt change in the 

 character of the country. The Pre-Cambrian region is decidedly 

 rocky and uneven and is thus, in large part, unsuited for purposes of 

 agriculture. It is pre-eminently a grazing country with stretches 

 of imdeared forest land still remaining. In marked contrast the 

 country underlain by Ordovician strata is prevailingly fiat and fertile, 

 well cleared, and occupied by a large farming population. 



In the area covered by the Forest Distribution map, the Laurentian 

 country is imderlain by a diversified series of altered sedimentary rocks 

 among which limestones predominate, resting upon and invaded by 

 enormous bodies of gneissic granite. 



The sedimentary series is largely developed to the south-east, where 

 it is comparatively free from igneous intrusions. Towards the north- 

 west, however, the granite, in ever-increasing amount, arches up the 

 sedimentary series and wells up through it, in places disintegrating it 

 into a breccia composed of shreds and patches of the invaded rock 

 scattered through the invading granite, until eventually connected 

 areas of the sedimentary series disappear entirely and over hundreds 

 of square nailes, the granite and granite-gneiss alone are seen, holding, 

 however, in almost every exposure, inclusions which represent the last 

 scattered remnants of the invaded rock. In addition to these extensive 

 batholiths of granite and gneiss, other rocks of an intrusive character 

 occur. Among the more important may be mentioned gabbros, diorites 

 and amphibolites, in addition to nepheline and other alkaline syenites, 

 with which the corundum deposits are associated. 



♦Extracted from Guide Book No. 2, International Geological Congress, 1913 



