CONTACTS OF ARCHE-AX WITH PALEOZOIC ROCKS. 3()o 



than at present. The middle Silurian inlier in the great orographic de- 

 pression of lake Temiscaniing on the Ottawa, which will be again referred 

 to, is another example of these newer and undisturbed strata occup^ying 

 ground much below the general level of the surrounding country. 



On the north shore of lake Huron, between Killarney village and 

 Spanish river, and again on Grand Manitoulin island, in the vicinity of 

 Sheguenda and westward of that village, the Lower Silurian strata rest 

 almost horizontally upon the flanks of bold bare ridges of quartzite, the 

 stratification of which stands nearly vertically. The angles of slope of 

 the ancient rock-surfaces exposed to the weather along the crests of these 

 ridges are continued, as far as can be observed in sections, under the 

 newer rocks forming their flanks, so that the former represent only the 

 upper parts of ridges, once much higher, but now partly buried under 

 the strata w^hich accumulated around them in Silurian times. A high 

 ridge of quartzite runs along the north side of Frazer bay, and a similar 

 ridge, but less elevated, forms the northwest side of Killarney bay. The 

 summits and sides of these ridges are, for the most part, thoroughly 

 smoothed and striated by glaciation, but near their southern bases occa- 

 sional spots are found which have escaped the action of the ice and which 

 show evidence of great antiquity, the flinty rock being worn into pits 

 and hollows, but with no sign of granular or textural disintegration. A 

 broken fringe of Black river limestone skirts the base of the quartzite 

 range on the northwest side of Killarney bay, and the erosion of the 

 spots referred to may be of pre-Paleozoic date, having been preserved till 

 now by a thin limestone covering, or they may represent portions of the 

 surface as it existed immediately before the glacial epoch which have 

 escaped the smoothing action of the ice, but this is not so likel3^ 



In the neighborhood of the quartzite ridges only those beds of the 

 newer rock which are in contact with the old formation contain angular 

 fragments of the rocks on which they lie. The layers containing this 

 debris are usually of no great thickness and the fragments themselves 

 are of small size; but close to Sheguenda, to the north and south of the 

 village, are pretty thick strata composed of sharply angular pieces of 

 quartzite of all sizes packed closely and confusedly together, with only 

 enough calcareous cement to consolidate them. This locality is about 

 twenty miles south of the main Huronian area left uncovered by Silurian 

 strata and the water of lake Huron. 



On La Cloche island and elsewhere in the vicinity numerous ridges 

 and domes of Huronian quartzite protrude throu^j^h the flat-lying Silu- 

 rian limestones and shales, so that the former resemble masses which 

 have been forced up through them from below, whereas they are only 

 higher portions of the old sea bottom, around which the horizontal beds 



