GLACIAL ORIGIN OF HURONIAN ROCKS 



465 



would be largely detritus from these old greenstones and cherts; 

 but such is by no means the case. The basal portion is made up 



Fig. 6. — Huronian conglomerate on Keewatin slate. Near Temagami. Ont. 



Fig. 7. — Coarse conglomerate on greywacke (Huronian). Temagami, Ont. 



very largely of material similar to that which inclosed the old valley; 

 but the greater portion of both bowlders and matrix is quite different. 

 There are not now exposed any near-by hills from which these mate- 



