2o8 W. H. COLLINS 



eluded that following Timiskaming time the whole region, shown in 

 Figure 3, was mountain-built. The southern portion was long 

 afterward involved in the Killarnean mountain-building and, in 

 that part, any evidence of this earher orogeny was pretty completely 

 demolished; but there is httle doubt that the older mountains 

 extended over the whole region. 



Between the finish of Timiskaming sedimentation and the 

 commencement of the Bruce period these older, pre-Huronian 

 mountains must have been uplifted, carved, and completely des- 

 troyed, for the Bruce series hes upon a peneplained surface evidently 

 quite as maturely eroded as the surface of today. The evidence 

 for this has been discussed at length in various Geological Survey 

 reports,' and need not be repeated. Attention need be directed 

 here only to the length of time required for this complete physio- 

 graphic cycle; the Appalachian Mountains, which are not yet 

 nearly so completely leveled, have existed since Permian time. 



Just as the Killarnean mountain-building demolished in the 

 southern part of the region the evidence of earlier geological history, 

 so it might be expected the pre-Huronian mountain-building, which 

 extended over the whole region, would have obhterated all of the 

 geological record anterior to the deposition of the Dore series. 

 This is not wholly the case. When the Timiskaming series was 

 first described by W. G. Miller,^ he noted that it contained granite 

 pebbles. Many years before, Logan noted the presence of granite 

 bowlders in the Dore series, though, at that early stage in Canadian 

 geological work, he could not be sure of the position of this series 

 in the geological scale. These granite inclusions in the oldest 

 known sediments have afforded ground for much speculation regard- 

 ing the nature of the surface from which they were derived, and 

 upon which they were deposited. 



It was not until 1920 that the ancient granite which supplied 

 these pebbles was identified in situ beneath the Dore series, near 

 Michipicoten Harbor. At that place the Dore series lies tilted at 

 an angle of 50° or more against a basement of older rocks, from 



' M. E. Wilson, Geol. Surv., Can., Memoir No. 39; W. H. Collins, op. cit., Memoir 

 Nos. 33, 95, and another not yet published. 



• ' Ann. Rep. Ontario Bureau of Mines, Vol. XIX, Part 2, p. 62. 



