RESUME, AND GENERAL DISCUSSION. 557 



latter series, and not forming basement conglomerates. All the other 

 so-called proof of unconformity has been made out of the fact that the 

 strike of the foliation in the two formations when not in contact has 

 been found to be discordant — worthless evidence unless the rocks ob- 

 served in both formations be proved to be sedimentary and the foliation 

 be shown to be coincident with the stratification. Now if the Lauren- 

 tiun was an old metamorphosed sedimentary formation which had been 

 upheaved and contorted, and on whose worn edges the Huronian had 

 been laid down, the evidence of the fact ought to be overwhelming in 

 amount after the counti-y has been studied for so many years. Wher- 

 ever the Primordial is found in contact with the Azoic, the basement 

 conglomerates and the worn edges of the older Azoic are to be found, 

 and a like condition should be observed if the Huronian is distinct from 

 the Laurentian. But such is not the case, even Selwyn going so far as 

 to declare that the supposed unconformity' cannot " be said to be based 

 on or in accord with the stratigrajihical observations of either Logan, 

 Murray, Bell, or myself."* 



It is well known that any eruptive rock so soon as it comes in contact 

 with erosive agencies will yield fragmental material even before it is 

 cold, and that much eruptive matter is ejected in a fragmental state, so 

 that in a mixed series of eruptive and detrital rocks nothing is more 

 common than to have the debris of one enclosed in another, without 

 thac enclosure proving that the rocks differ in geological age. This is 

 well known to be the case with the copper-bearing rocks of Keweenaw 

 Point, and it has been shown that the iron ores of the Marquette dis- 

 trict, which form a constituent part of the so-called Huronian, are over- 

 lain by a conglomerate containing the debris of the former — yet both 

 are by every geologist placed in the same series. 



The basis of fact which forms the main support of the twofold division 

 of the Archfcan — including under that designation all rocks lying below 

 the lowest fossiliferous series — is this: the axial or eruptive portions 

 of disturbed and mountain regions are largely' granitic and gneissoid in 

 character. These granitic, granitoid, and gueissic masses are brought to 

 light in the cores of great mountain chains, where long-continued uplift 

 of the original crust of the earth has, through a succession of geological 

 ages, been furnishing the material from which the sedimentaiy forma- 

 tions were built up. That the gneissic or gneissoid rocks are closely 

 allied to the distinctly granitic and not necessarily metamorphosed strati- 

 fied deposits is clear to us, as the result of long-continued investigations 

 * Xotes on tlie ^'Life of Sir W. E. Logan," 1SS3, p. 3. 



