KlSsUMlS, AND GENEKAL DISCUSSION. 



557 



latter series, and not formiiig 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 sliown to be coincident with the stratification. Now if the Lauren- 

 tian 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 country 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 Laurontian. Cut 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 stratigraphical observations of eitiier 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 

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

 well known to bo 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 

 arc by every geologist placed in the same series. 



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

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

 the lowest fossiliferons scries — is this: the axial or eruptive portions 

 of disturbed and mountain regions are largely granitic and gneissoid in 

 cl)aractcr. Tlicsc granitic, granitoid, and gneissic 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 furuisJiing the material from which the sedimentary forma- 

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

 alUed to the distinctly granitic and not necessarily metamorphosed strati- 

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



* Notes 01) the "Life of Sir W. E. Logan," 1883, p. 3. 



