190 THE MAliQUETTE IRON-BEAIMNG DISTRICT. 



exhibit proof tliat tlu'\- once existed as igueous magmas, from which they 

 were formed bv cooling, so that in their present condition they are all of 

 igneous origin. Not a sediment of any kind has been detected among them. 

 In this respect the Northern Complex differs essentially from the Marquette 

 Algonkian, which consists almost exclusively of well-preserved sediments. 

 The relations of the granites and the gneisses to the greenstone-schists 

 are those that obtain between the Mareniscan and the Laurentian series 

 of Van Hise, the greenstone-schists representing the Mareniscan, and the 

 granite-gneisses the Laurentian. Nothing corresponding to Adams's Gren- 

 ■vdlle series has yet been discovered in this district, and perhaps nothing 

 corresponding to his Fundamental Gneisses. 



SECTIOX II.— THE SOUTHERN COMPliEX. 



So far as our studies have g'one it has l)een found impossible to map 

 the rocks of the Southern Complex even as definitely as has been done 

 in the case of the Northern Complex. Except in its eastern portion, there 

 are no large distinct areas in that part of the southern district studied 

 that are occupied almost exclusively by one kind of rock. Most of the 

 area is occupied by granites, gneisses, hornblendic and micaceous schists, 

 and greenstone-schists, together with the various acid and basic eruptives 

 that intrude them. 



The relations existing between the rocks of the Southern Complex 

 and those belonging in the ^larquette series are referred to at the proper 

 places in connection with the discussion of the lowermost beds of the 

 Alg-oukian. Where their contacts are seen there are found marked uncon- 

 formities between the two series, as will be explained later. At other places 

 the crystallines, as well as the fragmental rocks, are mashed to such an 

 extent that it is difficult to draw a line between them. Along such con- 

 tacts there are often developed light-colored sericitic schists and gneisses, 

 whose origin is problematic. At many other places, notabh' in Rs. 27 and 

 28 W., the granites and schists are separated from the Algonkian sedi- 

 ments by a strip of country devoid of ex[)osures. Often swamps intervene 

 between the last outcrops of the bedded roc^ks and the first ones of the 



