SCTMMAET. 219 



rocks are apijareutlv in most cases extremely mashed phases of the granites. 

 They occur only on the borders of the granitic areas, between these and the 

 Marquette sedimentaries. The gneisses consist largely of quartz, sericito, 

 2:)lagioclase, and kaolin. In a few instances rocks with the characteristics 

 of the Palmer gneisses are found at the base of the Marquette series, con- 

 stituting the matrix of conglomerates in which the bowlders are Lu-gelv 

 identical with specimens of Palmer gneisses occurring beneath the con- 

 glomerates. These rocks are regarded as mashed arkoses, derived by 

 disintegration and alteration of the granites, whose mashed and silicified 

 forms the true Palmer gneisses are. The arkoses originally had the same 

 comjjosition as the granites of whose detritus they consist; consequently 

 their altered phases are practically identical with the altered granites them- 

 selves. The area on the map colored for the Palmer gneisses is underlain 

 by those gneisses that are believed to be mashed granites. 



The micaceous and hornblendic schists are evenly banded rocks with 

 a distinct strike and dip. Their banding is often narrow enough to be 

 observed in hand specimens. In other cases the banding is broad, so that 

 it is observable only in the ledges. In thin section a few of the rocks 

 are typically gneissic. In most of them a cataclastic structure is strongly 

 marked. All are more or less foliated, and their foliation, as well as their 

 cataclastic structure, is ascribed to pressure. The liornblendic schists are 

 shown to be mashed basic eruptives, and the micaceous varieties are thought 

 to be mashed acid eruptives; but whether the schists were originally tutfs 

 or massive rocks is not known. 



The schists are older than the granites, since dikes of the latter rock 

 intrude the former in great numbers. Their relations to the greenstone- 

 schists are not known, since contacts of the several kinds of schists have not 

 been observed. If the micaceous and hornblendic schists are older than 

 the green schists, they may represent the basement upon which the latter 

 rocks were laid down. In any event tlie hornblendic and micaceous schists 

 represent the typical Mareniscan formation as defined by Van Hise in his 

 correlation essay, and the granite the Laurentian. 



As in the case of the Northern Complex, no rocks of sedimentary 

 origin have been detected in the Southern Complex. 



