THE PALMEK GNEltiSKS. 213 



places the liandin<;- is even, while in otliers it is nutcli contorted, where 

 lenses and veins of quartz and narrow dikes of" red s^ranite are interposed 

 between the bands. As the granite area to the south is approached the 

 number of granite dikes in the schists increases, and these rocks themselves 

 become more and more massive. On the north side of Lake Palmer the 

 relations of the dikes to the schists are well seen in the almost perpendic- 

 ular side of a high cliff. Here great dikes of red granite cut the schists in 

 all directions, although there seems to have been a preference for a direc- 

 tion parallel to their foliation. On the ledges south of the lake, numbers 

 of naiTOW parallel dikes of the same red granite occur between layers of 

 hornblende-schists and mica-schists, producing on smooth ledges a banded 

 structure of great beauty. 



There seems to be no question but that most, if not all, of the gneisses 

 south of Summit Mountain are properly members of the granite-schist 

 series. The banded structure that has been noticed in most of them is due 

 in part to the banded character of the schist-granite complex from which 

 they were derived. 



The schists with the characteristics of the Palmer gneisses therefore 

 include foliated rocks of Algonkian age (in the neighborhood of the 

 Piatt mine) and others belonging to the Basement Complex. The line 

 between the two, as drawn on the maps, is as accurately located as is 

 possible after making a very thorough examination of all the ledges in its 

 vicinity. Where well-defined conglomerates occur the line is drawn just 

 beneath these, and the schists accompanying the conglomerates are placed 

 Avhere they belong, in the Marquette series. Where no conglomerates are 

 found and nothing is discovered, either in the field or under the microscope, 

 to indicate that the gneisses Avere once fragmental, they are placed in the 

 Basement Complex, and the line is drawn above them. The Palmer 

 gneisses of the area represented on the map (Atlas Sheet IV) are therefore 

 regarded as members of the Basement Complex. (The meaning of apparent 

 gradations between unconformable series is described in another place; 

 see pp. 298-299). 



PETROGRAPHICAL CHARACTER. 



The key to the origin of the Palmer gneisses is discovered in the 

 study of the altered mosaic between the large fractured fragments of 



