STRUCTUILiL FEATURES OF THE PRE-C AM BRIAN 197 



Mattagami area. — This area (Fig. 11), which Hes on Mattagami 

 Lake, has been briefly examined by the writer, but has been studied 

 in detail by J. A. Bancroft.' The following is a summarized 

 description of the more important points of composition and 

 structure described by him. 



The rocks include, as in the three foregoing areas, an overlying 

 sedimentary and an older lava series. The sediments have been 

 named by Bancroft the Mattagami series. They form a belt under- 

 lying the bed of the lake which outcrops at intervals along its shores 

 over a distance of about fifteen miles. They consist almost wholly 



Fig. II. — The Mattagami area 



of quartz biotite schists, which are probably the metamorphosed 

 equivalent of impure sandstones; these pass into conglomerate in 

 places by the addition of pebbles of all sizes up to six inches in 

 diameter. The pebbles are always scattered, never crowded 

 together as in the conglomerates already described. However, it 

 may be that if the series were better exposed bands of the more 

 characteristic conglomerate would be seen. The deformation has 

 been so great that all the pebbles with the exception of the hard 

 granites have been squeezed, flattened, and in many cases reduced 

 to narrow strings; while even the granites have been much granu- 

 lated and recrystallized. On this account the recognition of the 



^ Report on Mining Operations, Quebec, Department of Colonization, Mines, and 

 Fisheries, 191 2, p. 131. 



