STRUCTURAL FEATURES OF THE PRE-CAMBRIAN 195 



mica gneiss, identical in composition with the corresponding gar- 

 netiferous gneiss of the Nemenjish series on the Opawika River. 

 Below this, in scattered outcrops, were observed basalts, basic 

 intrusives, tuffs, and carbonate schists. 

 The succession in this area is therefore: 



Broadback series, sandstone, now muscovite schist, arkose or greywacke, 

 conglomerate 



Unconformity 

 Nemenjish series, garnetiferous mica gneiss 

 Basic intrusives, basalts, tuffs, carbonate schists 



Kenoniska area. — This area (Fig. 10) lies at the north end of 

 Kenoniska Lake, on the Broadback River. It was mapped in part 

 during the work of 191 2. The map published at that time included 

 the results of information gained by an earlier observer, which 

 re-examination by the writer in 1914 proved to have been incorrect. 

 As a result the formation boundaries shown on the map of 191 2 

 are not to be accepted as final. 



The geologic section in this area is very similar to that found 

 in the Lucky Strike area, but is of more value, partly because the 

 section is better exposed and more complete, and partly because 

 undeformed rocks are to be found. The structure of the area is 

 that of an anticline about ten miles in width, both limbs of which 

 are cut off by granite. The anticline plunges to the east. The 

 rocks on the limbs are very much sheared, but at the crest of the 

 anticline, which is seen about five miles above Kenoniska Lake, 

 the shearing has been so slight that even the slightest foliation 

 can barely be detected. 



The uppermost series, which was termed the Broadback series 

 by the writer in 191 2, consists of sediments which lie unconformably 

 on an older series consisting mainly of lavas. At the base of the 

 sedimentary series there are two heavy bands of conglomerate, 

 separated by a thick band of fine-grained greywacke containing 

 occasional pebbles. Above the conglomerate occur in order 

 arkose, a thin band of quartzite, and mica schist. The latter 

 includes both muscovite and biotite schists, of which the biotite 

 schists are the larger in amount. The muscovite schists are prob- 

 ably the metamorphosed equivalent of very siliceous shales, the 

 biotite schists of less siliceous shales. 



