464 . E. L. BRUCE 



In our map sheet there is an interesting series comprised of highly altered. 



sediments which are closely associated with the Keewatin One belt has 



an apparent thickness of one and one half miles and a length of 1 1 miles 



The rocks in the three large areas mentioned in the preceding paragraph 

 consist of slate, greywacke, quartzite, and a little conglomerate, all of which 

 have been altered to schists. Both the cleavage and bedding of the sedi- 

 ments have nearly vertical dips, but there are usually small angles between 

 their strikes. A little chert is also present. Conglomerate schist was seen 



in four localities and, in each case, near the outer edge of the sediments 



The pebbles which are somewhat flattened, consist of quartz porphyry and 

 greenstones, suggesting an unconformity between the sediments, on the one 

 hand, and the greenstones and quartz porphyry on the other. However, the 

 only good contacts which were seen between the sediments and the greenstones 

 were on lot 7 in the second concession of Coulson township and these might 

 suggest that the sediments were interbedded with the pillow lavas of the 

 Keewatin. It may be added that in this locality the banded cherts which 

 appear to be a part of the main group of sediments are older than the pillow 

 lavas. In view of these apparently conflicting observations it is seen that 

 the relationship between the Keewatin lavas and these old sedimentary rocks 

 has not been definitely worked out. Possibly the conglomerates may be of 

 interformational origin or may belong to the Temiskaming series. 



It seems clear that there are two possibilities. Either the 

 lava flows here called Keewatin are in reality much younger than 

 those usually classed as Keewatin, younger in fact than the Temis- 

 kaming series, or there is a great interbanded series of lava flows, 

 tuffs, and sediments. The presence of conglomerate in such a 

 series is quite to be expected. 



LAKE NIPIGON DISTRICT 



In the Kowkash area east of Lake Nipigon, Hopkins^ has 

 found a series of rocks which he calls the Marshall Lake series. 

 This group consists of quartz-mica schists, garnet, and staurolite 

 schists. Hopkins says: 



The chemical composition, microscopic evidence, and frequent occurrence 

 of alternating coarse and fine bands in these quartzose rocks suggest that they 

 are elastics or volcanic fragmental rocks deposited in water. Since they are 

 interbanded with ellipsoidal lavas on Cross lake and contain some iron forma- 

 tion they are apparently closely associated with the Keewatin. 



^ Ann. Repl. Out. Bureau of Mines, Vol. XXVI (1917), p. 206. 



