REPORT OF THE CHIEF ASTRONOMER 383 



SESSIONAL PAPER No. 25a 



lites, quartz films and bands are often found parallel to the fissility. Some 

 apparently true quartzites occur. The rocks also show the effects of 

 mechanical deformation. The limestone is in places brecciated. These 

 sedimentary rocks are among the oldest in the district. They are cut and 

 greatly disturbed by the later intrusions of eruptive rocks so that little 

 can now be determined regarding their thickness and original stratigra- 

 phical relationships. They seldom form large continuous bands but 

 generally appear as islands of greater or less extent in the intrusive rocks. 

 They probably form parts of a once extensive series of sediments which 

 covered southern British Columbia.' 



In the sheet accompanying the present report the limestone of the 

 Attwood series is mapped with the same colour as that showing the position 

 of the limestone in the Grand Forks complex. The Attwood limestone is 

 believed to compose all the masses so coloured in the area west of the North 

 Fork of the Kettle river. It is possible that some of the more completely 

 altered greenstones of the belt represent contemporaneous basic lava flows 

 or ash-beds in the true sediments of this group, but on account of the initial 

 difficulty in the field, such greenstones have not been differentiated from the 

 younger volcanics (Phoenix group) on the map. 



As to the age of this unquestionably very thick group of sediments nothing 

 is known with absolute certainty. The present writer is, however, strongly 

 of opinion that Mr. Brock is correct in regarding them as equivalent to the 

 fossiliferous (probably Carboniferous) series of argillitic, quartzitic, and lime- 

 stone rocks occurring in the Rossland mountains. Lithologically the two 

 groups are extremely alike; their distance apart geographically is but slight; 

 and their relations to the respectively associated volcanics and intrusive rocks 

 are strikingly similar. Hence the writer follows Mr. Brock in his tentative 

 correlation of the Attwood series with the Carboniferous system, though of 

 course, recognizing the possibility that some Triassic or even Jurassic sediments 

 may be included in the group as actually mapped. 



Chlorite and Hornblende Schists. 



Mr. Brock has mapped small patches of chlorite and hornblende schists 

 and remarks in the legend that their origin is uncertain. Two of these patches 

 occur in the five-mile belt along the eastern contact of the Midway volcanic 

 formation. Mr. Brock's brief reports do not contain any additional information 

 concerning these metamorphic rocks. They may be the equivalents of certain 

 phases of the Grand Forks schists and, like the latter, may be highly altered 

 masses of the older greenstones of the district. 



Phoenix Volcanic Group. 



The town of Phoenix is situated in the midst of a large though interrupted 

 area of basic volcanics, a series for which the name ' Phoenix group ' has been 

 proposed for the purposes of the present report. At the town itself there is a 



