PRE-CAM BRIAN ROCKS OF NEWFOUNDLAND 



467 



the relations of this series to the beds above and below were not 

 seen. 



The series consists predominantly of thin-bedded, green-gray, 

 dense, hallefiinta-like slates, at least several thousand feet thick, 

 which may be compact without cleavage, or dynamically meta- 

 morphosed, with a resultant well-developed cleavage; and to a 

 lesser extent of green-gray feldspathic sandstones and conglom- 

 erates. The slates often resemble at a superficial glance banded 

 flow rhyolites, but occasional sandy layers betray their true origin. 



The slates may vary from very fine-grained or dense siliceous 

 quartzites to argillaceous slates, or from dense feldspathic quartzites 

 to chertlike feldspathic slates. Thin, intercalated beds and layers 

 of feldspathic sandstone are common, but the predominant char- 

 acter of the rocks is that of a slate. The feldspathic character of 

 the typical slate and its normally fresh, undecomposed character 

 are shown very well by the two chemical analyses which follow. It 

 will be noted that the soda is in excess of the potash, contrary to 

 the usual rule for sediments derived from well-weathered materials, 

 and that the analyses resemble those of certain rhyolites. The 

 high soda content may be due to plagioclases washed in from basic 

 tuffs. 



TABLE III 



Chemical Analyses of Members of Conception Slate Series 



1. Feldspathic slate, near Brigus, Conception Bay. 



2. Feldspathic quartzite, Robinson's Bight, Random Sound, Trinity Bay. 



The sandstones are formed of angular to subangular grains of 

 quartz, fresh plagioclase, orthoclase, rhyolite, plagioclase basalt, 

 and tuffs. The rhyolite fragments exhibit axiolitic, spherulitic, 

 and banded textures. 



