DESCRIPTION OF THE AREAS 277 



The series is interpreted as one of conformable sediments interbanded 

 with volcanic rocks, 



KNEE-OXFORD LAKES DISTRICT'' 



In the Knee Lake district a complex of volcanic and sedimentary rocks 

 is intruded by stocks and batholiths of granite. The solid rocks are 

 thickly covered by Pleistocene and Eecent de]3osits, and outcrops are 

 neither large nor continuous. Hence the relationships of the different 

 formations must not be considered as unquestionably determined and the 

 succession suggested may require some modification. 



Table of pre-Gambrian Formations 



Granite. 



(Intrusive contact.) 



Quartz-porpliyry dikes. 



(Intrusive contact.) 



Pre-granite complex Upper part. Lavas, tuffs, and volcanic f rag- 

 mental rocks, with some sedi- 

 ments. 

 Lower part. Conglomerate slate graywacke. 

 Biotite gneiss, etcetera, witli 

 some lava flows. 



Lithological Characters 

 Pre-Granite Complex, Lower Part 



The lower part of the pre-granite complex is dominantly sedimentary 

 in origin, but volcanic fragmental rocks and some lavas are interbedded 

 with the sediments. The sedimentary beds are heterogeneous in character 

 and seem to be variable from place to place along the strike. The various 

 types include biotite gneiss, garnet gneiss, massive biotite rocks, slate, 

 impure quartzite, and conglomerate. The gneisses and the massive biotite 

 rock are the most commonly exposed, because most resistant. The biotite 

 gneiss is a grayish rock that weathers a dull brownish gray. It is well 

 banded, and weathered surfaces show the banding prominently due to 

 difference in the hardness of the laminations. In places the harder layers 

 are attacked transversely, leaving them merely as rows of conical eleva- 

 tions. 



Under the microscope the mica schists are found to consist largely of 

 quartz grains, many of which show distinct rounding. The biotite is 

 arranged in parallel position. Some foils lie between the quartz indi- 

 viduals,, but much of it penetrates the quartz and is apparently secondary 



^ E. L. Bruce : Knee-Oxford area. Geol. Surv. Can., Sum. Kept., 1919. 

 XIX — Bull. Geol. Soc. Am., Vol. .32, 1920 



