CHAPTER VI. 

 THE STURGEON RIVER TONGUE. 



By William Shirley Baylet. 



DESCRIPTIOlSr AND BOUNDARY OF AREA. 



The Sturgeon River area of Algonkian sediments, like the Felch 

 Mountain area, is an east-west tongue of conglomerates, slates, and dolo- 

 mites, very narrow at its. eastern extremity and widening out toward the 

 west until it finally plunges under drift deposits that separate it from the 

 large Huronian area of the Crystal Falls district. The tongue occupies 

 the western portion of T. 42 N., R. 27 W., the central and northern portions 

 of T. 42 N., R. 28 W., T. 42 N., R. 29 W., and T. 42 N., R. 30 W., and 

 the southern parts of T. 43 N., Rs. 28 W., 29 W., and 30 W. The best 

 exposures of the rocks constituting the tongue are found in sees. 7, 8, 17, 

 and 18, T. 42 N., R. 28 W., and in sees. 1 and 3, T. 42 N., R. 29 W., on or 

 near the northwest branch of the east branch of the Sturgeon River; hence 

 the name Sturgeon River tongue (PL LI). 



On the south the sedimentary rocks are bounded by an area of granites, 

 gneisses, hornblende-schists, and mica-schists, that are cut by granite and 

 quartz veins, by dikes of diabases, and by other greenstones. This area 

 separates the Sturgeon River tongue of sediments from the Felch Mountain 

 tongu -yiug from 2 to 3 miles farther south. The exact line of demarca- 

 tion between the granite-schist complex and the sedimentary rocks is difficult 

 to draw, because for the eastern 7 miles the latter are bordered by green- 

 stones whose position in the granite-schist complex or in the sediirientary 

 series can not be determined at present. The line as drawn on the map 

 places the greenstones in the Archean. It begins near the south side of sec. 

 7, T. 42 N., R. 27 W., and runs a little south of west to the quarter post 

 between sections 17 and 18, in the next town west, then northwest to near 



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