THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE II 



seemed likely to disclose relationships typical of a much larger sur- 

 rounding region, were in brief some of the factors controlling the 

 selection of the Canton cjuadrangle as a field for the determination, 

 so far as circumstances would permit, of the space and time rela- 

 tions of the various igneous and metamorphic rocks there exposed. 

 Glacial deposits are present over part of the quadrangle in suffi- 

 cient quantity to make the detailed study and precise mapping of the 

 Precambrian frequently impossible. The central belt, crossing the 

 area from west to east, is particularly unfavorable in this re- 

 spect; in its western part, to be sure, the boundaries of the larger 

 formations can be determined with a fair degree of approximation ; 

 but in the center and on the opposite side of the zone, even this is 

 impossible. In the southernmost belt, however, the conditions are 

 quite different. Except for two or three high-level glacial lake de- 

 posits, the county is practically free from debris, and outcrops are 

 abundant. Bearing in mind, therefore, the varying restrictions 

 imposed by glacial activity upon the accurate mapping of the bed- 

 rock of the quadrangle, the distribution, nature and structural rela- 

 tionships of the rock units composing the Precambrian terrane wir 

 now be described. 



