PALEOZOIC ROCKS OF THE CANTON QUADRANGLE II 



Potsdam Sandstones 



This name is here used in the plural because of the growing 

 probability that the formation as at present understood is not a 

 unit, and also because of its varied lithologic expression. 



The exposures of these rocks within the quadrangle are limited 

 entirely to outliers, unless those in the Grass river near the county 

 house (locality 69) are connected with the main mass of Paleozoic 

 rocks on the north. The remaining outcrops are isolated from 

 the general embed, forming scattered patches whose relations and 

 character are of peculiar interest. 



One of the most extensive of these Potsdam outliers lies about 

 two miles south-southeast from Canton village (localities 76 to 

 80) but is badly drift covered, with the outcrops in five or six 

 separated groups that bear little resemblance to one another. At 

 locality JJ all the exposures show the white saccharoidal sand- 

 stone of the upper " Potsdam " dipping uniformly southward about 

 5 degrees, without any sign of faulting. The actual contact with 

 the vertical reddish quartzose Grenville rocks beneath is seen at 

 the north end. One-half of a mile south, at locality 76, are glaciated 

 ledges of a much more indurated red quartz sandstone full of micro- 

 faulting, forming an " autoclastic " rock. The lowest ledge is very 

 red typical Potsdam ; higher up are hematitic iron spherules in a 

 whitish layer; banding is common and some of the most brecciated 

 portions are gray rather than red. In the field to the east a small 

 surface just above the soil is flesh pink, its glacial polish like glass 

 indicating intense induration. In attitude, these beds of locality 76 

 appear to surmount the white layers of the previous locality, but 

 in every other way they look to be much older and it seems safe 

 to assume that the dip changes in the interval, if indeed the two 

 formations are not totally unconformable. 



One and one-fourth miles due east, at locality 80, it is possible 

 to work out a fairly strong anticline and syncline in rather similar 

 indurated and microfaulted beds of various red, buff and leaden 

 colors, as is shown in the cross-section diagram of this locality in 

 pocket. This diagram, drawn to scale without exaggeration, shows 

 the true dips, at some points exceeding 30 degrees. A core of red 

 jaspery quartzite protrudes through layer C at the east end north 

 of the line of section. Not far southwest of the west end, across 

 the brooklet, is a small exposure of white to p nk sandstone more 



