Sf. Pe/er's Sandstone. 



1 29 



forced to conclude that this formation is a greatly augmented 

 development of the St. Peter's sandstone ; or, that the Lower 

 Magnesian limestone (" Calciferous sandrock") has thinned 

 out, so as to leave the St. Peter's sandstone and the Potsdam 

 below (as developed in the Mississippi valley) to go on as one 

 mass to the northward." 



"It is scarcely possible to suppose that the lower sandstone 

 'of the upper Mississippi Valley has not, at some time or in 

 some form extended as far as Lake Superior ; but it is far 

 from being proved that the sandstone now so largely developed 

 on the south shore is that sandstone, as we have shown. If 

 this sandstone consist of both that above and that below the 

 Calciferous, or of the St. Peter's and the Potsdam proper, then 

 at some point we should expect to find a change of character, 

 or nonconformity between the beds, to indicate the lapse of 

 time in the deposition of the Lower Magnesian limestone of 

 more southern localities ; and this view is sustained by the 

 observed want of conformity between the sandstone and 

 Magnesian limestone near Dead River just cited. "* 



The question is here left in an unsatisfactory condition; 

 but if the later conclusions, f that the Lake Superior sand- 

 stones are Potsdam or pre-Potsdam in age be sustained, it is 

 probable that the St. Peter's formation will be confined to a 

 narrow strip through the northern peninsula from the 

 Menoninee to St. Mary's River. 



Hall asserted the same again in 1869,! as did also Logan |] 

 in the map of Canada in 1865. 



In referring to the sandstone east of Keweenaw Point, 

 sometimes called the Eastern sandstone, Dr. Alex. WinchellS 

 considered it as the probable equivalent of the Calciferous 

 and Chazy formations of Xew York. He says, in regard to 

 the Lake Superior sandstone as a whole : " The portion west 

 of the Point is thought by some to be of the same age 

 [Calciferous and Chazy], while others regard it as the equiva- 



:; Ibid, pp. 215-216. 



flrving. R. D. : Copper-bearing rocks of Lake Superior. Monographs U. S 

 Geological Survey, Vol. V, 1883. 



JAm. Phil. Soc. Trans., new ser., Vol. XIII. p. 329. 



Atlas accompanying the Geology of Canada from the commencement to 1S63. 

 1865. 



^Sketches of Topography, Climate and Geology of Michigan. Waiting's Atlas 

 of Michigan, 1873, p. 46. 



