340 POSITION AND EQUIVALENCY. 



Deposits of bog iron ore are not infrequent in low lands upon this formation. The iron has been derived 

 from the sandstones and the limestones, much like the iron of tertiary age. 



Geological Position and Equivalency. 



For the position of the red sandrock series we need only to refer to Figs. 167, 230, 234, 

 and Sections VIII. to XIII. Without an exception it rests upon the Hudson River Group. 

 The stratigraphical evidence goes to show that the red sandrock is of the age of the Me- 

 dina sandstone or Oneida conglomerate. This was the original view of Prof. Emmons, 

 and has since been sustained by Professors C. B. Adams, W. B. Rogers, and Sir W. E. 

 Logan. It is certainly an objection to this view that the characteristic fucoid, Arihropliy- 

 cus Jfarlani, of the Medina sandstone, has never been found in it. 



Professor Emmons originated a different view after the adoption of his Taconic system, 

 and regards it, sometimes as the calciferous sandstone, and sometimes the Potsdam sand- 

 stone. He did not rely, however, upon Palseontological evidence, but upon its strati- 

 graphical relations to the black slate of the Taconic system. 



The Canada Survey provisionally named the prolongation of the red sandrock into 

 Canada " the Quebec Group." One hundred and thirty-seven species of fossils, having a 

 primordial aspect, have been obtained from this group at Point Levi, near Quebec ; and 

 the Survey have changed their views respecting its age, and now agree with Prof. Em- 

 mons in placing it at the base of the Lower Silurian system. These views are proclaimed 

 in a letter from Sir Wm. Logan to Barrande, published in this Report under the "Georgia 

 Slate." If the view taken by this letter be adopted, it will be necessary to suppose the exist- 

 ence of a great fault, extending from Quebec through the whole of Canada and Vermont, and 

 perhaps to Alabama. Its course through Vermont would correspond very nearly to the 

 western boundary of the red sandrock formation. 



It seems that the conocephalits, one of the most important genera in establishing the 

 primordial character of the Quebec group, was discovered in Vermont by Messrs. Z. 

 Thompson and S. R. Hall, in 1847, long before its discovery in Canada, and before its 

 value in palseontological research was known in Europe. (See Prof. James Hairs letter to 

 C. B. Adams, on page 339.) Had the specimens been more perfect they would have been de- 

 scribed long ago, and might have started the present controversy earlier than its recent 

 inception. 



We have used the name of red sandrock for this series of strata, that our Survey 

 may not be committed to either side of the discussion before the result is clear to 

 every mind. And we have presented the arguments in full upon both sides of the 

 controversy, so that our readers may decide for themselves the question of the age of the 

 red sandrock, and that, too, from original sources. 



Professor Emmons holds that the red sandstones of this age rest unconformably upon 

 the slates beneath, throughout the State, and regards this as a strong argument in favor 

 of his views. Even if the premises were granted we do not think his conclusions would 

 follow. 



We add in this place a few rough notes we made in 1859, concerning the relations of 

 these grits and slates. We do not feel disposed to endorse them now, but quote them as 

 an exposition of theories which have been held regarding these rocks, and are not yet 

 proved to be false. 



