Geology af St. Helens Island. 57 



who has made a careful study of the fauna which they con- 

 tain, and through his courtesy we are enabled to state the 

 age of the two limestones. The larger area is of Lower 

 Oriskany age (early Devonian), as expressed in Western 

 Ontario and Virginia, while the smaller area is Lower 

 Helderberg (Upper Silurian), and corresponds to the 

 Upper Pentamerus zone of Eastern New York. 



It is of peculiar interest to find remnants of these two 

 formations in the present locality, inasmuch, as they 

 have not been found in situ elsewhere in Western Quebec. 

 The occurrences indicate an extension of the Upper 

 Silurian and early Devonian seas as far north as Montreal. 



An east and west section (A B figure 3) across the 

 Lower Oriskany inclusion and the breccia, shows the 

 relations of the two, and from this it is apparent that at 

 an earlier period the former was wholly enclosed in 

 the latter. 



Figure 3 



*a J> t> A > 



Section across Limestone /nc/usions in Breccia 

 Breccia^ Oriskany Limestone S 



Scale Horizontal Vertical 25" 



Petrography of the Beeccia. For a more minute 

 examination, a typical specimen was chosen from the 

 breccia near the limestone, and a thin section was made 

 of the matrix. Macroscopically the matrix is fine grained, 

 grey in color, quite hard and dull, with an irregular 



