NATURAL HISTORY, TORONTO REGION 



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The Silurian (Upper Silurian) of southwestern 

 Ontario includes a number of fairly distinct subdivi- 

 sions which have been classed in various ways, the 

 Niagara Limestone standing out most prominently at 

 the crest of the escarpment before mentioned. 



Professor Parks gives the following classification 

 of the Silurian : 



Salina .... Impure limestone and shale with gyp- 

 sum and rock salt. 

 Guelph .... Dolomite. 



Lockport Dolomitic limestone. 



Eochester-Shale. 

 Clinton .... Limestone and shale. 

 Medina .... Sandstone and shale. 

 Cataract . . . Sandstone, etc. 



All of these subdivisions except the Guelph and 

 Salina are well exposed in the Niagara gorge, the 

 Cataract red or grey sandstone and shale resting 

 upon the red Queenston shale at the mouth of the 

 gorge. As one follows up the gorge the Cataract 

 beds disappear beneath the rapids, and afterwards 

 the Medina is lost, so that at the falls the lowest rock 

 visible is the Clinton limestone. 



The Niagara (Lockport) limestone is thin at 

 Queenston Heights, at the mouth of the gorge, but 

 grows thicker as one approaches the falls, owing to 

 the gentle southward dip of the beds. 



Dr. Parks mentions the following fossils as com- 

 mon in the Niagara and lower formations of the 

 Silurian. 





