THE OTTAWA NATUR 



Vol. XXVII JUNE-JULY, 1913 Nos. 3-4 



REVISION OF THE SILURIAN OF SOUTH-WESTERN 



ONTARIO. 



Bv M. G. Williams.* 



At the l c >12 meeting of the Paleontological Society of 

 America, Professor Charles Schuchert read a paper entitled 

 "The Cataract, a New Formation at the Base of the Silurian 

 in Ontario and New York." During the summer of 1912 the 

 writer was engaged by the Geological Survey of Carada in 

 revising the Silurian of Manitoulin Island and Georgian Bay, 

 and was with Professor Schuchert during his field observations 

 in these regions. A preliminary statement of the results of the 

 work will appear in the Summary Report of the Geological 

 Survey of Canada for 1912. In the meantime, it may be stated 

 that the "Cataract" formation in the Georgian Bay region 

 consists of two very distinct divisions a lower dolomite member 

 11 or 12 feet thick near Collingwood, and 50 feet or more in 

 thickness on parts of Manitoulin Island: and an upper shale 

 member of varying thickness. 



For the dolomite division of the Cataract formation the 

 name "Manitoulin member" is proposed, because of its import- 

 ance on Manitoulin Island. Here it rests upon soft green shale 

 at the top of the Richmond formation. At Cabot Head 6 feet 

 or more of soft, red shale intervene between the green Richmond 

 shale and the base of the Manitoulin dolomite. 



The red clay-shale, which forms the upper division of the 

 formation on Manitoulin Island, is well exposed along the road 

 between the villages of Kagawong and West Bay. at a locality 

 north-east of Kagawong Lake. For this division, the name 

 "Kagawong member" is proposed. In the Manitoulin region 

 the Kagawong shale is overlain by about 6 feet of green shale 

 about 6 feet thick which appears to grade upward into the 

 argillaceous dolomite of the Lockport formation. At Cabot 

 Head probably 16 feet of firm red shales underlie soft red clay- 

 shale similar to that on Manitoulin Island. Firm red shale, 



^Published by permission of the Director of the Geological Survey of 

 Canada. 



