THE NIAGARAN FORMATIONS OF WESTERN OHIO 347 



typical Medina formation shades through lateral alteration into 

 the typical Cataract." 1 



This apparently agrees with the idea expressed by Professor R. 

 Zuber, of the University of Lemberg, on the escarpment at Hamil- 

 ton, Ontario, in August, 1913, when he said that the Medina and 

 Cataract appeared to him to be different facies of the same forma- 

 tion. Concerning the relation to the Brassfield, Professor Schuchert 

 wrote : 



The Cataract may also be compared with the Brassfield formation of Ohio 

 and Indiana, as the two are clearly related, and also both are of a limestone 

 facies. The former has 76 species and the latter 140. Between the two there 



are 24 forms in common When the two biotas are finally carefully 



compared with each other, there will undoubtedly be added more significant 

 forms strengthening the view that the Cataract and Brassfield are fairly close 

 correlates in time. However, as these two faunas are not of the same epicon- 

 tinental basin, one cannot expect a large percentage of the forms to be common 

 to both; the Brassfield element came in from the Gulf of Mexico region, while 

 the Cataract migrated into Ontario through the Gulf of St. Lawrence embay- 

 ment across the Province of Quebec or came in from the Arctic. 2 



A little later Dr. M. Y. Williams, in his article on the "Stra- 

 tigraphy of the Niagara Escarpment of Southwestern Ontario," 

 has stated that "Medina is used in the sense in which Grabau 

 has redefined the term, that is, to include the beds above the 

 Queenstown shale and below the Clinton formation. It is extended, 

 however, laterally to include the Cataract formation as defined by 

 Schuchert." 3 



The Medina sandstone underlies the Clinton beds of New York 

 and is not included in the Niagaran series, but is the upper forma- 

 tion of the Oswegan series as classified by the New York Geological 

 Survey. Therefore, if the correlation reviewed above be accepted, 

 then the Brassfield limestone (formerly called Clinton) of Kentucky, 

 Ohio, and Indiana is to be transferred from the Niagaran to the 

 Oswegan series of the Silurian system. 



Furthermore, Professor T. E. Savage believes that in the Mis- 

 sissippi Valley the Sexton Creek limestone "represents about the 



1 Ibid., p. 294. 2 Ibid., p. 291. 



3 Summary Report of the Geological Survey [Canada] for the Calendar Year 1913 

 (1914), p. 182. 



