ROCHESTER AND ONTARIO BEACH QUADRANGLES 2 1 



stated, however, that the closing stages of the dolomite period in 

 western New York were extremely complex, and we are not in a 

 position to say positively that everywhere in New York State the 

 upper Guelph fauna terminates this series. 



In the excavations made at Dufferin islands at Niagara Falls, the 

 section which was temporarily exposed showed a fauna that 

 included both Lockport and Guelph species. As this horizon is 

 above the crest of the falls, it represents a higher horizon than 

 the upper Guelph, as determined along the Niagara gorge and at 

 Shelby. Above this exposure at the falls there are at least 40 feet 

 before the Salina series appears. In the type section for the Guelph 

 in Canada, it is considered as following the Lockport and is there 

 regarded both as a faunistic and lithologic element in the succession 

 of Siluric rocks. 



Of the two Guelph beds at Shelby, it is of importance to note 

 that the fauna of the lower is of the purer Guelph type, while 

 in the upper the presence of Lockport species is much more 

 pronounced. 



The 32 feet of dolomites separating these two faunas are quite free 

 from Guelph fossils, the species found being all of the Lockport 

 type. At Rochester it is the upper Guelph fauna that appears in 

 greatest force and its admixture and complication with the Lockport 

 fauna is very noticeable. 



In regard to the Lockport and Guelph faunas, it should be stated 

 that the former represents the normal or indigene fauna, which is 

 the immediate successor of, and derivative from the Rochester shale 

 fauna. The Guelph fauna on the other hand is not to be considered 

 as derived from the Lockport and Rochester shale faunas as pre- 

 sented in the strata which immediately precede the first appearance 

 of the Guelph fauna. It is, therefore, in the New York province to 

 be regarded as an alien fauna which invaded this section of the 

 State from the west and temporarily displaced the normal or Lock- 

 port fauna. The peculiar conditions which brought about the intro- 

 duction of the Guelph fauna into the Lockport sediments will be 

 stated later. 



On the map the lower portion of the Lockport dolomites which 

 is free from the Guelph species we have designated simply as Lock 

 port dolomites and the upper portion as Lockport dolomite with 

 interbedded Guelph faunas. 



