8.s6 



PRINCIPLES OF STRATIGRAPHY 



A nearly continuous cuesta in face may be traced along the south 

 shore of Lake Ontario from Rochester to Niagara, and thence 

 northwestward through Canada, the Indian Peninsula between 

 Georgian Bay and Lake Huron, and across the Manitoulin Islands. 

 Turning westward on these islands, it passes through the Northern 

 Peninsula of Michigan, and then turns southward, forming the 

 peninsula between Lake Michigan and Green Bay, beyond which it 

 continues southward through eastern Wisconsin. 



Fig. 209. Map showing the probable drainage and topography in eastern 

 North America during Tertiary time, when a revived cuesta- 

 topography was produced. 



The cuesta is cut out of the Lower Siluric formations which 

 here consist of the capping hard Niagaran (Lockport) limestones 

 and dolomites, underlain by softer shales and sandstones, into which 

 the inner lowland has been cut. In New York the softer strata 

 are thickest while the overlying hard beds thin eastward. Here the 

 inner lowland is very deep, approaching in places a thousand feet 

 below the top of the cuesta. Most of it is submerged by the waters 

 of Lake Ontario. Eastward from Rochester the cuesta becomes 

 less defined, owing to the failure of the hard capping stratum, and 

 it finally unites with the next higher cuesta to the south, to form 



