1892.J PROSSER THE GENESEE SECTION. 



93 



down. to the Archean (?), With two exceptions the thickness of each 

 formation is obtained from some well record and the wells which have 

 furnished most of the data for this general section are the Clarks- 

 ville, Castile, Rock Glen, Batavia and Rochester. 



A General Geological Section of Western New York, not 

 FAR west of the Genesee River. 



DEPTH. ^NESs!" FORMATION. 



o' Little Genesee conglomerate = 



Olean conglomerate (?). 

 300' Upper Devonian (estimated). 



Wolf creek conglomerate. 

 1150'-!- Chemung. (') 



Portage (estimated in part). (-') 



Genesee shale. {") 



Hamilton. 



Marcellus shale. 



Upper Helderberg 

 150' and 



? Lower Helderberg. (') 



(I.) It is probable that the Clarksville well, No. gi, does not reach the bottom of the Chemung 

 and in that case 1150' is not the entire thickness of this stage. 



(2.) From a comparison of the well sections there was about 825' of Portage in the Castile well. 

 But that well did not commence at the top of the Portage, so that it is better to call this stage at least 

 900' in thickness and it may be considerably thicker. 



(3.) The first black shale seen may not be the top of the Genesee, but some of the black bands 

 in the lower part of the Portage, in which case 100' is probably greater than the true thickness of the 

 Genesee shale. 



(4.) There is from i4o'-i5o' of rock that lithologically it is not possible to separate from the 

 Upper Helderberg ; but it is possible that part of this limestone ought to be referred to the Onondaga Salt 

 group. Mr. Harris noted the same difficulty in the Jamestown well (Am. Geol. Vol. VII, p. 170). 



(5.) The wells throughout the salt district indicate a thickness of from 500' to a little more than 

 600' for the Onondaga Salt group. 



