48 



NEW YORK STATE MUSEUM 



The following is the succession in descending order and the 

 formations are considered in order from bottom to top. 



Chautauquan 



" Upper ' 



Lower 



Chemung sandstones 

 and shales 



Neodevonic < 



Senecan < 



Wiscoy shale 



Nunda sandstone 

 Gardeau flags and shale 

 Grimes sandstone 

 Hatch flags and shale 

 Rhinestreet black shale 

 Cashaqua shale 

 Middlesex black shale 

 West River black shale 

 Genundewa limestone 

 L Genesee black shale 



425' 



400^ 

 190^ 

 2151 

 344' 



204^ 



125' 



81 



5' 



The aggregate thickness of the beds here described is 2142 feet. 

 The difference in altitude between the Genesee river bed at the 

 north line of the Nunda quadrangle and the highest point near the 

 southwest corner of the Portage quadrangle is 1565 feet and 578 

 feet additional are brought up by the elevation of the strata toward 

 the north and east. 



Genesee shale 



The lowest rock exposure on this area is the Genesee black shale. 



Historical. This formation was first described in the 3d Annual 

 Report by Hall, 1839, page 301, under the title " Upper black shale," 

 beginning, " Reposing upon the Tully limestone we have a thickness 

 of 150 feet of shale exhibiting throughout a uniform color, and 

 slaty structure " etc. 



The black shale is mentioned several times in this report, as 

 occurring in Seneca, Yates and Ontario counties, but no more 

 specific name is applied to it. It is also referred to in the 4th 

 Annual Report. 



In the final report of 1843, page 218, the name Genesee slate is 

 substituted for Upper black shale, and the opening of the gorge of 

 the Genesee river at Mount Morris is said to be the place of its 

 greatest development in the district. 



