4 



NEW YORK STATE MUSEUM 



SUCCESSION OF STRATA 



The following formations are represented on the map: 



Chautauquan | Cheimm S sandstone and shale 

 ' Prattsbnrg shale 

 ''High Point sandstone 

 West Hill flags and shale 

 Grimes sandstone 

 Hatch shale and flags 

 Senecan -i Rhinestreet black shale 

 Parrish limestone, in the 

 Cashaqua shale 

 West River shale 

 Genundewa limestone 

 I Genesee shale 



Neodevonic 



Genesee shale 



The lowest formation exposed within the limits of the northern 

 or Watkins quadrangle is the Genesee black slate which outcrops 

 slightly at the water's edge 443 feet A. T., in a low arch on the west 

 side of Seneca lake south of Fir Tree point and 6 miles from the 

 head of the lake. Here are about 6 feet of black slaty shale above 

 the water level but this is partially covered by the cliff talus. Toward 

 the west this formation increases in thickness and is well exposed in 

 the ravines along Seneca lake at the north and also along the shores 

 of Canandaigua lake. In the Genesee valley it is 90 feet thick but 

 from there westward it decreases rapidly and on the shore of Lake 

 Erie at the mouth of Pike creek it is but 12 inches in thickness. 

 Eastward from this meridian it decreases in thickness and the forma- 

 tion of which it is a member is not recognized beyond Smyrna, Che- 

 nango co. The rock is nearly all densely black bituminous shale, 

 some layers of which are slightly argillaceous or calcareous and 

 lighter colored. Calcareous concretions occur at intervals, usually in 

 the lighter beds. 



Fossils are very rare and none were observed in these outcrops. 

 Elsewhere the following species are found to be highly characteristic : 

 Liorhynchus quadricostatus, O r b i c u 1 o i d e a 1 o- 

 densis, O. minuta, Lingula spat u lata. 



