356 New York State Museum 



that when the Lower Devonian Oriskany sea flooded the 

 trough again and spread westward over this eroded sur- 

 face these sands were reworked by the waves and depos- 

 ited as the Oriskany sandstone, which is very fossilifer- 

 ous in places. In Pennsylvania it is a thick deposit of 

 very pure quartz-sand, but in some places it is no more 

 than a thin layer of quartz grains. At the end of Oris- 

 kany deposition the Cumberland area of the Appalachian 

 trough was elevated and in eastern New York we have 

 only the coarse sands and grits of a mud delta constitut- 

 ing the Esopus formation (Oriskanian). Submergence 

 became pronouncedly positive in late Lower Devonian 

 (late Oriskanian) time and continued to the maximum 

 flooding of the continent in late Middle Devonian (Ham- 

 ilton) time. 



The great submergence of the Middle Devonian in 

 North America had its counterpart in Europe, Asia, Aus- 

 tralia and South America, and was one of the greatest 

 floodings in geologic history, exceeded later only by the 

 great submergence of the Cretaceous. The interior sea 

 was again established and in it was accumulated the 

 Onondaga limestone which with its wealth of corals and 

 brachiopods indicates a warm, clear sea surrounded by 

 lowlands, and it must have been of long duration. The 

 warm waters brought many coral species and an abun- 

 dance of corals first from the North Atlantic and Gulf 

 of Mexico and later from the Arctic sea that advanced 

 southward. These corals built extensive reefs in the 

 limestone deposits, such as the famous occurrence at the 

 Falls of the Ohio, Louisville, Ky. The Onondaga lime- 

 stone stretches from the Hudson river across New York 

 to Michigan and it also extends into Indiana, Illinois and 

 Kentucky around what were perhaps islands of the Cin- 



