1198 NEW YORK STATE MUSEUM 



Oriskany beds 



The Oriskany of this vicinity presents two distinct kinds of 

 deposits. The lower portion is a pebble bed or conglomerate 

 6 to 18 feet thick; the upper portion, 20 to 50 feet in thickness, 

 consists of layers of sandy limestones intercalated with bands 

 of cherty limestone, both of which are replete with fossils. 



The difference between the typical Port Ewen and the pebbly 

 Oriskany is very great though the change from the one formation 

 to the other was not violent, as indicated by the following de- 

 tailed section measured on the West Shore Railroad cut about 

 % mile south of the Wilbur bridge. The beds are numbered in 

 ascending order. 



Feet Inches 



14-21 Typical Port Ewen nodular limestone.... 66 2 



22 Band of black chert 1 6 



23 Impure limestone with much chert in thin 



bands ; no fossils 4 9 



24 Black, banded chert with thin limy bands. 

 The limestone bands contain a small amount of 



quartz sand 5 



25a Layer of quartz pebbles of size of peas ..... 3 



25b Black chert 9 



26 Alternating thin bands of pebbles and chert. . 3 7 



27 White pebble bed >. 5 



A solid bed of well rounded, water worn, white 



quartz pebbles, of size varying from peas to 

 white beans, stained with brown iron oxid, ce- 

 mented by limestone in some parts, elsewhere 

 no cement and pebbles loose. Fossils consist- 

 ing of waterworn fragments of the larger Oris- 

 kany brachiopods and gastropods. 

 28 Black pebble bed 9 



This is a solid bed of white rounded quartz pebbles of about 

 the same size as those of bed 27, but in places attaining even 

 1 inch in diameter. These are embedded in a tough hard matrix 

 of dark siliceous mud cement, that often assumes the character 

 of black chert. Among the quartz pebbles are often pebbles of 

 black chert like that of beds 22, 24, 25b; and a few masses of 



