310 C. SCHUCHERT — l6wER U KLDERBERG-ORISK AN Y FORMATIONS 



Along the Delaware river, this formation is very variable in its litholog- 

 ieal characters, follows directly upon the Helderbergian series, and is 

 overlain by a great mass of Esopus grit. 



Lesley* summarizes the work of the " Second Geological Survey of 

 Pennsylvania" on the Oriskany formation as follows: 



" In Pennsylvania the outcrops of Oriskany extend in straight and curved lines 

 and many zigzags through nineteen counties, a total distance of 1,100 miles ; the 

 formation, however, appearing and disappearing, thickening and thinning; vary- 

 ing in character from sandy shales to massive flint rock ; in some places crowded 

 with shells, at others almost destitute of them ; in some places calcareous, in others 

 with scarcely a trace of lime, in some places highly ferruginous, even containing 

 iron enough to furnish furnace ore." 



The maximum thickness in Pennsylvania is probably not over 200 

 feet. It has been given as 700 feet, but this depth apparently includes 

 either the Helderbergian or the Esopus grit. 



The Oriskany and Helderbergian series, as exposed in the Neversink 

 valley, enter New Jersey and Pennsylvania south westward from Port 

 Jervis, New York. The Oriskany of this region is described by I. C. 

 White,f as follows : 



" The rocks which make up the Oriskany series change so radically in character 

 in passing southwest from the eastern line of the district that there is scarcely any- 

 thing in common to the sections of the group at the eastern line of Pike and the 

 western line of Monroe. 



" The sandstone member of the series is entirely absent at the eastern extremity 

 of Pike county, the only representative of the Oriskany there present being a bed 

 of limy, cherty shales, weathering down into muddy looking beds holding Oriskany 

 fossils. They are in fact a mere continuation of the Lower Helderberg beds up to 

 the very base of the Cauda-galli grit." 



At Carpenters Point village, the Oriskany was estimated as 50 feet 

 thick. On crossing the Delaware river into Monroe count} 7 , the Oriskany 

 appears to thicken and at Broadhead creek is 45 feet thick, at the western 

 line of Monroe about 175 feet, and is fully 200 feet thick on the Lehigh 

 river below Bowman's. 



George H. Cook,J the state geologist of New Jerse} 7 , describes the 

 Oriskany of that state as follows: 



"Under this division [Oriskany sandstone] we have included the large mass of 

 rock lying between the Lower Helderberg and Cauda-galli. There is a thin bed 

 offender sandstone, or almost sand, full of indistinct marks of fossils, which may 

 be considered as the base of the formation. It is hardly eight feet thick, and may 



♦ Second G-eol. Survey Pa., Summary Final Report, vol. ii. 1892, }>]). 1036, 1037. 

 f9econd Geol. Survey Pa., vol. <;<;. 1882, pp. 122-126. 

 JGeol. of New Jersey, 1868, pp. 160, 161. 



