IU(58 NEW YORK STATE MUSEUM 



8 ORISKANY BEDS 



These are silicious limestones, often with an abundance of 

 chert, the fossils being mostly silicified and weathering out 

 readily. Says Clarke : 1 



These strata, highly silicious, hard, dark limestones, have been 

 most favorably exposed to decomposition, and in consequence 

 the calcareous matter. has been largely leached out for a con- 

 siderable depth on all exposed surfaces, only a porous residuum 

 remaining. This light, rusty and firm rotten stone retains the 

 external and internal casts [molds] of the fossil remains with 

 which it is filled, in exquisite detail and forms excellent material 

 for study. Only by hastening nature's process with acid can the 

 fossils be made out from the black and cherty or unchanged 

 calcareous cores of this rock. 



The fauna of this formation was fully described and illustrated 



by Clarke. He summarizes it as follows : 2 



Of the 94 clearly defined species of this fauna, 38 represent ex- 

 pressions of species which began their existence in Helderbergian 

 times; on the other hand, but 18 of the species of the fauna con- 

 tinued their existence, or appear to be represented by closely 

 allied forms beyond the close of the Oriskany sedimentation. 

 29 are represented in the earlier known fauna of the arenaceous 

 beds of the Oriskany. 



The only satisfactory exposures of the Oriskany bed in situ are, 

 first, on the middle mountain road (Newman road) along the 

 western side of the road between the quarries of Becraft lime- 

 stone on the north and the stream which crosses the road near the 

 contact of the Oriskany and Esopus on the south ; and second, in 

 the field to the east of this, where the beds are brought up in little 

 folds. The best collecting grounds for the weathered out fossils 

 are in this same field, north of the flat bottomed meadow ground, 

 and in the fields west of the swampy area which marks the Oris- 

 kany-Esopus contact on the western side of the mountain. One 

 of the most accessible localities is at the crossing of the 

 middle transverse mountain road over this stream. Weathered 

 out Oriskany fossils are also found at the northern outcrop of the 

 Oriskany on syncline no. 2 and occasionally along the stream 

 following the Oriskany outcrop between faults 15 and 17. The 



1 Oriskany Fauna of Becraft Mountain, p. 12, 13. 



2 hoc. cit. p. 71. 



