192 ■ NEW YORK STATE MUSEUM 



and Esopus is everywhere marked by low, swampy ground and by 

 the existence of stream beds."^ 



Esopus 



The Esopus is a dark gray silicious shale. It has an approximate 

 maximum thickness of 550 feet. The very strong cleavage which 

 has been induced in it has given rise to very thin, platelike pieces. 

 The entire Esopus is a continuous succession of hogbacks, giving 

 an appearance very similar to a series of step faults. Yet this ap- 

 pearance may be due merely to differential weathering on account 

 of the greater development of certain cleavages over others. This 

 latter theory is partially borne out by the fact that the valleys 

 between the hogbacks run parallel to the strike of the beds. 



No fossils were found in the Esopus though prolonged search 

 was made for them. Irregular pyrite nodules are very abundant in 

 all parts of the Esopus and Lower Ononda^. For 50 or more feet 

 up into the Onondaga, probably a fourth of the many fossils found 

 are pyritized. This suggests that perhaps each of the Esopus 

 nodules also represents what is left of one or more fossils after the 

 wonderful cleavage to which it has been subjected. 



The Schoharie grit is here included in the Esopus on account of 

 the absence of fossils and the lithic similarity of the two formations. 



Onondaga 



The transition from the Esopus to the Onondaga is very gradual. 

 The lowest, much cleaved beds are arenaceous shales and except 

 for the fossils would be placed in the Esopus. The beds become 

 more calcareous till 30 feet above the base, a typical calcareous 

 shale is developed. Here the fossils are quite numerous though 

 few in species. The most abundant species are Coelospira 

 acutiplicata and C. g r a b a u i . The strata continue 

 principally as calcareous shales for over a hundred feet but with 

 the occurrence of thin bands of limestone more and more frequently 

 toward the top. For the next 40 or 50 feet the limestone and cal- 

 careous shale beds are about equal in number and thickness. Here 



^Grabau, A. W. Stratigraphy of Becraft Mountain, Columbia County, N. Y. 

 N. Y. State Paleontol. An. Rep't. 1902. p. 1069. 



