14 



NEW YORK STATE MUSEUM 



cops cristata var. p i p a ; the cephalopods, Cyrto- 

 ceras undulatum and Gyroceras trivolve, and 

 the brachiopods, Atrypa reticularis, Leptaena 

 r h o m b o i d a 1 i s , S t r o p h e o d o n t a concava, S. 

 inaequistriata, Spirifer acuminatus and S . 

 divaricatus and others. 



Marcellus beds 



Marcellus black shale 



The term Marcellus shale has been generally applied in New 

 York geology to the series of black and dark blue shales which lie 

 immediately on the Onondaga limestone and at the top pass gradu- 

 ally into the lighter colored Hamilton shales. At Marcellus, Onon- 

 daga co., from which place the name is derived, only the lower 

 layers are well exposed and observations in that region and in the 

 western part of the State indicate the desirability of restricting 

 the term to the lower shales, exposed at the type locality, thereby 

 obtaining a more exact basis for correlation. 1 



From Ontario county westward the thin Marcellus black shale 

 is delimited upward by the Stafford limestone. The rock is a 

 densely black and highly bituminous slaty shale with a few thin 

 calcareous layers and rows of spherical concretions. 



Neither the lower nor upper contacts with the limestones are 

 exposed on this quadrangle, and the shales nowhere come to the 

 surface. The thickness of the formation can therefore only be 

 estimated or obtained from well records. 



The beds are 41 feet thick in the Livonia salt shaft and con- 

 tain a 5 foot stratum of soft limestone, 27 feet below the top. 

 The most western exposure of the Marcellus shale is in the bed of 

 Plumbottom creek at Lancaster, 6 miles east of the east line of this 

 quadrangle. A layer of limestone 1 foot thick forming there the 

 bottom of the outcrop and separated by 18 to 20 feet of black 

 shale from the Stafford limestone probably represents the five 

 foot stratum of the Livonia salt shaft. Since the contact with the 

 Onondaga limestone is not exposed at this locality it fails to fur- 

 nish information on the entire thickness of the Marcellus shale. 

 This has been obtained in the well on Smoke's creek, previously 

 mentioned, where a total thickness of 55 feet has been measured. 



The fauna of the black shales is small and fossils are rare except 



IN. Y. State Mus. Bui. 63. p. 14. 



