ORTHOCERAS IN THE ONEONTA BEDS OF CHENANGO VALLEY 167 



A REMARKABLE OCCURRENCE OF ORTHOCERAS IN THE 

 ONEONTA BEDS OF THE CHENANGO VALLEY, N. Y. 



BY JOHN M. CLARKE 



(Plates 1-4) 



At Oxford in the valley of the Chenango river in southern 

 central New York are the extensive bluestone quarries of the 

 F. G. Clarke Co. These quarries lie in the westward extension 

 of the formation termed by Vanuxem the Oneonta beds. I have 

 shown on previous occasions that these Oneonta beds represent 

 in the Chenango valley region a peculiarly local development of 

 the later deposits made during the period of time known as the 

 Portage age. They are underlaid by the lower beds of the Ithaca 

 stage, bearing an abundant marine fauna very closely allied 

 in specific traits to the fauna of the Hamilton shales beneath. 

 The Oneonta deposits were evidently laid down in a shallow or 

 receding sea or perhaps, speaking with more precision, in an 

 estuary while shut off from the open sea and freely receiving ter- 

 restrial drainage. The deposits contain no forms of life similar 

 to those of the upper beds of the Ithaca formation with which 

 they are apparently stratigraphically continuous and which 

 bound them on the west. Their strata consist for the most part 

 of schistose sands here and there interstratified with fine-grained 

 argillaceous shales carrying in places considerable calcareous 

 matter. The deposits are several hundred feet in thickness in 

 this section, and are often highly colored by the green and red 

 tints of iron oxids, in which respect they are not unlike some of 

 the sands of the Catskill formation. With our present knowl- 

 edge we interpret the Oneonta sedimentation as of similar origin 

 to that of the Catskill and the precursor or the introduction 

 of the latter in the meridian of the Chenango valley. Here the 

 Chemung beds^ carrying a marine fauna, extend over the Oneonta 

 sediments and separate them from the Catskill above, but, pass- 

 ing eastward into Delaware co., the Chemung strata finally dis- 



