The Stratigraphic and Faunal Relations of the Oneonta 

 Sandstones and Shales, the Ithaca and the Portage 

 Groups in Central New York. 



By John M. Clarke. 



In the Thirteenth Annual Report of the State Geologist, dated 1894, 

 the writer communicated the preliminary results of observations made in 

 Chenango county, with especial reference to the westward extension through 

 that region of the barren sandstones, red and green shales constituting the 

 Oneonta beds, as denned by the late Lardner Vanuxem. Sufficient evidence 

 was there brought forward to show that westward of the Chenango river 

 this group of beds, so important economically for its high-grade sandstones 

 and so strikingly characterized by the brilliant coloration of many of its softer 

 beds, rapidly thins out. Even before reaching the western limit of Chenango 

 county the last positive evidence of it has disappeared. The Genegantslet 

 creek, a considerable water course rising in the high land of Pharsalia town- 

 ship and flowing almost due south into the Chenango river, gives a number 

 of instructive sections which olfer a clew to the mode of its disappearance. 

 The entire mass of this distinctly eastern sediment does not thin to a -single 

 edge. Between it and the contemporaneous sediments of the fossil-bearing 

 Ithaca group, which predominate in western Chenango county, there was a 

 constant oscillation and a mutual encroachment ; consequently the rock 

 sections show recurrences of Oneonta conditions after the main body of such 

 deposits had been left far below. Thus, in the village of Greene, on Bird- 

 sail's brook (Station M, Report of 1894), a section lying almost as low as the 

 river level in the Chenango valley, the characteristic Oneonta shales and 

 sands, with their reds and greens, are well shown. But northward along the 

 Genegantslet, flowing through high lands well elevated above this spot are 

 repeated evidences of such highly colored beds, separated from those beneath 

 by intervals of fossiliferous rocks. At Station N, two miles north of Greene 

 on the highway to Smith ville Flats, are fossiliferous shales, 150 to 200 feet 

 higher than the beds at Station M ; at Station O, two and one-half miles north 

 of Smith ville Flats and considerably higher in the section, are again green shales 

 and sands with fish remains, a repetition of the Oneonta sediments, together 

 with shaly layers bearing fossils. Still further north, a short distance south 



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