N. II. Darton — Oneonta and Chemung Formations, etc. 203 



Art. XXV. — The stratigraphic relations of the Oneonta and 

 Chemung formations in eastern Central New York • by 

 1ST. H. Darton, U. S. Geological Survey. 



Introductory . — This paper is a condensed account of a recent 

 investigation in upper Devonian stratigraphy, made for the 

 State of New York for the new geological map. Dr. James 

 Hall made some statements regarding the general bearing of 

 the results at the Rochester meeting of the Geological Survey 

 of America, and a detailed report with map will finally be 

 published in the report of the State Geologist of New York. 



The principal purpose of the investigation was to determine 

 the relations and distribution of the Oneonta and Chemung 

 formations in their extension from Delaware county through 

 the Catskill Mountains, but some study was also given to their 

 relations in Chemung and Broome counties. 



In its typical development in Otsego county, the Oneonta 

 formation comprises a thick mass of red shales and red and 

 gray sandstones similar in character to the rocks of the Catskill 

 Mountains and overlying the Chemung formation in southern 

 New York and northern Pennsylvania. The formation was 

 given its name by Yanuxem who supposed that it was equiva- 

 lent to the Catskill formation and above the Chemung forma- 

 tion. The organic remains in the Oneonta beds were few and 

 consist of plant remains common to the Catskill rocks and a 

 fresh or brackish water form now known as Amphigenia. 

 Later studies by James Hall and others led to the discovery of 

 an overlying series of shales and sandstones containing Che- 

 mung fossils at several localities southwest of Oneonta, and it 

 was found that the fauna of the underlying beds was Hamil- 

 ton in age. These discoveries indicated that the Oneonta for- 

 mation represented approximately the eastern extension of the 

 Portage formation, considerably modified in character but well 

 defined in stratigraphic position. Nothing however was deter- 

 mined as to the eastward extension of the Oneonta beds and 

 overlying Chemung along the northern and eastern side of the 

 • Catskill Mountains and Mather's statements in his report were 

 too vague to throw light on the problem. The great mass of 

 gray sandstone with red shales constituting the Catskill Moun- 

 tains were designated Catskill by Mather and the mass was 

 supposed to be underlain in eastern New York by an obscure, 

 attenuated representative of the Chemung and under which 

 in turn were recognized the " Portage " and the Hamilton 

 formations. 



Am. Jour. Soi. — Third Series, Vol. XLV, No. 267. — March, 18J)3. 

 15 



