Formations in eastern Central New York. 207 



from below upward, going west, and there can be no doubt as 

 to the continuity of sedimentation throughout. South of 

 Cortland the red materials are entirely absent and the entire 

 section is typical Portage. 



The fossiliferous Chemung shales overlying the Oneonta 

 formation south of Franklin have a thickness of about 300 

 feet and present the usual Chemung character. They grade up- 

 ward through a series of flags, into hard, coarse, cross- bedded 

 gray sandstones with intercalated red shale layers. In tracing 

 these fossiliferous shales eastward they were found to gradually 

 merge into flags and then into harder, coarse sandstones until 

 at Croton, ten miles east, their horizon is represented by a 

 heavy mass of coarse, gray, cross-bedded sandstones with 

 flaggy layers. This mass becomes harder and coarser eastward 

 and was traced to and along the eastern front of the Catskill 

 Mountains, its base defining the upper limit of the Oneonta 

 formation. Its thickness averages about 250 feet It is over- 

 lain by a red shale bed twenty-five to thirty feet in thickness 

 and this in turn is overlain by the thick mass of hard gray 

 sandstone on which the old Mountain House is built. At a 

 point about four miles due west of Durham some molluscan 

 remains were found in a softer gray bed about 175 feet above 

 the summit of the Oneonta formation. One fairly distinct 

 individual was recognized by Dr. Hall as Spirifer disju?icta, a 

 Chemung form. 



From Franklin, westward, the Oneonta-Chemung boundary 

 is clearly marked by the abrupt change from red beds to gray 

 shales and soft sandstones. It extends along the slopes south 

 of Unadilla and Sidney down the Susquehanna to a couple of 

 miles below Afton. Thence south to Guilford and Summit 

 on the New York, Ontario and Western Railroad and down 

 the Chenango to Greene. The exposures along the railroad 

 opposite Oxford from Lyons Creek bridge, where the Hamil- 

 ton is exposed, to the Chemung at Summit, were described by 

 C. E. Beecher, J. "W. Hall and C. E. Hall as a typical section 

 exhibiting the stratigraphic position of the Oneonta forma- 

 tion.* 



I have not traced the formations farther southward than 

 Palenville along the eastern front of the Catskills but there 

 can be no doubt as to their extension across the Delaware and far 

 into Pennsylvania. The "Chemung" rocks to which Mather 

 and others refer, lies below the Oneonta beds or about 1,000 feet 

 below the actual base of the Chemung horizon, and are Hamilton 

 in position. Their fauna is meager and consists of species sup- 

 posed by Vanuxem to be " Chemung " in central New York, 



*Xote on the Oneonta Sandstone in the vicinity of Oxford, Chenango County, 

 5th Report of State Geologist of New York, for 1885, p. 11. 



