206 i\ T . II. Darton — Oneonta and Chemung 



ized by a greater proportion of red shales than are contained 

 in the great overlying series eastward, but both are closely 

 related in their general history. The Oneonta beds preserve 

 their character for a few miles farther west than do the basal 

 members of the overlying series, but finally merge into typical 

 Portage. 



The Hamilton group (Marcellus to Hamilton) also change in 

 character eastward similarly becoming coarse-grained and 

 finally flaggy nearly to its base. 



The outcrop area of the typical Oneonta formation is a wide 

 belt extending through eastern Chenango, southern Otsego, 

 northern Delaware, southern Schoharie and eastern Greene 

 counties. Its greatest width is on the latitude of Otsego 

 where the belt is about fifteen miles wide. In Delaware 

 county it averages from six to ten miles wide and its beds are 

 everywhere finely exposed. On Schoharie Creek it begins at 

 the Manorkill Falls and extends about twelve miles southward. 

 It extends far north about the headwaters of the Catsldll and 

 then southeastward in a narrowed belt along the steep slope of 

 the high northern and eastern front of the Catskills by Cairo 

 and through Palenville. 



Stratigraphy. — The stratigraphic components of the Oneonta 

 formation are somewhat variable in its smaller subdivisions 

 but certain members preserve general characteristics through- 

 out. The basal beds are gray flags which merge into the 

 Hamilton. Their thickness averages about fifty feet and they 

 may be regarded in greater part as beds of passage. They are 

 streaked with red shale above and give place to a thick mass 

 of red shales with more or less intercalated gray or greenish 

 flags. Next above is a series of gray sandstones and flags with 

 occasional red shale streaks in some localities, and usually some 

 red sandstone layers. This series averages between two hun- 

 dred and two hundred and fifty feet in thickness. The upper 

 member of the formation consists of six or seven hundred feet 

 of red shales and sandstones with intercalated gray and green- 

 ish flaggy beds and some cross-bedded sandstones eastward. 

 The red shales are bright red in color and moderately hard in 

 texture. They are not in regular continuous beds throughout 

 but constitute greatly elongated lenses in the gray flags and 

 red sandstones. 



Toward the western termination of the Oneonta formation 

 these members lose their distinctness and finally give place to 

 the gray beds of the Portage. The formation also gradually 

 decreases in thickness and width and on the Chenango there 

 are not over 500 feet of red beds. West of Norwich the red 

 materials disappear rapidly and their place is taken by gray 

 shales and thin bedded sandstone. This change in character is 



