38 NEW YORK STATE MUSEUM 



both series the pebbles and conglomeratic streaks are scattered and 

 irregular, while the sands are often cross-bedded. Thin layers of 

 red shale occur, and locally gray sandstones." The deposits prob- 

 ably represent flood plains, deltas, and alluvial fans accumulated 

 mostly above sea level. 



(7) Oneonta sandstone (Upper flagstone). '' Thin and thick 

 bedded sandstones from 20 to 200 feet thick with interbedded red 

 shales up to 30 feet thick." Chiefly light gray to brown in color. 

 Abundant cross-bedding, occasional dark shale, frequent flagstone 

 beds. Capable of furnishing " bluestone " flags and more massive 

 dimension stone. To be seen in the vicinity of West Shokan and 

 westward. 



(8) Ithaca and Sherburne (lower flagstone " bluestone "). " Thin 

 bedded sandstone, with intercalated beds of dark shale. The sand- 

 stones are in masses from a few inches to 40 feet in thickness, 

 greenish gray to light bluish gray or dark gray in color, and are 

 extensively quarried as flagstones." There are occasional conglom- 

 eratic streaks. Occurs in large development in the vicinity of the 

 Ashokan reservoir (500 feet). The heavier cross-bedded and 

 coarser grained beds are capable of furnishing an unusually good 

 quality of large dimension stone for heavy structural uses. The 

 beds of this formation near Olive Bridge will in all probability 

 furnish the greater proportion of stone of all kinds for the con- 

 struction of the great Ashokan dam [see discussion of bluestone 

 near Ashokan dam, pt 2]. The chief common fossil content is 

 impressions of plant remains. 



(9) Hamilton and Marcellu's shales. " Dark gray to black or 

 brown shales with thin arenaceous beds in the upper part." Forms 

 the upper portion of the escarpment that follows the outer margin 

 of the Catskill foothills bordering the westerly side of the middle 

 Rondout and lower Esopus valleys. Occasionally beds are sub- 

 stantial enough for flagstone production (700 feet or more with the 

 Marcellus.) 



The chief index fossils are : Spirifer mucronatus, 

 Athyris s p i r i f e r b i d e s , Chonetes coronatus. 



The Marcellus shale is not readily differentiated in the Esopus 

 valley. Characteristically it is a thin bedded shale of no great 

 thickness (180 feet in the Schoharie valley) lying between the 

 Onondaga limestone and the Hamilton and obscured by talus from 

 the escarpment (with the Hamilton 700 feet.) 



Styliolina fissurella, Chonetes mucronatus, 

 Strophalosia truncata, Liorhynchus mysia. 



