174 



Report of the State Geologist. 



4. Spirifer Tuttius, Hall (?). (c) 



Form of this species, but not well enough preserved to show the 

 fine striae. 



5. Leptodesma Rogersi, Hall. (rr) 



XX Less than five feet above the top of the first fall are blue 



shales alternating with thin sandstones which form the rocky sides of the 

 narrow gorge. These rocks have the typical lithologic characters of the 

 Sherburne, and from their stratigraphic position undoubtedly belong at the 

 base of that formation. This is one of the best localities found in the Una- 

 dilla valley for the purpose of illustrating the transition from the Hamilton 

 to the Sherburne formation. It indicates that the conditions under which the 

 Tully limestone and Genesee slate were formed had nearly ceased and that 

 the lithologic characters of tho^e formations are scarcely represented in the 

 Unadilla valley. Vanuxem mentioned the occurrence of the Genesee slate at 

 North New Berlin (now New Berlin) \ but it was probably some of the rather 

 darker shales of the Sherburne which lie considered the Genesee, and, in fact, 

 under his description of the formation it is stated that " The Genesee slate was 

 not distinctly recognized east of the town of Smyrna in Chenango county." 2 



Fossils are very rare in these shales, only two fragments of a Goniatites 

 and another of a different shell being found. In this glen the top of the 

 Hamilton, according to barometric readings, is approximately 140 feet lower 

 than it is at XX A 3 , in West brook, New Berlin village, scarcely two miles 

 farther north, which would give, approximately, a dip to the south of seventy 

 feet per mile. Although this dip is considerably greater than former esti- 

 mates, still it agrees closely with the estimates in the earlier part of this 

 report for the exposures ten miles farther west along the Chenango valley. 

 The base of the Marcellus shale is north of Bridgewater in the upper part of 

 the Unadilla valley, twenty miles north of XX B, and, providing the dip is 

 as great for the entire distance as in the vicinity of New Berlin, we would 

 have a thickness along the Unadilla valley of over 1,300 feet for the Marcellns 

 ami Hamilton formations. The lithologic characters and fauna of the Hamil- 

 ton and Marcellus formations as shown along the Unadilla river valley from 

 New Berlin t<> Bridgewater have been described in a former paper. 3 About 

 one mile south of XX B is a smaller brook which exposes shales and thin 

 sandstones of tin- Sherburne formation. 



1 Geology of New York, Part III., p. 292. 

 •> I/Ad., p. 169. 



3 Prosser: The Devonian section of centra! New York along the Unadilla river. Twelfth Annual Report State Geologist 

 [New York], 1893, pp. 110-142. 



