LOWER SILURIC SHALES OF THE MOHAWK VALLEY 47 



to Fort Hunter, at the mouth of the creek. About seven and one- 

 half miles south of Fort Hunter the contact of the Canajoharie 

 shale with the Schenectady is a very distinct one. The section at 

 this contact in a cliff on the western side of the creek, three miles 

 south of Mill Point, has been described by Prosser (1900, page 

 470), as follows: 



Feet 



45X 1 Clear black shale from the water to the base of 

 lowest sandstone stratum in the cliff, 114' by 

 level and 105' by barometer. At the sand- 

 stone stratum there is a decided lithologic 

 break from the black argillaceous shales be- 

 low. Utica shale 114=114 



X 2 Grayish sandstones alternating with bluish 

 argillaceous shales to the top of the cliff. 

 Hudson River formation 195 == 309 



X 3 Mostly covered from the top of the cliff to 



the highway 15 = 324 



X 4 Occasional ledges of sandstone show on the 

 side of the hill from the highway nearly to 

 its top. Hudson River formation 120 = 444 



From this point up the river a splendid series of exposures of 

 the Schenectady formation is furnished by the river banks. The 

 section from Burtonville (formerly Burton's bridge) to Esperance 

 has already been described in detail by Mather (title 2, page 379). 

 Hundreds of feet of rock are here exposed in magnificent cliffs ; on 

 investigation they prove, however, a monotonous alternation of sand- 

 stone or grit beds with shales with an extreme scarcity of fossils. 

 As far as fossils were observed (a few traces of Climacogr. 

 typicalis in the upper layers and Sphenophycus 1 a t i - 

 f olius in the lower shales), they show the great uniformity of 

 the fossil content throughout the entire series of beds here com- 

 prised as Schenectady shale. 



A third group of fossiliferous outcrops has been observed by 

 us five to ten miles south of Schenectady, directly in front of the 

 Helderbergs, along the Normanskill and its branches, the Bozen 

 kill and the Vly near the villages of Altamont, Guilderland and 

 Voorheesville. We have already described on page 41 the remark- 

 able alternation of sandstones and shales at the Bozen kill. Con- 

 tinuous outcrops ranging through 200 and 300 feet of rock are 

 found in the upper branches of this kill west of Altamont, which 

 form deep ravines in the lower slope of the Helderberg escarpment. 

 These beds consist prevailingly of bluish and greenish gray shales 

 with several intercalations of sandstone beds, the latter reaching 



