Peossee and Cuminus— Lower Silurian Sections. 



633 



Section Northeast of Little Falls. 



The following section begins at the river level below the falls in the 

 eastern part of Little Falls and continues northerly for about two miles, 

 nearly to the summit of the general elevation for that region. 



XL VII IP, The Laurentian rocks composed principally of 203=903 

 gneiss have a thickness of 203 feet as determined by tape and Locke level 

 measurements. The barometric readings gave 200 feet of the gneiss and 

 this part of the section may be divided as follows: From the river to the 

 New York Central railroad, forty feet of garnetiferous gneiss, the base of 

 which is well exposed along the river; vertical cliff of thirty-three feet of 

 similar gneiss, weathering to a reddish-brown, to level of Little Falls and 

 Dolgeville railroad; gneiss forming cliff above Little Falls and Dolgeville 

 railroad, including the conspicuous layers above the cut, sixty feet; gneiss in 

 the cedar grove where the joint openings are conspicuous, then mostly covered, 

 but exposed near the top just below Loorais street, seventy feet. All the 

 gneiss except the seventy feet of the upper part is well shown in Plate 

 VII, which is a near view, looking westward, of the gneiss along the 

 New York Central railroad in the eastern part of Little Falls. 



I>\ In the base of the Hiram Boyer quarry on Loomis street, just 3 ^= e |^ 

 above the gneiss, is a very coarse-grained, quartzitic sandstone containing 

 quite large quartz pebbles. At present the contact of this sandstone and 

 the gneiss is hardly shown, though Mi'. Boyer states that in the deeper part 

 of the quarry, former excavations showed it very distinctly. In general, the 

 gneiss apparently dips heavily to the northeast, while in the quarry the 

 sandstone has a dip of from one to one and one-half degrees to the north- 

 west. Professors Shaler and H. S. Williams studied this exposure some 

 years ago and, it is believed, determined that the sandstone rests uncon- 

 formably upon the gneiss.* Mr. Walcott stated that this sandstone "has 

 been referred to the Potsdam, "j- though he apparently did not accept this 

 correlation, for he said : "it is doubtful if we can claim the presence of the 

 Potsdam at any point in the Mohawk Valley." 



IP. Bluish-black, finely arenaceous shale, nine inches thick, H F =% 7 

 weathering to irregular pieces. It contains fairly well preserved specimens of 

 I/mgul&pi% acuminata, Con., which were first discovered by Professors 

 Shaler and H. S. Williams, and reported by the latter at the Washington 

 meeting of the Geological Society of America, in 1890. J 



* See Walcott : Correlation Papers - Cambrian. Bulletin United Stale* Geological Survey, No. 81, pp. 207-347. 

 ilbid., p. 347. 



t Tbiil.. pp. 207. 3t7. The paper 1ms never been published, but its title occurs on p 634, Vol. 2, BttHetin Geological Society of 

 America 



