WALC0TT.1 GEORGIA TERRANE. 107 



Helderberg qnartzite exists at Bernardston, Massachusetts, and another 

 quartzite of different age, about 3 miles west of Plymouth, Vermont, 

 is interstratified with gneiss; and then there is the great quartzite of 

 the Green Mountain range, whose relation to the quartzites interbedded 

 in the gneiss is unascertained. " We can not assume, therefore, that 

 this last is all of one geological age." After examining the quartzite of 

 Canaan, Connecticut, he was led to the conclusion from the facts observed 

 that the quartzite is the inferior rock, and rests unconformably beneath 

 the limestone. 1 



When briefly presenting some conclusions concerning the strati graph- 

 ical structure of the Cambrian of western Vermont, Prof. C. H. Hitch- 

 cock 2 states that Dr. Emmons believed the rocks were deposited against 

 the western base of the Green Mountains, in order of, first, the Granu- 

 lar Quartz, then the Stockbridge limestone, and lastly the various slates 

 which were capped by the black slates holding Olenellus. The report 

 says further: 



Prof. Hitchcock suggested as a better theory of structure, that sediments were formed 

 contemporaneously, both upon the Green Mountains and the Adirondack side of the 

 valley, thus making the granular quartz on the east side of the valley of the same 

 age with the Potsdam sandstone at Whitehall, N. Y., and elsewhere west of Lake 

 Champlaiu. Next, the Calciferous sandstone, Levis, Chazy. and Trenton limstones, 

 were deposited entirely across the valley and by means of their fossils are now iden- 

 tified adjacent to both the quartz rock and the typical Potsdam sandstone. Thirdly, 

 the limestones are succeeded by slates. This theory of original deposition differs from 

 that of Emmons, in supposing that sedimentation was being effected both on the 

 Green Mountain and Adirondack borders, instead of on the former only. 3 



In summing up the account of the discoveries of Eev. Augustus Wing 

 in Vermont geology, Prof. Dana says : 4 



The Red sandrock on the west of the Eolian limestone — admitted to be Potsdam or 

 Primordial in age— and the Quartzyte on the east which often rises into mountain 

 ridges, are of the same formation, and come nearly or quite together in Monktou, on 

 the northern limits of the limestone area (p. 414). 



The quartzyte of the eastern range, with that also of the local belts in the Eolian 

 limestone area, is regarded as Potsdam (or Primordial) in age, because it contains in 

 many places Scolithi (worm-burrows) and Fucoids like those found in the Potsdam 

 sandstone; because also it adjoins Calciferous limestone beds at the localities just 

 mentioned in North Middlebury and New Haven ; and because it joins the Red sand- 

 rock in Monkton, and one rock has in many places the character of the other, although 

 not commonly alike in color, and showing differences explainable on the ground of 

 the greater metamorphism of the quartzyte. " In Monkton, the Red sandrock and 

 the Quartzyte meet in a succession of short anticlinals, thus cutting off to the north 

 the great trough or synclinal;" and "the Red sandrock absolutely overlies the beds of 

 Red sandrock in one anticlinal and the quartzyte in another anticlinal, and both hold 

 Scolithus linearis." 5 



^p.cit.p. 186. 



2 Remarks on the stratigraphical structure of the Cambrian and Cambro-Silurian rocks of western 

 Vermont. Boston Soc. Nat. Hist,, Proc, vol. 18, 1875, p. 191. 



3 Op.cit.,p. 191. 



4 An account of the discoveries in Vermont geology of the Rev. Augustus Wing. Am. Jour. Sci., 3d 

 ser., vol. 13, 1877, p. 414-416; vol. 14, pp. 36-37. 



6 Op. cit.p.416. 



