POSTGLACIAL FAULTS OF EASTERN NEW YORK J 



locations are exposed for 25 or 30 feet ; and it should be remarked, 

 that they do not occur in the vicinity of a ledge, a cliff or steep hill- 

 side of rocks, or upon the side of a hill, but upon a level surface 

 upon the summit.^ 



Mather^ also reported another locality east of the Hudson near 

 Hyde Park. He states that 



The smoothed and scratched gre3^wacke or grit was observed 

 on the ridge east of Hyde Park; and about half a mile east of 

 the post road opposite to half a mile north of De Graff's Tavern, 

 the grooves and scratches, which were perfectly similar in size, 

 depth and direction, were interrupted by slips or slight faults 

 of the rock since the scratches have been made. Professor Cas- 

 sels observed them in several places in that vicinity. The edges 

 of the rock, both above and below, on the sHp, were sharp, and 

 the grooves and scratches of the lower mass were continuous 

 plump up to the surface of the upper mass ; and on the upper mass 

 they were continued quite to the sharp edge along which the slip 

 has taken place. 



This type of relatively recent faults appears next to have been 

 seen and described b}^ Mr G. F. Matthew as occurring in a very 

 pronounced manner in the environs of St John, New Brunswick. 

 The Cambric slates of the upper division of the St John group 

 are described by him as being cut by n. e. and s. w. faults, with 

 a hade varying from 60° to 80° s. e. There are also diagonal 

 faults extending north and south, and east and west. In the 

 city of St John, the faults vary in downthrow from 54 irich to 

 4 inches, the downthrow with one exception being on the north. 

 In one locality Matthew found the sum of the displacements to 

 be 5 feet 8 inches. He has published a photograph showing the 

 character of the faulted surfaces.^ 



Matthew noted the reversed character of the faults and sup- 

 posed the movement to be due to a failure of support beneath, 

 or to a lateral thrust from the southeast, with his preference for 

 the latter view, in support of which he cites the ancient moun- 

 tain-building pressures acting in this direction. He also notes 

 the pressure acting on the rocks at Monson, Mass., reported by 

 Niles, and the occurrence of slight earthquake shocks near St 

 John, N. B., as evidence independent of the faults that the 

 earth's crust in this part of the continent is yielding under 

 strain. 



IMather, W. W. GeoloRy of New York: Report on First District. 1843. p. 156-57. 



^Op. cit. p. 387. Locality not visited by J. B. W. 



sPost-glacial Faults of St John, N. B. Am. Jour. Sci. Ser. 3. 1004. 48:501-3, pi. 11. Also 

 Movements of the Earth's Crust at St John, New Brunswick, in Post-glacial Times. N. B. Nat. 

 Hist. Soc. BuL 12. 18.94. P- 34-42., 



