70 NEW YORK STATE MUSEUM 



the low ground along the railroad and gives way at the north to 

 slates, although some distance intervenes between outcrops. The 

 northern margin is plainly a faulted one and lies along the very 

 prominent but narrow valley that forms the route of the Central 

 New England Railroad track almost the entire distance from Hope- 

 well Junction to Manchester Bridge. That this represents a line of 

 faulting is reasonably certain. As a topographic feature it may be 

 followed across country for miles. It is often swampy, frequently 

 for long distances, and this feature was probably still more prom- 

 inent before the railroad bed' was put in. It does not have the 

 appearance of having been a prominent line of drainage, but rather 

 a more extensive illustration of the topographic effect of base-level- 

 ing forces operating along a continuous line of weakness such as a 

 great fault would produce. There are other conspicuous illustra- 

 tions of the same kind, both within the slates and limestones of this 

 t^uadrangle. 



( The southern margin is obscured by a great mass of drift, but the 

 limestone is almost certainly cut by a fault on the southwest. 



A mile and a half north of New Hackensack a crossroad con- 

 nects the New Hackensack road with another running for some 

 distance parallel with the railroad track. The northwestern margin 

 may be followed from this road northeastward to the railroad track, 

 outcrops appearing between the latter and the road just south of it. 

 Along this margin the limestone shows a low scarp for some dis- 

 tance. The eastern margin is also easily followed as a scarn from 

 the crossroad where the limestone appears in contact with the 

 black, splintery slates northeastward to the railroad. Outcrops 

 occur along the public road at the north. Everything is concealed 

 south of the crossroad at the south. 



The limestone of this block is of a very dark bluish-gray color. 

 It often shows veinlets and nests of calcite. Fresh surfaces show 

 darker and more crystalline bunches in a rock of dark gray color. 

 The rock is more crystalline than other members of the ^^'apping•er 

 creek belt. In litholcgy, it often has a strong resemblance to 

 varieties met with in the Fishkill limestone, notably southeast of 

 Hopewell. No fossils were found. The average strike is about 

 n. 60° e. and the dip 40° s.e. The block forms a distinct topo- 

 graphic feature. 



THE FISHKILL LIMESTONE 

 The belt of which this limestone is a part may be traced with 

 some interruptions from IMillerton in the northeastern corner of 

 Dutchess county nearly to the Hudson river. The portion within 



