410 



Report of thk State Geologist. 



mollusks and trilobite fragments. The species determinable were a Dalma- 

 wites, Leperditia alta, Meristella he vis, Nucleospira ventrieosa and Oodospira 

 conca/va* To the east of the Hudson river slate area is the right branch of 

 the Cambrian limestone belt which spreads eastward to Bell vale mountain 

 and northward to Sugar Loaf mountain and underlies the broad, flat 

 Warwick valley. 



From the strikes and dips obtainable, the indications are that the 

 Cambrian limestone underlies the slates with a constant, though varying 

 degree of unconformity and which are themselves brought up by low folds; 

 the Mounts Adam and Eve area being along the axis of a low anticline. The 

 section adapted partly from Professor Kemp's paper, is given in figure 3. 



Geology of the Region along Bellvale Mountain. 



Bell vale mountain enters Orange county from New Jersey along the 

 west side of Greenwood lake, and extends to a point about four miles north 

 of the latter, with an elevation of 1,200 to 1,300 feet A. T., beyond which it 

 extends as a discontinuous rounded ridge with greatly diminished elevation, 

 merging into the southwestern continuation of Skunnemunk mountain, 

 northwest of Monroe. The latter extends, as a high doubly crested cliff - 

 topped ridge, nearly to Cornwall. 



The general structure of Bellvale mountain is that of a compressed 

 synclinal of Devonian rocks, a portion of whose western limb has been cut off 

 by a fault, and the missing member replaced by gneiss. 



The geologic age of this belt has been, for many years, a disputed point 

 among geologists. Horton, in his report on the geology of Orange county, 

 refers to Bellvale mountain, and states that the southeast side, to}), and about 

 one-third of the slope on the northwest side are composed of greywacke and 

 greywacke slate, standing nearly vertical. 



On the geologic map of New York, 1844, the area of Skunnemunk 

 mountain is put down as Hudson river slate. On the New Jersey geologic 

 map of 1868, Professor G. H. Cook referred these rocks to the Potsdam. 



In 1871, 1). S. Martin found the first fossils of this belt in a so-called coal 

 mine on Skunnemunk mountain. (The Coal of Orange county, N. Y, Proc. 

 X. )'. Lye. Nat. ///*., I., p. 2f>i>.) Professor Martin states that the coal mine 

 of .Monroe lies upon the western side near the summit of the mountain. The 

 rock is a dark grey siliceous or argillaceous sandstone, carrying carbonaceous 



* J. F. Kemp and A. Hollick. On the Granite at Mounts Adam and Eve, Warwick, Orange county, N. Y.. and its Contact 

 Phenomena. Annul* of New York Academy of Sciences, VII, p. «:)8. 



