378 DARTON — GREEN POND, N. J., TO SKUNNEMUNK MT., N. Y. 



appear to be remnants of shore deposits lying against the gneiss and 

 some gritty sandstones of Hudson age. To the north there is a general 

 overlap westward of the Monroe shales and Bellvale flags. In the ex- 

 treme southwest corner of the map is the end of the quartzite due west 

 of Monroe. 



Continuing northward along the same valley there is, between Wood- 

 cock hill and Skunnemunk mountain, a ridge of considerable prominence 

 in which the quartzites are again exposed. The rock is a white con- 

 glomeratic quartzite, and a thickness of about 80 feet is seen. No fossils 

 were observed. It dips eastward with perfect conformity under Monroe 

 shales, in which many lower Hamilton fossils were found. It is cut off 

 on the westward by a clearly exposed overthrust along which it abuts 

 against the Cambrian limestone and for a short distance, against some 

 shales of probable Hudson age. Its relations are shown in section II, 

 plate 17, and in figure 6, page 390. It is represented as Oneida on the 

 map accomj^anying the " Geology of New Jersey," 1868, and by Smock 

 in the section in his paper. 



Two miles north of the end of this ridge, at the northern end of 

 Skunnemunk mountain, I find there is another mass of the quartzite 

 brought up by the pitch of the synclinal. It is underlain by the Helder- 

 berg liuiestones at the Cornwall Station locality, and to the southward is 

 clearly overlain by fossiliferous Monroe shales. It is in the northern end 

 of Pea hill, a northern foothill of Skunnemunk mountain, and is con- 

 spicuously exposed along and near the road from Woodcock hill to 

 Cornwall Station. It is a conglomeratic quartzite similar to the others 

 southward, but consists mainly of somewhat smaller pebbles and large 

 sand grains. No fossils were found, but careful search was not made. 

 About 30 feet are exposed, and the area of outcrop is only a couple of 

 acres. Its relations are shown in section I, plate 17 and in figure 3. 

 Possibly other exposures of the Oriskany may be found along the edges 

 of the Monroe shales, for I did not examine its entire length. There are 

 long distances in which there is drift cover, but in several localities the 

 formation is apparently entirely absent. 



In designating the formation Oriskany I do not intend to give the im- 

 pression that it is precisely equivalent to the Oriskany sandstone of 

 central New York. Probably the sediments comprise the greater part 

 of Oriskany group if the sedimentation was continuous in this belt. 



Helderherg Limestone. — The limestones of this formation occur at in- 

 tervals along the belt to which this paper relates, and their characteristic 

 fauna affords important evidence as to the stratigra^jhic position of the 

 associated formations. The most interesting locality is at Cornwall 

 Station, where the occurrence of the formation was announced over half 



