AREA NORTHWEST OF MONROE. 



377 



conglomerate beds of white quartz pebbles and a few reddish streaks. 

 Ninety to one hundred feet are exposed. 



These two areas are shown as Oneida on the map of the Paleozoic and 

 Azoic formations accompanying the Geology of New Jersey, 1868, but 

 I believe that they are Oriskan}-. They are very similar to the other 

 Oriskany beds, and have the same relations to the Monroe shales. Their 

 proximity to the Hudson formation is due either to overthrust or overlap. 

 Unconformity to the Hudson beds is exposed at a number of points, par- 

 ticularly at the southern end of the southern mass, and it appears to be 

 due to overlap. Along the strike, a mile northeast of the southern end 

 of the larger mass of quartzite above described, there are three small 

 lens-like masses of the quartzite, 

 and in 1885 I discovered under 

 the southernmost of them a 

 limestone containing unmistak- 

 able Helderberg fossils. This 

 strengthens very greatly the 

 view that they are all of Oris- 

 kan}^ age. The relations of this 

 limestone are shown in section 

 IV, plate 17. There is no possi- 

 bility of overthrust at the base 

 of the quartzite at this point, 

 and the conform it}"" of the over- 

 lying jNlonroe shales is clearly 

 apparent. 



The three small areas consti- 

 tute a line of. knolls along the 

 foot^ of the western slope of 

 Skunnemunk mountain, and 



are probably part of a continuous layer, which is cut off northward by 

 overlap or possibly by a fault. They are white quartzites, with few peb- 

 bles, and present a thickness of about 25 feet at greatest. Along the 

 Hudson shale and sandstone and crystalline slopes westward there are 

 two small outliers of similar (piartzite, but more conglomeratic in char- 

 acter, which appear to be deposited across the unconformable overlap of 

 Hudson beds, on the gneiss. Smock has a map of this region in his 

 paper, in which one of the areas is shown as Potsdam and the two over- 

 lapping masses as Oneida. No fossils were found, but from the evidence 

 above presented I believe the masses are all Oriskany. The areal rela- 

 tions in this district are shown in figure 2. 



In this map the three lenses of quartzite are shown on the right-hand 

 side, and the two areas of conglomerate are near the center. The latter 



Fkjcre 2. — Region northwest of Monroe, New York. 



