NEWARK ROCKS OF ROCKLAND COUNTY, N. Y. 21 



A mile and a half northeast of Blauvelt's foundry is a place 

 called Limekiln. Here many years ago the calcareous conglomer- 

 ate was quarried somewhat extensively and burnt for lime. In the 

 quarry, beds of massive conglomerate containing boulders two 

 feet in diameter occur. Interbedded with the conglomerate are 

 thin layers of silicious sandstone. Similar rocks outcrop at 

 intervals for some rods from the quarry, but the highly calcareous 

 conglomerates do not extend uninterruptedly to the exposures 

 near Blauvelt's foundry. Calcareous conglomerate interstratified 

 with beds of sandstone also outcrops along the road a mile and a 

 half southwest of Ladentown. 



The above are the important localities where the highly cal- 

 careous conglomerate is known to occur. A series of ledges of 

 coarse sandstone, interbedded with thin conglomerate beds, occurs 

 for over a mile along the top of the ridge west of the New Jersey 

 and New York railroad between Pomona station and New Hemp- 

 stead station. The conglomerate beds, because of the numerous 

 limestone pebbles contained in them, are more easily weathered 

 by solution than the silicious sandstones, and the latter therefore 

 project as shelves for 1 or 2 feet. Other localities where the 

 sandstone and more silicious conglomerate can be seen have 

 already been noted. 



Thickness. Only a part of the Newark beds are represented in 

 the New York area. In consequence of faulting along the north- 

 western border, the upper beds are wanting and the bottom beds 

 are concealed beneath the waters of the Hudson. The thickness 

 is consequently much less than in some parts of New Jersey, but, 

 on account of the impossibility of making correct allowance for 

 unknown faults which may repeat the beds, no estimates were 

 made. Estimates of the maximum thickness for the series in 

 New Jersey varied from 11,800 feet to 14,700 feet ? but even here 

 the presence of several unknown factors may have introduced a 

 large error into the figures. 



