9^ NEW YORK STATE MUSEUM 



trusion which extends southward through New Jersey onto Staten 

 Island and is also encountered in the interior of Rockland county. 

 The Palisades are the exposed edge of a sill or sheet of diabase that 

 is intruded between shales and sandstones of Triassic age. The 

 sheet is several hundred feet thick, in places nearly iooo feet, and in 

 general seems to follow the bedding planes of the sedimentary 

 strata which dip to the west and northwest at an angle of from 

 5° to 1 5 . The outcrop is narrow, seldom over a mile, and in 

 places is limited to a single steep escarpment. The principal 

 quarries are near Nyack and Haverstraw at the base of the cliffs. 

 Other quarries have been opened near Suffern, Rockland county, 

 on an isolated intrusion, and also near Port Richmond, Staten 

 Island, at the southern end of the Palisades sill. 



Trap occurs in numerous places in the Adirondacks, but mostly 

 as narrow dikes. It is especially common in Essex and Clinton 

 counties where there are many thousands of dikes that range from 

 a few inches to 20 or 30 feet thick. On the southern border of the 

 region are a few dikes of notable size, such as that in the town of 

 Greenfield, Saratoga county, and at Little Falls in the Mohawk 

 valley. A quarry has been opened in the Greenfield occurrence for 

 the supply of crushed stone. 



The quarrying of trap along the face of the Palisades in Rockland 

 county probably will soon be discontinued, as it is designed to 

 purchase the quarry properties for the Palisades Interstate Park. 

 The lands to be included within the park extend from the river line 

 to the top of the Palisades. So far only the Manhattan Trap Rock 

 Quarry has been taken over, but negotiations are proceeding for 

 the acquirement of the other quarries along the river front. 



The future of the industry in this section is somewhat unsettled. 

 It is not unlikely that new quarries may be opened on top of the 

 ridge and in the interior of Rockland county, though the facilities 

 for production and shipment in that section can scarcely be equal 

 to those of the present localities. 



