NEWARK ROCKS OF ROCKLAND COUNTY, N. Y. 



31 



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press me as being a fault gap. The rise of the contact is appar- 

 ently somewhat gradual, indicating an unconformable contact rather 

 than a fault. 



At Short Clove there is another small 

 change of elevation, of not more than 

 30 feet, due possibly to a small fault 

 or to another unconformable contact. 

 The base is here about 180 feet above 

 the river. From this point west to 

 the end of the ridge no definite state- 

 ment can be made as to the structural 

 relations which prevail between the 

 trap and sandstone along the northern 

 border. Nowhere is the actual con- 

 tact revealed. At only two localities 

 has the sandstone been found any- 

 where near the trap. At one of these, 

 an old quarry under Little Tor, the 

 strike of the sandstone is nearly at 

 right angles with the trend of the trap 

 ridge, and the beds dip 10° westward. 

 Two layers of trap having a maximum 

 thickness of 4 feet have been intruded 

 into the sandstones in this quarry. 

 They can be traced for about 25 yards 

 generally conformably to the sand- 

 stones, and finally disappear by peter- 

 ing out. The sandstones near the 

 dikes are unaltered. Their junction 

 with the main trap mass is not shown. 

 At the other locality near the terminus 

 of the ridge, the conglomeratic sand- 

 stones dip toward the trap as if they 

 passed beneath it. It is impossible to 

 say whether, from Short Clove west- 

 ward, the trap and sandstones abut 

 against each other along a steeply inclined contact plane which 

 trends parallel to the direction of the ridge, i.e. a dike contact, 



vTrough Hollow 



//:W) — 



m 



North 



Fig. 4 Section showing the uncon- 

 formity of the trap and sandstone along 

 the Hudson river near Rockland land- 

 ing. 



