GEOLOGY OF THE WEST POINT QUADRANGLE, NEW YORK II7 



a height of hetween 600 and 700 feet at Haverstravv. if this piano, 

 which is fairly continuous and very definite, is projected to the High- 

 lands across the Haverstraw-Stony Point lowland, it would strike the 

 mountain mass of Dunderberg and Anthony's Nose and adjacent 

 mountain masses much too low to correspond to any prominent 

 physiographic feature on these mountainsides or elsewhere in the 

 Highlands, except the ground near Peekskill and to the east and 

 northeast of that point. The Cretaceous peneplain of the High- 

 lands, if the tops of the mountains may be assumed to represent 

 that feature roughly, is several hundred feet higher than the pro- 

 jected peneplain as thus traced toward the Highlands from the 

 south, and it may be that the only meaning to be attached to this 

 discrepancy is that some of the displacement along certain lines is of 

 Post-Cretaceous Age. 



The writers are inclined to believe that this is the proper explana- 

 tion of the abrupt break in planes. Traced to the northeast, the dis- 

 crepancy in levels fades out and there is no such additional movement 

 suggested at all, for the weaker phyllites and limestones come in direct 

 contact with granite and gneiss and are eroded to the same level 

 along the contact without any physiographic expression whatever. 

 Even the fault zone is not marked by any feature in most places. If 

 there has been movement in Post-Cretaceous time along this fault, it 

 is all confined to the extension of the line as it follows the edge of 

 the Triassic fault block toward the southwest. 



Yet another explanation has been suggested by the studies of Bar- 

 rell ^ f or the steplike arrangement of erosion planes in the northern 

 Appalachians. He argues that advances of the sea have developed 

 these forms as marginal and submarine planation eflfects in later 

 Tertiary time. With this explanation the faulting or deformation 

 question drops largely out of consideration as no deformation, beyond 

 that accomplishing enough depression of the whole region to permit 

 the sea to invade and enough re-elevation to cause its retreat, is 

 necessary. Barrell seems to have substantiated his explanation in the 

 region studied by him. We are not able to say, from the facts at our 

 command in this particular area, the West Point quadrangle, whether 

 or not marine encroachment should be accepted as the best explana- 

 tion here. 



Later Mesozoic overlap. It seems to be the belief of the physio- 

 graphers who have studied the New England and New York region 



^ Joseph Barrell, The Piedmont Terraces of the Northern Appalachians. 

 Am. Jour. Sci. 49:257, 258, 327-362, 407-428. (1920) 



