﻿74 NEW YORK STATE MUSEUM 



flat that drainage is essentially dendritic modified slightly by joint- 

 ing. The great relief of the Catskills is due wholly to erosion 

 of flat but very resistant strata that withstood the destructive ero- 

 sion of Cretaceous peneplanation and stand as residuary rem- 

 nants even to the present time. The Catskills are therefore essen- 

 tially a Monadnock group. In structure they are almost as simple 

 as the higher portions of the cuesta of Long Island, and they hold 

 the same relation to the forms developed by erosion out of the 

 old Paleozoic coastal plain of the interior. 



Summary 



Physiographically the most complex zone is midway in the region 

 under discussion — i. e. The Highlands. This belt is bordered on 

 both sides by less complicated zones of less relief, of more regular 

 topographic forms and less obscure history — the Piedmont zone 

 on the south and the Paleozoic folds on the north. The outer mar- 

 gins are both simple, essentially eroded coastal plains with strata 

 dipping away from the central belts and on which forms and drain- 

 age lines characteristic of such history are developed. These outer 

 zones are the coastal plain of Long Island on the south and the 

 Cat skill Monadnock group on the north. It matters little that they 

 differ in age by almost half of the known geologic column. 



