66 NEW YORK STATE MUSEUM 



Structure and composition now belonging to it. Many items of im- 

 portance are indicated in some of these early periods. For ex- 

 ample, the sea encroached on the land borders repeatedly from the 

 westward — especially throughout Palezoic times, while in Meso- 

 zoic and Cenozoic times the evidence of shif tings of sea margins 

 is confined to the east and southeast borders, and likewise probably 

 no near by place has been continuously beneath the sea. 



But the unraveling of these conditions is obscured by subsequent 

 events. Land surfaces that once were, became covered by later 

 sediments. The physiography of those times, Paleophysiography, as 

 well as paleogeography, is therefore a difficult and intricate line of 

 investigation. With these ancient surfaces the dicussion of present 

 features has little to do. Here and there the present surface cuts 

 across and exposes the edges of an older one giving traces of the 

 old profile; but in most cases it is so distorted by the foldings and 

 other displacements belonging to a later period that a restoration 

 of the original continental features is a task fit for the most highly 

 trained specialist. 



The surface as it now exists, and the rock floor modified only by 

 the inequalities of the loose soil mantle, yields more readily to in- 

 vestigations of origin and history. 



b History of present surface configuration. On some por- 

 tions of the region there seems to have been no deposition since the 

 close of Paleozoic time. Throughout most of Mesozoic and Ceno- 

 zoic times, therefore, those regions probably have been continuously 

 land areas (continental) and have been subjected to the agencies 

 of erosion. This appHes particularly to the Highlands region and 

 the Catskills and the Shawangunk range and intervening country. 



What the surface configuration was like in the early stages is 

 wholly unknown. In the beginning, mountain-folding — the Appa- 

 lachian folding — was in progress and the features were probably 

 those of partially dissected anticlinal folds. With the progress of 

 erosion the Triassic deposits were accumulated along the eastern 

 border, probably on the continental slopes. Subsequently, further 

 elevation extended erosion over the Triassic areas also and the 

 Cretaceous beds were laid down on the margin. The general lines 

 of development have been the same from that time to the present. 

 Each successive important formation less heavily developed and 

 forming a band outside of and upon the older one — the whole now 

 constituting a series of successive belts the oldest of which is far 

 inland and the newest at the sea margin. 



