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NEW YORK STATE MUSEUM 



front as if spreading out on the lowland at the southern entrance 

 to the Highland canyon. It is reasonable to suppose that at this 

 stage the ice pressing against the northern slope of the Highlands 

 and having thinned too much to flow over these ridges forced a 

 long tongue through the Highlands comparable to the ice streams 

 which are pressed out from the inland ice of Greenland to the west 

 coast. With, this stage some of the higher terraces and morainal 

 deposits in the Highlands may be associated. Later the ice dwin- 

 dled away melting at surface and also on its sides thus permitting 

 the deposition of gravels and sands about its margins and over 

 the rock terraces which at this stage bordered the dead ice in the 

 gorge. With the melting out of this ice, the glacial occupation of 

 the Lower Hudson was closed. 



An earlier chapter in the glacial occupation of the lower Hud- 

 son valley is recorded in the terminal moraine and possibly also 

 in the clays at Haverstraw which are covered unconformably by 

 later sands and gravels. If the view be correct that the terminal 

 moraine at the Narrows is the so called " inner " or Cape Cod 

 moraine and that the " outer " or Nantucket moraine is to be 

 found overrun by ice and suffused in the region immediately north 

 of the Narrows it is probable that in the lower Hudson valley 

 as on the east in Massachusetts the ice advanced some distance 

 in taking up its position along both of these ice fronts. Con- 

 sidering these frontal moraines as respectively culminating the 

 earlier and the later Wisconsin epoch, in the interval between the 

 two episodes of southernmost prolongation of the ice front there 

 would be opportunity for the deposition of some of the older clays 

 which are found as far north as Haverstraw. On the other hand 

 it must be recognized that the advance of an ice sheet causes it 

 to overrun all deposits wmich have been laid down in front of it 

 in its own time. It does not, therefore, from the evidence at hand, 

 appear possible to conclude definitely whether the Haverstraw 

 clays pertain to the latest Wisconsin or to an earlier epoch. That 

 no clays are found in the lower Hudson overlying the deposits 

 contemporaneous with the ice fronts in the Hudson valley, makes 

 it evident at once that in this field none of the geographic con- 

 ditions have prevailed which produced the widespread clays of 

 the upper Hudson valley and the Lake Champlain district. 



