PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS 635 



the surface of the formation north of the moraine is carved into 

 valleys and deep reentrants of the coast line, depressions the main 

 features of which are consonant neither with the southward move- 

 ment of ice over the area nor the erosive work of subglacial streams 

 discharging across them at the ice front. That these valleys ante- 

 date the last ice advance appears to be shown in that all of them are 

 more or less encumbered by morainal materials. 



As typical examples of these valleys, that entering into Manhas- 

 set bay at Glen Cove, as well as that in whose lower extension Mill 

 Neck creek flows, may be taken. The Glen Cove valley heads at 

 the inner base of the moraine near a very well marked pass at the 

 eastern base of Harbor hill, a passage through which undoubtedly 

 subglacial waters escaped when the ice front lay against the moraine 

 and at a time when it must be admitted subglacial drainage may 

 well have followed the course of this valley for a part or a whole of 

 its course. The objections to accepting the valley, however, as the 

 work of this subglacial stream, aside from those above stated, are 

 1) the graded character of its bed, sloping northward toward the 

 sea as if made by a normal stream like that now flowing in it, 

 though the existing stream evidently flows in a valley which it 

 found encumbered by more or less glacial drift ; 2) the tributary 

 vales evidently cut by running water as in normal open air streams ; 

 3) the course of the stream at Glen Cove, east and west, in a direc- 

 tion contrary to ice movement in this locality. The digitation is 

 even more pronounced in the case of the Mill Xeck creek valley 

 just south of the ponds. The upper part of the valley above the 

 100 foot contour is also walled in by glacial deposits later than the 

 Columbia in which it is cut. Like considerations hold in regard to 

 the deep valleys which extend from Oyster Bay village toward 

 East Korwich. The Mill Neck creek depression continues below 

 scale vel, and, branching south of Oak neck, separates that island — 

 an island except for the barrier beach tying it to the land on tiie 

 west — from Mill Neck. It is evident that there has been developed 

 a marked dissection of the Columbia, and that this dissection on north 

 and south as well as on east and west lines is increasingly severe 

 toward the northern coast, as in the normal degradation of an area 

 of incoherent materials marginal to a depression such as that of 



