PLEISTOCENE GEOLOGY OF NASSAU CO. AND BOROUGH OF QUEENS 647 



Washington; hence the ice-laid and the water-laid drift of this epi- 

 sode are here assembled under the name of the Port Wasliington 

 stage of ice retreat. 



Whether some of the deposits lying south of this line and yet 

 north of the moraine, as in the plain north of Green vale station, 

 may not constitute an intermediate series of deposits can only be 

 determined by more evidence than the topography of the deposits 

 alone affords. 



From the village of Port Washington northwestward there over- 

 looks the harbor a thick plain of sand with a lobate margin. These 

 lobes point inward from the east and the north and have their sum- 

 mit line traced by the 80 foot contour line. The plain of sand is 

 free from boulders, and its structure, as shown in numerous deep 

 sand pits, consists of beds dipping everywhere southward toward 

 the shore at angles of about 20°. All about the iceward edge of 

 tlie sand plain are boulder-strewn fields, which on the north and 

 west have a decidedly morainic topography below the 100 foot con- 

 tour line. From near Plum point around the coast of the sound to 

 Mott point this topography is very distinct, forming a rough slope 

 to the sea rather than a ridge ; but the morainal deposits, as shown 

 at Barker point, are a mere veneer over older glacial beds. 



The topography thus defined marks the overlap of the ice sheet at 

 this stage on Manhasset neck, and the sand plain is a delta formed 

 in a body of water whose surface was approximate)}^ at the level of 

 the summit line of the lobate margin of the deposit. 



It follows from this conclusion that, if other sand plains at this 

 level occur to the east and west on the north side of the moraine 

 within approximately the same distance of retreat from the main 

 moraine, the probable position of the ice front at this later stage 

 may be traced by drawing a line along the northern margin of these 

 deltas. 



Another such deposit less clearly developed occurs at Great Neck 

 village at approximately the same hight ; and, as the line between 

 the inner margin of the sand plain and the ice edge on the western 

 part of Manhasset neck turns in this direction, it appears legitimate 

 to associate the two deposits in the manner indicated. The line 

 thus di*awn suffices to show that the front of the ice sheet was at 



