044 NEW YOKK STATE MUSEUM 



tlio one time presence of an ice remnant. The marpns of tlie 

 depression also ai*e contoured as if by deposition a^^ainst a mass of 

 ice. It is j)recisely in tliis portion of the ice front that the crest of 

 the moraine beai-s indications of havintj been overridden bv tlie ice 

 (p. «3S. 



The traii>iu<->runiiii water courses are bcs-t .studied at Itoslyn. At 

 this point the glacial stream excavated a trench nearly 40 feet deep 

 in the gravels immediately adjacent to the moraine on the south, 

 fi)rming well defined terraces fairly well brought out by the con- 

 toui-s on the map. About a mile below Koslyn this crease turns 

 sharply eastward for half a mile, then straightens out and continues 

 southward by Albertson, to the east of East Williston and thence to 

 the sea. 



The frontal plain near Creedmoor e.vhibits no marked trace of a 

 crease, and many creases which are distinct on the outer southern 

 margin of the outwash plain become faint and practically disappear 

 as surface features nearer the moraine. This fadinjr of creases 

 would be caused by the wandering of streams over the surface, 

 spreading gravel and sand, with the aggradation or building up of 

 the plain by the streams near the ice front so long as they were 

 overloaded with debris. 



The creases on the eastern part of the Hempstead quadrangle are 

 deflected southwestward into the Jamaica bay depression. East of 

 that region, the streams flow generally southward, the numerous 

 creases marked by the 100 foot contour line, for instance, gathering 

 southward into six or seven drainage channels through wdiich small 

 streams now drain the water from the plain. 



Outtoash jtlain. The outwash plain is evidently more complex 

 ii; its origin that its mere surface would indicate. The disap- 

 pearance of the older Pleistocene gravels beneath the nioiaine on 

 the north at about 200 feet above the sea has already been noted. 

 Just as the level of these deposits falls off on the north side of the 

 moraine to the westward, so does the bight of the outwash plain, 

 and, for that matter, that of the main moraine itself. There is good 

 reason for holding therefore that the so-called Cohnnbia deposits 

 extend south of the moraine and presumably underlie the outwash 

 plain, if they do not actually form here and there surface exposures. 



