Works^ williBgly made airailable members of the staff nho assisted the Geological 

 Smnrey in maJdjog the isater-leYel sieasiireiBents in May 1943 • Mr^ Henry L# Frauenthal, 

 of the saine organization^ offered many helpful suggestions • Gi^tefal acknowledg- 

 ment is also due Mr* Russell Stifcer, Executive Eigineer of the Mew lork State Water 

 Power and Control Commission^ whose constructiTe criticise led to notable iaqprove- 

 ments in the map# The coverage of western Suffolk County was made possible by the 

 financial cooperation of the Board of Superidsars and the Water Authority of that 

 county* %.e draftiiag of the map and sections was executed by !&•• Lauren E» 

 Wistoft^ of the Geological Survey • 



GEOLOGI 



The geology of Long IslaiKi has been discussed at length by several writers 

 (6) (10) (12) (IS) and will therefore only be sketched briefly hei^# 



Long Island is formed of glacial deposits of varying thickness that were laid 

 down on unconsolidated beds of Cretaceous age« The backbone of the island is a 

 double row of hills representing terminal moraines fashioned by the great ice 

 sheets of iiie Pleistocene epochs South of these morainal deposits is an outwash 

 plain that slopes gently toward the oceani> The outwash material is quite perme- 

 able and raitier uniform in structure » The water table in the area south of tiie 

 moraiiBS is accordingly a more or less continuous surface of low slqpe^ though 

 modified somevbat by the streams that it feeds* 



Along the north shore of the island the glacial deposits are much less 

 homogeneous and generally less permeable^ being con^osed in part of till* Numerous 

 bays cut into the dtiore of the island along the sound* Flowing into these bays 

 are many small streams of steep aLope^ some of i&ich are fed by natural springs* 

 In the area north of the moraines there are several anaH lakes and water tables 

 perched on iis^ermeabLe lenses above the main water table* There the main water 

 table slopes steeply and in irregular fashion, generally toward the north shore* 



