628 NKW YOKK STATK MUSKUM 



of the area of the Oyster Bay rjuadrangle at this time. The thin- 

 ness of tlie bed, anil the identity of the sediments wliich underlie and 

 snecetnl it, go far to show that tliis boulder clay making was but an 

 episode in the formation of the gravels and sands in this field. 



The outcrop of the boulder clay bed on the bluffs gives rise to 

 boulders which have slidden down the slope. A section transverse 

 to the face of the bluff in one of the pits showed an ancient talus of 

 boulder clay extending down to the road. Not only the texture 

 and structure of the sands and gravels, but also the appearance of 

 the l>oulder clay bed in these pits indicates that these deposits 

 extended eastward across what is now the bay to the like deposits on 

 the opposite bluff. Nowhere do the deposits show that increasing 

 coarseness toward their exposed edges which is the characteristic 

 nuirk of the heads of glacial sand plains and those bodies of glacial 

 sands and gravels which have accumulated about the edge of a gla- 

 cier or its outlying stagnant masses. The bays are clearly valleys of 

 erosion cutting through both the Pleistocene and locally the pre- 

 Pleistocene clays and sands alike. 



A bed of till, presumably an extension of that above described, 

 occurs on the east shore of llem])stead bay in Glen Cove about 60 

 feet alM»ve sealevel, in the following incompletely exposed section. 



TLKISTOCEXE SECTION IN GLEN COVE, FROM TOP 



(iravfl and fine sand 3 ft 



Till, with small angular boulders 5 



(iravel, clavcv 1 (5 in. 



Gravel, sandy ;^> 



Sand, base not seen ;] 



20 feet distant the till passes into stratified gravel and sand. The 

 rapid transition of the till into stratified drift at this locality explains 

 the absence of the bed in many sections. It was probably locally 

 dejX)8ited. 



A similar till bed dihtinctly less bouldery but equally amorphous, 

 is exposed in the bluff at Barker point, from which, first appearing 

 at a]>out 20 feet above the sealevel, it sinks, on the western face of 

 this headland, southward, being involved in the dislocations of the 

 north coast of the island (tig. 2). 



