DIVERSITY OF THE GLACIAL PERIOD JJl 



from the glacier which deposited the Jameco gravels. These 

 greater thicknesses in the clay are generally associated with 

 more or less well-defined valleys in the older gravels (see wells 

 5, 8, and i8 in Fig. 5), and the wood in the lower portion is 

 rounded, or waterworn in distinction from the compound pieces 

 of lignite found in the upper portion, indicating the true swamp 

 character of the latter deposits. This would leave a thickness 

 of about 50 feet definitely assignable to the Sankaty period in 

 western Long Island — a thickness which is very similar to that 

 found on Gardiner's Island. 



Merrill reports the clays at the brickyard west of Greenport 

 very much folded, and they, as well as the clays of Robbins 

 Island, may belong to this age. Similar concretionary clays are 

 found in the high hills between Bridgehampton and Sag Harbor, 

 often very near the surface, and sometimes reaching a height of 

 over 100 feet above sea level — a height doubtless due to fold- 

 ing similar to that shown on Gardiners Island. 



The similarity of the stratigraphic position of these beds on 

 Long Island, Gardiners Island, Marthas Vineyard, and Nantucket 

 leaves no doubt of their equivalence to the Sankaty of Wood- 

 worth. 



Gayhead interval. — There is nothing on Long Island which 

 can clearly be referred to this interval except by inference. 

 While there are many cases of folding on the north shore, the 

 time of the folding is not so clearly fixed as in the small islands 

 to the eastward. Still we feel, from the great similarity of the 

 Pleistocene succession in each case, an assumption that the 

 major folding took place at the same time is not unfounded. 

 The main folding on the north shore occurred before the deposi- 

 tion of the typical Manhasset (Tisbury), as is the case in the 

 New England islands. Some slight folding has doubtless 

 occurred since that time, but it is of small consequence when 

 compared with the older. 



Ma?ihasset. — The Manhasset of Woodworth ' consists of a 

 series of yellow quartz sand and gravel, with an intercalated 

 bowlder bed, and on the north shore lies horizontally on the 



'J. B. Woodworth, Bulletin of New York State Museum, No. 48, 1901, Plate I. 



