ment of some of these Jameco wells which are situated near the northern shore of Jamaica 

 Bay. However, the Jameco wells to the north, though heavily pumped, still yield fresh water. 

 Records from water stage recorders operated by the Geological Survey indicate that pumping 

 of wells screened in the Jameco formation in southern Queens causes a widespread drawdown 

 of the piezometric surface, and that the pumping wells mutually interfere with one another. 



Jwmeco gravel — Nassau County: The Jameco gravel has been indentified in Nassau County 

 with certainty only in a narrow fringing area along the south shore. There, the deposits range 

 in thickness from about 25 to 4 feet and are relatively unimportant hydrologically in Nassau 

 County. There are deep lying outwash deposits in the north shore embayment which resemble 

 both the Jameco and the Upper Pleistocene. However, as they are discontinuous and are not 

 covered by Gardiners clay, it seems more appropriate to place them in the Upper Pleistocene. 



Jameco gravel — Suffolk County: The meager data available at present indicates that no 

 extensive beds of Jameco gravels lie beneath the south shores of the County. The deep lying 

 glacial gravels in the north shore embayments, although they resemble somewhat the Jameco, 

 have been correlated as Upper Pleistocene deposits because they appear to be more closely 

 related to the local beds of Upper Pleistocene than to the deep Jameco gravels of Kings and 

 Queens Counties. Early investigators tentatively classified certain gravel beds in the eastern 

 and northern parts of Suffolk County as part of the Jameco formation. Folding caused by the 

 thrust of the Pleistocene ice sheets has so obscured true stratigraphic relations that certain 

 identification of the beds cannot be made. However, as along the south shore, these gravels 

 are hydrologically unimportant. 



Gardiners clay 



A sharp lithologic change from gravel to clay marks the contact between the subaerial 

 outwash deposits known as the Jameco gravel and the overlying Gardiners clay, a marine 

 interglacial formation. The clays contain warm water fauna and were probably deposited 

 under conditions similar to those which prevail in the bays along the south shore of Long Island 

 at the present time. 



The Gardiners normally consists of a dark gray or greenish gray silty clay containing 

 woody material, diatoms, f oraminif era, and fragments of larger shells ; chiefly pelecypods and 

 gastropods. In some places, the Gardiners may consist of fine sand, sandy clay, and scattered 

 discontinuous lenses of coarse sands; 5 or 10 feet thick. The minerals in the sand residues 

 consist of angular quartz, biotite, chlorite, muscovite, amphibole, and pyroxene. It may also 

 contain glauconite in varying amounts. This mineral may have been derived from the rework- 

 ing of Tertiary or Cretaceous beds which in places contain glauconite. 



The Gardiners clay is the only formation on Long Island which can now be traced from 

 place to place on the basis of fossil content. Even this procedure is rendered difficult by virtue 

 of the fact that much of the fauna resembles or is identical to existing types. The Gardiners 

 clay is not everywhere fossiliferous. The amount of fossil material present varies from rare 

 to abundant in different localities indicating local variations in depth of water and environment. 



Sea level in Gardiners time was at least 50 feet lower than the present level and no beds 

 of Gardiners clay are known to occur above this depth except where they have been pushed 

 up by folding due to the movement of Upper Pleistocene ice sheets. 



Gardiners clay — Kings County: The accompanying contour map of the formation shows 

 that the Gardiners clay underlies all of the County except a narrow belt along the East River 

 and Newtown Creek in the northern part of the County. In these areas it is believed that the 

 clay was eroded in some places and in other places was never deposited. 



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