observed in eastern Nassau and western Suffolk Counties. In other parts of Long Island, the 

 Mannetto gravel was either never deposited or has been removed by later erosion. In this report, 

 the Mannetto deposits are not recognized as a separate unit but if present have probably been 

 included with later Pleistocene beds due to the difficulty in separating the gravels in well logs. 



The Jameco gravel is most extensively distributed in Kings and Queens Counties and in 

 a small area in southern Nassau County. The distribution and extent of the gravels in Suffolk 

 County is at present not well known. 



The Jameco either rests unconformably on the Cretaceous deposits or on bedrock in 

 northwestern Kings County. In turn it is overlain by the Gardiners clay. The name Jameco 

 was first introduced by A. C. Veatch (9), who applied it to the water-bearing sands beneath 

 the Gardiners clay at the Jameco pumping station of the City of New York situated in southern 

 Queens County. As typically developed in the western part of the Island, the Jameco deposits 

 consist predominantly of dark brown, dark gray or multi-colored beds of coarse sand and 

 gravel containing some cobbles, boulders, and scattered layers of silt and clay. In contrast to 

 the Cretaceous deposits, the Jameco contains very little quartz and is composed chiefly of 

 fragments of fresh granite, diabase, gneiss, schist, sandstone, shale, and pegmatite. It contains 

 also grains of chemically unstable minerals such as felspar, amphibole, pyroxene, biotite, and 

 chlorite. The pebbles and grains of the Jameco are usually well rounded and water worn. The 

 composition of the deposits may vary somewhat from place to place depending on the source 

 of the outwash material. 



In the type locality at the western end of Long Island, the gravels lie 100 or more feet 

 below sea level and are overlain by beds of Gardiners clay which confine the water in the 

 Jameco gravels under artesian pressure. Numerous breaks or channels in the clay permit 

 direct recharge of the Jameco from overlying deposits of Upper Pleistocene age. The forma- 

 tion has a gentle southward slope, and nowhere crops out at the land surface. 



Jameco gravel — Kings County: The Jameco beds can be tapped by wells almost everywhere 

 in the County except the northern and northwestern sections. The limits of the deposit are 

 indicated on the accompanying contour map of the Jameco. Its thickness ranges from about 

 50 to 150 feet. The thickest beds occur as valley fill deposits in deep pre-glacial valleys which 

 cross the county from northeast to southwest. The elevation of the upper surface of the Jameco 

 ranges from about 100 to more than 200 feet below sea level. The aquifer has, in the past, 

 been an important source of water for public supply in the Flatbush section of Kings County. 

 Heavy pumping caused gradual encroachment of sea water. The resultant contamination of 

 the aquifer necessitated complete abandonment in 1947 of all the remaining public supply 

 wells in Kings County. 



At the present time only a few industrial wells draw water from the Jameco gravels in 

 Kings County. The aquifer may take on renewed importance as a source of ground water for 

 cooling purposes if the water temperature of the upper Pleistocene deposits continues to rise 

 due to excessive recharge of warm water from recharge wells. 



Jameco gravel — Queens County: The area in which the Jameco is developed to the greatest 

 degree lies in the southern part of Queens. Except for a few isolated remnants the Jameco 

 is absent in the northwestern part of the County. The top of the Jameco ranges from 

 about 80 to 250 feet below sea level. It lies at greatest depths in the vicinity of Rockaway 

 Beach in southern Queens. The thickness of the Jameco ranges from 30 to 150 feet, being 

 thickest where it fills pre-Pleistocene valleys. 



The irrgularities of the upper surface of the Jameco, as shown on the accompanying 

 contour map, suggest that some erosion of the Jameco surface may have taken place before 

 deposition of the overlying Gardiners clay. The aquifer is tapped in southern Queens County 

 by many public supply wells. Intrusion of salt water from Jamaica Bay has caused abandon- 



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