Upper Glacial

Exceptforasmallportion pfsareetaxdi mrofe depositad on Longlsland, the upper sectionci cedimenlson tl^eis^i^i^d r^na^^oflP^e^i^l^ec^tins^l^icMc^cii^c^s^^fiv^^i^^lXsvrre a resultef Wisconein ift^^ mlsclation.nhe upper glacial deposits lie unconformably atop the subcropping Matawan/Magothy, Jameco Gravel and Gardiners Clay.

Giaxidlsroui hascut defniyintosubcroppinptosmations,perticnlarIymte ahe Matawan/Magothy section. The upper glacial deposits outcrop at the surface and rxpresexta dullrangpof aiacIaCdeppcitis>nal endisonmrcSffrommoixineto ouCwash jrioin toiceustsmo.Uppenglanial canrecca mtfsickness ofVOOfert The oaomorphology of Long Island is marked by the resultant hills of the Ronkonkoma and Harbor Hill moraines and gently sloping plains associated with glacial outwash depesfe Tneuoectnlatial derotttsmake up the Upper Glacial aquifer, which is the predominant source of private water supply wells. The moraines consist of till con^osed ofsand, clay and gravel and display an average horizontal hydraulic conauctiviryof 13n feet;per dry(Smolensky et al., 1989). The highly permeable stratified drift of the outwash plains that lie south of the moraines consists of fine to very coarse grained quartzose sand and pebble to boulder sized gravel. The average horizontal hydraulic conductivity of the glacial outwash deposits is 270 feet per day (Smolensky et al., 1989).

Holocene deposits, which are as much as 50 feet thick and consist of salt-marsh deposits, stream alluvium, and beach sands, occur locally throughout the island. Holocene deposits consist of sand, clay, silt, organic muck, and shells. They are at land surface and generally overlie Pleistocene deposits. They are either unsaturated or too thin and discontinuous to form aquifers. In some areas, they form local confining units.

Geologic Unit



Upper Glacial Aquifer



Gardiners Clay (Kings & Queens Cnty)

confining unit

Jameco (Kings & Queens Cnty)


Monmouth Group (south shore)

confining unit

Upper Cretaceous

Magothy Formation


Raritan Fm - Clay Member

confining unit

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