Rocks of Upper Cretaceous and early and late Tertiary age make up the Atlantic Coastal 

 Plain in western Long Island and northern New Jersey. They consist of lithologically similar, 

 semiconsolidated, sandstones and sandy gravels which overlap toward the northwest and 

 have a regional dip of several degrees to the southeast. Regional strike of the Cretaceous 

 strata is approximately North 60° East, whereas strike of the overlying Tertiary formations 

 is more easterly. (Minard, 1969.) The Cretaceous and Tertiary rocks form a wedge-like prism 

 which thickens to the southeast and unconformably overlies the previously mentioned 

 Precambrian, Paleozoic and Triassic rocks of the Piedmont Province. The maximum exposed 

 aggregate thickness of Coastal Plain strata in northern New Jersey is about 500 feet (Minard, 

 1969); the southern tip of New Jersey and the shelf edge in the Hudson Canyon vicinity 

 have a reported thickness of about 10,000 feet. (Kraft, Sheridan, and Maisano, 1971.) 



Exposures of hematite-cemented Cretaceous sandstones form prominent ridges and hills 

 over 240 feet high in the Atlantic Highlands north of the Navesink River in New Jersey. The 

 Shrewsbury Rocks, south of Sandy Hook, exhibit striking bathymetric expression from the 

 shoreface to about 7 miles offshore where they are truncated by the Hudson Channel. 



Detailed stratigraphic descriptions of the Cretaceous formations of Long Island are 

 included in papers by Fuller (1914), and Suter (1949); Minard (1969) provides a detailed 

 account of the Coastal Plain stratigraphy of northeastern New Jersey. (See Table 1 .) 



a. Long Island. Because Pleistocene glacial till, glaciofluvial and glaciomarine outwash 

 occur as thick and pervasive overburden on Long Island, little is known about the exact 

 geologic nature of pre-Pleistocene bedrock. Most of the data available on pre-Pleistocene 

 strata are from samples and logs obtained from the numerous water wells drilled to depths 

 of hundreds of feet. First-hand data are also derived from a limited number of rock 

 exposures on the northern side of the island where the glacial overburden is absent or thin 

 due to either nondeposition or to subsequent erosion by later glacial and nonglacial 

 processes. 



The contact between Cretaceous and the overlying early Tertiary strata extends in a 

 northeast direction and appears to run offshore in the vicinity of Long Branch, New Jersey. 

 (See Figure 3.) Eastward projection of this contact and lack of Tertiary-type rock in Long 

 Island drill holes support the hypothesis that the youngest bedrock underlying Long Island 

 is Cretaceous in age. 



Upper Cretaceous strata in western Long Island are represented by the Lloyd Sand 

 Member and the Raritan Clay Member, both included in the Raritan Formation and the 

 uppermost Magothy Formation. Porous sand members are excellent reservoirs for ground 

 water in all of the counties of western Long Island, and detailed stratigraphy is presented in 

 several reports by Fuller (1914), Suter (1949), and Soren (1971). 



The Lloyd Sand consists primarily of beds of sand and gravel interbedded with thin 

 lenses of silt and clay and was deposited on a moderate relief erosion surface of the 

 underlying Precambrian metamorphics. Consequently, thickness of the sand varies from 

 negligible in northwest Queens County to about 300 feet beneath Rockaway Beach. It is a 

 major source of high quality freshwater in western Long Island. 



14 



