transect (Fig. 9) contains 15 cores which extend a maximum o£ 108 feet 

 (33 meters) below sea level. Seaward o£ core V-3, the Pleistocene- 

 Holocene sequence is about 20 feet (6.1 meters) thick and the Gardiners 

 surface is at -76 feet (-23.2 meters) MSL. None of the cores appear to 

 penetrate Monmouth strata. The east transect (Fig. 9) contains 11 

 shorter cores which extend a maximum of 94 feet (28.7 meters) below sea 

 level. Most of the cores show marked variations in sediment types and 

 all but the three inshore cores contain abundant glauconite, suggesting 

 sediment derivation from underlying Monmouth strata. The top of the 

 Gardiners Formation along this line is placed at -82 feet (-25 meters) 

 MSL from cores V-22, V-23, and V-24. Rampino's (1973) study of the land- 

 ward continuation of these borings revealed basically the same stratig- 

 raphy reported here except that he found evidence of a clay-silt stratum 

 (Wantagh Formation) between glacial outwash sands and overlying the 

 Gardiners Clay. He attributed this stratum to an interglacial period 

 of high sea level. His interpretation is supported by U.S. Geological 

 Survey (USGS) investigation of Pleistocene-Holocene stratigraphy in the 

 mid-Atlantic region. 



Seismic data and some CERC cores indicate that the shelf geology from 

 Fire Island Inlet east to Shinnecock Inlet is similar in structure and 

 stratigraphy to that described above; i.e.. Upper Cretaceous strata of 

 the Monmouth -Ma taw an Group exhibit some deformation and a truncated upper 

 surface. These strata are overlain by the Gardiners Clay and a relatively 

 thin overburden of late Pleistocene interglacial silts and sand and gravel 

 outwash detritus. Holocene back-barrier estuarine muds and marine sands 

 are also present. Exceptions to this geologic framework are shelf areas 

 where ancestral river channels have deeply eroded the Coastal Plain sur- 

 face and subsequently been filled with outwash sand and gravel. From 

 Shinnecock Inlet eastward to Montauk Point the Coastal Plain surface 

 becomes progressively deeper and covered by thicker Quaternary sediments, 

 analogous to the western Long Island shelf. The Coastal Plain surface is 

 more deeply eroded under the eastern Long Island shelf than in the central 

 Long Island shelf region for the same reasons that apply to the western 

 Long Island inner New York Bight shelf. Eight major north-south river 

 channels dissect the eastern mainland and shelf of Long Island and at 

 least six are present in western Long Island. This contrasts with the 

 central Long Island region where only two ancestral channels are identi- 

 fied. These channels are discussed later, but basically the higher 

 density of buried river channels found in western and eastern Long Island 

 provides explanation for the deeply eroded Coastal Plain surface and for 

 thicker accumulations of Pleistocene sediments. 



Pleistocene sediments were found to vary considerably in thickness 

 and lithology in the Long Island region. Because of similar lithologies 

 with both overlying Holocene sediments and underlying Cretaceous strata, 

 it is often difficult to accurately identify upper and lower Pleistocene 

 contacts from the seismic records or from the sediments in the cores. 

 Thus, the regional extent and abundance of definite Pleistocene sedi- 

 ments are uncertain. The most definitive evidence for the Cretaceous- 

 Pleistocene contact is an undulatory dark line on the seismic records 

 directly overlying southeast-dipping flat reflectors. Presence of 



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