Table 3. Log of the Orient Point, Long Island boring. 



Boring interval "^ 

 (feet) 



Description 



0to41 



41 to 146 



Medium dense to dense, yellow-brown sandy gravel. Poorly sorted. Individual sand grains are angular to 

 subangular and gravel materials are rounded to subrounded. 



Very dense micaceous, silty, fine sand becoming finer with depth grading into a micaceous, fine sandy silt 

 at -70 feet. 



Very stiff, brovm sUty clay interfingered with layers of clayey silt and occasional fine sand partings. The 

 upper part consists of equal amounts of clay and silt in 1/8- to 1/2-inch layer thicknesses. Lower part 

 contains more clay layers than silt and is up to 2 inches thick. Mass property tests indicate that these clays 

 have been preconsolidated in the past under loads greater than presently exist. 



1. Data from Woodward-Clyde-Sherard and Associates (1965). (See Figure 2 for location.) 



2. Surface elevation at boring is approximately +20 feet (Mr. Henry Miller, 



Alpine Geophysical Associates, Incorporated, personal communication, 1973). 



continues to the channel floor or whether the varves overlie Coastal 

 Plain strata or older glacial materials. Existence o£ varve deposits at 

 the Orient Point location is consistent with other occurrences of fine- 

 grain sands and muds in CERC cores from the Gardiners Bay-Napeague Harbor- 

 Peconic Bay region of eastern Long Island. Such a broad occurrence of 

 these sediments supports the hypothesis that a large freshwater lake 

 occupied this region during Pleistocene time. Frankel and Thomas (1966) 

 found evidence of lacustrine sediments in the Fishers Island region east 

 of Long Island which appear to correlate with the lake deposits reported 

 here and by Coch (1974). Varve strata in the Orient Point CJiannel (Fig. 6) 

 show some evidence of deformation but no scour on the seismic records is 

 evident. Therefore, the lake must have postdated the glacial advance 

 responsible for the Ronkonkoma Moraine. Since this moraine is thought 

 to be of Wisconsin age by most workers, the lacustrine phase is inferred 

 to be late Wisconsin in age intermediate between times of the Ronkonkoma 

 advance and the Harbor Hill advance. 



d. Holocene Sediments . The fourth stratigraphic unit recognizable 

 from the cores and geophysical records is Holocene sediment. Definitive 

 recognition of these materials is difficult because they closely resemble, 

 and many times are derived from underlying Pleistocene or Cretaceous- 

 Tertiary strata. Holocene stratigraphy is best identified on the seismic 

 records when the acoustic returns are good quality and the records show a 

 complete sequence of southeast-dipping Coastal Plain strata, overlain by 

 flat-lying or slightly dipping Pleistocene strata, which often exhibit an 

 irregular upper surface, and then thin evenly bedded Holocene strata on 

 top. The most definitive proof for the presence of Holocene sediments is 

 the radiometric carbon- 14 (C^**) dates for cores 39, 67, and 73 off Fire 

 Island and cores 1, 2, and 14 in the Gardiners Bay-Napeague Harbor area 

 of eastern Long Island. The thickness and distribution of Holocene sedi- 

 ment vary considerably depending on present and past environmental history 

 and sea floor morphology. CERC cores indicate that Holocene sediments are 

 most abundant (or most easily recognized) in the shelf region between Fire 

 Island Inlet and Shinnecock Inlet. Many cores in that shelf area exhibit 



38 



