Table 4. Carbon-14 dates from CERC Long Island vibratory cores. 



Core 



Location 



Depth to top 

 (feet) 



of peat (MSL) 

 (meters) 



Coordinates 



Age in years (B.P.) 



1 



Plum Island 



-50.0 



(-15.15) 



41°09'N.72°ll'W. 



8,120 ±125 



and 

 8,665 ± 145 













2 



Gardiners Bay 



-39.8 



(-12.0) 



41°04'N. 72°13'W. 



6,575 ± 125 



14 



Block Island Sound 



-52.5 



(-15.9) 



41°05'N. 72°02'W. 



5,600 ± 180 



39 



Moriches Inlet 



-36.0 



(-10.9) 



40°45'N.72°47'W. 



5,585 ±110 



67 



Fire Island 



-61.0 



(-18.5) 



40°40'N. 73°00'W. 



7,750 ± 125 



73 



Moriches Inlet 



-54.0 



(-16.36) 



40°45'N.72°45'W. 



7,585 ± 125 



1. Shown in Figures 2 and 24. 



2.5 feet (0.8 meter) is silty type III sediment. Core 67 off central Fire 

 Island contains one-half foot of mud over about 9 feet of sand. Type V 

 sediment underlies the sand down to 13 feet (4 meters) and includes a 

 small layer of peat which was dated at 7,750 ±125 years B.P. (Kumar, 1973; 

 Sanders and Kumar, 1975). Four feet of silty type III sediment completes 

 the bottom of the core. In Gardiners Bay, core 1 contains 2.5 feet of 

 type V sediment at the core bottom with a 1-foot-thick peat layer dated 

 at 8,665 ±145 years B.P. and 8,120 ±125 years B.P. (Caldwell and Sanders, 

 1973). Core 2 contains almost 7 feet of type V sediment, including about 

 2 feet of peat dated at 6,575 ±125 years B.P., overlying 4 feet of medium 

 to coarse sand. In Block Island Sound, core 14 contains 4.5 feet (1.4 

 meters) of organic-rich type V sediment with 7.5 feet (2.3 meters) of 

 medium to coarse sand on top and 1 foot of type III sediment underneath. 

 The organic content in the mud was dated at 5,600 ±180 years B.P. 



Since 1949, radiocarbon dating techniques have been widely accepted 

 as a liseful tool in determining approximate ages of organic material. 

 These methods give reasonably accurate ages when compared with tree- ring 

 dating, except for organic materials older than 30 to 40 thousand years 

 B.P. because the short half- life of C^'* limits detection beyond these 

 cutoff dates. Carbon-14 dating methods have greatly expanded man's 

 knowledge of history and are used in this study to gather clues to the 

 history of eustatic sea level rise and sedimentation during the past 

 several thousand years; this submergence has had profound effects on the 

 Long Island shelf and coastal geology. Based on the assumption that the 

 peat material dated once lived at or near the sea- land intersection and 

 that insignificant compaction of the underlying sediment has taken place, 

 it is possible to plot these dates and to construct a curve showing the 

 relative rate and magnitude of sea level rise. Figure 25 is a plot of 

 the seven dates from this study (Table 4) shown in relation to sea level 

 curves for Cape Cod, New Jersey, and lona Island. Dates for both Cape 

 Cod and lona Island are considerably younger and beyond the scope of this 

 data; however, two dates from New Jersey extend the curve past 6,000 years 

 B.P. and into the realm of dates from this report. The best-fit curve for 



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