Table 5. Characteristics of sand and gravel deposits. 



Designation 



Core No. 



Water depths 

 (■) 



Thickness 

 (<■) 



Mean grain size 

 (mm) 



Est. volume 

 (million a 3 ) 



Re-arks 



A 



31 



11 to 14 



2.7 



0.25 to 0.27 



1 



Deposit consists of two Irregular 

 ridges off Matinlcock Point 



B 



36 



8 to 18 



4.3 



0.60 to 0.90 



6 



Shoal about 6.4 km S. of Stamford Is 

 glacial till on a bedrock high 



C 



7A 



7 to 18 



3.1 



0.50 to 1.20 



4 



Cable and Anchor Beef S. of 

 Norwalk Islands Is glacioflu- 

 vlal sediment on a bedrock high 



D 



26, 26B, 

 38 



6 to 18 



2.7 



0.34 to 1.10 



7 



Shoal off Eatons Neck is composed 

 of Pleistocene sands 



E 



9 



12 to 20 



3.9 



0.28 to 0.62 



4 



Shoal about 5 km SE. of Norwalk 

 Islands consists of steeply 

 dipping forset strata 



F 



12 to 15, 



49, 53A, 



54 



6 to 12 



3.9 



0.25 to 1.00 



37 



Shoal off Bridgeport Is a glaclo- 

 fluvlal delta with steeply dipping 

 forset strata 



C 



21 



6 to 15 



3.3 



0.61 to 0.89 



5 



Shoal off Crane Neck Is composed 

 of Pleistocene sands 



H 



78 



6 to 15 



2.7 



0.31 to 1.10 



5 



Deposit consists of glaclof luvlal 

 sands 



I 



57 



8 to 9 



3.7 



0.47 to 0.99 



10 



Shoal S. of Milford overlies the 

 buried ancestral Quinnlplac River 

 channel 



J 



76 



6 to 17 



3.5 



0.43 to 0.48 



7 



Shoal is well stratified with forset 

 strata 



K 



58A 



6 to 9 



2.1 



_______ 



3 



Townshend Ledge Is composed of 

 glaclof luvlal sediment on a 

 bedrock high 



L 



75 



6 to 18 



3.8 



0.40 to 0.65 



40 



Shoal has forset strata pro- 

 grading west 



H 



72, 74 



6 to 17 



2.7 



0.34 to 0.79 



54 



Shoal consists of Pleistocene 

 glaclof luvlal sands; sand waves 

 with 5-m relief are present 



N 



64 to 67A 



2 to 6 



2.7 



0.43 to 0.84 



6 



Long Sand Shoal is composed of 

 stratified glaciofluvlal and 

 estuarlne sands overlying bedrock 



'Data unknown. 



Point on the Long Island north shore (Fig. 17). The reduction of seismic line 

 1 shown in Figure 18 shows the morphology of the shoals and the undulatory 

 character of the bedrock as well as the position of core 31 taken on top of 

 the nearshore shoal. Core 31 contains almost entirely medium grain-size 

 quartz sand. The character of the seismic profiles suggests that the shoals 

 are composed of sandy material and probably have a similar origin. Using a 

 sand thickness of 2.7 meters, the calculated sand volumes for the nearshore 

 shoal and the offshore shoal are 642 and 367 thousand cubic meters, respec- 

 tively. These volumes may be quite conservative as seismic line 1 (Fig. 18) 

 shows that the nearshore shoal is a maximum of 6 meters thick, and that the 

 offshore shoal is about 4.6 meters thick. 



b. Area B . Area B is an isolated shoal (Fig. 17) situated immediately 

 south of Stamford Harbor and to the west of a designated dumping ground for 

 dredge material. The shoal rises to within 7.9 meters of the water surface 

 but its base lies in water depths of about 21 meters on three sides and 

 slightly more than 30.5 meters to the north. The seismic data suggest that 

 the shoal is composed of sedimentary material perched on a bedrock high; core 



39 



