UNCLASSIFIED 



SECURITY CLASSIFICATION OF THIS PAGEfHTian Data Bntend) 



The subbottom consists of igneous and metamorphic bedrock that crops out 

 close to the Connecticut shore and slopes south to depths of -250 meters at 

 the Long Island north shore. The bedrock surface under the Sound is highly 

 irregular and exhibits relief on the order of ±30 meters. There are numerous 

 buried river channels that generally trend north-south in the western Sound, 

 and apparently project south under Long Island; a large east-west channel 

 along the Long Island north shore that underlies eastern Long Island and 

 Gardiners Bay, projects south to possibly join the Block Island Shelf channel. 

 Many channels, deeply scoured by Pleistocene glaciers, project south from 

 present-day rivers along the Connecticut shore. The deepest channel at -244 

 meters MSL underlies New Haven Harbor and trends southwest past a bedrock high 

 at Stratford Shoal and then projects south under the Long Island mainland. 



Cretaceous strata overlie the bedrock in isolated areas of the middle of 

 the Sound and exhibit considerable surface relief due to erosion by multiple 

 glacial advances. Pleistocene sediments consist of thick accumulations of 

 very firm varvelike silts and clays filling and overlying the bedrock surface 

 throughout much of the central Sound, as well as moderately to poorly sorted 

 sands and gravels up to boulder size that were placed as discontinuous reces- 

 sional moraine segments, glacial outwash heads, and fluvial deltas. The pres- 

 ence of these glacial depositlonal features on the seabed from the western end 

 of the Sound to about the Connecticut River longitude is evidence for one or 

 more readvances of the late Wisconsin glacier subsequent to deposition of the 

 Harbor Hill Moraine rimming the Long Island north shore. 



Holocene sediments consist primarily of organic sandy muds that are 

 accumulating in low energy environments. The primary sources of these fine- 

 grained materials are coastal erosion of glacial debris, riverine inputs, and 

 landward transport of fines from adjacent Block Island Sound and the inner 

 shelf. 



Fourteen isolated shoal features have been identified as offering the 

 highest potential as sources of beach-fill sand and construction aggregate. 

 Based on available data, a conservative estimate is that 189 million cubic 

 meters of sand and gravel is available in water depths not exceeding 20 meters 

 if the latest dredging technology were used. 



UNCLASSIFIED 



SECURITY CLASSIFICATION OF THIS PAGEfHfien Data Entered) 



