The major bathymetric trends and features from the NOS maps with seven 

 selected profile locations are shown in Figure 4; the cross-sectional pro- 

 files across the Sound are illustrated in Figure 5. Based on bathymetry, the 

 Sound is divided into five major basins separated by shoals that have 

 considerable relief. 



The western basin (profile A in Fig. 5) is rather narrow and water depths 

 to 27 meters are common in the center but greater depths are present in small 

 depressions. The central part of the Sound is composed of three basins with 

 Cable and Anchor Reef, Stratford Shoal, and Six Mile Reef acting as the bound- 

 ing shoals. Depths in the central basins usually do not exceed 30 meters, but 

 some holes on the Long Island side extend to -46 meters. The eastern basin 

 (profiles F and G in Fig. 5) has considerably more relief, and depths in the 

 elongate troughs may exceed 91 meters, such as "The Race" in profile G. 



7. Previous Geologic Investigations . 



Long Island Sound is probably one of the most studied areas in the United 

 States. Dana (1890) was one of the first to speculate that based on land sur- 

 face morphology and depth contours the ancient "Sound River" flowed eastward 

 toward Block Island Sound and was responsible for eroding the trough that 

 became Long Island Sound when sea level rose to its present position. How- 

 ever, Veatch (1906) judged that the Sound River flowed west rather than east 

 and breached western Long Island to join the sea. Fuller's (1914) study of 

 the glacial deposits on Long Island gave support to Dana's eastward-flow 

 theory for the Sound River but he believed that the major erosion took place 

 in late Tertiary or early Pleistocene time, and that much of the present 

 morphology of the Sound was the result of glacial erosion and depositional 

 processes during late Wisconsin time. Fleming's (1935) study of central Long 

 Island and its glacial geology pointed out that the Ronkonkana and Harbor Hill 

 Moraines are composed mostly of stratified ice contact or glaciof luvial sand 

 and gravel rather than till deposited directly at the glacier terminus. 



Investigation of the Sound continued with studies of the surface deposits 

 on Long Island and Connecticut; however, in the 1950' s new geophysical equip- 

 ment was developed that allowed researchers to survey the Sound and look at 

 the subbottom to give a third dimension to its geologic character. Oliver and 

 Drake (1951) were about the first to use seismic refraction data to show that 

 a very uneven bedrock surface underlies the Sound and is covered with glacial- 

 age unconsolidated sediments. They were unable to identify Cretaceous strata 

 in the Sound that were known to form the core of the Long Island mainland. 



Ellis (1962), in a detailed study of the sediments and geologic history of 

 the Norwalk Islands between Stamford and Bridgeport, Connecticut, stated that 

 the island chain was underlain by bedrock but that glacial till from a termi- 

 nal moraine younger than the Harbor Hill formed most of the islands' relief. 



Upson and Spencer ( 1964) used deep boring logs from bridge foundation 

 projects to describe the subbottom configuration and fill sediments of the 

 ancestral channels of the Housatonic, Quinnipiac, and Thames Rivers that dis- 

 charge into Long Island Sound. They found that all the valleys were eroded by 

 glacial processes to bedrock and subsequently nearly filled with a sequence of 

 glacial till, outwash sand and gravel, and estuarine silt and clay. Sanders 

 (1965) and Haeni and Sanders (1974) used well boring logs and continuous 



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