island and continue south across the shelf to intersect the present Hudson 

 shelf channel. However, the connections with channels in the Sound have 

 apparently been obliterated by glacial erosion because contour patterns do not 

 match. Also, the unusual channel depths and reverse gradients to the north 

 are the result of massive glacial erosion as the terminus remained at the 

 Harbor Hill Moraine. 



In central parts of the Sound the bedrock surface is generally well below 

 the depth range of the sparker records; however, Grim, Drake, and Heirtzler 

 (1970) show a well-developed, characteristic glaciated east-west valley 

 paralleling the north shore of Long Island from Port Jefferson east to about 

 72°30' W. The sparker profiles show several tributary channels which trend 

 south, but it cannot be determined from existing data if the channels also 

 transect Long Island and continue south across the shelf to a possible 

 intersect with the Block shelf channel. 



The deep valley from the ancestral Quinnipac River that trends southwest 

 from New Haven Harbor with a thalweg of -224 meters has been described by 

 Haeni and Sanders (1974); the seismic records from this study show that it 

 continues past Milford and Bridgeport to the north of Stratford Shoal, then 

 changes to a more southerly orientation west of Stratford Shoal and probably 

 connects with the -213-meter valley (described by Grim, Drake, and Heirtzler, 

 1970) underlying the north shore of Long Island at Stony Brook near Crane Neck 

 (Fig. 11). The valley's southward continuation is not clearly defined, but 

 Williams (1976) theorized that it connects with a buried channel present on 

 the shelf 5.4 kilometers seaward of Moriches Inlet. The valley was certainly 

 a major drainage channel before Pleistocene time, and its depth and width in 

 the Sound rival the Hudson River fjord and make it by far the largest buried 

 channel extension of the present rivers in Connecticut. 



The last bedrock channel of major significance is the buried extension of 

 the Connecticut River which trends southeast from the present mouth toward 

 Orient Point on Long Island. Sparker profiles several kilometers seaward of 

 the river mouth show that the channel has a broad and open base with a thalweg 

 of -78 meters (which is remarkably shallow), suggesting that glacial scour was 

 not as pervasive as in other parts of the Sound. The channel continues south 

 under Orient Point where glacial erosion has produced thalwegs of -152 meters 

 and the channel has been filled with Lake Flushing varve sediments (Fig. 7). 



2. Surface and Subbottom Sediment Character and Distribution . 



The lithologic character of the sedimentary deposits in Long Island Sound 

 to the maximum core recovery depth of 5 meters was determined by both macro- 

 scopic and microscopic examination of samples from the 80 cores shown in 

 Figure 13. Information on areas where cores were not taken was derived from 

 extrapolation of the core data, using the CERC acoustic profiles, and from 

 literature sources. 



Based on these analyses the surface and subbottom sediments have been 

 classified, primarily by grain-size texture using mean grain diameter and 



32 



