an apparent major channel almost 10 miles (16.1 kilometers) offshore Fire 

 Island. This possible Huntington channel extension is shown to the west in 

 Figure 16 as a broad depression a minimum of 275 feet (84 meters) deep (the 

 maximum energy penetration for seismic line V) . Evidence that channel H 

 crosses central Fire Island is also supported by channellike depressions 

 in the Cretaceous surface shown in Figure 4, profile C. 



Channel I in central Long Island (Fig. 13) is based on analyses of 

 seismic reflection and magnetic data by Grim^ Drake, and Heirtzler (1970) 

 in Long Island Sound; Figure 12 in their study shows that a channel cut 

 into the pre-Tertiary surface north of Smithtown Bay exceeds 700 feet 

 (213.4 meters) in depth and appears to project southeast and decrease in 

 depth as the channel approaches the Long Island north shore. The over- 

 deepening of many of the channels north of the Harbor Hill Moraine is 

 attributed to repeated ice scour by Pleistocene glaciers. Channel I is 

 comparable in depth to the former Hudson fjord at Tarry town. New York, 

 which was scoured by glacial ice to -725 feet (-221 meters) MSL (Worzel 

 and Drake, 1959). The more shallow continuation of channel I across Long 

 Island to the coast (Fig. 13) is based on seismic evidence of a 205-foot 

 (62.5 meters) channel 3 miles seaward of Moriches Inlet, and also by 

 channellike depressions in Cretaceous strata in Figure 4, profile C. 

 The channel has an apparent reversed gradient because glacial scour was 

 limited to the north shore. 



A 40-mile-wide (64.4 kilometers) area (Fig. 13) in east-central Long 

 Island (73°20'W. to about 72°40'W.) has no major buried channels crossing 

 either the Long Island mainland or the Atlantic inner shelf. This lack of 

 channeling is explained by Grim, Drake, and Heirtzler (1970) in a contour 

 map of the pre-Tertiary surface under Long Island Sound which shows a 

 steep-sided east-west oriented buried channel reaching depths of -800 feet 

 (-244 meters) MSL north of this nonchanneled area. They commented on the 

 lack of continuity of pre-Tertiary contours between mainland Long Island 

 and the Sound in this area. Apparently, this deep east-west channel in 

 the Sound was a major drainage system before Pleistocene glaciation and 

 it effectively intersected any streams flowing south from New England 

 across the Sound and diverted their discharges east toward Block Island 

 Sound. Then, with the advent of continental glaciation, the channel was 

 overdeepened by ice scour as the main glacier body impinged on the Long 

 Island north shore. The position and orientation of this channel would 

 suggest that it was controlled by the Coastal Plain cuesta. 



The eastern Long Island shelf subbottom is extensively channeled 

 (Fig. 13). Two primary buried channels (J and K) appear to trend south- 

 southeast from Long Island Sound and have thalweg depths exceeding -500 

 feet (-152.4 meters) I4SL. These channels lie on the western margin of 

 the complex of buried channels shown by McMaster and Ashraf (19 73) to 

 underlie the southern New England shelf. Cross sections in Figure 6 

 of the Three Mile (J) and Orient Point (K) channels show they are cut 

 into bedrock and Coastal Plain strata and are filled with horizontal or 

 slightly undulatory more recent sedimentary strata. Clues to the vertical 



47 



