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High-Resolution Quaternary Seismic Stratigraphy, New York Bight Continental Shelf, OFR 02-152
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Quaternary Sedimentary Deposit

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Pleistocene Channel-Fill Units
Two prominent channels incise the coastal-plain strata. One channel trends sub-parallel to the south shore of Long Island and extends from under Jamaica Bay to the eastern limit of the study area (Figs. 6 and 12). This channel is filled with up to ~55 m of acoustically amorphous Quaternary sediment (Fig. 10).

Seismic-reflection profile showing possible fault within the Hudson Shelf Valley. Also link to larger image.
Figure 13. Seismic-reflection profile showing possible fault within the Hudson Shelf Valley.
Seismic-reflection profilee showing Coastal Plain Unconformity and overlying Quaternary deposits. Also link to larger image.
Figure 12. Seismic-reflection profilee showing Coastal Plain Unconformity & overlying Quaternary deposits. Also link to larger image.
A second major channel incises the coastal-plain strata in the Hudson Shelf Valley area (Fig. 13), and forms the oldest of a complex of at least three (possibly four) smaller cut-and-fill channels (Fig. 14).
Seismic-reflection profilee showing Pleistocene channels within Hudson Shelf Valley. Also link to larger image.
Figure 14. Seismic-reflection profilee showing Pleistocene channels within Hudson Shelf Valley. Also link to larger image.
These smaller channels are informally designated as Hudson channels R5, R6, and R7 (Figs. 6, 15, and 16) with increasing depth in the section (Lotto, 2000). Channel R7, and in places R6 and R5, incise coastal-plain strata. The thalweg of Hudson channel R6 is marked by a series of saddles and depressions that closely follow the trend of the modern Hudson Shelf Valley (Fig. 15). The surface of channel R5 (Fig. 16) has been traced south of the study area along the modern Hudson Shelf Valley to latitude 40º00' N (Allison and others, 1997).
Map showing depth of Hudson Channel R6 below sea level. Also link to larger image.
Figure 15. Map showing depth of Hudson Channel R6 below sea level. Also link to larger image.
An additional internal reflector, informally designated as reflector R4 (Lotto , 2000), also has the geometric configuration of a shallow, small incised channel in the area of Hudson Shelf Valley (Fig. 14). However, reflector R4 can be distinguished on CHIRP subbottom profilees only in a small area due to its relatively low amplitude. Due to its limited spatial extent, we have not interpreted reflector R4 as a paleo-Hudson channel.

Pleistocene sedimentary deposits that fill the smaller Hudson channels are informally designated as Hudson Channel-Fill Units (CFUs) CFU5, CFU6, and CFU7 respectively (Lotto, 2000). CFU7 is acoustically amorphous and difficult to distinguish due to acoustic blanking from the overlying gassy sediment of unit CFU5 (Fig. 14). CFU7 pinches out to the north. CFU6 (Fig. 14) crops out as a narrow belt on the west wall of the modern Hudson Shelf Valley from latitude 40º7'N to 40º10'N,(Allison and others, 1997). South of 40º15', clinoform strata of CFU6 fill the upper part of channel R6 from the east (Fig. 15). Channel R5, the floor of which is conformable to the bedding of CFU6 on
Map showing depth to Hudson channel R5 below sea level. Also link to larger image.
Figure 16. Map showing depth to Hudson channel R5 below sea level. Also link to larger image.
its western flank and unconformable on its eastern flank, has truncated much of CFU6. CFU5 is gas-charged sediment (Fig. 14) and crops out in isolated areas within the Hudson Shelf Valley from latitude 40º15'N to 40º18'N (Fig. 4). CFU5 exhibits westward-prograding clinoform fill south of 40º14'N and eastward-prograding clinoform fill north of the same latitude (Fig. 16).
Pleistocene Shelf Sedimentary Deposit 
The Pleistocene sedimentary deposit is not restricted to the CFUs, but extends across much of the study area (Fig. 8). The upper section of the Pleistocene deposit is extensively incised by additional cut-and-fill channels that trend generally north to south from southern Long Island (Fig. 17). These laterally discontinuous cut-and-fill channels are interpreted to be glaciofluvial features (Lotto, 2000), similar to those described immediately east of the study area along the inner continental shelf (Foster and others, 1999; Schwab and others, 1999, 2000b).
Seismic-reflection profile showing Holocene ravinement surface. Also link to larger image.
Figure 17. Seismic-reflection profile showing Holocene ravinement surface. Also link to larger image.


In the nearshore area off Long Beach, sandy gravel and gravelly sand exposed on the seabed are interpreted by Schwab and others (2000a) to be reworked Pleistocene glaciofluvial sediments (Fig. 4). Sidescan-sonar images in the area reveal a series of sharply defined, linear, high-backscatter features, perpendicular or slightly oblique to the shoreline (Fig. 2a). These backscatter features are interpreted to represent a series of low-amplitude, transverse bedforms, in which gravelly sand forms the high-backscatter lineations and fine sand produces the low backscatter (Duane and others, 1972; Schwab and others 1997a, 1997b, 2000). Where buried by Holocene sediment, the upper surface of the Pleistocene sedimentary deposit is truncated by a relatively horizontal regional unconformity, known as the Holocene ravinement surface (Fig. 7).

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