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Figure 7. (Top) sidescan-sonar imagery from the western part of the study area, (middle) in the area of seismic-reflection profile B-B' extending southeast to northwest, (bottom) with interpretation.

Figure 8. (Top) sidescan-sonar imagery associated with (middle) seismic-reflection profile C-C' and (bottom) interpretation.

Five historic seismic-reflection profiles cross the study area (Needell and others, 1983b; 1983c). Seismic-reflection data from the western and southern parts of the study area show horizontal to slightly dipping layered strata filling low areas in a unit of discontinuous reflectors (fig. 7). The layered strata, which coincide with a channel system, are interpreted to be fluvial and estuarine sediments (Needell and others, 1983b). The unit of discontinuous reflectors, which also covers the surface of the central part of the study area, is interpreted to be unstratified glacial drift (Needell and others, 1983b). The easternmost profile shows a unit of faintly stratified sediment overlying a unit of discontinuous reflectors (fig. 8). The stratified unit is interpreted to be composed of glaciolacustrine sediments, like those found east of the study area on the same bathymetric high (McMullen and others, 2008).