Sidescan Sonar Imagery and Surficial Geologic Interpretation
of the Sea Floor off Branford, Connecticut

a83-220interp - Subbottom profile from north-central Long Island Sound near Branford Reef (Needell and others, 1987). Profile location is shown on the bathymetric map elsewhere in this report. Interpretation of the profile shows the bedrock surface and the overlying glacial and marine units. Gas at the boundary of the glacial and marine units obscures much of the record.

a83-222interp - Subbottom profile from north-central Long Island Sound across Townshend Ledge (Needell and others, 1987). Profile location is shown on the bathymetric map elsewhere in this report. Interpretation of the profile shows the bedrock surface and the overlying glacial and marine units. Glacial drift crops out at the sea floor and comprises Townshend Ledge.

bathymap - Bathymetric map of the Branford, Connecticut study area. Depths are in meters and are adjusted to mean lower low water. Locations of seismic-reflection profiles 20 and 22, sample stations, and detailed images of the sidescan sonar mosaic presented elsewhere in this report are indicated. To view the detailed sidescan sonar images, select the desired area from the map above.

deposition - Bottom photograph showing an example of a sedimentary environment characterized by deposition. Note the muddy sediment and abundant polychaete and amphipod tubes. Bottom photo is from Niantic Bay in Long Island Sound (Poppe and others, 2000c).

environments - Map showing the distribution of sea-floor sedimentary environments off Branford, Connecticut. These environments include: erosion or nondeposition, sorting or reworking, and deposition.

erosion - Bottom photograph showing an example of a sedimentary environment characterized by erosion or nondeposition. Note the gravelly sediment and sessile fauna. Bottom photo is from Niantic Bay in Long Island Sound (Poppe and others, 2000c).

fishinga - Clam trawler at sea in north-central Long Island Sound.

fishingc - Lobster boat pulling traps in Long Island Sound.

fishingd - Clam trawler BIVALVE at sea in north-central Long Island Sound.

furrows1 - Perspective view of an idealized sedimentary furrow in the muddy cohesive sediments of north-central Long Island Sound. Figure shows the linear depression with gently sloping walls, longitudinal ripples, bioturbation, and nucula shells.

furrows2 - Schematic representation showing two possible mechanisms (modified from Flood (1983) and McLean (1981), respectively) for the formation of sedimentary furrows in north-central Long Island Sound. (A) Secondary helical flow patterns sweep coarse material, such as nucula shells or sand, into linear zones of convergence. These relatively coarse particles are driven by tidal currents and cut furrows into soft, cohesive sediments. (B) Turbulent wakes produced by flow around dredge-spoil disposal mounds or other obstacles on the sea floor may also initiate furrow development. Sand grains eroded from the mounds then abrade the lengthening furrows into the soft seabed.

interpret - Interpretation of the sidescan sonar mosaic (NOAA survey H11043) off Branford, Connecticut. The different patterns are features that are defined in the explanation and discussed in the text.

mosaic - Sidescan sonar mosaic of the sea floor off Branford, Connecticut (NOAA survey H11043). Light tones on the image represent areas of relatively high backscatter (typically coarser grained sediments); dark tones represent areas of relatively low backscatter (typically finer grained sediments).

nucula - Nucula SPP, locally known as Nutclams, range up to 6 mm long and are common in muddy bottom sediments within Long Island Sound.

sampling - Image shows USGS and Connecticut DEP scientists deploying a modified Van Veen grab sampler in Long Island Sound. This sampler is equipped with both still and video cameras.

sediment - Distribution of surficial sediments off Branford, Connecticut. Interpretation of the sediment distribution is based on data from sampling stations (sample locations are shown on the bathymetric map elsewhere in this report), on tonal changes in backscatter on the sidescan sonar image, and on correlation of the textural and backscatter data with the bathymetry.

shellbed - Bottom photograph shows an example of a shell bed providing shelter for a juvenile skate. Bottom photo is from Niantic Bay in Long Island Sound (Poppe and others, 2000c).

shepfig - Sediment classification scheme from Shepard (1954) as modified by Schlee (1973).

sortrewk - Bottom photograph showing an example of a sedimentary environment characterized by sorting or reworking. Note the sandy muddy sediment and abundant shell debris. Bottom photo is from Niantic Bay in Long Island Sound (Poppe and others, 2000c).

ssanoise - Detailed view of small-scale acoustic noise in the sidescan sonar mosaic from the Branford, Connecticut study area. Noise may be related to water-column events or geometric effects related to the sidescan sonar's angle of incidence with the sea floor.

sssfurrows - Detailed view of sedimentary furrows in the sidescan sonar mosaic from the Branford, Connecticut study area. "Tuning fork" joining pattern exhibited by some of the furrows typically open to the east (right) suggesting net westward transport. Location of this view is shown in the bathymetric figure; distribution of sedimentary furrows on the mosaic is shown in the interpretation figure.

ssshclamtrawls - Detailed view of trawl marks in the sidescan sonar mosaic from the Branford, Connecticut study area. Looped curvilinear trawl marks result from commercial hard-clam fishing. Location of this view is shown in the bathymetric figure.

ssslowbarcs - Detailed view of the low backscatter arcuate bands observed in the sidescan sonar mosaic from the Branford, Connecticut study area. Location of this view is shown in the bathymetric figure.

sssspoils - Detailed view of dredge-spoil mounds in the sidescan sonar mosaic from the Branford, Connecticut study area. Note the association of a sedimentary furrow with a dredge spoil mound. The extension of furrows on the right off both the east and west sides of the dredge spoil is evidence for the oscillatory nature of the tidal currents. Location of this view is shown in the bathymetric figure.

ssstownshend - Detailed view of Townshend Ledge in the sidescan sonar mosaic from the Branford, Connecticut study area. This rocky feature is an outcrop of the Madison moraine. Location of this view is shown in the bathymetric figure.

ssstrawlmarks - Detailed view of trawl marks in the sidescan sonar mosaic from the Branford, Connecticut study area. Location of this view is shown in the bathymetric figure; distribution of trawl marks on the mosaic is shown in the interpretation figure.

studylocationmap - Map showing location of the Branford, Connecticut study area (red polygon). Also shown are major onshore moraines, and the sites of other interpreted sidescan sonar surveys in Long Island Sound: Norwalk -- Twichell and others (1997); Milford -- Twichell and others (1998); New Haven Harbor and New Haven Dumping Grounds -- Poppe and others (2001); Roanoke Point -- Poppe and others (1999a); Falkner Island -- Poppe and others (1999b); Hammonasset -- Poppe and others (1997); Niantic Bay -- Poppe and others (1998a); New London -- Poppe and others (1992), Moffett and others (1994), Zajac and others (2000, 2003); Fishers Island Sound -- Poppe and others (1998b). NOAA sidescan sonar survey H11044, shown by a dashed line, has not yet been interpreted.

towfish - Edgetech (EG&G) 272T sidescan sonar tow fish used aboard the RUDE for data acquisition during NOAA survey H11043.

waveyf - Detailed view of "wavy" sedimentary furrows in the sidescan sonar mosaic from the Branford, Connecticut study area. Sinuous character of these furrows is related to an irregular ship's track.