Side-Scan Sonar Investigation of Shallow-Water Depositional Processes In and Around Block Island Sound: Before and After the Nor'easter of 1992,
LAMONT-DOHERTY GEOLOGICAL OBSERVATORY PALISADES NY
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Using side-scan and sub-bottom sonar, we surveyed portions of Block Island Sound before and after the occurrence of a number of large storms to determine how storm events modify the distribution and type of bedforms, sedimentary facies, and acoustic backscatter of shelf sediments. Our analysis of the data suggest that the passage of these large storms did not significantly modify the existing sedimentary bedforms or the large-scale acoustic backscatter patterns observed in Block Island Sound. One explanation for this surprising observation is that the submerged portion of the Ronkonkoma glacial moraine, which extends from Montauk Point at the tip of Long Island to Block Island and continues northward to Point Judith, Rhode Island, acts as a natural jetty at the mouth of Block Island Sound, dissipating much of the storms wave energy. Correlation of sub-bottom and side-scan sonar data in conjunction with surficial sediment type indicates that the physiography and subsurface geology F generated during the last glaciation and deglaciation strongly influences the present-day sediment transport, erosion, and deposition in Block Island Sound. Although there are no significant large-scale changes observed between 1991 and 1994, numerous smaller-scale changes are observed.
- Physical and Dynamic Oceanography
- Acoustic Detection and Detectors