New Hampshire and Vicinity Continental Shelf: Morphologic Features and Surficial Sediments
|Title||New Hampshire and Vicinity Continental Shelf: Morphologic Features and Surficial Sediments|
|Authors||Ward, LG, Vallee-Anziani, M, McAvoy, ZS|
|Volume||BOEM/New Hampshire Cooperative Agreement (Contract M14ACOOO10) Technical Report|
|Number of Pages||24|
|Organization Name||Bureau of Ocean Energy Management (BOEM) Marine Minerals Branch|
|Keywords||CMECS, continental shelf, Maps, New Hampshire, Surficial Geology|
The New Hampshire continental shelf is extremely heterogeneous and includes extensive bedrock outcrops, sand and gravel deposits, and muddy basins. Many of the depositional features are glacial in origin and have been significantly modified by marine processes as sea level fluctuated since the end of the last major glaciation. The apparent glacial deposits (e.g., drumlins) have been eroded, leaving very coarse lag deposits while supplying sand to develop wave-formed features (shoals). Many of these features have positive relief standing above the seafloor, lending evidence of their formation by waves and shallow water currents. Of particular interest is a large sand body that is ~3.2 km in length, ~1.3 km in width and has a maximum relief of ~7 m (in comparison to the surrounding seafloor). Some of these deposits may represent significant sand and gravel deposits on the New Hampshire continental shelf that have the potential for future use for beach nourishment and other efforts to build coastal resiliency.
Recent high resolution multibeam echosounder (MBES) bathymetric and backscatter surveys have revealed features of the New Hampshire shelf and vicinity seafloor in exceptional detail that has not been previously described. Synthesis of the MBES bathymetry and backscatter, coupled with an extensive archived database consisting of subbottom seismics, bottom sediment grain size data, and vibracores, was used to develop new surficial geology maps and significantly improve our knowledge of the character and origin of the major depositional features. The new surficial geology maps depict the exposed bedrock distribution, morphologic features, and sediment distribution. These maps are only the first step in developing high resolution and accurate surficial geology maps for the New Hampshire and vicinity continental shelf and need extensive field verification. However, they represent a major improvement over previous mapping efforts. When completed and verified, the surficial geology maps will be the most detailed ever published for the New Hampshire continental shelf.