| Description |
The U.S. Geological Survey (USGS), in cooperation with the National Marine Sanctuary Program of the National Oceanic and Atmospheric Administration (NOAA), has conducted seabed mapping and related research in the Stellwagen Bank National Marine Sanctuary (SBNMS) region since 1993. The interpretive datasets and source information presented here are for quadrangle 3, which is one of 18 similarly-sized quadrangles that comprise the 3,700 square kilometer (km2) SBNMS region. The seabed of SBNMS is a glaciated terrain that is topographically and texturally diverse. Mapping of quadrangle 3 shows the distribution of substrates on the southeastern part of Stellwagen Bank, on adjacent banks and basins in deeper water to the east, in the eastern part of Race Point Channel to the south of the bank, and on the northern slope of Outer Cape Cod. Water depths range from ~25 m on the bank crest to ~135 m east of South Ninety Bank which lies off the eastern margin of Stellwagen Bank. The data presented here for quadrangle 3 are the foundation for Scientific Investigations Map 3544 (Valentine and Cross, 2026), which presents maps of seabed topography, ruggedness, backscatter intensity, distribution of geologic substrates, sediment mobility, distribution of fine- and coarse-grained sand, and substrate mud content. For the quadrangle 3 interpretation, data from 309 ground validation stations were analyzed, including 279 sediment samples. The geologic substrate maps of quadrangle 3 show the distribution of 21 substrates that represent a wide range of textures, such as rippled sand, immobile sand, immobile muddy sand, sand that partially veneers gravel, and boulder ridges. Not all of these substrates can be mapped as individual polygons as some scattered deposits are not coherent units mappable at the given scale. Substrate types are defined or inferred by sediment grain-size composition, surface morphology, sediment layering, the mobility or immobility of substrate surfaces, and water depth range. Scientific Investigations Map 3544 portrays the major geological elements (substrates, topographic features, processes) of environments within quadrangle 3. It is intended to be a basis for the study of sediment transport processes that affect a shallow, offshore bank and adjacent basins, for the study of the ecological requirements of invertebrate and vertebrate species that use these substrates, and to support seabed management in the region. [More]
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