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 2, which is one of 18 similarly-sized quadrangles that comprise the 3,700 square kilometer (km2) SBNMS region. The seabed of the SBNMS region is a glaciated terrain that is topographically and texturally diverse. Mapping of quadrangle 2 shows the distribution of substrates across the southwestern part of Stellwagen Bank, in Stellwagen Basin to the west and southwest of the bank, in Little Stellwagen Basin, and in the western part of Race Point Channel to the south of the bank. Water depths range from ~19 m on the bank crest to ~64 m in Stellwagen Basin. The previously unpublished data provided in this data release in conjunction with previously published bathymetric and seabed backscatter imagery, photographs, video, and grain-size analyses for quadrangle 2 are the foundation for Scientific Investigations Map 3530 (Valentine and Cross, 2024), 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 2 interpretations, data from 733 ground validation stations were analyzed, including 656 sediment samples. The seabed geology of quadrangle 2 comprises 19 substrate types ranging from boulder ridges to mobile and rippled sand to mud. Not all of these substrates are mappable as individual polygons. 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 3530 portrays the major geological elements (substrates, topographic features, processes) of environments within quadrangle 2. 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.

This field activity is part of the effort to map geologic substrates of the Stellwagen Bank National Marine Sanctuary region off Boston, Massachusetts. The overall goal is to develop high-resolution (1:25,000) interpretive maps, based on multibeam sonar data and seabed sampling, showing surficial geology and seabed sediment dynamics. This cruise was conducted in collaboration with the Stellwagen Bank National Marine Sanctuary, and the data collected will aid research on the ecology of fish and invertebrate species that inhabit the region. The Sanctuary's research vessel, R/V Auk, visited 19 locations on Stellwagen Bank at which a customized Van Veen grab sampler (SEABOSS) equipped with a video camera and a CTD was deployed in drift mode to collect sediment for grain-size analysis, video imagery of the seabed, and measurements of water column properties.