Comprehensive Geologic Mapping of the Inner Continental Shelf off the Delmarva Peninsula

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The USGS has collected new geophysical data, seafloor grab samples, and video footage from the inner continental shelf off the Delmarva Peninsula as well as acquired and optimized NOAA and BOEM data.

This article is part of the June-July 2017 issue of the Sound Waves newsletter.

The USGS has collected about 10,000 kilometers of new geophysical data and 258 seafloor grab samples along with video footage at more than 200 bottom video stations to portray the geology and seafloor characteristics on the inner continental shelf off the Delmarva Peninsula.

Additionally, the USGS has acquired and repurposed existing NOAA hydrographic data and Bureau of Ocean Energy Management (BOEM) Wind Energy Area geophysical data to optimize the design of this extensive survey to produce one of the most data-rich and aerially extensive (about 5,100 square kilometers) inner continental shelf studies on the U.S. Atlantic Coast.

Map shows survey lines of the inner continental shelf of the Delmarva Peninsula in green, and data from partners in blue

The USGS conducted surveys on the inner continental shelf of the Delmarva Peninsula (shown in green) to complement related datasets previously collected in the area by partners NOAA and BOEM. The inset map shows location of the study area. Image credit: USGS.

Map of the NE US coast showing several types of data collected by NOAA and the USGS, with explanatory insets

Hill-shaded bathymetric, backscatter, and photographic data collected by NOAA and the USGS. Backscatter data give indications of seafloor character. In general, low-backscatter intensity (blue) corresponds to finer-grained material, whereas high-backscatter intensity (orange) corresponds to coarser substrate. Off the coast of Virginia, zones of low backscatter indicate a smoother, sandy sea floor (inset A), whereas zones of high backscatter often indicate a sea floor with abundant carbonate (shell hash) (inset B). Image credit: Laura Brothers, USGS.

The Delmarva Peninsula is a 220-kilometer-long headland, spit, and barrier-island complex located off the mid-Atlantic states of Delaware, Maryland, and Virginia that was substantially affected by Hurricane Sandy. In response to Hurricane Sandy, the U.S. Department of the Interior funded an initiative to define the geologic framework of the Delmarva inner continental shelf and its role in coastal-sediment flux and vulnerability through geophysical mapping of its offshore areas. The Delmarva project provides baseline datasets and derivative interpretive maps that offer a geospatial framework for scientific research and provide critical information to planners and decision-makers who oversee the management of resources and mitigation of hazards in the coastal ocean. Bathymetric data are critical for developing surge models, whereas sub-sea floor data inform structural and geologic understanding.

These data and mapping products are needed for:

  • Identifying sand and cultural resources;
  • Delineating benthic habitat;
  • Identifying shallow geohazards, such as natural gas and structurally weak sediment units;
  • Evaluating and selecting optimal sites for offshore infrastructure placement; and
  • Locating sites for offshore development and general marine planning.

These datasets will also contribute to improving our ability to identify coastal areas in the region that are most susceptible to effects of large storms and sea-level rise.  

High-Resolution Geophysical data releases:
https://doi.org/10.5066/F7MW2F60
https://doi.org/10.5066/F7P55KK3
https://doi.org/10.3133/ofr20141262

Read more about the Delmarva project at https://www.usgs.gov/centers/whcmsc/science/hurricane-sandy-response-linking-delmarva-peninsulas-geologic-framework.

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