The U.S. Geological Survey (USGS)'s Woods Hole Science Center, in cooperation with the Massachusetts Office of Coastal Zone Management (CZM) and the National Oceanic and Atmospheric Administration (NOAA), is conducting geophysical surveys to characterize the bottom morphology, surficial-sediment distribution, and subsurface geology in the shallow coastal waters off Massachusetts.
The long-term goal of this mapping effort is to produce high-resolution geologic maps that will be used in aggregate-resource and benthic-habitat studies by State and other Federal agencies. USGS scientists Brad Butman and Ilya Buynevich are the principal investigators for this cooperative project.
Three nearshore survey areas between Boston and the Massachusetts-New Hampshire State line were initially identified by CZM for study. These survey areas, which are inshore of the Stellwagen Bank multibeam-echosounder survey conducted previously by the USGS, include Boston Harbor and approaches, the South Essex Ocean Sanctuary, and the Southern Merrimack Embayment.
Over the past several years, NOAA's National Ocean Service (NOS) has collected hydrographic sonar data (bathymetry and sidescan-sonar data) in the first survey area, Boston Harbor and approaches, as updates to nautical charts. These data will be reprocessed by USGS and CZM scientists for geologic interpretation. Seth Ackerman and Brad Butman are leading the data-processing and interpretive efforts for Boston Harbor.
The second survey area includes parts of the South Essex Ocean Sanctuary between Nahant and Cape Ann. Approximately 75 percent of this area was surveyed with interferometric sonar, seismic-reflection profiling, and sidescan sonar during a 3-week survey conducted last fall by USGS personnel Barry Irwin, Chuck Worley, Ilya Buynevich, Brian Andrews, Bill Danforth, Dave Foster, Dave Nichols, Tom O'Brien, and Jane Denny on the USGS research vessel Rafael.
The rest of the area will be surveyed in spring 2004, after which detailed ground-truth data, including grab samples, video footage, and still photographs, will be collected.
Last fall's South Essex Sanctuary Survey was designed to acquire 100-percent coverage of the sea floor with interferometric sonar, a swath-bathymetry system. Line spacing ranged from 100 to 150 m within 10- to 40-m water depths, with the closer line spacing in the shallower water.
All survey systemssidescan sonar, seismic-reflection profiler, and interferometric sonarwere run concurrently. Brian Andrews, a recently hired contractor for the USGS' Woods Hole Science Center, and Ilya Buynevich are leading the data-processing and interpretive efforts for this area.
The third survey area, the Southern Merrimack Embayment, is an inner-shelf region dominated by drumlins and riverine deposits. Multibeam-echosounder data will be collected from this area by a commercial hydrographic-survey company and analyzed by USGS staff.
Data from these three survey areas will eventually be combined with USGS databases from Stellwagen Bank National Marine Sanctuary, providing continuous high-resolution sea-floor coverage for most of Massachusetts Bay.
in this issue: Seamount Environments off California
Sea Floor off Massachusetts