Summary for Field Activity Number 2004-014-FA

Area of Operations: Cape Cod National Seashore, Massachusetts, United States, North America, North Atlantic

Dates: May 17, 2004 to May 20, 2004

Objectives: Electrical resistivity surveying and radium/radon sampling.

Type of Activity: Sampling

Information to be derived: Samples and Chemical Analysis
Electrical resistivity survey data

Summary: Abstract prepared for Coastal Geotools Conference, March 7-10, 2005, Myrtle Beach, SC: INTEGRATION OF CONTINUOUS RESISTIVITY PROFILING AND SEISMIC REFLECTION DATA IN THE NEARSHORE ENVIRONMENT; VeeAnn A. Cross, David S. Foster, John F. Bratton U.S. Geological Survey, Woods Hole, MA; Keywords: groundwater, resistivity profiling, seismic reflection, 3D mapping, nearshore; ABSTRACT-- Groundwater discharging to bays and estuaries is of concern because it often contains elevated concentrations of nutrients and other pollutants that affect coastal ecosystems. Saltwater intruding into coastal aquifers due to excessive pumping has also affected water supplies of coastal communities. Commonly underrepresented in groundwater studies is the understanding of the geometry and stratigraphic control of groundwater flow systems beneath coastal water bodies. This issue is addressed with the use of continuous resistivity profiling (CRP) and seismic reflection data. The CRP system was used to map the freshwater-saltwater interface in the subseafloor environment of outer Cape Cod, Massachusetts. An AGI SuperSting Marine system was used, which consisted of a DC power source, an electrode streamer cable, a GPS receiver, a fathometer, and shipboard logging software. Collected data were processed with an inversion program, AGI EarthImager 2D. Using a combination of GIS software packages, including ArcGIS (ESRI) and EarthVision (Dynamic Graphics), these processed data were integrated with subsurface geology as interpreted from results of previous seismic reflection surveys and onshore drilling. This data integration resulted in a 3D representation of the groundwater system where its relationship to the subsurface geology in the sub-aqueous environment, including confining units and preferential flow conduits, can be examined in greater detail. This approach can be applied to other marine/estuarine areas to characterize groundwater flow in the nearshore environment.

USGS Project Number: 2921-0I410 - Project Description

Contact: John Bratton (jbratton@usgs.gov)

InfoBank: uses the identifier H-1-04-MA. Visit this site for more information.

InfoBank: uses the identifier R-2-04-MA. Visit this site for more information.