Open-File Report 2008-1364
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Statement of Problem
Purpose and Scope
Description of Study Area
Methods of Investigation
Continuous Resistivity Profiles
Results and Discussion
Continuous Resistivity Profiling
High-Resolution Seismic Profiling
Summary and Conclusions
Geophysical (CHIRP, boomer, and continuous direct-current resistivity) and geochemical tracer studies
(continuous and time-series 222Radon) were conducted along the Broward County coast from Port Everglades
to Hillsboro Inlet, Florida. Simultaneous seismic, direct-current resistivity, and radon surveys in the
coastal waters provided information to characterize the geologic framework and identify potential
groundwater-discharge sites. Time-series radon at the Nova Southeastern University National Coral Reef
Institute (NSU/NCRI) seawall indicated a very strong tidally modulated discharge of ground water with
222Rn activities ranging from 4 to 10 disintegrations per minute per liter depending on tidal stage.
CHIRP seismic data provided very detailed bottom profiles (i.e., bathymetry); however, acoustic penetration
was poor and resulted in no observed subsurface geologic structure. Boomer data, on the other hand, showed
features that are indicative of karst, antecedent topography (buried reefs), and sand-filled troughs.
Continuous resistivity profiling (CRP) data showed slight variability in the subsurface along the coast.
Subtle changes in subsurface resistivity between nearshore (higher values) and offshore (lower values)
profiles may indicate either a freshening of subsurface water nearshore or a change in sediment porosity
or lithology. Further lithologic and hydrologic controls from sediment or rock cores or well data are
needed to constrain the variability in CRP data.
Reich, C.D., Swarzenski, P.W., Greenwood, J.W., and Wiese, D.S., 2009, Investigation of coastal hydrogeology utilizing geophysical and geochemical tools along the Broward County coast, Florida: U.S. Geological Survey Open-File Report 2008-1364, 21 p., plus apps. A-C.
U.S. Geological Survey
Florida Integrated Science Center
U.S. Geological Survey
600 4th Street South
St. Petersburg, FL 33701
Christopher D. Reich at email@example.com
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