In recent years, ground-penetrating radar (GPR) has been applied in a rapidly increasing number of stratigraphic studies. Its ability to produce continuous subsurface profiles (under favorable circumstances) has resulted in a better understanding of the shape, extent, and internal structures of facies belonging to several different depositional environments. Thus far, however, GPR has been used in few coastal regions, mainly because of the widespread occurrence of signal-attenuating units. Facies producing signal attenuation include fine-grained estuarine and lagoonal clays and coarser-grained units that contain saltwater. The present study, utilizing a Geophysical Survey Systems Inc. System 3 GPR, focuses on a number of barrier beaches and spits along the New England coast. Most of these barriers are sandy to gravelly; they include a reservoir of fresh groundwater that increases in thickness toward the center of the barrier. To a certain degree, the volume of fresh water is related to the size of the barrier. The occurrence of fresh groundwater in a mainly sandy matrix has turned out to be favorable for GPR application in several instances, with the best results being obtained in the centermost portions of wide and high barriers. Signature quality decreases rapidly toward both the sea and the back-barrier marshes and tidal flats. In both directions, the freshwater-saltwater boundary is increasingly closer to the surface. GPR has proven to be useful in several aspects of the study of coastal barriers. It is an important tool in identifying and characterizing different stratigraphic units that make up a barrier. GPR is also highly useful in determining sediment budgets of coastal systems. Finally, GPR can be applied to determine the occurrence and the maximum extent of peat layers underneath a barrier. Interpretation of GPR profiles, in conjunction with more conventional methods of barrier study, provides a data base that can be used to analyze a range of physical parameters which may have left their mark in a barrier, such as relative sea-level changes, paleotidal range, sediment source and supply, and the effect of storms.


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