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Floridablanca is an 18th century archaeological site located in southern Argentina. Archaeological investigations at the site began in 1998, and in 2000 we started a project to perform geophysical studies there. In this paper, we report the implementation of electrical and electromagnetic (EM) methods in a sector of the site that corresponds to the settlers' houses. The objective of the project was to characterize the zone and the buried archaeological structures (adobe walls, tiles from a collapsed roof) with 2D and 3D electrical and EM techniques. We first applied an EM induction method covering a 600-m 2 area with a frequency ranging from 1000 to 19 000 Hz. A 3D visualization of the in-phase and quadrature components gave an initial description of anomalies possibly associated with buried structures. We then performed dipole-dipole profiles and inverted the data to obtain the corresponding 2D and 3D electrical images. Finally, after correlating the information obtained from the analysis of both EM and electrical data, we performed a more localized 3D dipole-dipole mesh (25 m 2) to achieve the final electrical image of the most representative buried structure. The combination of both techniques allowed us to map two entire houses and to identify three types of walls: main, separating, and inner. These results have been confirmed by an archaeological excavation.

We present the application of three geophysical methodsöground-penetrating radar, resistivity and electromagnetic inductionöto the Floridablanca archaeological site at San Julia¤ n Bay, Argentina. The objective of the prospection was to detect buried archaeological structuresömostly adobe wallsöto delimit these structures, tofindtheircharacteristicsandto study thepresence oftilesattributable to roof collapse within the zone of interest. Profiles were carried out in this zone and outside it to compare results. A periodic distribution of low-contrast shallow anomalies was found that indicated the presence of different types of buried walls within the zone. Also the absence of tile accumulations could be determined. These results provided the archaeologists with useful information to design a more efficient excavation plan

The objective of the research contained in this paper was the characterization of a contaminant plume and the description of the surrounding area, in order to give information for future remediation. The origin of the plume was a hydrocarbon spill produced by fissures in a purge chamber belonging to a gas transmission system. Data from control wells indicated that the soil was composed mainly of clays. The most important result was that, close to the chamber, a [Formula: see text]-thick layer of gasoline was detected at [Formula: see text] depth, floating over the water table. This is a case in which a resistive contaminant like hydrocarbon is located in a conductive medium; in these circumstances geoelectrical prospecting is particularly good for characterizing the zone. The extent of the area under study was [Formula: see text], approximately, and the thicknesses involved were more than [Formula: see text] of, in many cases, very conductive materials. Thus, a field design was required that would cover the zone with deep penetration and at the same time optimize lateral resolution. By combining Wenner and dipole-dipole configurations, the electrical imaging of the contaminated zone and the description of the surrounding soil were achieved.

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We obtain the transverse electric (TE) and transverse magnetic (TM) Fresnel reflection coefficients for different interfaces in the subsoil: air/fresh‐water, air/seawater, fresh‐water/seawater, air/NAPL (non‐aqueous phase liquid), NAPL/water and water/NAPL. We consider a range of NAPL saturations, where the complementary fluid is water with 0.65 ppt (parts per thousand) of NaCl. The common feature is that the TM mode (parallel polarization) has a negative anomaly and the TE mode (perpendicular polarization) has a positive anomaly. For the cases studied in this work, pseudo‐Brewster angles appear beyond 40° for the air/NAPL and NAPL/water interfaces and at near offsets (below 40°) for the water/NAPL interface. Pseudo‐critical angles are present for the water/NAPL interface. Besides the reflection strength, the phase angle can be used to discriminate between low‐ and high‐conductivity NAPL, when the properties of the upper medium are known. A wavenumber–frequency domain method is used to compute the reflection coefficient and phase angle from synthetic radargrams. This method and the curves can be used to interpret the amplitude variations with angle (AVA) of reflection events in radargrams obtained with ground‐penetrating radar (GPR).