Archaeological Prospection Archaeol. Prospect. 12, 19–30 (2005) Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/arp.244 Ground-penetrating Radarand Geo- electrical Simulations of Data from the Floridablanca Archaeological Site M. DE LA VEGA, 1, * A. OSELLA, 1 E. LASCANO 1 AND J. M. CARCIONE 2 1 Dto. de F|¤ sica-Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires, Ciudad Universitaria, Pab.1,1428, Buenos Aires, Argentina 2 Istituto Nazionale di Oceanografia e di Geof|¤ sica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico,Trieste-Italy ABSTRACT In this work we characterize the electromagnetic response of archaeological remains of a Spanish fortress situated on the Atlantic coast in Patagonia (Argentina).The fortress, part of the Floridablanca colony, founded in the eighteenth century, has been surveyed with non-invasive electromagnetic techniques (ground-penetrating radar (GPR) and the geo-electric method). The surveys indicate the presence of adobe walls of various sizes and width having different preservation states. Use of inversion algorithms alone to interpret the data has not been conclusive in obtaining a reliable model, because many uncertainties remained. To aid the interpretation, we make use of modelling methods to simulate the low- and high-frequency electromagnetic responses of the structures. The walls can be differentiated in spite of the low resistivity contrast with the surrounding media. The resolution of the 500 MHz antenna allows a satisfactory determination of the location of the walls and their conser- vation state. Similarly, the geo-electricalresponse has enough sensitivity to detect the innerand major walls.Copyright ß 2005 JohnWiley & Sons, Ltd. Key words: simulation; ground-penetrating radar; geo-electric; walls; resolution; Floridablanca Introduction Geophysical methods have proven to be very useful to archaeologists in order to detect, map and study the characteristics of different types of objects and structures in the subsurface. These methods allow the evaluation of their conserva- tion state, the identification of different construc- tion phases and zones disturbed by agricultural activities or plundering. Moreover, the investiga- tion of geological deposits and buried landforms is useful for generating palaeoenvironmental information (e.g. Herbich et al., 1997; Silliman et al., 2000; Weston, 2001). Although these methods have been applied systematically in archaeology during the past 50 years, their implementation in Argentina is relatively new, having started in the middle of the 1990s (Carrara, 1996; Ponti et al., 1996). In 2000, we started the acquisition of geophysi- cal profiles at the Floridablanca archaeological site, which is located near San Julia ´n Bay, Argentina. Floridablanca was a Spanish colony inhabited for a period of four years (1781–1784). The site has an area of 10 000 m 2 and is characterized by the pre- sence of elevations of the terrain that correspond to buried archaeological structures, as indicated by previous excavations (Senatore et al., 2000). The objective of the survey was to detect the buried Copyright # 2005 John Wiley & Sons, Ltd. Received 10 June 2004 Accepted 29 October 2004 * Correspondence to: M. de la Vega, Dto. de Fı ´sica-Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires, Ciudad Universitaria, Pab. 1, 1428, Buenos Aires, Argentina. E-mail: matias@df.uba.ar