1845 ǻİȜτȓο τȘȢ ǼȜȜȘȞȚțȒȢ ΓİωȜογȚțȒȢ ǼταȚȡȓαȢ τοȝ. XXXVII, 2007 ΠȡαțτȚțά 11 ου ǻȚİșȞούȢ ΣυȞİįȡȓου, ΑșȒȞα, ΜάȚοȢ 2007 Bulletin of the Geological Society of Greece vol. XXXVII, 2007 Proceedings of the 11 th International Congress, Athens, May, 2007 REMOTE SENSING TECHNIQUES IN THE SEARCH FOR ANCIENT SHIPWRECKS: HOW TO DISTINGUISH A WRECK FROM A ROCK IN GEOPHYSICAL RECORDINGS Dimitris Sakellariou Institute of Oceanography, Hellenic Centre for Marine Research, Anavyssos, Greece sakell@ath.hcmr.gr Abstract This paper presents the way conventional marine geophysical methods may be used with the highest efficiency for deep-water archaeological research, especially for the detection of ancient shipwrecks. Their use becomes all the more effective, when the principles of oceanography and marine geology are being followed during the interpretation of the geophysical recordings. The integration of sub-bottom profiling data provides valuable information on the geological structure of the seafloor’s shallow substrate, which are an almost absolute prerequisite for a geologically reasonable interpretation of the side scan sonar images. Otherwise, interpretation of the sonar recordings may be erroneous or may be in direct discrepancy with the shallow sub-seafloor geological structure. Limitations of the efficiency of the geophysical methods in the case of targets of biogenic or anthropogenic origin or in shallow water environments are also being discussed. Key words: Underwater archaeology, Side scan sonar, subbottom profiler, geologic interpretation. 1. Introduction The aim of this paper is to evaluate the way, marine geophysical methods and geological- oceanographic interpretation of the geophysical recordings should be used and followed, in order to become a powerful tool in deep-water archaeological research. Limitations of the efficiency of the same methods in shallow water are also discussed. The conclusion presented herewith are drawn from the experience we gained during the over twenty research cruises (over 200 days shiptime) devoted to the search for ancient shipwrecks in the last six years in the frame of the collaboration of the Ephorate of Underwater Antiquities (EUA) of the Greek Ministry of Culture and the Hellenic Centre for Marine Research (HCMR). It is widely accepted that remote-sensing techniques are a powerful tool in deep-water archaeological research (Ballard et al., 2000; Quinn et al., 2002a; Quinn et al., 2002b; Chalari et al., 2003; Blondel and Pouliquen, 2004; Papatheodorou et al., 2001; 2005, Sakellariou et al 2006; 2007), especially at depths beyond the range of scuba-diving. Quinn et al (2000) describe adequately the principles of the operation of side scan sonar, sub-bottom profiler and magnetometer and the advantages of using geophysical equipment to record submerged and buried archaeological resources. Nevertheless, the majority of the published works refer to the detection of relatively recent, wooden- or iron-made wrecked ships, the hull of which is rather complete or relatively well preserved and commonly rises well above the seafloor (Hobbs at al. 1994; Barto Arnold III et al. 1999), or to the geophysical investigation of already known submerged archaeological sites (Quinn et al. 1997; 1998).