On the in-situ detection of flint for underwater Stone Age archaeology

Managing and protecting archaeological sites of significant cultural interest threatened by construction works is a central archaeological activity today. This paper discusses a resonance feature in worked flint (blades and flakes) that may facilitate an easier detection of submerged Stone Age sites than it is possible today. Underwater archaeology represents an important aspect of Stone Age archaeology, because the submerged sites often display better preservation than land sites, and also can be part of extensive areas with well-preserved inundated Stone Age landscapes and thus can provide important environmental information. The Stone Age sites often contain many hundreds and often many thousands flint blades and flakes. As demonstrated by earlier unpublished sound lab experiment, the resonance feature of the flint pieces can be excited, and the resonance signal is strong and with narrow spectral peaks in spite of some damping. In this paper, the assumption is that it should be possible to detect buried flint blades and flakes from their resonance spectrum. The flint pieces are modeled as simple geometrical objects embedded in sediment. Their backscatter signals are then synthesized and their spectral pattern and resonance frequencies are modeled and compared to early experimental results obtained from a series of prehistoric blades and flakes in a sound lab experiment. Advanced signal processing methods, i.e., wavelet and Hilbert transformations, are used to extract the flint resonance features. The feasibility of locating buried worked flints in situ based on the basis of resonance features of the backscatter signals is discussed.