Geoacoustic characterization of Stone Age cultural layers: Preliminary FE modelling

The use of acoustic methods to detect and map submerged Stone Age sites is of great importance for both the archaeological and underwater acoustics research. This paper presents a preliminary numerical study for the geoacoustic characterization of Stone Age cultural layers. Finite element modelling tools are used to investigate the feasibility of detecting acoustically a submerged flint. The acoustic response of a flint buried in soft sediment is simulated. A realistic condition of the flint submerged in a cultural layer surrounded by seawater, sand, mud and a substrate layer of Moraine is also presented. A theoretical calculation of flint resonance frequencies shows that depending on their characteristics, they can produce a wide range of frequencies beyond 2 kHz as it has been observed experimentally. In this study, a Ricker wavelet source is used to estimate the total and scattered pressure fields due to a flint sample. Simulation of the wave propagation accounts for the variation of the compressional and shear speeds of sound. To detect the submerged flint, the source contains the determined fundamental resonance obtained at 10.6 kHz. Snapshots for different views around the flint are analyzed to detect the effect of the flint sample. A sharp peak is noticed to appear at the given resonance of about 18% the emitting signal for the flint buried inside 5 cm of a cultural layer environment. The case of the flint buried in 15 cm of cultural layer overlying and 100 cm of sand is also computed and presented. This first step modelling indicates that acoustic probing may detect and localize worked flints buried inside soft sediment environment. The other results obtained are analyzed and discussed. The study support the development of a geoacoustic inverse method to characterize submerged flints cores and blades but also the accumulation of flakes.