Status for the development of acoustic mapping of submerged stone age sites

The development of an acoustic system for cost-effective mapping of submerged Stone Age sites located on, and embedded in, the sea floor, reported briefly at the 2nd RIO Acoustics Symposium (Gran et al. 2016), has progressed significantly since then. A number of experiments and survey results now demonstrate that it is possible to obtain clear and significant acoustic responses from flint tools and debitage1 produced by humans, whereas naturally-cracked pieces of flint of similar shapes and dimensions do not produce equivalent responses. It has also been demonstrated that debitage responds acoustically even when embedded within sea-floor sediments. So far, responses have been obtained from the cultural layers of Stone Age settlements containing large amounts debitage covered by at least one metre of sediment. It is now important to develop the method further, so it is also effective for smaller amounts of debitage from all siliceous materials used by humans to produce debitage, and at maximum depths in the sediment. There should also be no water-depth limitation when operating the system. Since Stone Age sites can be expected to be found down to approximately -140 m below present sea level (the lowest glacial sea level), the system will support the practical implementation of UNESCO's 2001 convention for underwater cultural heritage, which also covers international waters [1]. The existing types of predictive modelling, based on the bathymetry of former exposed and inhabited surfaces, are very imprecise and expensive, taking into account the costs of precise physical mapping of the potential sites by coring.