Neural Networks to Map Archaeological Lithic Artefacts

Abstract

An analytical non - destructive strategy to chemically characterize lithic artefacts has been developed. Around 100 archaeological lithic materials found in Neolithic - Chalcolithic sites in the Mediterranean region of the Iberian Peninsula and nowadays stored in different museums of the Valencian Community (Spain), were studied. The materials belong to different typologies of rock (diabase, sillimanite, ophite and amphibolite) and were analysed employing portable energy dispersive X - ray fluorescence spectroscopy (pXRF) directly in the rock surface. The obtained data were processed through neural networks protocol, specifically the so - called Kohonen networks or Self Organised Maps (SOM), to map the geologic samples. This self - organized topological feature maps are suitable to deal with multidimensional representations and map them in a two - dimensional space of neurons, following an unsupervised learning protocol. SOM is used to reduce multidimensional data onto lower - dimensional spaces and clustering procedures. As a result, SOM create spatially organized representations, which enhance the discovery of correlations between data. In this case the method has enabled the evaluation of elemental markers related to each rock type behaving as a fine hidden pattern detector and so understand the possible advantages and disadvantages of the analytical method employed to define provenance issues. The attribution suggested by statistics is mainl y driven by the composition of rocks essential minerals which are linked to the different petrogenetic conditions. The results showed that in most of the cases the distribution and dispersion of the chemical profile depend of the kind of rock, and clea rly suggest that a good way to identify stone tools raw material procurement is to look for elemental markers, being the prior st ep to create an approximation to ancient exchange networks and their evolution in a diachronic axis .