Mine dans la forêt du Morvan
L’article “Tracking archaeological and historical mines using mineral prospectivity mapping” par Monna, F., Camizuli, E., Nedjai, R., Cattin, F., Petit, C., Guillaumet, J.-P., Jouffroy-Bapicot, I., Bohard, B., Chateau, C., Alibert, P. vient d’être publié par Journal of Archaeological Science. 49 (2014) 57-69. pdf.
Il s’agit d’un transfert de technologie depuis les techniques les plus récentes utilisées aujourd’hui en prospection minière vers le monde de l’archéologie. Le but est de restreindre considérablement la zone qui doit être prospectée par l’archéologue qui cherche à découvrir les mines exploitées par nos prédécesseurs. Pour cela, les analyses de sédiments de rivières effectuées dans le passé par le BRGM (http://sigminesfrance.brgm.fr/) sont mises à contribution. Deux types de traitements mathématiques ont été utilisés: l’Exploratory Data Analysis (EDA) et le modèle fractal. Combinés à un système d’information géographique, les résultats définissent des zones à forte prospectivité qui permettent à l’archéologue de guider ses recherches. Le gain de temps est appréciable puisqu’en prospectant seulement 15 à 20% de la zone, plus de 70% des structures sont découvertes.
Abstract: The present study proposes a technological transfer from modern mining prospection to the field of archaeology, providing a methodology to facilitate the discovery of ancient mining sites. This method takes advantage of the thousands of geochemical analyses of streambed sediments, performed by national geological surveys to inventory mineral substances. The datasets are treated following two different approaches: Exploratory Data Analysis and a fractal-based method, in order to delineate geochemical anomalies. Mineral rospectivity maps are then obtained by combining the results with a geographical information system. The surroundings of the Celtic oppidum of Bibracte, French Massif Central, known to have been mined at least since the Late Bronze Age until Modern Times, have been chosen to exemplify the method’s potential in archaeology. First, an exhaustive record of the mining sites was undertaken over a pilot area by pedestrian prospection. If mineral prospectivity maps had been used as guidelines, ~70% of these mines would have been discovered by prospecting only ~15- 20% of the whole area. Besides saving a significant amount of time and effort, the approach described here may supply clues for determining the nature of mineral substances exploited in the past, when such information cannot be straightforwardly obtained from the field or from textual archives. It should however be noticed that this approach is proposed as a first step before peer archaeological investigation following more conventional methods. Technically, there is no real obstacle to the application of the methodology proposed here, because (i) software and associated packages are freely available from the web, as well as original geochemical datasets (at least in France), and (ii) minimal mathematical skills are required.