The Quaternary succession of the Bulè and Alpetto valleys (Monviso Massif, Piedmont) as a possible supply for prehistoric jade axes raw material

Abstract

This contribution presents a geological mapping of the Quaternary succession of the Bule and low Alpetto tributary valleys (Po Valley, Piedmont), together with preliminary data on its petrography. The investigated area, covering an altitude range between 3015 and 1485 m a.s.l., is located in the Monviso Massif Ophiolite Complex, at the contact with marble and calcschist of the Dora-Maira Massif cover. The Quaternary sequence mainly consists of glacial, outwash, debris and landslide deposits, with local torrential/avalanche and colluvial bodies. The investigation on the petrographic composition of these sediments has allowed to recognize the occasional occurrence of jadeitite boulders, likely exploited during the Neolithic period for axe head production. Four possible jadeitite blocks have been found; one of them is described here for the first time, sizing up to 1 m3. In detail, one of the finds is a Neolithic site of jade polishing in the high Bule Valley that was referred to the middle of V millennium BC (Allisio, La Preistoria e l’alta Valle Po, Lar Editore, Perosa Argentina, 2012). The jadeitite blocks have been found in the debris (site A), landslide (site B), glacial (site C) and outwash (site d) sediments. The petrographic characterization of the new jadeitite samples might potentially shed light on the still controversial genesis of these peculiar rocks.