Archaeomagnetic investigation of bricks from the VIIIth–VIIth century BC Greek–indigenous site of Incoronata (Metaponto, Italy)

Abstract : An archaeomagnetic investigation of two sets of brick fragments (in total 39) along with a radiocarbon date from one of the most important Greco­indigenous archaeological sites in the Central Mediterranean, the VIIIth­VIIth Century BC site of Incoronata (Metaponto, Italy) has been carried out in order to aid archaeological understanding of the site as well as to produce high quality archaeomagnetic data. A full suite of rock magnetic experiments have been carried out in addition to the classical Thellier method experiments with correction for anisotropy of TRM and cooling rate. The results indicate that the two sets of bricks are magnetically identical and have the same heating history and thus it is inferred the same origin. It seems that the bricks had been reused in two different contexts: (1) mixed with stone and ceramics in deposit pits and (2) used to consolidate an artificial plateau. The brick samples all contain a single component of remanence and thus, importantly, this study has shown that the hypothesis of destruction by fire is no longer tenable to explain the deposit pits previously interpreted as being storage houses or dwellings (oikoi), but is consistent with the suggestion that the pits are ritual deposits. Whilst it did not prove possible to obtain an estimate of the inclination of the geomagnetic field (since the bricks did not gain their remanence whilst on one of their flat surfaces), the archaeointensity experiments (with anisotropy of TRM and cooling rate correction) give a mean intensity of 85 ± 5 µT for the field at Incoronata during the VIIIth­VIIth century BC. This is almost twice the present day field strength and thus provides further evidence that the field was strong over at least a 30° longitude area of the globe during this time.