Abstract
Alignments of heating stones hearths are common in Southeast France and in Switzerland at the Late Bronze and Early Iron Ages. Because of the plateau effect on the radiocarbon calibration curve, the hypothesis that the structures were in use almost synchronously within an alignment is still debated. For archaeomagnetic dating purposes, we studied eight heating stones hearths, six of them organized in two parallel alignments, from the site Clos de Roques -Route de Barjols in Saint-Maximin-la-Sainte-Baume in Southern France. Archaeodirections were determined after thermal and alternating field demagnetizations and archaeointensities using the Thellier-Thellier protocol with corrections for the anisotropy and cooling rate effects. The large difference between average archaeodirections (more than 20° in declination) clearly demonstrate that the last use of the structures was not contemporaneous, bearing in mind that no archaeological evidence of multiple uses was found. The archaeomagnetic dates were obtained with the local prediction of declination, inclination and intensity by the European geomagnetic model SCHA.DIF.4k. They range between the end of the 8th century BCE and the end of the 5th century BCE with a ~ 150 years precision at 95 % of confidence for most structures. These results confirm the occupation of the site at the Early Iron Age given by other dating methods but imply a longer use than the one around 625-575 BCE suggested by the typochronology of ceramic artefacts. The different archaeomagnetic dates obtained within the alignments show that the alignments of hearths were not established over a short period as previously thought but over a couple centuries, highlighting the important and still poorly understood role of these fired structures in the area.