Provenance of sculptural limestones in protohistoric Provence (SE France): Insights from carbonate rock petrography and stable isotope geochemistry

Abstract

The combination of a detailed analysis of microfacies, diagenetic features and isotopic signatures (carbon and oxygen) of limestones from protohistoric statues and the comparison with substantial regional petrographic and geochemical databases have proven to be successful for constraining the provenance and providing insights into the production of statuary materials in Provence during the Iron Age. The limestones forming the sculptures from Roquepertuse (twin-headed “Hermes”, the lintel with horses and the warrior seated cross-legged) and Rognac (warrior seated cross-legged) are interpreted to derive from lower Barremian carbonate formations from La Fare Massif, likely from near Coudoux, based on 1) micropalaeontologic markers (orbitolinids), 2) grain size, texture and grain composition (oolitic, oobioclastic and bioclastic grainstones), 3) dissolution features affecting ooid cortices and 4) carbon and oxygen isotope signatures. The bryozoan-echinoderm association and the occurrence of Amphistegina suggest that the bust of warrior from La Cloche oppidum (3rd to 1st century BCE) is made of a Miocene limestone from La Couronne Formation. Its isotope composition suggests a provenance from quarries located at Anse du Verdon or possibly further west. The fragment of scapulary tunic found in a disturbed archaeological context dated of 6th to 2nd century BCE on the Baou de Saint-Marcel oppidum, in Segobrige territories east of Massalia, is made of a vuggy limestone whose clotted peloidal-fenestral fabric and isotope signature are consistent with local, lower Pleistocene travertines. The young male head from the Ziem Museum was made of a planktonic foraminiferal, quartz-free limestone with Heterohelix for which no analogue is known in the region, thus suggesting that its place of manufacture is likely to be located outside Provence. Finally, the analyzed set of limestones from protohistoric sculptures, and of certain Provençal provenance, derive from stone production sites geographically close (<20 km) to the places of discovery. A set of non-invasive in situ techniques has been also used to discriminate among the possible sources (magnetic susceptibility, X-ray fluorescence chemical analysis, sound velocity, photogrammetry), but they appeared non discriminant for the present case.