Sediments deposited in the lower Argens valley at Fréjus, a well-known Roman Imperial harbor in northwestern Mediterranean, reveal pollutant metal imprints since the Iron Age. Lead, copper and zinc concentrations in sediments above a facies transition from sand (lower) to silt (upper) at 1820–1946 cal. BP (65–130 cal. CE) are four times higher than in the non-contaminated geochemical background unit at the bottom of the core. These correlated chemical and sedimentological shifts in the ancient marine bay follow the growth of the Augustan city subsequent to the building of the Roman harbor during the late first century BCE. Trace metal enrichment factors (calculated from background concentrations) display a slight but significant increase (1.3 to 1.5) in sediments deposited during the Fréjus protohistoric period, just below the facies transition. This enrichment is corroborated by mean 206Pb/207Pb isotope ratios that vary from 1.179 (± 0.002) to 1.193 (± 0.002) and 1.202 (± 0.002) in the Roman, protohistoric and background units respectively. These findings are the first evidence of pollutant metal release into the lower Argens ria during the protohistoric period, as far as 2600 years ago. Lead isotope signatures in the protohistoric sediment layers shed light on several possible geographic origins for ores from which accumulated pollutant metals may originate. These include copper mines in the Alps or the Languedoc regions. Cyprus may also be isotopically invoked as a source that is not supported by archaeological findings and would constitute, if proven true, a new insight regarding metal trades in protohistoric Gaul.
|Number of pages||8|
|Journal||Journal of Archaeological Science: Reports|
|State||Published - Feb 2018|
Bibliographical noteFunding Information:
The project leading to this publication has received partial funding from Excellence Initiative of Aix-Marseille University (A*MIDEX, a French “Investissements d’Avenir” program). The authors thank Fréjus Town Council , The “ Service Municipal d'Archéologie ” and the “ Service Départemental d'Archéologie ” for logistic and funding. This research was conducted as part of the Paleomed ANR program. We are grateful to P. Leveau, P. Excoffon and two anonymous reviewers for providing insightful comments that helped improve the manuscript.
© 2017 Elsevier Ltd
- Iron Age
- Lead isotopes
- Pollutant metals
- Roman harbor
ASJC Scopus subject areas