Attempts to Date Salt-making Activity in Iron Age Britain using Magnetic Inclinations

• Published in: Journal of archaeological science 1999-11, Vol.26 (11), p.1377-1389
• Main Authors: Borradaile, G.J., Lagroix, F., Maher, L., Stewart, J.D., Lane, T., Linford, N., Linford, P.
• Format: Article
• Language: English
• Subjects: Archaeology and Prehistory; archeomagnetism, Iron Age, salt-making, Britain, magnetic inclination; Earth Sciences; Europe; Geophysics; Humanities and Social Sciences; Iron Age; Metal Ages; North West Europe; Prehistory and protohistory; Sciences of the Universe
• ISSN: 0305-4403; 1095-9238
• DOI: 10.1006/jasc.1999.0413

“Briquetage” describes all the ceramic equipment used in extracting sea salt in prehistoric and Roman Europe. It includes semi-cylindrical desiccating troughs and the stands, supports and clips used to stabilize them over hearths. In many cases, the baked hearth linings or superstructures are included under “briquetage”. Upon first inspection, archeomagnetic dating seems inappropriate because the briquetage is broken and disoriented material. Although the ancient magnetic declination cannot be referred to the present North direction, the desiccating troughs acted as water-level gauges so that a tilt correction permits one to estimate the archaeoinclination. The range of inclinations brackets the age of the saltern use within the last two centuries BC . This is compatible with ceramic styles and two radiocarbon ages of charcoal from a supposedly contemporaneous hearth. The archeodeclination of 7° (α 95=10°) from a contemporary in situ hearth confirms this age range. Thus, we attribute the Lincolnshire salterns to Late Iron Age activity. The paleosecular variation for southern Britain over the last two millennia is sufficiently characteristic in many time periods to permit the use of inclinations alone to bracket ages. This requires material with some original horizontal reference, e.g. masonry fragments, disrupted sedimentary layers or pot-bases.