Protohistoric briquetage at Puntone (Tuscany, Italy): principles and processes of an industry based on the leaching of saline lagoonal sediments

Abstract

A protohistoric (c.10th–5th c. BC) briquetage site at Puntone (Tuscany, Italy) was studied to unravel the salt production processes and materials involved. Geophysical surveys were used to identify kilns, pits, and dumps. One of these pits and a dump were excavated, followed by detailed chemical and physical analyses of the materials encountered. The pit had been used for holding brine, obtained by leaching of lagoonal sediment over a sieve, that afterwards was discarded to form large dumps. Phases distinguished indicate that the pit filled with fine sediment and was regularly “cleaned.” The presence of ferroan‐magnesian calcite in the pit fill testifies to the prolonged presence of anoxic brine. The production processes could be reconstructed in detail by confronting the analytical results with known changes in composition of a brine upon evaporation. These pertain in particular to the accumulation of “bitterns” and increased B (boron) concentrations in a residual brine. Both could be traced in the materials studied, and were found to be far more indicative than the ubiquitously studied concentrations of Cl and Na.

Intensive archaeological survey at Piscina Torta: use of a low-cost RTK portable kit to materialise a UTM grid on the ground

“…The latter is a widespread technique all over Europe [2][3][4] and consists in boiling brine in a ceramic container (the reddish jars) until the salt (NaCl) precipitates due to the water evaporation. To extract the salt cake breaking the vessel is necessary: this would explain the huge amount of potsherds in those specialised sites [5][6][7]. Before the archaeological excavation, we decided to collect all the surface artefacts in a grid of 5x5 m. The aims were both to confirm (or modify) the chronology of the site and to obtain data that could guide us in the placement of the subsequent excavation soundings through the study of surface ceramic density.…”

Low-cost GPS/GNSS Real Time Kinematic receiver to build a cartographic grid on the ground for an archaeological survey at Piscina Torta (Italy)

“…The latter is a widespread technique all over Europe [2]- [4] and consists in boiling brine in a ceramic container (the reddish jars) until the salt (NaCl) precipitates due to evaporation. To extract the salt cake, it is necessary to break the vessel: this would explain the huge amount of potsherds in those specialised sites [5]- [7].…”