Sediments exposed to high temperatures: reconstructing pyrotechnological processes in Late Bronze and Iron Age Strata at Tel Dor (Israel)

Many of the sediments analysed from Tel Dor (Israel) show structural alterations indicating that they were exposed to high temperatures. This observation is consistent with the abundant evidence for use of pyrotechnology from the earliest exposed Middle Bronze Age strata through the Roman period. Such structurally altered sediments may well represent one of the more widespread and durable records of pyrotechnology, and as such could be invaluable for reconstructing past human activities. The specific aims of this research are therefore to develop the means for identifying local sediments that were altered by different pyrotechnological activities and to elucidate the varying circumstances whereby sediments were exposed to high temperatures in a Late Bronze and Iron Age 1 section. We first characterize natural sediments sampled on and in the proximity of the tell and monitor their transformations due to exposure to high temperatures in an oven and in open fires, focusing in particular on the transformations of the clay mineral components of mud-brick materials. The analytical techniques used include micromorphology, Fourier transform infrared spectrometry (FTIR), X-ray powder diffractometry (XRD) and X-ray fluorescence (XRF) spectrometry. Using the temperature "calibrated" data, we confirm that large volumes of sediments at Tel Dor were exposed to high temperatures. In Area G, we identify three fundamentally different ways that heat-affected sediments were produced and accumulated: (1) In the Late Bronze Age (Phases 11-12) the sediments were heated to temperatures between 800 and 900 degrees C and were then deposited in the area under investigation. A plausible scenario is that these sediments were exposed to heat from ovens or kilns; (2) During the early Iron Age (Phase 10) the heat-affected sediments (heated above 1000 degrees C) formed in close association with casting pits for the working of copper-containing (bronze) objects. (3) During Phase 9 of the Iron Age, heat-affected sediments were produced in situ at this location due to a major conflagration. The temperatures reached around 1000 degrees C. This study shows that analysis of high temperature exposed sediments may be an invaluable means of reconstructing fire-associated activities, even when the actual installations have not been identified during the excavation or were not preserved. (c) 2006 Elsevier Ltd. All rights reserved.