ORGANIC CARBON LOSS AND CHANGES IN δ13C VALUES AS EVIDENCE OF FIRE AT ARCHAEOLOGICAL SITES

Studies have shown that soils can be raised to relatively high temperatures (100-700°C) when heat is applied from an above-ground fire source (i.e. campfire, logging slash, etc.) (Campbell et al., 1995; Ryan, 2000). These temperatures can remain high for several hours and reach depths of 10 cm or more within the mineral horizons of the soil. An Inseptisol and an Alfisol from a Western Maryland deciduous forest were sampled by horizon and exposed to the elevated temperatures associated with heat transfer measured beneath campfires. Substantial loss in organic carbon and change in carbon stable isotope composition was observed, even after exposure to the lower end of the soil heating spectrum (200-400°C). Analysis showed that a comparison of carbon isotope enrichment in organic matter beneath a suspected campfire site to that of unaltered soil would give quantitative information about the minimum temperature in the soil beneath the campfire. Application of these results may lead to particular insight for archaeological sites where soil surfaces or paleosols have been eroded or otherwise truncated.