How heat alters underlying deposits and implications for archaeological fire features: A controlled experiment

Abstract

While it is true that the use of fire is undoubtedly an important behavioral trait, fire can also leave important traces in archaeological deposits, including altering previously deposited sediments and artifacts. The set of controlled experiments reported here do not focus on fire per se, but rather on the effects of some of the most important variables underlying the transfer of heat to subsurface sediments. These variables, including temperature, duration, sediment type, moisture, and mineralogy, are altered here in ways that essentially bracket the range of conditions under which past fires may have existed. The results show that sediments as much as 10 cm directly below a heat source routinely reach temperatures of 200 °C, with higher temperatures and greater depth of heat transfer possible with longer durations or higher surface temperatures. One of the implications of these results is that a surface can produce substantial thermal-alterations of archaeological artifacts and sediments deposited much earlier in the sequence. Likewise, there are significant implications for the analyses and chronometric dating of thermally altered sediments and burned artifacts.