Temperature, compression and fragmentation: an experimental analysis to assess the impact of taphonomic processes on charcoal preservation

摘要

This paper explores how mechanical properties of different South Asian tree taxa might influence charred wood fragmentation and the composition of charcoal assemblages retrieved from archaeological contexts. The dataset is composed of selected plant species that were collected in Gujarat (Northern India) in September 2007 as part of the North Gujarat Archaeological Project. The taxa analysed represent the most common wood species found in the arid thorn scrubland formation in South Asia and are among the most abundant identified in Neolithic and Chalcolithic archaeological sites in this area. The specimens have been measured and subsequently charred at three different temperatures, under constant conditions. Afterwards, their resistance to compression has been measured on two planes, parallel and perpendicular to the direction of fibres, using a Hounsfield 5-kN machine. The tests were performed in order to understand the different response to compressive stress of wood that has been subject to a range of thermal degradations. The standardised treatment applied to the samples has permitted the comparison of results and the delineation of simple correlations and divergences among the species analysed. Furthermore, the utilisation of a relatively simple operating protocol easily allows the addition of further data in the future. The applied protocol was specifically designed to answer archaeological questions. Therefore, even though from a material science point of view some of the measurements were not taken according to the prevailing standard procedures, it offers valuable data for anthracological research applied to archaeology in arid zones.