An experimental study of fuel use at the microscale: Plant and dung microfossil indicators from combustion installations

This paper addresses the contribution of experimentally-produced combustion installations to microarchaeological research on the identification, characterization and taphonomy of fuel materials as valuable past traces of fire use. Recent studies have investigated the taphonomy of microscopic remains (primarily opaline phytoliths and calcitic microfossils) from traditional mud-constructed ovens and their associated ashes, as well as of dung material experimentally burnt under open-air conditions, and under laboratory-controlled experiments across a range of temperatures in different combustion situations. In light of these previous studies, the present work builds on modern replicas of fire installations at the Iberian Citadel of Calafell (Tarragona, northeastern Spain), a reconstructed Iron Age settlement that hosts experimental archaeology research projects. The innovative aspect lies in the integrated study of plant and dung microfossils from experimentally-operated replicas of two types of archaeological combustion structures (hearths and ovens) from diverse locations (indoors and outdoors). These were operated under diverse weather and humidity conditions to record detailed firing measurements (temperature and time), using a range of fuel sources according to the available archaeobotanical data (pine and oak wood, pine cones, barley straw and weeds, palm leaves), as well as sheep and cattle dung. The study provides novel comparative reference records regarding the preservation and integrity of microscopic fuel remains, further pointing towards the value of experimentally-produced datasets for reconstructing fuel use from Iron Age fire installations, and perhaps from similar archaeological hearths and ovens from other time periods as well.