Effects of stepped-combustion on fresh pollen grains: Morphoscopic, thermogravimetric, and chemical proxies for the interpretation of archeological charred assemblages

Macroscopic charred remains have long since been studied in archeology, archaeobotany, and palaeoenvironmental research. Despite this long tradition, very little attention has so far been given to microscopic charred botanical remains, apart from microcharcoal. The discovery of extraordinarily well-preserved fossil bee-breads and fragments of charred honeycombs in an Etruscan settlement in northern Italy prompted us to perform a combustion experiment on fresh bee-breads, aimed to study the main morphological, structural and chemical modifications induced by heat on pollen grains and whole bee-breads. The experiment enabled the observation and quantification of changes in overall shape and size, brightness, tectum structure and sculptures of pollen grains, as well as changes in the chemical composition of whole bee-breads. Data obtained on fresh material were then applied to archeological samples from the Etruscan Forcello settlement for inferences on the combustion temperatures reached during the fire that destroyed the site.