Plant remains preserved in products of metal corrosion: source of evidence on ancient plant materials and environment from burial contexts

Abstract By-products of metal corrosion, when coming into contact with organic matter, have the capacity to preserve it from decay. A pilot study was conducted aiming to explore the potential and limitations of plant remains preserved in by-products of metal corrosion for archaeobotanical research. The organic remains considered come from the surface/immediate proximity of the metal funerary artefacts of two ancient cemeteries—Varna and Messambria, Eastern Bulgaria. Metal corrosion by-products were observed and sampled, under a low magnification stereo microscope. Subsequently, the plant macrofossils recognised were analysed under reflected light and a scanning electron microscope (SEM). Additionally, pollen was extracted from the metal corrosion by-products, using standard acetolysis. The analyses from the graves of both cemeteries allowed identification of textiles and plant fibres, as well as wood ( Cornus sp., Pinus sp., Viburnum sp.). At Varna cemetery epidermis fragments of Juncus sp. were recognized, while at Messambria necropolis fruits of almond were found. The pollen analysis from Varna points to use of flowers in the ritual ( Daphne tetrads were recorded) and shows a notably open landscape with 77% non-arboreal pollen (NAP). The palynological analysis from the Messambria necropolis revealed the use of flowers in the burial ritual indicated by clusters of Vitis, Cistus and Rosaceae pollen. The surrounding vegetation was dominated by open oak woodland and open habitats (43% NAP) with a strong presence of anthropogenic indicators. The outcome of the study proved to be promising for reconstructing details of the burial rituals including associated plant materials, as well as the surrounding plant habitats during the functioning of the cemeteries.