Diagenetic screening of bone samples; tools to aid taphonomic and archaeometric investigations

It is generally a challenge to interpret incomplete and degraded skeletal assemblages found during archaeological excavations. Several events after the death of animals and humans, before and after burial, will have influenced the situation as seen upon excavation. This post-mortem sequence of events can be called the taphonomic history of bones. Taphonomic signatures detected using histology can provide additional data on deposition/ burial and the evolution of the burial environment. This paper reports on the results of a histological characterization of diagenetic alterations in a bone assemblage from the Roman Period burial and settlement site of Castricum, located in the province of NoordHolland in the Netherlands. The aim is to assess the relationship between bone histology and known taphonomic events. Both transmitted light microscopy and scanning electron microscopy were used to investigate histological changes. In 1995, the excavation at Castricum uncovered skeletal material of humans and a variety of animal species that had received different burial treatments. The humans, as well as some dogs and cattle, were buried as complete inhumations. The skeletal remains of horses provided evidence of surface exposure before deposition. Additionally, both environmental changes (e.g. variations in groundwater levels) as well as disturbances by later human activity are known to have occurred since the internment of the bones. Together with the animal refuse bones from the site, this assemblage provides an excellent opportunity to investigate the relationship between early taphonomy, burial conditions and histological appearance. The complex taphonomic history of the Castricum skeletal material was found to be reflected in several characteristic alterations of the bone microstructure such as extent of bioerosion, cracking, staining and inclusions of framboidal pyrite crystals. This allowed for the reconstruction of a post-mortem sequence of events.