Selective reburial: a potential approach for the in situ preservation of waterlogged archaeological wood in wetland excavations

Abstract

Excavations at Dispilio, a prehistoric lakeside settlement in northern Greece, have revealed a significant number of vertical wooden piles that need to be protected during and after excavation. Lifting of the piles is not possible and approaches such as reburial, cannot currently be implemented as excavation is still in progress. In 2005, several posts were “selectively buried” on an experimental basis, by encasing them in PVC pipes and backfilling with the surrounding sediment. This approach appeared to be capable of protecting the piles during excavation and be a potential solution for their post-excavation preservation. This preliminary study sets out to asses if this alternative approach to reburial could be an effective in situ preservation method.Fresh beech and pine samples were “selectively buried” similarly to the encased piles, and exposed to open excavation conditions. Retrieval of samples was undertaken every three months over a one year period and their condition was assessed by their physical properties, chemistry and biodeterioration. As no baseline data existed for the site, spot measurements of Eh, T, pH and water table were recorded every three months at three dipwells located inside the excavation trench. Physical properties of both buried and exposed pine and beech samples did not indicate considerable decay as longer exposure periods appear to be necessary to adequately reflect the effects of deterioration. However, assessment of micro-morphology and chemistry showed some differences in the deterioration degree of the exposed samples compared to those buried in sediment.Monitoring results showed high seasonality in all environmental parameters throughout the 12 month monitoring period and indicated a hazardous environment for wood preservation.Preliminary results obtained showed that the “selective reburial” is directly dependant on overall site conditions. It reconstructs a similar microenvironment to the site burial environment and therefore can be effective for sites that favour wood preservation. In contrast to typical reburial, “selective reburial” can be applied during excavation without impeding its progress. However for environments like the one studied, this method is not recommended after excavation.