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

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.     

How an integrated diagnostic approach can help in a correct evaluation of the state of preservation of waterlogged archaeological wooden artefacts

Artefacts made of wood coming from archaeological excavations provide insights into human cultural behaviour of the past. They show how man utilised natural resources and how the development of woodworking techniques and artistic endeavour were developed. Within archaeological contexts, waterlogged anaerobic conditions generally preserve the appearance of artefacts, although wood is subject to severe decay processes. The said conditions can transform the original material into a new one, thus demonstrating specific differences from those of the “fresh” wood of the same species. In order to assess these new properties correctly, an integrated diagnostic approach is needed, one which includes a multidisciplinary (micromorphological, physical and chemical) evaluation of the state of preservation.     

Potential misidentification of in situ archaeological tool-residues: starch and conidia

Microscopic identification of organic residues in situ on the surface of archaeological artefacts is an established procedure. Where soil components morphologically similar to use-residue types exist within the soil, however, there remains the possibility that these components may be misidentified as authentic residues. The present study investigates common soil components known as conidia, fungal spores which may be mistaken for starch grains. Conidia may exhibit the rotating extinction cross under cross-polarised light commonly diagnostic of starch, and may be morphologically indistinguishable from small starch grains, particularly at the limits of microscope resolution. Conidia were observed on stone and ceramic archaeological artefacts from Honduras, Palau and New Caledonia, as well as experimental artefacts from Papua New Guinea. The findings act as a caution that in situ analysis of residues, and especially of those less than 5 μm in size, may be subject to misidentification.     

In situ corrosion studies on the submarine Resurgam: A preliminary assessment of her state of preservation

Abstract

The submarine Resurgam was the world's first mechanically powered submarine, built in 1879 and lost in 1880 off the north coast of Wales. She was discovered 116 years later in 1996 and as part of an initial survey the corrosion characteristics and state of preservation of the hull were investigated.

The results showed that the hull was actively corroding, although the corrosion mechanism was such that the corrosion products formed were likely to be of a protective nature. The present corrosion rate of the wrought-iron hull of the submarine was hard to quantify based on established means, as the profile of 116 years of corrosion products had not been retained over the entire hull due to spalling of the corrosion products. Where the concretion profile was retained it was possible to calculate an average corrosion rate of 0.1 mm per year. This, coupled with the knowledge of the corrosion rate of freshly exposed wrought iron in sea water, enabled a ‘worst case’ corrosion rate of between 0.1–0.2 mm per year to be estimated.

Two arrays of sacrificial anodes were attached to the hull to test the feasibility of using this method to slow the corrosion rate and stabilize the submarine In situ. It is too early to say how successful these will be in the long term, yet initial results were encouraging as the corrosion potential was seen to shift to a more cathodic and thus less corrosive potential after their attachment.     

Correlating archaeological and palaeoenvironmental records using a Bayesian approach: a case study from Sutton Common,South Yorkshire,England

This paper presents a case study aimed at correlating archaeological ‘events’ (obtained from radiocarbon measurements and dendrochronology) from the site of Sutton Common with a radiocarbon-dated pollen sequence obtained from a palaeochannel deposit adjacent to the area of the main archaeological activity. It demonstrates the use of a Bayesian approach to quantifying whether the timing of palynological ‘events’ interpreted as reflecting anthropogenic impacts are likely to be associated with archaeological ‘events’. The results suggest that Bronze Age activity in the form of a mortuary enclosure and associated cremation burials are probably not contemporary with the palynological evidence for disturbance to the oak–hazel woodland in this period. Subsequent evidence for local woodland clearance and agriculture is estimated to precede the construction of the large Iron Age enclosure in 372 BC, with increases in ‘anthropogenic indicators’ following this ‘event’. The construction of the site does not appear to have had a pronounced impact on the local vegetation, with hazel the only woody taxon to show clear reductions. Despite the use of a substantial number of oak timbers in the enclosure palisade, percentages of oak remain remarkably stable. Later farming activity on the site probably post-dates the end of activity in the enclosures. The value of the methodology is discussed in relation to quantifiable and robust correlations of archaeological and palaeoenvironmental narratives of landscape and human activity.     

Ancient Iberian horses: a method to recover DNA from archaeological samples buried under sub-optimal conditions for preservation

Existing methods to extract, amplify, and sequence ancient DNA (aDNA) from horse bone and teeth were optimized to recover DNA from a depositional environment of highly permeable acidic soil. DNA was successfully retrieved using 0.10g of bone powder from horse (Equus sp.) remains dating to 25 K years utilizing the methods optimized for this archaeological material. The genetic analyses were performed in a facility that is dedicated to ancient DNA research (Paleo-DNA Laboratory, Thunder Bay, ON, Canada) and has not been previously used to analyse modern or ancient horse DNA. Research was replicated to obtain reliable sequencing results for six samples from the Iberian Peninsula that were consistent with published sequences of Equus caballus. The archaeological sequence data obtained support hypotheses that promote the significance that the Iberian Peninsula has had to the multi-focal centres of origin for horse domestication and distribution of modern horse breeds. The data presented may provide evidence of the existence of an Iberian refugium for Equus during the last glacial period, 10 K years BP. Further molecular data analyses will enhance the ideas presented by this data and our understanding of horse domestication and phylogeny. The optimization of molecular techniques to successfully obtain DNA using minimally destructive, cosmetically sensitive techniques from archaeological remains endeavours to foster further cooperation between museums and researchers.     

The survival of biochemical information in archaeological bone

The paper gives a review of the advantages of genetic information potentially available from surviving molecules (especially proteins) in bone. Survival of such information depends on degradative processes during burial. Conventional protein chemical and immunochemical investigations on various organic components remaining in buried archaeological bone are described. The results provide information on the chemistry of collagen degradation, and indicate that polymorphic macromolecules survive at too low a concentration to be easily detectable.     

Relevance of soil biology and fertility research to archaeological preservation by reburial

Abstract

This paper discusses how soil biological information can help to improve understanding of, and possibly inform decisions about, preservation of organic archaeological remains by reburial. A brief summary of the properties of the soil biological community is followed by an outline of results from recent biological investigations following the recovery of archaeologically relevant materials that had been buried for thirty-three years in one of the experimental earthworks in England UK. Examples from the soil biology and fertility literature are discussed to illustrate the effects of fluctuations in soil wetness and aeration, and of nitrogen availability on decomposition. Finally, the impact of soil handling and physical disruption on biological processes in soil are discussed, as they influence whether soil functions can be restored at a reburial site once the archaeological resources have been ‘protected’ beneath.     

Selected physical parameters to characterize the state of preservation of waterlogged archaeological wood: a practical guide for their determination

Non-destructive and destructive methods for determining the physical parameters of waterlogged wood such as the porosity, the water content, the wet and dry bulk densities plus the density of the cell wall material are presented. Considerations in respect to determination of masses, volumes and sampling size are discussed.     

Ancient DNA in archaeological wheat grains: preservation conditions and the study of pre-Hispanic agriculture on the island of Gran Canaria (Spain)

The recovery of ancient DNA from archaeological wheat samples under different preservation conditions was assessed using a number of genetic markers. It was possible to amplify nuclear DNA from desiccated grains but not from charred. The desiccated grain was from a pre-Hispanic grain silo in Gran Canaria and showed excellent DNA preservation, enabling the amplification of the ribosomal DNA markers IGS and ITS, the upstream region of the HMW-glutenin locus and single-locus nuclear microsatellites. Our results demonstrated the presence of both durum and bread wheat in an assemblage of naked grain. We were also able to identify different genotypes in durum wheat and compare these with extant landraces, providing insights into the agrarian practices of the ancient Canarians and the origin of their crops.     

Mapping by matching: a computer vision-based approach to fast and accurate georeferencing of archaeological aerial photographs

To date, aerial archaeologists generally apply simple rectification procedures or more expensive and time-consuming orthorectification algorithms to correct their aerial photographs in varying degrees for geometrical deformations induced by the topographical relief, the tilt of the camera axis and the distortion of the optics. Irrespective of the method applied, the georeferencing of the images is commonly determined with ground control points, whose measurement and identification is a time-consuming operation and often limits certain images from being accurately georeferenced. Moreover, specialised software, certain photogrammetric skills, and experience are required. Thanks to the recent advances in the fields of computer vision and photogrammetry as well as the improvements in processing power, it is currently possible to generate orthophotos of large, almost randomly collected aerial photographs in a straightforward and nearly automatic way. This paper presents a computer vision-based approach that is complemented by proven photogrammetric principles to generate orthophotos from a range of uncalibrated oblique and vertical aerial frame images. In a first phase, the method uses algorithms that automatically compute the viewpoint of each photograph as well as a sparse 3D geometric representation of the scene that is imaged. Afterwards, dense reconstruction algorithms are applied to yield a three-dimensional surface model. After georeferencing this model, it can be used to create any kind of orthophoto out of the initial aerial views. To prove the benefits of this approach in comparison to the most common ways of georeferencing aerial imagery, several archaeological case studies are presented. Not only will they showcase the easy workflow and accuracy of the results, but they will also prove that this approach moves beyond current restrictions due to its applicability to datasets that were previously thought to be unsuited for convenient georeferencing.     

Southwest Scottish Crannogs: using in situ studies to assess preservation in wetland archaeological contexts

This paper presents the results of in situ monitoring of waterlogged burial contexts in southwest Scotland. The sites investigated are Iron Age crannogs (lake dwellings) which have a proven waterlogged archaeological component, and which are being assessed as part of a national program of study by the Scottish Wetland Archaeology Programme (SWAP) team. A monthly monitoring program commenced in July of 2004. To date, monitoring of water levels, pH, and redox potential, has been undertaken for a period of 17 months in order to encompass any seasonal variability at the sites studied. The results have proven robust in that an ‘ideal’ site for in situ preservation has been identified from the five sites investigated, and the monitoring has highlighted external variables and seasonal impacts that have the potential to influence the long-term in situ preservation at the remaining sites studied. In general, these results have expanded upon our knowledge of the potential for the preservation of existing archaeological remains within such contexts. This study represents the first stage of monitoring aimed at developing a holistic understanding of in situ conditions at the crannog sites studied in southwest Scotland.     

Discerning use-related micro-residues on tools: testing the multi-stranded approach for archaeological studies

In this paper I explore how post-depositional contaminants and non-use related ancient residues may be distinguished from use-related residues directly associated with the application of ancient artefacts. It is assumed that contaminant and unintentional remains have a random distribution over a tool’s surface. Preserved use-related residues, however, are expected to have a consistent spatial distribution around a working edge. To test this, residues on used and unused experimental flakes were recorded after they underwent weathering. The surfaces of the experimental flakes were divided in four quadrants, of roughly equal size. The surface coverage of the residue types per quadrant was then recorded. On used flakes with well preserved residues, the use-related residues are more abundant on portions associated with the sharp edge than on portions associated with blunt sides. On the samples without identified use-related remains and on the unused sample, the distribution of micro-remains is more uniform. This study confirms that by using a contextual approach it is possible to distinguish use-related remains from non-use-related and co-incidental remains.     

UNCSTD: 'geoperspective' of a multidisciplinary commission

Abstract

The term 'safety critical' applies to a wide range of technologies, from car braking systems, through trains and their signalling systems, to advanced air and space technology, both civil and military. It is a rather sophisticated euphemism for 'dangerous';and like the word 'safe', it suggests the existence of some spectral but inherent property beneficial to human health that could be lost under certain conditions, but does not have to be. How far can the discourse about safety be trusted?And why are debates about risk sometimes so heated?In this paper it is proposed that literary theory, particularly work on 'deconstruction' by philosopher Jacques Derrida, can shed some light on these questions. Unsurprisingly, deconstruction cannot say much to safety engineers about the technicalities of system building. But then again questions about whether and why we continue to build and rely upon safety critical technologies are not simply technical; the language used in them is almost always politically charged.