Monitoring the burial environment of terrestrial wet archaeological sites in The Netherlands

Abstract

Monitoring the burial environment of archaeological sites is necessary to assess the success of their preservation in situ. Also, monitoring the state of preservation of actual archaeological remains together with that of their burial environment will further our understanding of the degradation processes acting on archaeological remains in situ. These remains consist not only of objects made from wood, metal, stone, etc., but also of pollen, soil features and even micromorphological features. Although, to date, the precise degradation mechanisms of archaeological remains in situ are not yet fully understood, general agreement exists on which parameters should be monitored in wet terrestrial environments. Also, it has been established that in situ measurements are preferable to laboratory analyses of soil (water) samples. In practice, it is difficult to find suitable monitoring equipment for in situ measurement as it must meet many requirements: an in situ measuring principle; stable for a period of at least several months; robust for use in the field; and equipped with a datalogger. A suitable principle exists for measuring the redox potential, however a simple, robust field instrument with datalogger is not yet available. Monitoring of the water table level, temperature and oxygen content is possible with recently developed, commercially available instruments. Monitoring of acidity is less complex as it does not vary as rapidly as, for example, the redox potential; however, the recommended method is still based on analysing soil samples, which is not acceptable in the long term at archaeological sites.     

Reburial of shipwrecks in marine sediments: a long-term study on wood degradation

Historical shipwrecks in marine environments are continuously decomposed by wood-degrading organisms, adapted to this specific environment. To protect the wrecks from degradation and to preserve the unique remains for future generations, reburial of wrecks using various covering materials has been suggested as a long-term preservation method. The following experiment was carried out to study the bio-protective effect of sediment. Sound oak, pine, and birch samples were buried above and within marine sediment in Marstrand harbour, and retrieved for analysis after 6, 12, 24, and 36 months. Macroscopic as well as light-microscopic examinations were carried out on each occasion. Marine borers (shipworm, Limnoria), soft rot and tunnelling bacteria were wood degraders immediately above the seabed; soft rot, tunnelling bacteria, and erosion bacteria were active 10 cm below the seabed; erosion bacteria were the only degraders at a depth of 43 cm below the seabed. The wood species had different durability towards the decay agents. After 3 years, wood samples above the seabed were totally decomposed, whereas wood was highly protected at 43 cm depth in sediment. In the sediment, decay decreased significantly with depth of burial. The results suggest that reburial of shipwrecks in marine sediment can be recommended as a simple and efficient method for long-term preservation of the wooden cultural heritage.     

Quantification and Visualization of In Situ Degradation at the World Heritage Site Bryggen in Bergen,Norway

Abstract

Environmental monitoring at the World Heritage Site of Bryggen in Bergen, Norway, has shown damaging settling rates caused by degradation of underlying archaeological deposits. Measurements of piezometric head, oxygen, and soil moisture content, as well as chemical analyses of water and soil samples are key elements of the environmental monitoring.

Groundwater monitoring and geochemical analyses reveal a complex and dynamic flow through the natural and anthropogenic stratigraphy. The preservation conditions within the organic archaeological deposits are strongly correlated with oxygen and soil moisture content, that are controlled by the groundwater flow conditions at the site. To quantify decay rates, it is thus essential to understand the wider hydrogeological context of the site. This paper presents recent advancements in quantifying decay rates in the saturated zone at Bryggen. The paper also shows that 3D geo-archaeological modelling can contribute to preservation management by visually combining results of geological, archaeological, geochemical, and hydrological investigations. This opens up for improved multidisciplinary understanding of preservation potential, thereby contributing to an improved protection of archaeological deposits in situ.     

Monitoring and Modelling Saturation as a Proxy Indicator for in situ Preservation in Wetlands—a GIS-based Approach

The unifying nature of water on the preservation of organic archaeological and palaeoenvironmental source material within wet deposits is well recognized. It is also understood that, while the preservation of such deposits is fundamental towards our understanding of the past, in many areas de-watering through agricultural drainage and water abstraction is degrading them. Within the framework of preservation in situ such environments present considerable challenges. Fundamentally, the environmental dynamics of wetlands, not least of water, mean that they must be monitored carefully in order to understand the condition of the burial environment and thereby the likely preservation potential. This paper presents an approach to monitoring the saturation of the burial environment and modelling this data using a geographical information system (GIS). It demonstrates a method aimed at modelling the conditions of current preservation, and predictively modelling the conditions for long-term, in situ preservation in order to provide a baseline for resource management. It is shown that the quantification of saturation is possible and advantageous in the management of dynamic wetland environments.     

Take the Right Decision Everybody

Abstract

The archaeological deposits in medieval towns are among the most important and distinctive heritage monuments in Norway. At the same time they are among the more challenging phenomena confronting heritage management authorities, municipal planners, and property owners/developers alike, especially in relation to building and infrastructure projects. The modern settlement has developed on top of medieval and younger deposits which means that not only are they an irreplaceable depository of historical information, but they also form a significant part of the modern town’s physical foundation.

Since 2002 the Directorate for Cultural Heritage in Norway (Riksantikvaren) has been funding systematic monitoring of archaeological deposits of the World Heritage Site Bryggen in Bergen. The monitoring programme consists of several approaches: archaeological assessment of the deposits state of preservation, biochemical investigation of preservation conditions within the deposits, hydrogeological mapping of the water table, water flow, and other given parameters.

Continuous systematic monitoring by using testable, replicable methods and measures, data, and results acquire increased quality and validity. These in turn provide the cultural heritage management with a toolbox for making correct decisions and thereby allow the government’s preservation targets to be attained. But, most important, it guarantees the preservation of the ‘underground archives’ and at the same time allows the urban centres to develop.

This paper presents the knowledge developed through monitoring the Bryggen site as a basis for an official Norwegian standard covering archaeological, biochemical, and hydrogeological deposit investigations.     

Changes in the Physico-Chemical and Microbial Nature of Wetlands from the Leaching of Chromated Copper Arsenate (CCA)-Treated Wood

Abstract

Microbial activities are responsible for reducing the harmful effects of pollutants in different burial environments. Within wetlands in particular, microorganisms play an important role in the transformation of heavy metals and metalloids via direct or indirect oxidation/reduction. In turn, these microbial transformations can lead to the detoxification of pollutant elements such as copper, chromium and arsenic that comprise CCA-treated wood.

CCA was the most commonly used wood preservative in the UK (up until its partial ban in 2004). CCA prolongs the service life of wood by making it resistant to microbiological attack. As such, it has been regularly used in the construction of platforms and boardwalks in wetlands. However, recent concerns over the impact of the chemical constituents of this treatment on both the environment and human health have prompted the introduction of legislation in order to ensure that this type of treated wood is disposed of in accordance with the relevant health and safety guidelines.

In light of this information, it is important to assess changes in the physico-chemical and microbial nature of wetlands associated with the leaching of CCA from wooden structures. The results will not only provide a greater scope for understanding the implications associated with the in situ preservation of the archaeological resource contained within these environments, but also highlight the potential ramifications for wetland ecosystem dynamics.     

In situ Preservation Solutions for Deposited Iron Age Human Bones in Alken Enge,Denmark

The rich mass deposition of Iron Age human bone material from the Danish site, Alken Enge, is extraordinary not only from an archaeological perspective but also from a preservation point of view. The main find is situated in a waterlogged, anoxic environment which provides excellent preservation conditions and therefore enables in situ preservation of the human bones. However, major differences in local environmental conditions challenge an in situ preservation of the entire site area as parts of the bone material presently deteriorate. In this paper, a multi-proxy environmental monitoring approach is used to document threats and to suggest the best preservation solution for the archaeological finds, whether in or ex situ.     

On the challenges and benefits of indoor archaeology: 15 years at the Archeodome (Mitchell Prehistoric Indian Village,South Dakota)

Abstract

Field archaeology is normally associated with outdoor excavation and exposure to the natural environment. Archaeological excavations have adapted to a wide spectrum of these conditions, but the recent prominence of archaeological sites as tourist attractions and educational facilities has occasionally led to dramatically different environments for the archaeological recovery, interpretation, and preservation of evidence, including facilities that permit indoor excavation. This article explores 15 years of experience at the Mitchell Prehistoric Indian Village in South Dakota. An “Archeodome” covering part of the site represents a non-traditional excavation and preservation environment that presents considerable benefits and challenges for archaeologists. The structure provides the basis for evaluating the nature of indoor excavation within its archaeological and educational context and provides a cautionary note for archaeologists, heritage groups, tourist boards, and others interested in the preservation of archaeological sites. Though this article focuses on the Mitchell site, the information reported has broad implications for sites where structures cover archaeological deposits.     

The Future Preservation of a Permanently Frozen Kitchen Midden in Western Greenland

Abstract

Archaeological materials may be extraordinarily well preserved in Arctic areas, where permanently frozen conditions in the ground slow down the decay of materials such as wood, bone, ?esh, hair, and DNA. However, the mean annual air temperature in the Arctic is expected to increase by between 2·5 to 7·5°C by the end of the twenty-?rst century. This may have a signi?cant warming effect on the soil and could lead to permafrost thaw and degradation of currently frozen archaeological remains. Here we present a four-year monitoring and research project taking place at Qajaa in the Disko Bay area in West Greenland. Qajaa is a large kitchen midden, containing frozen remains from 4000 years of inhabitation, from when the ?rst Palaeo-Eskimos entered Greenland, until the site was abandoned in the eighteenth century. The purpose of the project is to investigate current preservation conditions through ?eld and laboratory measurements and to evaluate possible threats to the future preservation.

Preliminary results show that the archaeological material at Qajaa is still very well preserved, but some microbial decay is observed in the exposed wooden artefacts that thaw every summer. Maximum temperatures are above 0°C in the upper 40–50 cm of the midden and between 0 and ?2°C down to 3 m depth. Thereby the permafrost may be vulnerable to quite small increases in air temperatures. Laboratory measurements show that the decay of the archaeological wood in the midden is temperature-dependent, with rates increasing 11–12% every time the soil temperature increases 1°C. Moreover, the soil organic material produces heat when decomposed, which could have an additional warming effect on the midden. At the moment the water or ice content within the midden is high, limiting the subsurface oxygen availability. Threats to the future preservation are related to further thawing followed by drainage, increased oxygen availability, microbial decay of the organic material, and heat production.     

Laboratory Research on the Effects of Heavy Equipment Compaction on the in situ Preserved Archaeological Remains

Following the Malta Convention/Valletta Treaty the preferable way for the physical protection of archaeological sites is in situ preservation. When planning in situ preservation, in addition to other issues, it is also necessary to consider changes in physical environment and their impact on in situ preserved remains. This is especially important when human interaction takes place. Recently, an increase in construction on the top of archaeological sites has occurred, thus the effects of heavy equipment compaction need to be studied in more detail.

This paper presents research on the effects of the use of heavy equipment (e.g. rammers and rollers) compaction on archaeological remains. For the purpose of our research, laboratory testing has been performed. In a custom-made steel box, artificial archaeological sites were created using layers of sandy silt and gravel. A variety of archaeological and modern artefacts were placed in these created environments. Some of them were equipped with strain gauges for deformation recording. Through a series of tests a servo-hydraulic piston was used, which simulated the dynamic loading of the artificial sites. Humidity and temperature were recorded before, during, and after each test. Since layers and artefacts were three-dimensionally recorded before and after each test, compaction of layers and movements of artefacts could be studied. With attached strain gauges and visual inspection following each test, deformations and thus damage to artefacts during different stages of loadings was recorded.

The goals of our laboratory tests were the development of a new methodological approach to study the effects of heavy equipment compaction to the archaeological sites, getting an insight into the problems of such tests, and the estimation of the applicability of their results. With the presented results, our research has been a step towards better understanding the effects of heavy equipment compaction on archaeological remains and thus to the preservation of archaeological sites in situ.     

A Qualitative Approach for Assessment of the Burial Environment by Interpreting Soil Characteristics; A Necessity for Archaeological Monitoring

Abstract

Modern-day archaeological monitoring is often hampered by lack of money, lack of time, inadequate measuring equipment, and lack of insight in the conservation potential of a site.

Although in modern archaeological excavations soil characteristics are noted (colour, texture, groundwater level, and sometimes mineralogy), these characteristics are mainly used for the interpretation of a site. However, by looking to these characteristics from a conservational view eventually combined with the conservation status of the archaeological objects, much can be learned about the burial environment. This is essential for optimizing archaeological monitoring.

Degradation processes result from the change of reactive phases in the soil or the site. Reactive phases are soil components such as organic matter, sulfides, iron(hydr)oxides and carbonates (chalk, shells), and, if present, components in the ground or interstitial water such as hydrogen ions and sulphate. The presence of these phases can easily be established by the archaeologist or soil scientist in the field. We propose a simple field-based method for assessing degradation processes essential for in situ preservation and monitoring.     

Preservation of fungi in archaeological charcoal

During the analysis of wood charcoal remains from archaeological sites, it is common to find different microorganisms and different forms of degradation present in the plant tissue. However, one may encounter difficulties when attempting to identify these microorganisms and determine when their attack occurred. This paper focuses on preservation aspects related to the microorganisms in wood and demonstrates the structural changes that take place in different types of decayed wood after it was converted into charcoal. The study seeks to determine whether the microbial attack found in archaeological woods took place before the burning of the wood or after. Burning experiments were conducted using wood that had been decayed by various types of fungi including white-rot, brown-rot, and soft-rot. The laboratory burnt wood samples showed decay patterns that were comparable to those observed in archaeological charcoal samples, indicating that signs of fungal infestation and features of decay can be preserved after burning with micromorphological details of mycelium and cell wall attack evident. This indication may provide important information related to the gathering of deadwood as fuelwood. In addition, examples of decayed wood preserved in archaeological charcoal assemblages are described. Their relationship to the archaeological context and environmental conditions may suggest different interpretative models concerning wood management strategies applied by past societies.     

Eco-Archaeometry: Interdisciplinary Applications in Egypt

Abstract

One of the problems currently faced by modern society is the worldwide catastrophic deterioration of archaeological and cultural sites directly exposed to the action of the environment. Frequently, it has proved difficult to identify the processes responsible for these deteriorations, which are often the result of an abrupt change in site specific environmental conditions. To understand them a broad interdisciplinary approach is needed, and consequently, a substantial input from several disciplines, such as archaeology and archaeometric, environmental and conservation sciences, is necessary. Such interaction is particularly necessary on a basic research level, and can best be achieved if the relevant disciplines are drawn together a priori on equal footing into a complementary effort in eco-archaeometry. The primary goal of eco-archaeometry is to identify and quantify physicochemical processes which cause the deterioration of ancient cultural patrimony. Its findings are essential prerequisites for the development of optimum, safe methods for conservation and preservation of ancient monuments. Some examples of the eco-archaeometric approach in Egypt are summarised and it is demonstrated that without an interdisciplinary approach such studies would not have been successful.     

Reburial and Analyses of Archaeological Remains in the Marine Environment — Investigations into the Effects on Metals

Abstract

The treatment and long-term storage of recovered cultural material from underwater heritage sites is becoming less cost effective, and reburial of archaeological sites and the associated artefacts in the marine environment is becoming increasingly common practice in managing the submerged cultural resource. Following recent large-scale underwater archaeological excavations in Marstrand harbour, Sweden, the majority of recovered finds were reburied in defined trenches in the harbour sediment. Subsequently, the Studio of the Western Sweden Conservators in conjunction with the Bohus County Museum initiated a fifty-year research project to evaluate reburial as an appropriate method of preserving waterlogged archaeological artefacts in the long term. The research project, entitled ‘Reburial and Analyses of Archaeological Remains’, was launched in 2002 and consists of six sub-projects. The main aims of these sub-projects are to analyse the extent of deterioration of the most common material types found on underwater archaeological sites, assess the stability of packing and marking materials used in archaeological documentation, and monitor the reburial environment.

The aim of the metals sub-project is to investigate the short- to long-term corrosion behaviour of metals buried in the marine environment by examining the deterioration of reburied and exposed modern metal coupons and eventually compare these results to the analysis of actual shipwreck artefacts. The environmental monitoring sub-project is designed to complement the other sub-projects by assessing the physico-chemical changes occurring in the reburial environment over time and the effect on the deterioration of the different reburied material types. In comparing the results obtained over the past seven years from both the metals and monitoring sub-projects, it should be possible to more accurately evaluate the effectiveness of reburial as a long-term in situ preservation strategy for metallic archaeological remains.     

The unification of archaeological sites of Athens: The birth of an archaeological park?

Abstract

Recently, there has been a growing trend to present archaeological resources in the form of archaeological parks. These are an innovative way of presenting vast archaeological sites that contain a number of monuments, as a single entity, using components of the environment as interpretation features and creating an ‘invented’ integrity of the landscape. Even though the overall concept of an archaeological park emerged in Scandinavia at least three decades ago, only recently has it taken on a wider character and been applied to a variety of archaeological sites. But no clear criteria exist for them.

The current project of the Unification of the Archaeological Sites of Athens involves creating an archaeological park that includes most features considered essential for a park of this kind. However, the special characteristics of Athens (the over-built urban landscape, environmental pollution, and the mystical relationship between the ancient and modern cities), give the future park a rather individual character.     

Flotation versus dry sieving archaeobotanical remains: A case history from the Middle Horizon southern coast of Peru

Abstract

During excavations at the site of Casa Vieja located in the Peruvian coastal desert, archaeological plant remains were systematically collected to assess whether it is more productive and informative to sieve sandy sediments in dry environments or to process such samples by water flotation, a persistent methodological concern. At Casa Vieja, dual subsamples were collected and analyzed using both of these procedures. For dry, sandy sediment conditions, each processing strategy was found to yield a different view of the botanical remains. Dry sieving recovers more of the larger plant specimens whereas water flotation yields more of the smaller-sized material. These results should be incorporated into archaeological research designs in the future, especially for desert environments.     

A Ticking Clock? Preservation and Management of Greenland’s Archaeological Heritage in the Twenty-First Century

ABSTRACT

Evaluating the rate of deterioration at archaeological sites in the Arctic presents several challenges. In West Greenland, for example, increasing soil temperatures, perennial thaws, coastal erosion, storm surges, changing microbial communities, and pioneer plant species are observed as increasingly detrimental to the survival of organic archaeological deposits found scattered along the country’s littoral zones and extensive inner fjord systems. This article discusses recent efforts by the REMAINS of Greenland project for developing a standardised protocol that defines the archaeological state of preservation, the preservation conditions, and asset value of organic deposits. Special emphasis is given to the degradation of materials such as bone and wood that are historically observed to be well-preserved in Greenland but now currently at risk. The protocol provides a baseline for monitoring future changes and will assist archaeologists in Greenland with a procedure for documenting and predicting areas of increasing vulnerability due to a warming climate.     

The potential of chironomid (Insecta: Diptera) larvae in archaeological investigations of floodplain and lake settlements

The head capsules of chironomids (Insecta: Diptera) are well preserved in sediments and can be recognised to a high taxonomic level, usually genus and sometimes species. Work on lake sediments has shown that they can be accurate indicators of water temperature, oxygen regimes, and nutrient status (particularly total phosphorus and chlorophyll-a), as well as heavy metal pollution. No systematic chironomid analyses, however, have previously been undertaken on archaeological deposits. In order to address this we assessed the use of chironomids in three types of archaeological deposit; firstly, a lake core at the edge of a lake settlement (crannog), secondly, a palaeochannel infill adjacent to a multi-period settlement site and lastly, a Roman well deposit from a floodplain environment. The chironomid assemblages are shown to vary significantly both between and within the sites and reflect the immediate environment and the adjacent area. The lake sediment assemblage reflects the construction of the crannog through elevated levels of organic detritus, wood and woody debris. The palaeochannel assemblage reveals changing natural conditions and nutrient enrichment probably associated with settlement during the Saxon period. The well assemblage is taxonomically restricted and indicative of organic debris, dead plant material, animal dung and possibly human effluent deposited after abandonment of the well. Dry storage of the palaeochannel and well sediments for several years did not appear to affect the concentration or state of preservation of the head capsules. The chironomid reconstructions are shown to provide an additional indicator of human activity which has the potential to provide quantitative data on the character of aquatic environments associated with archaeological sites.     

Evaluation of the rate of wood degradation at the Iron Age archaeological site of Biskupin,Poland

A study was made of the degradation of archaeological Scots pine (Pinus sylvestris L.) at the Iron Age archaeological site of Biskupin, Poland. Wood degradation was evaluated after 10 years of deposition of samples in different burial conditions (mineral soil, peat and water) and at different depths (25, 50 and 100 cm) at the location of the original archaeological wood from the Lusatian culture settlement. Changes in the wood samples were assessed on the basis of selected physical (maximum water content, basic density and porosity) and chemical (chemical composition, structure of cellulose and lignin) properties. The observed degradative changes were different for samples deposited in different locations of the archaeological site and at different depths. They relate mainly to carbohydrates—both cellulose and hemicelluloses—although the structure of lignin also underwent changes. The experiment using wood that had been degraded to a similar degree to the Biskupin wood enabled identification of the actual danger of degradation of the latter. It was found that the remains of the wooden structure of the Biskupin settlement are degrading, despite the favourable physicochemical conditions prevailing at the site, and it is necessary to take measures to prevent its further decomposition.     

Determining the preservation rating of submerged archaeology in the post-glacial southern North Sea: a first-order geomorphological approach

Abstract

During most of the last glaciation, the southern North Sea floor was exposed and accessible to humans. Archaeological finds are concentrated around Brown Bank, Dogger Bank and the Norfolk Banks, but the Palaeolithic and Mesolithic archaeological potential of these areas is poorly known. Management of submerged archaeological heritage requires knowledge about location (potential) and context, ascribing significance (value) and determining risk. Thus, the preservation potential of primary and secondary archaeological material around these three areas is considered a) in the context of the post-glacial evolution of the southern North Sea and b) regarding natural and anthropogenic processes. A detailed review is followed by original research material describing an approach to assessing preservation potential. In general, low-energy deposits associated with former intertidal, floodplain or lacustrine environments are likely to preserve primary archaeological material, including organic remains, whilst (high-energy) riverine environments are more likely to preserve inorganic secondary archaeological material. The main possible anthropogenic impacts on submerged archaeology result from beam trawling, which may disturb deposits at the seafloor, and aggregate dredging, which may remove secondary deposits. Trawling and aggregate dredging are increasingly contributing to knowledge, through reporting finds through established protocols, and through assisting in funding relevant to multi-disciplinary research.