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.     

Mineral weathering in forest soils and its relevance to the preservation of the buried archaeological resource

There is more woodland in Britain now than for many centuries and considering many international climate change mitigation policies, woodland cover, both in Britain and internationally, is being promoted. However, neither the management of existing woodlands nor their expansion should be at the expense of important archaeological evidence. Due to the large number of known archaeological sites, the large areas of land with uninvestigated archaeological potential and the expanding woodland cover, suitable mitigation strategies need to be developed to allow preservation in situ of important sites. An understanding of how woodland soils and the buried archaeological resource interact is, therefore, essential. This paper utilises ongoing environmental research into the mineral weathering rates in forest soils and considers its application to artefact preservation. The study concludes that soil water pH, its movement, and the saturation of dissolved ions in the soil solution are major factors determining both mineral and artefact longevity. A simple guide to artefact longevity based on these properties is proposed and a geochemical model for predicting loss is tested. These tools could be applied to any soil or individual horizon irrespective of land-use.     

Bone diagenesis in the European Holocene II: taphonomic and environmental considerations

We have applied cluster analysis to mercury intrusion porosimetry data from 219 archaeological bones (121 human and 98 animal) and soil chemistry data from 219 accompanying soil samples (1 per bone sample), to investigate the influence of soil chemistry on bone preservation. The samples chosen for the study were obtained from sites ranging in time from the pre-modern to the Mesolithic and were representative of burial environments across Europe (from the Baltic to the Mediterranean). These results represent the single largest database for archaeological bone preservation in the European Holocene to date and demonstrate the potential for large-scale diagenetic studies to help develop long term preservation strategies for our European heritage. Despite the variety of sites and environments, bones could be categorised into only four main diagenetic types. Furthermore, soil chemistry appears to significantly affect only one type of preservation, the pathway characterised by loss of mineral. In neutral to basic soils, taphonomy and in particular the differences between the treatment of human and animal remains, becomes the dominating factor in determining preservation. Using these results, strategies for heritage management of archaeological sites can be suggested; grouping sites into those requiring immediate excavation and those where in situ preservation is viable.     

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.     

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.     

Archaeological evidence of intestinal parasites from coastal shell middens

Shell midden sediment from Canada's Pacific coast has yielded consistent and quantifiable evidence of human intestinal parasitism. Auger samples from pre-contact settlements have produced evidence of as many as four parasite genera, including fish tapeworm (Diphyllobothrium spp.) and human roundworm (Ascaris lumbricoides). The methods of parasite extraction were non-complex, replicable and non-invasive. This project demonstrates the practicality of soil testing throughout a range of archaeological features and encourages the standard curation of culturally deposited soils for the purpose of archaeoparasite recovery.     

Sedimentological and archaeological fabrics in Palaeolithic levels of the South-Eastern Pyrenees: Cova Gran and Roca dels Bous Sites (Lleida, Spain)

The comparative study of sedimentary fabrics in relation to archaeological fabrics in various levels of the sites of Cova Gran de Santa Linya (Middle and Early Upper Palaeolithic) and the Roca dels Bous (Middle Palaeolithic) has made it possible to analyse the formation dynamics of the deposits and determine the extent of disturbance of the archaeological levels by natural processes. To achieve this, diagrams and two- and three-dimensional indices were calculated from the azimuth and dip angle of natural clasts and artefacts. The results indicate that the sedimentary levels were formed mainly by planar fabric shape gravitational processes (low depositional angles), which differ notably from the archaeological fabrics they contain, characterised by a greater degree of isotropy. This difference in the fabrics would reflect human activity and indicates that the archaeological levels both in Cova Gran and Roca dels Bous have not been subject to significant natural modifications, and are preserved in situ.     

Deep Impact: What Happens When Archaeological Sites are Built on?

Abstract

Increasingly, developers and archaeologists search for ways to build on archaeological sites, while at the same time preserving the remains underneath. However, deciding which effects of construction on archaeological sites are acceptable and which are not is hampered by the lack of knowledge on the impacts of construction on archaeological sites. This paper provides an update on some of the effects of building on archaeological sites. Recent research had shown that displacement piles cause less disturbance in soft soils than previously thought. Moreover, replacement piles may be less benign that assumed up till now. Effects of loading on archaeological sites are described, and gaps in the knowledge on these effects are indicated. More research is needed in this field, especially on predicting soil disturbance and damage to weak materials. Impermeable surfaces and constructions on top of sites may affect the visibility of soil features due to decreased rainwater infiltration. Finally, a series of non-physical effects are mentioned that will have to be taken into account when deciding on allowing building on archaeological sites.     

Variation in collagen stable nitrogen values in black-tailed jackrabbits (Lepus californicus) in relation to small-scale differences in climate,soil, and topography

Longstanding observations about the relationship between increasing aridity and ¹⁵N enrichment in mammalian collagen values have led to an interest in their use as a paleoclimatic marker. Here we report on variability in collagen nitrogen values from five modern and two archaeological samples of black-tailed jackrabbits (Lepus californicus) from the eastern Great Basin of the United States (N = 178 individuals). Nitrogen δ¹⁵N values were highly variable within all samples. Modern samples showed significant differences despite similarities in average annual precipitation and temperature. Archaeological samples were indistinguishable from each other or from modern samples taken from the same area despite independent evidence for differences in precipitation for the two prehistoric periods considered. Differences between modern samples were most strongly associated with soil characteristics. We discuss these results in light of their relationship with topography and vegetation and highlight their implications for archaeological applications of stable nitrogen analyses in several contexts.     

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.     

‘I Felt Connected to a Past World’: A Survey of Visitors to Colonial Archaeological Sites Conserved In Situ in Australia and New Zealand

Abstract

While there is extensive international literature on the technology and techniques of archaeological conservation and preservation in situ, there has been only limited discussion of the meanings of the places created and the responses they evoke in visitors. Experience in Australia and New Zealand over the past decade suggests that the conservation of colonial archaeological remains is today seen as a far more desirable option, whereas previously many would have suggested that this kind of conservation was only appropriate in ‘old world’ places like Greece and Italy; and that the archaeology of the colonial period was not old enough to be of value. This paper discusses a recent survey of visitors to colonial archaeological sites which reveals some of the ways in which these archaeological remains are experienced, valued, and understood, and gives some clues as to why conservation in situ is an expanding genre of heritage in this region. The visitors surveyed value colonial archaeological sites conserved in situ for the link they provide to place, locality, and memory; for the feeling of connection with the past they evoke; and for the experience they provide of intimacy with material relics from the past. This emphasis on the affective qualities of archaeological remains raises some issues in the post-colonial context, as it tends to reinforce received narratives of identity and history, and relies on the ‘European’ antiquarian appreciation of ruins — making the urban environment more like Europe by creating evidence of similar historical layering.     

Botanical Archaeology at the Norman P Site in Ohio

Abstract

Continuous prehistoric occupation of northern Ohio from 9000 B.P. to 5000 B.P. has often been questioned. Its demonstration is difficult to support. Stratigraphically intact archaeological evidence for this Late PaleoIndian-Early Archaic period is not common in the eastern United States and is generally found in dry rockshelters or in alluvial bottomlands. In northern Ohio, rockshelters are rare and bottomlands have recently been subjected to deep-plowing. The controlled comparative germination of viable seeds in such recently disturbed strata yields an Index of Plowing which can determine the lower limits of such disturbance in the absence of other pedological or archaeological indications. The application of this Index to the Norman P site in Summit County, Ohio, reveals an intact PaleoIndian-Archaic Transitional occupation.     

A Predictive Map of Compression- Sensitivity of the Dutch Archaeological Soil Archive

Abstract

Weak soils like unconsolidated clay and peat may deform and compress considerably by loading, for example, by sand bodies for roads and railways. Archaeological sites within such easily compressible soil layers may therefore be heavily affected by different kinds of construction works. The vulnerability of archaeological sites to compression is largely dependent on soil properties like lithology, grain-size, and previous loading history. This may therefore differ considerably. Predicting the compression sensitivity is of great value for planners, since they can estimate in which areas in situ protection of archaeological sites may be feasible and where it would require (costly) technical measures or plan adaptations.

As part of the Cultural Heritage Agency’s research programme on construction and archaeology, we prepared predictive maps of the compression sensitivity of the subsurface sediments in the Netherlands for 1 m depth intervals from 0 to 20 m depth.

The maps were constructed using a full 3-D model of the subsurface of the Netherlands.

In combination with the Indicative Map of Archaeological Values (IKAW) that is already available, these maps can be used to better estimate the technical measures needed and costs involved for in situ protection of archaeological sites in the planning phase of construction projects.     

Chemical analyses of organic residues in archaeological pottery from Arbon Bleiche 3, Switzerland – evidence for dairying in the late Neolithic

Fatty acids distribution and stable isotope ratios (bulk δ¹³C, δ¹⁵N and δ¹³C of individual fatty acids) of organic residues from 30 potsherds have been used to get further insights into the diet at the Late Neolithic (3384–3370 BC) site of Arbon Bleiche 3, Switzerland. The results are compared with modern equivalents of animal and vegetable fats, which may have been consumed in a mixed ecology community having agrarian, breeding, shepherd, gathering, hunting, and fishing activities. The used combined chemical and isotopic approach provides valuable information to complement archaeological indirect evidence about the dietary trends obtained from the analysis of faunal and plant remains. The small variations of the δ¹³C and δ¹⁵N values within the range expected for degraded animal and plant tissues, is consistent with the archaeological evidence of animals, whose subsistence was mainly based on C₃ plants. The overall fatty acid composition and the stable carbon isotopic compositions of palmitic, stearic and oleic acids of the organic residues indicate that the studied Arbon Bleiche 3 sherds contain fat residues of plant and animal origin, most likely ruminant (bovine and ovine). In several vessels the presence of milk residues provides direct evidence for dairying during the late Neolithic in central Europe.     

Baseline bioavailable strontium isotope values for the investigation of residential mobility and resource-acquisition strategies in prehistoric Cambodia

Strontium (Sr) isotope ratios (⁸⁷Sr/⁸⁶Sr) measured in human skeletal material can increase one's understanding of the residential behaviour and resource-acquisition strategies of past populations. The paper maps bioavailable ⁸⁷Sr/⁸⁶Sr variation in 183 plant and soil samples across Cambodia. Bioavailable ⁸⁷Sr/⁸⁶Sr, as measured in plants, differs significantly between four major geological units. The data set will support future investigations of skeletal material from Cambodian archaeological sites. Baseline ⁸⁷Sr/⁸⁶Sr data should be applied judiciously to skeletal populations, and in concert with other lines of evidence, to identify potential geographical outliers rather than to ascribe specific locations from which individuals may have moved.     

Making Better Use of Monitoring Data

This paper addresses the knowledge gap that exists in relation to understanding and quantifying the sensitivity of organic-rich archaeological deposits with respect to changes in the soil environment. Based on two case studies we demonstrate that it is possible to quantify the current decay rate in unsaturated archaeological deposits by combining decay rates measured in the laboratory with on-site monitoring data in a simple decay model. The decay of organic archaeological deposits is highly sensitive to variations in soil temperatures and soil water content. Measurements of soil water content cannot always stand alone as a representative measurement of oxygen availability; which suggests that in situ measurements of oxygen content or redox potential are needed in order to understand the preservation conditions at a site. The results of this study emphasize the advantage of combining monitoring data with laboratory studies, in order to document in more detail where and when degradation takes place.     

Stratigraphy and geochronology of La Playa archaeological site,Sonora, Mexico

La Playa archaeological site in northern Sonora, Mexico contains a long record of human activity that includes the Paleoindian period (terminal Pleistocene) and much of the Holocene. The size and complexity of La Playa has discouraged a systematic characterization of its stratigraphy and geochronology, a deficiency we redress in the study. We distinguished seven stratigraphic units ranging in age from >44,570 to 400 cal yr B.P. using ¹⁴C dates from charcoal and terrestrial gastropods found mostly in archaeological features. All of the buried (in situ) cultural remains are contained in Units B (4690–1580 cal yr B.P.) and C (1010–400 cal yr B.P.) and represent overbank deposition from the nearby Rio Boquillas. Occupation at the site peaks in Units B₄ and B₅, corresponding to the Cienega phase (2800–1800 cal yr B.P.) of the Early Agricultural period. This period coincides with the growth of early agricultural villages in the region and is marked at La Playa by thousands of archaeological features including roasting pits, human burials, and extensive canal irrigation systems. The presence of semi-aquatic and aquatic snails demonstrates that water was present year round in the canal systems constructed during this period. Stable and radiometric isotopic evidence suggests that early agriculturalists diverted ground water over several kilometers from the nearby Rio Boquillas. The extensive Cienega phase occupation ended after about 1700 cal yr B.P. with deep erosion of the site, an event also visible in alluvial records in southern Arizona that marked the end of the Early Agricultural period and significant changes in settlement organization in the region.     

Deciphering the inorganic chemical record of ancient human activity using ICP-MS: a reconnaissance study of late Classic soil floors at Cancuén,Guatemala

Inorganic chemical analysis of soil floors using inductively coupled plasma-mass spectrometry (ICP-MS) was undertaken to provide information on the nature and location of past human activity in the ancient Maya city of Cancuén, Guatemala. The use of ICP-MS to detect trace and ultra-trace elemental enrichment of two excavated soil floors from the late Classic period is the first study of its kind in Mesoamerican archaeology. Geochemical background of the site was established by the analysis of palaeosols and nearby undisturbed ‘off-site’ soil profiles. Robust statistical methods used in the study clearly distinguished the level of anthropogenic enrichment across the former floors. Many elements measured showed only minor departures (10–20%) from the site's background soil chemistry. The greatest levels of elemental enrichment were detected in the rare earth elements, mercury, and gold. The latter is of particular interest considering the consensus that gold was absent from the world of the Classic-period Maya. Comparisons of the spatial pattern of mercury enrichment with lithic and archaeological data show strong linkages to past industrial and ritual activities. Elevated rare earth element concentrations were recorded broadly across both soil floors and are considered to be related to concentrated human occupation in antiquity.     

The impact of manuring on nitrogen isotope ratios in cereals: archaeological implications for reconstruction of diet and crop management practices

Recent archaeological studies of human diet have used stable nitrogen isotope ratios (δ¹⁵N) from human bone collagen to infer the relative importance of terrestrial plant and animal foods. This approach is based on widely observed enrichment of δ¹⁵N up the food chain, plants having distinctly lower values than the herbivores that consume them. Studies of early farming diets in Britain, Denmark and Germany have tended to detect relatively high δ¹⁵N values (e.g. c. +9‰), interpreted as evidence of a diet largely based on animal products, though archaeobotanical evidence for crop cultivation (e.g. carbonised cereal grain and chaff) is widespread. This paper investigates the impact of manuring on δ¹⁵N values in modern cereals, and of charring on these cereal values. The results from two long-term experiments demonstrate that manuring significantly raises δ¹⁵N in cereal grain and chaff. Depending on manuring levels and frequency, it appears that human diets with a major component of such grain would conventionally be interpreted as indicating a largely animal-based diet or a mixed plant/animal diet. Moreover, preliminary analyses of experimentally charred grain and chaff from manured and unmanured conditions are promising for the extraction of reliable ancient δ¹⁵N values from archaeobotanical cereal remains. The wider implications of these results, and the need for further work, are discussed.     

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.