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.     

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.     

Do geotextiles affect soil biological activity in the ‘reburial’ environment?

Abstract

The effect of five different proprietary geotextiles on the activity of soil micro-organisms (respiration as measured by CO₂ production) has been investigated in model laboratory chambers. The aim was to determine whether geotextiles, used to ‘protect’ archaeological materials during conservation by reburial, influence microbial processes that may promote biodegradation of organic archaeological materials by altering the physical properties of the soil. Four of the geotextiles were composed of either polythene or polypropylene and did not provide substrates for microorganisms. These four geotextiles had no significant effect on microbial activity over a short-term (56 days) burial period. By contrast, one of the geotextiles had a core of wheat straw and coconut fibre bonded in a polypropylene mesh. This geotextile led to increased microbial activity as a result of biodegradation of the straw and fibre core. From a practical point of view, these data suggest that geotextiles that are not themselves readily biodegradable did not enhance biodegradation of other organic material in the short term in the burial environment. If the use of geotextiles offers other advantages, such as providing a marker in the soil or back-fill, or because they facilitate subsequent cleaning and preservation operations, then their use is warranted.     

Development and evaluation of geochemical methods for the sourcing of archaeological maize

Strontium (Sr)-isotope values on bone from deer mice pairs from 12 field sites in the Chaco Canyon area, New Mexico, were compared with isotope values of synthetic soil waters from the same fields. The data indicate that mice obtain Sr from near-surface sources and that soil samples collected at depths ranging from 25 to 95 cm contain Sr that is more accessible to the deep roots of maize; thus, synthetic soil solutions provide better data for the sourcing of archaeological maize. However, the Sr-isotope composition of mice may be more valuable in sourcing archaeological remains of animals such as rabbit, turkey, and deer.     

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.     

Multi-element soil prospection aiding geophysical and archaeological survey on an archaeological site in suburban Sagalassos (SW-Turkey)

In order to take full advantage of the archaeological information contained within buried archaeological sites, it is important to apply an integrative approach combining complementary prospection methods. In this study, geochemical prospection data are combined with archaeological and geophysical survey results on an unexcavated site in suburban Sagalassos (SW-Turkey), with the aim of obtaining better insights into the structural shapes and past functionalities of the area. Spatial and multivariate statistical analyses of the chemical data reveal anomalies of K, P and Zn on a location where archaeological and geophysical results suggest the presence of ceramic producing kilns. These elemental enrichments are thought to result from burning wood or dung as fuel for the detected kilns. In addition, local anomalies of Co, Cr, Fe, Mg, Mn and Ni were found to reflect the working and storage of ophiolitic clays, employed as a raw material for ceramic production. Radiocarbon dating of charcoal in a 2.5 m deep drill core in this zone provides ages between AD 120 and 350 at depths of 50 and 60 cm. Al, As, Ba, Ca, Na, Sr, Ti and Pb are considered geogenic elements in this study. The present study supports the theory that geochemical prospection holds potential as a surveying technique, as it was found that chemical data facilitate the interpretation of structures detected by geophysical and archaeological methods, thereby creating an extra dimension to the interpretation of survey data. The results further argue in favour of using strong-acid extractions and the consideration of a large suite of elements when applying chemical soil survey as an archaeological prospection technique, and highlight the importance of considering site lithology. Multivariate statistics proved to be invaluable in distinguishing anthropogenic from lithological soil patterns.     

Autochthony and orientation patterns in Olduvai Bed I: a re-examination of the status of post-depositional biasing of archaeological assemblages from FLK North (FLKN)

Recent excavations at FLK North (Olduvai Gorge, Tanzania) have produced new information on the orientation of archaeological materials at various levels of the site. This information includes the uniform distribution of material azimuths, which contrasts with previous inferences of highly patterned orientations of materials in the Bed I archaeological sites. Those previous inferences of patterned material orientations are based on Mary Leakey's 50-year-old drawings of artifact and fossil bone distribution, but are not verified by our precise measurements of archaeological objects made in situ. Nor do those previous results agree with the general lack of geological, geomorphological, and/or taphonomic data that would indicate significant post-depositional movement of archaeological materials in the sites. We argue here that Leakey's drawings are incomplete (only portions of each assemblage were drawn) and inaccurate in their representation of the original locations, shapes and orientations of most archaeological specimens. This argument is supported by several important mismatches in object representations between a photograph taken of a small portion of the FLK 22 Zinjanthropus site floor before the removal of the archaeological items, and the sketch of the same area drawn by Leakey. Thus, we conclude that primary orientation data of excavations (i.e., direct measurements taken from items) generated prior to object removal are the only valid indicators of the relative isotropy or anisotropy of these important paleoanthropological assemblages.     

In situ preservation of archaeological bone: a histological study within a multidisciplinary approach

To make preservation in situ a serious option for the management of archaeological sites, research has to be done on the factors affecting conservation of different archaeological materials, including bone. A European project has been started which deals with bone degradation in a multidisciplinary way. The goals of the project are to develop techniques to describe the preservation of archaeological bone, to make a classification of soil environments according to their preservation potential and to detect what factors in the environment of the bone affect its conservation. One technique used in this project to determine the state of preservation of archaeological bone is histology. The relevance of this technique for archaeological heritage management research is discussed.     

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.     

Sampling Design and Inferential Bias in Archaeological Soil Chemistry

The ways and extent to which sampling design influences data collection and archaeological inference is a constant concern for archaeologists. Yet, spatial analyses based on anthrosol chemistry have been less willing to concede this problem and to explore potential solutions. This article reviews the recent literature on soil sampling for spatial studies and then uses an example from prehispanic Honduras to examine how both quantitative and qualitative interpretations of soil chemical patterns can shift when sampling design changes. The results of this study suggest that the principal challenges to selecting an appropriate sampling design are in determining the sample size and density, as well as recognizing and adequately dealing with variation in the soil properties being measured. These findings provide cautionary tales for spatial studies aimed at using soil chemical data to infer activity patterns in the archaeological record.     

GPR and inductive electromagnetic surveys applied in three coastal sambaqui (shell mounds) archaeological sites in Santa Catarina state, South Brazil

In this article, GPR – Ground Penetrating Radar and inductive electromagnetic (EM38 equipment) results are presented for three archaeological sites of shell mounds located between Laguna and Jaguaruna cities, mid-southern coast of Santa Catarina state, Brazil. The Jabuticabeira II, Santa Marta IV, and Encantada III sites were studied. These sites consist of carbonate shell mounds built by societies that inhabited this region during the pre-colonial period (7.5–1.3 ky BP). Geophysical responses obtained in these archaeological sites had allowed the identification of anomalous regions related to archaeological point targets as well as continuous targets, correlated to the shell mound's structure and buried geologic features. GPR numerical modelling studies were done in order to evaluate the performance of the GPR method in relation to materials found in that environment, besides helping interpretations of real results. The synthetic GPR model was a good match with real data obtained in the field. So, the real and synthetic results serve as a reference guide to direct excavation activities in these archaeological and geological structures. In the Jabuticabeira II shell mound, lithic materials and burials were found amidst archaeological layers characterized by sediment rich in organic material, ferruginous concretions, and loose shells. In the Santa Marta IV archaeological site, a concentration of ceramic materials, burials and fireplaces were found. In the Encantada III site, a strong anomaly characterized by a hyperbolic reflection was related to the presence of a silicified tree root; a great example of ambiguity in shallow geophysics interpretation in archaeological applications. Results functioned as a guide to archaeological excavations, allowing cost and time reduction as well as contributing to improve the knowledge of these archaeological sites situated in southern Brazil.     

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 use of soil chemistry data to address post-mortem diagenesis in bone mineral

The soluble and exchangeable ions for a soil profile from the Roonka archaeological site. Lower Murray Basin, South Australia, are compared with the total elemental content of the soils. Since the chemical composition of post-mortem ionic substitution phases and secondary minerals in archaeological bone will depend on the availability of ions to the soil solution under field conditions, it is suggested that models addressing diagenesis in bone employ soluble and exchangeable ions rather than total elemental soil data.     

Detection of exposed and subsurface archaeological remains using multi-sensor remote sensing

Multi-sensor airborne remote sensing has been applied to the Itanos area of eastern Crete to assess its potential for locating exposed and known buried archaeological remains, and to delineate subsurface remains beyond the current limits of ground geophysical data in order to permit future targeted geophysical surveys and archaeological excavations. A range of processing techniques (e.g., Reed–Xiaoli anomaly detection) have been applied to the CASI, ATM and lidar data in order to detect anomalies based on the premise that buried remains are likely to alter the physical and chemical characteristics of the soil compared with those of the surroundings due to variations in soil depth and drainage. Through a combination of CASI, ATM and lidar data, surface remains have been classified and mapped effectively using an object-oriented approach. The detection of subsurface remains is more problematic; however, the thermal data is most promising in this respect. The value of capturing multi- or hyperspectral data at a high spatial resolution has been demonstrated as well as the additional benefits of combining these with airborne lidar.     

Calcium–iron–phosphate features in archaeological sediments: characterization through microfocus synchrotron X-ray scattering analyses

The occurrence of amorphous calcium (Ca)–iron (Fe)–phosphate infilling features in thin-section samples from archaeological stratigraphies is increasingly being reported and used in the cultural interpretations of sites. In some contexts, these materials are the product of dissolution and recrystallization of bone material within pores of the soil or sediment matrix. This study uses transmitted microfocus X-ray scattering to characterize and measure features of known cod fish bone (Gadus morhua) materials, and compare them to archaeological samples of amorphous Ca-Fe-phosphate infilling material found in thin section from early fishing community sites. The analyses characterize the structure of these features for the first time, and allow discussion of the diagenetic processes that lead to their formation.     

ACKNOWLEDGING FIFTY YEARS OF NEUTRON ACTIVATION ANALYSIS IN ARCHAEOLOGY

Neutron activation analysis has been an important analytical technique for chemical characterization studies of archaeological materials since 1957, and remains one of the best analytical approaches for bulk chemical characterization of archaeological ceramics and other materials. This paper introduces a series of reports that document the history of NAA applied to archaeological materials.     

Multi-element soil analysis: an assessment of its potential as an aid to archaeological interpretation

Multi-element soil analysis is now an established technique in archaeology. It has been used to locate archaeological sites and define the extent of human activity beyond the structural remains, and to aid interpretation of space use in and around archaeological remains. This study aimed to evaluate the consistency of these soil element signatures between sites and hence their potential usefulness in archaeological studies. Known contexts on abandoned farms across the UK were sampled to test the relationships between element concentrations and known functional area and to assess inter-site variability. The results clearly show that there are significant differences in the soil chemistry of contrasting functional areas, particularly for Ba, Ca, P, Zn, Cu, Sr and Pb. Despite significant site specific effects, which appear to reflect individual anthropogenic practices rather than geological influences, there is sufficient similarity in the pattern of element enhancement to allow reliable interpretation of former function using discriminant models. Relating these enhancements to precise soil inputs, however, is more problematic because many important soil inputs do not contain distinct element fingerprints and because there is mixing of materials within the soil. There is also a suggestion that charcoal and bone play an important role in both the loading and post-depositional retention of Ca, Sr, P, Zn, and Cu and thus may be significant in the formation of soil element concentration patterns.     

Study of interactions between polyethylene glycol and archaeological wood components by C high-resolution solid-state CP-MAS NMR

While use of polyethylene glycols, PEG, polymers for archaeological wood conservation has been well established, there is almost no study of such composite materials with carbon thirteen high-resolution solid-sate NMR. We demonstrate that NMR is an useful analytical tool to characterize rapidly samples of conserved wooden objects. By choosing an appropriate value of the contact time (from 3 to 5 ms) for which the PEG component gives only a small residual NMR signal in the CP-MAS experiment, it is possible to edit selectively the spectra of the wood components. It allows one to visualize the degradation extent of the archaeological wood even when the conservation processes have been already applied. Moreover, by studying the kinetics of CP-MAS experiments, the time constants, T_1ρH and T_CH values for PEG moiety were computed. From these data, it is shown that either in the crude commercial product or in incorporated in archaeological woods, two components are present and they are the signatures of crystalline (or ordered) and amorphous (or disordered) molecular domains. Moreover, it was shown in the archaeological woods that almost 30% of PEG was in close molecular interactions with lignins. This study is the first evidence that the PEG in conserved wood can interact at a molecular level with wood components. It also demonstrates that the PEG diffuses inside the residual cell walls of archaeological wood. This data are important for scientists in charge of process development for the conservation of wooden artifacts.     

Why does (archaeological) micromorphology have such little traction in (geo)archaeology?

Archaeological deposits are often complex and illustrative of an intricate interplay between geogenic and anthropogenic inputs and formation processes. Even for those archaeologists—particularly prehistorians—who consider the basic principles of natural stratigraphy to excavate their sites, they nonetheless typically underutilize the observations and data available at the microstratigraphic level. The technique of soil micromorphology—or archaeological micromorphology as referred to throughout this paper—has seen an astounding increase in its use to answer archaeological questions and archaeological sediments in the last decades. However, we consider that this tool is still quite underutilized and not as mainstream as other techniques. In this paper, we briefly reflect on what can be some of the causes underlying this situation and how we (that is, both producers and consumers of micromorphology data) can go about to change it. The main idea is that we need to establish a better and more approachable way to present micromorphological results and be better at integrating them with the macroscopic archaeological data and research questions.     

Evaluating Natural Site Formation Processes in Eolian Dune Sands: A Case Study from the Krmpotich Folsom Site,Killpecker Dunes,Wyoming

Eolian dune sands commonly contain archaeological material in both surface and buried contexts. However, because of the dynamic nature of dunes, the original context of an archaeological site can be severely modified or destroyed as a result of post-occupational geomorphic processes. This paper examines a Folsom occupation associated with a buried soil in the Killpecker Dunes in southwestern Wyoming. Field and labortory data are compared to determine the likely scenario of natural site formation processes responsible for the current context of the archaeological assemblage. Two primary eolian stratigraphic units are present at the site, and are separated by the buried artefact-bearing soil. Radiocarbon and optical luminescence ages indicate that the Folsom artefacts occur across a temporal hiatus, and that the buried soil is late Holocene in age. Sedimentological data indicate that the highest frequencies of artefacts by depth are associated with an erosional contact characterized by a concentration of coarse-grained material. Thus, the Folsom assemblage appears to have been vertically displaced as a result of post-occupational erosion and deflation. This case study indicates that evaluating the context of an archaeological occupation in a dune setting is best carried out utilizing multiple lines of evidence derived from both field and laboratory work.