Preservation potential of charcoal in alkaline environments: an experimental approach and implications for the archaeological record

Charcoalified plant material (usually wood) has been described as being inert with a high preservation potential. Although usually black on both the outside and inside, the physical and chemical properties differ as a function of temperature and time of exposure to a heat source. Post-depositional processes however may exert additional affects on charcoalified material and introduce bias into the archaeological record. This work explores the influence of alkaline conditions, often encountered in the soil environment, on the preservation potential of charcoalified material. Charcoal, experimentally produced at different temperatures, was exposed to a number of solutions of potassium hydroxide and calcium hydroxide with different pHs, to simulate exposure to alkaline soil conditions. Under these conditions chemically mediated physical interactions occur resulting in fragmentation of the charcoal samples into (very) small pieces the size of which depends upon the initial temperature of charcoalification. Moreover further interactions result in a decrease in reflectance relative to samples not exposed to alkaline conditions. Although experimentally driven the potential for physical loss of charcoal from a particular site coupled with the reduction in (expected) reflectance of any resident material, has important implications for any conclusions drawn regarding the archaeological record.     

Stable carbon and oxygen isotopic compositions of wood ash: an experimental study with archaeological implications

Wood ash, composed mainly of the mineral calcite, is an important component in many archaeological sites. Identification of wood ash in the archaeological record is often difficult due to mixing of ash with other calcitic components of geogenic origin and/or due to diagenetic changes. A recent empirical study using the stable isotope compositions of carbon (δ¹³C) and oxygen (δ¹⁸O) in wood ash enabled the identification of mixtures of wood ash with geogenic calcite and to follow diagenetic changes due to partial dissolution and re-precipitation of ash in two prehistoric cave sites in Israel. Little however is known about the processes responsible for the isotopic compositions of wood ash in relation to formation at various temperatures and the influence on isotopic composition of ash from a variety of plant species. Here we present an experimental study of wood ash formed by burning three C3 tree species and one C4 desert bush at different temperatures. The results indicate that there are significant differences in the isotopic compositions of carbon and oxygen between wood ash that forms by combustion at a relatively low temperature (500 °C) and at a higher temperature (900 °C). In addition, we show that the isotopic composition of carbon and oxygen in high temperature wood ash approaches equilibrium over a period of several months and that the carbon isotopic composition of low temperature wood ash may reflect the photosynthetic pathway of the burnt woody species. Lastly, we show that the isotopic compositions obtained from wood ash prepared at different temperatures do not reflect a temperature dependent fractionation process, but a mixing line between calcite that formed by low temperature combustion and calcite formed by high temperature combustion which later underwent re-carbonation with atmospheric CO₂. In addition, we suggest that exchange processes may possibly occur during combustion between decomposing calcium-oxalate and atmospheric O₂, CO₂ and CO. The archaeological implications of this study are discussed in relation to identification of wood ash in the archaeological record, identification of fuel sources and burning temperatures, and diagenetic changes expected in karstic cave environments. The method presented here can be applied at any archaeological site.     

Compression and digestion as agents of vertebral deformation in Sciaenidae,Merlucidae and Gadidae remains: an experimental study to interpret archaeological assemblages

Journal of Archaeological Method and Theory - Fish taphonomy from archaeological sites provides considerable useful information about human behaviours and environmental contexts as potential food...     

Hunting lesions caused by osseous projectile points: experimental results and archaeological implications

The identification of projectile impact traces on archaeological faunal remains is an important issue for understanding prehistoric hunting behavior, especially in the Paleolithic and Mesolithic. From the beginning of the Upper Paleolithic in Europe, and earlier in Africa, projectiles tipped with osseous points were of great importance for subsistence; but thus far, no specific experimental reference has been developed to help identify the traces left by these points. In 2003 and 2004 two series of projectile experiments with antler points of Magdalenian design were organized, involving two ox calves and two female fallow deer as targets for bow and spearthrower shooting. The subsequent study demonstrates that positive identifications of impact traces left by osseous points can be made. The observation of 127 impact traces allowed us to distinguish three main types of traces: notches, punctures and perforations. The relationships between the nature of the impact traces and the (i) target species, (ii) characteristics of the impacted bones, and (iii) type of weapon are presented. Synthesized results are then discussed within the context of the European Upper Paleolithic and Mesolithic.     

Terrestrial hermit crabs (Anomura: Coenobitidae) as taphonomic agents in circum-tropical coastal sites

Hermit crabs are ever alert for more suitable shells to inhabit, but what this may mean for coastal shell middens has rarely been considered. Here, the impact of the most landward-based of hermit crab families, the tropical Coenobitidae, upon archaeological shell-bearing deposits is assessed using a case study: the Neolithic Ugaga site from Fiji. At Ugaga, hermit crabs were found to have removed the majority of shells from the midden and had deposited their old, worn shells in return. The behavioural ecology of genus Coenobita suggests a mutualistic interaction whereby humans make available shell and food resources to hermit crabs, which in turn provide a site cleaning service by consuming human and domestic waste. Diagnostic indicators of terrestrial hermit crab wear patterns on gastropod shells are outlined and the conditions under which extensive ‘hermitting’ of shell midden deposits may occur are investigated. The ability to recognise hermit crab modification of shells is considered not only important for archaeomalacologists analysing tropical shell deposits, but also for field archaeologists wishing to select suitable shell samples for radiocarbon dating.     

Fuel, Fire and Heat: an experimental approach to highlight the potential of studying ash and char remains from archaeological contexts

As in traditional societies today ancient societies probably selected different fuels to meet specific heat requirements. Char and ash, the end products of fire, are often found in abundance in archaeological contexts. These end products can provide information regarding (i) the original fuel resource and type, (ii) the characteristics of the fire and (iii) combined with other archaeological evidence shed further light on possible socio-economic activity(-ies) associated with that fire. The three main fuel resources would have been (i) modern vegetation, (ii) fossil fuel and (iii) animal by-products. Local availability and abundance would have influenced the choice made.In this study an experimental approach was adopted to try and distinguish between the three different fuel resources that are known to have been used by ancient societies (and continue to be used by traditional societies today) from their char and ash remains to help determine original fuel-type and understand the relative heating properties. For this end one fuel-type from each fuel resource listed above, namely wood, peat and cow dung, was chosen.     

Temperature,compression and fragmentation: an experimental analysis to assess the impact of taphonomic processes on charcoal preservation

This paper explores how mechanical properties of different South Asian tree taxa might influence charred wood fragmentation and the composition of charcoal assemblages retrieved from archaeological contexts. The dataset is composed of selected plant species that were collected in Gujarat (Northern India) in September 2007 as part of the North Gujarat Archaeological Project. The taxa analysed represent the most common wood species found in the arid thorn scrubland formation in South Asia and are among the most abundant identified in Neolithic and Chalcolithic archaeological sites in this area. The specimens have been measured and subsequently charred at three different temperatures, under constant conditions. Afterwards, their resistance to compression has been measured on two planes, parallel and perpendicular to the direction of fibres, using a Hounsfield 5-kN machine. The tests were performed in order to understand the different response to compressive stress of wood that has been subject to a range of thermal degradations. The standardised treatment applied to the samples has permitted the comparison of results and the delineation of simple correlations and divergences among the species analysed. Furthermore, the utilisation of a relatively simple operating protocol easily allows the addition of further data in the future. The applied protocol was specifically designed to answer archaeological questions. Therefore, even though from a material science point of view some of the measurements were not taken according to the prevailing standard procedures, it offers valuable data for anthracological research applied to archaeology in arid zones.     

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.     

Young lesbians negotiating public space: an intersectional approach through places

In this paper I analyze how different aspects of identity combine to shape the experiences of seven young lesbians in public space in Manresa, a non-metropolitan city in Catalonia. I argue that their experiences need to be understood intersectionally and spatially, as complex processes that involve the mutually constituted identities that shift in space. I focus on interviews and Relief Maps to show how these dynamics work and how they are related to larger social processes such as the heteronormalization and adultification of public space.     

Rock art as an archaeological and social indicator: The neolithisation of the Iberian Peninsula

Rock art has been regarded as a second class archaeological data source. In this paper we use Levantine rock art as a case study, to show how this situation can be reversed. This rock art, found along the Mediterranean region of the Iberian Peninsula, has been considered to be typically Mesolithic due to its distinctive hunting scenes. A review of certain archaeological indicators provides new arguments about its chronology, its socio-cultural attribution, and its significance. We first deal with the chronological issue, presenting the evidence that led to the recent consideration of the Levantine style as Early Neolithic, in synchrony with two other rock art styles (Schematic and Macroschematic). We will further propose that rock art itself is a central and independent source of information to explore the historical context of the Neolithisation of Mediterranean Iberia. Its wide geographical distribution allows us to study different and complementary territories as a single entity. This contrasts with the limitations posed by the study of settlements, whose differences, at a regional scale, are usually interpreted in terms of cultural variability. If we consider rock art as a key aspect in the constitution of social landscapes, it must not be treated just as an ideological by-product of the Neolithisation, but as a key factor in understanding this historical process.     

Temporal frequency distributions of alluvium in the American Southwest: taphonomic,paleohydraulic, and demographic implications

The use of radiocarbon frequency distributions to reconstruct prehistoric human and animal populations must account for taphonomic loss and other factors that affect the archaeological and paleontological records. Surovell et al. (JAS, 36, 1715–1724) have recently proposed a correction for “taphonomic bias” that is based on the radiocarbon frequency of a global sample of volcanic deposits. Analysis of 717 radiocarbon dates sampled from the alluvium of the San Pedro and Santa Cruz rivers and their tributaries in southeastern Arizona shows that discovery and scientific biases also play an important role in the creation of radiocarbon frequency distributions, and that the rate of “taphonomic bias” in prehistory is not predicted by the radiocarbon frequency of volcanic deposits. The latter principle is further argued using a sample of 123 Pliocene to Clovis-age proboscideans from the San Pedro Valley. We propose an alternative model that is based on the nature of the stratigraphic record, with discovery bias, scientific bias, taphonomic loss, and the shape of the calibration curve all operating to influence the temporal frequency distribution of radiocarbon-dated prehistoric phenomena.     

Hunting with Howiesons Poort segments: pilot experimental study and the functional interpretation of archaeological tools

For many decades the use of backed pieces from the Howiesons Poort, between about 70 ka and 55 ka ago, in South Africa has been a point of discussion. Recently direct evidence has been provided to associate these tools with Middle Stone Age hunting strategies. Yet, whether they were used to tip hunting weapons or as barbs remained an open question. In this paper we introduce a set of pilot experiments designed to test the effectiveness of Howiesons Poort segments, the type fossils of the industry, hafted in four different configurations as tips for hunting weapons. It is shown that the morphological type can be used successfully in this way. We present the results of a macrofracture analysis conducted on the experimental tools and compare these to results obtained from three Howiesons Poort backed tool samples. By correlating experimental outcomes, macrofracture data and the interpretation of micro-residue distribution patterns, we provide some insight into the functional variables that might be associated with Howiesons Poort segments.     

The decomposition of starch grains in soils: implications for archaeological residue analyses

Recent research involving starch grains recovered from archaeological contexts has highlighted the need for a review of the mechanisms and consequences of starch degradation specifically relevant to archaeology. This paper presents a review of the plant physiological and soil biochemical literature pertinent to the archaeological investigation of starch grains found as residues on artefacts and in archaeological sediments. Preservative and destructive factors affecting starch survival, including enzymes, clays, metals and soil properties, as well as differential degradation of starches of varying sizes and amylose content, were considered. The synthesis and character of chloroplast-formed ‘transitory’ starch grains, and the differentiation of these from ‘storage’ starches formed in tubers and seeds were also addressed. Findings of the review include the higher susceptibility of small starch grains to biotic degradation, and that protective mechanisms are provided to starch by both soil aggregates and artefact surfaces. These findings suggest that current reasoning which equates higher numbers of starch grains on an artefact than in associated sediments with the use of the artefact for processing starchy plants needs to be reconsidered. It is argued that an increased understanding of starch decomposition processes is necessary to accurately reconstruct both archaeological activities involving starchy plants and environmental change investigated through starch analysis.     

Black grouse as the prey of the golden eagle at an archaeological site

Remains of black grouse, Lyrurus tetrix, were recovered from an archaeological excavation of the site of a golden eagle, Aquila chrysaetos, eyrie. It has been suggested that bird remains from human predation can be distinguished from those due to avian predation, because humans leave few of the distal bones (tibiotarsus, carpometacarpus). In this case, the eagle also left few of these bones; it is suggested that the distinction is one which may allow owl prey to be distinguished, but human and raptor prey are indistinguishable by that criterion.     

The value of sieving of grave soil in the recovery of human remains: an experimental study of poorly preserved archaeological inhumations

The aim of this work is to assess the effects of sieving basal grave fills, following lifting of visible skeletal remains on the recovery of human bones and loose teeth in poorly preserved inhumation burials. The experiment was carried out during excavations at the 7th–9th century AD cemetery site at Whitby, England. Burials generally consisted of degraded bone fragments and/or soil stains. In each grave (N = 70 adult burials), all visible human remains were hand-collected on site; following this, the soil remaining in the grave was recovered and sieved successively through 8 mm, 4 mm and 2 mm meshes. No bone or dental fragments in the 2–4 mm fraction were identifiable to skeletal element. Approximately one third of the total weight of bone, and one third of the total numbers of teeth were recovered in the 4–8 mm and >8 mm sieved fractions. It is concluded that sieving down to 4 mm is adequate for recovery of adult skeletal remains at the study site. It would be useful to conduct similar sieving experiments at other archaeological cemetery sites to provide data on recovery when bone survival is good, and in subadult burials.     

Characterization of archaeological lime mortars in a Ming dynasty tomb: A multi-analytical approach

Lime mortars have played an important role in constructing ancient Chinese masonry structures, including city walls, buildings, and tombs. A tomb built with lime mortars and stones belonging a Ming high-ranking official, Xu Jie, was discovered in Huzhou City of China. Eight different samples from Xu Jie’s tomb, representing four types of lime-mortar-based materials: joint mortar between stone bricks, bedding mortar, grouting mortar, and plaster mortars were collected for analysis and comparison. The characterization of the construction materials has therefore become of primary importance. The function of each mortar was reported and studies into the micro-textural features and mineralogical compositions of those mortars were performed via a multi-analytical approach. The joint mortars were all found to be aerial lime mortars with predominately lime. The bedding mortar was found to consist of lime, soil and sand, typical of a tabia mortar. The grouting mortar was found to consist of lime and ground contact metamorphosed limestone. Analysis of plaster sample taken from the roof of the main tomb identified the presence of calcium stearate/palmitate, indicating the usage of plant-based tung oil as an additive. The analytical results will promote our understanding of Ming architectural technology and craftsmanship, and provide critical information for the conservation of Xu Jie’s tomb.     

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.     

Relative frequency of butchering cutmarks produced by obsidian and flint: an experimental approach

An experimental approach was used to determine how stone tool materials affect the frequency of observed cutmarks. Five whitetail deer were butchered by an expert butcher using flint and obsidian tools and the skeletons were prepared and analyzed. The authors found that the deer butchered with obsidian tools generally displayed fewer incidents of cutmarks than their flint-butchered counterparts. Consideration of this variable may prove to be important to archaeologists attempting to answer questions of specialization or when making comparisons of cutmark data between sites.