THE POTENTIAL OF CARBONIZED GRAIN TO PRESERVE BIOGENIC 87SR/86SR SIGNATURES WITHIN THE BURIAL ENVIRONMENT*

Carbonized grains survive for millennia in many archaeological contexts. Their stable structure raises the possibility that they preserve biogenic strontium isotope signatures. This hypothesis was investigated using short‐term, laboratory experiments with modern grain immersed in Chalk solution. HCl leaching removed > 95% of secondary alteration from charred grain, and isotope ratios close to the starting value were recovered. This could not be achieved with uncharred grains. HCl leaching of archaeological carbonized grains produced comparable levels of decontamination. Although preliminary, these results suggest that strontium isotope analysis of archaeological carbonized grains from calcareous burial contexts could be used to investigate ancient trade and agriculture.     

TESTING AN ALTERNATIVE HIGH‐THROUGHPUT TOOL FOR INVESTIGATING BONE DIAGENESIS: FTIR IN ATTENUATED TOTAL REFLECTION (ATR) MODE*

Archaeological bone undergoes alterations after burial (diagenesis) that constitute a problem for the survival of archaeological information. A common method to assess this alteration is Fourier transform infrared spectrometry (FTIR). However, the commonly applied method (FTIR–KBr) is destructive and sample preparation may influence the results. This paper tests the suitability of FTIR attenuated total reflection (FTIR–ATR), a method not commonly used to investigate bone diagenesis. FTIR–ATR requires less sample preparation and can be non‐destructive, allowing analysis of bone cross‐sections. Modern and archaeological bones were analysed using both methods and different sample preparation methods were tested. The results show that FTIR–ATR has advantages for the rapid assessment of bone diagenesis.     

Patterns of Diagenesis in Bone II: Effects of Acetic Acid Treatment and the Removal of Diagenetic CO3

Archaeological bones of varying preservation have been treated with 0·1 M acetic acid in order to investigate the effect on structural and chemical alterations caused by diagenesis. Acetic acid is commonly used as a “cleaning agent” for removing diagenetic carbonate from bone and enamel, in an attempt to recover original, biogenic signals for use in dietary and¹⁴C dating studies.Diagenetic parameters were measured before and after treatment on a range of archaeological bones with good and bad preservation. Histological preservation defined the behaviour of the correlating parameters, where correlation coefficients between carbonate content and crystallinity, microporosity and macroporosity increased significantly after treatment. For histologically well preserved material, acetic acid is effective at returning carbonate content to around that of modern bone. Where bone is extensively damaged by micro-organisms, “loose” diagenetic material can be removed, but a fraction largely composed of hypermineralized bioapatite remains, which, we believe, cannot be reliably used to obtain accurate biological signals.     

BONE POROSITY AND THE USE OF MERCURY INTRUSION POROSIMETRY IN BONE DIAGENESIS STUDIES*

Porosity measurements made on archaeological bones have revealed very-close relationships between changes in the porosity, remaining protein content and mineral alterations. The results have important implications for models that attempt to quantify the rates and extent of chemical reaction between bone and its geochemical environment. We report here on a novel application of an established technique, mercury intrusion porosimetiy, to investigate in more detail the pore size distribution of archaeological bones. Mercury intrusion porosimetry measures an ‘intermediate’range of bone porosity, ‘mesoporosity’, and produces data which permit the observation of significant structure characteristics in the porosity of modern laboratory altered and diagenetically altered bones.     

Bone Diagenesis and Taphonomic History of the Paso Otero 1 Bone Bed, Pampas of Argentina

Samples of guanaco bone from an archaeological site in the Pampas of Argentina have been analysed to understand the diagenetic profile of the bone assemblages that characterized the taphonomic history of the site. Two archaeological occupations of Paso Otero 1 were investigated, encompassing similar landscape settings, climates, and depositional environments. The time span is a c. 2000 year period from c. 4800 to 2800 years . A total of 30 bone samples taken from both occupations were used to provide a preliminary characterization of the diagenetic pathways at the site. The parameters investigated provide a comprehensive account of how both mineral (hydroxyapatite) and bone protein (collagen) have been altered. In order to compare the two bone assemblages in terms of their diagenetic parameters, multivariate analyses were conducted. Results indicate two different diagenetic profiles in the site, % N being one of the variables that accounts for most of the variation in Paso Otero 1. The diagenetic analyses indicate that protein is less preserved in the bone assemblage from the middle stable landscape. Alternative interpretations of the diagenetic profiles are discussed in light of the taphonomic history of the site, and palaeoenvironmental information of the region. One hypothesis stresses the importance of the role of climate in defining the different diagenetic pathways, and the other the continued action of the combined diagenetic factors along time as the main explanation for the variability in the state of preservation of the bones in Paso Otero 1.     

EFFECTS OF DIFFERENT SAMPLE PREPARATION METHODS ON STABLE CARBON AND OXYGEN ISOTOPE VALUES OF BONE APATITE: A COMPARISON OF TWO TREATMENT PROTOCOLS*

Researchers have long debated the appropriateness of stable isotope analysis of bone apatite to reconstruct the diets of ancient animals. The debate has centred, in part, on diagenesis of bone mineral from interaction with the burial environment. A number of acetic acid treatments are used to remove diagenetic carbonates from samples; however, less is known on how different protocols alter stable isotope values. We compare two common acetic acid solution treatments (0.1 M versus 1.0 M-buffered) to examine the effects on carbon and oxygen isotope values and Fourier transform infrared spectroscopy (FTIR) spectra in human bone from different burial contexts. Results indicate that both treatments have a similar effect on isotope values and FTIR spectra in bone apatite.     

AUTOMATION OF SOLUBILITY PROFILES USING A FLOW CELL

The solubility profile technique is a means of characterizing the mineral phase of bones and fossils from archaeological and palaeontological sites. The method is based on the differential dissolution of variously substituted apatites in acetate buffer at pH 4.5. The original solubility profile protocol, which involves repetitive washing and centrifuging, is extremely cumbersome and time-consuming. Here we describe an alternative, automatic method in which the fossil bone preparations are dissolved in a perspex cell. The behaviour of fossil preparations in the manual and automatic protocols are compared. We conclude that the dissolution cell is satisfactory for routine applications, but that the original, manual protocol is preferable for preliminary investigation of untested assemblages.     

MULTIANALYTICAL STUDY OF PALAEOLITHIC REINDEER ANTLER. DISCOVERY OF ANTLER TRACES IN LASCAUX PIGMENTS BY TEM*

Palaeolithic and modern reindeer antler were analysed using complementary techniques to evaluate the conservation state of bone material. X‐ray diffraction, FT‐IR spectroscopy, scanning electron microscopy (SEM–EDX) and transmission electron microscopy (TEM–EDX) as well as proton induced X‐ray and γ‐ray emission (PIXE–PIGE) at the particle accelerator AGLAE, C2RMF were applied. This study enabled us to define the chemical and structural features of ancient antler at the micro‐ and nanometre scale and compare them to those of other bone materials such as bone and ivory. Antler is richer in its organic fraction compared to bone and ivory. Its mineral fraction, carbonated hydroxylapatite, shows very specific crystal shapes at the nanometre scale. This specific property allowed us to recognize antler traces in pigment samples originating from rock art paintings in the Lascaux cave, Dordogne, southwestern France, Magdalenian period. Therefore, TEM–EDX is the technique of choice for characterizing antler traces in complex mixtures. In the paint material of Lascaux, antler seems most likely to be a pollutant introduced either by stirring the pigments in water with a piece of antler or by carving antler artefacts next to the preparation of paint material. However, it could eventually be used as a marker of paintings that were created contemporaneously.     

COMMENT: CHEMICAL AND MINERALOGICAL APPROACHES TO CERAMIC PROVENANCE DETERMINATION

This comment concerns an ‘absolutist’ perspective on the superiority of mineralogical analysis over chemical analysis for the determination of ceramic provenance. This point of view has appeared in the literature in recent years, but it has not been justified and is not justifiable. Mineralogy and chemistry are complementary. They measure different things and are best used in combination to generate secure, geographically specific ceramic source assignments.