Bones and teeth are highly hierarchically structured and hererogeneous materials, and post mortem processes can reinforce this heterogeneity. It is therefore important to consider this heterogeneity ...to better understand diagenetic processes. In this study, ATR-FTIR mapping was applied to several heated and un-heated archaeological samples, and to similar modern references in order to test the potential of this method. ATR-FTIR mapping can provide spatially resolved information on alteration state of mineral and organic matter. This technique allowed to describe the spatial distribution of organic and mineral matter preservation in unheated Palaeolithic bones (Bize-Tournal, France) characterized by a better preservation in the centre of the cortical bone. Spatial variations in the chemical composition of an archaeological heated bone (Abri Pataud, France) compared to a modern reference suggested taphonomical uptake of carbonate in the most external part. This pattern could correspond to a process of re-carbonatation of the calcined mineral matter in the outermost part of the sample due to combustion in a CO2 rich atmosphere. FTIR-ATR is a powerful tool that allows for identifying and characterizing local heterogeneities in bone preservation. This technique open new prospects to reconstruct the taphonomical history of ancient samples.
•ATR-FTIR mapping was applied to several modern and archaeological samples.•ATR-FTIR can provide spatially resolved information on mineral and organic matter.•The preparation protocol will allow multi-scale and multi-technique approaches.•This technique has the potential to identify the better preserved areas in fossils.•Mapping can provide new insights to reconstruct taphonomical history of samples.
Expensive and time-consuming preparation procedures for radiocarbon and stable isotope analyses can be conducted on archaeological bone samples even if no collagen is preserved. Such unsuccessful ...preparation can lead to the partial destruction of valuable archaeological material. Establishing a rapid prescreening method for evaluating the amount of bone collagen while minimizing the impact of sampling constitutes a challenge for the preservation of archaeological collections. This study proposes and discusses a new methodology to detect and quantify collagen content in archaeological bone samples by attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy. A total of 42 Pleistocene to modern bone samples were selected according to their nitrogen content measured using an elemental analyzer. Comparison of collagen content estimation using ATR-FTIR and mass spectrometry reveals that some of the studied samples are contaminated by a nitrogen source coming from the burial environment. Two different FTIR calibration approaches were tested on the uncontaminated samples: peak-to-peak ratio and multivariate regression (PLS). The two approaches yield similar results with a good correlation of ATR-FTIR analyses and N wt% from 0.7 to 4wt% (R²=0.97–0.99; standard error of estimation ±0.22 to 0.25wt%). While collagen content remains difficult to detect in poorly preserved bones (less than ~3wt%), ATR-FTIR analysis can be a fast alternative for sample screening to optimize the sampling strategy and avoid partial destruction of valuable samples that do not contain enough collagen for further analysis.
Strontium isotopic analysis of sequentially formed tissues, such as tooth enamel, is commonly used to study provenance and mobility of humans and animals. However, the potential of
Sr/
Sr in tooth ...enamel to track high-frequency movements has not yet been established, in part due to the lack of data on modern animals of known movement and predictive model of isotope variation across the landscape. To tackle this issue, we measured the
Sr/
Sr in plant samples taken from a 2000 km
area in the Altai Mountains (Mongolia), and the
Sr/
Sr in tooth enamel of domestic caprines whose mobility was monitored using GPS tracking. We show that high-resolution, sequential profiles of strontium isotope composition of tooth enamel reliably reflect the high-frequency mobility of domestic livestock and that short-term residency of about 45 days can be resolved. This offers new perspectives in various disciplines, including forensics, ecology, palaeoanthropology, and bioarchaeology.
Exogenous carbonaceous contaminants coming from sediments significantly bias the radiocarbon date of collagen samples extracted from archaeological bone and teeth. In this study, a new approach ...combining pyrolysis, comprehensive gas chromatography and mass spectrometry (Py-GC × GC/MS) was proposed to ensure their removal during the demineralization and bone collagen extraction. This approach permitted to identify hydrocarbon contaminants for archaeological samples from the Neolithic period, in 30–40 μg of collagen. The use of 2D GC improved importantly the separation, selectivity and resolution compared to 1D GC thus permitting to detect organic contaminants within the complex chromatograms issued from collagen pyrolysis. Moreover, efficiency of the extraction steps in collagen sample preparation for radiocarbon dating (acid and alkali treatments, filtration steps) could be evaluated for four different protocols on the basis of organic contaminant removal. Radiocarbon dating of the extracted collagen of four of the tested protocols corroborated the results of the Py GC × GC/MS data. This approach opens new perspectives for the use of comprehensive gas chromatography in the domain of archaeological sciences.
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•Soil contaminants in archaeological collagen may be detected upstream.•Collagen extraction protocols are differently effective for removing contaminants.•Py-GCxGC/MS is efficient to assess contaminant persistence and collagen preservation.
Collagen glue has been used for nearly two centuries to consolidate bone material, although its prevalence in museum collections is only now becoming visible. Identifying and removing collagen glue ...is crucial before the execution of any geochemical or molecular analyses. Palaeolithic bone objects from old excavations intended for radiocarbon dating were first analysed using ZooMS (Zooarchaeology by Mass Spectrometry) to identify the animal species, however peaks characteristic of both cattle and whale were discovered. Two extraction methods for ZooMS were tested to identify the authentic animal species of these objects, which revealed that these were originally whale bone objects that had been consolidated with cattle collagen glue. This is the first time animal collagen glue has been identified in archaeological remains with ZooMS, illustrating again the incredible versatility of this technique. Another technique, Fourier Transform Infrared Spectroscopy in Attenuated Total Reflectance mode (FTIR-ATR), was also tested if it could rapidly identify the presence of collagen glue in archaeological bone material, which was not the case. Two other cleaning methods were tested to remove bone glue contamination prior to radiocarbon dating, along with two modified collagen extraction methods for ZooMS. These methods were applied to bone blank samples (FmC = 0.0031 ± 0.0002, (n = 219), 47 336 ± 277 yr BP) that were experimentally consolidated with collagen glue and to the Palaeolithic bone material (ca. 15 000 and 12 000 yr BP). The experimental bone blanks produced excellent
C ages, suggesting the cleaning methods were successful, however the
C ages for some of the Palaeolithic material remained too young considering their contextual age, suggesting that the collagen glue contamination had most likely cross-linked to the authentic collagen molecule. More research is needed in order to gain a deeper understanding of the occurrence and elimination of cross-linked collagen-based glues in material from museum collections.
Since the early trials in the 50
's, the reliability of
14C dates obtained from bioapatites has always been questioned. However, methodological attempts at dating biological apatites are rare. The ...compilation of the radiocarbon dates published in
Radiocarbon over the period 1959–2009 shows that less than 6% of all the bone dates were performed on purified bioapatite. Crucial for the validation of the approach, is the design of tests for the preservation of the geochemical signal in biological apatites that are relevant for
14C dating. Because carbonate in apatite can exchange isotopically with dissolved carbon present in the environmental fluids, pretreatments are necessary but not sufficient and preservation criteria based on mineral integrity are of limited help. In this case, only an indirect approach, based on the dating of different bone/tooth fractions of the same individual and/or associated material is able to distinguish between preserved and altered fossils. In case of alteration, it is unlikely that the rate of isotopic exchange/recrystallization will be identical in skeletal tissues with different physico-chemical properties and any intra-individual difference measured in
14C age must result from differential diagenesis. We applied this strategy to more than 100 Holocene and Late Pleistocene localities worldwide. This approach confirms that carbonate in calcined bone is very resistant to post-burial isotopic exchange and is the most reliable source of inorganic carbon for
14C dating regardless of the environmental conditions. Large intra-individual differences in
14C age are found in several European and American localities, showing that both bone and enamel apatite can suffer from rejuvenation due to isotopic exchange during fossilization. On the contrary, the absence of significant intra-individual differences in
14C age in most of the localities from arid environments (Africa, Arabic Peninsula) attests to the good preservation of bone apatite in these regions. This contrasting situation confirms that bone diagenesis must be treated on a site-by-site basis, and demonstrates that bioapatite is a reliable material to date skeletal remains in arid environments.
Bone remains of small vertebrate fossils provide valuable information for paleoenvironmental and paleoclimatic reconstructions. However, direct radiocarbon dating of small vertebrates remains ...challenging as the extraction of sufficient good quality collagen is required. The efficiency of eight collagen extraction protocols was tested on seven samples, representative of different ages and burial environments, including both macro and small vertebrate taxa. First, the samples were prescreened using attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) to quantify collagen content in archaeological bones, revealing that one should be discarded for 14C dating. Then, the quantity of protein extracted (yield) and collagen integrity were checked using conventional elemental analysis. The results show that one protocol was not able to accurately extract collagen from the samples. A soft HCl-based protocol seems more appropriate for the pretreatment of archaeological small mammal bones, whereas a harsher protocol might be more efficient to extract a higher amount of collagen from large mammals as well as amphibian bones. The influence of the tested protocols on carbon and nitrogen isotope values was also investigated. The results showed that isotopic variability, when existing, is related to the interindividual differences rather than the different protocols.
Quantitative reconstruction of paleodiet by means of sequential sampling and carbon isotope analysis in hypsodont tooth enamel requires a precise knowledge of the isotopic enrichment between dietary ...carbon and carbon from enamel apatite (
ε
D–E), as well as of the timing and duration of the enamel mineralization process (amelogenesis). To better constrain these parameters, we performed a series of controlled feeding experiments on sheep ranging in age from 6 to 24
months-old. Twenty-eight lambs and 14 ewes were fed isotopically distinct diets for different periods of time, and then slaughtered, allowing the timing and rate of molar growth to be determined. High resolution sampling and stable carbon isotope analysis of breath CO
2 performed on six individuals following a diet-switch showed that 70–90% of dietary carbon had turned over in less than 24
h. Sequential sampling and carbon isotopic analysis was performed on the first (M
1) and second (M
2) lower molars of four lambs as well as on the third lower molar (M
3) of 11 ewes. The changes in diet were recorded in all molars. We found that the length of enamel matrix apposition is approximately one-quarter of the final tooth length during crown extension, and that enamel maturation spans slightly less than 3
months in M
1, and 4
months in M
2 and M
3. Portions of enamel in equilibrium with dietary carbon were used to calculate
ε
D–E values. Animals on grass silage diets had values similar to previous observations, whereas animal switched to pelleted corn diets had values ca. 4‰ lower, a pattern consistent with lower methane production observed for animals fed concentrate diets. The tooth enamel forward model of
Passey and Cerling (2002) closely predicted the amplitude of isotope changes recorded in tooth enamel, but slightly underestimated the rate of isotope change, suggesting that the rate of accumulation of carbonate during maturation may not be constant over time. Although stable isotope profiles in tooth enamel represent underdetermined systems, our results demonstrate that they can provide useful information about dietary variability if the mineralization process is taken into account.
Because hard tissues can be radiocarbon dated, they are key to establishing the archaeological chronologies, palaeoenvironmental reconstructions and historical-biogeographical processes of the last ...50,000 years. The advent of accelerator mass spectrometers (AMS) has revolutionized the field of archaeology but routine AMS dating still requires 60-200 mg of bone, which far exceeds that of small vertebrates or remains which hold a patrimonial value (e.g. hominid remains or worked bone artefacts). Here, we present the first radiocarbon dates obtained from minute amounts of bone (3-60 mg) using a MIni CArbon DAting System (MICADAS). An optimized protocol allowed us to extract enough material to produce between 0.2 and 1.0 mg of carbon for graphite targets. Our approach was tested on known-age samples dating back to 40,000 BP, and served as proof of concept. The method was then applied to two archaeological sites where reliable dates were obtained from the single bones of small mammals. These results open the way for the routine dating of small or key bone samples.
A range of archaeological and palaeoclimatic studies use isotopic analyses of ungulate hypsodont tooth enamel. Such studies commonly assume a constant growth rate, though this has not been fully ...tested. Here, we use stable isotope analyses of sequential enamel samples to study horse tooth growth. We fit the data using models corresponding to constant and exponentially decreasing rates of growth, and compare the results to metrical data showing the geometry and timing of apposition. The results indicate enamel apposition and maturation advances at an exponentially decreasing rate. An understanding of this variable growth rate is crucial for interpreting isotopic data from equid teeth.
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