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The study of stable isotopes in fossil bioapatite has yielded useful results and has shown that bioapatites are able to faithfully record paleo-environmental and paleo-climatic parameters from archeological to geological timescales. In an effort to establish new proxies for the study of bioapatites, intra-tooth records of enamel carbonate stable isotope ratios from a modern horse are compared with trace element profiles measured using laboratory micro X-Ray Fluorescence scanning. Using known patterns of tooth eruption and the relationship between stable oxygen isotopes and local temperature seasonality, an age model is constructed that links records from six cheek upper right teeth from the second premolar to the third molar. When plotted on this age model, the trace element ratios from horse tooth enamel show a seasonal pattern with a small shift in phase compared to stable oxygen isotope ratios. While stable oxygen and carbon isotopes in tooth enamel are forced respectively by the state of the hydrological cycle and the animal's diet, we argue that the seasonal signal in trace elements reflects seasonal changes in dust intake and diet of the animal. The latter explanation is in agreement with seasonal changes observed in carbon isotopes of the same teeth. This external forcing of trace element composition in mammal tooth enamel implies that trace element ratios may be used as proxies for seasonal changes in paleo-environment and paleo-diet., Competing Interests: The authors have declared that no competing interests exist.

Upon passage through Earth's atmosphere, micrometeorites undergo variable degrees of melting and evaporation. Among the various textural and chemical groups recognized among cosmic spherules, that is, melted micrometeorites, a subset of particles may indicate anomalously high degrees of vaporization based on their chemical and isotopic properties. Here, a selection of such refractory element‐enriched cosmic spherules from Widerøefjellet (Sør Rondane Mountains, East Antarctica) is characterized for their petrographic features, major and trace element concentrations (N = 35), and oxygen isotopic compositions (N = 23). Following chemical classification, the highly vaporized particles can be assigned to either the "CAT‐like" or the "High Ca‐Al" cosmic spherule groups. However, through the combination of major and trace element concentrations and oxygen isotopic data, a larger diversity of processes and precursor materials are identified that lead to the final compositions of refractory element‐enriched particles. These include fragmentation, disproportional sampling of specific mineral constituents, differential melting, metal bead extraction, redox shifts, and evaporation. Based on specific element concentrations (e.g., Sc, Zr, Eu, Tm) and ratios (e.g., Fe/Mg, CaO + Al2O3/Sc + Y + Zr + Hf), and variations of O isotope compositions, "CAT‐like" and "High Ca‐Al" cosmic spherules likely represent a continuum between mineral endmembers from both primitive and differentiated parent bodies that experienced variable degrees of evaporation. [ABSTRACT FROM AUTHOR]

The impacts of diagenesis on archaeological and palaeontological bone complicate investigations of in-vivo chemical and isotopic characteristics. Such bone is often pre-treated in an attempt to remove diagenetic alteration prior to trace element or isotopic analyses, although very few standardized approaches exist for evaluating pre-treatment effectiveness. In this pilot study, we characterize the diagenetic alteration and assess the impact of acetic acid chemical pre-treatment on the trace element and structural characteristics of four bones from Belgium, including an Early Medieval cremated bone from Broechem and three representative 'old' bones of different ages (ca. 40–130 ka) from the Late Pleistocene sedimentary sequence of Scladina Cave. Each bone was analyzed before and after acetic acid pre-treatment using the 'Perio-spot' technique and 'Perios-endos' profiles. We measured trace element concentrations with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and micro X-ray fluorescence spectroscopy (μXRF). Structural characteristics were investigated with Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). Our results indicate that chemical pre-treatment had little to no significant impact on the trace element content of the Early Medieval cremated bone, had the most impact on the youngest bone from Scladina Cave, and had less impact on the trace element content of two older bones from Scladina Cave. This suggests that the effectiveness of acetic acid chemical pre-treatment is greater for bones undergoing early diagenetic processes, has minimal impact on highly crystalline cremated bone, and may preferentially leach in-vivo signatures from bones undergoing later diagenesis. The weights of leachates removed from each bone also correspond well with their hypothetical diagenetic states, indicating that researchers could potentially assess the diagenetic state of bones by weighing the leachates produced during acetic acid pre-treatment. Therefore, our new approach may provide a valuable step toward effectively and consistently differentiating among in- and ex-vivo trace element signatures, and, by proxy, those of their isotopes, in archaeological and palaeontological bone. • Diagenesis and impact of acetic acid pre-treatment investigated in 'old' and cremated bone • Acetic acid pre-treatment has little to no impact on trace element and structural characteristics of cremated bone • Impact of acetic acid pre-treatment is greatest for reactive 'old' bones undergoing early diagenetic processes • Acetic acid pretreatment may preferentially leach in-vivo signatures from recrystallized 'old' bone • Weights of dried-down leachates correspond with diagenetic state of 'old' bones [ABSTRACT FROM AUTHOR]

High resolution in situ trace element μXRF maps and profiles were measured on the enamel exposed in cross sections through archaeological human permanent molars from seven Late Neolithic/Early Chalcolithic funerary caves and megalithic graves of north-central Iberia. Changes in concentrations of Fe, Zn and Sr in inward direction into the enamel shed light on diagenetic and endogenous trace element concentrations in archaeological tooth enamel. Most of these profiles resemble sigmoid-shaped leaching profiles, suggesting that a combination of diffusion and advection processes govern the uptake of trace elements into the enamel from pore fluids on the outside of the tooth and in the more porous dentine. The present study shows how diffusion-advection (DA) models can be fitted to these trace element profiles to explain changes in trace element concentrations that happen during diagenesis. DA models explain a major part of the variation observed in leaching profiles into the enamel and can be used to reconstruct endogenous trace element concentrations, leaching times and leaching depth as well as trace element concentrations in ambient pore water during diagenesis. Models of trace element leaching together with trace element mapping reveal that Fe, Zn and Sr concentrations consistently increase during diagenesis, regardless of the type of burial site (i.e. funerary caves vs. megalithic graves). Profiles of Pb concentrations show much smaller concentration gradients, causing DA model fitting to be less accurate. Modelled leaching depths of 300–400 μm warrant a careful approach when sampling for endogenous archaeological tooth enamel for trace element and stable isotope analysis. Results also show that it is possible to reconstruct endogenous trace element concentrations from these samples, even without applying pretreatment procedures, because leaching of trace elements into the enamel often remains limited to the outer 300–400 μm of the enamel on archaeological timescales. Modelled leaching times are about ten times lower than the age of the samples, suggesting that the rate of trace element leaching into tooth enamel slows down or even halts during the burial period. • Micro X-Ray Fluorescence scanning reveals trace element variability in archaeological tooth enamel. • Fe, Zn, Sr and Pb leach into tooth enamel during diagenesis. • Diffusion-advection models reconstruct leaching parameters and pristine element concentrations. • Rates and depth of leaching differ per element and between burial types. • Outer enamel and enamel-dentine junction should be avoided when sampling enamel for palaeo reconstructions. [ABSTRACT FROM AUTHOR]