Strontium Isotope Ratios Research Articles

Comparison of powdered enamel sample pretreatment methods for strontium isotope analysis

Most researchers assume minimal impact of pretreatment on strontium isotope ratios ( 87 Sr/ 86 Sr) for bones and teeth, and methods vary tremendously. We compared 14 pretreatment methods, including no prep other than powdering enamel, ashing, soaking in water, an oxidizing agent (bleach or hydrogen peroxide) or acetic acid (0.1 M, 1.0 M, and 1.0 M buffered with calcium acetate), and a combination of these steps. We prepared and analyzed aliquots of powdered molar enamel from three proboscideans (one modern captive Indian elephant, Elephas maximus indicus ; one Pleistocene mastodon, Mammut americanum ; and one Miocene gomphothere, Afrochoerodon kisumuensis ). Each pretreatment was performed in triplicate and we measured 87 Sr/ 86 Sr, Sr concentration, and uranium (U) concentration, using the same lab space and instrumentation for all samples. Variability in 87 Sr/ 86 Sr and Sr and U concentrations was considerable across pretreatments. Mean 87 Sr/ 86 Sr across methods ranged from 0.70999 to 0.71029 for the modern tooth, 0.71458 to 0.71502 for the Pleistocene tooth, and 0.70804 to 0.70817 for the Miocene tooth. The modern tooth contained the least Sr and negligible U. The Pleistocene tooth contained slightly more Sr and measurable amounts of U, and the Miocene tooth had approximately 5x more Sr and U than the Pleistocene tooth. For all three teeth, variance in 87 Sr/ 86 Sr, Sr concentrations, and U concentrations among replicates was statistically indistinguishable across pretreatments, but there were apparent differences among pretreatments for the modern and Pleistocene teeth. Both contained relatively little Sr, and it is possible that small amounts of exogenous Sr from reagents, building materials or dust affected some replicates for some pretreatments. For the modern tooth, median 87 Sr/ 86 Sr varied considerably (but statistically insignificantly) across pretreatments. For the Pleistocene tooth, variability in median 87 Sr/ 86 Sr was also considerable; some pretreatments were statistically distinct but there were no obvious patterns among methods. For the Miocene tooth, variability in median 87 Sr/ 86 Sr was much smaller, but there were significant differences among pretreatments. Most pretreatments yielded 87 Sr/ 86 Sr and Sr concentrations comparable to, or lower than, untreated powder, suggesting selective removal of exogenous material with high 87 Sr/ 86 Sr. Further evaluation of the mechanisms driving isotopic variability both within and among pretreatment methods is warranted. Researchers should clearly report their methods and avoid combining data obtained using different methods. Small differences in 87 Sr/ 86 Sr could impact data interpretations, especially in areas where isotopic variability is low.

Strontium isotope ratios in kidney stones reveal the environmental implications for humans in Beijing, China.

Kidney stones are a common disease that threatens human health on a global scale and are closely related to the contemporary environment. The strontium isotope ratio (87Sr/86Sr) has been widely used to trace the migration of ancient humans through bones and teeth, which recorded their bioavailable Sr from the environment. However, no 87Sr/86Sr data for kidney stones have been reported. Therefore, this study explored the Sr content of kidney stones and reported their 87Sr/86Sr data for the first time to reflect the environmental implications for humans; 66 calcium oxalate kidney stones collected in Beijing were measured for calcium (Ca), magnesium (Mg) and strontium (Sr) content to explore Sr distribution behavior in kidney stones, and 17 samples were tested for strontium isotopes. Ca and Mg had a joint effect on the Sr content of kidney stones, with magnesium having a stronger effect, whereas 87Sr/86Sr values were unaffected by these elements. The 87Sr/86Sr values of kidney stones ranged from 0.709662 to 0.710990, within the range of environmental soil and water in Beijing. Drinking water and surface soils (representing food sources) mainly contributed to the bioavailable Sr of kidney stones, while sea spray and dust storm did not. This study is the first to report 87Sr/86Sr values for kidney stones. Evidence of Sr isotope ratios in kidney stones reveals environmental implications for humans and bioavailable Sr sources, demonstrating a great potential of Sr isotope ratios at the intersection of life and environmental sciences.

Isotope geochemistry as a natural tag of fish in Patagonian freshwater environments: The invasive Chinook salmon case

Patagonian aquatic environments have been invaded since the end of the last century by different species of salmonids. Knowing the natal origin and homing/straying rate of the salmonids in colonised environments is essential to understanding the dispersal mechanisms and developing management plans. In the last two decades, Chinook salmon Oncorhynchus tshawytscha showed the greatest natural dispersal capacity in Patagonia. The main goal of this study was to evaluate the environmental strontium isotope ratio (87Sr/86Sr) as a potential natural tag to infer the natal origin and ontogenetic habitat use of salmonids in Patagonia, specifically Chinook salmon. 87Sr/86Sr ratio was determined in water samples from 26 sites distributed in 14 Atlantic and Pacific basins in low and high water seasons. Environmental 87Sr/86Sr showed greater spatial than temporal variation, revealing great potential as a tool to infer the natal origin and life history of several migratory fish species in Patagonia. Otolith core-to-edge 87Sr/86Sr profiles were also analysed in 108 Chinook salmon from six basins. A cluster analysis based on the Unweighted Pair Group method (UPGMA) and Euclidean distances without prior classification grouped the sampled rivers into five main groups with significantly different (p < 0.05) isotopic ratios, sometimes integrated basins with different slopes (Atlantic or Pacific). The cluster analysis based on the natal 87Sr/86Sr period in otolith (∼natal origin) showed clear segregation between the Atlantic and Pacific samples. A mismatch between water and otolith natal 87Sr/86Sr ratio was detected in some Atlantic basins (e.g. De las Vueltas River in Santa Cruz Basin) and Pacific (e.g. Liquiñe Basin) and, which could be explained either by straying behaviours or by large geochemical variability between tributaries, within river systems. Our results showed that 87Sr/86Sr is a useful natural tag to trace the life history of migratory fishes in Patagonia, especially for invasive species such as Chinook salmon.

Metals and metal isotopes incorporation in insect wings: Implications for geolocation and pollution exposure

Anthropogenic activities are exposing insects to elevated levels of toxic metals and are altering the bioavailability of essential metals. Metals and metal isotopes have also become promising tools for the geolocation of migratory insects. Understanding the pathways of metal incorporation in insect tissues is thus important for assessing the role of metals in insect physiology and ecology and for the development of metals and metal isotopes as geolocation tools. We conducted a diet-switching experiment on monarch butterflies [Danaus plexippus (L.)] with controlled larval and adult diets to evaluate the sources of 23 metals and metalloids, strontium isotopes, and lead isotopes to insect wing tissues over a period of 8 weeks. Concentrations of Ca, Co, Mo, and Sb differed between the sexes or with body mass. Ni and Zn bioaccumulated in the insect wing tissues over time, likely from the adult diet, while increases in Al, Cr, Cd, Cu, Fe, and Pb were, at least partially, from external sources (i.e., dust aerosols). Bioaccumulation of Pb in the monarch wings was confirmed by Pb isotopes to mainly be sourced from external anthropogenic sources, revealing the potential of Pb isotopes to become an indicator and tracer of metal pollution exposure along migratory paths. Concentrations of Ba, Cs, Mg, Na, Rb, Sr, Ti, Tl, and U appeared to be unaffected by intrinsic factors or additions of metals from adult dietary or external sources, and their potential for geolocation should be further explored. Strontium isotope ratios remained indicative of the larval diet, at least in males, supporting its potential as a geolocation tool. However, the difference in strontium isotope ratios between sexes, as well as the possibility of external contamination by wetting, requires further investigation. Our results demonstrate the complexity of metal incorporation processes in insects and the value of studying metals to develop new tools to quantify pollution exposure, metal toxicity, micronutrient uptake, and insect mobility.

Study on the strontium isotope standard in pig teeth excavated from Zaoshugounao site, Shaanxi Province of China

AbstractIn archaeology, strontium isotope analysis is developing into an efficient scientific technique for tracing the movement of prehistoric humans and animals. Determining the local bioavailable 87Sr/86Sr ratio range is the key to distinguishing whether the human or animal is indigenous to the local area. It has been shown that the 87Sr/86Sr ratio in the enamel of pigs can be an excellent sample to determine the range of local strontium isotope ratio at the site. However, pigs may not be all local at the site, and there is no special study on whether pigs’ different ages and tooth types impact the local strontium isotope characteristics. In this paper, the tooth enamel of 19 pigs from the Zaoshugounao site for strontium isotope ratio (87Sr/86Sr) by multicollector–inductively coupled plasma mass spectrometry. There were no significant differences in 87Sr/86Sr ratios of local pigs at different months and different molar types, which did not affect the determination of the local strontium isotope standard. Based on the local strontium isotope ratio range (0.711056–0.711476), we found that five pigs were non‐local. The Jing and Wei river basins (in Guanzhong basin) and northern Shaanxi are likely sources of non‐pigs.

Sr analyses from only known Scandinavian cremation cemetery in Britain illuminate early Viking journey with horse and dog across the North Sea.

The barrow cemetery at Heath Wood, Derbyshire, is the only known Viking cremation cemetery in the British Isles. It dates to the late ninth century and is associated with the over-wintering of the Viking Great Army at nearby Repton in AD 873-4. Only the cremated remains of three humans and of a few animals are still available for research. Using strontium content and isotope ratios of these three people and three animals-a horse, a dog and a possible pig-this paper investigates the individuals' residential origins. The results demonstrate that strontium isotope ratios of one of the adults and the non-adult are compatible with a local origin, while the other adult and all three animals are not. In conjunction with the archaeological context, the strontium isotope ratios indicate that these individuals most likely originated from the area of the Baltic Shield-and that they died soon after arrival in Britain. This discovery constitutes the first solid scientific evidence that Scandinavians crossed the North Sea with horses, dogs and other animals as early as the ninth century AD.

National-scale distribution of strontium isotope ratios in environmental samples from South Korea and its implications for provenance studies

Successful application and accurate interpretation of strontium (Sr) isotope ratios (87Sr/86Sr) requires underlying information about the large-scale variabilities in their signatures from a variety of environmental samples, which can be correlated with the Sr isotopic signatures of underlying local geology. In this national-scale study, we analyzed 87Sr/86Sr in soil, plants, stream water, and Chinese mystery snail (Cipangopaludina chinensis) shells collected from South Korea to evaluate large-scale spatial variabilities, interpret relationships among isotopic signatures of various sample types, and generate spatial distribution isoscapes reflecting the heterogeneity of isotopic signatures across South Korea. Non-parametric comparisons among environmental samples showed non-significant differences in their isotopic ratios. The 87Sr/86Sr of plant and soil samples were strongly correlated (R2adj = 0.93), suggesting that both reflect national-scale lithological properties. Similarly, the 87Sr/86Sr of shells showed strong correlations with the 87Sr/86Sr of both plant and soil samples (R2adj = 0.90). The 87Sr/86Sr signatures of environmental samples in this study aligned with expected Sr isotopic values and generally reflected local geology. Spatial distribution maps of samples showed similar 87Sr/86Sr spatial patterns, with high radiogenic values from granitic and granitic gneiss rocks systems and low radiogenic values from volcanic and sedimentary rock systems. Stream water samples showed significant correlations with soil and plant isotopic ratios, but with a low coefficient of determination (R2adj = 0.68). The deviations were much larger for samples with 87Sr/86Sr > 0.720. Further study is needed to improve the accuracy of baseline determination and interpretation of stream water isotopic variations.

Using the geographic detector model to identify factors controlling the bioavailability of Sr isotopes in China

Strontium isotope ratios (87Sr/86Sr) are a widely applied tool in provenance applications in archaeology, paleoecology, forensics, and food science. Bedrock Sr is naturally and anthropogenically transferred to other reservoirs on the Earth’s surface through interactions with the hydrosphere, atmosphere, and biosphere. We attempt to reassess the contribution of the spatial distribution of bioavailable strontium isotopes using the geographic detector model (GDM). Our study reveals that the watershed factor explains 50.35% of the spatial variation of bioavailable Sr isotopes, while the climate, terrain, geology, and soil explain 14.41%, 4.94%, 4.63%, and 4.70% of the spatial variation of bioavailable Sr isotopes. The factors influencing the spatial variation of bioavailable Sr isotopes in China were ranked as follows: basin &amp;gt; climate &amp;gt; terrain &amp;gt; geology &amp;gt; soil type. The nonlinear enhancements of the interactions between the watershed and geology explained 59.90% of the spatial variation in bioavailable Sr isotopes, indicating that natural processes still control the bioavailability of strontium isotopes in China. Based on the synthesized river-water isotopic data, the large-scale bioavailable Sr isoscape discussed herein can be useful for migratory studies in China. The enrichment of strontium isotope data to refine Sr isotopes, as well as the search for better data on possible controlling factors, will make the analysis more comprehensive and provide a solid foundation for explaining strontium isotope migration.

Natal Contributions of Kokanee Salmon to Flaming Gorge Reservoir, Wyoming–Utah: An Evaluation Using Otolith Microchemistry

Abstract In a system that uses supplemental stocking to enhance a fishery that serves a dual purpose, an understanding of the contributions from natural and hatchery-produced fish is important so that hatchery resources can be appropriately allocated. Kokanee Oncorhynchus nerka were first stocked in Flaming Gorge Reservoir (FGR), Wyoming–Utah, in 1963 and serve a dual purpose as a prey resource and sport fish. Although natural recruitment occurs in the reservoir, a supplemental stocking program was initiated in 1991. We sought to identify the natal origin (i.e., natural, hatchery) of kokanee in FGR using otolith microchemistry. We evaluated return to the creel, composition of spawning aggregates, and growth of kokanee in FGR and focused on differences associated with natal origin. We analyzed kokanee otoliths that we collected from hatcheries (n = 60) and FGR (n = 1,003) for the strontium isotope ratio, 87Sr/86Sr, using laser ablation and a multicollector inductively coupled plasma mass spectrometer. We conducted Kruskal–Wallis tests to compare the strontium isotope ratios from the otolith edge of kokanee that we sampled from hatcheries and FGR. Based on 87Sr/86Sr ratios, we could distinguish natural-origin kokanee from 11 of the 12 hatcheries (P &amp;lt; 0.01); however, the Wigwam Hatchery was not significantly different from FGR (P = 0.84). We used model-based discriminant function analysis to assign natal origins for kokanee caught in FGR. Hatchery contribution to the population at large varied from 21 to 50% among year classes from 2014 to 2018. The percentage of hatchery origin kokanee in the creel (18–50%) was similar to what we observed in the population. Hatchery-produced kokanee contributed a higher proportion to tributary-spawning aggregates (40–90%) than shoreline-spawning aggregates (19–58%) by sample year. Growth of natural and hatchery kokanee was similar, suggesting similar performance in the system. Results from this study identify that hatchery supplementation contributes to the population and recreational harvest of kokanee in FGR. This research also provides insight into the ecology of kokanee that is useful for better understanding kokanee population dynamics in reservoir systems.

Determining the geographical origin of durum wheat samples by combining strontium isotope ratio and multielemental analyses

AbstractBackground and objectivesDetermining the geographical origin of durum wheat is an important and emerging challenge because consumers perceive added value of final products (e.g., pasta) depending on the origin. Declaration of geographical origin is also an emerging requirement of specific national regulations. Among analytical strategies for determining geographical origins of samples, isotopic techniques based on both light and radiogenic isotope targets stand out, despite limitations of applicability, validation and assessment of interyear variability.FindingsIn this study, 87Sr/86Sr isotopic analysis was successfully used to discriminate Italian (ITA) samples versus rest‐of‐the world (RoW) samples and subsequently integrated with an elemental analysis (ICP‒MS) on 75 elements. A tiered approach was finally adopted in which the results of the 87Sr/86Sr analysis were input to a second step of support vector machine classification modeling (SVMC) based on the Al, Mn, Mo, P, S, Ti, Y, and Zn percentages in each sample. This model was tested against a blind group of samples with overall satisfactory performance.ConclusionValuable information from multielemental and stable isotope ratio analyses was collected for authentic samples from different Italian, European, and non‐European regions harvested during different years.Significance and noveltyThis study demonstrates the potential and validity of an innovative combined multielemental and strontium isotope ratio approach for the geographic discrimination of durum wheat on a global scale: the developed predictive model has already been routinely employed to control industrial lots.

Hydrochemical and isotopic baselines for understanding hydrological processes across Macquarie Island.

Isotopic and hydrochemical data from lakes provide direct information on catchment response to changing rainfall, evaporation, nutrient cycling, and the health of ecosystems. These techniques have not been widely applied to lakes in the Southern Hemisphere high latitudes, including Southern Ocean Islands (SOIs) experiencing rapid, significant shifts in climate. Historical work has highlighted the localised nature of geochemical drivers in controlling the hydrochemical evolution of lakes, such as geology, sea spray contribution, vegetation, geographical location, and ice cover extent. The role of groundwater in lake hydrology and hydrochemistry has not been identified until now, and its omission will have major implications for interpreting soil-water-air processes affecting lakes. Here we present the first comprehensive, island-wide hydrochemical and isotopic survey of lakes on a SOI. Forty lakes were examined across Macquarie Island, using comparable methods to identify key environmental processes and their geochemical drivers. Methods include stable carbon (δ13CDOC: dissolved organic carbon and δ13CDIC: dissolved inorganic carbon), oxygen (δ18O), hydrogen (δ2H) and strontium isotopic ratios (87Sr/86Sr) in water. These provide essential baseline data for hydrological, biological, and geochemical lake processes. Lakes on the western side of the island are influenced by sea spray aerosols. In general, it was found that lakes at higher elevations are dilute and those located in lower elevation catchments have experienced more water-rock interactions. The hydrochemical and isotopic tracers suggest that lakes in lower elevations contain more terrestrial sourced ions that may be contributed from groundwater. Increasing temperatures and changing rainfall patterns predicted for the region will lead to shifts in nutrient cycles, and impact the island's unique ecosystems. Future research will focus on long-term monitoring to understand seasonal, annual, and long-term variability to test fundamental hypotheses concerning ecosystem function and the consequences of environmental change on SOIs.

Hydrogeochemical modeling of the spatiotemporal variations in 87Sr/86Sr isotope ratios and Sr concentrations of spring waters in a headwater catchment (Strengbach CZO–France)

The variations in strontium (Sr) isotope ratios in river waters at a regional scale are usually discussed in terms of lithological diversity constituting the watershed bedrock. To discuss the origin of the spatiotemporal variations in Sr concentrations and isotopic compositions of spring waters at the headwater watershed scale, we analyzed the 87Sr/86Sr and 143Nd/144Nd isotopic ratios of the main constitutive minerals of the granitic bedrock of the Strengbach Critical Zone Observatory (CZO) and developed coupled hydrogeochemical modeling integrating the Sr concentration and isotopic composition. The simulation results show that the long-term (1990–2010) decrease in Sr concentrations in the CS springs of the Strengbach catchment can be explained by the response of mineral weathering along the water pathway to the pH increase that affected the incoming solutions to the weathering system during the same period. This pH increase reduces the water path proportion marked by a high flux of apatite and biotite dissolution. Thus, it reduces the Sr concentration of the outgoing spring waters. The different responses of the various CS springs to the incoming solutions' pH increase can be explained by the more or less long residence time of the water in the bedrock for the different springs. The analytical data also confirm that the 87Sr/86Sr isotope ratios of the CS springs varied little or not at all on average from 1990 to 2010. In contrast, they varied significantly during a hydrological cycle and from one spring to another. The constancy of the average 87Sr/86Sr isotope ratios over several years is explained by a granitic bedrock water path sufficiently long for soil solution pH variations to no longer influence the emergence of the spring. The simulation results also show that the isotopic variations observed in the CS springs during a hydrological cycle can be explained by differences in the transit time of the water in the substratum between high and low waters and the modifications that they entail on the degree of saturation of the water with respect to biotite and apatite. These differences do not need to be explained by differences in the mineralogy of the rocks drained by waters between high and low discharge periods. Similarly, the different average isotope ratios from one spring to another can be explained by the more or less long transit times in the bedrock of the waters feeding these different springs. Again, it is not necessary to explain them by local lithological differences from one spring to another. These different results highlight that at the scale of an upstream basin such as the Strengbach, the Sr isotopic variations observed in the CS springs should not systematically indicate lithological differences in the rock. The development of coupled isotope modeling approaches should help to disentangle the part of this process relating to hydrological processes in the isotopic variability of the spring waters.

The Truth of Unusual Deaths under Military Expansion: Evidence from the Stable Isotopes of a Human Skull Ditch in the Capital City of the Early Shang Dynasty.

The site of Zhengzhou Shang City (ca. 1509-1315 cal. BC) was the capital of the early Shang Dynasty in China. Archaeological excavations have unearthed a ditch containing approximately one hundred unusual dead human skulls in the rammed-earth foundations of the palace area. The identity and origin of the skulls have long been disputed. In this work, strontium, carbon and nitrogen stable isotope analyses were carried out on 11 human skulls and 1 tooth from the ditch, as well as on 11 human bones, 11 human teeth from the ordinary tombs and 10 pig teeth from the Zhengzhou Shang City site. We determined that, in Zhengzhou Shang City, the local strontium isotope ratio ranges from 0.711606 to 0.711884, and ordinary inhabitants consumed mainly C4 plants supplemented by C3 plants. Moreover, humans buried in the ditch have 87Sr/86Sr values from 0.711335 to 0.711741 and consumed only C4 plants. Combining the isotopic data with the archaeological and cultural context, it is concluded that the unusual human skulls in the ditch are most likely those of prisoners of war captured by the central forces conquering the Xiaomintun area of Anyang in the early Shang Dynasty. The results provide valuable insight into the history of violence and military warfare in the early Chinese dynasty.

Combining conventional tree-ring measurements with wood anatomy and strontium isotope analyses enables dendroprovenancing at the local scale

Dendroprovenancing provides critical information regarding the origin of wood, allowing further insights into economic exploitation strategies and source regions of timber products. Traditionally, dendroprovenancing relies on pattern-matching of tree rings, but its spatial resolution is limited by the geographical coverage of species-specific chronologies available for crossdating and, in the case of short-distance trades, by scarce environmental variability. Here, we present an approach to provenance timber with high spatial resolution from forested areas that have been exploited intensively throughout history, with the aim to understand the sustainability of the various woodland management practices used to supply timber products. To this end, we combined tree-ring width (TRW), wood anatomical and geochemical analyses in addition to multivariate statistical validation procedures to trace the origin of living oak trees (Quercus robur) sampled in four stands located within a 30-km radius around the city of Limoges (Haute-Vienne, France). We demonstrate that TRW and wood anatomical variables (and in particular cell density) robustly discriminate the eastern from the western site, while failing to trace the origin of trees from the northern and southern sites. Here, strontium isotopic ratios (87Sr/86Sr) and Ca concentrations identify clusters of trees which could not be identified with TRW or wood anatomy. Ultimately, our study demonstrates that the coupling of wood anatomy with geochemical signatures allows to correctly pinpoint the origin of trees. Given the small geographic scale of our study and the limited differences in elevation and climate between study sites, our results are particularly promising for future dendroprovenancing studies. We thus conclude that the combination of multiple approaches will not only increase the accuracy of dendroprovenancing studies at local scales, but could also be implemented at much larger scales to identify trends in historic timber supply throughout Europe.

Diet and mobility in early medieval coastal Belgium: Challenges of interpreting multi-isotopic data

During the early medieval period (5th–9th century CE), the North Sea coastal societies were involved in long distance maritime trade relations, which resulted in a pronounced mobility of individuals throughout the North Sea area. This work presents the first isotope data from human remains on diet and mobility from early medieval Belgian coastal populations. A total of 23 out of 51 excavated individuals from the archaeological site of Koksijde, Belgium (7th–8th century AD), was selected for isotope and elemental analyses (δ13Ccol, δ15N, δ18OP, δ13Cap, δ18OC, 87Sr/86Sr and [Sr]). The high δ15N values of part of the individuals buried at Koksijde indicate that high trophic level ranked fish was included in their diets, suggesting an intensive exploitation of marine food sources. The δ18O values are not compatible with the predicted ‘local’ values while the strontium isotope ratios have values close to that of seawater (0.7092). Either the actual oxygen isotope values in early medieval Belgium are offset by 1 or 2‰ compared to the current meteoric water predictions, or the population came from somewhere else. Whether or not this was linked to the population’s mobility is difficult to assess based on their δ18O and 87Sr/86Sr values. Nonetheless, the study of the population at Koksijde provides new insights into the lives of the early medieval coastal Belgian societies.

A Neandertal dietary conundrum: Insights provided by tooth enamel Zn isotopes from Gabasa, Spain

The characterization of Neandertals' diets has mostly relied on nitrogen isotope analyses of bone and tooth collagen. However, few nitrogen isotope data have been recovered from bones or teeth from Iberia due to poor collagen preservation at Paleolithic sites in the region. Zinc isotopes have been shown to be a reliable method for reconstructing trophic levels in the absence of organic matter preservation. Here, we present the results of zinc (Zn), strontium (Sr), carbon (C), and oxygen (O) isotope and trace element ratio analysis measured in dental enamel on a Pleistocene food web in Gabasa, Spain, to characterize the diet and ecology of a Middle Paleolithic Neandertal individual. Based on the extremely low δ66Zn value observed in the Neandertal's tooth enamel, our results support the interpretation of Neandertals as carnivores as already suggested by δ15N isotope values of specimens from other regions. Further work could help identify if such isotopic peculiarities (lowest δ66Zn and highest δ15N of the food web) are due to a metabolic and/or dietary specificity of the Neandertals.

Combined use of statistical Bayesian model and strontium isotopes deciphering the high complexity groundwater flow in the Guarani Aquifer System (GAS)

The Guarani Aquifer System (GAS) is one of the most important groundwater reservoirs in Latin America. Even though its geological aspects and hydraulic behavior are deeply studied, questions regarding hydraulic connections between the GAS and the overlying (SGAS) and underlying (PRE-GAS) aquifers within the Paraná Sedimentary Basin geological framework are recently being pursued. This paper presents a new tracer approach within the GAS, incorporating strontium isotopes in a statistical Bayesian model. The multi-pronged approach is used to quantify mixing proportions and identify different processes related to water-rock interaction and hydrochemical data. Strontium isotopic ratio ranged from enriched values (>0.711) associated with higher GAS groundwater contribution, to lower values associated with contribution from the SGAS (∼0.707) and PRE-GAS (∼0.709) units, as well as isotopic fingerprint associated with direct rainwater recharge. As groundwater flows through the GAS, the mixing proportions between the end-members changes along with the hydrogeochemical evolution. Near recharge zones, GAS represents the dominant source (38% ± 10%), followed by PRE-GAS (28% ± 16%), SGAS (19% ± 11%) and rainwater (14% ± 10%). In transition waters between outcrop and confined areas, the GAS contribution remains dominant (48% ± 9%), followed by PRE-GAS (37% ± 14%) and SGAS (14% ± 8%). In the GAS confined zone, where contributions from rainwater and SGAS is absent, 87Sr/86Sr ratio is more associated with waters from PRE-GAS (53% ± 16%) than from GAS (46% ± 16%). This behavior indicates that groundwater flow in the GAS represent a more complex and vulnerable groundwater mixing system, closely related to the regional geological context of a closed intracratonic basin, than previously understood. The use of strontium isotopes as a hydrogeochemical tracer applied in a statistical mixing model, contributes to a more refined understanding of regional groundwater flow and water origin in the GAS.

Water-rock exchange of Sr isotopes evaluated through a reactive transport model: Application to the El Chichón hydrothermal system

The strontium isotope ratio (87Sr/86Sr) is a natural tracer commonly used to determine water sources, water flow trajectories, and mixing relationships. In high-temperature hydrothermal systems, the low solubility of retrograde minerals such as calcite and anhydrite may significantly reduce the dissolved Sr concentration. Further contribution of Sr along the flow path from isotopically distinct sources will alter and potentially mask the original Sr isotopic signature of the fluid, limiting the potential of 87Sr/86Sr data for reconstructing fluid flow patterns. This study investigates the tracing potential of 87Sr/86Sr in terms of fluid circulation within the El Chichón volcano hydrothermal system. Although limestone aquifers are evidenced in the region, the 87Sr/86Sr signature of most thermal fluids from the volcano does not indicate any major Sr contribution from such lithologies, but rather reveals that Sr is inherited from volcanic rocks. An isotope-enabled reactive transport model is performed to investigate under which conditions a connection between the limestone and volcanic aquifers is compatible with chemical and Sr isotopic compositions of the thermal springs. Results indicate that the 87Sr/86Sr signature of a sedimentary fluid with moderate Sr concentration can be completely modified into a magmatic signature after interacting with Sr-rich primary minerals, such as plagioclases, within short period of times (<1 year). Primary minerals release magmatic Sr to the fluid while secondary minerals (such as calcite) progressively precipitate and remove the initial sedimentary Sr. The El Chichón hydrothermal system hence represents a case where the 87Sr/86Sr of most springs does not keep any memory of the circulation through the sedimentary basement, as magmatic Sr dominates the isotopic signature. A certain analogy exists with hydrothermal fluids vented at oceanic spreading centers, whose 87Sr/86Sr signature departs from seawater and reflects Sr inherited from water-basalt interaction.

Stable carbon and oxygen isotope geochemistry as provenance indicator for the picture stones on Gotland (Sweden)

ABSTRACT The picture stones from Gotland are one of the most famous and exceptional groups of monuments known from Swedish Prehistory. These carved memorial stones and their extraordinarily rich imagery are a unique source for the study of Late Iron and Viking Age culture and in particular Scandinavian pre-Christian religions. The Gotlandic picture stones are mainly made from the thickly layered limestones surrounding the reefs and bioherms of Gotland’s carbonate platform from the middle part of the Silurian (latest Llandovery to Ludlow, Telychian – Ludfordian). However, the exact origins of the picture stones’ raw materials on Gotland have remained undetermined. In this paper, we investigate the geological origin of the raw material by isotope geochemistry. Whereas the oxygen (δ18O) and strontium isotope ratio (87Sr/86Sr) were strongly altered by diagenesis the carbon isotope ratio (δ13C) is quite stable. Because the different geological units on Gotland show specific isotope signatures, the δ13C values from picture stones can be used to assign them to the respective geological unit, and thus to the source area of the raw material. This also allows for an estimation of transport distance minima between the raw material source area and the find place of each sampled picture stone. Most of the picture stones seem to be produced from local material with short transport distances, less than 10 km and only a few were transported at a far distance exceeding 10 km. In summary, the transport distance was dependent mostly on the local availability of picture-stone-suitable rocks.

Livestock supply to an imperial sacrificial site of the early Chinese empires evidenced by strontium isotope ratios

A newly excavated ritual site, Xuechi, exposed abundant sacrificial livestock, allowing to understand the supplies and managements of livestock during the early Chinese Qin-Han Empires. Here we reported animal enamel 87Sr/86Sr values from the Xuechi site that are obviously higher than those of local snails and surface water, as well as calcites of the Chinese Loess Plateau (CLP) where the site was located, strongly suggesting that these sacrificial animals were not raised in the vicinity of the site. The regional bioavailable 87Sr/86Sr isoscape further indicates that some livestock were probably derived more than one hundred kilometers away, suggesting a complex social network for recruiting and managing the sacrificial activities. In the context of other Neolithic-Bronze Age records on the CLP, an increasing trend in variation of faunal 87Sr/86Sr values shows a robust correlation to Chinese states’ trajectory, in concordance with the territorial expansion model for state formation.