Strontium Isotope Ratios Research Articles

Sr–Nd Isotopic Evidence of a Heterogeneous Magmatic Source of Alkaline–Carbonatite Rocks of the Odikhincha Alkaline–Carbonatite Massif (Maimecha-Kotui Province, Siberia)

This study focuses on the igneous rocks composing the Odikhincha massif. The massif is typical ring alkaline–ultrabasic massif with carbonatites, second largest in the Maimecha-Kotui province. The Sr-Nd isotopic values of the traps of the Arydzhang Formation and the host dolomites were also determined for comparison. The Rb–Sr isotope system of phlogopite and calcite from the Od-16-19 carbonatite of the Odikhincha massif is disturbed; the obtained age on the mineral isochrone (245 ± 3 Ma) is close to the time of formation of the Siberian traps and rocks of the ultrabasic–alkaline Maimecha-Kotui complex, but the large scatter of analytical points (MSWD = 22) does not allow this date to be considered as reliable. The disturbance of the isotope system is probably related to the fact that the strontium isotope ratio in the fluid was not constant during autometasomatic phlogopitization of carbonatite. The U–Pb isotopic system of titanite and perovskite from the same carbonatite sample Od-16-19 also appeared to be disturbed, since data points formed discordia. The U–Pb age obtained for titanite and perovskite are 244 ± 5 Ma (MSWD = 1.8) and 247 ± 18 Ma (MSWD = 4), respectively. Apparently, the age values provided by the two isotopic systems (245 ± 3 Ma by Rb–Sr and 247 ± 18 and 244 ± 5 Ma by U–Pb) are consistent with each other and reflect the time of metasomatic processes, i.e., phlogopitization and iolitization. Rb–Sr and Sm–Nd isotope data for ultrabasic–alkaline intrusive rocks with carbonatites of the Odikhincha massif and volcanics of the Arydzhang Formation indicate an enriched, relative to the composition of the convecting mantle, isotopically heterogeneous source of their parent melts. This source could be a combination of ultrabasic mantle rocks and rocks of basic composition (basites). The latter played the role of an enriched component. No signs of contamination of the melts with the host sedimentary rocks in situ were found, however, variations of Sr and Nd isotopic ratios in the rocks of the Odikhincha massif may indicate that during the introduction of deep magmas their interaction and substance exchange with the surrounding rocks of the lithosphere continued up to complete solidification of the melts, as indicated by the nature of local isotopic heterogeneity within the Odikhincha intrusion.

Sulfate isotope composition of Messinian evaporites in the Piedmont basin (Italy)

The Piedmont basin (NW Italy) records a Messinian Salinity Crisis (MSC) succession including a selenite gypsum deposit assigned to the Primary Lower Gypsum (PLG, MSC stage 1). Strontium isotope ratios are in the range of the PLG deposits of the Mediterranean area. Sulfate isotope compositions of vertically oriented selenite gypsum beds, in the lower part of the succession, are similar to those reported in other PLG deposits. However, flattened branching selenite cones in the upper part show higher isotope compositions, mainly in δ34S values, suggesting intense BSR conditions, stronger than reported in other PLG deposits. We interpret this chemical shift during deposition of the upper part of the PLG as the result of increased marine restriction assisted by the marginal position of this basin in the Adriatic Gulf during the Apennine and Alpine uplifts.

Origin of Hydrothermal Barite in Polymetallic Veins and Carbonate-Hosted Deposits of the Cyclades Continental Back Arc

Abstract Polymetallic veins and breccias and carbonate-replacement ore deposits in the Cyclades continental back arc, Greece, formed from a range of fluid and metal sources strongly influenced by the dynamics of the late Mesozoic-Cenozoic Hellenic subduction system. These complexities are recorded in the isotopic signatures of hydrothermal barite. We investigated 17 mineral occurrences on four Cycladic islands and from Lavrion on the mainland. Here, barite occurs in almost all deposit types of Miocene to Quaternary age. We used a multiple isotope and geochemical approach to characterize the barite in each deposit, including mineral separate analysis of δ34S and δ18O and laser ablation-inductively coupled plasma-mass spectrometry of 87Sr/86Sr and δ34S. Barite from carbonate-hosted vein and breccia Pb-Zn-Ag mineralization on Lavrion has a wide range of δ34S (2–20‰) and δ18O (10–15‰) values, reflecting a mix of magmatic and surface-derived fluids that have exchanged with isotopically heavy oxygen in the carbonate host rock. Sulfur (δ34S = 10–13‰) and oxygen (δ18O = 9–13‰) values of barite from the carbonate-hosted vein iron and barite mineralization on Serifos are permissive of a magmatic sulfate component. Barite from epithermal base and/or precious metal deposits on Milos has δ34S (17–28‰) and δ18O (9–11‰) values that are similar to modern seawater. In contrast, barite from vein-type deposits on Antiparos and Mykonos has a wide range of δ34S (16–37‰) and δ18O (4–12‰) values, indicating a seawater sulfate source modified by mixing or equilibration of the hydrothermal fluids with the host rocks. Strontium isotope ratios of barite vary regionally, with 87Sr/86Sr ≥ 0.711 in the central Cyclades and 87Sr/86Sr ≤ 0.711 in the west Cyclades, confirming the strong influence of upper crustal rocks on the sources of fluids, Sr, and Ba in the formation of ore.

Use of strontium isotope ratios in potential geolocation of Ajnala skeletal remains: a forensic archeological study.

Stable isotope methods for provenance of unidentified human remains are relatively a newer field of enquiry in forensic archeology. It is of great interest for forensic experts these days. The application of strontium isotope analyses for estimating geolocation of archeological remains is of great interest in bioarcheology and modern forensics. The strontium (Sr) isotope composition of human bones and teeth has been widely used to reconstruct an individual's geo-affiliation, residential mobility, and migration history. Thousands of unknown human remains, reportedly belonging to 282 Indian soldiers of 26th Native Bengal regiment and killed in 1857, were exhumed non-scientifically from an abandoned well situated underneath a religious structure at Ajnala (Amritsar, India). Whether these remains belonged to the individuals, local or non-local to the site, was the important forensic archeological question to be answered by doing their thorough forensic anthropological examinations. In the present study, 27 mandibular teeth (18s molars, 6 first molars, and 3 premolars) collected from the Ajnala skeletal assemblage were processed for strontium isotope analysis, and the measured ratios were compared with published isotope baseline data to estimate the locality status of these remains. The Sr isotopic values were concentrated in the range of 0.7175 to 0.7270. The comparative analysis of isotopic ratios revealed that most individuals buried in the Ajnala well have 87Sr/86Sr values close to the river as well as groundwater of the Gangetic plain (less radiogenic 87Sr/86Sr ~ 0.716); most likely originated near Varanasi (Uttar Pradesh, India) region, whereas the individuals with higher 87Sr/86Sr ratios (~ 0.7200) probably resided in the West Bengal and Bihar areas where the river as well as groundwater of the Gangetic plain is relatively more radiogenic. Thus, the strontium isotope results reveal that the Ajnala individuals did not grow up or live in the Amritsar region during their childhood, and this observation complemented the previous forensic anthropological and molecular findings. There is very little Indian data on the bioavailable strontium, so the inferences from the present study estimating Sr isotope abundances are expected to provide baseline data for future forensic provenance studies that will contribute to the global efforts of mapping Sr isotope variations by the isotope community.

Between valleys, plateaus, and mountains: unveiling livestock altitudinal mobility in the Iron Age Iberian Peninsula (3rd c. BC) through a multi-isotope approach

Seasonal altitudinal mobility has been a key practice among pastoral societies in the north-eastern Iberian Peninsula to cope with the unpredictable Mediterranean climate. The existence of a massive and regulated mobile herding system in this area dates back to the 12th century. Nevertheless, early herd connections between the lowlands and the Pyrenees during the Roman period have been documented. The available information regarding the potential adoption of sheep's mobile pastoralism by Iberian societies prior to the Romans' arrival is limited. This study aims to provide fundamental new insights into livestock altitudinal mobility during this period through a biogeochemical approach. Sequential analysis of carbon and oxygen isotope values is combined with strontium isotope ratios from sheep second and third lower molars from four Catalan sites (Mas Castellar de Pontós, Tossal de Baltarga, Sant Esteve d'Olius, Turó de la Rovira). The results reveal evidence of migrations across different altitudinal and geological areas, unveiling the great adaptability of mobile livestock strategies by Iberian populations. The first evidence of descending herds' mobility from the Pyrenees to the lowlands prior to the Roman conquest is also attested. Finally, the effectiveness of multi-isotope analysis (δ18O, δ13C, 87Sr/86Sr) in detecting seasonal livestock movements is demonstrated. Thus, this study provides a comprehensive and nuanced understanding of the complexity of sheep livestock management of the north-eastern Iberian societies during the Middle/Late Iron Age. Moreover, the research points to a more integrated and connected Ibero-Pyrenean world with contemporary lowland communities than so far suggested. However, animal mobility was not widely practised and was possibly determined by the environmental conditions, economic needs, and political decisions of each settlement.

Combining stable isotope ratios with elemental concentrations to improve the estimation of terrestrial carnivore diets

Stable isotopes of animal tissue have been used to estimate diet for many consumer species and places, but the ability to assign contributions to all food items is limited by the number of tracers used, and the separation of the tracer data among the dietary sources. We tested whether we could detect caribou (Rangifer tarandus) in the diet of individual predators in southwest Canada, where caribou are endangered. The separation between caribou tissue and that of other common prey was minimal using C13 and N15 isotope ratios and our confidence in assigning the caribou diet fraction correctly was low despite testing several fractionation values and priors. We measured the concentration of a suite of elements in the tissue of lichen, large prey and predators to investigate whether we could use an elemental concentration as a diet tracer and better assign the caribou diet fraction, because several of these elements were known to be more abundant in lichen, a major food for caribou in winter. Strontium and cesium had higher concentrations, when normalized by a common salt (we chose calcium), in caribou tissue than the other prey species we measured; this was also true for strontium isotope ratios. The elemental tracers appeared to overestimate caribou in the diet however, we suggest that the addition of either cation could yield finer and more accurate estimates of diet for large terrestrial predators after further investigation. The addition of a strontium isotope ratio tracer to a diet investigation may be equally informative and require less pre-work, because one ratio (Sr87/Sr86) has already been well studied.

Analysis of soils, grapes, and wines for Sr isotope characterisation in Diqing Tibetan Autonomous Prefecture (China) and combining multiple elements for wine geographical traceability purposes

Determining the origin and authenticity of wine is a matter of rising interest among consumers and industry standards. The strontium isotopic ratio is regarded as an efficient technique for wine tracing. This study presents an assessment of the Sr isotope value in different matrices, including soil, grapes, and wine. Strontium isotopic maps were built using measured data. Diqing soil isotope ratios ranged between 0.714010 and 0.721999, and grape and wine isotope ratios ranged between 0.710029 and 0.718137, and 0.709508 and 0.718372, respectively. A high correlation was found between the Sr isotope ratios between of grapes and wines (R2 = 0.945), and a weak correlation was found between soil and grapes (R2 = 0.187). In general, the 87Sr/86Sr ratios of Diqing wine have a different range from those of wine from other countries. Compared to carbon isotope values, the oxygen isotope values have a wide diversity in wine from different regions. Elemental fingerprinting, light and heavy isotopes combined with discriminant analysis (DA) and random forest (RF) supported a relatively small wine geographical origin more effectively than the isotopes. This study is the first to focus on the Sr isotopes in different matrices (soil, grapes, and wine) from China and provides a data reference for tracing the provenance of wine.

Образ жизни детей и взрослых варварской округи Херсонеса (по материалам могильников Фронтовое 3 и Киль-Дере 1)

The necropolises Frontovoe 3 and Kil-Dere 1 from the environ of Chersonesos are interesting and important for the reconstruction of the cultural and historical situation on the borders of the Roman Empire. Data on the isotopic composition of bone collagen and tooth enamel provide new opportunities to discuss the nutrition, economy, and mobility of societies. The isotope composition of carbon and nitrogen informs about the average dietary intake of an individual over the last few years of life (7—10), while the ratio of strontium isotopes in tooth enamel characterizes the habitat of the child during the formation of the crown of the teeth (in this case, from 1 to 6 years). Thus, we obtain information about local natives and migrants of the first generation, whose childhood, probably, passed outside the environ of Chersonesos. The isotopic composition of carbon and nitrogen in 67 samples of bone tissue and the composition of strontium in 35 samples of tooth enamel were studied. The life support system of these societies was based on the use of local terrestrial food resources. Few individuals have been found who can be named first-generation migrants. The low variability of the isotope ratios of strontium and carbon indicates a clear localization of this population group on the given territory. We also discuss the factors behind the differences in the isotopic markers of groups from Kil-Dere 1 and Frontovoye 3. These can be both environmental factors and cultural differences. The questions addressed here can be answered by studying a broader base of the compared materials.

Tracing Mobility Patterns of Buried Species of the Late Iron Age Funerary Staggered Turriform of Son Ferrer (Calvià, Spain)

Abstract This is the first mobility 87Sr/86Sr analysis in human remains made on the Balearic Islands. Eight human individuals buried at the same Late Iron Age funerary chamber of Son Ferrer site (Calvià, Mallorca) have been sampled for strontium and oxygen isotopic analysis (87Sr/86Sr and δ 18O). The study includes strontium and oxygen isotopic analysis of domestic mammals buried in the same Funerary Area (FA1) together with present-day vegetation and archaeological bone to assess the strontium isotopic ratios (87Sr/86Sr) around the site. All the results are compatible with the 87Sr/86Sr documented in Mallorca and, more specifically, with the surrounding bedrocks from the site. Humans, caprines, and dogs provided similar results and no significant differences are found between the species. The only exception is a caprine which shows seasonal movement through the period of enamel mineralisation. The isotopic information agrees with the previous studies, which proposed that Son Ferrer site was a symbolic place for the surrounding territory where people from the nearby villages were buried.

Investigating mobility and pastoralism in Kerma-period communities upstream of the fourth cataract, Sudan.

The Kingdom of Kush in today's northern Sudan and southern Egypt (ancient Nubia) is often depicted as a secondary state relative to ancient Egypt. More recent investigations have set aside Egyptocentric and western, colonialist perspectives of state development focused on control of land and agricultural surplus, examining Kushites through the lens of African-based models of mobile pastoralism in which power and authority were achieved through control of herds and alliance-building. Here, analyses of radiogenic strontium isotopes in human dental enamel are used to investigate diachronic shifts in mobility patterns linked to pastoralism and state development during the Kerma period (ca. 2500-1100 BCE). From five cemetery sites around al Qinifab, Sudan, upstream of the capital at Kerma, we analyzed the strontium isotope ratios of 50 teeth from 27 individuals dating from the Early through Late Kerma phases. Individuals from the Early and Middle Kerma phases demonstrated considerable 87 Sr/86 Sr ratio variability (mean = 0.70835 ± 0.00109), with 50% falling outside the locally bioavailable strontium range. Conversely, most Classic (0.70756 ± 0.00043) and Late Kerma (0.70755 ± 0.00036) individuals exhibited ratios consistent with the local region. These changes indicate a potential transformation in subsistence strategies and social organization as early communities engaged in a more mobile lifestyle than later groups, suggesting a greater degree of pastoralism followed by declining mobility with Kushite state coalescence and a shift to agropastoralism. Because 87 Sr/86 Sr ratios from enamel reflect childhood geographic residence, these findings indicate that mobility likely involved extended family groups, and not just transhumant adults.

A needle in a haystack: strontium isotopes (87Sr/86Sr) in otoliths identify origin of largemouth bass from a large Southwest reservoir

Largemouth bass Micropterus salmoides, a popular warm water sport fish, is routinely stocked in reservoirs throughout the USA to augment wild populations. Evaluating if these supplementations are successful requires distinguishing hatchery-sourced fish from their wild counterparts. From 2011 to 2019, over 467 000 largemouth bass fingerlings were stocked from multiple hatchery sources into a large southwestern reservoir (Elephant Butte Reservoir, New Mexico, USA) to supplement the sport fish population. To identify hatchery-sourced largemouth bass, we measured strontium isotope ratios (87Sr/86Sr) and determined ages using otoliths and dorsal spines. Otolith analysis of 169 fish classified 92.9% ( n = 159) to the reservoir with few fish of hatchery origin (2 from Arkansas, 1.2%, and 1 from Montana, 0.6%). While stocking over 467 000 fingerlings across 8 years appears to reflect negligible stocking success, it is likely that low and variable stocking densities (average 3.0, range 0.29–7.77 fish·ha−1) contributed to the low stocking success in Elephant Butte Reservoir. Dorsal fin spines did not yield accurate age reconstructions and their 87Sr/86Sr values were affected by matrix interferences preventing source assignments.

Main reservoir controlling factors and diagenetic evolution of the Xiao'erbulak Formation of Tarim Basin, NW China: A case study of Well KPN1 in Kalpin area

The Cambrian subsalt dolomite in the Kalpin area of the Tarim Basin is an important reserve growth point and strategic replacement area. However, there is a lack of clear understanding regarding the formation mechanism of high-quality reservoirs in this region, which has hindered oil and gas exploration. This study aims to address this knowledge gap by providing a comprehensive description of the rock types and characteristics of the Xiao'erbulak Formation. Microscope observations, geochemical analyses, and interpretations of well logging data from Well KPN1 were used in this analysis. The Xiao'erbulak Formation can be divided into four members, arranged from bottom to top. The relatively high manganese (Mn) content (87–137.7 ppm), oxygen isotope composition (δ18O) with an average value of −6.37‰, and strontium isotope ratio (87Sr/86Sr) with an average value of 0.7109 indicate that dolomitization of the Xiao'erbulak Formation likely occurred during the penecontemporaneous-shallow burial period. The early formation of dolomite contributed to increased reservoir porosity and resistance to compaction during deep burial, which laid the foundation for reservoir formation. The carbon isotope composition (δ13C) of the Xiao 1 and Xiao 2 members exhibit frequent zigzag curves, indicating recurring progression/regression processes. The subsequent development of granular beach facies played a crucial role in reservoir formation in the Xiao 2 Member. Tectonic fractures and penecontemporaneous karstification controlled the reservoir characteristics of the Xiao 3 Member. Furthermore, this study provides an analysis of the diagenetic evolution model of Well KPN1 and examines the impact of diagenetic transformations on reservoir quality. The systematic analysis of downhole data from Well KPN1 serves as a foundational reference for comparative studies with other drilling sites in the area. It also offers valuable guidance for future exploration and deployment strategies in the northwest Tarim Basin.

Interactions between Trypillian farmers and North Pontic forager-pastoralists in Eneolithic central Ukraine.

The establishment of agrarian economy in Eneolithic East Europe is associated with the Pre-Cucuteni-Cucuteni-Trypillia complex (PCCTC). PCCTC farmers interacted with Eneolithic forager-pastoralist groups of the North Pontic steppe as PCCTC extended from the Carpathian foothills to the Dnipro Valley beginning in the late 5th millennium BCE. While the cultural interaction between the two groups is evident through the Cucuteni C pottery style that carries steppe influence, the extent of biological interactions between Trypillian farmers and the steppe remains unclear. Here we report the analysis of artefacts from the late 5th millennium Trypillian settlement at the Kolomiytsiv Yar Tract (KYT) archaeological complex in central Ukraine, focusing on a human bone fragment found in the Trypillian context at KYT. Diet stable isotope ratios obtained from the bone fragment suggest the diet of the KYT individual to be within the range of forager-pastoralists of the North Pontic area. Strontium isotope ratios of the KYT individual are consistent with having originated from contexts of the Serednii Stih (Sredny Stog) culture sites of the Middle Dnipro Valley. Genetic analysis of the KYT individual indicates ancestry derived from a proto-Yamna population such as Serednii Stih. Overall, the KYT archaeological site presents evidence of interactions between Trypillians and Eneolithic Pontic steppe inhabitants of the Serednii Stih horizon and suggests a potential for gene flow between the two groups as early as the beginning of the 4th millennium BCE.

Massive influence of Himalayan source on sedimentation along northern Indian peninsular basin

A 39 m long sediment core (MD161-19) spanning 320 ka, collected from the intermediate water depths of (1480 m) of Mahanadi offshore was subjected to provenance analyses using Sr and Nd isotope systematics. The Sr–Nd isotope ratios of MD161-19 fall on the mixing line defined by Ganga and Brahmaputra main stem averages. Strontium and Nd isotope ratios along with Fe/Al ratio clearly show the predominance of Himalayan sediments in the study area. The significant temporal variations in the Sr–Nd isotope ratios observed for the entire depositional age (320 ka) may be attributed to changes in the relative sediment contribution by Ganga and Brahmaputra river systems draining terrains with contrasting Sr–Nd isotope ratios. The temporal geochemical profiles coupled with precipitation profile show that wet-phases during stadials led to enhanced erosion of the trans-Himalayan batholiths (THB) rocks (characterized by high εNd values) possibly due to glacial expansion in the higher reaches of the Brahmaputra catchment. The warm interstadials coupled with enhanced precipitation are accompanied by a shift towards lower εNd values which may be attributed to extensive erosion of the Ganga catchment area comprising rocks characterized by lower εNd values and diminished THB contribution due to lack of glacial influence.

A craton-wide geochemical study of Neoarchaean carbonate rocks of Zimbabwe

Neoarchaean greenstone belts of the Zimbabwe craton host microbialite-bearing limestone successions that range in age from ~2.82 to 2.68 Ga. The best-preserved successions, according to Raman geothermometry, are situated in the Bulawayo and Belingwe greenstone belts where they have been subjected to lower greenschist facies metamorphism with a peak temperature of ~350 °C. Elsewhere, such as in the Masvingo belt, peak temperatures reached ~540 °C, giving rise to marbles. The carbonate rocks consist mainly of calcite and, to a lesser extent, dolomite and contain variably admixtures of siliciclastic detritus. Samples with the least amount of siliciclastic detritus have shale-normalized rare earth element and Y distribution patterns that indicate open marine conditions, with positive La, Eu, and Gd anomalies, superchondritic Y/Ho ratios, and depleted light rare earth elements relative to the heavy rare earth elements. The δ13СVPDB values are −2.0 to 2.1 ‰, and δ18OVPDB values cluster in the range of −20 to −10 ‰. Strontium isotope ratios vary in concert with siliciclastic detritus. The lowest initial 87Sr/86Sr ratio of 0.70155 is close to the depleted mantle value at the time of deposition, suggesting minimal contribution from evolved felsic crust to the Neoarchean ocean. Only samples from the Masvingo belt show radiogenic Sr isotope ratios (0.70202–0.70340) indicative of an epicratonic setting with exposed felsic basement. For the rest, open marine conditions prevailed in a proto-cratonic setting characterized by mantle-derived greenstone volcanism. Carbonate sedimentation on the Zimbabwe craton thus predate the fundamental rise in the marine 87Sr/86Sr Sr isotope signal in the late Neoarchaean.

Tales from Ginderup Mound in Thisted County, Denmark

The preservation of organic and human remains in Early Nordic Bronze Age mounds (1700 BCE -1100 BCE) permits new provenance work on this important period. Studies have shown that different mobility/non-mobility patterns were exercised by elite women during this time. To extend the database, we conducted strontium isotope analyses of the enamel from the second and third molars from the elite female grave from Ginderup in Thisted County, Denmark. Among other items, this grave included the textile remains of a possible corded skirt or fringed blanket. We complemented analyses of this woman’s enamel with strontium isotope analyses of the first molar from Grave B as well as osteological analysis of the individuals from Early Nordic Bronze Age Graves A, B and C.
 Our results revealed that the strontium isotope ratios obtained from the woman wearing a possible corded skirt yielded one local ratio (M2) and one non-local ratio (M3). The results from Grave B yielded a ratio which falls within the local baseline of present-day Denmark. Our results suggest that the Ginderup Woman was probably of local origin, but that she also was repeatedly mobile during her life. These data are further evidence for the Nordic Bronze Age’s complex socio-dynamics.

The Material Complexity of Three Seventeenth-Century Cabinets Exported from the Far East

ABSTRACT This paper focuses on three Far East cabinets that have ended up in Sweden for various reasons and on various routes. Some specific characteristics have been analysed using various scientific methods: sectional microscopy, wood taxonomy, X–ray fluorescence microscopy, pyrolysis-gas chromatography-mass spectrometry, strontium isotope ratio measurement, and radiocarbon dating. The results show that the cabinets contain wood from species endemic to Japan, namely asunaro (Thujopsis dolabrata) and hinoki (Chamaecyparis obtuse). They are coated with urushi sap derived from Toxicodendron vernicifluum trees, in two cases confirmed to be harvested in China, and one case probably blended with sap exuded from Toxicodendron succedanea harvested in North Vietnam. Their black appearance is due to a soot pigment typical of many products from the early Edo period or older. The data obtained with scientific methods, unavailable in the past, improve knowledge about these cabinets. Such new information should be made available to scholars and the general public.

Strontium isotope analysis of the Xiongnu nobles and their followers in Central Mongolia

As the first provenance study focusing on Xiongnu nobles and their followers, this study analyzed eleven human and four animal remains from the Gol Mod 2 cemetery in western Mongolia for strontium isotope ratios. The results suggest that two of the three nobles had lived in the Khanuy valley for an extended period of time, and one had lived elsewhere but was buried at the same cemetery as were the other nobles. These Xiongnu nobles might have migrated in the grassland, but the Khanuy valley and the Gol Mod 2 site surely played an irreplaceable role for them, providing valuable information for the investigation of the Xiongnu political center. A number of the followers did not grow up locally but were chosen to follow the nobles and lived in or close to the valley during their later lives. Furthermore, strontium isotope values and dietary features together confirmed that the human skeleton in G2T189 belonged to the tomb owner rather than a buried intruder. This study is a reminder that some traditional methods used to determine the local strontium isotopic range for a site are not suitable when the studied human individuals did not live a sedentary lifestyle or their social roles evidently varied.

Strontium isotopes trace the dissolution and precipitation of mineral organic carbon interactions in thawing permafrost

Interactions between minerals and organic carbon (OC) in soils are key to stabilize OC and mitigate greenhouse gas emissions upon permafrost thaw. However, changes in soil water pathways upon permafrost thaw are likely to affect the stability of mineral OC interactions by inducing their dissolution and precipitation. This study aims to assess and quantify how mineral OC interactions are affected by dissolution and precipitation in thawed relative to unthawed layers. We hypothesize that a change in the radiogenic strontium (Sr) isotopic ratio (87Sr/86Sr) involved in mineral OC interactions upon changing water saturation conditions implies a destabilization of the mineral OC interaction. We quantified mineral OC interactions using selective extractions in soils facing gradual thaw (Eight Mile Lake, AK, USA) and in sediments with a thawing history of abrupt thaw (Duvanny Yar, Russia), and we measured the 87Sr/86Sr ratio of the selective extracts targeting the Sr associated to mineral OC interactions. Firstly, for water saturated layers with a higher proportion of mineral OC interactions, we found a difference in the 87Sr/86Sr ratio relative to the surrounding layers, and this supports the preservation of a Sr “stable” pool in these mineral OC interactions. We estimated that a portion of these mineral OC interactions have remained undissociated since their formation (between 4% and 64% by Sr isotope mass balance). Secondly, we found no difference in 87Sr/86Sr ratio between layers accumulating Fe oxides at redox interfaces regularly affected by water table changes (or upon thermokarst processes) relative to surrounding layers. This supports the dominance of a Sr “labile” pool inherited from processes of dissolution and precipitation of the mineral OC interactions. Thirdly, our estimations based on a Sr isotope mass balance support that, as a consequence of permafrost thaw, a larger proportion of Sr from primary mineral weathering (>80%) controls the Sr in mineral OC interactions in the saturated zone of deeply thawed soils relative to poorly thawed soils (∼50%). In conclusion, we found that the radiogenic Sr isotope method, applied for the first time in this context, is promising to trace dissolution-precipitation processes of mineral OC interaction in thawing permafrost.

Abrupt Changes in Atmospheric Circulation During the Medieval Climate Anomaly and Little Ice Age Recorded by Sr‐Nd Isotopes in the Siple Dome Ice Core, Antarctica

AbstractThe Southern Hemisphere westerly winds (SWW) play a critical role in global climate, yet their behavior on decadal to centennial timescales, and the mechanisms driving these changes during the preindustrial era, remain poorly understood. We present a decadally resolved record of dust compositions using strontium and neodymium isotope ratios in mineral dust from the Siple Dome ice core, Antarctica, to explore the potential that abrupt changes in SWW behavior occurred over the past millennium. The record spans portions of the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) intervals as defined in the Northern Hemisphere. We find evidence of an abrupt strengthening of atmospheric circulation during the MCA at ∼1125 CE (825 BP) that persisted for about 60 yr, indicating increased influence of Patagonia‐sourced dust. This occurs during an extended positive phase of Southern Annular Mode (SAM+)‐like conditions, characterized by high SWW velocities and a southerly shift of the main wind belt toward ∼60°S, suggesting that rapid changes in SWW strength could occur under the present SAM+ pattern. A second 20 yr long shift in dust compositions during the LIA at ∼1748 CE (200 BP) is coincident with higher dust delivery to Siple Dome, and may indicate increased dust emissions related to glacier activity in Patagonia. The new Siple Dome ice core data set demonstrates that Sr‐Nd isotopes can be used to trace shifts in atmospheric circulation on decadal timescales.