Stable Isotope Studies Research Articles

Camelid husbandry in the Atacama Desert? A stable isotope study of camelid bone collagen and textiles from the Lluta and Camarones Valleys, northern Chile.

Management of camelids in the coastal valleys of the Andes has generated much debate in recent years. Zooarchaeological and isotopic studies have demonstrated that in the coastal valleys of northern and southern Peru there were locally maintained camelid herds. Because of the hyperarid conditions of the northern coast of Chile, this region has been assumed to be unsuitable for the raising of camelids. In this study we report stable carbon and nitrogen isotopic compositions of camelid bone collagen and textiles made from camelid fiber from Late Intermediate Period (LIP) and Late Horizon (LH) occupations in northern Chilean river valleys. The camelid bone collagen isotopic compositions are consistent with these animals originating in the highlands, although there is a significant difference in the camelids dating to the LIP and LH, possibly because of changes made to distribution and exchange networks by the Inca in the LH. There were no differences between the isotopic compositions of the camelid fibers sampled from textiles in the LIP and LH, suggesting that either the production of camelid fiber was unchanged by the Inca or the changes that were made do not present visible isotopic evidence. Several camelid fiber samples from both the LIP and LH present very high δ13C and δ15N values, comparable to human hair samples from one site (Huancarane) in the Camarones Valley. These data suggest that people in the northern valleys of Chile may have kept small numbers of animals specifically for fiber production. Overall, however, the vast majority of the textile samples have isotopic compositions that are consistent with an origin in the highlands. These data suggest that the hyperarid coastal river valleys of northern Chile did not support substantial camelid herds as has been interpreted for northern Peru.

Reconstructing diets and subsistence strategies of the Bronze Age humans from the Central Plains of China: A stable isotopic study on the Nanwa site

AbstractA multicrop agricultural system, including millet, wheat, rice, and soybeans, first emerged in China in the Late Longhang period and is considered to be one of the most important basic foundations underpinning the origin and development of early states in China. However, there is still a lack of studies on the specific subsistence strategies of humans from the Bronze Age, specifically addressing how widespread the multicrop agricultural system was. To explore these questions above, carbon and nitrogen isotope analysis on human bones from the Nanwa site (ca 1720–256 BC & 960–1279 AD) was undertaken to investigate the palaeodiet and subsistence strategies of the Nanwa humans. This paper also reviews the existing stable isotope data of Bronze Age humans on the Central Plains of China.The Nanwa humans from the Erlitou and Yinxu periods have a mean δ13C value of −9.4 ± 0.7‰ and −9.1 ± 0.9‰, suggesting a predominantly C4 diet, probably derived from millet agriculture or domesticated animals fed on millet. Nanwa humans of the Eastern Zhou Dynasty have a relatively low mean δ13C value of −10.5 ± 2.4‰, indicating a consumption of much more C3 foods, likely derived from rice, wheat, soybean, or animals that fed on those plants. A temporal stable isotopic comparison from the Erlitou period to the Eastern Zhou Dynasty on the Central Plains of China shows the majority of the Bronze Age humans have high mean δ13C value (−9.5 ± 1.8‰), suggesting a predominantly C4‐based diet. We infer that millet agriculture was still the primary economy for humans during the Bronze Age. However, there is a relatively large proportion of humans from the Eastern Zhou Dynasty that have decreased δ13C values, indicating a much more C3 foods consumption and diversity diet, presumably derived from a multicrop agricultural system of millet, wheat, rice, and soybean. It is possible that the trend moved from a narrowly focused, mainly millet‐based diet, to a more diverse agricultural system and was triggered by a combination of factors such as climate change, agricultural reform, social stratification, wars, migration, and so on.

Comparing the assimilation of dietary nitrogen supplied by animal-, plant- and microbial-derived ingredients in Pacific white shrimp Litopenaeus vannamei: A stable isotope study

In order to become a more profitable and sustainable industry, the aquaculture sector is constantly exploring alternative nutrient sources. In the present study, the natural stable isotope signatures of different animal-, plant- and microbial-derived ingredients were determined to evaluate the assimilation of dietary nitrogen in Pacific white shrimp. Experimental diets were manufactured to replace fish meal and squid meal with microbial- and plant- derived ingredients (48 and 66 % dietary inclusion) and were also used as additives (4%). Ingredients were also used as additives to study their effects on growth performance and assimilation. Corn gluten, soy protein isolate, Arthrospira (Spirulina) biomass and a bacterial meal (ProFloc™) were used to formulate six, isotopic control diets containing one source of dietary nitrogen, while six combined diets had varying proportions of ingredients. At the end of the trial, survival rates were similar among treatments (88 ± 9%) but there were significant differences in mean final weight. Microbial and animal proteins promoted similar final weight when combined (1080−1537 mg), while plant ingredients and Arthrospira caused lower growth when used alone (420−970 mg). Isotopic values indicated significant differences in the assimilation proportions of dietary nitrogen, mainly attributed to the ingredients’ different amino acid profiles. The dietary nitrogen contained in microbial-derived ingredients was assimilated at similar, or even higher proportions than fish meal and squid meal. Diet formulated with 33 % fish meal, Arthrospira and corn gluten, contributed 31, 36 and 33 % of dietary nitrogen to muscle growth, respectively. The second 33 % combination supplied 42, 34 and 24 % from squid meal, bacterial meal and soy protein. When ingredients were used at 4%, additive levels, they also contributed structural nitrogen to shrimp muscle tissue despite low dietary inclusions. Results demonstrated the viable use of stable isotopes to evaluate the assimilation of dietary nitrogen supplied by emerging alternative ingredients.

An ideal solution? Optimising pretreatment methods for artificially mummified ancient Egyptian tissues.

RationaleAlthough the analysis of skeletal remains dominates the study of ancient dietary stable isotopes, mummified bodies also allow short‐term diet to be studied through the analysis of soft tissues. The application of resins, waxes and oils during mummification can affect the results obtained. This study assesses a range of methods for removing such substances from mummified tissue.MethodsAn experimental mummification model following ancient Egyptian methods was created using a modern pig leg. Sub‐samples of skin, muscle and bone were removed and coated with a range of substances used in Egyptian mummification. Four methods were used to clean these samples before the measurement of the carbon and nitrogen stable isotope ratios of their gelatinised collagen content using a ThermoFinnigan Flash Elemental analyser coupled to a DeltaPlus XL isotope ratio mass spectrometer via a ConFlo III interface.ResultsThe results showed that embalming materials can significantly affect dietary stable isotope ratios, and that these substances are most effectively removed using a mixture of polar and non‐polar solvents. Results indicate that bone samples demineralised with HCl and skin samples produce more accurate results than bone samples demineralised with EDTA or muscle samples.ConclusionsThe choice of tissue and the preparation methods used can have a significant effect on the accuracy of stable isotope data obtained from mummified tissue, particularly when embalming materials are also present. A mixture of solvents appears to be a more effective cleaning agent than a single solvent. Demineralisation with HCl is preferable for well‐preserved bone, as used in this study, but whether this is the case for more fragile, less well‐preserved bone requires further study. Skin samples produce more consistent data than muscle, but visually distinguishing between these tissues is not simple on ancient mummies.

Tectono-metamorphic evolution of an evaporitic décollement as recorded by mineral and fluid geochemistry: The “Nappe des Gypses” (Western Alps) case study

Evaporites play a major role on the structuration of collisional orogens especially when they act as décollement units. However, their exact pressure-temperature-deformation (P-T-d) paths are poorly documented. In this study, the first direct P-T-d constraints of the “Nappe des Gypses” formation (western French Alps) have been established. An innovative association of structural geology, petrography, crystallochemistry, and detailed study of both fluid inclusions and stable isotopes (C, O) analysis has been applied to this evaporitic facies. Geochemical analysis shows that the “Nappe des Gypses” formation has recorded the three typical metamorphic and deformational events of the Alps (namely D1, D2 and D3). These different constraints allow the determination of the first P-T path determination for this unit. Metamorphic peak conditions of the “Nappe des Gypses” are at 16.6 ± 2.3 kbar and 431 °C ± 28 °C. This formation was buried at similar conditions than the oceanic units. During the exhumation path, the D1-D2 transition is reached at 350 °C ± 20 °C and 6.5 ± 1.8 kbar and the D2-D3 transition is assumed to be at 259 °C ± 24 °C and 2.0 ± 1.0 kbar (Strzerzynski et al., 2012). Peak P-T conditions overlap those of the median Liguro-Piemontese units but are different from those of the Briançonnais units. It implies 1) an active and crucial role of the “Nappe des Gypses” during the exhumation of the Alpine oceanic complex, and 2) confirms the allochthonous and more distal origin of the European Tethyan passive margin of the “Nappe des Gypses” formation. Consideration of sulfates dehydration probably between 15.0 and 16.6 kbar and 200 and 300 °C, allows to discuss pore pressure excess and its mechanical consequences on the exhumation process. This process is very likely to amplify the “décollement” effect of the evaporites and allow the nappe stack formation.This illustrates the role of this formation as a décollement surface. This difference of evolution highlights the major role of the evaporitic formations on the exhumation and structuration of a collisional chain. Such methodology could contribute to decipher the role of evaporites in the structural context of other collisional chains such as Himalaya, Pyrenees or Zagros.

A conceptual model for water resources circulation patterns in Andarokh-Kardeh region (NE, Iran)

Andarokh-Kardeh region is located northeast of Iran and provides notable part of potable water of Mashhad, the second most populated city of Iran with over 3 million inhabitants. Stable isotopes (18O, 2H and 13C), hydrodynamic, and hydrochemical indicators have been applied to evaluate water resources quality comprehensively and to present a hydrogeological conceptual model for the Andarokh-Kardeh region. Hydrochemical studies indicate that chemical rock weathering and ion exchange are the main factors controlling the quality of water in the region, while atmospheric (precipitation) as well as anthropogenic sources have no notable effect. Stable isotopes (18O and 2H) studies in surface and groundwater samples demonstrate enriched values in Kardeh Dam Reservoir (KDR) due to evaporation and also demonstrate that the interaction between KDR and downstream groundwater resources is negligible. The δ13C isotope and DIC and DOC concentrations indicate role of carbonate mineral dissolution from Mozdooran Formation, atmospheric and soil CO2 and also the domination of C3 vegetation coverage in the study region. The developed conceptual model for Andarokh-Kardeh demonstrates different hydrogeological conditions during wet and dry periods, and highlights the main process which affect hydrogeology of the region. Water quality studies and the developed conceptual model demonstrate the main factors controlling water quality and the main hydrogeological characteristic of Andarokh-Kardeh region which can be used by water resources scientists for the future water management programmes.

Stable isotope and fluid inclusion studies of early Zn-Cu-(Ni-Co)-rich ores, lower ore zone of Brushy Creek mine, Viburnum Trend MVT district, Missouri, U.S.A.: Products of multiple sulfur sources and metal-specific fluids

Mississippi Valley-type (MVT) deposits of the Viburnum Trend are typically lead-dominant and occur in the upper portion of the Cambrian Bonneterre Dolomite. Unusual zinc- and copper-rich ores, with notable enrichments in Ni, Co, and Ag, have been discovered within the lower Bonneterre Dolomite, >30 m below the district’s main ore-bearing horizon. These ores appear to be localized along fault/fracture zones within the Lamotte Sandstone, which promoted extreme dissolution of the base of the overlying Bonneterre Dolomite and resulted in pronounced vertical zoning of early Ni-Co, Cu, Zn and Pb ores above the sandstone/dolomite contact.Stable isotope and fluid inclusion studies were undertaken to assess whether the deep ores resulted from a single fluid reservoir that evolved from Cu-Ni-Co-rich to Zn-rich to Pb-rich or are instead products of distinct fluids unrelated to the stratigraphically higher, main Pb-rich ores of the district. Sphalerite-hosted fluid inclusions from the lower orebody appear to be geochemically distinct from those that formed the upper orebodies. They record the highest K/Na and Mg/Na ratios in the southeast Missouri MVT district, suggesting dominance of siliceous lithologies (arkose and/or felsic igneous rocks) over limestones along their ore-fluid pathways. Paragenetic trends indicate that distinct fluid compositions are associated with specific generations of sphalerite, which likely reflects the presence of multiple fluids.The δ34S values of ore minerals (early pyrite and chalcopyrite, −7 to +5‰; early sphalerite, +6 to +15‰; main sphalerite, +7 to +17‰ V-CDT) indicate deposition from fluids that utilized isotopically distinct sulfide reservoirs. Low-δ34S sulfur sources for early ores likely included sulfide in local brines within the Lamotte Sandstone and diagenetic sulfide minerals within the basal units of the Bonneterre Dolomite. A trend of increasing δ34S values of ore sulfides (from −5 toward +17‰) with vertical distance above the Lamotte Sandstone-Bonneterre Dolomite contact indicates that as the deep ore fluid system worked its way upward, it breached less permeable units in the lower Bonneterre Dolomite, allowing incorporation of high-δ34S sulfide from brines present higher in the stratigraphic section. A concomitant up-section pattern of decreasing δ18O values of dolomite cement and recrystallized remnant host rock (from −3 toward −9‰ V-PDB) is also consistent with a localized, deep mineralizing fluid system, which interacted progressively with the stratigraphically higher, regional-scale, Pb-rich fluid system.The episodic nature of metal sulfide deposition in the lower ore zone points to a system in which fluid mixing would have been highly variable, both temporally and spatially. Reaction path models require mixing of multiple, ore metal-specific and sulfide-bearing fluids in order to form the orebody. The sequence and concentrations of metal sulfides are inconsistent with ore formation from a single, evolving metal-bearing fluid.This study indicates that faults localized early metal- and sulfide-bearing fluids, facilitating mixing of fluids that resulted in the accumulation of high-grade ores near the Bonneterre Dolomite-Lamotte Sandstone contact. Recognition of fault/fracture patterns beneath more typical Pb-rich orebodies in the Viburnum Trend may be a viable exploration strategy for similar Zn-Cu-Co-Ni-rich deposits.

Particle size matters: The effect of particle size on carbon and oxygen isotope composition of bone hydroxyapatite.

Stable isotope studies often focus on hydroxyapatite (bioapatite) to answer questions of paleodiet, paleomobility, and paeloenvironment. This study seeks to determine the effect that sample particle size (in particular SA:V, or surface area to volume ratios) has on measured carbon and oxygen stable isotope values (δ13 C and δ18 O) in bone hydroxyapatite. Previously ground Homo sapiens sapiens cortical bone samples were subdivided using geological screens to obtain three separate sub-samples, differing only in their particle size. These aliquots (n = 60) were then treated using established protocols to remove any exogenous organic material (2.5% NaOH) and adsorbed carbonates (0.1 M CH3 COOH), and analyzed for δ13 C and δ18 O using a Kiel-IV Carbonate Device coupled to a Thermo-Finnigan DeltaPlus IRMS. Data obtained indicate that decreased particle size leads to increases in both δ13 C and δ18 O, with oxygen isotope values being more dramatically affected. Specifically, it is possible to produce isotopic shifts of as much as 1.0‰ and 4.0‰ for δ13 C and δ18 O, respectively, solely by analyzing different sized particles from the same individual, bone, and sample. Based upon the variability seen between different size fractions from the same sample, it is clear that particle size has a meaningful impact on carbon and oxygen isotope composition. We attribute these shifts to the differential adsorption or precipitation of environmental carbon and oxygen during pretreatment. We recommend that particle size be added to the list of potential variables affecting isotope composition, alongside other factors including diagenesis, reagent concentration, and treatment time. We would also note that while most individuals exhibit consistent changes, some do not, and thus further investigation into these phenomena is warranted.

Bonebed amber as a new source of paleontological data: The case of the Pipestone Creek deposit (Upper Cretaceous), Alberta, Canada

Amber deposits and dinosaur bonebeds provide some of the most detailed sources of information on terrestrial ecosystems, but these sources have rarely been studied in tandem. The Pipestone Creek bonebed from the Campanian Wapiti Formation of Alberta, Canada, provides an opportunity to explore both data sources in the same deposit for the first time. The site has yielded an exceptional fauna dominated by abundant remains of the centrosaurine ceratopsian Pachyrhinosaurus. The initial campaigns of excavation in the 1980s led to the collateral discovery of amber, and the site became the first published source of insect-bearing amber in a dinosaur bonebed. Here we describe amber inclusions in detail and analyze the composition and geochemistry of the amber (FTIR spectroscopy and stable isotope studies) in order to draw paleoecological and paleoenvironmental inferences. We describe a feather fragment from an aquatic bird, as well as new species of Psocodea and Hymenoptera (Mymarommatidae) with ecological constraints. Indeterminate aphid and spider inclusions were also found, but preservation was not sufficient for formal description. FTIR spectroscopy suggests a botanical source among the Cupressaceae, while stable isotope data indicate that the resin-producing forest did not receive precipitation directly from the Western Interior Seaway. These initial results show that amber is a valuable source of additional information about the habitat surrounding the vertebrates found in bonebed deposits. Given the abundance and range of inclusions encountered so far, Pipestone Creek amber also appears to be a promising new source for a relatively diverse Campanian amber assemblage.

Geochemical study of stable carbon and oxygen isotopes in landfilled Ca-rich oil shale ash

Geochemical study of stable carbon and oxygen isotopes in landfilled Ca-rich oil shale ash

The origin and chemical composition of Carpathians chloride CO2-rich waters in the light of stable chlorine isotope studies (37Cl and 35Cl)

Investigations into chloride CO 2 -rich water occurring in the Polish and Slovakian Carpathians were carried out to gain a better understanding of the Cl – sources. The primary Cl – concentration in sea water, processes accompanying diagenesis, together with water-rock-gas interactions, have undoubtedly influenced the present content of chlorides. The Cl – - concentrations in the waters analysed vary from 35.5 to 4148.3 mg/l, lower than in sea water, with a mean ~19000 mg/l. The measured δ 37 Cl values range from –1.15 to –0.26‰, below the typical sea water value of 0‰. It might be concluded that the chemical and isotopic composition of these waters are the result of reactions during diagenesis (e.g., ion exchange or diffusion through low-permeability clay layers) as well as meteoric water influx.

The reconstruction of the mechanisms of problematic authigenic carbonates formation in diagenetic and catagenetic environments associated with the generation/oxidation of hydrocarbons

Authigenic carbonates are crystallized in subaquatic and subaerial settings at various stages of sedimentary rock formation, and are often found in both ancient and modern deposits. The explanation of their genesis may be problematic. However, in most cases the study of stable isotopes makes it possible to reconstruct the authigenic carbonates crystallization mechanism. The fact of the frequent genetic association of authigenic carbonates with hydrocarbons determines the importance of the development of methods for the reliable identification of their genesis.

Functional differences in trophic structure of offshore wind farm communities: A stable isotope study

The proliferation of offshore wind energy installations causes a local change in biodiversity because these structures become heavily colonised by large quantities of fouling fauna, attract large mobile crustaceans and fish, and alter the macrofaunal communities in the soft sediments surrounding the wind turbines. Here, we analysed the stable isotope signals (δ13C and δ15N) of the faunal communities associated with a wind turbine, its scour protection layer (SPL) and the surrounding soft sediments. We hypothesised that structural differences in community composition would be reflected in food web complexity and that resource partitioning could be one of the mechanisms contributing to the co-existence of such dense communities. Sampling was conducted at a gravity-based foundation in the Belgian part of the North Sea, where both sessile and mobile organisms were collected along the depth gradient of the turbine, the SPL and the surrounding soft substrate. The results indicated that the structural differences of the communities are reflected in the food web complexity as indicated by the trophic niche size, the trophic diversity and the redundancy of the communities along the depth gradient. Higher food web complexity was associated with zones where high accumulation of organic matter occurs (soft substrate and SPL). Low food web complexity was observed in depth zones that are dominated by sessile suspension-feeding organisms (intertidal and Mytilus zone). The high trophic diversity and low redundancy observed within the trophic clusters of the soft substrate and the Metridium zone indicated that resource partitioning can be a mechanism allowing the co-existence of large densities of a wide variety of species.

Stable isotopes (H, O, S) signatures evidencing evolutionary trends of Brazilian spas groundwaters

This paper reports a stable isotope (H, O, S) study of groundwater samples (25) in 10 spas from southeast Brazil. They are cold (25 °C, 36%), hypothermal (25–33 °C, 60%) and mesothermal (33–36 °C, 4%) waters; and are predominantly composed of bicarbonate, carbonate and sodium. Dissolved sulfate is the dominant anion in one water sample and its concentration increased with increase in pH, electrical conductivity (EC) and total dissolved solids (TDS) values in the samples. 2H and 18O data reported in the literature for circa 700 rainwater samples collected in São Paulo State and Brasília airport, Brazil, were used to construct the following regional meteoric waterline (RMWL): δ2H V-SMOW (‰) = 8.06 δ18Owater V-SMOW (‰) + 12.85. The HO isotopes of the studied groundwater samples show a δ18Owater variation of −14.1 to −5.3‰ V-SMOW, whereas the δ2H range was −66.5 to −31.7‰ V-SMOW, which was plotted on or near the RMWL, suggesting a meteoric origin for them. However, one hypothermal water sample (29 °C) plotted away from this RMWL, and is from a deep fractured aquifer which mainly occurs in fenitization aureole rocks surrounding the carbonatite complex at Araxá spa, Minas Gerais State, and a magmatic hydrothermal water may contribute to this water sample. The use of both δ34Ssulfate and δ18Osulfate values in the selected sites permitted the plotting of a mixture line of the dissolved sulfate in the different aquifer systems of this study, considering two major sources as endmembers: sulfide oxidation, SOX (δ34Ssulfate = +1‰ and δ18Osulfate = +1‰) and sulfates possessing δ34Ssulfate = +9‰ and δ18Osulfate = +21‰ (OSW). This is an unusual isotopic composition opposite from that of sea water. The δ34Ssulfate and δ18Osulfate values tend to increase with increase in dissolved sulfate concentration. The OS isotopes signatures that deviated from the general mixture line could be due to several processes, including atmospheric deposition, SO2 oxidation in the atmosphere, soil-derived sulfate, sulfide oxidation, evaporites dissolution and the presence of dissimilatory sulfate-reducing bacteria. Three sulfate isotope composition of spring waters from Águas da Prata spa in the Poços de Caldas alkaline massif (PCAM) represented endmember sources that defined a triangle around the remaining PCAM samples, as well as the samples from the crystalline basement, São Francisco craton, and Alto Paranaíba igneous province (APIP). Such triangle allows for estimation of the relative isotopic contribution in the different spas groundwaters, which is a new approach that focuses on the use of δ34Ssulfate-δ18Osulfate pair in environmental studies, and shows its usefulness in addition to other conventional hydrogeochemical fingerprints.

Geology, alteration system, and uranium metallogenic potential of Pasha-Ladoga Basin, Russia

The Mesoproterozoic Pasha-Ladoga Basin is located at the margin of the Karelian Craton and Svecofennian Belt in northwest Russia. It is the only basin in Russia that is currently recognized to host unconformity-type uranium mineralization (e.g., Karku deposit). Mineralization is associated with the Priozersk Formation which comprises a basal sequence of immature arkosic sandstones and conglomerates interpreted as high-energy braided stream channel and channel bar facies within an alluvial fan depositional environment. Diagenetic and hydrothermal alteration of the Priozersk sandstones is similar to that observed in unconformity-related uranium deposits of the Athabasca Basin (Canada) and includes three main stages: (1) an early diagenetic assemblage comprising illite-smectite (K-rectorite), calcite, minor chlorite, and kaolinite precipitated at 100–150 °C; (2) a peak diagenetic-hydrothermal assemblage composed of kaolinite-dickite, Fe- and Fe-Mg chlorite, calcite, and sulfides formed at 150–250 °C; (3) late diagenetic-hydrothermal event involving fracture-controlled kaolinite and late hematite. Similar to the Athabasca Basin type uranium mineralization, the Karku deposit exhibits anomalous concentrations of LREE, Nb, Pb, and positive correlations between U and Cu, Zn, Ag, and Pb that is a geochemical signature of unconformity-type uranium mineralization. Based on oxygen and hydrogen stable isotope study, it was found that fluids in equilibrium with early and peak diagenetic clays were consistent with oxidized basinal brines and reduced basement fluids. In contrast to the Athabasca Basin, mineralizing fluids at the Karku area were more reduced and potassic. A new geological model for the Karku deposit is proposed based on petrographic observations and sandstones geochemistry. The proposed model envisages the permeable rocks of paleoregolith and the coarse-grained basal part of the Priozersk Formation as the main pathway for migration of uraniferous fluids responsible for the formation of Karku uranium deposit. From the perspective of the geological setting, the Karku deposit differs from deposits of the Athabasca Basin in that it occurs in a rapidly deposited rift-related basin with associated mafic magmatism, the host sandstone sequence is relatively thin (e.g., Priozersk Formation) and exhibits abrupt lateral facies variations, and the widespread presence of early diagenetic interstitial swelling clays. Based on these sedimentological characteristics, it is considered that the Karku deposit setting precludes optimum conditions to create high tonnage high-grade unconformity-type U deposits as found in the Athabasca basin.

Geological, geochronological, pyrite geochemical and stable isotope studies of the Tantou gold deposit in central China

The Tantou Au deposit is a large-scale gold deposit in the Xiong’ershan area. A geochemical study of pyrite was conducted using laser ablation inductively coupled plasma mass spectrometry. Two types of hydrothermal pyrite were identified in the ores and wall rocks, i.e., the fine euhedral pyrite in brecciated ores (Py1) and coarse grains disseminated in the quartz-sulfide veins (Py2). The trace elements of the two pyrite types exhibit different concentrations, associations and rim-core zoning, implying different geneses and crystallization processes. Both pyrites of the two mineralization stages were hydrothermal pyrite. However, the Au, As, Co, Ni, and Zn were more rich in Py1, while Ag, Cu, Mo, Sb, and Pb were favored in Py2. The growth rims of Py1 suggest several pulses of fluid activities. Hydrothermal sulfides from the main ore-forming stage have a Rb-Sr isochron age of 124.2 ± 3.1 Ma, placing the gold mineralization in the Early Cretaceous. The initial 87Sr/86Sr value of the sulfides is 0.71124 ± 0.00010, suggesting an ancient crust source (the Paleoproterozoic Xiong’er Group). In situ S isotope data acquired from the main sulfides suggest that the ore-forming materials underwent isotopic fractionation because of oxidation of the ore-forming fluids during the hydrothermal process. The C-O isotope values of calcite from the postore stage indicate that magmatic fluids were likely the principle sources of carbon and that low temperature alteration has had a significant effect on the levels of CO2 and carbonate ions. Together, these results suggest that the Tantou Au deposit is genetically related to the destruction of the North China Craton as a result of lithospheric thinning during the Early Cretaceous.

Stable Isotope Studies of North American Arctic Populations: A Review

We review the major stable carbon and nitrogen isotope studies conducted on human remains in the North American Arctic (NAA) and discuss the findings with respect to two major research themes: diachronic subsistence, and the development of food cultures across the NAA. The interpretation of stable isotope data from human bone collagen and hair keratin is complicated by issues of equifinality in addition to uncertainty arising from the high fat/high protein diets of Arctic hunter gatherers. We suggest future lines of inquiry which may help to alleviate some of these challenges. Our review of Arctic stable isotope studies shows the ongoing potential of stable isotope analysis of Arctic hunter-gatherers and faunal populations, but we include the caveat that regardless of how cutting-edge or refined the analytical method, future stable isotope studies must be contextualized with other lines of evidence from well-excavated sites, and would profoundly benefit from the incorporation of indigenous perspectives and research priorities.

Variability in polar bear Ursus maritimus stable isotopes in relation to environmental change in the Canadian Beaufort Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 630:215-225 (2019) - DOI: https://doi.org/10.3354/meps13136 Variability in polar bear Ursus maritimus stable isotopes in relation to environmental change in the Canadian Beaufort Sea Nicole Boucher1,*, Andrew E. Derocher1, Evan S. Richardson2 1Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada 2Wildlife Research Division, Science and Technology Branch, Environment and Climate Change Canada, Winnipeg, MB R3C 4W2, Canada *Corresponding author: nboucher@ualberta.ca ABSTRACT: Diets of apex predators can be used to understand the effects of environmental changes within an ecosystem and to monitor shifts in community dynamics. Using stable isotopes of nitrogen and carbon (δ15N and δ13C) in polar bear Ursus maritimus guard hairs, we examined their diet in the Canadian Beaufort Sea from 2003 to 2011. We investigated how δ15N and δ13C were related to population demographics, sea ice dynamics, climate indices, air temperatures, and ringed seal Pusa hispida ovulation rates. Bayesian stable isotope models were used to determine annual variation in prey contributions and niche widths. Diet contributions from ringed seal, bowhead whale Balaena mysticetus, beluga Delphinapterus leucas, and bearded seal Erignathus barbatus varied by sex, reproductive status, and year. Polar bear ringed seal consumption was lowest and niche widths were highest in 2004 following ringed seal reproductive failure in the early 2000s, and polar bear δ15N decreased when ringed seal ovulation rate was high. Polar bear δ15N and δ13C were linked to capture locations, which may reflect geographic gradients in stable isotopes within the Beaufort Sea. Climate indices were not related to polar bear δ15N and δ13C. Sea ice dynamics were related to polar bear δ13C, suggesting that the bears’ diets shift in response to environmental change. Overall, these results highlight the biological link between polar bears and ringed seals, as well as sea ice dynamics, and the importance of considering geographic location in stable isotope studies. KEY WORDS: Ursus maritimus · Polar bear · Beaufort Sea · Sea ice dynamics · Environmental change · Stable isotopes · Diet · Niche width Full text in pdf format Supplementary material PreviousCite this article as: Boucher N, Derocher AE, Richardson ES (2019) Variability in polar bear Ursus maritimus stable isotopes in relation to environmental change in the Canadian Beaufort Sea. Mar Ecol Prog Ser 630:215-225. https://doi.org/10.3354/meps13136 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 630. Online publication date: November 07, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

The Rate of Glucose Appearance Is Related to Postprandial Glucose and Insulin Responses in Adults: A Systematic Review and Meta-analysis of Stable Isotope Studies

It is often assumed that lower postprandial glucose (PPG) and insulin (PPI) responses are induced by slower glucose influx from the gut (e.g., by delayed carbohydrate digestion). However, changes in the rate of appearance of glucose in the peripheral circulation [rate of appearance of exogenous glucose (RaE)] may be accompanied by changes in endogenous glucose production (EGP) and the rate of disappearance of total glucose into tissues (RdT). The quantitative relationships between reductions in RaE and PPG/PPI levels are unclear. The objective was to perform a meta-analysis to quantify the effect of changes in RaE on changes in PPG and PPI levels (primary) and EGP and RdT (secondary). We systematically searched the Scopus, Medline, and Cochrane library databases through 10 January 2019 for randomized, controlled, carbohydrate-rich interventions that aimed to reduce RaE in humans, measured using dual or triple stable isotope methods. The 2-h net incremental AUCs for all variables were extracted or calculated. Relationships between RaE and outcomes were quantified by weighted regression analyses. There were 12 articles, including 17 comparisons, that satisfied the inclusion criteria. The subjects were mainly men (60%), with age and BMI ranges of 18-40 y and 20.0-27.5 kg/m2, respectively. A 10% reduction in RaE was associated with reductions in PPG levels, PPI levels, and the RdT of 7% (95% CI: 2%, 12%; P=0.010), 8% (95% CI: 2%, 13%; P=0.012), and 11% (95% CI: 4%, 17%; P=0.005), respectively, but was not significantly associated with a change in EGP (13%; 95% CI: -7%, 33%; P=0.176). All fluxes together explained 70% and 26% of the variances in PPG and PPI levels, respectively. In adults, reducing glucose RaE by diet is associated with significant reductions in PPG levels, PPI levels, and the rate of glucose disposal. This trial was registered in the PROSPERO database with identifier CRD42018084824.

Histological structure of baleen plates and its relevance to sampling for stable isotope studies

Stable isotope analysis of baleen plates is a widespread technique for studying baleen whales. Typically, subsamples along the growth axis of the baleen plate are extracted and analysed to examine time-related variation in their stable isotope signals. However, baleen plate tissue is composed of two different tissues: a pair of cortex layers flanking an internal medulla. These two histological components exhibit differential development, and their consolidation as a tissue is therefore likely non-synchronic. This could influence stable isotope results because the stable isotope signal may differ in each subsample according to the proportion of the two histological components extracted from the tissue. In this study, stable isotope analysis was combined with optical microscopy examination of fin whale (Balaenoptera physalus) baleen plates to understand the ontogeny of the two histological components. In both of them, the δ15N values followed a sinewave pattern along the growth axis of the baleen plate. However, the δ15N values of the cortex appeared to be advanced compared to those of the medulla. Additionally, the amplitude of the δ15N values in the oscillations was higher in the cortex than in the medulla. The histological examination revealed that these differences are caused by earlier and faster synthesis of the cortex layer compared to that of the medulla. Because the stable isotope ratios of the two layers differ, we propose that in this type of studies only the outer-most part (closest to the surface) of the cortex should be subsampled and analysed. Additionally, to include the most recently formed tissue, this subsampling should start well below the zwischensubstanz, or baleen “gum”.