Soil δ13C and δ15N baselines clarify biogeographic heterogeneity in isotopic discrimination of European badgers (Meles meles)

Isotopic techniques have been used to study phenomena in the geological, environmental, and ecological sciences. For example, isotopic values of multiple elements elucidate the pathways energy and nutrients take in the environment. Isoscapes interpolate isotopic values across a geographical surface and are used to study environmental processes in space and time. Thus, isoscapes can reveal ecological shifts at local scales, and show distribution thresholds in the wider environment at the macro-scale. This study demonstrates a further application of isoscapes, using soil isoscapes of 13C/12C and 15N/14N as an environmental baseline, to understand variation in trophic ecology across a population of Eurasian badgers (Meles meles) at a regional scale. The use of soil isoscapes reduced error, and elevated the statistical signal, where aggregated badger hairs were used, and where individuals were identified using genetic microarray analysis. Stable isotope values were affected by land-use type, elevation, and meteorology. Badgers in lowland habitats had diets richer in protein and were adversely affected by poor weather conditions in all land classes. It is concluded that soil isoscapes are an effective way of reducing confounding biases in macroscale, isotopic studies. The method elucidated variation in the trophic and spatial ecology of economically important taxa at a landscape level. These results have implications for the management of badgers and other carnivores with omnivorous tendencies in heterogeneous landscapes.

The use of paleoclimatic simulations to refine the environmental and chronological context of archaeological/paleontological sites

To reconstruct the paleoenvironmental and chronological context of archaeological/paleontological sites is a key step to understand the evolutionary history of past organisms. Commonly used method to infer paleoenvironments rely on varied proxies such as faunal assemblages and isotopes. However, those proxies often show some inconsistencies. Regarding estimated ages of stratigraphic layers, they can vary depending on the dating method used. In this paper, we tested the potential of paleoclimate simulations to address this issue and contribute to the description of the environmental and chronological context of archaeological/paleontological sites. We produced a set of paleoclimate simulations corresponding to the stratigraphy of a Late-Pleistocene Holocene site, El Harhoura 2 (Morocco), and compared the climatic sequence described by these simulations to environmental inferences made from isotopes and faunal assemblages. Our results showed that in the studied site combined US-ESR ages were much more congruent with paleoenvironmental inferences than OSL ages. In addition, climatic variations were found to be more consistent with isotopic studies than faunal assemblages, allowing us to discuss unresolved discrepancies to date. This study illustrates the strong potential of our approach to refine the paleoenvironmental and chronological context of archaeological and paleontological sites.

Concepts and Revised Models for Phanerozoic Orogenic Gold Deposits

Existing published models for orogenic gold deposits (OGDs) do not adequately describe or explain most deposits of Phanerozoic age, and there are numerous reasons why Phanerozoic OGDs might differ significantly from older deposits. We subdivide Phanerozoic OGDs into four main subtypes, based on a number of descriptive criteria, including tectonic setting, lithological siting, and characteristics of the mineralization in each subtype. The four subtypes are: 1) crustal scale fault associated (CSF) subtype, 2) sediment-hosted orogenic gold (SHOG) subtype, 3) forearc (FA) subtype, and 4) syn- and late tectonic dispersed (SLTD) subtype. Lead isotopic studies suggest that Pb and other metals in all but the FA subtype were likely derived from relatively small source reservoirs in the middle or upper crust. OGDs formed in large, lithologically and structurally homogeneous regions will tend to be of the same subtype; however, in geologically complex orogenic belts it is common to find two or more subtypes that formed at approximately the same time. Based on the synthesis of global OGDs of Phanerozoic age districts containing CSF or SHOG subtype deposits appear to have the best potential for hosting multiple large deposits. FA subtype deposits form in a relatively uncommon tectonic setting (accretionary forearc, possibly overlying a subducting spreading ridge) and are likely to be rare. SLTD subtype OGDs are the most common, but most are small and uneconomic, although they commonly generate substantial alluvial gold deposits.

Isotopic and hydrogeochemical characterization of groundwater and surface water from a mine site in Tanzania

This study used the hydrochemical properties of water to reveal the causes of water quality degradation. The results showed that most samples located downstream of the mine tailings dam were slightly acidic with pH as low as 4.6. Samples with high levels of Na+, Cl−, and could not be isotopically linked to the local geochemistry, but the anthropogenic activities and evaporation were probably responsible for the observed water chemistry. The Piper diagram indicated cations were dominate by Ca and Mg, while anions were dominated by bicarbonates and sulphates. Pb and Hg levels (mean 70.29 and 17.95 μg/L, respectively) were all higher than the World Health Organization (WHO) and Tanzanian drinking water guidelines. Mining activities probably contributed to the observed low pH values and elevated concentration of cyanides, heavy metals, and metalloids. Stable isotope results indicated a vulnerability of the water to recent contamination that could be attributed to anthropogenic activities. Moreover, isotopic studies indicated a flow pattern from the eastern to the western side of the mine study site. Lowland samples were more 3H-enriched than highland ones. The present study concludes that groundwater recharge from recent local precipitation may have an impact on the sources studied.

Theory and Calculation of Nontraditional Stable Isotope Fractionation

This paper conducts processing on isotope anharmonic effect with molecular dynamics method and Monte Carlo method based on path integration. It introduces the theoretical calculation method of pressure effect, and finally the nuclear volume effect and its theoretical calculation method, stressing that the nuclear volume effect is an important part of isotopic studies of heavy metals in the future. This paper makes an analysis on the equilibrium fractionation theory based on simple harmonic approximation.

Ultrasonic Shaking of Glauconite Pellets with Diverse Reagents for a Comparison of Their K–Ar with Already Published Rb–Sr Results

A combined ultrasonic treatment, with de-ionized H2O, dilute HAc or dilute HCl, of three Mid-Miocene glauconite samples was applied to K–Ar date the different separates in order to compare the results with those obtained by the Rb–Sr method using the same three samples and that were analyzed strictly in the same way. Two aliquots yield opposite elemental and K–Ar trends, which suggests different initial mineral compositions for the various pellets. The K–Ar data of two untreated and leached L7 and L8 aliquots are almost within analytical uncertainty from 17.3 ± 0.6 Ma to 19.6 ± 0.7 Ma (2σ), while those of the third L10 sample are slightly higher at 22.1 ± 1.2 Ma (2σ). Comparatively, the earlier published Rb–Sr ages of the three untreated samples and of the leached aliquots gave similar data for the L7 aliquots by an isochron at 18.1 ± 3.1 (2σ) Ma and for the sample L8 by an isochron with an age of 19.6 ± 1.8 (2σ) Ma, while the untreated L10 aliquot yields a very high Rb–Sr date of 42.1 ± 1.6 (2σ) Ma. This untreated L10 glauconite fraction contains blödite, a Sr-rich carbonate that impacted the two isotopic systems differently. Generally, dilute HCl or HAc acids dissolve carbonates, sulfates, sulfites and oxides, while they do not affect the clay-type crystals such as glauconites. These soluble minerals can be identified indirectly, as here, by X-ray diffraction and the amounts of leached Na2O, CaO and Fe2O3 contents. Together with the leaching of some metallic trace elements, those of NaO confirm the leaching of metals and of blödite that are both hosted by the glauconite pellets. The occurrence of this Sr-enriched mineral explains the age differences of the non-treated aliquots and suggests a systematic leaching of any glauconite separate before isotope determination and, possibly, a comparison of the Rb–Sr and K–Ar results. Ultrasonic shaking appears appropriate for physical disaggregation of any contaminating grains that may remain hosted within the pellets, even after a preliminary H2O wash, which may dissolve and remove the soluble minerals but not the H2O-insoluble silicates. The K–Ar study completed here as a complement to a previous Rb–Sr study highlights, again, the importance of the preparation step in isotopic studies of glauconite-type and, by extension, of any clay material, as all occurring minerals can interfere in the final age determinations and, therefore, differently in the mineral assemblages. All those not in isotopic equilibrium need to be removed before analysis, including the soluble Sr or alkali-enriched ones.