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Rubinite (IMA 2016-110) is a recently discovered Ti3+-dominant refractory mineral in the garnet group from the solar nebula. It has the Ia 3 d garnet-type structure with a = 12.19(1) Å, Z = 8, and an end-member formula of C a 3 T i 2 3 + S i 3 O 12. Rubinite was identified as micrometer-sized crystals in five refractory Ca, Al-rich inclusions (CAIs) from the CV3 carbonaceous chondrites Allende, Efremovka, and Vigarano. In the Vigarano CAI V3, it occurs in the central portion of an ultra-refractory fragment with Zr, Y, Sc-oxide, spinel, and davisite-diopside, all enclosed within an amoeboid olivine aggregate. In the Allende Compact Type A (CTA) CAI AE01-01, it occurs with gehlenitic melilite, perovskite, spinel, hibonite, davisite, grossmanite, and diopside. In Efremovka, rubinite occurs within gehlenitic melilite with perovskite, spinel, and grossmanite in three CTA CAIs E101, E105, and 40E-1 (in a compound CAI). Rubinite is present in spinel-poor regions in all four of the Efremovka and Allende CAIs, but it is in contact with spinel in the Vigarano inclusion. The mean chemical composition of type rubinite in Allende is (in wt%) CaO32.68, Ti2O3 14.79, TiO2 13.06, SiO2 28.37 Al2O3 3.82, Sc2O3 1.80, Na2O 1.01, ZrO2, 0.80, MgO 0.79, V2O3 0.61, FeO 0.53, Y2O3 0.07, Cr2O3 0.05, total 98.38, giving rise to an empirical formula of (Ca2.94Na0.08) T i 1.04 3 + T i 0.59 4 + S c 0.13 M g 0.10 V 0.04 F e 0.04 Z r 0.03 S i 2.38 A l 0.38 T i 0.24 4 + O 12 , where Ti3+ and Ti4+ are partitioned based on stoichiometry. Efremovka rubinite has a similar composition with a mean empirical formula of C a 2.97 N a 0.06 T i 1.05 3 + T i 0.66 4 + M g 0.12 S c 0.09 Z r 0.03 V 0.03 Y 0.01 F e 0.01 S i 2.36 A l 0.48 T i 0.16 4 + O 12. Vigarano rubinite is much more Y-, Sc-, and Zr-rich, having an empirical formula of (Ca1.89Y0.83Mg0.28) T i 0.59 3 + S c 0.50 Z r 0.72 M g 0.2 V 0.02 C r 0.01 S i 1.64 A l 1.18 T i 0.07 4 + F e 0.06 O 12. All rubinites are Ti3+-rich, but a significant amount (11–46%) of the Ti is 4+. In the Efremovka CTAs, spinel is 16O-rich (Δ17O∼−24‰); rubinite and perovskite show limited ranges of Δ17O (from−24 to −16‰; most analyses range from −24 to −20‰); melilite and grossmanite are the most 16O-depleted minerals (Δ17Orange from∼−10 to−4‰and from−8 to−5‰, respectively). In the Allende CTA AE01-01, spinel and hibonite are 16O-rich (Δ17O∼−24‰); melilite, rubinite, and perovskite show large ranges in Δ17O (from −23 to −3‰, from −21 to −6‰, and from −14 to −2‰, respectively); grossmanite is uniformly 16O-depleted (Δ17O ∼−3‰). Rubinite formed under highly reducing conditions in the solar nebula by gas-solid condensation and crystallization from a Ca-, Al-, and Ti-rich melt. Subsequently, most rubinite grains in the Allende CAI and some in the Efremovka CAIs may have experienced O-isotope exchange to various degrees with an 16O-depleted (Δ17O∼−2‰) aqueous fluid on the CV chondrite parent asteroid. However, crystallization from a Ca, Al, Ti-rich melt that recorded O-isotope exchange with nebular gas with variable Δ17O or post-crystallization O-isotope with such gas cannot be excluded. The mineral name is in honor of Alan E. Rubin (b. 1953), a cosmochemist at the University of California, Los Angeles (UCLA), U.S.A., for his many contributions to research in cosmochemistry and mineralogy of meteorites. [ABSTRACT FROM AUTHOR]

Rationale: The stable isotope compositions of atmospheric CO2 can provide useful insight into various geochemical processes and carbon cycles on Earth, which is critical for understanding of Earth's changing climate. Here, we present a simple and cost‐effective analytical method for the collection and measurement of carbon and oxygen isotope compositions of atmospheric CO2. Methods: Air samples of ~150 mL were collected individually or collectively using our simple active air collection system and then extracted on a vacuum purification line to remove noncondensable gases and atmospheric water vapor. The efficiency of removing atmospheric water vapor was tested by using a magnesium perchlorate desiccant trap and a dry ice/ethanol trap. Lastly, a "J‐Cut tube sealing/cracking method" was developed to store and transfer purified atmospheric CO2 to the GasBench II and CF‐IRMS system for δ13C and δ18O measurements. Results: The collective active air collection method combined with the full sample air extraction method for a 3‐min transfer time or "Full 3m TE" yields the best analytical precision of 0.07‰ (δ13C) and 0.04‰ (δ18O). Removing atmospheric water vapor from air samples is not necessary for δ13C, but essential for δ18O measurements. The J‐Cut tube sealing/cracking method shows a near 100% effectiveness for the storage and transfer of atmospheric or any CO2. Conclusions: A simple and cost‐effect method was developed for the collection, purification, storage, and isotopic analysis of indoor/outdoor atmospheric CO2 samples for general users. This method utilizes a popular headspace gas sample preparation system for CF‐IRMS and an easy‐to‐build vacuum purification line without involving complex and high‐cost devices for the preparation of atmospheric CO2. [ABSTRACT FROM AUTHOR]

Rationale: Vein calcite in Devils Hole has been precipitating continuously in oxygen‐isotope equilibrium at a constant temperature for over 500 000 years, providing an unmatched δ18O paleoclimate time series. A substantial issue is that coeval calcite (based on matching δ18O values) has uranium‐series ages differing by 12 000 years. Methods: An unparalleled high‐accuracy δ18O chronology series from continuously submerged calcite was used to correct the published uranium‐series ages of non‐continuously formed calcite in two cores, cyclically exposed by water‐table decline during glacial–interglacial transitions. This method relies on the premise that the δ18O values of coevally precipitated calcite are identical, allowing matching calcite δ18O values to establish formation ages. Results: Exposed calcite can have apparent ages that are 12 000 years too young due to unrecognized uranium mobility and resulting mixed ages identified in over 50 mixed uranium‐series ages from previous studies. Secondary uranium in fluids, sourced from the formation or dissolution of porous carbonate deposits (folia) with high uranium‐238 (238U) concentrations, has migrated up to 10 mm into vein calcite. Conclusions: The continuously submerged Devils Hole δ18O chronology is not explained by orbital forcing. Rather, this chronology represents a regional climate record in the southern Great Basin of sea‐surface‐temperature (SST) variations off California, variations that preceded the last and penultimate deglaciations by 5000 to approximately 10 000 years. Temporal discrepancies between the continuously submerged Devils Hole chronology and other regional δ18O records (e.g., the Leviathan chronology) can be explained by unrecognized cryptic, pernicious uranium mobility, leading to model estimations that may be thousands of years younger than actual ages. Consequently, paleo‐moisture availability, water‐table, and groundwater recharge models based on these mixed uranium‐series ages are too young by as much as 12 000 years. The potential for post‐formation uranium addition in subaerial cores and speleothems underscores the need for caution in uranium‐series dating, highlighting δ18O time‐series comparisons as a method for identifying mixed ages. [ABSTRACT FROM AUTHOR]

Megacrysts in kimberlite are large (>1 cm) mineral grains that crystallized from sub-lithospheric proto-kimberlite melts in the lower sub-continental lithospheric mantle (SCLM), often after complex melt-SCLM interactions. Understanding the development of the proto-kimberlite melt system is important for two primary reasons: 1) a control on the melt diversification and range in Mg# observed in kimberlites that erupt at the surface and 2) it is associated with diamond-destruction in the deep lithosphere. We present δ18O values for a well-characterized suite of megacrysts from the Monastery kimberlite, South Africa, to evaluate variations in melt δ18O, the effect of melt-SCLM interactions on the primary δ18O of mantle-derived magmas, and further constrain the development of the proto-kimberlite melt system in the deep lithosphere. The δ18O values of the megacrysts from the early-crystallising assemblages of Fe-poor (Mg# 83–88) olivine and relatively primitive (Group 1) ilmenite are: δ18O Fe-poor ol = 5.43 to 5.84 ‰ ( x ¯ = 5.23 ‰, σ = 0.10, n = 10); δ18O Grp 1 ilm = 3.88 to 4.35 ‰ ( x ¯ = 4.10 ‰, σ = 0.15, n = 8). The calculated δ18O value of melts in equilibrium with these megacrysts (5.4–5.8 ‰), indicates that they are typical of mantle-derived melts (i.e., 5.7 ± 0.2 ‰; Eiler, 2001). Garnet, clinopyroxene, and orthopyroxene have δ18O of: δ18O gt = 5.12 and 5.25 ‰ (n = 2); δ18O cpx = 4.72 and 5.02 ‰ (n = 2); δ18O opx = 5.20 and 5.55 ‰ (n = 2). The calculated melts in equilibrium with these phases range from 4.9 to 5.4 ‰, which overlaps those calculated for Fe-poor olivine and Group 1 ilmenite but extend to slightly lower δ18O. The δ18O values of the megacrysts from later crystallising assemblages of Fe-rich olivine (Mg# 78–83), moderately evolved (Group 2) ilmenite, phlogopite, and zircon have δ18O values are: δ18O Fe-rich ol = 4.53–4.94 ‰ ( x ¯ = 4.75 ‰, σ = 0.15, n = 5); δ18O Grp 2 ilm = 2.74–4.46 ‰ ( x ¯ = 3.56 ‰, σ = 0.45, n = 11); δ18O phlog = 4.25–5.73 ‰ ( x ¯ = 5.08 ‰, σ = 0.48, n = 8); and δ18O zir = 4.87–5.09 ‰ ( x ¯ = 4.98 ‰, σ = 0.08, n = 6). These phases have calculated equilibrium melts (3.8–5.6 ‰) predominantly below the typical mantle range. The δ18O values of the Group 3 ilmenites, representing the last stage of crystallisation, have δ18O Grp 3 ilm = 2.93–4.05 ‰ ( x ¯ = 3.59 ‰, σ = 0.36, n = 7). Based on the most primitive megacrysts (Fe-poor olivine and Group 1 ilmenite), we show that the Monastery proto-kimberlite melt had a mantle-like δ18O value of 5.61 ± 0.15 ‰ upon entering the SCLM. The magma then experienced several stages of evolution in the deep lithosphere. The lower-than-normal mantle δ18O values of melts in equilibrium with, the more evolved megacrysts, Fe-rich olivines, Group 2 ilmenites, phlogopites, and zircons can be explained by the assimilation of low-δ18O eclogitic material. An increased Cr# during evolution, marked by the Group 2 ilmenites, suggests additional assimilation of a Cr-rich peridotitic component. We present a three-step model for the Monastery proto-kimberlite involving fractional crystallisation along with complex open-system processes involving melt-SCLM interactions and show that the δ18O value of primary mantle-derived magmas can be significantly modified during ascent through the lithospheric mantle. Furthermore, assimilation of an eclogitic component in the deep lithosphere may contribute to the Fe-enrichment observed in megacryst-rich kimberlites globally. [ABSTRACT FROM AUTHOR]

Abundant granitic plutons intruded the eastern Meguma terrane of Nova Scotia in the middle- to late Devonian. Less voluminous diorite–tonalite and gabbro intrusions are associated with the granitic plutons along the northern margin of the terrane adjacent to the Cobequid–Chedabucto fault zone. All plutons contain metasedimentary xenoliths, and the mafic plutons show magma mingling textures with their adjacent granitic plutons. New U–Pb zircon data from autocrystic zircon in 13 samples indicate coeval emplacement of mafic and granitic plutons between ca. 382 and 368 Ma. However, the zircon grains contain numerous inherited domains that range in age from Palaeoproterozoic to Devonian. These inherited ages correspond to detrital zircon U–Pb dates from the Cambrian to Ordovician metasedimentary host rocks. Zircon oxygen isotopic data (δ18O) are between +7.4 ± 0.2‰ and +9.3 ± 0.3‰ indicating significant involvement of the crust as the magma source or contaminant. If the high δ18Ozrn values are a result of contamination, the contaminant was likely the metasedimentary rocks of the Meguma terrane. Hafnium isotopic data from autocrystic zircon have εHf(t) between −6.0 ± 1.5 and +2.1 ± 2.5. The new zircon U–Pb, O, and Hf isotopic data from plutons in the eastern Meguma terrane are indistinguishable from published data from the South Mountain Batholith. The data suggest that Devonian magmatism in the Meguma terrane post-dated the main orogenic event that caused folding and regional metamorphism and involved the same magma source and/or contaminants throughout the terrane. [ABSTRACT FROM AUTHOR]

AMS radiocarbon ages of organic matter from ice wedges and enclosing peat were determined for the polygonal peatland at the Lorino site on the eastern coast of the Chukchi Peninsula. The study's goal was to fill a knowledge gap about the dynamics of polygonal peatlands with ice wedges and winter climate conditions during the Holocene in this easternmost region of the Russian Arctic. It has been found that peatland accumulated during the Younger Dryas and early Holocene, mostly between 14 and 9.9 cal ka BP, while ice wedges were dated from 7.7 to 6.6 cal ka BP. Since ice wedges have features of syngenetic growth, the discrepancy in the age of ice wedges and enclosing peatland may result from the significant presence of early and pre-Holocene peat. It is assumed that the older polygonal peatland deeply thawed during the Holocene optimum, and subsequently, when the permafrost aggraded, a new generation of ice wedges was formed. The AMS 14C age (18.1 cal ka BP) of the ice wedge exposed below the peat indicates the presence of a Late Pleistocene generation of ice wedges at the study site. Paleotemperature reconstructions based on the stable isotope composition of ice wedges show that the mean January air temperature during the Northgrippian stage of the Holocene varied from –27 to –23°C, and at the end of the Late Pleistocene, from –32 to –26°C. [ABSTRACT FROM AUTHOR]

Sulphur and oxygen stable isotopes of sulphate have been used to trace the sources of sulphur into aquatic systems. These isotopes have also been used to understand the transformation and fate of sulphur in the water bodies contaminated by AMD discharge from active and/or abandoned mines. Stable isotopes of oxygen in dissolved sulphate (δ18OSO4) and water (δ18OH2O) have helped to decipher the sulphide oxidation pathways and estimate their contributions. The present study is focused on analysing the composition of sulphur and oxygen stable isotopes of sulphate and oxygen stable isotope in AMD and Lunar-Lukha River water flowing through the coal mining area of the East Jaintia Hills District, Meghalaya, in order to decipher the sulphide oxidation pathways. The results showed that the sulphur stable isotope of sulphate (δ34SSO4) ranged between –12.5 and –8.0 ‰ (VCDT). The oxygen isotope of sulphate (δ18OSO4) ranged between 1.4 and 2.0 ‰ (VSMOW). The oxygen isotope of water (δ18OH2O) was distributed between –6.2 and –4.2 ‰ (VSMOW). Pyrite oxidation was found to be the dominant source of sulphate in the Lunar-Lukha Rivers. The results of the stoichiometric isotope balance model showed that 68–83 % of sulphate derived Fe3+ oxidation pathway, with a high portion of sulphate oxygen derived from water. The sulphite–water oxygen exchange model revealed the release of intermediate sulphoxyanions, suggesting the presence of an oxidation pathway of sulphide minerals to sulphate via sulphoxyanions. The results from this study will be helpful in defining effective remediation strategies to mitigate AMD impacts. [ABSTRACT FROM AUTHOR]

Megalithism has been repetitively tied to specialised herding economies in Iberia, particularly in the mountainous areas of the Basque Country. Legaire Sur, in the uplands of Álava region, is a recently excavated passage tomb (megalithic monument) that held a minimum number of 25 individuals. This study analysed the carbon, nitrogen, oxygen, and strontium isotope ratios of 18 individuals, in a multi-tissue sampling study (successional tooth enamel sampling, incremental dentine sampling, and bulk bone collagen sampling). The results provide a high-resolution reconstruction of individual mobility, weaning, and dietary lifeways of those inhumed at the site. Oxygen and strontium isotope analysis suggest all individuals come from a similar, likely local, geological region, aside from one biological female who presents a notably different geographical birthplace, weaning, and dietary life history than the rest of the burial population. Comparisons to other nearby megalithic sites (∼35km as the crow flies), located in a valley area, reveal that, whilst sharing the same mortuary practices, these individuals held notably different lifeways. They highlight notably earlier ages of cessation of nursing (≤2 years at Legaire Sur vs. ≥4 years in other megalithic tombs), and a greater dependence on pastoralism than previously observed in lowland megalithic graves. The results from Legaire Sur reveal the complexity of the Late Neolithic-Chalcolithic transition in north-central Iberia, categorising yet another separate socio-economic group with distinctive lifeways inhabiting the region. [ABSTRACT FROM AUTHOR]

Rationale: Micrometeorites are extraterrestrial particles smaller than ~2 mm in diameter, most of which melted during atmospheric entry and crystallised or quenched to form 'cosmic spherules'. Their parentage among meteorite groups can be inferred from triple‐oxygen isotope compositions, for example, by secondary ion mass spectrometry (SIMS). This method uses sample efficiently, preserving spherules for other investigations. While SIMS precisions are improving steadily, application requires assumptions about instrumental mass fractionation, which is controlled by sample chemistry and mineralogy (matrix effects). Methods: We have developed a generic SIMS method using sensitive high‐mass resolution ion micro probe‐stable isotope (SHRIMP‐SI) that can be applied to finely crystalline igneous textures as in cosmic spherules. We correct for oxygen isotope matrix effects using the bulk chemistry of samples obtained by laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) and model bulk chemical compositions as three‐component mixtures of olivine, basaltic glass and Fe‐oxide (magnetite), finding a unique matrix correction for each target. Results: Our first results for cosmic spherules from East Antarctica compare favourably with established micrometeorite groups defined by precise and accurate but consumptive bulk oxygen isotope methods. The Fe‐oxide content of each spherule is the main control on magnitude of oxygen isotope ratio bias, with effects on δ18O up to ~6‰. Our main peak in compositions closely coincides with so‐called 'Group 1' objects identified by consumptive methods. Conclusions: The magnitude of SIMS matrix effects we find is similar to the previous intraspherule variations, which are now the limiting factor in understanding their compositions. The matrix effect for each spherule should be assessed quantitatively and individually, especially addressing Fe‐oxide content. We expect micrometeorite triple‐oxygen isotope compositions obtained by SIMS to converge on the main clusters (Groups 1 to 4) after correction firstly for magnetite content and secondarily for other phases (e.g., basaltic glass) in each target. [ABSTRACT FROM AUTHOR]

Understanding of the diversity and petrogenesis of achondrites is critical for deciphering magmatic processes and the early evolution of planets and asteroids. Here, we report the detailed petrologic, mineralogical, geochemical, and chronological features of the unbrecciated Vestan meteorite Northwest Africa (NWA) 8326. We found that NWA 8326 is composed of coarse-grained orthopyroxene (∼74 vol%), plagioclase (∼19 vol%), fine-grained augite (∼5 vol%), and many accessory minerals such as chromite, ilmenite, Fe-sulfide, silica phases, K-feldspar, Ca-phosphate phases, zircon, baddeleyite, rutile, and primary Si,Al,K-rich glass, differing from typical howardite-eucrite-diogenite meteorites. Based on textural feature and compositional calculation of pyroxene, we suggest that the coarse-grained orthopyroxene was inverted from primary pigeonite and NWA 8326 should be classified as a pigeonite cumulate eucrite. The oxygen and chromium isotope data (Δ17O = − 0.254 ± 0.009 ‰; ε54Cr = − 0.60 ± 0.06) support this classification. A few zircon aggregates are observed in NWA 8326 and the grains therein show a core-mantle zoned texture in cathodoluminescence (CL) images, with the cores being dark and Al-rich while the mantles being bright and Al-poor. We interpret that the CL-dark cores are xenocrystic zircon grains derived from eucrites, whose presence indicates that NWA 8326 should have formed through partial melting of the Vestan mantle, with assimilation of eucritic material. The presence of xenocrystic zircon and primary Si,Al,K-rich glass and the large compositional variation of plagioclase indicate that NWA 8326 is an unequilibrated cumulate eucrite and hence the zircon 207Pb/206Pb age of 4559.2 ± 5.2 (2σ) Ma represents the crystallization of NWA 8326. Reconciling the cumulative texture with the presence of the chemically evolved glass, NWA 8326 would be excavated during the late stage of its crystallization and escaped the prevalent crustal thermal metamorphism of the eucrite parent body. The Mg isotopic composition of NWA 8326 is higher than most diogenites, which suggests that the parent magma of such a pigeonite cumulate eucrite was derived from a source region with heavier magnesium isotopic composition (μ25Mg: −90 to − 96 ppm). [ABSTRACT FROM AUTHOR]

In this study, hydrogeochemistry and environmentally stable isotopes were employed to examine the processes involved in recharging aquifer systems and the changes in the groundwater chemistry caused by the interaction between the water and the aquifer matrix. Based on data derived from 113 groundwater wells, various tools and techniques, including stable environmental isotopes Oxygen-18 and Deuterium (δ18O and δD) for 33 samples and geochemical modeling with NETPATH, were used to evaluate the recharge mechanism and the evolution of the groundwater, combining GIS with hydrological and hydrochemical methods. The results revealed that groundwater from the Quaternary was the main source for irrigation; the water quality was categorized as relatively fresh to saline, with the total dissolved solids (TDSs) ranging from 261.3 to 8628.56 mg/L, exhibiting an average value of 2311.68 mg/L. The results of the environmental isotope analysis showed that the range of oxygen δ18O isotopes in the groundwater was from −5.65‰ to +0.39‰, while the range of hydrogen δD isotopes was from −32.60‰ to 4.73‰. Moreover, the δ18O–δD relationship indicated that the groundwater samples fell around the global meteoric precipitation line, showing a strong relationship, with a coefficient (R2) of approximately 0.82. The NETPATH model revealed that the dissolved chemical species within the groundwater system primarily originated from processes such as mineral weathering and dissolution, ion exchange, and evaporation. [ABSTRACT FROM AUTHOR]

ABSTRACT Industrial shale oil/gas flow have been discovered in the Luanping Basin, and the hydrocarbon potential of the Lower Cretaceous Xiguayuan Formation (Luanping Basin, North China) has attracted the attention of geologists in recent years. The paleoenvironmental conditions, provenance and chert origin of the Xiguayuan Formation were studied using the geochemistry of lacustrine sediments in the Caoying section. A pronounced positive correlation between the oxygen and carbon isotopes of autogenous carbonates indicates the Early Cretaceous Luanping paleolake was an alternating depositional environment of open and closed, with obvious evaporation. The V/(V + Ni) ratios, negative Ce and Eu anomalies suggest that the Xiguayuan Formation was deposited in anoxic conditions with fewer instances of euxinic conditions. Sr/Ba, Z and S values together demonstrate a brackish to saline waterbody under semi‐arid and fluctuating semi‐humid paleoclimatic conditions. Various indicators show that they are predominantly derived from felsic igneous rocks and minor probable basic source supply with minor sedimentary recycling. The cherts are developed in Unit 1 and Unit 2, compared with Unit 3, Unit 1 and Unit 2 show relatively open, less reductive, high salinity. A theoretical formation model of alternating rise and drop in lake levels in the basin was established to show syndepositional bedded chert‐bearing sedimentary succession. The acid river dominate water and the evaporation in front fan delta environment maybe the main factor that lead silica precipitation. [ABSTRACT FROM AUTHOR]

The oxygen isotopic microanalysis of calcite is essential for obtaining high spatial resolution data linked to microstructures, a challenge for conventional techniques. This analysis, however, relies heavily on matrix-matched reference materials, of which only a few calcite standards are available. In this study, an inorganically precipitated calcite vein sample (WS-1) was evaluated through 225 SIMS oxygen isotope analyses and was found to have a homogeneous isotopic composition, with an external reproducibility ≤0.21‰ (1σ), suggesting its potential as a SIMS reference material. The precise δ18OVPDB value, determined via traditional gas-source IRMS, was −16.52 ± 0.13‰ (1SD). Matrix effects were assessed using various carbonates, including abiotic aragonite (VS001/1-A), three abiotic calcites (NBS18, Cal-1, WS-1), and a high-Mg calcite (gorgonian coral). The results revealed negligible matrix effects between abiotic aragonite and calcites but significant differences between calcites and high-Mg calcite, likely due to Mg content or differences in biogenic crystal morphology and trace organic composition. This study demonstrates the utility of in situ oxygen isotopic microanalysis for calcite but emphasizes the need for caution when analyzing high-Mg calcitic skeletons. [ABSTRACT FROM AUTHOR]

Pogo is identified as a deep-seated, intrusion-related gold deposit. Carbonate minerals have a close spatial relationship to hydrothermal gold mineralization in all of its principal ore zones. The carbon and oxygen isotopic ratios of carbonate minerals (siderite, ankerite, and calcite) present within the deposit illustrate the isotopic evolution of the ore-forming fluid. The initial hydrothermal fluid phase is interpreted to be magmatic in origin. The fluid evolution was characterized by a gradual decrease in δ18O and a slight increase in δ13C with decreasing temperature. The dominant carbon-bearing species was CO2, with methane introduced sporadically. Siderite is associated with early-stage mineralization and occurs with ankerite in main-stage ore assemblages. Calcite is recognized in the later stages of mineralization. Gold in the Pogo deposit occurs as native gold, Au-Bi-Te minerals, inclusions in sulfide minerals, or as "invisible gold". The latter is found in pyrite, chalcopyrite, arsenopyrite, and quartz, based on ion microprobe analysis. The presence of invisible gold in these minerals has significant metallurgical implications for gold processing at the Pogo mine. [ABSTRACT FROM AUTHOR]

Fossiliferous carbonate concretions are commonly found in sediments deposited in the Late Cretaceous Western Interior Seaway. Although concretions are diagenetic features, well-preserved fossils from within them have been instrumental in reconstructing the temperature and d18O value of Western Interior Seaway seawater, which is essential for accurate reconstruction of Late Cretaceous climate. Here, we constrain formation conditions of Late Campanian and early Maastrichtian carbonate concretions by combining triple oxygen isotope measurements with carbonate clumped isotope paleothermometry on different carbonate phases within the concretions. We measured both fossil skeletal aragonite and sparry calcite infill from cracks and within macrofossil voids to evaluate differences between "primary" and "altered" geochemical signals. Based on the two temperature-sensitive isotope systems of the primary fossil shell aragonite, the temperature of the Western Interior Seaway was between 20 °C and 40 °C and was likely thermally stratified during the Campanian. The reconstructed d18Oseawater values of ~-1‰ for Campanian Western Interior Seaway waters are similar to those expected for the open ocean during greenhouse climates, while the Maastrichtian Western Interior Seaway may have been more restricted, with a d18Oseawater value of ~2‰, which reflects more evaporative conditions. We reconstructed the diagenetic history of the sparry infill and altered fossils using a fluid-rock mixing model. Alteration temperature, alteration fluid d18O value, and the initial formation temperature were calculated by applying the fluid-rock mixing model to a particle swarm optimization algorithm. We found a different range of initial formation temperatures between the Campanian (25-38 °C) and Maastrichtian (9-28 °C). We also found that alteration in the presence of light meteoric fluids (d18O ≈ -10‰) is required to explain both the sparry infill and the altered fossil isotopic values. Based on our results, both lithification and alteration of the carbonates occurred soon after burial, and light meteoric fluids support prior findings that high-topographic relief existed on the western margin of the Western Interior Seaway during the Late Cretaceous. As one of the first studies to apply these techniques in concert and across multiple mineralogical phases within samples, our results provide important constraints on paleoenvironmental conditions in an enigmatic ocean system and will improve interpretations of the overall health of ecosystems leading into the end-Cretaceous mass extinction. [ABSTRACT FROM AUTHOR]

Late Devonian aquatic environments hosted the fin-to-limb transition in vertebrates. Upper Devonian (ca. 365-360 Ma) strata in Pennsylvania, USA, preserve a diversity of fishes and tetrapods in coastal marine to fluvial depositional environments, making this region ideal for investigating the ecology and evolution of Late Devonian vertebrates. A key unresolved issue has been reconstructing the specific aquatic habitats that hosted various vertebrates during this period. Specifically, the salinity of environments spanning fresh to shallow marine water is difficult to discern from sedimentological and paleontological analyses alone. Here, we analyze rare earth elements and yttrium (REY) as well as stable oxygen and sulfur isotope compositions (d18O, d34S) in fossil vertebrate bioapatite from late Famennian (ca. 362-360 Ma) strata of the Catskill and Lock Haven formations in the Appalachian Basin, USA, to determine the relative salinity of their aquatic environments. These results confirm the ecological euryhalinity of several taxa (Bothriolepis sp., tristichopterids, and Holoptychius sp.). Our results are the first demonstrating that some early tetrapod species occupied unequivocally freshwater habitats by late Famennian time (ca. 362-360 Ma). Our study shows that integrating sedimentological and paleontological data with combined oxygen and sulfur isotope analysis allows precise tracing of the relative salinity of vertebrate habitats deep in the past. [ABSTRACT FROM AUTHOR]

Spatio-temporal isotopic variations and the driving forces in precipitation were explored in Eurasian continent. The results showed that δ18O, d-excess and δ2H-δ18O regressions all presented pronounced spatial heterogeneities among different climate zones, with the distance to sea and the latitude identified as main geographic controls. The Mann-Kendall test revealed that significant temperature increases were observed at the majority (18/20) of the sites. However, δ18O did not universally exhibit the same upward trend (5/20 sites) as temperature although significant positive δ18O-temperature correlations existed at most (18/20) sites. The combined effects of multiple environmental factors complicated the interpretation of isotopic signals. [ABSTRACT FROM AUTHOR]

The Yangtze River as the largest river in Asia, plays a crucial role in understanding the primary driving factors behind river terrace formation, predicting the evolutionary trends of Yangtze River Basin, and ensuring the survival and development of the surrounding populations. 660 chronological data of river terraces in Yangtze River Basin were systematically collected and organized, a river terrace age database was established, and an age probability density function was constructed, and the formation mechanisms of river terraces in the region were explored. The results show that over the past 200 ka, the probability density curve of river terrace ages in the upper and middle Yangtze River Basin exhibits clear peaks at ～11 ka, ～23 ka, ～40 ka, ～44.8 ka, and ～56.25 ka, which correlate strongly with periods of global warming, significant shifts in paleoprecipitation of Loess Plateau, and changes in cave oxygen isotope values, the frequency of river terrace development is higher in the mountainous areas of the upper Yangtze River Basin; the age peaks of the river terrace probability density curve in the middle and upper Yangtze River Basin primarily coincide with global climate abrupt events, the formation of river terraces is more widespread in regions and periods of intense tectonic uplift; river terraces in Yangtze River Basin are formed under the combined influence of tectonic activity and climate change; climate's abrupt changes act as short-term trigger mechanisms, destabilizing river channels and driving incision that leads to terrace formation, while regional tectonic uplift provides the necessary space for river incision, thereby enhancing the sensitivity of river terraces to climate fluctuations; this, in turn, facilitates the formation of river terraces, with a notably higher frequency of terrace formation during relatively warmer climatic periods. [ABSTRACT FROM AUTHOR]

This article presents the results of oxygen stable isotope analysis on eastern oyster (Crassostrea virginica) samples (n = 25) from a Mission-Era (ca. AD 1565–1680) site, Pueblo Santa Catalina de Guale, on St. Catherines Island, GA. Stable isotope analysis was used to assess the seasonality of oyster harvesting on St. Catherines Island during the Mission Era to better understand how Spanish colonization and the Catholic mission system may have impacted Guale foodways. Five eastern oyster left valves were sampled from each known neighborhood of Pueblo Santa Catalina de Guale. Existing data regarding the seasonality of pre-colonial mollusk collection on St. Catherines Island and elsewhere in the coastal Southeast are discussed in conversation with the results of this analysis. This work indicates that Guale residents of St. Catherines Island during the Mission Era were harvesting oysters most intensely during cooler months. This pattern is consistent with estimates of pre-colonial shellfishing seasonality across the region and may even represent a modest increase in the seasonal constriction of shellfishing when compared to data from the preceding period. Salinity estimates based on the isotope data also suggest Guale people during the Mission Era were collecting from a comparatively narrower range of estuarine habitats. We argue that these subtle shifts are a consequence of the reorganization of Guale labor associated with missionization. [ABSTRACT FROM AUTHOR]

The tectonic evolution of the Palaeocene–Eocene Tethys Himalayan foreland basin plays a crucial role in reshaping the collisional orogenic process of the Yarlung–Tsangpo oceanic basin. However, studies examining the sedimentary response during the tectonic evolution of the foreland basin are lacking. In this study, through a detailed field investigation and analysis of Palaeocene–Eocene strata in the Tingri area, we clarified the evolution of the Tethys Himalayan tectonic regions and its sedimentary response. Carbon and oxygen isotopes, geochemistry and detrital zircon U–Pb dating demonstrated that the lower Palaeocene Jidula Formation and upper Palaeocene–lower Eocene Zongpu Formation were deposited in a coastal–shallow marine environment, with the detritus sourced from the northern Indian passive margin. The upper Eocene Pengqu Formation was deposited in a deltaic environment, with its detritus sourced from the Gangdese arc and the Yarlung–Tsangpo suture zone at the active continental margin. Combined with the nearshore subaqueous fan branch channel of the Jidula Formation and the slump deformation of the Zongpu Formation, the Palaeocene–Early Eocene southern Tethys Himalaya in the Tingri area was located in the forebulge of the peripheral foreland basin. The marine–continental interactive delta of the Pengqu Formation and its provenance from the Gangdese magmatic arc indicate that the Tingri area was situated in the foredeep of the peripheral foreland basin during the Late Eocene. The study provides valuable insights into the collisional orogenic processes between the Indian and Eurasian plates. [ABSTRACT FROM AUTHOR]

• Oxidative dissolution pathway of stibnite was studied by sulfate oxygen and sulfur isotope compositions. • The relative percentage of water-derived oxygen incorporation into sulfate increase from 5 % to 52 % with longer reaction duration. • A conceptual model of stibnite oxidative dissolution pathway under the aerobic abiotic conditions was proposed. The environmental threat posed by stibnite is an important geoenvironmental issue of current concern. To better understand stibnite oxidation pathways, aerobic abiotic batch experiments were conducted in aqueous solution with varying δ18O H2O value at initial neutral pH for different lengths of time (15-300 days). The sulfate oxygen and sulfur isotope compositions as well as concentrations of sulfur and antimony species were determined. The sulfur isotope fractionation factor (Δ34S SO4-stibnite) values decreased from 0.8‰ to -2.1‰ during the first 90 days, and increased to 2.6‰ at the 180 days, indicating the dominated intermediate sulfur species such as S 2 O 3 2−, S0, and H 2 S (g) involved in Sb 2 S 3 oxidation processes. The incorporation of O into sulfate derived from O 2 (∼100%) indicated that the dissociated O 2 was only directly adsorbed on the stibnite-S sites in the initial stage (0-90 days). The proportion of O incorporation into sulfate from water (27%-52%) increased in the late stage (90-300 days), which suggested the oxidation mechanism changed to hydroxyl attack on stibnite-S sites promoted by nearby adsorbed O 2 on stibnite-Sb sites. The exchange of oxygen between sulfite and water may also contributed to the increase of water derived O into SO 4 2−. The new insight of stibnite oxidation pathway contributes to the understanding of sulfide oxidation mechanism and helps to interpret field data. [ABSTRACT FROM AUTHOR]

Stable isotope ratios of nitrate (NO3−) can be used as a tool to investigate NO3− dynamics in watersheds over the world. However, most of the NO3− source analyses from watersheds using isotopes have been conducted during baseflow conditions, and more information is required on conditions during rainfall, which is a crucial period for nitrogen export to downstream ecosystems. Additionally, there is limited information regarding the sources of stable isotopes of NO3− in watersheds of Japan. We measured the nitrogen and oxygen isotopes of NO3− (δ15N–NO3− and δ18O–NO3−) in the Yasu River during baseflow and rainfall events and those from major NO3− sources in the watershed. The δ15N–NO3− exported from forests and rice paddies showed small fluctuations, while there were large fluctuations in the δ15N–NO3− exported from sewage treatment plants, suggesting the need to obtain data on δ15N–NO3− exported from sewage treatment plants. The NO3− concentrations in the Yasu River during summer baseflow were too low to be explained by the mixing of NO3− sources within the watershed, suggesting that NO3− consumption processes within the river and groundwater influence the NO3− concentrations. Furthermore, the sources of NO3− exported from the watershed differed during baseflow and rainfall, with a larger contribution of forest-derived NO3− during rainfall. Monitoring during rainfall is therefore essential to determine the sources of NO3− exported from the watershed. [ABSTRACT FROM AUTHOR]

Ocean-island basalts display a relatively large range in their oxygen isotopic composition (δ18O) compared to mid-ocean ridge basalts (MORB). The origin of these variations in δ18O—due to a combination of crustal contamination and/or mantle heterogeneity—is controversial. Kamaʻehuakanaloa (formerly Lōʻihi Seamount) is an active submarine Hawaiian pre-shield volcano that is last known to have erupted in 1996. Basalts from Kamaʻehu (for short) are derived from a distinctive 3He-rich deep mantle source within the Hawaiian plume, yet they commonly experience at least two types of shallow crustal contamination based on enrichments in seawater-derived Cl and 234U. Here, we present oxygen isotopic analyses of volcanic glasses (n  = 102 from 53 samples) and single olivine crystals (n  = 47 from eight samples) for tholeiitic (n  = 28), transitional (n  = 4), and alkalic (n  = 18) basalts, and three hawaiites from Kamaʻehu. The average δ18O values of both glass and olivine from the North Rift Zone and NE summit platform (~5.6‰ and 5.1‰, respectively) are higher (at >95% confidence) than those from the South Rift Zone and the SW summit platform (~5.3‰ and 4.9‰). The glass alkalic index (AI<0 is the switch from alkalic to tholeiitic lavas as the degree of mantle melting increases) and incompatible element enrichment (K2O/TiO2) increases with decreasing MgO and CaO/Al2O3. The northern Kamaʻehu glasses are more frequently alkalic (~68%), more enriched, and more differentiated than those from southern Kamaʻehu (~81% tholeiitic or transitional). Model eruption ages from 226Ra–230Th disequilibria suggest that the transition from alkalic to tholeiitic volcanism at Kamaʻehu was nearly complete by ~2 ka. The predominantly alkalic northern lavas likely record an earlier phase of the volcano's eruptive history that has since been covered by the more recent eruptions of tholeiitic basalts to the south. These observations suggest that melt flux from the mantle (recorded by the AI values and K2O/TiO2 ratios) regulates the crustal processing and δ18O variations of Kamaʻehu magmas. The mantle-controlled transition from alkalic to tholeiitic volcanism at Kamaʻehu led to the more frequent supply of larger magma batches produced by higher degrees of mantle melting, establishment of an active shallow hydrothermal system for high-temperature alteration of the volcanic edifice, and a decreasing extent of clinopyroxene fractionation. The average δ18O values of glass (~5.4‰) and olivine (~5.0‰) from Kamaʻehu—similar to the most depleted MORB—represent the best estimate for mantle-derived magma at this volcano. The higher average δ18O values of the glass and olivine from northern Kamaʻehu result from assimilation of volcanic edifice that was altered by seawater-rock interaction at low temperature, whereas the lower δ18O values from southern Kamaʻehu result from assimilation of such materials altered at high temperature. [ABSTRACT FROM AUTHOR]

The Siberian Arctic is warming rapidly, causing permafrost to thaw and altering the biogeochemistry of aquatic environments, with cascading effects on the coastal and shelf ecosystems of the Arctic Ocean. The Lena River, one of the largest Arctic rivers, drains a catchment dominated by permafrost. Baseline discharge biogeochemistry data are necessary to understand present and future changes in land-to-ocean fluxes. Here, we present a high-frequency 4.5-year-long dataset from a sampling program of the Lena River's biogeochemistry, spanning April 2018 to August 2022. The dataset comprises 587 sampling events and measurements of various parameters, including water temperature, electrical conductivity, stable oxygen and hydrogen isotopes, dissolved organic carbon concentration and 14C, colored and fluorescent dissolved organic matter, dissolved inorganic and total nutrients, and dissolved elemental and ion concentrations. Sampling consistency and continuity and data quality were ensured through simple sampling protocols, real-time communication, and collaboration with local and international partners. The data are available as a collection of datasets separated by parameter groups and periods at https://doi.org/10.1594/PANGAEA.913197 (Juhls et al., 2020b). To our knowledge, this dataset provides an unprecedented temporal resolution of an Arctic river's biogeochemistry. This makes it a unique baseline on which future environmental changes, including changes in river hydrology, at temporal scales from precipitation event to seasonal to interannual can be detected. [ABSTRACT FROM AUTHOR]

[Display omitted] • We provide He-Sr-Nd-Pb-O isotopes of the Korean Peninsula basalts. • The source lithology is a complex mixture of peridotite and pyroxenite sources. • SCLM caused geochemical enrichment and low 3He/4He ratios in the basalts. The Earth's mantle is considered to be geochemically heterogeneous, which is reflected by the diverse compositions of oceanic island basalts (OIB). The mantle enrichment resulting in this is primarily attributed to the influx of recycled crustal materials into the mantle through subduction. Additionally, the sub-continental lithospheric mantle (SCLM) complicates the elucidation of mantle heterogeneity. From this perspective, Northeast Asia, where the Pacific stagnant slab in the mantle transition zone and the SCLM distribution are presented, is the suitable site for examining the upper mantle scale enrichment. Here we report He-Sr-Nd-Pb-O isotope compositions of Cenozoic basalts found around the Korean Peninsula to illustrate the source lithology and components that caused mantle heterogeneity. Our measured helium isotope ratios ranging from 5.7 to 7.3 R a (3He/4He ratio of air, R a = 1.39 x 10-6) are mostly within the SCLM range (6.1 ± 0.9 R a) but lower than the mid-ocean ridge basalt range (MORB; 8 ± 1 R a). The Sr-Nd-Pb isotope compositions of the basalts generally display a mixture of depleted MORB mantle (DMM), enriched mantle 1 (EM1), and enriched mantle 2 (EM2) components. In addition, the basalts have δ18O olivine (vs. V-SMOW) values ranging from 4.7 to 5.7 ‰ that deviate from the DMM range (δ18O olivine = 5.1 ± 0.2 ‰). Our isotopic analysis results highlight the role of a pyroxenite source in the metasomatized SCLM in the genesis of basalts, and the low 3He/4He ratios of the basalts indicates a significant contribution of SCLM. Moreover, the delaminated cratonic SCLM and asthenosphere-lithosphere interaction are scenarios for the low 3He/4He ratios. Therefore, we propose that mixing of DMM (high 3He/4He ratio; 7 to 9 R a) and the metasomatized SCLM (low 3He/4He ratio; 5 to 7 R a) allowed enrichment within the upper mantle scale for the Cenozoic intraplate magmatism in Northeast Asia. [ABSTRACT FROM AUTHOR]

The world's longest tree-ring chronology comprises thousands of oak and pine series from Germany and continuously covers the Holocene back to 12,325 cal BP. A lack of relict wood from the Younger Dryas cold reversal ca. 12,900-11,700 cal BP, however, challenges the extension of this absolutely dated ring width record further back in time. Here, we combine 646 high-resolution stable oxygen isotope and 795 radiocarbon measurements from subfossil pines that grew during the Younger Dryas at three different sites near Zurich, Switzerland, to extend the record. Coherency of the oxygen isotope variations secures internal crossdating, and radiocarbon wiggle-matching places the final 425-year-long ring-width chronology between 12,716 and 12,292 cal BP with an uncertainty of ±8 years. Our study describes an important step towards annual dating precision further into the Late Glacial period. [ABSTRACT FROM AUTHOR]

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Stromatolites, distinctive fossil records within Precambrian strata, are essential for investigating the depositional environments of early Earth and the geological settings conducive to hydrocarbon formation. The Luonan area is located in Shaanxi Province, China, where a large number of stromatolites have been discovered within the Mesoproterozoic Erathem, providing new perspectives on paleoenvironment and reservoir spaces. This study analyzes the morphology of stromatolites, associated microorganisms, mineralogy, and cathodoluminescence from the carbonate rocks of the Jixian System. Carbon and oxygen isotope analyses help reconstruct paleosalinity and climate, enhancing understanding of their petroleum geological significance. Combining carbon and oxygen isotope analysis with the fine observation and description of stromatolite can better reconstruct the paleoenvironmental features of the Mesoproterozoic Era. The results indicated a narrow range of carbon isotope values (δ13C: −5.81‰ to −2.43‰; mean: −4.03‰) and oxygen isotope values (δ18O: −9.06‰ to −5.64‰). The Longjiayuan Formation is characterized by high CaO and MgO content, with low SiO2 and minimal terrigenous input, in contrast with the Fengjiawan Formation, which exhibits elevated SiO2 and greater terrigenous material. The Luonan stromatolites display prominent rhythmic laminations, primarily composed of dolomite, indicating a potential for hydrocarbon source rocks. Stromatolite morphologies, including layered, columnar, and wavy forms, reflect varied depositional microfacies. The alternating bright and dark laminae, rich in CaO and CO2 but differing in Ca2+ and Mg2+ concentrations, signify seasonal growth cycles. These Mesoproterozoic stromatolites developed in a warm, humid, and stable climatic regime, within a marine anoxic-to-suboxic setting, typically in intertidal or supratidal zones with low hydrodynamic energy. In the southern margin of the North China Craton, stromatolites from the Mesoproterozoic Era are extensively developed and exhibit distinct characteristics. Due to the biogenic alteration of stromatolites, the porosity of the rock increased. These stromatolites have altered the physical properties of the host rocks to some extent, suggesting the possibility of becoming effective hydrocarbon reservoirs. This has significant implications for deep oil and gas exploration, providing valuable guidance for future prospecting efforts. [ABSTRACT FROM AUTHOR]

Oxygen isotope ratios (δ18O) of tree-ring cellulose and historical documentary records are widely used to explore the hydroclimatic conditions of the past. In this study, we attempted to reconstruct chronologies of local climate disasters spanning 4 centuries in central Japan using these proxy data. For tree-ring δ18O measurements, we prepared cellulose samples from a long-living cedar tree with continuously broad ring widths. To enhance the temporal resolution, we divided each annual ring into several (mainly six) segments. Analysis of the correlations with observed relative humidity and precipitation data revealed that the intra-ring δ18O variations in the sample tree reflected the hydroclimatic conditions from April to July in each year. Subsequently, we chronologically listed the occurrence of eight types of disasters in the 17th to 19th centuries in the area adjacent to the sample tree according to 20 titles of "Town/City history", which is a compilation of historical documentary records from the local municipality. By comparison with the intra-ring δ18O data, we found that most of the major droughts and long rains recorded in the historical documents occurred in the Baiu rainy season (typically June–July) or pre-Baiu season, corresponding to the growing season of the sample tree. Based on an analysis of the intra-ring δ18O variation for documentary-based drought and long-rain years, we set thresholds of intra-ring δ18O values to identify and extract drought and long-rain years. Drought and long-rain chronologies obtained by applying these thresholds were temporally continuous, complementing those based on documentary records. They depicted the relationships between the frequency of these climate disasters and the occurrence of major famines and the long-term tendency of length and magnitude of the Baiu rainy season in historical times. [ABSTRACT FROM AUTHOR]

Salt lake brine-type potassium-lithium deposits play an important role as a strategic mineral resource that is in short supply in China and the rest of the world. In the case of long-term, high-intensity exploitation of brine resources, if large-scale active faults are encountered, these faults will form advantageous channels for brine migration. In some special cases, the surface fresh water leaks into these advantageous channels and will soon produce a large amount of fresh water in the brine mining well area, resulting in the destruction of the mining well and in the reduction in the potassium lithium grade of the brine. Based on the monitoring of the chemical components and hydrogen and oxygen isotopes of brine in mining wells, combined with the principle of stable isotope conservation, the influence of freshwater leakage accidents on brine extraction wells was quantitatively calculated. The amount of fresh water added to brine by accident is approximately 78%. This further indicates that it is necessary to strengthen long-term monitoring of the chemical components of confined brine to ensure sustainable and stable production. [ABSTRACT FROM AUTHOR]

Identifying the various components contributing to river discharge can be challenging. This study relies on stable isotopes and electrical conductivity (EC) of water as tracers to distinguish the different components contributing to total river discharge. Additionally, we have made an effort to comprehend the processes that may influence glacier ice melt as well as the limits of oxygen-based hydrograph separation. Two distinct geographic domains in terms of climates and topographies were examined. The first study site represents the upper Ganga catchment (central Himalaya), while the second site is located in the Chandra sub-basin in western Himalaya. Errors in estimating the proportion of glacier melt in isotope mixing model are likely if end-member isotopic compositions, are not well defined, particularly for rainfall. Hydrograph separation results indicate that snowmelt is the largest contributor to total river flow in both regions. The contribution of snowmelt to the total runoff of the upper Ganges ranged from ∼60% to 70%. The estimated contributions of glacier melt varied from 36% to 63% in upper Ganga headwater to 6% to 15% at Devprayag and ∼8% at Rishikesh. In the Hamtah River, glacier and snowmelt contributions, quantified using a two-component mixing model, ranged from 10% to 14% during the pre- and post-monsoon seasons of 2013. The significant spatial and temporal variability, coupled with overlapping isotopic signatures, suggests complex glacio-fluvial interactions in these catchments. Local slow-moving air masses with whirling motion closer to the study area irrespective of the direction, and air parcels coming through Bay of Bengal branch are characterized by depleted isotopic rainfall compared to air masses originating from the Arabian Sea. [ABSTRACT FROM AUTHOR]

This study investigates the relationship between oxygen isotope ratios (δ18 O) in oak tree ring cellulose and past drought variability in Letea Forest, Romania. A δ18 O site chronology spanning 1803–2020 was compiled from seven individual time series. δ18 O values exhibited a significant negative correlation with moisture-related variables (cloud cover, relative humidity, and precipitation) and a positive correlation with temperature and sunshine duration. This confirms that δ18 O from tree rings can be a good proxy for moisture availability. The strongest correlation was found between δ18 O and the August Standardized Precipitation Evapotranspiration Index for an accumulation period of 9 months (SPEI9) for central and eastern Europe. This highlights SPEI9 as a superior indicator of drought compared to individual parameters like temperature or precipitation. Using a linear regression model, we reconstructed August SPEI9 variability for the past 200 years. The reconstruction captured interannual and decadal variations, with distinct wet and dry periods. Analysis of large-scale atmospheric circulation patterns revealed a link between high δ18 O values (indicating dry conditions) and a high-pressure system over the North Atlantic. Conversely, low δ18 O values (indicating wet conditions) corresponded to negative pressure anomalies over Europe. Moreover, extreme values of δ18 O are also associated with the prevalence of a hemispheric teleconnection pattern, namely wave number 4. This δ18 O chronology and the corresponding August SPEI9 reconstruction offer valuable tools for understanding past climate variability and its relationship with large-scale atmospheric and oceanic circulation patterns. [ABSTRACT FROM AUTHOR]

This paper reports a high-resolution isotopic study of medieval horse mobility, revealing their origins and in-life mobility both regionally and internationally. The animals were found in an unusual horse cemetery site found within the City of Westminster, London, England. Enamel strontium, oxygen, and carbon isotope analysis of 15 individuals provides information about likely place of birth, diet, and mobility during the first approximately 5 years of life. Results show that at least seven horses originated outside of Britain in relatively cold climates, potentially in Scandinavia or the Western Alps. Ancient DNA sexing data indicate no consistent sex-specific mobility patterning, although three of the five females came from exceptionally highly radiogenic regions. Another female with low mobility is suggested to be a sedentary broodmare. Our results provide direct and unprecedented evidence for a variety of horse movement and trading practices in the Middle Ages and highlight the importance of international trade in securing high-quality horses for medieval London elites.

This article investigates the harvest month for bent-nose clams (Macoma nasuta) at CA-ALA-11, an estuarine site in the modern-day city of Alameda along the San Francisco Bay. The archaeological deposit in which the clam shells were recovered dates primarily to the Early Period (3,350–2,550 cal BP) and Early-Middle Transition (2,550–2,150 cal BP), although some activity continues through 2,650 BP. Season of harvest estimates for clams offers insight into Indigenous use of estuarine resources and the degree of sedentism or length of habitation at this locality. Water salinity varies predictably in San Francisco Bay, from annual lows in winter to highs in summer. We used oxygen isotopes (δ18O) to estimate season of harvest by sampling at the intact terminal growth edge of the shell, which records salinity at the time of harvest. Three additional samples represent earlier periods of shell growth. Results show that while clams comprise a minority of the shellfish harvested, clamming took place between January and August, with a marked peak in mid-winter (February). There is no evidence for fall harvesting, which suggests that people were either not living at CA-ALA-11 during this time or focused on acquiring other seasonally available foods. We compare these results to previously published data on seasonality of clam harvesting from five other San Francisco Bay area sites.

Abstract Marine life on Earth is known back to the Archean Eon, when life on land is assumed to have been less pervasive than now. Precambrian life on land can now be tested with stable isotopes because living soil CO2 is isotopically distinct for both carbon and oxygen from both marine and volcanic CO2. Our novel compilation of previously published oxygen and carbon isotopic compositions of pedogenic and paleokarst carbonate can be compared with the coeval marine record. Long-term enrichment (to heavier isotopic composition) of oxygen, but no significant trend in carbon through time, long apparent from marine carbonate, is now demonstrated also for pedogenic and paleokarst carbonate. Oxygen isotopic enrichment is not due to changing global temperature or hypsometry, but to increased evapotranspiration and photosynthesis on larger continents. Differences in isotopic composition between land and sea have increased in an episodic fashion, peaking at times of major evolutionary innovations for life on land, and also at times of ice ages. The δ13C and δ18O divergences between land and sea correspond to terrestrial productivity spikes including evolution of Neoproterozoic (635 Ma) lichens, middle Ordovician (470 Ma) non-vascular land plants, middle Devonian (385 Ma) forests, early Cretaceous (125 Ma) angiosperms, and middle Miocene (20 Ma) sod grasslands.

Introduction: The Global Meteoric Water Line (GMWL) describes the linear relationship between stable hydrogen (δ 2H) and oxygen (δ 18O) isotopes in precipitation over large spatial scales and therefore represents a unique reference for water isotopic values. Although trees have the potential to capture the isotopic composition of precipitation, it remains unclear if the GMWL can be reconstructed from tree-ring stable isotopes, since δ 18O and δ 2H undergo in vivo physiological fractionation. Methods: We analyze the tree rings δ 18O and δ 2H values from six regions along a latitudinal gradient from Spain to Greenland. Results: The data show that the covariance between δ 18O and δ 2H closely follows the GMWL, which reflects the isotopic signature of large-scale precipitation patterns. We show that changes in regional tree-ring δ 18O and δ 2H values along wide latitudinal ranges are influenced by the isotopic composition of precipitation with temperature and latitude being the most significant drivers of spatial variation across the studied regions. In contrast, local tree-ring δ 18O and δ 2H values are mainly controlled by plant physiological fractionation processes that mask the isotopic signature of precipitation. Conclusion: We conclude that covariance in tree-ring δ 18O and δ 2H reflects the GMWL at larger spatial scales, but not when evaluating them at individual sites. [ABSTRACT FROM AUTHOR]