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Large meteorite impacts must have strongly affected the habitability of the early Earth. Rocks of the Archean Eon record at least 16 major impact events, involving bolides larger than 10 km in diameter. These impacts probably had severe, albeit temporary, consequences for surface environments. However, their effect on early life is not well understood. Here, we analyze the sedimentology, petrography, and carbon isotope geochemistry of sedimentary rocks across the S2 impact event (37 to 58 km carbonaceous chondrite) forming part of the 3.26 Ga Fig Tree Group, South Africa, to evaluate its environmental effects and biological consequences. The impact initiated 1) a giant tsunami that mixed Fe2+-rich deep waters into the Fe2+-poor shallow waters and washed debris into coastal areas, 2) heating that caused partial evaporation of surface ocean waters and likely a short-term increase in weathering and erosion on land, and 3) injection of P from vaporization of the S2 bolide. Strata immediately above the S2 impact event contain abundant siderites, which are associated with organic matter and exhibit light and variable δ13Ccarb values. This is consistent with microbial iron cycling in the wake of the impact event. Thus, the S2 impact likely had regional, if not global, positive and negative effects on life. The tsunami, atmospheric heating, and darkness would likely have decimated phototrophic microbes in the shallow water column. However, the biosphere likely recovered rapidly, and, in the medium term, the increase in nutrients and iron likely facilitated microbial blooms, especially of iron-cycling microbes. [ABSTRACT FROM AUTHOR]

While simultaneous radiocarbon and δ13C measurements have been available for organic materials (by accelerator mass spectrometry, AMS, and isotope ratio mass spectrometry, IRMS, respectively), this has not been possible for carbonates until now. Using an existing interface for gas ion source AMS measurements, we developed a prototype for a universal gas interface that allows simultaneous measurement of both carbon isotope ratios from potentially any source of CO2. First results obtained from reference materials (IAEA-C6, OxaII, PhA, IAEA-C1, IAEA-C2, ETH-4) show that for both organic as well as carbonate samples, the precision of radiocarbon measurements in the coupled mode is comparable to routine standalone AMS measurements. For IRMS δ13C measurements, the performance for different materials shows more variation with precisions ranging from 0.07‰ to 0.47‰. However, both organic materials and carbonates can achieve precisions as good as 0.13‰. Once fully automated, the method shows potential for filling the gap of simultaneous carbon isotope measurements for non-organic materials. [ABSTRACT FROM AUTHOR]

Numerous recent studies have tested the clumped isotope (Δ47) thermometer on a variety of biogenic carbonates such as foraminifera and bivalves and showed that most follow a common calibration. However, there may be a difference between biogenic-carbonate-based calibrations and the most recent inorganic carbonate calibrations that are assumed to have formed close to isotopic equilibrium. Biogenic calibrations such as those based on foraminifera from seafloor sediments suffer from uncertainties in the determination of the calcification temperatures. Therefore, well-constrained laboratory cultures without temperature uncertainty can help resolve these discrepancies. Although the sample size requirements for a reliable Δ47 measurement have decreased over the years, the availability and preservation of many biogenic carbonates are still limited and/or require substantial time to be extracted from sediments in sufficient amounts. Coccoliths, on the other hand, are abundant and often well-preserved in sediments, and they are a potential interesting target for palaeoceanography. We thus determined the Δ47 –temperature relationship for coccoliths due to their relative ease of growth in the laboratory. The carbon and oxygen isotopic compositions of coccolith calcite have limited use in palaeoenvironmental reconstructions due to physiological effects that cause variability in the carbon and oxygen isotopic fractionation during mineralization. However, the relatively limited data available suggest that clumped isotopes may not be significantly influenced by these effects. We cultured three species of coccolithophores under controlled carbonate system conditions with CO 2(aq) concentrations between 5 and 45 µM , pH between 7.9 and 8.6 units, and temperatures between 6 and 27 °C. Our well-constrained results agree with a previous culture study that there are no apparent species- or genus-specific vital effects on the Δ47 –temperature relationship in coccolithophores despite significant deviations from equilibrium in the C and O isotopic composition. We find that while varying environmental parameters other than temperature does not have a significant effect on Δ47 , changing the parameters yields coccolith Δ47 –temperature calibrations that agree within 1.2 ppm. Our coccolith-specific Δ47 –temperature calibration with well-constrained temperatures shows a consistent, positive offset of 2–3 °C to the inorganic carbonate calibrations, which point to as yet unknown coccolith-specific disequilibrium effects. Thus, we suggest the use of our coccolith-specific calibration for further coccolith palaeoceanographic studies and that calibrations derived from laboratory-grown biogenic carbonates are desirable to reinforce the confidence of clumped-isotope-based temperature reconstructions in palaeoceanography. [ABSTRACT FROM AUTHOR]

Discerning ecosystem change and food web dynamics underlying anthropogenic eutrophication and the introduction of non-native species is necessary for ensuring the long-term sustainability of fisheries and lake biodiversity. Previous studies of eutrophication in Lake Victoria, eastern Africa, have focused on the loss of endemic fish biodiversity over the past several decades, but changes in the plankton communities over this same time remain unclear. To fill this gap, we examined sediment cores from a eutrophic embayment, Mwanza Gulf, to determine the timing and magnitude of changes in the phytoplankton and zooplankton assemblages over the past century. Biogeochemical proxies indicate nutrient enrichment began around ~ 1920 CE and led to rapid increases in primary production, and our analysis of photosynthetic pigments revealed three zones: pre-eutrophication (prior to 1920 CE), onset of eutrophication with increases in all pigments (1920–1990 CE), and sustained eutrophication with cyanobacterial dominance (1990 CE–present). Cladoceran remains indicate an abrupt decline in biomass in ~ 1960 CE, in response to the cumulative effects of eutrophication and lake-level rise, preceding the collapse of haplochromine cichlids in the 1980s. Alona and Chydorus, typically benthic littoral taxa, have remained at relatively low abundances since the 1960s, whereas the abundance of Bosmina, typically a planktonic taxon, increased in the 1990s concurrently with the biomass recovery of haplochromine cichlid fishes. Overall, our results demonstrate substantial changes over the past century in the biomass structure and taxonomic composition of Mwanza Gulf phytoplankton and zooplankton communities, providing a historical food web perspective that can help understand the recent changes and inform future resource management decisions in the Lake Victoria ecosystem. [ABSTRACT FROM AUTHOR]

Carbonate‐brucite chimneys are a characteristic of low‐ to moderate‐temperature, ultramafic‐hosted alkaline hydrothermal systems, such as the Lost City hydrothermal field located on the Atlantis Massif at 30°N near the Mid‐Atlantic Ridge. These chimneys form as a result of mixing between warm, serpentinization‐derived vent fluids and cold seawater. Previous work has documented the evolution in mineralogy and geochemistry associated with the aging of the chimneys as hydrothermal activity wanes. However, little is known about spatial heterogeneities within and among actively venting chimneys. New mineralogical and geochemical data (87Sr/86Sr and stable C, O, and clumped isotopes) indicate that the brucite and calcite precipitate at elevated temperatures in vent fluid‐dominated domains in the interior of chimneys. Exterior zones dominated by seawater are brucite‐poor and aragonite is the main carbonate mineral. Carbonates record mostly out of equilibrium oxygen and clumped isotope signatures due to rapid precipitation upon vent fluid‐seawater mixing. On the other hand, the carbonates precipitate closer to carbon isotope equilibrium, with dissolved inorganic carbon in seawater as the dominant carbon source and have δ13C values within the range of marine carbonates. Our data suggest that calcite is a primary mineral in the active hydrothermal chimneys and does not exclusively form as a replacement of aragonite during later alteration with seawater. Elevated formation temperatures and lower 87Sr/86Sr relative to aragonite in the same sample suggest that calcite may be the first carbonate mineral to precipitate. Plain Language Summary: At the Lost City hydrothermal field, warm alkaline fluids are discharging out of uplifted mantle rocks. When vent fluids mix with seawater at the seafloor, carbonate and brucite minerals form spectacular towers up to 60 m high. Systems like Lost City are important because the reaction between water and rocks provides carbon and energy sources for microbial life. However, we still do not fully understand what controls the mineralogy and geochemistry of the Lost City hydrothermal chimneys. In this paper, we suggest that the extent of mixing between the hydrothermal fluids and seawater influences the mineralogy and geochemistry of the chimneys. Calcite, which was previously thought to form only during alteration of aragonite by seawater, can also form during seawater‐hydrothermal fluid mixing. Both calcite and brucite form in the interior of the chimneys where vent fluid is more dominant. Aragonite, on the other hand, forms in the exterior of the structures from seawater‐rich fluids. Lastly, because minerals precipitate rapidly during fluid mixing, the stable isotope geochemistry of the carbonates mostly records the composition and temperature of seawater and not the mixed fluid. Thus, care should be exercised in interpreting mineral geochemical data from similar systems. Key Points: The mineralogy and geochemistry of Lost City chimneys are controlled by the extent of mixing between hydrothermal fluids and seawaterBrucite and calcite precipitate in vent fluid dominated zones while aragonite forms in the exterior of the structures in seawater‐rich zonesCarbonates precipitate in isotopic disequilibrium and record the O and C stable isotope composition of seawater dissolved inorganic carbon [ABSTRACT FROM AUTHOR]

Although the serpentinite‐hosted Lost City hydrothermal field (LCHF) was discovered more than 20 years ago, it remains unclear whether and how the presence of microbes affects the mineralogy and textures of the hydrothermal chimney structures. Most chimneys have flow textures comprised of mineral walls bounding paleo‐channels, which are preserved in inactive vent structures to a varying degree. Brucite lines the internal part of these channels, while aragonite dominates the exterior. Calcite is also present locally, mostly associated with brucite. Based on a combination of microscopic and geochemical analyses, we interpret brucite, calcite, and aragonite as primary minerals that precipitate abiotically from mixing seawater and hydrothermal fluids. We also observed local brucite precipitation on microbial filaments and, in some cases, microbial filaments may affect the growth direction of brucite crystals. Brucite is more fluorescent than carbonate minerals, possibly indicating the presence of organic compounds. Our results point to brucite as an important substrate for microbial life in alkaline hydrothermal systems. Plain Language Summary: Water‐serpentinite reactions at the Lost City hydrothermal field (LCHF) are considered similar to the interactions between seawater and volcanic rocks of the early Earth. The vent fluids that form as a result of this interaction are rich in organic compounds that serve as food and hydrogen that provides energy for microbial life. Systems such as Lost City are ideal sites for investigating processes relevant to early life on Earth. Dense microbial communities live in the mineral structures that form from mixing between vent fluids and seawater at the LCHF. The effect of these microbial inhabitants on the mineralogy and textures of the hydrothermal chimneys is still unknown. This study aims to better understand the mineralogy of the hydrothermal chimneys at Lost City and the relationships between microbes and minerals. Calcite and brucite form in the interior of the chimneys, while aragonite forms on the exterior. Brucite forms inorganic mineral membranes that bound cavities where microbes may live. Unlike calcite and aragonite, brucite is spatially closely associated with microbial activity. Key Points: Lost City hydrothermal chimneys preserve flow textures defined by mineral membranes bounding paleo‐channels and form a network of cavitiesThe backbone of the chimney structure is initially brucite. Carbonates precipitate on brucite as the chimneys continue to formBrucite is the preferred substrate for the growth of microbial biofilms within the chimneys [ABSTRACT FROM AUTHOR]

It has recently been observed, that a change in the crop spectrum happened during the so-called Middle Neolithic in France at ca. 4000 BC. An agricultural system based on free-threshing cereals (naked wheat and naked barley) seems to shift to one based on glume wheats. This is a major change for traditional farmers and this paper aims to shed light on its possible causes. Here we describe the results of new investigations in a key area for the understanding of this process: the NW Mediterranean arch, where free-threshing cereals are the main cultivars since ca. 5100 BC. New data confirm that the shift towards glume wheats is also observed in some sites of the NE of the Iberian Peninsula and that among the glume wheats that spread at ca. 4000 BC we should not only consider emmer and einkorn but also Timopheevi's wheat. Stable isotope analyses indicate no major decrease in soil fertility or alterations in local precipitation regimes. The agricultural change may be the result of a combination of the spread of damaging pests for free-threshing cereals and presumably new networks being developed with the North-eastern part of Italy and the Balkans. [ABSTRACT FROM AUTHOR]

We investigated calcites and dolomites precipitated during burial diagenesis of the Upper Triassic (Norian) continental siliciclastics from sub-surface reservoirs of the northern Paris Basin (Chaunoy Formation) that experienced a thermal maximum >100°C during Late Cretaceous times. Relative carbonate precipitation timing was established via petrographic analyses. The diagenetic carbonates were further investigated by fluid inclusion and clumped isotope (Δ47) thermometry. The two thermometric datasets were interpreted by evaluating the possible occurrence of inclusion thermal reequilibration and Δ47 solid-state reordering, based on the known basin thermal history and the three existing Δ47 reordering models. By considering the fluid inclusion and Δ47 datasets obtained and the various Δ47 reordering models, different carbonate precipitation scenarios, in terms of timing and parent fluid composition (818Ofluid), were inferred. These results underline that in samples having experienced thermal maximum >100°C, accuracy and interpretation of fluid inclusion and Δ47 thermometry data (especially on calcite) may be biased by thermal reequilibration and solid-state reordering. The results converge towards the need of jointly applying fluid inclusion and Δ47 thermometry on the same carbonate phases to evaluate all the possible precipitation scenarios. The most likely carbonate precipitation scenarios, based on Δ47 thermometry data, point at the precipitation of two calcite phases during Early to Late Jurassic times and of one dolomite phase during the Late Cretaceous. The parent fluids possibly were original formation waters of the Chaunoy Fm. that mixed with brines migrating from the East, where time equivalent evaporitic deposits occur. The proposed precipitation model for calcites and dolomites, involving different pulses of brine migration, and the dominance of calcite phases were not recorded by previous studies on the Upper Triassic units. These latter results may be of interest to evaluate the reservoir potential of the Chaunoy Fm. in this underexplored portion of the Paris Basin. [ABSTRACT FROM AUTHOR]

Numerous recent studies have tested the clumped isotope (Δ47) thermometer on a variety of biogenic carbonates such as foraminifera and bivalves and showed that all follow a common calibration. While the sample size requirements for a reliable Δ47 measurement have decreased over the years, the availability and preservation of many biogenic carbonates is still limited and/or require substantial time to be extracted from sediments in sufficient amounts. We thus determined the Δ47-temperature relationship for coccolith carbonate, which is abundant and often well-preserved in sediments. The carbon and oxygen isotopic compositions of coccolith calcite have limited use in palaeoenvironmental reconstructions due to physiological effects that cause variability in the carbon and oxygen isotopic values. However, the relatively limited data available suggest that clumped isotopes may not be influenced by these effects. We cultured three species of coccolithophores in well- constrained carbonate system conditions with a CO2(aq) between 5 and 45 ^M and temperatures between 6°C and 27°C. Our results agree with a previous culture study that there are no species- or genus-specific effects on the Δ47-temperature relationship in coccolithophores and find that varying environmental parameters other than temperature also do not have a significant effect. Our coccolith-specific Δ47-temperature calibration agrees within ±1°C of other biogenic carbonate calibrations yet all biogenic carbonate calibrations show a consistent offset of ≥2°C relative to the inorganic carbonate calibrations. Thus, all biogenic specific calibrations can be used interchangeably and must be used for the reconstruction of calcification temperatures in biogenic carbonates. [ABSTRACT FROM AUTHOR]

Numerous recent studies have tested the clumped isotope (Δ47) thermometer on a variety of biogenic carbonates such as foraminifera and bivalves and showed that all follow a common calibration. While the sample size requirements for a reliable Δ47 measurement have decreased over the years, the availability and preservation of many biogenic carbonates is still limited and/or require substantial time to be extracted from sediments in sufficient amounts. We thus determined the Δ47-temperature relationship for coccolith carbonate, which is abundant and often well-preserved in sediments. The carbon and oxygen isotopic compositions of coccolith calcite have limited use in palaeoenvironmental reconstructions due to physiological effects that cause variability in the carbon and oxygen isotopic values. However, the relatively limited data available suggest that clumped isotopes may not be influenced by these effects. We cultured three species of coccolithophores in well-constrained carbonate system conditions with a CO2(aq) between 5 and 45 μM and temperatures between 6 °C and 27 °C. Our results agree with a previous culture study that there are no species- or genus-specific effects on the Δ47-temperature relationship in coccolithophores and find that varying environmental parameters other than temperature also do not have a significant effect. Our coccolith-specific Δ47-temperature calibration agrees within ±1 °C of other biogenic carbonate calibrations yet all biogenic carbonate calibrations show a consistent offset of ≥2 °C relative to the inorganic carbonate calibrations. Thus, all biogenic specific calibrations can be used interchangeably and must be used for the reconstruction of calcification temperatures in biogenic carbonates. [ABSTRACT FROM AUTHOR]

The sealing characteristics of the geological formation located above a CO2 storage reservoir, the so-called caprock, are essential to ensure efficient geological carbon storage. If CO2 were to leak through the caprock, temporal changes in fluid geochemistry can reveal fundamental information on migration mechanisms and induced fluid–rock interactions. Here, we present the results from a unique in-situ injection experiment, where CO2-enriched fluid was continuously injected in a faulted caprock analogue. Our results show that the CO2 migration follows complex pathways within the fault structure. The joint analysis of noble gases, ion concentrations and carbon isotopes allow us to quantify mixing between injected CO2-enriched fluid and resident formation water and to describe the temporal evolution of water–rock interaction processes. The results presented here are a crucial complement to the geophysical monitoring at the fracture scale highlighting a unique migration of CO2 in fault zones. [ABSTRACT FROM AUTHOR]

The addition of sulfur (S) to organic matter to form organosulfur compounds is generally thought to protect organic matter from microbial degradation and promote its preservation. While most microbial sulfur cycling occurs in sulfate-rich sediments above the sulfate-methane transition zone, recently discovered active sulfur cycling in deeper sulfate-poor environments may have a yet-unquantified impact on the mineralization of organic matter. Here we investigated the fate of buried S-compounds down to 10-m sediment depth representing the entire ~13.5 kya history of the sulfate-rich alpine Lake Cadagno. Chemical profiles of sulfate and sulfur reveal that these oxidized species are depleted at the sediment surface with the concomitant formation of iron sulfide minerals. An underlying aquifer provides a second source of sulfate and other oxidants to the deepest and oldest sediment layers generating an inverse redox gradient. At both sulfate depletion zones, isotopes of chromium-reducible sulfur (CRS) and humic-bound sulfur are highly negative (−30 to −65 per mil) compared to background sulfate suggesting ongoing microbial sulfur cycling. Interestingly, humic-bound S from intermittent sediment layers within the sulfate-depleted methanogenesis zone consistently exhibits a lower δ34S than CRS in lacustrine deposits but a higher δ34S than CRS in terrestrial deposits, which could possibly be due to different reactivities of organic matter types (lacustrine versus terrestrial origin) to sulfide or the ability of microorganisms to form/degrade organic S. Although sulfate concentrations are extremely low between the sulfate depletion zones, dsrB gene libraries reveal a huge potential for microbial sulfur reduction throughout the sediment column. [ABSTRACT FROM AUTHOR]

The Middle-Jurassic Opalinus Clay is the foreseen host rock for radioactive waste disposal in central northern Switzerland. An extensive drilling campaign aiming to characterize the argillaceous formation resulted in a comprehensive drill core data set. The rheologically weak Opalinus Clay is only mildly deformed compared to the over- and underlying rock units but shows a variety of natural fractures. While these structures are hydraulically indistinguishable from macroscopically non-deformed Opalinus Clay today, their analysis allows for a better understanding of the deformation behaviour in the geological past. Here, we present an overview of the different fracture and fault types recorded in the Opalinus Clay and a detailed microstructural characterization of veins—natural dilational fractures healed by secondary calcite and celestite mineralizations. Macroscopic drill core analysis revealed five different natural fracture types that encompass tension gashes of various orientations with respect to bedding and small-scale faults with displacements typically not exceeding the drill core diameter. The occurrence of different fault types generally fits well with the local tectonic setting of the different drilling sites and with respect to the neighbouring regional fault zones. The microstructural investigations of the various vein types revealed their often polyphase character. Fibrous bedding-parallel veins of presumable early age were found to be overprinted by secondary slickenfibres. The polyphase nature of fibrous bedding parallel veins and slickenfibres is supported by differing elemental compositions, pointing towards repeated fracturing and mineralization events. Direct dating of vein calcites with U–Pb was unsuccessful. Nevertheless, age constraints can be inferred from structural orientations and fault slip kinematics. Accordingly, some of the veins already formed during sediment compaction in Mesozoic times, others possibly relate to Early Cenozoic foreland uplift. The youngest veins are most likely related to Late Cenozoic regional tectonic events, such as the Jura fold-and-thrust belt to the south and the Hegau-Lake Constance Graben to the northeast of the study area. During these latest tectonic events, previously formed veins acted as rheologically stiff discontinuities in the otherwise comparably weak Opalinus Clay along which deformation of the rock formation was re-localized. [ABSTRACT FROM AUTHOR]

The abundance and types of reef-bearing carbonate platforms reflect the evolution of Devonian climate, with conspicuous microbial-algal reefs in the warm Early and Late Devonian and sponge-coral reefs in the cooler Middle Devonian. A dolomitized Wenlock-Lower Devonian microbial-algal reef-bearing carbonate platform hosts epigenetic copper-cobalt-germanium (Cu-Co-Ge) sulfide mineralization at Ruby Creek-Bornite in the Brooks Range, Alaska. Here, we present rhenium-osmium (Re-Os) radiometric ages and molybdenum and sulfur (δ98/95Mo = +2.04 to +5.48‰ and δ34S = −28.5 to −1.8‰) isotope variations for individual Cu-Co-Fe sulfide phases along the paragenetic sequence carrollite-bornite-pyrite. In the context of a hot, extensional passive margin, greenhouse conditions in the Early Devonian favored restriction of platform-top seawater circulation and episodic reflux of oxidized brines during growth of the carbonaceous carbonate platform. Molybdenum and sulfur isotope data signal the stepwise reduction of hot brines carrying Cu during latent reflux and geothermal circulation for at least ca. 15 million years from the Early Devonian until Cu-Co sulfide mineralization ca. 379–378 million years ago (Ma) in the Frasnian, Late Devonian (weighted mean of Re-Os model ages of carrollite at 379 ± 15 Ma [n = 4]; Re-Os isochron age of bornite at 378 ± 15 Ma [n = 6]). On the basis of petrographic relationships between sulfides and solid bitumen, and the Mo and S isotope data for sulfides, we imply that the endowment in critical metals (e.g., Co, Ge, Re) in the Ruby Creek-Bornite deposit is linked to the activity of primary producers that removed trace metals from the warm Early Devonian seawater and concentrated Co, Ge, and Re in algal-bacterial organic matter in carbonate sediments. [ABSTRACT FROM AUTHOR]

Ikaite and pseudomorphs thereafter ("glendonites") are a potentially powerful tool for palaeoclimatic studies, as a low-temperature proxy. However, much uncertainty still surrounds the drivers of ikaite formation, in particular prerequisite thermal and chemical conditions. Furthermore, the ikaite to glendonite transformation is not fully understood, and it was unclear which calcite phases in glendonites were ikaite-derived and which were later diagenetic calcites. This leads to difficulties in choosing which phase to analyse in order to reconstruct the original ikaite growth environmental conditions. Petrographic examination of air-transformed ikaite from the Isatkoak Lagoon in Utqiaġvik, Alaska, confirms that both 'Type I' and 'Type II' calcite phases seen in glendonites are directly derived from ikaite breakdown and not from secondary sources. Clumped isotope temperature reconstructions for transformed ikaites from Utqiaġvik, and comparison to Recent glendonites from the White Sea, Russia, confirm that clumped isotope thermometry may be used to reconstruct ikaite growth temperatures, whilst stable isotopes and minor elemental analysis reveal that a range of geochemical conditions characterise ikaite growth sites. [ABSTRACT FROM AUTHOR]

The excellent preservation of the waterlogged botanical remains of the multiphase Neolithic pile-dwelling site of Zug-Riedmatt (Central Switzerland) yielded an ideal dataset to delve into the issue of plant economy of a community spanning several decades. The study identified a major change in crops where oil plants played a key role in the site's initial phase before being supplanted over the course of a few decades by naked wheat, barley and pea. Wild plants continued to be gathered albeit in different proportions. In the latest settlement phase, the changes in the local vegetation and in the values of the analyses of carbon stable isotopes suggest a less humid environment. The hypothesis is that the changes perceived in the plant economy represent a resilience strategy adopted by the inhabitants in reaction to short term local climatic alterations. The two types of soil sampling techniques (monolith and bulk) allowed comparing these results. While the density of plant remains appears to be underestimated among the samples collected by the monolith technique, the proportions of economic taxa remain unaffected. The findings thus reveal that when the bulk samplings are distributed carefully throughout multiphase sites and avoid mixing stratigraphical units, and if the samplings are representative of all archaeological features from a whole area, then each of the two techniques offer analogous results. [ABSTRACT FROM AUTHOR]

Using biodegradable instead of conventional plastics in agricultural applications promises to help overcome plastic pollution of agricultural soils. However, analytical limitations impede our understanding of plastic biodegradation in soils. Utilizing stable carbon isotope (13C-)labelled poly(butylene succinate) (PBS), a synthetic polyester, we herein present an analytical approach to continuously quantify PBS mineralization to 13CO2 during soil incubations and, thereafter, to determine non-mineralized PBS-derived 13C remaining in the soil. We demonstrate extensive PBS mineralization (65 % of added 13C) and a closed mass balance on PBS−13C over 425 days of incubation. Extraction of residual PBS from soils combined with kinetic modeling of the biodegradation data and results from monomer (i.e., butanediol and succinate) mineralization experiments suggest that PBS hydrolytic breakdown controlled the overall PBS biodegradation rate. Beyond PBS biodegradation in soil, the presented methodology is broadly applicable to investigate biodegradation of other biodegradable polymers in various receiving environments. This study applies stable carbon isotope labelling to study polymer biodegradation in soils. This labelling enables accurate and precise tracking of polymer carbon during biodegradation and, thereby, provides a holistic picture of this process. [ABSTRACT FROM AUTHOR]

We explore the effects of the Pliensbachian–Toarcian Boundary Event (P–ToBE) on tropical carbonate productivity in the interior to margin and slope of the Venetian Platform (Northern Italy). We document the P–ToBE for the first time in the shallow‐water platform margin, and we bio‐ and chemostratigraphically tie it to transgressive/regressive cycles. Following the latest Pliensbachian sea‐level drop and emersion, transgressive grainstones at the platform edge record the P–ToBE negative carbon isotope excursion (CIE) of 1–1.5‰, also found in marl/limestone couplets on the slope. Recovery of platform productivity was ephemeral, as the platform drowned right after the peak negative CIE and was covered by deep‐sea thin‐bedded micritic limestones. The end of the P–ToBE correlates with a regression and renewed recovery of carbonate productivity. The negative CIE of the subsequent Toarcian Oceanic Anoxic Event is recorded in open‐sea cherty limestones both at the marginal and interior platform. These limestones document an even wider transgression and the renewed partial drowning of the platform in the Serpentinus Zone. We investigate the causes of the carbon perturbation at the P–ToBE, using a simple carbon cycle model. The duration and magnitude of the CIE suggest a rapid release of methane in driving the CIE, perhaps related to the preceding sea‐level drop and associated cryosphere perturbation, or to thermogenic alteration of coals near the Karoo‐Ferrar Large Igneous Province (LIP). The extent of the warming and the magnitude of the P–ToBE CIE implies a contribution of volcanogenic carbon dioxide from the Karoo‐Ferrar LIP. Key Points: The Pliensbachian–Toarcian Boundary Event is chemo‐ and lithostratigraphically analyzed in sections of the Venetian carbonate platformWe find a negative carbon isotope excursion at the Pliensbachian–Toarcian boundary in slope, and, for the first time, in platform sedimentsNumerical model of the global carbon cycle points toward low δ13C carbon as substantial source of total carbon release during this event [ABSTRACT FROM AUTHOR]

A large part of the hydrated oceanic lithosphere consists of serpentinites exposed in ophiolites. Serpentinites constitute reactive chemical and thermal systems and potentially represent an effective sink for CO2. Understanding carbonation mechanisms within ophiolites are almost exclusively based on studies of outcrops, which can limit the interpretation of fossil hydrothermal systems. We present stable and radiogenic carbon isotope data that provide insights into the isotopic trends and fluid evolution of peridotite carbonation in ICDP Oman Drilling Project drill holes BA1B (400‐m deep) and BA3A (300‐m deep). Geochemical investigations of the carbonates in serpentinites indicate formation in the last 50 kyr, implying a distinctly different phase of alteration than the initial oceanic hydration and serpentinization of the Samail Ophiolite. The oldest carbonates (∼31 to >50 kyr) are localized calcite, dolomite, and aragonite veins, formed between 26°C and 43°C and related to focused fluid flow. Subsequent pervasive small amounts of dispersed carbonate precipitated in the last 1,000 years. Macroscopic brecciation and veining of the peridotite indicate that carbonation is influenced by tectonic features allowing infiltration of fluids over extended periods and at different structural levels such as along fracture planes and micro‐fractures and grain boundaries, causing large‐scale hydration of the ophiolite. The formation of dispersed carbonate is related to percolating fluids with δ18O lower than modern ground and meteoric water. Our study shows that radiocarbon investigations are an essential tool to interpret the carbonation history and that stable oxygen and carbon isotopes alone can result in ambiguous interpretations. Plain Language Summary: Water‐rock interactions that have biological and economic importance have received increasing interest in recent years. Carbon species, stored in the atmosphere, biosphere, oceans, and lithosphere, are profoundly affected by biotically and abiotically controlled exchange reactions among these reservoirs. Carbon is an essential element for life and contributes to the greenhouse effect in the form of CO2 and CH4. Unraveling water‐rock reactions that transform atmospheric CO2 into thermodynamically stable carbonates helps to better understand long‐term carbon storage in the lithosphere and its long‐term influence on climate and to better evaluate the potential for life within the lithosphere. This study uses samples recovered by drilling mantle sequences of the Wadi Tayin Massif in Oman and presents chemical data to evaluate carbon sources, speciation, and transformations. The Wadi Tayin Massif is located in the Samail Ophiolite and comprises mantle rocks. Mantle rocks react in contact with water to form serpentine and create an environment that promotes the transformation of CO2 into carbonates. Our results demonstrate large‐scale carbonization of the massif and a dominance of dispersed carbonate formation below the surface. Our study provides insights into the carbon cycle and will help to evaluate the potential of mantle rocks to store carbon and sustain life. Key Points: Two carbonate occurrences are observed: localized dolomite, calcite, and aragonite veins and pervasive dispersed carbonatesCarbonate precipitation in the peridotite occurred in the last 50 kyr at moderate temperatures, post‐dating ocean‐floor serpentinizationThe oxygen isotope composition of dispersed carbonates indicates precipitation from highly 18O‐depleted fossil groundwater [ABSTRACT FROM AUTHOR]

Petrographic and major element investigations of carbonates from seven drill cores recovered during IODP Expedition 357 on the Atlantis Massif (AM) provide information on the genesis of carbonate minerals in the oceanic lithosphere. Textural sequences and mineralogical assemblages reveal three distinct types of carbonate occurrences in ultramafic rocks that are controlled by (a) fluid composition and flow, (b) temperature, and (c) the presence of mafic intrusions. The first occurrence of carbonate consists of different generations of calcite that formed syn‐ to post‐ serpentinization. These calcites formed at temperatures between 30 and 184°C (based on clumped isotope thermometry) and from a fluid influenced by interaction with mafic intrusions. The second occurrence consists of magnesite, dolomite, calcite, and aragonite veins that also formed syn‐ to post serpentinization. These carbonates formed at temperatures between ambient and 196°C, from fluids with highly variable FeO, MnO, and SrO composition and Mg/Ca ratios, but overall high CO2 and moderate SiO2 concentrations. High FeO (3.3 wt%) and MnO (7.3 wt%) contents indicate high temperatures, high water/rock ratios, and low oxygen fugacity for both carbonate assemblages. The third occurrence consists solely of aragonite veins formed at low temperatures (<9°C) within the uplifted serpentinized peridotites. Major element analyses suggest that aragonite precipitated from seawater, which experienced little interaction with the basement. Combining these results, we propose a model that positions different carbonate occurrences in a conceptual framework considering mafic domains in the peridotites and fluid heterogeneities during progressive exhumation and alteration of the AM. Plain Language Summary: Carbonates form in diverse geological settings within the continental and oceanic lithosphere. They present a safe and permanent geological storage for CO2, which is an important greenhouse gas. Thus, understanding the mechanism that drives carbonate formation will help to find a solution to stabilize atmospheric CO2 and reduce global warming. This study uses petrographic and chemical investigations of drilled lithosphere samples from the Atlantis Massif to create a model for carbonate formation. The Atlantis Massif is located in the Atlantic Ocean close to the Mid‐Atlantic‐Ridge. It is characterized by a high amount of mantle rocks exposed at the seafloor. Mantle rocks react in contact with seawater to form serpentine and create an environment that leads to the transformation of CO2 into carbonates. Our results demonstrate a high variability in carbonate chemistry as well as timing and temperature of formation within the Atlantis Massif. It shows that carbonate formation not only depends on the chemistry of the fluid from which it precipitates but also on the physical properties of the fluid. Furthermore, the study shows that Mg‐rich carbonate (magnesite) formation can occur in an oceanic setting, which is predicted but rarely observed in natural settings. Key Points: Carbonate precipitation is controlled by fluid composition and flow, temperature, and the presence of mafic intrusionsMagnesite and dolomite formed at high Mg/Ca ratios and zones of channelized flow in serpentinized peridotites at the Atlantis MassifCO2 capture is limited in the shallower crust, concentrated around Lost City, but may be more extended in deeper circulation [ABSTRACT FROM AUTHOR]

Foreland fold-and-thrust belts (FTBs) record long-lived tectono-sedimentary activity, from passive margin sedimentation, flexuring, and further evolution into wedge accretion ahead of an advancing orogen. Therefore, dating fault activity is fundamental for plate movement reconstruction, resource exploration, and earthquake hazard assessment. Here, we report U–Pb ages of syn-tectonic calcite mineralizations from four thrusts and three tear faults sampled at the regional scale across the Jura fold-and-thrust belt in the northwestern Alpine foreland (eastern France). Three regional tectonic phases are recognized in the middle Eocene–Pliocene interval: (1) pre-orogenic faulting at 48.4±1.5 and 44.7±2.6 Ma associated with the far-field effect of the Alpine or Pyrenean compression, (2) syn-orogenic thrusting at 11.4±1.1 , 10.6±0.5 , 9.7±1.4 , 9.6±0.3 , and 7.5±1.1 Ma associated with the formation of the Jura fold-and-thrust belt with possible in-sequence thrust propagation, and (3) syn-orogenic tear faulting at 10.5±0.4 , 9.1±6.5 , 5.7±4.7 , and at 4.8±1.7 Ma including the reactivation of a pre-orogenic fault at 3.9±2.9 Ma. Previously unknown faulting events at 48.4±1.5 and 44.7±2.6 Ma predate the reported late Eocene age for tectonic activity onset in the Alpine foreland by ∼10 Myr. In addition, we date the previously inferred reactivation of pre-orogenic strike-slip faults as tear faults during Jura imbrication. The U–Pb ages document a minimal time frame for the evolution of the Jura FTB wedge by possible in-sequence thrust imbrication above the low-friction basal decollement consisting of evaporites. [ABSTRACT FROM AUTHOR]

The carbon geochemistry of serpentinized peridotites and gabbroic rocks recovered during IODP Expedition 357 on the Atlantis Massif (AM) was examined to characterize carbon sources and the fate of dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) in seawater during long‐lived hydrothermal circulation and serpentinization. Carbon isotopes reveal three stages of carbonate formation, starting at least 38,000 yr ago: (a) Early dispersed carbonate precipitation, with low water/rock ratios and high temperatures (50°C–190°C); (b) carbonate vein formation related to high and focused fluid fluxes still at high temperatures (30°C–200°C); and (c) seawater circulation leading to cold carbonate precipitation controlled by late, brittle fractures during uplift, and unroofing of the oceanic core complex. Our study reveals three main DIC sources in the system: (a) DIC from abiotic hydrothermal degradation of dissolved organic matter (OM); (b) DIC from seawater; and (c) DIC from mantle‐derived volatiles. Basement rocks containing dispersed carbonates are characterized by high concentrations (∼800 ppm) of total non‐carbonate carbon (NCC) and 13C‐depleted carbonates. We propose that high seawater fluxes in the southern part of the AM likely favor the transport and incorporation of marine DOC in serpentinites and that carbonates record isotopic signals of OM decay. Our study indicates that organic carbon accounts for a significant proportion of the total carbon stored in the AM and suggests that serpentinites may be an important sink of DOC from seawater. Plain Language Summary: Carbon can be found in higher concentrations within the atmosphere, terrestrial biosphere, oceans, and lithosphere. It is an essential element for various abiotic and biotic reactions and is in the form of CO2 and CH4, an important greenhouse gas. The transfer of carbon between different reservoirs is not well constrained. This study uses samples recovered by drilling the lithosphere at the Atlantis Massif (AM) and chemical investigations to evaluate carbon sources, speciation, and transformations. The AM is located in the Atlantic Ocean close to the Mid‐Atlantic‐Ridge and comprises a high amount of mantle rocks exposed at the seafloor. Mantle rocks react in contact with water to form serpentine and create an environment that promotes the transformation of CO2 into carbonates. Our results demonstrate that the oceanic lithosphere is a significant reservoir of organic compounds and inorganic carbonates and that carbonates record the oxidation of organic matter over long periods. Our study can help to evaluate the potential of mantle rocks to store carbon and reduce CO2 emission. However, it may also provide information to evaluate the potential for life within the lithosphere, not only on Earth but also on other planets where serpentinization processes occur. Key Points: Serpentinization is associated with dispersed carbonate and multiple generations of veins formed at temperatures from 5°C to 200°CThe system has multiple carbon sources: inorganic and organic carbon from seawater, mantle‐derived carbon, and minor in situ productionAbiotic hydrothermal degradation of dissolved organic matter contributes to carbon cycling in peridotite‐hosted hydrothermal systems [ABSTRACT FROM AUTHOR]

Understanding the Earth's climate system during past periods of high atmospheric CO2 is crucial for forecasting climate change under anthropogenically-elevated CO2. The Mesozoic Era is believed to have coincided with a long-term Greenhouse climate, and many of our temperature reconstructions come from stable isotopes of marine biotic calcite, in particular from belemnites, an extinct group of molluscs with carbonate hard-parts. Yet, temperatures reconstructed from the oxygen isotope composition of belemnites are consistently colder than those derived from other temperature proxies, leading to large uncertainties around Mesozoic sea temperatures. Here we apply clumped isotope palaeothermometry to two distinct carbonate phases from exceptionally well-preserved belemnites in order to constrain their living habitat, and improve temperature reconstructions based on stable oxygen isotopes. We show that belemnites precipitated both aragonite and calcite in warm, open ocean surface waters, and demonstrate how previous low estimates of belemnite calcification temperatures has led to widespread underestimation of Mesozoic sea temperatures by ca. 12 °C, raising estimates of some of the lowest temperature estimates for the Jurassic period to values which approach modern mid-latitude sea surface temperatures. Our findings enable accurate recalculation of global Mesozoic belemnite temperatures, and will thus improve our understanding of Greenhouse climate dynamics. [ABSTRACT FROM AUTHOR]

The middle Miocene climate transition (MMCT), around 14 Ma, was associated with a significant climatic shift, but the mechanisms triggering the event remain enigmatic. We present a clumped isotope (Δ47) bottom-water temperature (BWT) record from 16.0 to 12.2 Ma from Ocean Drilling Program (ODP) Site 747 in the Southern Ocean and compare it to existing BWT records from different latitudes. We show that BWTs in the Southern Ocean reached 8–10 ∘C during the Miocene climatic optimum. These high BWT values indicate considerably warmer bottom-water conditions than today. Nonetheless, bottom-water δ 18O (calculated from foraminiferal δ 18O and Δ47) suggests substantial amounts of land ice throughout the interval of the study. Our dataset further demonstrates that BWTs at Site 747 were variable with an overall cooling trend across the MMCT. Notably, a cooling of around 3–5 ∘C preceded the stepped main increase in benthic δ 18O , interpreted as global ice volume expansion, and appears to have been followed by a transient bottom-water warming starting during or slightly after the main ice volume increase. We speculate that a regional freshening of the upper water column at this time may have increased stratification and reduced bottom-water heat loss to the atmosphere, counteracting global cooling in the bottom waters of the Southern Ocean and possibly even at larger scales. Feedbacks required for substantial ice growth and/or tectonic processes may have contributed to the observed decoupling of global ice volume and Southern Ocean BWT. [ABSTRACT FROM AUTHOR]

Last glacial North Atlantic climate is characterized by abrupt, centennial‐millennial scale climate oscillations, called Dansgaard‐Oeschger (D‐O) events. Understanding the cause and propagation of these D‐O events into Eurasia is hampered by the scarcity of quantitative paleotemperature estimates from continental archives with precise, independent age models. Here, we present land snail shell carbonate clumped isotope‐based active season paleotemperature estimates and δ13C/δ18O‐based aridity reconstructions from Greenland stadial/interstadials (GS/GI) between 31 and 26.5 ka from the 14C‐dated Dunaszekcső loess section (Hungary). This reconstruction is complemented with a new 230Th‐dated flowstone stable isotope record covering 30‐26 ka. Our snail shell clumped isotope (Δ47) data indicate growing season temperatures (GSTs) of 16°C–18°C and 7°C–14°C for the investigated interstadials and stadials, respectively. Stable carbon and oxygen stable isotope compositions of shells and flowstone calcite reveal milder interstadials with drier summers and more available moisture over the winter season, and colder stadials with annually/seasonally (winter) drier conditions, promoting increased loess/dust deposition. We propose that large‐scale ocean‐atmospheric variability, characterized by NAO phases, may have imparted a major control on transmitting abrupt North Atlantic climate event signals into continental Europe during the last glacial. Plain Language Summary: Abrupt climate changes of the last ice age had profound impacts on climate of the North Atlantic. However, the nature of these so‐called Dansgaard‐Oeschger (D‐O) warming events and impact on Eurasian climate and ecosystems is not well‐known, due to the scarcity of reliable paleotemperature estimates from continental climate archives with independent chronology. To overcome this, we present paleotemperature estimates with a new methodology (clumped isotope paleothermometry) applied on land snail shells from precisely dated loess deposits in Hungary (East Central Europe) and a stable isotope record from a nearby U‐Th‐dated flowstone (sheet‐like deposit, usually in limestone caves). Our growing season temperature estimates allow tracking of paleotemperature changes over periods of cooling and warming in East Central Europe, preceding the Last Glacial Maximum (26‐19 thousands of years ago). Our dual archive approach is based on two independent but geographically close archives, thereby increasing confidence in getting accurate results. The data show 4°C–7°C increase in growing season temperatures during warming events compared to the cold climatic periods, implying very substantial shifts in continental climates and ecosystems in East Central Europe. Key Points: We reconstruct stadial and interstadial land temperatures using clumped isotopes in land snails from southern Hungary (East Central Europe)Warming of ~4°C–7°C for Greenland interstadials 5.1 and 3 in East Central EuropeLarge‐scale ocean‐atmospheric variability may control transmission of abrupt North Atlantic climate signals into Europe [ABSTRACT FROM AUTHOR]

Previous studies have shown that microbially produced methane can be a dominant carbon source of lacustrine sedimentary macrofauna in eutrophic lakes, most likely through grazing on methane-oxidizing bacteria. Here we investigate the contributions of different carbon sources to macrofaunal biomass across five lakes in central Switzerland that range from oligotrophic to highly eutrophic. Macrofaunal communities change with trophic state, with chironomid larvae dominating oligotrophic and tubificid oligochaetes dominating eutrophic lake sediments. The 13C -isotopic data suggest that the average contribution of methane-derived carbon to the biomass of both macrofaunal groups is similar but consistently remains minor, ranging from only ∼1 % in the oligotrophic lake to at most 12 % in the eutrophic lakes. The remaining biomass can be explained by the assimilation of detritus-derived organic carbon. Low abundances of methane-cycling microorganisms in macrofaunal specimens, burrows, and surrounding sediment based on 16S ribosomal RNA (rRNA) gene sequences and copy numbers of genes involved in anaerobic and aerobic methane cycling (mcrA , pmoA) support the interpretation of isotopic data. Notably, 16S rRNA gene sequences of macrofauna, including macrofaunal guts, are highly divergent from those in tubes or sediments. Many macrofaunal specimens are dominated by a single 16S rRNA phylotype of Fusobacteria, α -, β -, γ -, or ε -Proteobacteria, Bacteroidetes, or Parcubacteria. This raises the question of whether dominant lake macrofauna live in so far uncharacterized relationships with detrital organic-matter-degrading bacterial endosymbionts. [ABSTRACT FROM AUTHOR]

In the Maritime Alps (NW Italy - SE France), the Middle Triassic-Berriasian platform carbonates of the Provençal Domain are locally affected by an intense hydrothermal dolomitization. This dolomitization resulted from a large-scale hydrothermal circulation related to deep-rooted faults, and is indirect evidence of a significant earliest Cretaceous fault activity in this part of the Alpine Tethys European palaeomargin. New carbonate U-Pb dating and geochemical (stable isotope and noble gases on inclusion-hosted water, 87Sr/86Sr, clumped isotopes) data allowed a better understanding of the timing and mechanisms of the hydrothermal circulation. Hydrothermal fluids probably originated from seawater, which was involved in a deep circulation within the underlying crystalline basement, undergoing heating to more than 200°C and substantial compositional modification by prolonged interaction with basement rocks. Thin cement rims rich in carbonaceous material, locally alternated with hydrothermal dolomite cements, are interpreted as remnants of ephemeral microbial communities that could colonize the upper part of hydrothermal conduits during periods of reduced hot fluid flow and contemporaneous downward seawater infiltration. [ABSTRACT FROM AUTHOR]

Mountains are among the most sensitive ecosystems to climate change, and one of the most evident signs of climate-related effect is the continuous net loss of ice from the cryosphere. Several studies showed that meltwater from glaciated and perennially frozen areas can profoundly affect alpine aquatic ecosystems. Here, we present the impressive temporal increase in solutes in Lake Leit, a mountain lake in the Central Alps that is impacted by an active rock glacier. During the last 30 years, concentrations of sulfate and base cations increased by factors of 4 and 3, respectively. Atmospheric deposition, the only catchment external source, could be excluded as possible cause. The inlets have sulfate and base cations concentrations that were up to double the concentrations of the lake outlet confirming the presence of catchment internal sources. The highest concentrations were measured in the springs at the bottom of the rock glacier. Ground surface temperatures of the rock glacier indicated a high probability of permafrost occurrence, while the annual mean air temperature after the mid-1980s showed continuously positive deviations from the long-term average values (period 1961–1990) with increasing values after 2010. δ34S of sulfate in the inlets and the outflow indicated that sulfate in Lake Leit mainly derived from dissolution of gypsum/anhydrite even if its presence is not confirmed by the Geologic Atlas of Switzerland. Because of these results, we postulate the presence of subsurface traces of sulfate-bearing evaporites, probably associated with Triassic metasediments. These deposits are very common in the closer surroundings. We further hypothesize that the thawing of permafrost affects the flow path of water enabling its contact with fresh highly weatherable minerals increasing the overall weathering rate and shifting the relative ionic composition in the discharge toward the ions that originate from the most soluble minerals. This study shows that increased permafrost thawing in the future can influence water quality in high-alpine settings. [ABSTRACT FROM AUTHOR]

The success of geological carbon storage depends on the assurance of permanent containment for injected carbon dioxide (CO 2) in the storage formation at depth. One of the critical elements of the safekeeping of CO 2 is the sealing capacity of the caprock overlying the storage formation despite faults and/or fractures, which may occur in it. In this work, we present an ongoing injection experiment performed in a fault hosted in clay at the Mont Terri underground rock laboratory (NW Switzerland). The experiment aims to improve our understanding of the main physical and chemical mechanisms controlling (i) the migration of CO 2 through a fault damage zone, (ii) the interaction of the CO 2 with the neighboring intact rock, and (iii) the impact of the injection on the transmissivity in the fault. To this end, we inject CO 2 -saturated saline water in the top of a 3 m thick fault in the Opalinus Clay, a clay formation that is a good analog of common caprock for CO 2 storage at depth. The mobility of the CO 2 within the fault is studied at the decameter scale by using a comprehensive monitoring system. Our experiment aims to close the knowledge gap between laboratory and reservoir scales. Therefore, an important aspect of the experiment is the decameter scale and the prolonged duration of observations over many months. We collect observations and data from a wide range of monitoring systems, such as a seismic network, pressure temperature and electrical conductivity sensors, fiber optics, extensometers, and an in situ mass spectrometer for dissolved gas monitoring. The observations are complemented by laboratory data on collected fluids and rock samples. Here we show the details of the experimental concept and installed instrumentation, as well as the first results of the preliminary characterization. An analysis of borehole logging allows for identifying potential hydraulic transmissive structures within the fault zone. A preliminary analysis of the injection tests helped estimate the transmissivity of such structures within the fault zone and the pressure required to mechanically open such features. The preliminary tests did not record any induced microseismic events. Active seismic tomography enabled sharp imaging the fault zone. [ABSTRACT FROM AUTHOR]

Foreland fold-and-thrust belts record long-lived tectonic-sedimentary activity, from passive margin sedimentation, flexuring, and further involvement into wedge accretion ahead of an advancing orogen. Therefore, dating fault activity is fundamental for plate movement reconstruction, resource exploration, or earthquake hazard assessment. Here, we report U-Pb ages of syntectonic calcite mineralizations from four thrusts and three tear faults sampled, at the regional scale, across the Jura fold-and-thrust belt in the northwestern Alpine foreland (eastern France). Four regional tectonic phases are recognized in the middle Eocene-middle Pleistocene interval: (1) pre-orogenic faulting at 44.7 ± 2.6 and 48.4 ± 1.5 Ma associated to the uplift of the Alpine forebulge, (2) syn-orogenic thrusting at 11.4 ± 1.1, 10.6 ± 0.5, 9.7 ± 1.4, 9.6 ± 0.3, and 7.5 ± 1.1 Ma associated to possible in-sequence thrust propagation, and (3) syn-orogenic tear faulting at 10.5 ± 0.4, 9.1 ± 6.5, 7.3 ± 1.9, 5.7 ± 4.7, 4.8 ± 1.7, and at 0.7 ± 4.2 Ma including the reactivation of a pre-orogenic fault as tear fault at 3.9 ± 2.9 Ma. Previously unknown faulting events at 44.7 ± 2.6 and 48.4 ± 1.5 Ma predate by ~ 10 Ma the accepted late Eocene age for tectonic activity onset in the Alpine foreland. In addition, we dated the previously inferred strike-slip faults re-activation as tear fault. The U-Pb ages demonstrate the long-lived tectonic history at the plate boundary between European and African plates and that the deformation observed in the foreland is directly linked to continental collision. [ABSTRACT FROM AUTHOR]

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The middle Miocene climate transition (MMCT, ~14.5-13.0 Ma) was associated with a significant expansion of Antarctic ice, but the mechanisms triggering the event remain enigmatic. We present a new clumped isotope (Δ47) bottom water temperature (BWT) record from 16.0 Ma to 12.2 Ma from Ocean Drilling Program (ODP) Site 747 in the Southern Ocean, and compare it to existing BWT records. We show that BWTs in the Southern Ocean were ~8-10 °C during the middle Miocene greenhouse, and thus considerably warmer than today. Nonetheless, bottom water d18O (calculated from foraminiferal β18O and Δ47) suggests substantial amounts of land ice throughout the interval of the study. Our dataset demonstrates that BWTs at Site 747 decreased by ~3-5 °C across the MMCT. This cooling preceded the stepped main increase in global ice volume, and appears to have been followed by a transient bottom water warming starting during or slightly after the main ice volume increase. We speculate that a regional freshening of the upper water column at this time may have increased stratification and reduced bottom water heat loss to the atmosphere, counteracting global cooling in the bottom waters of the Southern Ocean and possibly even at larger scales. Additional processes and feedbacks required for substantial ice growth may have contributed to the observed decoupling of Southern Ocean BWT and global ice volume. [ABSTRACT FROM AUTHOR]

Previous studies have shown that microbially produced methane can be a dominant carbon source of lacustrine sedimentary macrofauna in eutrophic lakes, most likely through grazing on methane-oxidizing bacteria. Here we investigate the contributions of different carbon sources to macrofaunal biomass across five lakes in central Switzerland that range from oligotrophic to highly eutrophic. Macrofaunal communities change with trophic state, with chironomid larvae dominating oligotrophic and tubificid oligochaetes dominating eutrophic lake sediments. 13C-isotopic data suggest that the average contribution of methane-derived carbon to the biomass of both macrofaunal groups is similar, but consistently remains minor, ranging from only ~1% in the oligotrophic lake to at most 12% in the eutrophic lakes. The remaining biomass can be explained with assimilation of detritus-derived organic carbon. Low abundances of methane cycling microorganisms in macrofaunal specimens, burrows, and surrounding sediment based on 16S ribosomal RNA (rRNA) gene sequences and copy numbers of genes involved in anaerobic and aerobic methane cycling (mcrA, pmoA) support the interpretation of isotopic data. Notably, 16S rRNA gene sequences of macrofauna, including macrofaunal guts, are highly divergent from those in tubes or sediments. Many macrofaunal specimens are dominated by a single 16S rRNA phylotype of 'Fusobacteria, α-, β-, γ-, or ε-Proteobacteria, Bacteroidetes, or Parcubacteria. This raises the question whether dominant lake macrofauna live in so far uncharacterized relationships with detrital organic matter-degrading bacterial endosymbionts. [ABSTRACT FROM AUTHOR]

Rationale: Unravelling the biogeochemical cycle of the potent greenhouse gas nitrous oxide (N2O) is an underdetermined problem in environmental sciences due to the multiple source and sink processes involved, which complicate mitigation of its emissions. Measuring the doubly isotopically substituted molecules (isotopocules) of N2O can add new opportunities to fingerprint and constrain its cycle. Methods: We present a laser spectroscopic technique to selectively and simultaneously measure the eight most abundant isotopocules of N2O, including three doubly substituted species – so called “clumped isotopes”. For the absolute quantification of individual isotopocule abundances, we propose a new calibration scheme that combines thermal equilibration of a working standard gas with a direct mole fraction‐based approach. Results: The method is validated for a large range of isotopic composition values by comparison with other established methods (laser spectroscopy using conventional isotopic scale and isotope ratio mass spectrometry). Direct intercomparison with recently developed ultrahigh‐resolution mass spectrometry shows clearly the advantages of the new laser technique, especially with respect to site specificity of isotopic substitution in the N2O molecule. Conclusions: Our study represents a new methodological basis for the measurements of both singly substituted and clumped N2O isotopes. It has a high potential to stimulate future research in the N2O community by establishing a new class of reservoir‐insensitive tracers and molecular‐scale insights. [ABSTRACT FROM AUTHOR]

We propose a non-local, meso-scale approach for coupling multiphysics processes across scale. The physics is based on discrete phenomena, triggered by local Thermo-Hydro-Mechano-Chemical (THMC) instabilities, that cause cross-diffusion (quasi-soliton) acceleration waves. These waves nucleate when the overall stress field is incompatible with accelerations from local feedbacks of generalized THMC thermodynamic forces that trigger generalized thermodynamic fluxes of another kind. Cross-diffusion terms in the 4 x 4 THMC diffusion matrix are shown to lead to multiple diffusional P- and S-wave equations as coupled THMC solutions. Uncertainties in the location of meso-scale material instabilities are captured by a wave-scale correlation of probability amplitudes. Cross-diffusional waves have unusual dispersion patterns and, although they assume a solitary state, do not behave like solitons but show complex interactions when they collide. Their characteristic wavenumber and constant speed define mesoscopic internal material time-space relations entirely defined by the coefficients of the coupled THMC reaction-cross-diffusion equations. For extreme conditions, cross-diffusion waves can lead to an energy cascade connecting large and small-scales and cause solid-state turbulence. [ABSTRACT FROM AUTHOR]

The Middle Pleistocene Transition (MPT, ~641–920 ka) represents a period of the Quaternary climate when, in the absence of substantial changes in orbital forcing, the climate progressively shifted to the 100 ka asymmetrical glacial–interglacial cyclicity characterizing the current climate. The causes of this change remain still uncertain but several lines of evidence suggested the carbon storage of the deep ocean played a relevant role. Here we evaluate the contribution of the eastern deep tropical Pacific to the global ocean carbon sequestration and storage between 760 and 1,040 ka. We present multi‐proxy records for export production and the redox environment at the seabed from Ocean Drilling Program Site 1242 located in the deep East Equatorial Pacific. Our data indicate the development of suboxic bottom waters during early marine isotopic stage (MIS) 23 and glacial MIS 22, suggesting the capture and storage of respired carbon. Redox‐sensitive elements suggest the progressive oxygenation of the deep ocean initiated at the end of the glacial MIS 22, continued across deglaciation and ended with the accomplishment of full interglacial MIS 21. We describe this pattern as a "less complete deglacial ventilation" in that it differs from the mid‐late Pleistocene Pacific deep ocean ventilation pattern which occurs during deglaciations. The ventilation of the deep Pacific Ocean extending beyond deglaciation might have contributed to a persistent deep ocean carbon sequestration, which might have resulted in lowered atmospheric CO2 values that could have influenced the internal response of the climate system contributing to the development of the 100 ka climate variability. Key Points: Storage of respired carbon in the east equatorial Pacific from interglacial MIS 23 to glacial MIS 22Ventilation of the deep sea and inferred atmospheric CO2 release extended from the end of glacial MIS 22 to full interglacial MIS 21 [ABSTRACT FROM AUTHOR]

This paper investigates the hydrothermal fluid circulation that was linked to the extensional evolution of the Adriatic rifted margin during the Jurassic opening of the Alpine Tethys. Remnants of this rifted margin are spectacularly preserved in SE Switzerland and N Italy. Five study areas were chosen ranging from the former proximal to the most distal part of the margin. We demonstrate an intimate link between Jurassic extensional tectonics and fluid activity affecting the pre‐ to early post‐rift sedimentary sequences. Nature, composition and origin of fluids are constrained by a multidisciplinary approach based on field observations and including geochemical (O‐C, Sr, He isotopes, U‐Pb datings, fluid inclusion microthermometry) and petrological methods. Several fluid‐related diagenetic products and processes such as dolomitization, veining, hydraulic brecciation, and silicification can be recognized. It appears that different paleogeographic settings and different stratigraphic levels document distinct phases of fluid activity. The fluids reached temperatures of up to 150°C near paleo‐seafloor. They were enriched in 18O, had high 87Sr/86Sr and low 3He/4He ratios, documenting a strong interaction between seawater and a granitic basement. Many lines of evidence point to the occurrence of over‐pressured fluids and long‐lasting fluid circulation due to fault‐valve mechanisms and high thermal gradients. Two main stages with different fluid chemistry can be recognized: (1) a carbonate‐rich stage that developed during the stretching phases and was linked to high‐angle normal faulting, and (2) a silica‐rich stage occurring during late rift exhumation of crustal and mantle rocks in the distal domains in the presence of detachment faults and high thermal gradients. This paper provides, for the first time, a large and robust characterization of fluid–rock interactions occurring during rifting along an almost complete section across a magma‐poor rifted margin. [ABSTRACT FROM AUTHOR]

Even though human-induced eutrophication has severely impacted temperate lake ecosystems over the last centuries, the effects on total organic carbon (TOC) burial and mineralization are not well understood. We study these effects based on sedimentary records from the last 180 years in five Swiss lakes that differ in trophic state. We compare changes in TOC content and modeled TOC accumulation rates through time to historical data on algae blooms, water column anoxia, wastewater treatment, artificial lake ventilation, and water column phosphorus (P) concentrations. We furthermore investigate the effects of eutrophication on rates of microbial TOC mineralization and vertical distributions of microbial respiration reactions in sediments. Our results indicate that the history of eutrophication is well recorded in the sedimentary record. Overall, eutrophic lakes have higher TOC burial and accumulation rates, and subsurface peaks in TOC coincide with past periods of elevated P concentrations in lake water. Sediments of eutrophic lakes, moreover, have higher rates of total respiration and higher contributions of methanogenesis to total respiration. However, we found strong overlaps in the distributions of respiration reactions involving different electron acceptors in all lakes regardless of lake trophic state. Moreover, even though water column P concentrations have been reduced by ∼ 50 %–90 % since the period of peak eutrophication in the 1970s, TOC burial and accumulation rates have only decreased significantly, by ∼ 20 % and 25 %, in two of the five lakes. Hereby there is no clear relationship between the magnitude of the P concentration decrease and the change in TOC burial and accumulation rate. Instead, data from one eutrophic lake suggest that artificial ventilation, which has been used to prevent water column anoxia in this lake for 35 years, may help sustain high rates of TOC burial and accumulation in sediments despite water column P concentrations being strongly reduced. Our study provides novel insights into the influence of human activities in lakes and lake watersheds on lake sediments as carbon sinks and habitats for diverse microbial respiration processes. [ABSTRACT FROM AUTHOR]

In this study, we investigated the application and the transferability of the Soil Water and Assessment Tool (SWAT) in a partly glacierized Alpine catchment characterized by extreme climatic conditions and steep terrain. The model was initially calibrated for the 10 km 2 watershed of the Damma glacier Critical Zone Observatory (CZO) in central Switzerland using monitoring data for the period of 2009–2011 and then was evaluated for 2012–2013 in the same area. Model performance was found to be satisfactory against both the Nash–Sutcliffe criterion (NS) and a benchmark efficiency (BE). The transferability of the model was assessed by using the parameters calibrated on the small watershed and applying the model to the approximately 100 km 2 catchment that drains into the hydropower reservoir of the Göscheneralpsee and includes the Damma glacier CZO. Model results were compared to the reservoir inflow data from 1997 to 2010 and it was found that the model predicted successfully snowmelt timing and autumn recession but could not accurately capture the peak flow for certain years. Runoff was slightly overestimated from late May to June, when it is dominated by snowmelt. Finally, we investigated the response of the greater catchment to climate change using three different climate change scenarios, and the results were compared to those of a previous study, where two different hydrological models, PREVAH and ALPINE3D, were used. The methodology presented here, where SWAT is calibrated for a small watershed and then applied for a bigger area with similar climatic conditions and geographical characteristics, could work even under extreme conditions like ours. However, greater attention should be given to the differences between glacier melt and snowmelt dynamics. In conclusion, this assessment test on the transferability of SWAT on different scales gave valuable information about the strengths and weaknesses of the model when it was applied under conditions different to those under which it was calibrated. [ABSTRACT FROM AUTHOR]

Serpentinitic systems are potential habitats for microbial life due to frequently high concentrations of microbial energy substrates, such as hydrogen (H2), methane (CH4), and short-chain organic acids (SCOAs). Yet, many serpentinitic systems are also physiologically challenging environments due to highly alkaline conditions (pH > 10) and elevated temperatures (>80°C). To elucidate the possibility of microbial life in deep serpentinitic crustal environments, International Ocean Discovery Program (IODP) Expedition 366 drilled into the Yinazao, Fantangisña, and Asùt Tesoru serpentinite mud volcanoes on the Mariana Forearc. These mud volcanoes differ in temperature (80, 150, 250°C, respectively) of the underlying subducting slab, and in the porewater pH (11.0, 11.2, 12.5, respectively) of the serpentinite mud. Increases in formate and acetate concentrations across the three mud volcanoes, which are positively correlated with temperature in the subducting slab and coincide with strong increases in H2 concentrations, indicate a serpentinization-related origin. Thermodynamic calculations suggest that formate is produced by equilibrium reactions with dissolved inorganic carbon (DIC) + H2, and that equilibration continues during fluid ascent at temperatures below 80°C. By contrast, the mechanism(s) of acetate production are not clear. Besides formate, acetate, and H2 data, we present concentrations of other SCOAs, methane, carbon monoxide, and sulfate, δ13C-data on bulk carbon pools, and microbial cell counts. Even though calculations indicate a wide range of microbial catabolic reactions to be thermodynamically favorable, concentration profiles of potential energy substrates, and very low cell numbers suggest that microbial life is scarce or absent. We discuss the potential roles of temperature, pH, pressure, and dispersal in limiting the occurrence of microbial life in deep serpentinitic environments. [ABSTRACT FROM AUTHOR]

The geochemical conditions conducive to dolomite formation in shallow evaporitic environments along the Triassic Tethyan margin are still poorly understood. Large parts of the Triassic dolomites in the Austroalpine and the southern Alpine realm are affected by late diagenetic or hydrothermal overprinting, but recent studies from the Carnian Travenanzes Formation (southern Alps) provide evidence of primary dolomite. Here a petrographic and geochemical study of dolomites intercalated in a 100 m thick Carnian sequence of distal alluvial plain deposits is presented to gain better insight into the conditions and processes of dolomite formation. The dolomites occur as 10 to 50 cm thick homogeneous beds, millimetre-scale laminated beds, and nodules associated with palaeosols. The dolomite is nearly stoichiometric with slightly attenuated ordering reflections. Sedimentary structures indicate that the initial primary dolomite or precursor phase consisted largely of unlithified mud. Strontium isotope ratios (87Sr/86Sr) of homogeneous and laminated dolomites reflect Triassic seawater composition, suggesting precipitation in evaporating seawater in a coastal ephemeral lake or sabkha system. However, the setting differed from modern sabkha or coastal ephemeral lake systems by being exposed to seasonally wet conditions with significant siliciclastic input and the inhibition of significant lateral groundwater flow by impermeable clay deposits. Thus, the ancient Tethyan margin was different from modern analogues of primary dolomite formation. [ABSTRACT FROM AUTHOR]

Obtaining absolute temperatures of the ocean in deep time is complicated by the lack of constraints on seawater chemistry. Seawater salinity, carbonate ion concentration, δ18O, and elemental abundance changes may obscure widely applied paleoproxies. In addition, with foraminifera‐based proxies applied over long time scales or through major transitions, taxonomic turnover can impair the robustness of a record. While requiring larger sample sizes than most other proxies, the clumped isotope method is independent of seawater chemistry. Here we test if small benthic foraminifera precipitate their carbonate in equilibrium with respect to the clumped isotope thermometer and if there are any species‐specific vital effects. We find that benthic foraminifera fall on the same calibration line as the majority of carbonate minerals including inorganic calcite. In addition, we find no offsets that can be attributed to a species‐specific for any of the samples. This finding implies that a necessary amount of sample material can be obtained by aggregating over multiple taxa of benthic foraminifera and allows for the application of this proxy over major climatic transitions that coincide with seawater chemistry changes and foraminifera extinctions. Key Points: There are no vital effect offsets of benthic foraminifera from abiogenic carbonate materials for clumped isotope temperature proxyThere are no discernible species‐specific offsets for benthic foraminiferaThe clumped isotope proxy is robust through deep time for paleoceanographic reconstructions [ABSTRACT FROM AUTHOR]

Even though human induced eutrophication has severely impacted temperate lake ecosystems over the last centuries, the effects on total organic carbon (TOC) burial and mineralization are not well understood. We study these effects based on sedimentary records from the last 180 years in five Swiss lakes that differ in trophic state. We compare changes in content of TOC and modeled TOC accumulation rates through time to historical data on algae blooms, water column anoxia, wastewater treatment, artificial lake ventilation, and water column phosphorus (P) concentrations. We furthermore investigate the effects of eutrophication on rates of microbial TOC remineralization and vertical distributions of microbial respiration reactions in sediments. Our results indicate that the history of eutrophication is well reflected in the sedimentary record. Subsurface peaks in sedimentary TOC coincide with past periods of elevated P concentrations in lake water. Sediments of eutrophic lakes show overall higher rates of microbial respiration, and a higher relative contribution of methanogenesis to total respiration. Yet, a clear impact of lake trophic state on the zonation of microbial respiration reactions is absent. Moreover, even though water column P concentrations have been reduced by ~ 80 % (range: ~ 50–90 %) since the period of peak eutrophication in the 1970s, TOC burial and accumulation rates have only decreased significantly (~ 20 and 25 %) in two of the five lakes. Hereby we found no clear relationship between the magnitude of the decrease in P concentrations and the change in TOC burial and accumulation rate. Instead, artificial lake ventilation, which is used to prevent water column anoxia in eutrophic lakes, may help sustain high rates of TOC burial and accumulation in sediments despite strongly reduced water column P concentrations. Our results provide novel insights into how eutrophication and eutrophication management practices affect organic carbon burial and the distribution of microbial respiration reactions in temperate lakes. These insights are important to understanding how anthropogenic activities affect the size of the carbon pool that is stored globally in lacustrine sediments. [ABSTRACT FROM AUTHOR]

This study identifies temporal biases in the radiocarbon ages of the planktonic foraminifera species Globigerina bulloides and Globigerinoides ruber (white) in a sediment core from the SW Iberian margin (so‐called Shackleton site). Leaching of the outer shell and measurement of the radiocarbon content of both the leachate and leached sample enabled us to identify surface contamination of the tests and its impact on their 14C ages. Incorporation of younger radiocarbon on the outer shell affected both species and had a larger impact downcore. Interspecies comparison of the 14C ages of the leached samples reveal systematic offsets with 14C ages for G. ruber being younger than G. bulloides ages during the last deglaciation and part of the Early and mid‐Holocene. The greatest offsets (up to 1,030 years) were found during Heinrich Stadial 1, the Younger Dryas, and part of the Holocene. The potential factors differentially affecting these two planktonic species were assessed by complementary 14C, oxygen and carbon isotopes, and species abundance determinations. The coupled effect of bioturbation with changes in the abundance of G. ruber is invoked to account for the large age offsets. Our results highlight that 14C ages of planktonic foraminifera might be largely compromised even in settings characterized by high sediment accumulation rates. Thus, a careful assessment of potential temporal biases must be performed prior to using 14C ages for paleoclimate investigations or radiocarbon calibrations (e.g., marine calibration curve Marine13, Reimer et al., 2013, https://doi.org/10.2458/azu_js_rc.55.16947). Key Points: Leaching of the outer shell is a powerful diagnostic for external subtle contamination and an effective tool to obtain more reliable radiocarbon datesCo‐occurring planktonic foraminifera species sampled across abrupt climatic events show radiocarbon age offsets of up to 1,030 yearsDifferential bioturbation coupled with species abundance changes is invoked to explain such temporal discrepancies [ABSTRACT FROM AUTHOR]

Seepage of methane (CH4) on land and in the sea may significantly affect Earth’s biogeochemical cycles. However processes of CH4 generation and consumption, both abiotic and microbial, are not always clear. We provide new geochemical and isotope data to evaluate if a recently discovered CH4 seepage from the shallow seafloor close to the Island of Elba (Tuscany) and two small islands nearby are derived from abiogenic or biogenic sources and whether carbonate encrusted vents are the result of microbial or abiotic processes. Emission of gas bubbles (predominantly CH4) from unlithified sands was observed at seven spots in an area of 100 m2 at Pomonte (Island of Elba), with a total rate of 234 ml m-2 d-1. The measured carbon isotope values of CH4 of around -18‰ (VPDB) in combination with the measured δ2H value of -120‰ (VSMOW) and the inverse correlation of δ13C-value with carbon number of hydrocarbon gases are characteristic for sites of CH4 formation through abiogenic processes, specifically abiogenic formation of CH4 via reduction of CO2 by H2. The H2 for methanogenesis likely derives from ophiolitic host rock within the Ligurian accretionary prism. The lack of hydrothermal activity allows CH4 gas to become decoupled from the stagnant aqueous phase. Hence no hyperalkaline fluid is currently released at the vent sites. Within the seep area a decrease in porewater sulphate concentrations by ca. 5 mmol/l relative to seawater and a concomitant increase in sulphide and dissolved inorganic carbon (DIC) indicate substantial activity of sulphate-dependent anaerobic oxidation of methane (AOM). In absence of any other dissimilatory pathway, the δ13C-values between -17 and -5‰ in dissolved inorganic carbon and aragonite cements suggest that the inorganic carbon is largely derived from CH4. The formation of seep carbonates is thus microbially induced via anaerobic oxidation of abiotic CH4. [ABSTRACT FROM AUTHOR]

The Triassic-Jurassic boundary is characterized by strong perturbations of the global carbon cycle, triggered by massive volcanic eruptions related to the onset of the Central Atlantic Magmatic Province. These perturbations are recorded by negative carbon isotope excursions (CIEs) which have been reported worldwide. In this study, Triassic-Jurassic boundary sections from the southern margin of the Central European Basin (CEB) located in northern Switzerland are analyzed for organic carbon and nitrogen isotopes in combination with particulate organic matter (POM) analyses. We reconstruct the evolution of the depositional environment from Late Triassic to Early Jurassic in northern Switzerland and show that observed negative shifts in δ13C of the total organic carbon (δ13CTOC) in the sediment are only subordinately influenced by varying organic matter (OM) composition and primarily reflect global changes in the carbon cycle. Based on palynology and the stratigraphic positions of isotopic shifts, the δ13CTOC record of the studied sections is correlated with the GSSP section at Kuhjoch (Tethyan realm) in Austria and with the St. Audrie’s Bay section (CEB realm) in southwest England. We also show that in contrast to POM analyses the applicability of organic carbon/total nitrogen (OC/TN) atomic ratios and stable isotopes of total nitrogen (δ15NTN) for detecting changes in source of OM is limited in marginal depositional environments with frequent changes in lithology and OM contents. [ABSTRACT FROM AUTHOR]

In this study, we investigated the application of the Soil Water and Assessment Tool (SWAT) for the simulation of runoff in the partly glacierised watershed of the Damma glacier Critical Zone Observatory (CZO), Switzerland. The model was calibrated using daily time steps for the period of 2009-2011, while two different approaches were used for its validation. Initially the model was validated using daily data for the years 2012-2013. Subsequently, the calibrated version of the model was applied on the greater area that drains to the hydropower reservoir of the Göscheneralpsee and includes the Damma glacier watershed, using inflow data. This validation approach can help in assessing model uncertainty under changing land use and climate forcing. Model performance was evaluated both visually and statistically and it was found that even though SWAT has rarely been used in high alpine and glacierised areas and despite the complexity of simulating the extreme conditions of Damma glacier watershed; its performance was very satisfactory. Our novel validation approach proved to be successful since the performance of the model was similarly good when applied for the greater catchment feeding Göscheneralpsee. Finally, we investigated the response of the two regions, Damma glacier and its greater area, to climate change using SWAT and results were compared to a previous study using the models PREVAH and ALPINE 3D. It confirmed that SWAT can predict changes in future runoff and peak flow in alpine areas with the same accuracy as more demanding models such as ALPINE 3D and PREVAH. This study demonstrates the applicability of SWAT in high elevation, snow and glacier dominated watersheds and in quantifying the effects of climate change on water resources. [ABSTRACT FROM AUTHOR]