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  • 101.
    Bohlin, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Point source influences on the carbon and nitrogen geochemistry of sediments in the Stockholm inner archipelago, Sweden2006In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 366, no 1, p. 337-349Article in journal (Refereed)
    Abstract [en]

    This study reports analyses of carbon and nitrogen content, and δ15N and δ13C in sediments of the Höggarnsfjärden Bay near Stockholm. Samples have been taken upstream, near, and downstream of a point source of processed leach water from a garbage dump. The surface sediment at the upstream and downstream sites has δ15N and δ13C close to the expected background of the area, even though a contribution from the leach water can be observed downstream of the point source. The sediment close to the outflow is strongly influenced by the carbon and nitrogen in the leach water.

  • 102. Bolhar, R.
    et al.
    Ring, Uwe
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ireland, T. R.
    Zircon in amphibolites from Naxos, Aegean Sea, Greece: origin, significance and tectonic setting2017In: Journal of Metamorphic Geology, ISSN 0263-4929, E-ISSN 1525-1314, Vol. 35, no 4, p. 413-434Article in journal (Refereed)
    Abstract [en]

    We report U-Pb zircon ages of c. 700-550Ma, 262-220Ma, 47-38Ma and 15-14Ma from amphibolites on Naxos Island in the Aegean extensional province of Greece. The zircon has complex internal structures. Based on cathodoluminescence response, zoning and crosscutting relationships a minimum of four zircon growth stages are identified: inherited core, magmatic core, inner metamorphic (?) rim and an outer metamorphic rim. Trace element compositions of the amphibolites suggest igneous differentiation and crustal assimilation. Zircon solubility as a function of saturation temperatures, Zr content and melt composition indicates that the zircon did not originally crystallize in the mafic bodies but was inherited from felsic precursor rocks, and subsequently assimilated into the mafic intrusives during emplacement. Zircon inheritance is corroborated by the complex, xenocrystic nature of the zircon in one sample. Ages of c. 700-550Ma and 262-220Ma are assigned to inherited zircon. Available geochemical data suggest that the 15-14Ma metamorphic rims grew insitu in the amphibolites, corresponding to a high-grade metamorphic event at this time. However, the geochemical data cannot conclusively establish if the c. 40Ma zircon rims also grew insitu, or whether they were inherited along with the xenocrystic cores. Two scenarios for emplacement of the mafic intrusives are discussed: (i) Intrusion during late-Triassic to Jurassic ocean basin development of the Aegean realm, in which case the 40Ma zircon rims would have grown insitu, and (ii) emplacement in the Miocene as a result mafic underplating during large-scale extension. In this case, only the 15-14Ma metamorphic outer rims would have formed insitu in the amphibolitic host rocks.

  • 103.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Benthic metabolism and sediment nitrogen cycling in Baltic sea coastal areas: the role of eutrophication, hypoxia and bioturbation2012Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Eutrophication is one of the greatest threats for the Baltic Sea, and one of its more critical consequences is bottom water hypoxia. Nutrient enrichment and oxygen-depletion affect both the deep central basins and a number of coastal areas, even though strategies for nutrient reduction have lately been implemented. In order to better understand why those threats are expanding and formulate more effective remediation strategies two main achievements are needed: (1) new data on benthic nutrient dynamics should be available in order to develop updated budgets for sensitive Baltic areas; (2) the main transformation processes and their regulation mechanisms (i.e. oxygen availability, presence of macrofauna, different organic loading scenarios) should be better constrained.

    Paper I was able to demonstrate that re-oxygenation of previously anoxic sediment has a positive effect on the ecosystem because of better retention of nutrients and efficient conversion of fixed nitrogen to nitrogen gas. Sediment colonization by the invasive genus Marenzelleria counteracts some of the positive aspects provided by benthic oxygenation (in particular, nutrient retention, N2 loss). A possible explanation for this reversal can be that Marenzelleria does stimulate anaerobic more that aerobic metabolism.

    Results from Paper II suggest that at the outermost stations of Himmerfjärden denitrification follows a pronounced seasonal pattern, primarily regulated by bottom water temperatures. At the innermost and impacted site oxygen level in the bottom water varies considerably during the year and causes denitrification/DNRA predominance to be the main nitrate reduction pathway. On an annual scale, the net amount of lost N2 is comparable at the four sampling sites and accounts for 96% of the total DIN discharged from the sewage treatment plant, suggesting that denitrification in the estuarine sediment acts as a major nitrogen sink for external N inputs.

  • 104.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Control factors of the marine nitrogen cycle: The role of meiofauna, macrofauna, oxygen and aggregates2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The ocean is the most extended biome present on our planet. Recent decades have seen a dramatic increase in the number and gravity of threats impacting the ocean, including discharge of pollutants, cultural eutrophication and spread of alien species. It is essential therefore to understand how different impacts may affect the marine realm, its life forms and biogeochemical cycles. The marine nitrogen cycle is of particular importance because nitrogen is the limiting factor in the ocean and a better understanding of its reaction mechanisms and regulation is indispensable. Furthermore, new nitrogen pathways have continuously been described. The scope of this project was to better constrain cause-effect mechanisms of microbially mediated nitrogen pathways, and how these can be affected by biotic and abiotic factors.

    This thesis demonstrates that meiofauna, the most abundant animal group inhabiting the world’s seafloors, considerably alters nitrogen cycling by enhancing nitrogen loss from the system. In contrast, larger fauna such as the polychaete Marenzelleria spp. enhance nitrogen retention, when they invade eutrophic Baltic Sea sediments. Sediment anoxia, caused by nutrient excess, has negative consequences for ecosystem processes such as nitrogen removal because it stops nitrification, which in turn limits both denitrification and anammox. This was the case of Himmerfjärden and Byfjord, two estuarine systems affected by anthropogenic activities, such as treated sewage discharges. When Byfjord was artificially oxygenated, nitrate reduction mechanisms started just one month after pumping. However, the balance between denitrification and nitrate ammonification did not favor either nitrogen removal or its retention.

    Anoxia is also present in aggregates of the filamentous cyanobacteria Nodularia spumigena. This thesis shows that even in fully oxic waters, millimetric aggregates can host anaerobic nitrogen processes, with clear implications for the pelagic compartment. While the thesis contributed to our knowledge on marine nitrogen cycling, more data need to be collected and experiments performed in order to understand key processes and regulation mechanisms of element cycles in the ocean. In this way, stakeholders may follow and take decisions in order to limit the continuous flow of human metabolites and impacts on the marine environment.

  • 105.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bartoli, Marco
    Gunnarsson, Jonas S.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Rahm, Lars
    Raymond, Caroline
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Svensson, Ola
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Shakeri Yekta, Sepehr
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Effect of reoxygenation and Marenzelleria spp. bioturbation on Baltic Sea sediment metabolism2013In: Marine Ecology Progress Series, ISSN 0171-8630, E-ISSN 1616-1599, Vol. 482, p. 43-55Article in journal (Refereed)
    Abstract [en]

    Nutrient reduction and the improvement of bottom water oxygen concentrations are thought to be key factors in the recovery of eutrophic aquatic ecosystems. The effects of reoxygenation and bioturbation of natural hypoxic sediments in the Baltic Sea were studied using a mesocosm experiment. Anoxic sediment box cores were collected from 100 m depth in Kanholmsfjärden (Stockholm Archipelago) and maintained in flow-through mesocosms with 3 treatments: (1) hypoxic: supplied with hypoxic water; (2) normoxic: supplied with oxic water; and (3) Marenzelleria: supplied with oxic water and the polychaete Marenzelleria spp. (2000 ind. m–2). After a 7 wk long conditioning period, net fluxes of dissolved O2, CH4, Fe2+, Mn2+, NH4+, NO2-, NO3-, PO43- and H4SiO4, and rates of nitrate ammonification (DNRA), denitrification and anammox were determined. Phosphate was taken up by the sediment in all treatments, and the uptake was highest in the normoxic treatment with Marenzelleria. Normoxic conditions stimulated the denitrification rate by a factor of 5. Denitrification efficiency was highest under normoxia (50%), intermediate in bioturbated sediments (16%), and very low in hypoxic sediments (4%). The shift from hypoxic to normoxic conditions resulted in a significantly higher retention of NH4+, H4SiO4 and Mn2+ in the sediment, but the bioturbation by Marenzelleria reversed this effect. Results from our study suggest that bioturbation by Marenzelleria stimulates the exchange of solutes between sediment and bottom water through irrigation and enhances bacterial sulfate reduction in the burrow walls. The latter may have a toxic effect on nitrifying bacteria, which, in turn, suppresses denitrification rates.

  • 106.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Callac, Nolwenn
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Vicenzi, Alessandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chi Fru, Ernest
    Stockholm University, Faculty of Science, Department of Geological Sciences. Cardiff University, UK.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Methane fluxes from coastal sediments are enhanced by macrofauna2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, no 1, article id 13145Article in journal (Refereed)
    Abstract [en]

    Methane and nitrous oxide are potent greenhouse gases (GHGs) that contribute to climate change. Coastal sediments are important GHG producers, but the contribution of macrofauna (benthic invertebrates larger than 1 mm) inhabiting them is currently unknown. Through a combination of trace gas, isotope, and molecular analyses, we studied the direct and indirect contribution of two macrofaunal groups, polychaetes and bivalves, to methane and nitrous oxide fluxes from coastal sediments. Our results indicate that macrofauna increases benthic methane efflux by a factor of up to eight, potentially accounting for an estimated 9.5% of total emissions from the Baltic Sea. Polychaetes indirectly enhance methane efflux through bioturbation, while bivalves have a direct effect on methane release. Bivalves host archaeal methanogenic symbionts carrying out preferentially hydrogenotrophic methanogenesis, as suggested by analysis of methane isotopes. Low temperatures (8 °C) also stimulate production of nitrous oxide, which is consumed by benthic denitrifying bacteria before it reaches the water column. We show that macrofauna contributes to GHG production and that the extent is dependent on lineage. Thus, macrofauna may play an important, but overlooked role in regulating GHG production and exchange in coastal sediment ecosystems.

  • 107.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Deutsch, Barbara
    Bartoli, Marco
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Seasonal benthic nutrient cycling in a Baltic sea estuary2012In: / [ed] The Oceanography Society, American Society of Limnology and Oceanography, American Geophysical Union, 2012Conference paper (Other academic)
    Abstract [en]

    Decades of urban, industrial, and agricultural discharge of nitrogen and phosphorus to the Baltic Sea have contributed to the spreading of water column hypoxia and annual widespread cyanobacteria blooms. Central to mitigating Baltic Sea eutrophication is to resolve how much reduction strategies of external N and P loading are offset by internal loading of the Baltic through nutrient recycling from the sediment. We investigated the seasonal variation of benthic nitrogen and phosphorus cycling in an estuary of the Baltic impacted by decades of sewage discharge. Sediment nutrient fluxes, denitrification, Anammox, DNRA, potential nitrification, and total and diffusive oxygen uptake (TOU/DOU) were quantified with 15N-tracer methods and microsensor profiling. Data indicate benthic net efflux of ammonium and phosphorus during the summer months, decreasing N2 loss with increasing organic matter content, and benthic N/P regeneration with a ratio of 3 to 7 compared to the sewage discharge N/P of ≈ 25, and a significant contribution (6 to 25%) of Anammox to N2 loss. On average benthic denitrification and Anammox may reduce the N load to the estuary by up to 54%.

  • 108.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Bartoli, Marco
    Marchant, Hannah K.
    Bruchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Seasonal oxygen, nitrogen and phosphorus benthic cycling along an impacted Baltic Sea estuary: regulation and spatial patterns2014In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 119, no 1-3, p. 139-160Article in journal (Refereed)
    Abstract [en]

    The regulatory roles of temperature, eutrophication and oxygen availability on benthic nitrogen (N) cycling and the stoichiometry of regenerated nitrogen and phosphorus (P) were explored along a Baltic Sea estuary affected by treated sewage discharge. Rates of sediment denitrification, anammox, dissimilatory nitrate reduction to ammonium (DNRA), nutrient exchange, oxygen (O2) uptake and penetration were measured seasonally. Sediments not affected by the nutrient plume released by the sewage treatment plant (STP) showed a strong seasonality in rates of O2 uptake and coupled nitrification-denitrification, with anammox never accounting for more than 20% of the total dinitrogen (N2) production. N cycling in sediments close to the STP was highly dependent on oxygen availability, which masked temperature-related effects. These sediments switched from low N loss and high ammonium (NH4+) efflux under hypoxic conditions in the fall, to a major N loss system in the winter when the sediment surface was oxidized. In the fall DNRA outcompeted denitrification as the main nitrate (NO3-) reduction pathway, resulting in N recycling and potential spreading of eutrophication. A comparison with historical records of nutrient discharge and denitrification indicated that the total N loss in the estuary has been tightly coupled to the total amount of nutrient discharge from the STP. Changes in dissolved inorganic nitrogen (DIN) released from the STP agreed well with variations in sedimentary N2 removal. This indicates that denitrification and anammox efficiently counterbalance N loading in the estuary across the range of historical and present-day anthropogenic nutrient discharge. Overall low N/P ratios of the regenerated nutrient fluxes impose strong N limitation for the pelagic system and generate a high potential for nuisance cyanobacterial blooms.

  • 109.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hylén, Astrid
    Rattray, Jayne E.
    Kononets, Mikhail Y.
    Ekeroth, Nils
    Roos, Per
    Thamdrup, Bo
    Brüchert, Volker
    Hall, Per O. J.
    The fate of fixed nitrogen in marine sediments with low organic loading: an in situ study2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, no 2, p. 285-300Article in journal (Refereed)
    Abstract [en]

    Over the last decades, the impact of human activities on the global nitrogen (N) cycle has drastically increased. Consequently, benthic N cycling has mainly been studied in anthropogenically impacted estuaries and coasts, while in oligotrophic systems its understanding is still scarce. Here we report on benthic solute fluxes and on rates of denitrification, anammox, and dissimilatory nitrate reduction to ammonium (DNRA) studied by in situ incubations with benthic chamber landers during two cruises to the Gulf of Bothnia (GOB), a cold, oligotrophic basin located in the northern part of the Baltic Sea. Rates of N burial were also inferred to investigate the fate of fixed N in these sediments. Most of the total dissolved fixed nitrogen (TDN) diffusing to the water column was composed of organic N. Average rates of dinitrogen (N-2) production by denitrification and anammox (range: 53-360 mu mol Nm(-2) day(-1)) were comparable to those from Arctic and subarctic sediments worldwide (range: 34-344 mu mol Nm(-2) day(-1)). Anammox accounted for 18-26% of the total N2 production. Absence of free hydrogen sulfide and low concentrations of dissolved iron in sediment pore water suggested that denitrification and DNRA were driven by organic matter oxidation rather than chemolithotrophy. DNRA was as important as denitrification at a shallow, coastal station situated in the northern Bothnian Bay. At this pristine and fully oxygenated site, ammonium regeneration through DNRA contributed more than one-third to the TDN efflux and accounted, on average, for 45% of total nitrate reduction. At the offshore stations, the proportion of DNRA in relation to denitrification was lower (0-16% of total nitrate reduction). Median value and range of benthic DNRA rates from the GOB were comparable to those from the southern and central eutrophic Baltic Sea and other temperate estuaries and coasts in Europe. Therefore, our results contrast with the view that DNRA is negligible in cold and well-oxygenated sediments with low organic carbon loading. However, the mechanisms behind the variability in DNRA rates between our sites were not resolved. The GOB sediments were a major source (237 kt yr(-1), which corresponds to 184% of the external N load) of fixed N to the water column through recycling mechanisms. To our knowledge, our study is the first to document the simultaneous contribution of denitrification, DNRA, anammox, and TDN recycling combined with in situ measurements.

  • 110.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Lund University, Sweden.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences. IGB-Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Germany.
    De Brabandere, Loreto
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM). Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Thamdrup, Bo
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Denitrification and DNRA at the Baltic Sea oxic-anoxic interface: Substrate spectrum and kinetics2016In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 61, no 5, p. 1900-1915Article in journal (Refereed)
    Abstract [en]

    The dependence of denitrification and dissimilatory nitrate reduction to ammonium (DNRA) on different electron donors was tested in the nitrate-containing layer immediately below the oxic-anoxic interface (OAI) at three stations in the central anoxic basins of the Baltic Sea. Additionally, pathways and rates of fixed nitrogen transformation were investigated with N-15 incubation techniques without addition of donors. Denitrification and anammox were always detected, but denitrification rates were higher than anammox rates. DNRA occurred at two sites and rates were two orders of magnitude lower than denitrification rates. Separate additions of dissolved organic carbon and sulfide stimulated rates without time lag indicating that both organotrophic and lithotrophic bacterial populations were simultaneously active and that they could carry out denitrification or DNRA. Manganese addition stimulated denitrification and DNRA at one station, but it is not clear whether this was due to a direct or indirect effect. Ammonium oxidation to nitrite was detected on one occasion. During denitrification, the production of nitrous oxide (N2O) was as important as dinitrogen (N-2) production. A high ratio of N2O to N-2 production at one site may be due to copper limitation, which inhibits the last denitrification step. These data demonstrate the coexistence of a range of oxidative and reductive nitrogen cycling processes at the Baltic OAI and suggest that the dominant electron donor supporting denitrification and DNRA is organic matter. Organotrophic denitrification is more important for nitrogen budgets than previously thought, but the large temporal variability in rates calls for long-term seasonal studies.

  • 111.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nascimento, Francesco
    Stockholm University, Faculty of Science, Department of Geological Sciences. Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bartoli, Marco
    University of Parma.
    Brüchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    EFFECT OF MEIOFAUNA ON BENTHIC ELEMENT CYCLING IN A BALTIC SEA COASTAL AREA2013Conference paper (Refereed)
    Abstract [en]

    We have studied the role of meiofaunal communities for nutrient cycling and organic matter mineralization in coastal sediments of the Baltic Sea. Although meiofauna is orders of magnitude more abundant than macrofauna and has commonly a much more diverse community structure, its importance for sediment biogeochemical pathways is poorly understood because of objective experimental difficulties when manipulating meiofauna communities due to small body sizes (0.04 to 1 mm) and inherent fragility. We used a density extraction method to separate intact and living metazoans from sediment and tested the effect of low meiofauna and high meiofauna abundances in the presence and absence of macrofauna for exchange rates of nutrients, O2, DIC, N2, and CH4. High abundances of meiofauna stimulated O2 uptake and the net N2 efflux by 16% and 34%, respectively, but did not change oxygen penetration depths significantly. By contrast, macrofauna increased oxygen penetration depths by 21% and stimulated methane emissions by a factor of 8. These results demonstrate the importance of meiofauna in the regulation of aerobic and anaerobic microbial processes and benthic fluxes in marine sediments.

  • 112.
    Bonaglia, Stefano
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Nascimento, Francisco J. A.
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bartoli, M.
    Klawonn, Isabell
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Bruchert, Volker
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Meiofauna increases bacterial denitrification in marine sediments2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 5133-Article in journal (Refereed)
    Abstract [en]

    Denitrification is a critical process that can alleviate the effects of excessive nitrogen availability in aquatic ecosystems subject to eutrophication. An important part of denitrification occurs in benthic systems where bioturbation by meiofauna (invertebrates <1mm) and its effect on element cycling are still not well understood. Here we study the quantitative impact of meiofauna populations of different abundance and diversity, in the presence and absence of macrofauna, on nitrate reduction, carbon mineralization and methane fluxes. In sediments with abundant and diverse meiofauna, denitrification is double that in sediments with low meiofauna, suggesting that meiofauna bioturbation has a stimulating effect on nitrifying and denitrifying bacteria. However, high meiofauna densities in the presence of bivalves do not stimulate denitrification, while dissimilatory nitrate reduction to ammonium rate and methane efflux are significantly enhanced. We demonstrate that the ecological interactions between meio-, macrofauna and bacteria are important in regulating nitrogen cycling in soft-sediment ecosystems.

  • 113.
    Borthwick, V. E.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Piazolo, S.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Macquarie University, Australia.
    Evans, L.
    Griera, A.
    Bons, P. D.
    What happens to deformed rocks after deformation?: A refined model for recovery based on numerical simulations2014In: Geological Society Special Publication, ISSN 0305-8719, E-ISSN 2041-4927, Vol. 394, p. 215-234Article in journal (Refereed)
    Abstract [en]

    Deformation, in large parts of the middle crust, results in strained rocks consisting of grains with variable dislocation densities and microstructures which are characterized by gradual distortion and subgrain structures. Post-deformation residence of these rocks at elevated temperatures results in microstructural adjustments through static recovery and recrystallization. Here, we employ a numerical technique to simulate intragrain recovery at temperatures at or below the deformation temperature. The simulation is based on minimization of the stored energy, related to misorientation through local rotation of physical material points relative to their immediate environment. Three temperature-and/or deformation-geometry-dependent parameters were systematically varied: (1) deformation-induced dislocation types, (2) dislocation mobility and (3) size of dislocation interaction volume. Comparison with previously published in situ experiments shows consistency of numerical and experimental results. They show temperature- and dislocation-type-dependent small-scale fluctuations in subgrain-boundary misorientations and orientation variation within subgrains. These can be explained by the combined effect of increase in dislocation interaction volume and activation of climb. Our work shows microstructure can be significantly modified even if the post-deformational temperature is at or below the deformation temperature: a scenario relevant for most deformed rocks.

  • 114.
    Borthwick, Verity
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Fundamentals of substructure dynamics: In-situ experiments and numerical simulation2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Substructure dynamics incorporate all features occurring on a subgrain-scale. The substructure governs the rheology of a rock, which in turn determines how it will respond to different processes during tectonic changes. This project details an in-depth study of substructural dynamics during post-deformational annealing, using single-crystal halite as an analogue for silicate materials. The study combines three different techniques; in-situ annealing experiments conducted inside the scanning electron microscope and coupled with electron backscatter diffraction, 3D X-ray diffraction coupled with in-situ heating conducted at the European Radiation Synchrotron Facility and numerical simulation using the microstructural modelling platform Elle. The main outcome of the project is a significantly refined model for recovery at annealing temperatures below that of deformation preceding annealing. Behaviour is highly dependent on the temperature of annealing, particularly related to the activation temperature of climb and is also strongly reliant on short versus long range dislocation effects. Subgrain boundaries were categorised with regard to their behaviour during annealing, orientation and morphology and it was found that different types of boundaries have different behaviour and must be treated as such. Numerical simulation of the recovery process supported these findings, with much of the subgrain boundary behaviour reproduced with small variation to the mobilities on different rotation axes and increase of the size of the calculation area to imitate long-range dislocation effects. Dislocations were found to remain independent to much higher misorientation angles than previously thought, with simulation results indicating that change in boundary response occurs at ~7º for halite. Comparison of 2D experiments to 3D indicated that general boundary behaviour was similar within the volume and was not significantly influenced by effects from the free surface. Boundary migration, however, occurred more extensively in the 3D experiment. This difference is interpreted to be related to boundary drag on thermal grooves on the 2D experimental surface. While relative boundary mobilities will be similar, absolute values must therefore be treated with some care when using a 2D analysis.

  • 115.
    Borthwick, Verity E.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Schmidt, S.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gundlach, C.
    Quantification of mineral behavior in four dimensions: grain boundary and substructure dynamics in salt2012In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 13, p. Q05005-Article in journal (Refereed)
    Abstract [en]

    Here we present the first four dimensional (time and three dimensional space resolved) experiment on a strongly deformed geological material. Results show that even complicated microstructures with large continuous and discontinuous changes in crystallographic orientation can be resolved quantitatively. The details that can be resolved are unprecedented and therefore the presented technique promises to become influential in a wide range of geoscientific investigations. Grain and subgrain scale processes are fundamental to mineral deformation and associated Earth Dynamics, and time resolved observation of these processes is vital for establishing an in-depth understanding of the latter. However, until recently, in situ experiments were restricted to observations of two dimensional surfaces. We compared experimental results from two dynamic, in situ annealing experiments on a single halite crystal; a 2D experiment conducted inside the scanning electron microscope and a 3D X-ray diffraction experiment. This allowed us to evaluate the possible effects of the free surface on grain and subgrain processes. The extent to which surface effects cause experimental artifacts in 2D studies has long been questioned. Our study shows that, although the nature of recovery processes are the same, the area swept by subgrain boundaries is up to 5 times larger in the volume than observed on the surface. We suggest this discrepancy is due to enhanced drag force on subgrain boundaries by thermal surface grooving. Our results show that while it is problematic to derive absolute mobilities from 2D experiments, derived relative mobilities between boundaries with different misorientation angles can be used.

  • 116.
    Borthwick, Verity
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Post-deformational annealing at the subgrain scale: Temperature dependent behaviour revealed by in-situ heating experiments on deformed single crystal halite2010In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 32, no 7, p. 982-996Article in journal (Refereed)
    Abstract [en]

    The dynamics of substructures, which encompass all structures present at the subgrain-scale, were investigated by static, in-situ annealing experiments. Deformed, single crystal halite was annealed inside a scanning electron microscope at temperatures between 280-470 ºC. Electron backscatter diffraction maps provided detailed information about crystallographic orientation changes. Three temperature dependent regimes were distinguished based on boundary misorientation changes. In regime I (280-300 ºC) some low angle boundaries (LABs), i.e. with 1º-15º misorientation, increase in misorientation angle, while others decrease. In regime II (~300 ºC) all LABs undergo a decrease in misorientation angle. Regime III (>300 ºC) is defined by enhancement of the subgrain structure as remaining LABs increase and some undergo a rotation axis change. Throughout regimes I and II, new LABs develop, subdividing subgrains. LABs could be divided into four categories based on annealing behaviour, orientation and morphology. We suggest that these observations can be directly related to the mobility and activation temperature of climb of two dislocation groups introduced during deformation. Therefore, with in-depth investigation of a substructure with known deformation geometry, we can infer ratios of dislocation types and their post-deformation and post-annealing location. These can potentially be used to estimate the post-deformational annealing temperature in crystalline materials.

  • 117.
    Borthwick, Verity
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Evans, Lynn
    Griera, Albert
    Bons, Paul
    Numerical simulation coupled with in-situ annealing experiments: A new model for recoveryManuscript (preprint) (Other academic)
    Abstract [en]

    A new, deterministic model for recovery integrated with the microstructural modelling platform Elle is presented here. Experimental data collected from 2D in-situ annealing experiments were used to develop and verify the simulation. The model is based on the change of strain energy related to misorientation when a virtual rotation is applied to a crystallite (i.e. physical data point). Boundary energies are calculated using the Read-Shockley relationship. The axes of rotation were selected based on the deformation geometry and potentially activated slip systems. Crystallographic rotation was applied in the case where largest reduction of energy was observed. The effect of parameters such as rotation mobility, neighbourhood size, critical misorientation and specific energy calculation method were systematically investigated. Simulations reproduced many aspects of the experiments and showed that processes were highly dependent on dislocation type and increase of long-range effects with temperature. The results suggest that dislocations remain independent entities for longer than expected, even in an organised subgrain boundary. The model could not, however, retain higher angle boundaries and always resulted in a general shift of boundary distributions towards lower angles. We suggest that the classic interpretation of boundary energies does not entirely work for misorientations that lie in the less defined part of the Read-Shockley relationship.

  • 118.
    Borthwick, Verity
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Schmidt, Søren
    Materials Research Division, Risø DTU.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gundlach, Carsten
    MaxLab, Lund University.
    In-situ 3DXRD annealing of a geological material: Evaluating the validity of 2D Manuscript (preprint) (Other academic)
    Abstract [en]

    Most in-situ heating experiments where substructure is investigated have been restricted to 2D. We compare a 2D experiment to a 3D X-ray diffraction experiment to evaluate the validity of the 2D method. Until now 3D X-ray diffraction has been limited to well-recovered substructures. We conducted a 3D in-situ annealing experiment on a halite crystal with a significant orientation gradient. This is the first experiment of its kind on a geological material and shows that even complicated microstructures can be resolved. Comparison of 2D and 3D showed that, although general results were similar, subgrain boundary movement occurred with higher frequency in 3D. We suggest this discrepancy is due to enhanced drag force on subgrain boundaries by surface thermal grooving. Thus, while results from 2D experiments largely reflect what is happening in the volume, analysis of boundary movement with regard to absolute mobilities needs to be considered with some care.

  • 119.
    Borthwick, Verity
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Schmidt, Søren
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gundlach, Carsten
    Griera, Albert
    Bons, Paul
    Jessell, Mark
    The application of in-situ 3D X-ray Diffraction in annealing experiments: First interpretation of substructure development in deformed NaCl2010In: Recrystallization and Grain Growth: Proceedings of the fourth Joint International Conference of Recrystallization and Grain Growth, 2010Conference paper (Refereed)
    Abstract [en]

    In-situ 3D X-ray diffraction (3DXRD) annealing experiments were conducted at the ID-11 beamline at the European Synchrotron Radiation Facility in Grenoble. This allowed us to non-destructively document and subsequently analyse the development of substructures during heating, without the influence of surface effects. A sample of deformed single crystal halite was heated to between 260-400 ºC. Before and after heating a volume of 500 by 500 by 300 mm was mapped using a planar beam, which was translated over the sample volume at intervals of 5-10 µm in the vertical dimension. In the following we present partially reconstructed orientation maps over one layer before and after heating for 240min at 260 ºC. Additional small syn-heating “maps” over a constrained sample rotation of 12-30º. The purpose of this was to illuminate a few reflections from 1 or 2 subgrains and follow their evolution during heating.

    Preliminary results show that significant changes occurred within the sample volume, for which, surface effects can be excluded. Results show a number of processes, including: i) change in subgrain boundary misorientation angle and ii) subgrain subdivision into areas of similar lattice orientation with new subgrain boundary formation. These results demonstrate that 3DXRD coupled with in-situ heating is a successful non-destructive technique for examining real-time post-deformational annealing in strongly deformed crystalline materials with complicated microstructures.

  • 120.
    Boskabadi, Ahmad
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pitcairn, Iairn K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stern, R. J.
    Azer, M. K.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mohamed, F. H.
    Majka, J.
    Carbonatite crystallization and alteration in the Tarr carbonatite-albitite complex, Sinai Peninsula, Egypt2013In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. - 239, p. 24-41Article in journal (Refereed)
    Abstract [en]

    Carbonate dykes occurring in the Arabian-Nubian Shield (ANS) are clearly intrusive in origin and carbonatites according to the IUGS classification, yet previous investigations refer to them as “intrusive carbonates”, due mainly to their low Sr, Ba, Nb, Y, Th and rare earth element (REE) contents. The Tarr carbonatite albitite complex (TCA) in SE Sinai, Egypt contains a series of small (<1.2 km2) albitite intrusions surrounded by small veins and dykes of carbonatite, which occur predominantly in a narrow zone of brecciation surrounding the intrusions. Fennitic alteration surrounding TCA has been reported but there is little consensus on the extent and origin of this alteration. Fennitic alteration surrounding the TCA carbonatites is not abundant. Alteration is dominated by precipitation of carbonates in the breccia zone surrounding the albitite intrusion with associated actinolite, chlorite, sericite and epidote. Geochemical compositions are consistent with addition of carbonates and associated secondary minerals because the altered rocks contain higher CaO, MgO, Fe2O3 and MnO and lower SiO2, Al2O3, Na2O and K2O compared to their less altered rocks. Fluid inclusion investigations show that the carbonatite magma contained a high-salinity H2O–CO2–NaCl–CaCl2 fluid, although the lack of fennitic alteration implies that this fluid was not abundant. The crystallization conditions of the carbonatite dykes and carbonatite matrix in the breccia zones have been constrained using Zr-in-rutile thermometry and fluid inclusion microthermometry. Crystallization of the carbonatite in the dykes and in the breccia zone occurred between 565 ± 38 °C and 420–480 °C, respectively and at 0.75–1.3 kbar, which corresponds to a depth of 2.8–4.9 km. Rutile hosted within the carbonatite crystallized earlier at high temperature and the carbonate matrix crystallized later after cooling. Immiscible fluid from carbonatite magma would have altered the surrounding country rocks at lower temperature (between 400 °C and 150 °C deduced from the fluid inclusion thermometry) after the intrusion of the carbonatite melt.

  • 121.
    Boskabadi, Arman
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. University of Texas at Dallas, USA.
    Pitcairn, Iain K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Boyce, Adrian
    Teagle, Damon A. H.
    Cooper, Matthew J.
    Azer, Mokhles K.
    Stern, Robert J.
    Mohamed, Fathy H.
    Majka, Jaroslaw
    Carbonate alteration of ophiolitic rocks in the Arabian-Nubian Shield of Egypt: sources and compositions of the carbonating fluid and implications for the formation of Au deposits2017In: International Geology Review, ISSN 0020-6814, E-ISSN 1938-2839, Vol. 59, no 4, p. 391-419Article, review/survey (Refereed)
    Abstract [en]

    Ultramafic portions of ophiolitic fragments in the Arabian-Nubian Shield (ANS) show pervasive carbonate alteration forming various degrees of carbonated serpentinites and listvenitic rocks. Notwithstanding the extent of the alteration, little is known about the processes that caused it, the source of the CO2 or the conditions of alteration. This study investigates the mineralogy, stable (O, C) and radiogenic (Sr) isotope composition, and geochemistry of suites of variably carbonate altered ultramafics from the Meatiq area of the Central Eastern Desert (CED) of Egypt. The samples investigated include least-altered lizardite (Lz) serpentinites, antigorite (Atg) serpentinites and listvenitic rocks with associated carbonate and quartz veins. The C, O and Sr isotopes of the vein samples cluster between -8.1 parts per thousand and -6.8 parts per thousand for delta C-13, +6.4 parts per thousand and +10.5 parts per thousand for delta O-18, and Sr-87/Sr-86 of 0.7028-0.70344, and plot within the depleted mantle compositional field. The serpentinites isotopic compositions plot on a mixing trend between the depleted-mantle and sedimentary carbonate fields. The carbonate veins contain abundant carbonic (CO2 +/- CH4 +/- N-2) and aqueous-carbonic (H2O-NaCl-CO2 +/- CH4 +/- N-2) low salinity fluid, with trapping conditions of 270-300 degrees C and 0.7-1.1kbar. The serpentinites are enriched in Au, As, S and other fluid-mobile elements relative to primitive and depleted mantle. The extensively carbonated Atg-serpentinites contain significantly lower concentrations of these elements than the Lz-serpentinites suggesting that they were depleted during carbonate alteration. Fluid inclusion and stable isotope compositions of Au deposits in the CED are similar to those from the carbonate veins investigated in the study and we suggest that carbonation of ANS ophiolitic rocks due to influx of mantle-derived CO2-bearing fluids caused break down of Au-bearing minerals such as pentlandite, releasing Au and S to the hydrothermal fluids that later formed the Au-deposits. This is the first time that gold has been observed to be remobilized from rocks during the lizardite-antigorite transition.

  • 122. Bouton, Anthony
    et al.
    Vennin, Emmanuelle
    Boulle, Julien
    Pace, Aurelie
    Bourillot, Raphael
    Thomazo, Christophe
    Brayard, Arnaud
    Desaubliaux, Guy
    Goslar, Tomasz
    Yokoyama, Yusuke
    Dupraz, Christophe
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Visscher, Pieter T.
    Linking the distribution of microbial deposits from the Great Salt Lake (Utah, USA) to tectonic and climatic processes2016In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 13, no 19, p. 5511-5526Article in journal (Refereed)
    Abstract [en]

    The Great Salt Lake is a modern hypersaline lake, in which an extended modern and ancient microbial sedimentary system has developed. Detailed mapping based on aerial images and field observations can be used to identify non-random distribution patterns of microbial deposits, such as paleoshorelines associated with extensive polygons or fault-parallel alignments. Although it has been inferred that climatic changes controlling the lake level fluctuations explain the distribution of paleoshorelines and polygons, straight microbial deposit alignments may underline a normal fault system parallel to the Wasatch Front. This study is based on observations over a decimetre to kilometre spatial range, resulting in an integrated conceptual model for the controls on the distribution of the microbial deposits. The morphology, size and distribution of these deposits result mainly from environmental changes (i.e. seasonal to long-term water level fluctuations, particular geomorphological heritage, fault-induced processes, groundwater seepage) and have the potential to bring further insights into the reconstruction of paleoenvironments and paleoclimatic changes through time. New ra-diocarbon ages obtained on each microbial macrofabric described in this study improve the chronological framework and question the lake level variations that are commonly assumed.

  • 123. Bouton, Anthony
    et al.
    Vennin, Emmanuelle
    Pace, Aurélie
    Bourillot, Raphaël
    Dupraz, Christophe
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Thomazo, Christophe
    Brayard, Arnaud
    Désaubliaux, Guy
    Visscher, Pieter T.
    External controls on the distribution, fabrics and mineralization of modern microbial mats in a coastal hypersaline lagoon, Cayo Coco (Cuba)2016In: Sedimentology, ISSN 0037-0746, E-ISSN 1365-3091, Vol. 63, no 4, p. 972-1016Article in journal (Refereed)
    Abstract [en]

    Active, carbonate-mineralizing microbial mats flourish in a tropical, highly evaporative, marine-fed lagoonal network to the south of Cayo Coco Island (Cuba). Hypersaline conditions support the development of a complex sedimentary microbial ecosystem with diverse morphologies, a variable intensity of mineralization and a potential for preservation. In this study, the role of intrinsic (i.e. microbial) and extrinsic (i.e. physicochemical) controls on microbial mat development, mineralization and preservation was investigated. The network consists of lagoons, forming in the interdune depressions of a Pleistocene aeolian substratum; they developed due to a progressive increase in sea-level since the Holocene. The hydrological budget in the Cayo Coco lagoonal network changes from west to east, increasing the salinity. This change progressively excludes grazers and increases the saturation index of carbonate minerals, favouring the development and mineralization of microbial mats in the easternmost lagoons. Detailed mapping of the easternmost lagoon shows four zones with different flooding regimes. The microbial activity in the mats was recorded using light-dark shifts in conjunction with microelectrode O-2 and HS- profiles. High rates of O-2 production and consumption, in addition to substantial amounts of exopolymeric substances, are indicative of a potentially strong intrinsic control on mineralization. Seasonal, climate-driven water fluctuations are key for mat development, mineralization, morphology and distribution. Microbial mats show no mineralization in the permanently submersed zone, and moderate mineralization in zones with alternating immersion and exposure. It is suggested that mineralization is also driven by water-level fluctuations and evaporation. Mineralized mats are laminated and consist of alternating trapping and binding of grains and microbially induced magnesium calcite and dolomite precipitation. The macrofabrics of the mats evolve from early colonizing Flat mats to complex Cerebroid or Terrace structures. The macrofabrics are influenced by the hydrodynamic regime: wind-driven waves inducing relief terraces in windward areas and flat morphologies on the leeward side of the lagoon. Other external drivers include: (i) storm events that either promote (for example, by bioclasts covering) or prevent (for example, by causing erosion) microbial mat preservation; and (ii) subsurface degassing, through mangrove roots and desiccation cracks covered by Flat mats (i.e. forming Hemispheroids and Cerebroidal structures). These findings provide in-depth insights into understanding fossil microbialite morphologies that formed in lagoonal settings.

  • 124. Brandefelt, J.
    et al.
    Kjellstrom, E.
    Naslund, J. -O
    Strandberg, G.
    Voelker, A. H. L.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    A coupled climate model simulation of Marine Isotope Stage 3 stadial climate2011In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 7, no 2, p. 649-670Article in journal (Refereed)
    Abstract [en]

    We present a coupled global climate model (CGCM) simulation, integrated for 1500 yr to quasi-equilibrium, of a stadial (cold period) within Marine Isotope Stage 3 (MIS 3). The simulated Greenland stadial 12 (GS12; similar to 44 ka BP) annual global mean surface temperature (T(s)) is 5.5 degrees C lower than in the simulated recent past (RP) climate and 1.3 degrees C higher than in the simulated Last Glacial Maximum (LGM; 21 ka BP) climate. The simulated GS12 is evaluated against proxy data and previous modelling studies of MIS3 stadial climate. We show that the simulated MIS 3 climate, and hence conclusions drawn regarding the dynamics of this climate, is highly model-dependent. The main findings are: (i) Proxy sea surface temperatures (SSTs) are higher than simulated SSTs in the central North Atlantic, in contrast to earlier simulations of MIS 3 stadial climate in which proxy SSTs were found to be lower than simulated SST. (ii) The Atlantic Meridional Overturning Circulation (AMOC) slows down by 50% in the GS12 climate as compared to the RP climate. This slowdown is attained without freshwater forcing in the North Atlantic region, a method used in other studies to force an AMOC shutdown. (iii) El-Nino-Southern Oscillation (ENSO) teleconnections in mean sea level pressure (MSLP) are significantly modified by GS12 and LGM forcing and boundary conditions. (iv) Both the mean state and variability of the simulated GS12 is dependent on the equilibration. The annual global mean T(s) only changes by 0.10 degrees C from model years 500-599 to the last century of the simulation, indicating that the climate system may be close to equilibrium already after 500 yr of integration. However, significant regional differences between the last century of the simulation and model years 500-599 exist. Further, the difference between simulated and proxy SST is reduced from model years 500-599 to the last century of the simulation. The results of the ENSO variability analysis is also shown to depend on the equilibration.

  • 125.
    Brander, Linus
    et al.
    Department of Earth Sciences, University of Gothenburg.
    Svahnberg, Henrik
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brittle-plastic deformation in initially dry rocks at fluid present conditions: Transient behavior of feldspar at mid crustal levelsManuscript (preprint) (Other academic)
  • 126. Brander, Linus
    et al.
    Svahnberg, Henrik
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Piazolo, Sandra
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Brittle-plastic deformation in initially dry rocks at fluid-present conditions: transient behaviour of feldspar at mid-crustal levels2012In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 163, no 3, p. 403-425Article in journal (Refereed)
    Abstract [en]

    We present detailed microstructural and chemical analyses from an initially dry anorthositic rock deformed during wet amphibolite facies conditions. Three different domains representing the microstructural variation of the deformed samples are investigated in detail in terms of fracture morphology and mode, grain characteristics and chemistry of present phases. Results show transient deformational behaviour where a close interaction between brittle, plastic and fluid-assisted deformation mechanisms can be observed. Our analysis allows us to describe the succession, interrelationships and effects of active mechanisms with progressively increasing strain in three so-called stages. In Stage 1, initial fracturing along cleavage planes promoted fluid influx that caused fragmentation and chemical reactions, producing fine-grained mineral assemblages in the fractures. Deformation twins and dislocations developed in clast pieces due to stress relaxation. Passive rotation of conjugate fracture sets and interconnection of intracrystalline fractures formed micro-shear-zones, constituting Stage 2. Microstructures and grain relationships indicate the activity and fluctuation between fracturing, dissolution-precipitation creep, grain boundary sliding and locally dislocation creep, reflecting the transient behaviour of brittle and plastic deformation mechanisms. Further rotation and widening of fractures into overall foliation parallel shear-bands (Stage 3) promoted strain partitioning into these areas through increased fluid influx, influence of fluid-assisted grain boundary sliding, phase mixing and presence of weak phases such as white mica. We suggest that local differences in fluid availability, volume fraction of weak phases produced by fluid present metamorphic reactions coupled with volume increase and local variations in stress concentration induced transient brittle-plastic behaviour. The studied shear-zone represents an example of the transformation of a rigid dry rock to a soft wet rock during deformation through syntectonic fracturing.

  • 127. Braun, Stefan
    et al.
    Mhatre, Snehit S.
    Jaussi, Marion
    Roy, Hans
    Kjeldsen, Kasper U.
    Pearce, Christof
    Stockholm University, Faculty of Science, Department of Geological Sciences. Aarhus University, Denmark.
    Seidenkrantz, Marit-Solveig
    Jorgensen, Bo Barker
    Lomstein, Bente Aa.
    Microbial turnover times in the deep seabed studied by amino acid racemization modelling2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 5680Article in journal (Refereed)
    Abstract [en]

    The study of active microbial populations in deep, energy-limited marine sediments has extended our knowledge of the limits of life on Earth. Typically, microbial activity in the deep biosphere is calculated by transport-reaction modelling of pore water solutes or from experimental measurements involving radiotracers. Here we modelled microbial activity from the degree of D: L-aspartic acid racemization in microbial necromass (remains of dead microbial biomass) in sediments up to ten million years old. This recently developed approach (D: L-amino acid modelling) does not require incubation experiments and is highly sensitive in stable, low-activity environments. We applied for the first time newly established constraints on several important input parameters of the D: L-amino acid model, such as a higher aspartic acid racemization rate constant and a lower cell-specific carbon content of sub-seafloor microorganisms. Our model results show that the pool of necromass amino acids is turned over by microbial activity every few thousand years, while the turnover times of vegetative cells are in the order of years to decades. Notably, microbial turnover times in million-year-old sediment from the Peru Margin are up to 100-fold shorter than previous estimates, highlighting the influence of microbial activities on element cycling over geologic time scales.

  • 128.
    Bredberg, Camilla
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    A lake sedimant record from southern Thailand: monsoon variability and ecosystem change since 18 ka2015Licentiate thesis, comprehensive summary (Other academic)
  • 129.
    Bringensparr, Caroline
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Glacial morphology and bathymetric mapping in Melville Bay, Western Greenland - Multibeam and backscatter mosaic2014Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During the VEGA Expedition, in June 2013, reflectivity (backscatter) and depth data wasacquired with a multibeam echosounder from an approximately 140 km2 large area in MelvilleBay, off the coast of Western Greenland. One of the expedition objectives was to search for andmap evidences of a grounded ice sheet, which is likely to have reached the edge of the continentalshelf during the Last Glacial Maximum, about 20 000 years ago. In this study, the acquired depthdata was compiled to a detailed bathymetric map, which was used to map the extension ofmorphological features caused by the ice sheet’s progression over the area. The results showbedrock erosion in the form of linear features, melt-water channels and different types ofdepressions. The surface sediment distribution, based on the reflectivity data, presents coarsersediment such as gravel in the deeper parts of the survey area as well as in channels anddepressions, while finer sediments such as silt and clay can be found generally in the remainder ofthe area. The conclusion is that the results strongly suggests there have been glacial erosion inthis area, however it is not possible to determine when this took place without age determinationof bottom samples. For a more comprehensive understanding of the glacial history in Melvilleand Baffin Bay, more surveys of this kind are necessary.

  • 130. Brinkhuis, Henk
    et al.
    Schouten, Stefan
    Collinson, Margaret E.
    Sluijs, Appy
    Sinninghe Damste, Jaap S.
    Dickens, Gerald R.
    Huber, Matthew
    Cronin, Thomas M.
    Onodera, Jonaotaro
    Takahashi, Kozo
    Bujak, Jonathan P.
    Stein, Ruediger
    van der Burgh, Johan
    Eldrett, James S.
    Harding, Ian C.
    Lotter, André F.
    Sangiorgi, Francesca
    van Konijnenburg-van Cittert, Han
    de Leeuw, Jan W.
    Matthiessen, Jens
    Backman, Jan
    Moran, Kathryn
    Clemens, Steve
    Eynaud, Frédérique
    Gattacceca, Jérôme
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jordan, Ric
    Kaminski, Michael
    King, John
    Koc, Nalan
    Martinez, Nahysa C.
    McInroy, David
    Moore, Theodore C.
    O’Regan, Matthew
    Pälike, Heiko
    Rea, Brice
    Rio, Domenico
    Sakamoto, Tatsuhiko
    Smith, David C.
    John, Kristen E. K. St
    Suto, Itsuki
    Suzuki, Noritoshi
    Mahito, Watanabe
    Yamamoto, Masanobu
    Episodic fresh surface waters in the Eocene Arctic Ocean2006In: Nature, Vol. 441Article in journal (Refereed)
  • 131.
    Broman, Curt
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sturkell, Erik
    Fallick, Anthony E.
    Oxygen isotopes and implications for the cavity-grown quartz crystals in the Lockne impact structure, Sweden2011In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 133, no 02-jan, p. 101-107Article in journal (Refereed)
    Abstract [en]

    Well-developed quartz crystals are found in open cavities in the intensely fractured crystalline basement of the marine-target impact structure at Lockne in central Sweden. The 458 Ma impact structure has a well-preserved crater in Precambrian granitic basement rock that is covered by resurge deposits composed of breccias and fine-grained sedimentary units of mixed Ordovician limestone, Cambrian black bituminous shales and the basement granite. Directly after the impact, the resurge deposits formed when the seawater rushed back into the crater. The residual heat from the impact facilitated a short-lived hydrothermal system accompanied by the inflowing seawater, which resulted in mineral growth in fractures and open cavities of the granite basement. The oxygen isotope values of the first-precipitated minerals, the cavity-grown quartz crystals, range from +15.2 to +16.2 parts per thousand (Vienna Standard Mean Ocean Water) and differ from those of the hosting granite basement rock with delta(18)O quartz between +10.1 and +11.7 parts per thousand. The delta(18)O values of the quartz are more consistent with derivation from a fluid of relatively high delta(18)O probably attributable to oxygen isotope exchange during seawater-rock interactions in the resurge deposits. The occurrence of organic matter in association with the cavity-grown quartz strongly indicates a relationship to the black bituminous shale in the matrix of the breccia that rests on the crater floor. Comparing the results with previously obtained oxygen data on fracture-grown calcite from Lockne shows that oxygen isotope composition of the cavity-grown quartz crystals is less variable and probably more accurately reflects the original fluid source.

  • 132.
    Broman, Curt
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sundblad, K.
    Valkama, M.
    Villar, A.
    Deposition conditions for the indium-bearing polymetallic quartz veins at Sarvlaxviken, south-eastern Finland2018In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 82, p. S43-S59Article in journal (Refereed)
    Abstract [en]

    Polymetallic quartz veins, with up to 1500ppm indium, have been discovered recently in the Sarvlaxviken area within the 1.64Ga anorogenic multiphase Wiborg rapakivi batholith and adjacent 1.90Ga Svecofennian crust in SE Finland. Evidence from primary fluid inclusions in the Sarvlaxviken area provides new information on the hydrothermal transport and depositional processes of metals in anorogenic granites. Fluid inclusions with variable aqueous liquid and vapour proportions (5-90vol.% vapour) occur in quartz, cassiterite and fluorite belonging to three generations of polymetallic quartz veins. Microthermometry indicates that the veins were deposited at temperatures that range from similar to 500 degrees C down to <100 degrees C and salinities from 0 to 16 eq. mass% NaCl. Fluid inclusion data show that the depositional conditions were similar regardless of vein generation. The interpreted depositional processes involve phase separation with a combination of condensation, cooling and boiling of an initially low-salinity (<3 eq. mass% NaCl) aqueous magmatic vapour phase enriched in CO2-F-Cl-S and metals. Fluid inclusions with low salinities dominate, but higher salinities are recorded in metal-rich parts of the veins. The turbulent fluid flow, with complex geometry and temperature-salinity patterns, may explain why sulfide and/or oxide opaque minerals occur irregularly, and are locally the dominating vein minerals, but disappear completely into barren parts of the quartz veins. All fluids are considered to have been generated by the F-rich Marviken granite (and related granite dykes), which show all geochemical criteria for an ore-fertile granite. The quartz veins investigated in the adjacent Svecofennian country rocks are considered to represent the very last stage of a fluid with similar characteristics to the fluid responsible for the ore formation in the Sarvlaxviken area, but that had cooled to <100 degrees C.

  • 133.
    Brüchert, Volker
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Deutsch, Barbara
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    BENTHIC BOUNDARY LAYER NUTRIENT AND OXYGEN BIOGEOCHEMISTRY IN A EUTROPHIED BALTIC SEA ESTUARY2013Conference paper (Refereed)
    Abstract [en]

    We present dissolved nutrient and oxygen concentrations determined with a benthic boundary layer profiling system for a set of stations along a eutrophication gradient in a Baltic Sea estuary. The sampling system yields vertically highly resolved CTD, oxygen, and nutrient profiles of the lowermost 80 cm of water overlying the sediment. Continuous oxygen and CTD measurements over 8 – 24 hours at fixed depths above the sediment surface provided information on the temporal variability of nutrients and the physical structure within the benthic boundary layer. These data indicate multiple short-term episodes of vertical mixing and stable stratification within the boundary layer that can lead to short-term fluctuations in bottom water oxygen of more than 100 µM. This high degree of temporal variability needs to be taken into account for benthic flux calculations that assume vertically mixed benthic boundary layers.

     

  • 134.
    Brüchert, Volker
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bonaglia, Stefano
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Raymond, Caroline
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Sediment med nyckelroll i näringsväven2014In: HavsUtsikt, ISSN 1104-0513, Vol. 1, p. 20-21Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    I sedimenten sker processer som kan vara helt avgörande för näringsbalansen i havsvattnet. Omvandlingen av fosfor till olika former är relativt väl känd, medan detaljerna i kvävets kretslopp är betydligt mindre kända. Mer än hälften av den årliga tillförseln av kväve till Östersjön beräknas omsättas till kvävgas i sedimentet, vilket sedan går förlorat för de flesta marina organismer.

  • 135.
    Brüchert, Volker
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bröder, Lisa
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Sawicka, Joanna E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Tesi, Tommaso
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry. nstitute of Marine Sciences, National Research Council, Italy.
    Joye, Samantha P.
    Sun, Xiaole
    Stockholm University, Faculty of Science, Stockholm University Baltic Sea Centre.
    Semiletov, Igor P.
    Samarkin, Vladimir A.
    Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 2, p. 471-490Article in journal (Refereed)
    Abstract [en]

    The Siberian Arctic Sea shelf and slope is a key region for the degradation of terrestrial organic material transported from the organic carbon-rich permafrost regions of Siberia. We report on sediment carbon mineralization rates based on O2 microelectrode profiling, intact sediment core incubations, 35 S-sulfate tracer experiments, porewater dissolved inorganic carbon (DIC), δ13 CDIC, and iron, manganese, and ammonium concentrations from 20 shelf and slope stations. This data set provides a spatial overview of sediment carbon mineralization rates and pathways over large parts of the outer Laptev and East Siberian Arctic shelf and slope, and allowed us to assess degradation rates and efficiency of carbon burial in these sediments. Rates of oxygen uptake and iron and manganese reduction were comparable to temperate shelf and slope environments, but bacterial sulfate reduction rates were comparatively low. In the topmost 20 to 50 cm of sediment, aerobic carbon mineralization dominated degradation and comprised on average 82% of the depthintegrated carbon mineralization. Oxygen uptake rates and 35 S-sulfate reduction rates were higher in the eastern East Siberian Sea shelf compared to the Laptev Sea shelf. DIC/NH4 + ratios in porewaters and the stable carbon isotope composition of remineralized DIC indicated that the degraded organic matter on the Siberian shelf and slope was a mixture of marine and terrestrial organic matter. Based on dual end member calculations, the terrestrial organic carbon contribution varied between 32% and 36%, with a higher contribution in the Laptev Sea than in the East Siberian Sea. Extrapolation of the measured degradation rates using  isotope end member apportionment over the outer shelf of the Laptev and East Siberian Sea suggests that about 16 Tg C per year are respired in the outer shelf sea floor sediment. Of the organic matter buried below the oxygen penetration depth, between 0.6 and 1.3 Tg C per year are degraded by anaerobic processes, with a terrestrial organic carbon contribution ranging between 0.3 and 0.5 Tg per year.

  • 136. Bukala, Michal
    et al.
    Klonowska, Iwona
    Barnes, Christopher
    Majka, Jaroslaw
    Kosminska, Karolina
    Janak, Marian
    Fassmer, Kathrin
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Luptakova, Jarmila
    UHP metamorphism recorded by phengite eclogite from the Caledonides of northern Sweden: P-T path and tectonic implications2018In: Journal of Metamorphic Geology, ISSN 0263-4929, E-ISSN 1525-1314, Vol. 36, no 5, p. 547-566Article in journal (Refereed)
    Abstract [en]

    The Seve Nappe Complex (SNC) of the Scandinavian Caledonides records a well-documented history of high pressure (HP) and ultra-high pressure (UHP) metamorphism. Eclogites of the SNC occur in two areas in Sweden, namely Jamtland and Norrbotten. The Jamtland eclogites and associated rocks are well-studied and provide evidence for late Ordovician UHP metamorphism, whereas the Norrbotten eclogites, formed during the late Cambrian (Furongian)/Early Ordovician, have not been studied in such detail, especially in terms of the P-T conditions of their formation. Within the studied eclogite, clinopyroxene contains a high-Na core and two rims: inner, medium-Na and outer, low-Na. Garnet consists of a high-Ca euhedral core, low-Ca inner rim and medium-Ca outer rim. A similar pattern occurs within phengite, where high-Si cores are enveloped by medium and low-Si rims. The compositions of the mineral cores, inner rims and outer rims reflect three stages in the metamorphic evolution of the eclogite. Applied Quartz-in-Garnet geobarometry, coupled with Zr-in-rutile geothermometry reveal that garnet nucleation (E0 stage) took place at 1.5-1.6GPa and 620-660 degrees C. The eclogite peak-pressure assemblage developed during the E1 stage, it consists of garnet+omphacite+phengite+rutile+coesite? and yields P-T conditions of 2.8-3.1GPa and 660-780 degrees C as constrained by conventional geothermobarometry and thermodynamic modelling in the NCKFMMnASHT system. Later, lower-pressure stages E2 and E3 record conditions of 2.2-2.8GPa, 680-780 degrees C and 2.1GPa, 735 degrees C, respectively. The prograde metamorphic evolution of the eclogite is inferred from inclusions of epidote, amphibole and clinopyroxene within garnet. The presence of amphibole-quartz-plagioclase symplectites, secondary epidote/zoisite and titanite replacing rutile record the later retrograde changes taking place at <1.5GPa (referred as E4 stage). The obtained P-T conditions indicate that the Norrbotten eclogites underwent a metamorphic evolution characterized by a clockwise P-T path with peak metamorphism reaching up to coesite stability field within a relatively cold subduction regime (7.8 degrees C/km). The obtained results provide the first evidence for UHP metamorphism in the SNC above the Arctic Circle and document cold subduction regime and multistage exhumation of the deeply subducted Baltican margin at early stage of the Caledonian Orogeny.

  • 137. Burdette, Shawn C.
    et al.
    Ball, Philip
    Day, Kat
    Scerri, Eric R.
    Thornton, Brett F.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Another four bricks in the wall2016In: Nature Chemistry, ISSN 1755-4330, E-ISSN 1755-4349, Vol. 8, no 4, p. 283-288Article in journal (Other academic)
    Abstract [en]

    Of all the things humans can bestow names upon, new chemical elements are about the rarest. Our group of periodic table experts attempts to read the tea leaves and predict the names for elements 113, 115, 117 and 118.

  • 138.
    Bäckstrand, Kristina
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Crill, Patrick, M.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jackowicz-Korczyński, Marcin
    Mastepanov, Mikhail
    Christensen, Torben, R.
    Bastviken, David
    Annual carbon gas budget for a subarctic peatland, northern Sweden2010In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7, no 1, p. 95-108Article in journal (Refereed)
    Abstract [en]

    Temperatures in the Arctic regions are rising, thawing permafrost and exposing previously stable soil organic carbon (OC) to decomposition. This can result in northern latitude soils, which have accumulated large amounts of OC potentially shifting from atmospheric C sinks to C sources with positive feedback on climate warming. In this paper, we estimate the annual net C gas balance (NCB) of the subarctic mire Stordalen, based on automatic chamber measurements of CO2 and total hydrocarbon (THC; CH4 and NMVOCs) exchange. We studied the dominant vegetation communities with different moisture and permafrost characteristics; a dry Palsa underlain by permafrost, an intermediate thaw site with Sphagnum spp. and a wet site with Eriophorum spp. where the soil thaws completely. Whole year accumulated fluxes of CO2 were estimated to 29.7, −35.3 and −34.9 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum sites (positive flux indicates an addition of C to the atmospheric pool). The corresponding annual THC emissions were 0.5, 6.2 and 31.8 gC m−2 for the same sites. Therefore, the NCB for each of the sites was 30.2, −29.1 and −3.1 gC m−2 respectively for the Palsa, Sphagnum and Eriophorum site. On average, the whole mire was a CO2 sink of 2.6 gC m−2 and a THC source of 6.4 gC m−2 over a year. Consequently, the mire was a net source of C to the atmosphere by 3.9 gC m−2 (based on area weighted estimates for each of the three plant communities). Early and late snow season efflux of CO2 and THC emphasize the importance of winter measurements for complete annual C budgets. Decadal vegetation changes at Stordalen indicate that both the productivity and the THC emissions increased between 1970 and 2000. Considering the GWP100 of CH4, the net radiative forcing on climate increased 21% over the same time. In conclusion, reduced C compounds in these environments have high importance for both the annual C balance and climate.

  • 139.
    Bäckström, Alexander
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    A new digital bathymetric model of Lake Vättern, Southern Sweden2018Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
  • 140.
    Bäckström, Alexander
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sediment classification from backscatter analysis of multibeam data from Lake Vättern2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 141. Cabral, Rita A.
    et al.
    Jackson, Matthew G.
    Rose-Koga, Estelle F.
    Koga, Kenneth T.
    Whitehouse, Martin J.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Antonelli, Michael A.
    Farquhar, James
    Day, James M. D.
    Hauri, Erik H.
    Anomalous sulphur isotopes in plume lavas reveal deep mantle storage of Archaean crust2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 496, no 7446, p. 490-494Article in journal (Refereed)
    Abstract [en]

    Basaltic lavas erupted at some oceanic intraplate hotspot volcanoes are thought to sample ancient subducted crustal materials(1,2). However, the residence time of these subducted materials in the mantle is uncertain and model-dependent(3), and compelling evidence for their return to the surface in regions of mantle upwelling beneath hotspots is lacking. Here we report anomalous sulphur isotope signatures indicating mass-independent fractionation (MIF) in olivine-hosted sulphides from 20-million-year-old ocean island basalts from Mangaia, Cook Islands (Polynesia), which have been suggested to sample recycled oceanic crust(3,4). Terrestrial MIF sulphur isotope signatures (in which the amount of fractionation does not scale in proportion with the difference in the masses of the isotopes) were generated exclusively through atmospheric photochemical reactions until about 2.45 billion years ago(5-7). Therefore, the discovery of MIF sulphur in these young plume lavas suggests that sulphur-probably derived from hydrothermally altered oceanic crust-was subducted into the mantle before 2.45 billion years ago and recycled into the mantle source of Mangaia lavas. These new data provide evidence for ancient materials, with negative Delta S-33 values, in the mantle source for Mangaia lavas. Our data also complement evidence for recycling of the sulphur content of ancient sedimentary materials to the subcontinental lithospheric mantle that has been identified in diamond-hosted sulphide inclusions(8,9). This Archaean age for recycled oceanic crust also provides key constraints on the length of time that subducted crustal material can survive in the mantle, and on the timescales of mantle convection from subduction to upwelling beneath hotspots.

  • 142.
    Callac, Nolwenn
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Université de Brest, France; Ifremer, France; CNRS, France.
    Oger, Philippe
    Lesongeur, Francoise
    Rattray, Jayne E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Vannier, Pauline
    Michoud, Gregoire
    Beauverger, Mickael
    Gayet, Nicolas
    Rouxel, Olivier
    Jebbar, Mohamed
    Godfroy, Anne
    Pyrococcus kukulkanii sp nov., a hyperthermophilic, piezophilic archaeon isolated from a deep-sea hydrothermal vent2016In: International Journal of Systematic and Evolutionary Microbiology, ISSN 1466-5026, E-ISSN 1466-5034, Vol. 66, p. 3142-3149Article in journal (Refereed)
    Abstract [en]

    A novel hyperthermophilic, piezophilic, anaerobic archaeon, designated NCB100(T), was isolated from a hydrothermal vent flange fragment collected in the Guaymas basin at the hydrothermal vent site named 'Rebecca's Roost' at a depth of 1997 m. Enrichment and isolation were performed at 100 degrees C under atmospheric pressure. Cells of strain NCB100(T) were highly motile, irregular cocci with a diameter of -1 mu m. Growth was recorded at temperatures between 70 and 112 degrees C (optimum 105 degrees C) and hydrostatic pressures of 0.1-80 MPa (optimum 40-50 MPa). Growth was observed at pH 3.5-8.5 (optimum pH 7) and with 1.5-7% NaCl (optimum at 2.5-3 %). Strain NCB100(T) was a strictly anaerobic chemo-organoheterotroph and grew on complex proteinaceous substrates such as yeast extract, peptone and tryptone, as well as on glycogen and starch. Elemental sulfur was required for growth and was reduced to hydrogen sulfide. The fermentation products from complex proteinaceous substrates were CO2 and H-2. The G+C content of the genomic DNA was 41.3 %. Phylogenetic analysis of the 16S rRNA gene sequence revealed that strain NCB100(T) belongs to the genus Pyrococcus, showing 99% similarity with the other described species of the genus Pyrococcus. On the basis of physiological characteristics, DNA G+C content, similarity level between ribosomal proteins and an average nucleotide identity value of 79 %, strain NCB100(T) represents a novel species for which the name Pyrococcus kukulkanii sp. nov. is proposed. The type strain is NCB100(T) (=DSM 101590(T) =Souchotheque de Bretagne BG1337(T)).

  • 143.
    Callac, Nolwenn
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Posth, Nicole R.
    Rattray, Jayne E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Yamoah, Kweku K. Y.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wiech, Alan
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Hemmingsson, Christoffer
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kilias, Stephanos P.
    Argyraki, Ariadne
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skogby, Henrik
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chi Fru, Ernest
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Modes of carbon fixation in an arsenic and CO2-rich shallow hydrothermal ecosystem2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 14708Article in journal (Refereed)
    Abstract [en]

    The seafloor sediments of Spathi Bay, Milos Island, Greece, are part of the largest arsenic-CO2-rich shallow submarine hydrothermal ecosystem on Earth. Here, white and brown deposits cap chemically distinct sediments with varying hydrothermal influence. All sediments contain abundant genes for autotrophic carbon fixation used in the Calvin-Benson-Bassham (CBB) and reverse tricaboxylic acid (rTCA) cycles. Both forms of RuBisCO, together with ATP citrate lyase genes in the rTCA cycle, increase with distance from the active hydrothermal centres and decrease with sediment depth. Clustering of RuBisCO Form II with a highly prevalent Zetaproteobacteria 16S rRNA gene density infers that ironoxidizing bacteria contribute significantly to the sediment CBB cycle gene content. Three clusters form from different microbial guilds, each one encompassing one gene involved in CO2 fixation, aside from sulfate reduction. Our study suggests that the microbially mediated CBB cycle drives carbon fixation in the Spathi Bay sediments that are characterized by diffuse hydrothermal activity, high CO2, As emissions and chemically reduced fluids. This study highlights the breadth of conditions influencing the biogeochemistry in shallow CO2-rich hydrothermal systems and the importance of coupling highly specific process indicators to elucidate the complexity of carbon cycling in these ecosystems.

  • 144.
    Callac, Nolwenn
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Université de Bretagne Occidentale, France.
    Rouxel, Olivier
    Lesongeur, Francoise
    Liorzou, Celine
    Bollinger, Claire
    Pignet, Patricia
    Cheron, Sandrine
    Fouquet, Yves
    Rommevaux-Jestin, Celine
    Godfroy, Anne
    Biogeochemical insights into microbe-mineral-fluid interactions in hydrothermal chimneys using enrichment culture2015In: Extremophiles, ISSN 1431-0651, E-ISSN 1433-4909, Vol. 19, no 3, p. 597-617Article in journal (Refereed)
    Abstract [en]

    Active hydrothermal chimneys host diverse microbial communities exhibiting various metabolisms including those involved in various biogeochemical cycles. To investigate microbe-mineral-fluid interactions in hydrothermal chimney and the driver of microbial diversity, a cultural approach using a gas-lift bioreactor was chosen. An enrichment culture was performed using crushed active chimney sample as inoculum and diluted hydrothermal fluid from the same vent as culture medium. Daily sampling provided time-series access to active microbial diversity and medium composition. Active archaeal and bacterial communities consisted mainly of sulfur, sulfate and iron reducers and hydrogen oxidizers with the detection of Thermococcus, Archaeoglobus, Geoglobus, Sulfurimonas and Thermotoga sequences. The simultaneous presence of active Geoglobus sp. and Archaeoglobus sp. argues against competition for available carbon sources and electron donors between sulfate and iron reducers at high temperature. This approach allowed the cultivation of microbial populations that were under-represented in the initial environmental sample. The microbial communities are heterogeneously distributed within the gas-lift bioreactor; it is unlikely that bulk mineralogy or fluid chemistry is the drivers of microbial community structure. Instead, we propose that micro-environmental niche characteristics, created by the interaction between the mineral grains and the fluid chemistry, are the main drivers of microbial diversity in natural systems.

  • 145. Campeau, Audrey
    et al.
    Wallin, Marcus B.
    Giesler, Reiner
    Löfgren, Stefan
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Schiff, Sherry
    Venkiteswaran, Jason J.
    Bishop, Kevin
    Multiple sources and sinks of dissolved inorganic carbon across Swedish streams, refocusing the lens of stable C isotopes2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 9158Article in journal (Refereed)
    Abstract [en]

    It is well established that stream dissolved inorganic carbon (DIC) fluxes play a central role in the global C cycle, yet the sources of stream DIC remain to a large extent unresolved. Here, we explore large-scale patterns in delta C-13-DIC from streams across Sweden to separate and further quantify the sources and sinks of stream DIC. We found that stream DIC is governed by a variety of sources and sinks including biogenic and geogenic sources, CO2 evasion, as well as in-stream processes. Although soil respiration was the main source of DIC across all streams, a geogenic DIC influence was identified in the northernmost region. All streams were affected by various degrees of atmospheric CO2 evasion, but residual variance in delta C-13-DIC also indicated a significant influence of in-stream metabolism and anaerobic processes. Due to those multiple sources and sinks, we emphasize that simply quantifying aquatic DIC fluxes will not be sufficient to characterise their role in the global C cycle.

  • 146. Capraro, L.
    et al.
    Massari, F.
    Rio, D.
    Fornaciari, E.
    Backman, Jan
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Channell, J. E. T.
    Macri, P.
    Prosser, G.
    Speranza, F.
    Chronology of the Lower-Middle Pleistocene succession of the south-western part of the Crotone Basin (Calabria, Southern Italy)2011In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 30, no 9-10, p. 1185-1200Article in journal (Refereed)
    Abstract [en]

    Biostratigraphy based on calcareous nannofossils, integrated by magnetostratigraphic, geochronological and isotopic data, allowed establishing a precise chronological framework for the Pleistocene succession within the south-western sector of the Crotone Basin (Calabria, Southern Italy), where the Pliocene-Pleistocene global stratotype section and point is defined, thus demonstrating that sedimentation was quasi-continuous during most of the Lower and Middle Pleistocene. At a large scale, the Pleistocene succession in this sector of the Crotone Basin is characterized by an evident shallowing-upwards trend, showing facies changes from bathyal to shelfal to littoral/continental. However, comparison between adjacent sectors within the investigated area demonstrates that stratigraphic architectures change vastly on very short distances. Our chronological constraints indicate that such changes in sedimentation styles probably occurred in response to differential subsidence rates, which originated tectonically-controlled synsedimentary structures where accommodation space and sediment yield were allotted unevenly. This articulated physiography led to striking differences in the overall thicknesses and organization of Pleistocene stratigraphies and, eventually, to a distinct diachroneity in the first appearance of shallow-marine deposits. In addition, superimposed are complex interplays between regional and local tectonics, eustasy and orbitally-forced climate changes. These interactions have been highlighted by the oxygen isotope stratigraphy established for a part of the studied succession, which is likely to document almost continuously the interval from Marine Isotope Stage (MIS) 26 to MIS 17. In its younger part (post-MIS 17), chronological ties are poor, as the succession is dominated by shallow-water to continental deposits showing a prominent organization into cyclothems. Nevertheless, based on the chronology of the underlying units, it is feasible that basin infill ended during MIS 15-MIS 14 times.

  • 147.
    Carlsson, Diana
    Stockholm University, Faculty of Science, Department of Geological Sciences. Department of Palaeobiology, Swedish Museum of Natural History.
    Geological and geochemical conditions controlling microbial colonization in igneous oceanic crust; implications for life on Mars2017Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The igneous oceanic crust has long been considered as an inhabitable place on Earth. Research has revealed that deep-sea sediments, and even the igneous crust underneath it, harbours vast quantities of microbial life, and that prokaryotic organisms in the deep- biosphere may contain as much carbon as all plant life found at the Earth’s surface. Detailed studies of the microbiological ecosystem in the deep-biosphere should therefore give us infor- mation about past, present and future environments, since changes in the ocean chemistry, temperatures, topography, and climate have a direct impact on the biotic components, such as diversity, abundance, and morphology.

    This study has focused on fossilised microbes found in open and sealed pore spaces in pillow lavas from the Troodos ophiolite in Cyprus. The aim was to understand the geological and geochemical conditions that are needed for microbes to survive under the extreme condi- tions found in the oceanic crust, and was done by investigating the surrounding mineralogy as well as the morphology and chemical composition of fossilized microbes. Quantitative fluid composition, temperature and pH during the time of microbial colonization, as well as fossilisation was evaluated based on the mineralogy and fluid inclusions found in secondary calcite veins.

    In this study, it is found that the microbial abundance increases towards higher tempera- tures, more pervasive hydrothermal alteration, and that colonization is favoured in volcanic rocks that are in close association with ore deposits. For their metabolism, they seem to to have preferred colonization around K and Fe rich minerals, vesicle and veins that have had a high abundance of fluids. Fossilization of the microbes has mainly been done by Fe and Mg rich montmorillonite, where some fungi show precipitated, or preserved, goethite in the central strand, and rutile crystals in vacant sites in the clay. Elements such as Mg, Ca, and Na seems to have come in with the oceanic water, and Ti with the primordial water. Fossilization seems to have been initiated during temperature and pH changes of later hydrothermal activity, where at least three hydrothermal events can be seen in total in the samples.

    1. Temperatures <50°C precipitated celadonite and saponite in open vesicles and veins, as well as introduced microbial life into open pore spaces.

    2. A later second hydrothermal event with temperatures <100°C precipitated Na and Ca zeolite, increasing the pH from 4-6 to 7-8, stressing the microbes into starting to adhere clays as possible protection.

    3. Fossilization was finalized with a last hydrothermal event with temperatures >75°C, precipitating Ca carbonates, increasing pH to >8-9, as well as making the environment inhabitable for the microbes.

    From this study, it is concluded that microbial colonization in basaltic pillow lavas favours open pore spaces that have had access to a high abundance of fluids, giving rise to more dissolved elements. These elements have come from both the oceanic and primordial water, as well as the host rock, and are essential for the microbes’ metabolism. The microbes seem to prefer temperatures <50°C and a pH below 7-8. 

  • 148.
    Carlsson, Diana
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Petrographic study of high-grade gneisses, Halland area2014Student paper other, 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This is a petrographic study of high-grade gneisses in the Halland area, Sweden. During bedrock mapping by the Swedish Geological Survey, three principal petrographically distinct gneiss domains have been recognized: the Skene, Varberg, and Halmstad domain. The purpose is to compare the petrographic textures and minerals that occur within this area, to determine possible metamorphic differences between the domains. Within this study, the petrographic descriptions will also be compared with technical data made on the gneisses, to evaluate if the gneisses could be used as aggregates, in for example road materials. The study was conducted in the south-western part of Sweden, in the lower Eastern Segment. A total of 19 thin samples from 10 different localities wad studied under an optical microscope, of which four localities are active quarries. The Skene domain orthogneisses typically have blue-green hornblende, dark brown/green brown biotite, no antiperthitic plagioclase, no perthitic orthoclase, microcline with tartan twinning, titanite and opaque minerals but no garnet are present. The textures of the Skene samples are inequigranular to seriate with both polygonal and interlobate grain boundaries. The Varberg domain orthogneisses typically have brown-green hornblende, red-brown biotite, antiperthitic plagioclase, perthitic orthoclase, no microcline with tartan twinning, garnet and opaque minerals are present. The texture of the Varberg samples are seriate with both polygonal and interlobate grain boundaries. The Halmstad domain orthogneisses typically have brown-green hornblende, red-brown biotite, antiperthitic plagioclase, no perthitic orthoclase and no microcline with tartan twinning, opaque minerals and occasionally garnet and epidote are present. The textures of the Halmstad samples are seriate to inequigranular with both polygonal and interlobate grain boundaries. From the study, it is concluded that even though the protolith classifications plot fairly similar, the metamorphic overprint seems to differ between the domains. From hydrous conditions in the amphibolite facies in the Skene gneisses, anhydrous conditions in the amphibolite to granulite facies in the Varberg gneisses, to anhydrous conditions in the amphibolite to granulite facies in the Halmstad gneisses. The Skene and Halmstad gneisses have a more pervasive recrystallization than the Varberg gneisses. From the petrographic study, rocks suitable for road aggregate production correlate with the presence of antiperthitic plagioclase and the absence of tartan twinning and titanite. Furthermore, higher sericitization has been correlated to higher technical values for road aggregates, which is inconsistent with previous work. This could be due to the Halland area being subjected to several metamorphic events, where prograde and retrograde reactions have affected the plagioclase differently, than in areas from previous work. It is concluded that the Varberg and the Halmstad gneisses seems to have the best properties for production of aggregates for roads while the Skene gneisses unsuitable for this purpose. This could be due to the fact that the Skene domain have a higher retrogression in comparison to the other domains.

  • 149.
    Carlsson, Diana
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Qualitative and quantitative petrography of meta-mafic rocks at Ölme, in the Eastern Segment of the Sveconorwegian orogen2015Independent thesis Basic level (degree of Bachelor), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Meta-mafic intrusions with an intrusion age of 1.6-0.9 Ga are found along a north-south trend in theTransitional section of the Eastern Segment in Sweden. These intrusions are garnet-bearing and thus anexception to other meta-mafic intrusions found in Sweden. Meta-mafic intrusions that are garnet-bearingare usually found in the Caledonides to the northeast and in the south west of Sweden where the pressureshave been naturally high due to orogenic events or subduction.The study was conducted on these intrusions around the community of Ölme, to understand themetamorphic and metasomatic history of the area. The focus lies on the transition from magmaticgabbroic intrusions to metamorphosed metagabbros and highly foliated garnet-amphibolites. AveragePT estimates was calculated using THERMOCALC and classical geothermobarometry, so that acomparison between the qualitative and quantitative data could be made.The study indicates metamorphism at amphibolite to upper amphibolite facies conditionsfor the metagabbros and the garnet-amphibolites.Average PT-estimates for the garnet-amphibolites gives metamorphic peak temperatures of 680°-730° Cwith pressures of 9.0-11.0 kbar at the Träfors locality, and metamorphic peak temperatures of 660°-770° Cwith pressures of 9.5-11.0 kbar at the Skråkvik locality. These results are comparable to research donefurther to the south on similar intrusions, with temperatures of 700° C and pressures of 10 kbar.It is concluded that the meta-mafic intrusions at the Skråkvik locality have been metamorphosed in adry system, in contrast to the Träfors locality which seems to have been affected by more pervasiveretrograde metamorphism and fluid-rock interaction. It is also concluded that mafic intrusionscan preserve their magmatic textures even under high pressure conditions.

  • 150.
    Carugati, Gabriele
    et al.
    University of Insubria Department of Chemical and Environmental Science 22100 Como Italy.
    Rauch, Sebastien
    Chalmers University of Technology Water Environment Technology, Department of Civil and Environmental Engineering .
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Experimental assessment of a large sample cell for laser ablation-ICP-MS, and its application to sediment core micro-analysis2010In: Mikrochimica Acta, ISSN 0026-3672, E-ISSN 1436-5073, Vol. 170, no 1-2, p. 39-45Article in journal (Refereed)
    Abstract [en]

    The coupling of laser ablation (LA) to inductively coupled plasma-mass spectrometry (ICP-MS) enables the direct analysis of solid samples with micrometric resolution. Analysis is often restricted to relatively small samples owing to the dimensions of conventional ablation cells. Here, we assess the performance of a large rectangular, commercially-available sample cell which enables analysis over a 10.2 x 5.2 cm(2) area. Comparison with the conventional cell shows a small to moderate performance decrease for the large cell resulting from the dilution of ablated particles in a larger volume with a 4-31% lower signal output and longer signal tailings. The performance of this cell is however sufficient for the determination of both major and trace elements in many kinds of samples. The applicability of the large cell LA-ICP-MS setup was demonstrated by the determination of Al, Si, Mn, Fe, Cu, Zn Pb and U in sediment core sections at a resolution of 0.6 mm. Detection limits for sediment analysis were 7 mg Al kg(-1), 68 mg Si kg(-1), 0.5 mg Mn kg(-1), 20 mg Fe kg(-1), 0.2 mg Cu kg(-1), 0.3 mg Zn kg(-1), 0.08 mg Pb kg(-1) and 0.003 mg U kg(-1). Cyclic patterns, which would have been overlooked by conventional analysis at cm resolution, were observed in analysed sediments. This study demonstrates the potential of LA-ICP-MS in environmental analysis, with the large sample cell setup offering the possibility to analyse a wider range of samples without sectioning.

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