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  • 201.
    Evers, Mariele
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Nyberg, Lars
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Coherence and inconsistency of European instruments for integrated river basin management2011Conference paper (Refereed)
    Abstract [en]

    Room for the River projects increase the level of flood protection by enlarging theconveyance and reducing hydraulic roughness. As a consequence sediment transportcapacities are reduced as well, causing shoals and a reduced navigation channel. Thelarge number of Room for the River measures and European Framework Directive(WFD) measures, aiming at an increase of the ecological potential (e.g. sidechannels), will result in much dredging, if no structural measures are implemented.The expected amount of dredging will be too large to handle. Therefore research isexecuted to limit the dredging effort by executing mitigating measures. Old principlesof irrigation are given new attention to be applied to side channels and channelsbetween longitudinal dams and the river bank ('bank channels'). A new round ofnormalisation works may be necessary, to limit dredging activities. Boundaryconditions for river managemant are stopping autonomous bed degradation andeconomic sustainability of sets of measures that can cope with the hydromorphologicconsequences of the Room for the River and WFD measures

  • 202.
    Evers, Mariele
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Centre for Climate and Safety. Bonn University.
    Nyberg, Lars
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Svedung, Inge
    Karlstad University, Faculty of Social and Life Sciences, Centre for Climate and Safety.
    Reducing flood risk by integrative land use planning2012In: Proceedings of the 43rd ESReDA seminar on land use planning and risk-informed decision making. Saint-Étienne-du Rouvray, France, Oct 22-23, 2012, 2012Conference paper (Refereed)
  • 203.
    Fagerlind, David
    Stockholm University, Faculty of Science, Stockholm Resilience Centre.
    Deconstructing the Great Acceleration2018Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    The Anthropocene is characterized by a strong human influence on the Earth System that is threatening the future prosperity of human societies. A mid-20th century onset of the Anthropocene is being proposed supported by the global phenomenon the Great Acceleration, but much concern has been raised that defining the Anthropocene based on global averages fails to recognize the massive inequalities in humanity’s contribution to current pressures on the Earth System. This study uses increase in growth rate as in indication of system change and conducts a statistical analysis to determine the largest change in the socio-economic domain of the Earth System on both a global and national level. The aim is to examine the empirical support for an unequal Anthropocene from a systems perspective. 814 of these events are identified across all the Great Acceleration indicators. The magnitude of the changes is typically large, with the growth rate increasing by more than 100% in 86% of the identified events. The findings suggest that while there is good evidence for a substantial change in the socio-economic domain of the Earth System the mid-20th century it is not the result of a globally synchronous event, but rather the culmination of a gradual process that display large temporal disparities with these system changes moving like waves across the Earth. The observed disparities show striking similarities to current developmental status suggesting that when deconstructed, the Great Acceleration can be used both to support global patterns and to illustrate inequalities between countries and people, making it a powerful tool to communicate the many facets of the Anthropocene.

  • 204.
    Fanting, Gong
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Linking socio-economic factors to urban growth by using night timelight imagery from 1992 to 2012: A case study in Beijing2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In recent decades, the night lights data of the Earth’s surface derived from the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) have been used to detect the human settlements and human activities, because the DMSP/OLS data is able to supply the information about the urban areas  and non-urban areas on the Earth which means it is more suitable for urban studies than usual satellite imagery data.

     

    The urban development is closed linked to the human society development. Therefore, studies of urban development will help people to understand how the urban changed and predict the urban change. The aim of this study was to detect Beijing’s urban development from 1992 to 2012, and find the contributions to the urban sprawl from socio-economic factors. Based on this objective, the main dataset used in this thesis was night lights images derived from the DMSP/OLS which was detected from  1992 to 2012. Due to the lacking of on-board calibration on OLS, and the over-glow of the lights resources, the information about the night lights cannot be extracted directly. Before any process, the night lights images should be calibrated. There is a method to calibrate the night light images which is called intercalibration. It is a second order regression model based method to find the related digital number values. Therefore, intercalibration was employed, and the threshold values were determined to extract urban areas in this study. Threshold value is useful for diffusing the over-glow effect, and finding the urban areas from the DMSP/OLS data. The methods to determine the threshold value in this thesis are empirical threshold method, sudden jump detection method, statistic data comparison method and k-mean clustering method. In addition, 13 socio-economic factors which included gross domestic product, urban population, permanent population, total energy consumption and so on were used to build the regression model. The contributions from these factors to the sum of the Beijing’s lights were found based on modeling.

     

    The results of this thesis are positive. The intercalibration was successful and all the DMSP/OLS data used in this study were calibrated. And then, the appropriate threshold values to extract the urban areas were figured out. The achieved urban areas were compared to the satellite images and the result showed that the urban areas were useful. During the time certain factors used in this study, such as mobile phone users, possession of civil vehicles, GDP, three positively highest contributed to urban development were close to 23%, 8% and 9%, respectively.

  • 205.
    Farineau, Anne
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Diamonds in the Rough: Remote predictive mapping using multispectral satellite imagery for kimberlite exploration on northeast Banks Island, NT2015Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    This study demonstrates the use and limitations of Remote Predictive Mapping (RPM) as an aid to kimberlite exploration on northeast Banks Island, Northwest Territories, Canada. It focuses on the effectiveness of ASTER and Landsat 8 optical multi-spectral satellite imagery for discerning the spectral properties of different bedrock and surficial materials that outcrop or blanket the regional terrain. Statistical algorithms and digital image enhancement techniques were used to highlight patterns and anomalies within each scene in order to determine the range of materials and specific deposits (e.g., till, glaciofluvial) that could be the source of recovered kimberlite indicator minerals (KIMs) from stream sediment samples. Field inspection and sampling were in part guided by these patterns and anomalies. During the course of fieldwork, numerous outliers of the Pliocene Beaufort Formation fluvial sand and gravel deposits were discovered on upland surfaces in northeastern Banks Island. These outcrops sit well beyond (east) of any previous mapped Beaufort Fm. extents, and it is hypothesized that as they exist within catchments where Industry has recovered KIMs, they could be a source of bedrock-inherited KIMs. Field observations and spectral sampling using a portable spectroradiometer were integrated with ASTER and Landsat data to predict the spatial extents of Beaufort Fm. deposits. Using test and field-validated Beaufort Fm. sites, Spectral Angle Mapper (SAM) whole pixel spectral target detection was compared with Matched Filtering (MF), Mixture-Tuned Matched Filtering (MTMF) sub-pixel spectral target detection methods and Parallelepiped classification for ASTER scenes 1228 and 0686.  Each method was also performed on ASTER scene 0541 to assess the potential for Quaternary sediment discrimination, using pixel ROIs from a field-validated glaciolacustrine deposit. The sub-pixel sensitivity of the MF/MTMF methods was determined to have the best potential for the discrimination of surficial materials on NE Banks Island.  MF/MTMF also had the best results for discriminating Beaufort Fm. in scene 1228, but Parallelepiped classification was the most effective prediction method for scene 0686. These inconsistent results indicate spectral variability between Beaufort Fm. sites, a consideration for any further study in the region.  

  • 206. Faucherre, Samuel
    et al.
    Jørgensen, Christian Juncher
    Blok, Daan
    Weiss, Niels
    Siewert, Matthias Benjamin
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Physical Geography, Stockholm University,Stockholm, Sweden.
    Bang-Andreasen, Toke
    Hugelius, Gustaf
    Kuhry, Peter
    Elberling, Bo
    Short and Long-Term Controls on Active Layer and Permafrost Carbon Turnover Across the Arctic2018In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 123, no 2, p. 372-390Article in journal (Refereed)
    Abstract [en]

    Decomposition of soil organic matter (SOM) in permafrost terrain and the production of greenhouse gases is a key factor for understanding climate change-carbon feedbacks. Previous studies have shown that SOM decomposition is mostly controlled by soil temperature, soil moisture, and carbon-nitrogen ratio (C:N). However, focus has generally been on site-specific processes and little is known about variations in the controls on SOM decomposition across Arctic sites. For assessing SOM decomposition, we retrieved 241 samples from 101 soil profiles across three contrasting Arctic regions and incubated them in the laboratory under aerobic conditions. We assessed soil carbon losses (C-loss) five times during a 1year incubation. The incubated material consisted of near-surface active layer (AL(NS)), subsurface active layer (AL(SS)), peat, and permafrost samples. Samples were analyzed for carbon, nitrogen, water content, C-13, N-15, and dry bulk density (DBD). While no significant differences were observed between total AL(SS) and permafrost C-loss over 1year incubation (2.32.4% and 2.51.5% C-loss, respectively), AL(NS) samples showed higher C-loss (7.94.2%). DBD was the best explanatory parameter for active layer C-loss across sites. Additionally, results of permafrost samples show that C:N ratio can be used to characterize initial C-loss between sites. This data set on the influence of abiotic parameter on microbial SOM decomposition can improve model simulations of Arctic soil CO2 production by providing representative mean values of CO2 production rates and identifying standard parameters or proxies for upscaling potential CO2 production from site to regional scales.

  • 207. Fenn, Kaja
    et al.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Bird, Anna
    Limonta, Mara
    Rittner, Martin
    Vermeesch, Pieter
    Ando, Sergio
    Garzanti, Eduardo
    Lu, Huayu
    Zhang, Hanzhi
    Lin, Zeng
    Insights into the provenance of the Chinese Loess Plateau from joint zircon U-Pb and garnet geochemical analysis of last glacial loess2018In: Quaternary Research, ISSN 0033-5894, E-ISSN 1096-0287, Vol. 89, no 3, p. 645-659Article in journal (Refereed)
    Abstract [en]

    The Chinese Loess Plateau, the world's largest and oldest loess record, preserves evidence of Asia's long-term dust source dynamics, but there is uncertainty over the source of the deposits. Recent single-grain detrital zircon U-Pb age analysis has progressed this issue, but debates remain about source changes, and the generation and interpretation of zircon data. To address this, we analyze different groupings of new and existing datasets from the Loess Plateau and potential sources. We also present the results of a first high resolution sampling, multi-proxy provenance analysis of Beiguoyuan loess using U-Pb dating of detrital zircons and detrital garnet geochemistry. The data shows that some small source differences seem to exist between different areas on the Loess Plateau. However, sediment source appears to be unchanging between loess and palaeosols, supporting a recent material recycling hypothesis. Our zircon and garnet data demonstrates, however, that Beiguoyuan experienced a temporary, abrupt source shift during the last glacial maximum, implying that local dust sources became periodically active during the Quaternary. Our results highlight that grouping data to achieve bigger datasets could cause identification of misleading trends. Additionally, we suggest that multi-proxy single-grain approaches are required to gain further insight into Chinese Loess Plateau dust sources.

  • 208.
    Figueiredo, Bruno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley National Laboratory, Berkeley USA.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Georg, Lindgren
    Swedish Radiation Safety Authority, Stockholm, Sweden.
    Review: The state-of-art of sparse channel models and their applicability to performance assessment of radioactive waste repositories in fractured crystalline formations2016In: Hydrogeology Journal, ISSN 1431-2174, E-ISSN 1435-0157, Vol. 24, no 7, p. 1607-1622Article in journal (Other academic)
    Abstract [en]

    Laboratory and field experiments done on fractured rock show that flow and solute transport often occur along flow channels. ‘Sparse channels’ refers to the case where these channels are characterised by flow in long flow paths separated from each other by large spacings relative to the size of flow domain. A literature study is presented that brings together information useful to assess whether a sparse-channel network concept is an appropriate representation of the flow system in tight fractured rock of low transmissivity, such as that around a nuclear waste repository in deep crystalline rocks. A number of observations are made in this review. First, conventional fracture network models may lead to inaccurate results for flow and solute transport in tight fractured rocks. Secondly, a flow dimension of 1, as determined by the analysis of pressure data in well testing, may be indicative of channelised flow, but such interpretation is not unique or definitive. Thirdly, in sparse channels, the percolation may be more influenced by the fracture shape than the fracture size and orientation but further studies are needed. Fourthly, the migration of radionuclides from a waste canister in a repository to the biosphere may be strongly influenced by the type of model used (e.g. discrete fracture network, channel model). Fifthly, the determination of appropriateness of representing an in situ flow system by a sparse-channel network model needs parameters usually neglected in site characterisation, such as the density of channels or fracture intersections.

  • 209.
    Figueiredo, Bruno
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Tsang, Chin-Fu
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Lawrence Berkeley National Laboratory, Berkeley, California.
    Rutqvist, Jonny
    Lawrence Berkeley National Laboratory.
    Niemi, Auli
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Study of hydraulic fracturing processes in shale formations with complex geological settings2017In: Journal of Petroleum Science and Engineering, ISSN 0920-4105, E-ISSN 1873-4715, Vol. 152, p. 361-374Article in journal (Refereed)
    Abstract [en]

    Hydraulic fracturing has been applied to extract gas from shale-gas reservoirs. Complicated geological settings,such as spatial variability of the rock mass properties, local heterogeneities, complex in situ stress field, and preexistingbedding planes and faults, could make hydraulic fracturing a challenging task. In order to effectivelyand economically recover gas from such reservoirs, it is crucial to explore how hydraulic fracturing performs insuch complex geological settings. For this purpose, numerical modelling plays an important role because suchconditions cannot be reproduced by laboratory experiments. This paper focuses on the analysis of the influenceof confining formations and pre-existing bedding planes and faults on the hydraulically-induced propagation ofa vertical fracture, which will be called injection fracture, in a shale-gas reservoir. An elastic-brittle model basedon material property degradation was implemented in a 2D finite-difference scheme and used for rock elementssubjected to tension and shear failure. A base case is considered, in which the ratio SR between the magnitudesof the horizontal and vertical stresses, the permeability kc of the confining formations, the elastic modulus Epand initial permeability kp of the bedding plane and the initial fault permeability kF are fixed at reasonablevalues. In addition, the influence of multiple bedding planes, is investigated. Changes in pore pressure andpermeability due to high pressure injection lasting 2 h were analysed. Results show that in our case during theinjection period the fracture reaches the confining formations and if the permeability of those layers issignificantly larger than that of the shale, the pore pressure at the extended fracture tip decreases and fracturepropagation becomes slower. After shut-in, the pore pressure decreases more and the fracture does notpropagate any more. For bedding planes oriented perpendicular to the maximum principal stress direction andwith the same elastic properties as the shale formation, results were found not to be influenced by theirpresence. In such a scenario, the impact of multiple bedding planes on fracture propagation is negligible. On theother hand, a bedding plane softer than the surrounding shale formation leads to a fracture propagationasymmetrical vertically with respect to the centre of the injection fracture with a more limited upward fracturepropagation. A pre-existing fault leads to a decrease in fracture propagation because of fault reactivation withshear failure. This results in a smaller increase in injection fracture permeability and a slight higher injectionpressure than that observed without the fault. Overall, results of a sensitivity analysis show that fracturepropagation is influenced by the stress ratio SR, the permeability kc of the confining formations and the initialpermeability kp of the bedding plane more than the other major parameters.

    The full text will be freely available from 2019-03-07 08:00
  • 210.
    Fiola, Markus L.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Influence of Sample Preparation on Portable XRF-analyses of Aeolian Sediments: a Case Study2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The geochemical composition of aeolian sediments like windblown dust particles is of major importance for the exploration of dust origin and weathering conditions. This allows for the reconstruction of dust transport pathways and thus wind directions and palaeoclimate conditions. The loess deposits of the Carpathian Basin are the most complete terrestrial sediment climate archive in Europe, yet their development is still not fully understood. With the advancement of accurate field portable X-ray fluorescence (XRF) spectrometers, field applications have become possible, allowing in-situ geochemical analysis and potential advances in understanding the source of Carpathian Basin loess. However, previous work has failed to address the question of sample preparation and device interchangeability in the context of loess analyses.

    This study uses both Bruker Tracer 5i and Titan S1, as well as secondary data obtained with an Ametek SpectroXepos, to investigate sample preparation influences on aeolian sediment samples from Irig (Serbia) and Madaras (Hungary). Results showed that although absolute values deviate substantially between devices using different calibrations, some elemental ratios like Ca/Ti or Rb/Sr can still be compared when only relative changes are interpreted. Absolute concentrations of light elements, such as magnesium and calcium, were strongly influenced by milling or acid treatment. Absolute concentrations of light elements were also strongly influenced by changes in sample moisture, whereas the effect on the absolute concentrations of heavier elements was comparably small. Results also show that the influence of sample moisture needs to be considered when computing paleoclimatic indicator ratios involving aluminium or strontium, as sample moisture has a strong effect on the absolute concentration of these elements.

    Most deviations in measured absolute concentrations between untreated and prepared samples were attributed to the special nature of compositional data and could be removed through the application of additive or centred log-ratio transformations. This highlights the importance of considering the closure effect, using proper and robust statistical analyses in sediment provenance research.The geochemical data provided in this study shed light on dust provenance and the paleoclimatic development of the southeast European loess and highlight the effects of analysis technique on interpretation of this geochemical data.

    The full text will be freely available from 2019-08-01 08:01
  • 211. Fontorbe, G.
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, C. L.
    Hendry, K. R.
    Conley, D. J.
    A silicon depleted North Atlantic since the Palaeogene: Evidence from sponge and radiolarian silicon isotopes2016In: Earth and Planetary Science Letters, Vol. 453, p. 67-77Article in journal (Refereed)
    Abstract [en]

    Despite being one of Earth's major geochemical cycles, the evolution of the silicon cycle has received little attention and changes in oceanic dissolved silica (DSi) concentration through geologic time remain poorly constrained. Silicon isotope ratios (expressed as delta Si-30) in marine microfossils are becoming increasingly recognised for their ability to provide insight into silicon cycling. In particular, the delta Si-30 of siliceous sponge spicules has been demonstrated to be a useful proxy for past DSi concentrations. We analysed delta Si-30 in radiolarian tests and sponge spicules from the Blake Nose Palaeoceanographic Transect (ODP Leg 171B) spanning the Palaeocene-Eocene (ca. 60-30 Ma). Our delta Si-30 results range from +0.32 to +1.67 parts per thousand and -0.48 to +0.63 parts per thousand for the radiolarian and sponge records, respectively. Using an established relationship between ambient dissolved Si (DSi) concentrations and the magnitude of silicon isotope fractionation in siliceous sponges, we demonstrate that the Western North Atlantic was DSi deplete during the Palaeocene-Eocene throughout the water column, a conclusion that is robust to a range of assumptions and uncertainties. These data can constitute constraints on reconstructions of past-ocean circulation. Previous work has suggested ocean DSi concentrations were higher than modern ocean concentrations prior to the Cenozoic and has posited a drawdown during the Early Palaeogene due to the evolutionary expansion of diatoms. Our results challenge such an interpretation. We suggest here that if such a global decrease in oceanic DSi concentrations occurred, it must predate 60 Ma. (C) 2016 The Authors. Published by Elsevier B.V.

  • 212. Fontorbe, Guillaume
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, Christina
    Hendry, Kate
    Carstensen, Jacob
    Conley, Daniel
    Enrichment of dissolved silica in the deep equatorial Pacific during the Eocene-Oligocene2017In: Paleoceanography, ISSN 0883-8305, E-ISSN 1944-9186, Vol. 32, p. 848-863Article in journal (Refereed)
    Abstract [en]

    Silicon isotope ratios (expressed as δ30Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ30Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene (~50–23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ30Si. The δ30Si values range from 3.16 to +0.18‰ and from 0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ30Si values around 37 Ma. The shift in radiolarian δ30Si is interpreted as a consequence of changes in the δ30Si of source DSi to the region. The decrease in sponge δ30Si is interpreted as a transition from low DSi concentrations to higher DSi concentrations, most likely related to the shift toward a solely Southern Ocean source of deep water in the Pacific during the Paleogene that has been suggested by results from paleoceanographic tracers such as neodymium and carbon isotopes. Sponge δ30Si provides relatively direct information about the nutrient content of deep water and is a useful complement to other tracers of deep water circulation in the oceans of the past. 

  • 213.
    Fors, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Jalilehvand, Farideh
    Risberg, Emiliana Damian
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Bjordal, Charlotte
    Phillips, Ebba
    Sandström, Magnus
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sulfur and iron analyses of marine archaeological wood in shipwrecks from the Baltic Sea and Scandinavian waters2012In: Journal of Archaeological Science, ISSN 0305-4403, E-ISSN 1095-9238, Vol. 39, no 7, p. 2521-2532Article in journal (Refereed)
    Abstract [en]

    Analyses of marine archaeological wood from shipwrecks in the Baltic Sea area, Kronan, Riksnyckeln, Tattran, the Puck Bay Boat and the Ghost wreck, and at the Scandinavian West coast, the Gota wreck, Stora Sofia and the Viking shipwrecks of Skuldelev, show accumulation of sulfur compounds. The penetration profiles of sulfur and iron into the wood and the speciation of characteristic sulfur groups were evaluated by combining X-ray spectroscopic analyses, in particular S K-edge XANES (X-ray absorption near edge structure) and X-ray fluorescence, with ESCA and elemental analyses. The combined analyses support the hypothesis that hydrogen sulfide produced by sulfate-reducing bacteria reacts and accumulates at low iron concentration mainly as organically bound sulfur, which as in previous studies was found by X-ray spectro-microscopy to accumulate in lignin-rich parts of the wood cell walls. The presence of iron(II) ions from corroding iron promotes formation of pyrite and other iron(II) sulfides, which easily oxidise in aerobic conditions with high humidity. No significant differences in sulfur and iron accumulation were found in wood from shipwrecks in the east coast brackish water and the west coast seawater. Sediments from three wreck sites, the Gota wreck, Stora Sofia and Kronan, were analyzed to a depth of a few decimeters and showed especially at the Stora Sofia high sulfur concentrations, exceeding 3 mass%. S K-edge XANES analyses of the sediments showed mainly reduced forms of sulfur, in particular pyrite and iron(II) sulfides together with elemental sulfur.

  • 214.
    Forsström, Anna
    Swedish Museum of Natural History, Department of Geology. Linköping University.
    Extraction and determination of Hf in water using a chelating resin and ICP-AES2014Student paper other, 10 HE creditsStudent thesis
  • 215.
    Franzen, L. G.
    et al.
    Univ Gothenburg, Dept Earth Sci, SE-40530 Gothenburg, Sweden..
    Malmgren, Björn A.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Microscopic charcoal and tar (CHAT) particles in peat: a 6500-year record of palaeo-fires in southern Sweden2012In: Mires and Peat, ISSN 1819-754X, E-ISSN 1819-754X, Vol. 10, article id 01Article in journal (Refereed)
    Abstract [en]

    Peat stratigraphies of eleven raised bogs in southern Sweden were investigated. Measurements included the occurrence of charcoal and various tar particles. Most of the particles found were microscopic, i.e. 5-100 mu m in diameter. Two distinctly different groups of particles were distinguished: (A) charred fragments of plant tissue and (B) objects formed from tar, which were classified into five sub-groups on the basis of morphology. Both charcoal and tar are indicative of mire and forest fires. We suggest that it is possible to use the different groups of particles as fire regime indicators. Hence, the high frequency of charcoal and tar (CHAT) in the lower parts of the stratigraphies, i.e. in the lower strongly decomposed fen and carr peats that were formed before ca. 4000 cal C-14 BP, could be indicative of intense and frequent local fires. The decreasing abundance of CHAT and the lower relative share of Type A particles within the lower strongly decomposed Sphagnum peat ca. 4000-2500 cal C-14 BP signify a transition from local to regional fires. With a few exceptions, the uppermost weakly decomposed ombrotrophic peats formed after ca. 2500 cal C-14 BP, in which both charcoal and tar are rare, indicate a period of low fire frequency at both local and regional scales. There is no regional variation in the lower material, and it seems that wildfires were common phenomena throughout southern Sweden during the first few thousand years after peat formation began 6-8000 years ago. From a climatological point of view, the mass occurrence of CHAT in the lower parts of the profiles indicates a warm and dry Mid Holocene with frequent and widespread wildfires, and a moist and cool Late Holocene with more sporadic fires. Spectral analysis of the entire dataset shows significant periodicities of 610, 70, 30, 21, 17 and 14 years, the two most significant being 14 and 70 years.

  • 216.
    Freitas, Flavio L. M.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Sparovek, Gerd
    University of São Paulo, Soil Dep..
    Mörtberg, Ulla
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Silveira, Semida
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Energy and Climate Studies, ECS.
    Klug, Israel
    Food and Agriculture Organization of United Nations, Nutrition and Food Systems Division.
    Berndes, Göran
    Chalmers University, Energy and Environment.
    Offsetting legal deficits of native vegetation among Brazilian landholders: effects on nature protection and socioeconomic developmentManuscript (preprint) (Other academic)
  • 217.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Revisiting the dissolution of biogenic Si in marine sediments: a key term in the ocean Si budget2017In: Acta Geochimica, ISSN 2096-0956, Vol. 36, no 3, p. 429-432Article in journal (Refereed)
    Abstract [en]

    Of the ~240 × 1012 mol year−1 of biogenic silica (bSi) produced by diatoms and other silicifying organisms, only roughly 3%–4% escapes dissolution to be permanently buried. At the global scale, how, where and why bSi is preserved in sediment is not well understood. To help address this, I compile 6245 porewater dissolved Si concentrations from 453 sediment cores, to derive the concentration gradient at the sediment–water interface and thus diffusive fluxes out of the sediment. These range from <0.002 to 3.4 mol m−2 year−1, and are independent of temperature, depth and latitude. When classified by sediment lithology, predominantly siliceous sediments unsurprisingly have higher mean diffusive fluxes than predominantly calcareous or clay-rich sediment. Combined with the areal extent of these lithologies, the ‘best-guess’ global sedimentary bSi recycling flux is 69 × 1012 mol year−1.

  • 218.
    Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Clymans, Wim
    Conley, Daniel J.
    Amorphous Silica Transport in the Ganges Basin: Implications for Si Delivery to the Oceans2014In: Procedia Earth and Planetary Science, Vol. 10, no 0, p. 271-274Article in journal (Refereed)
    Abstract [en]

    Rivers transport ∽6 x1012 mol yr-1 of dissolved Si (DSi) from the continents to the oceans. They also carry amorphous silica (ASi), solid phases likely to dissolve in seawater. Unfortunately, the magnitude of this flux is poorly constrained at a global scale. We present 92 new ASi values from suspended particulate matter (SPM) from the Ganges basin. Bulk SPM is ∽1.2% ASi, and mean ASi concentrations are ∽65 μM, of comparable magnitude to DSi concentrations. Our results also indicate a) ASi is not evenly distributed in the water column of large rivers, b) the ASi is not a wholly biogenic Si endmember and c) the ASi flux is, to a first order, a function of the SPM load. Our results suggest that the ASi particulate load is much greater than previously believed, rivaling that of the DSi load with important implications for the global Si cycle and oceanic Si isotopic budget.

  • 219.
    Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Clymans, Wim
    Jeppesen, Erik
    Lauridsen, Torben L
    Struyf, Eric
    Conley, Daniel J
    Lack of steady-state in the global biogeochemical Si cycle: emerging evidence from lake Si sequestration2014In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 117, no 2-3, p. 255-277Article in journal (Refereed)
  • 220.
    Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, Christina
    Struyf, Eric
    van Pelt, Dimitri
    Schoelynck, Jonas
    Hudson, Mike Murray
    Gondwe, Mangaliso J.
    Wolski, Piotr
    Mosimane, Keotsheple
    Gray, William
    Schaller, Jörg
    Conley, Daniel J.
    Tracing silicon cycling in the Okavango Delta, a sub-tropical flood-pulse wetland using silicon isotopes2014In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 142, no 0, p. 132-148Article in journal (Refereed)
    Abstract [en]

    Chemical weathering of silicate minerals releases elements into solution whereas the neoformation of secondary minerals works in the opposite direction, potentially confounding estimates of silicate weathering rates. Silicon isotopes (δ30Si) may be a useful tool to investigate these processes. Here, we present 82 δ30Si measurements from surface waters, pore waters, biogenic silica (BSi), clays, sand and vegetation from the Okavango Delta, Botswana, a freshwater sub-tropical, flood-pulse wetland. Hydrologically, the Okavango is dominated by evapotranspiration water losses to the atmosphere. It receives an annual pulse of water that inundates seasonal floodplains, while river baseflow is sufficient to maintain a permanent floodplain. δ30Si in dissolved silica (DSi) in surface waters along a 300 km transect at near-peak flood show a limited range (0.36–1.19‰), implying the Delta is well buffered by a balance of processes adding and removing DSi from the surface water. A key control on DSi concentrations is the uptake, production of BSi and recycling of Si by aquatic vegetation, although the net isotopic effect is necessarily small since all BSi re-dissolves on short timescales. In the sediments, BSi δ30Si (n = 30) ranges from −1.49‰ to +0.31‰ and during dissolution, residual BSi tends towards higher δ30Si. The data permit a field-based estimate of the fractionation associated with BSi dissolution, ε30BSi-DSi = −0.26‰, though it is unclear if this is an artefact of the process of dissolution. Clay δ30Si ranges from −0.97‰ to +0.10‰, (n = 15, mean = −0.31‰) and include the highest values yet published, which we speculate may be due to an equilibrium isotope effect during diagenetic transformation of BSi. Two key trends in surface water DSi δ30Si merit further examination: declining δ30Si in an area roughly corresponding to the permanent floodplains despite net DSi removal, and increasing δ30Si in the area corresponding to the seasonal floodplains. We infer that evaporative enrichment of surface waters creates two contrasting regimes. Chemical weathering of low δ30Si phases releases low δ30Si DSi in the relatively dilute waters of the permanent floodplains, whereas silicon removal via clay formation or vegetation uptake is the dominant process in the more enriched, seasonal floodplains.

  • 221.
    Frings, Patrick J
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Fontorbe, G.
    Clymans, W.
    De La Rocha, C. L.
    Conley, D.J.
    The continental Si cycle and its impact on the ocean Si isotope budget2016In: Chemical Geology, Vol. 425, p. 12-36Article in journal (Refereed)
  • 222.
    Fuchs, Lukas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Strain quantifications in different tectonic scales using numerical modelling2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis focuses on calculation of finite and progressive deformation in different tectonic scales using 2D numerical models with application to natural cases. Essentially, two major tectonic areas have been covered: a) salt tectonics and b) upper mantle deformation due to interaction between the lithosphere and asthenosphere.

    The focus in salt tectonics lies on deformation within down-built diapirs consisting of a source layer feeding a vertical stem. Three deformation regimes have been identified within the salt: (I) a squeezing channel flow underneath the overburden, (II) a corner flow underneath the stem, and (III) a pure channel flow within the stem. The results of the model show that the deformation pattern within the stem of a diapir (e.g. symmetric or asymmetric) can reveal information on different rates of salt supplies from the source layer (e.g. observed in Klodowa-diapir, Poland). Composite rock salt rheology results in strong localization and amplification of the strain along the salt layer boundaries in comparison to Newtonian rock salt. Flow and fold structures of passive marker lines are directly correlated to natural folds within a salt diapir.

    In case of the upper mantle, focus lies on deformation and resulting lattice preferred orientation (LPO) underneath an oceanic plate. Sensitivity of deformation and seismic anisotropy on rheology, grain size (d), temperature (T), and kinematics (v) has been investigated. The results of the model show that the mechanical lithosphere-asthenosphere boundary is strongly controlled by T and less so by v or d. A higher strain concentration within the asthenosphere (e.g. for smaller potential mantle temperatures, higher plate velocities, or smaller d) indicates a weaker coupling between the plate and the underlying mantle, which becomes stronger with the age of the plate. A Poiseuille flow within the asthenosphere, significantly affects the deformation and LPO in the upper mantle. The results of the model show, that deformation in the upper mantle at a certain distance away from the ridge depends on the absolute velocity in the asthenosphere. However, only in cases of a driving upper mantle base does the seismic anisotropy and delay times reach values within the range of natural data.

  • 223.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    Numerical modeling of the effect of composite rheology on internal deformation in down-built diapirs.2015In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 646, p. 79-95Article in journal (Refereed)
    Abstract [en]

    A two-dimensional finite difference code (FDCON) is used to estimate the progressive deformation and the effect of a composite rheology, i.e., Newtonian combined with non-Newtonian, on finite deformation patterns within a down-built diapir. The geometry of the diapir is fixed using two rigid rectangular overburden units which sink into a source layer of a certain viscosity. We have analyzed the progressive deformation within the entire salt layer for a composite rheology and compared them to a standard model with Newtonian rheology (ηs = 1018 Pa s). The composite rheology models show a more complex deformation patterns in comparison to the standard model. Deformation is more localized within the source layer, leaving a broader less deformed zone within the middle of the source layer. In comparison to the standard model, ellipticity (R) of the strain ellipse is amplified by a factor of up to three in high deformation regions with a finite deformation f larger than two (f = log10(R)). Initially vertical and horizontal passive marker-lines within the salt layer, are folded during salt movement. Initially horizontally-oriented marker-lines in the source layer show upright folds within the middle of the stem. Within the source layer, initially vertical marker-lines form recumbent folds, which are refolded during their flow from the source layer into the stem. During their refolding, the hinge of the fold migrates outward towards the flank of the diapir. A temporal and spatial hinge migration is observed for sub-horizontal folds that originated in the source layer as they are refolded. We have also studied both the effect of curved versus sharp corners between the source layer and the stem on strain evolution within both the feeding source layer and the down-built diapir. Strain evolution and hinge migration are strongly influenced by the geometry of the corner between the source layer and the stem.

  • 224.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    Numerical modeling on progressive internal deformation indown-built diapirs2014In: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 632, p. 111-122Article in journal (Refereed)
    Abstract [en]

    A two-dimensional finite difference code (FDCON) is used to estimate the finite deformationwithin a down-builtdiapir. The geometry of the down-built diapir is fixed by using two rigid rectangular overburden unitswhich sinkinto a source layer of a constant viscosity. Thus, the model refers to diapirs consisting of a source layerfeeding a vertical stem, and not to other salt structures (e.g. salt sheets or pillows). With this setup westudy the progressive strain in three different deformation regimes within the “salt” material: (I) a squeezedchannel-flow deformation regime and (II) a corner-flow deformation regime within the source layer, and(III) a pure channel-flow deformation regime within the stem. We analyze the evolution of finite deformationin each regime individually, progressive strain for particles passing all three regimes, and total 2Dfinite deformationwithin the salt layer. Model results show that the material which enters the stem bears inherited strainaccumulated from the other two domains. Therefore, finite deformation in the stem differs from the expectedchannel-flow deformation, due to the deformation accumulated within the source layer. The stem displays ahigh deformation zone within its center and areas of decreasing progressive strain between its center and itsboundaries.High deformation zoneswithin the stemcould also be observedwithin natural diapirs (e.g. Klodowa,Polen). The location and structure of the high deformation zone (e.g. symmetric or asymmetric) could revealinformation about different rates of salt supplies from the source layer. Thus, deformation pattern could directlybe correlated to the evolution of the diapir.

  • 225.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    A new numerical method to calculate inhomogeneous and time dependent large deformations of two-dimensional geodynamic flows with application to diapirism2013In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 194, no 2, p. 623-639Article in journal (Refereed)
    Abstract [en]

    A key to understand many geodynamic processes is studying the associated large deformation fields. Finite deformation can be measured in the field by using geological strain markers giving the logarithmic strain f = log 10(R), where R is the ellipticity of the strain ellipse. It has been challenging to accurately quantify finite deformation of geodynamic models for inhomogeneous and time-dependent large deformation cases. We present a new formulation invoking a 2-D marker-in-cell approach. Mathematically, one can describe finite deformation by a coordinate transformation to a Lagrangian reference frame. For a known velocity field the deformation gradient tensor, F, can be calculated by integrating the differential equation DtFij = LikFkj, where L is the velocity gradient tensor and Dt the Lagrangian derivative. The tensor F contains all information about the minor and major semi-half axes and orientation of the strain ellipse and the rotation. To integrate the equation centrally in time and space along a particle's path, we use the numerical 2-D finite difference code FDCON in combination with a marker-in-cell approach. For a sufficiently high marker density we can accurately calculate F for any 2-D inhomogeneous and time-dependent creeping flow at any point for a deformation f up to 4. Comparison between the analytical and numerical solution for the finite deformation within a Poiseuille–Couette flow shows an error of less than 2 per cent for a deformation up to f = 1.7. Moreover, we determine the finite deformation and strain partitioning within Rayleigh–Taylor instabilities (RTIs) of different viscosity and layer thickness ratios. These models provide a finite strain complement to the RTI benchmark of van Keken et al. Large finite deformation of up to f = 4 accumulates in RTIs within the stem and near the compositional boundaries. Distinction between different stages of diapirism shows a strong correlation between a maximum occurring deformation of f = 1, 3 and 4, and the early, intermediate and late stages of diapirism, respectively. Furthermore, we find that the overall strain of a RTI is concentrated in the less viscous regions. Thus, spatial distributions and magnitudes of finite deformation may be used to identify stages and viscosity ratios of natural cases.

  • 226. Fuchs, Lukas
    et al.
    Schmeling, Harro
    Numerical models of diapiric structures: analysis of the finite straindistribution2012In: Geophysical Research Abstracts, ISSN 1029-7006, E-ISSN 1607-7962, Vol. 14, p. EGU2012-330-1-Article in journal (Refereed)
  • 227.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Numerical models of diapiric structures: comparison of the 2D finitedeformation field between Rayleigh-Taylor like and down-built likediapirs2013Conference paper (Refereed)
  • 228.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Numerical models on thermal and rheological sensitivity of deformation pattern at the lithosphere-asthenosphere boundary2013Conference paper (Refereed)
  • 229.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Thermo-mechanical modelling of progressive deformation and seismic anisotropy at the lithosphere-asthenosphere boundaryIn: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246XArticle in journal (Other academic)
    Abstract [en]

       Deformation at the lithosphere-asthenosphere boundary is strongly governed by its effective viscosity, which depends on temperature, strain rate, and grain size. Moreover, deformation can cause lattice preferred orientation resulting in seismic anisotropy and shear wave splitting. We used a 1D model approach to calculate shear strain and characteristic depths for an oceanic plate as a function of age. We assume a composite rheology (dislocation and diffusion creep) in combination with a half-space cooling model temperature field for constant and variable thermal parameters, and different potential mantle temperatures. Systematically, sensitivity of characteristic depths, deformation pattern, and seismic delay times δt on temperature, plate velocity, steady state grain size, and rheology have been analyzed. Model results show that the characteristic depths are only affected by local variations in the temperature field or a shift in the dominant deformation mechanism. The other parameters, however, do strongly affect the maximum total shear strain. Due to a continuous simple shear of the upper mantle governed by the motion of the plate, anisotropy, thickness of the anisotropic layer, and δt reach relatively large values in comparison to observed data. However, a small amount of dislocation creep (25-40 %), due to a modified rheology or small grain sizes, leads to a significantly thinner anisotropic layer. As a result, δt is reduced by 50 % or more. The change of the characteristics of the anisotropic layer and degree of its anisotropy may reflect and be of significance for the viscous (de)coupling between the lithosphere and asthenosphere.

  • 230.
    Fuchs, Lukas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Schmeling, Harro
    Goethe-University, Institute of Geoscience, Frankfurt am Main, Germany.
    Koyi, Hemin
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics.
    Thermo-mechanical modelling of progressive deformation at the lithosphere-asthenosphere boundary: The effect of a horizontal pressure gradientManuscript (preprint) (Other academic)
  • 231. Gallagher, K
    et al.
    Bodin, T
    Sambridge, M
    Weiss, D
    Kylander, Malin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Large, David
    Inference of abrupt changes in noisy geochemical records using transdimensional changepoint models2011In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 311, no 1-2, p. 182-194Article in journal (Refereed)
    Abstract [en]

    We present a method to quantify abrupt changes (or changepoints) in data series, represented as a function of depth or time. These changes are often the result of climatic or environmental variations and can be manifested in multiple datasets as different responses, but all datasets can have the same changepoint locations/timings. The method we present uses transdimensional Markov chain Monte Carlo to infer probability distributions on the number and locations (in depth or time) of changepoints, the mean values between changepoints and, if required, the noise variance associated with each dataset being considered. This latter point is important as we generally will have limited information on the noise, such as estimates only of measurement uncertainty, and in most cases it is not practical to make repeat sampling/measurement to assess other contributions to the variation in the data. We describe the main features of the approach (and describe the mathematical formulation in supplementary material), and demonstrate its validity using synthetic datasets, with known changepoint structure (number and locations of changepoints) and distribution of noise variance for each dataset. We show that when using multiple data, we expect to achieve better resolution of the changepoint structure than when we use each dataset individually. This is conditional on the validity of the assumption of common changepoints between different datasets. We then apply the method to two sets of real geochemical data, both from peat cores, taken from NE Australia and eastern Tibet. Under the assumption that changes occur at the same time for all datasets, we recover solutions consistent with those previously inferred qualitatively from independent data and interpretations. However, our approach provides a quantitative estimate of the relative probability of the inferred changepoints, allowing an objective assessment of the significance of each change.

  • 232.
    Gallego-Sala, Angela V.
    et al.
    Geography Department, University of Exeter, Exeter, UK.
    Charman, Dan J.
    Geography Department, University of Exeter, Exeter, UK.
    Brewer, Simon
    Page, Susan E.
    Prentice, I. Colin
    Friedlingstein, Pierre
    Moreton, Steve
    Amesbury, Matthew J.
    Beilman, David W.
    Björck, Svante
    Blyakharchuk, Tatiana
    Bochicchio, Christopher
    Booth, Robert K.
    Bunbury, Joan
    Camill, Philip
    Carless, Donna
    Chimner, Rodney A.
    Clifford, Michael
    Cressey, Elizabeth
    Courtney Mustaphi, Colin
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History, Archaeology. Environment Department, University of York, York, UK.
    De Vleeschouwer, François
    de Jong, Rixt
    Fialkiewicz-Koziel, Barbara
    Finkelstein, Sarah A.
    Garneau, Michelle
    Githumbi, Esther
    Hribjlan, John
    Holmquist, James
    Hughes, Paul D. M.
    Jones, Chris
    Jones, Miriam C.
    Karofeld, Edgar
    Klein, Eric S.
    Kokfelt, Ulla
    Korhola, Atte
    Lacourse, Terri
    Le Roux, Gael
    Lamentowicz, Mariusz
    Large, David
    Lavoie, Martin
    Loisel, Julie
    Mackay, Helen
    MacDonald, Glen M.
    Makila, Markku
    Magnan, Gabriel
    Marchant, Robert
    Marcisz, Katarzyna
    Martínez Cortizas, Antonio
    Massa, Charly
    Mathijssen, Paul
    Mauquoy, Dmitri
    Mighall, Timothy
    Mitchell, Fraser J. G.
    Moss, Patrick
    Nichols, Jonathan
    Oksanen, Pirita O.
    Orme, Lisa
    Packalen, Maara S.
    Robinson, Stephen
    Roland, Thomas P.
    Sanderson, Nicole K.
    Sannel, A. Britta K.
    Silva-Sánchez, Noemí
    Steinberg, Natascha
    Swindles, Graeme T.
    Turner, T. Edward
    Uglow, Joanna
    Väliranta, Minna
    van Bellen, Simon
    van der Linden, Marjolein
    van Geel, Bas
    Wang, Guoping
    Yu, Zicheng
    Zaragoza-Castells, Joana
    Zhao, Yan
    Institute of Geographical Science and Natural Resources, Chinese Academy of Science, Beijing, China.
    Latitudinal limits to the predicted increase of the peatland carbon sink with warming2018In: Nature Climate Change, ISSN 1758-678X, E-ISSN 1758-6798, Vol. 8, no 10, p. 907-913Article in journal (Refereed)
    Abstract [en]

    The carbon sink potential of peatlands depends on the balance of carbon uptake by plants and microbial decomposition. The rates of both these processes will increase with warming but it remains unclear which will dominate the global peatland response. Here we examine the global relationship between peatland carbon accumulation rates during the last millennium and planetary-scale climate space. A positive relationship is found between carbon accumulation and cumulative photosynthetically active radiation during the growing season for mid- to high-latitude peatlands in both hemispheres. However, this relationship reverses at lower latitudes, suggesting that carbon accumulation is lower under the warmest climate regimes. Projections under Representative Concentration Pathway (RCP)2.6 and RCP8.5 scenarios indicate that the present-day global sink will increase slightly until around ad 2100 but decline thereafter. Peatlands will remain a carbon sink in the future, but their response to warming switches from a negative to a positive climate feedback (decreased carbon sink with warming) at the end of the twenty-first century.

  • 233.
    Garcia-Urquia, Elias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics. Natl Autonomous Univ Honduras, Sch Civil Engn, Ciudad Univ, Tegucigalpa, Honduras..
    Establishing rainfall frequency contour lines as thresholds for rainfall-induced landslides in Tegucigalpa, Honduras, 1980-20052016In: Natural Hazards, ISSN 0921-030X, E-ISSN 1573-0840, Vol. 82, no 3, p. 2107-2132Article in journal (Refereed)
    Abstract [en]

    In this paper, a method to derive rainfall thresholds based on the relationship between daily and the antecedent rainfall up to 6 days prior to landslide occurrence is proposed for the analysis of 134 landslide days in Tegucigalpa, Honduras, during the years 1980-2005. Based on a simple graphical procedure, rainfall frequency contour lines have been drawn in the daily versus antecedent rainfall plots to connect rainfall combinations relatively having the same frequency of occurrence. A two-bound threshold has been established: Below the lower bound, rainfall events are so frequent that any landslide day may only occur due to a significant anthropogenic disturbance, while, above the upper bound, rainfall alone is capable of inducing landslide days. Contour lines originating at the same daily rainfall value in all plots were then grouped together to form a threshold set, for which the number of well-predicted landslide days and false alarms was determined. It has been determined that 16 and 84 landslide days have fallen below the lower bound and above the upper bound, respectively. In addition, this method has been proven effective in the distinction between days with and without landslides, since it has led to a 23 % reduction in the number of false alarms per well-predicted landslide day when compared to a previously established threshold line for Tegucigalpa.

  • 234. Gardiner, N J
    et al.
    Maidment, D W
    Kirkland, C L
    Bodorkos, S
    Smithies, R H
    Jeon, Heejin
    Isotopic insight into the Proterozoic crustal evolution of the Rudall Province, Western Australia2018In: Precambrian Research, Vol. 313, p. 31-50Article in journal (Refereed)
  • 235. Gardiner, Nicholas J
    et al.
    Wacey, David
    Kirkland, Christopher L
    Johnson, Tim
    Jeon, Heejin
    Zircon U–Pb, Lu–Hf and O isotopes from the 3414 Ma Strelley Pool Formation, East Pilbara Terrane, and the Palaeoarchaean emergence of a cryptic cratonic core2018In: Precambrian ResearchArticle in journal (Refereed)
  • 236.
    Gartz, Mira
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Plantdiversitet på svenska slåtterängar: En GIS-analys med kulturella perspektiv2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    High plant species diversity depends on a landscape that provides enough habitual space,functional connectivity and heterogeneity. Habitat destruction and land use change is recognizedas the biggest threat to biodiversity of today. The Swedish landscape has not only undergonedramatic changes in land-use the last 60 years, it also contains some of the last fragments inEurope of the highly valuable hay-meadows. Many of the Swedish hay-meadows are consideredto hold high ecological values and are protected by Natura 2000 regulations. Yet there are nosystematic conservation strategies for the hay-meadows and most of the work is done byvolunteers. This study aims to further investigate how the surrounding landscape affects thetotal plant species richness on Swedish hay-meadows. A local scale GIS-analysis on landscapessurrounding 21 hay-meadows across two time steps was carried out. The historical land-use wascompared with the present landscapes and with species data from the same areas. Results showthat the forest cover has grown almost 12% in 60 years. There is a negative correlation betweenforest and the plant species richness of both time steps. The total area of arable fields hasdropped 19%, although no statistical correlation with the plant species richness of either timestep was found. The ex-arable fields of 1950 however, did show a negative impact, both aloneand together with open pasture. Open pasture has decreased 17%, although no statisticalcorrelation was found between this land-cover category and plant species richness. The overallresults indicate that the historical land-use on the local scale is of greater importance on thecurrent plant species richness than present land-use. This should be considered within landscapeplanning and when designing conservation strategies.

  • 237.
    Gartz, Mira
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Plantdiversitet på svenska slåtterängar: En GIS-analys med kulturella perspektiv2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    High plant species diversity depends on a landscape that provides enough habitual space, functional connectivity and heterogeneity. Habitat destruction and land use change is recognized as the biggest threat to biodiversity of today. The Swedish landscape has not only undergone dramatic changes in land-use the last 60 years, it also contains some of the last fragments in Europe of the highly valuable hay-meadows. Many of the Swedish hay-meadows are considered to hold high ecological values and are protected by Natura 2000 regulations. Yet there are no systematic conservation strategies for the hay-meadows and most of the work is done by volunteers. This study aims to further investigate how the surrounding landscape affects the total plant species richness on Swedish hay-meadows. A local scale GIS-analysis on landscapes surrounding 21 hay-meadows across two time steps was carried out. The historical land-use was compared with the present landscapes and with species data from the same areas. Results show that the forest cover has grown almost 12% in 60 years. There is a negative correlation between forest and the plant species richness of both time steps. The total area of arable fields has dropped 19%, although no statistical correlation with the plant species richness of either time step was found. The ex-arable fields of 1950 however, did show a negative impact, both alone and together with open pasture. Open pasture has decreased 17%, although no statistical correlation was found between this land-cover category and plant species richness. The overall results indicate that the historical land-use on the local scale is of greater importance on the current plant species richness than present land-use. This should be considered within landscape planning and when designing conservation strategies.

  • 238.
    Gee, David G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Andreasson, Per-Gunnar
    Lund Univ, Dept Geol, Lund, Sweden..
    Lorenz, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Frei, Dirk
    Univ Stellenbosch, Matieland, South Africa..
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Mineralogy Petrology and Tectonics. AGH Univ Sci & Technol, Fac Geol Geophys & Environm Protect, PL-30059 Krakow, Poland..
    Comments to "Detrital zircon signatures of the Baltoscandian margin along the Arctic Circle Caledonides in Sweden: The Sveconorwegian connection" by Gee et al. (2015) Reply to Ake Johansson (Precambrian Research)2016In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. 276, p. 236-237Article in journal (Refereed)
  • 239.
    Gee, David G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Ladenberger, Anna
    Dahlqvist, Peter
    Majka, Jaroslaw
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Be'eri-Shlevin, Yaron
    Frei, Dirk
    Thomsen, Tonny
    The Baltoscandian margin detrital zircon signatures of the central Scandes2014In: Geological Society, London, Special Publications, Vol. 390, p. 131-155Article in journal (Refereed)
    Abstract [en]

    In central parts of the Scandinavian Caledonides, detrital zircon signatures provide evidence of the change in character of the Baltoscandian crystalline basement, from the characteristic Late Palaeoproterozoic granites of the Transscandinavian Igneous Belt (TIB, c. 1650–1850 Ma) in the foreland Autochthon to the typical, mainly Mesoproterozoic-age profile (c. 950–1700 Ma) of the Sveconorwegian Orogen of southwestern Scandinavia in the hinterland. Late Ediacaran to Early Cambrian shallow-marine Vemdal quartzites of the Jämtlandian Nappes (Lower Allochthon) provide strong bimodal signatures with TIB (1700–1800 Ma) and Sveconorwegian, sensu stricto (900–1150 Ma) ages dominant. Mid-Ordovician turbidites (Norråker Formation) of the Lower Allochthon in Sweden, sourced from the west, have unimodal signatures dominated by Sveconorwegian ages with peaks at 1000–1100 Ma, but with subordinate components of older Mesoproterozoic zircons (1200–1650 Ma). Latest Ordovician shallow-marine quartzites also yield bimodal signatures, but are more dispersed than in the Vemdal quartzites. In the greenschist facies lower parts of the Middle Allochthon, the Fuda (Offerdal Nappe) and Särv Nappe signatures are either unimodal or bimodal (950–1100 and/or 1700–1850 Ma), with variable dominance of the younger or older group, and subordinate other Mesoproterozoic components. In the overlying, amphibolite to eclogite facies lower part of the Seve Nappe Complex, where the metasediments are dominated by feldspathic quartzites, calcsilicate-rich psammites and marbles, most units have bimodal signatures similar to the Särv Nappes, but more dispersed; one has a unimodal signature very similar to the Ordovician turbidites of the Jämtlandian Nappes. In the overlying Upper Allochthon, Lower Köli (Baltica-proximal, Virisen Terrane), Late Ordovician quartzites provide unimodal signatures dominated by Sveconorwegian ages (sensu stricto). Further north in the Scandes, previously published zircon signatures in quartzites of the Lower Allochthon are similar to the Vemdal quartzites in Jämtland. Data from the Kalak Nappes at 70°N are in no way exotic to the Sveconorwegian Baltoscandian margin. They do show a Timanian influence (ages of c. 560–610 Ma), as would be expected from the palinspastic reconstructions of the nappes. Thus the detrital zircon signatures reported here and published elsewhere provide supporting evidence for a continuation northwards of the Sveconorwegian Orogen in the Neoproterozoic, from type areas in the south, along the Baltoscandian margin of Baltica into the high Arctic.

  • 240. Gennari, Giordana
    et al.
    Rosenberg, Thomas
    Spezzaferi, Silvia
    Berger, Jean-Pierre
    Fleitmann, Dominik
    Preusser, Frank
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Al-shanti, Mahmoud
    Matter, Albert
    Faunal evidence of a Holocene pluvial phase in Southern Arabia with remarks on the morphological variability of Helenina anderseni2011In: Journal of Foraminiferal Research, ISSN 0096-1191, E-ISSN 1943-264X, Vol. 41, p. 248-259Article in journal (Refereed)
    Abstract [en]

    Although foraminifera have been found living in inlandsaline lakes isolated from the sea, this phenomenon has rarelybeen recognized in the fossil record. This study documents theoccurrence of benthic foraminifera in Holocene lake sedimentslocated nearly 500 km inland from the Red Sea, in theAl-Mundafan region of southern Saudi Arabia. The lakeformed during a regional pluvial period, 10,500–6000 yr BP.The presence of foraminifera and brackish charophytes in thestudied section represent an interval when the lake wasslightly brackish due to high evaporation. The studiedsediments yielded a bispecific benthic foraminiferal faunacomprised of Helenina anderseni and Trichohyalus aguayoi,as well as the brackish charophyte genus Lamprothamnium.The benthic foraminifera are species characteristic ofmangrove swamps, salt marshes, and lagoons, which areenvironments currently widespread along the Red Sea coasts.Because the Al Mundafan area was never connected to the seaduring the Quaternary, wading birds must have been thevector that transported the foraminifera to the paleolake

  • 241.
    Geyer, Gerd
    et al.
    Bayer Julius Maximilians Univ Wurzburg, Lehrstuhl Geodynam & Geomat Forsch, Inst Geog & Geol, D-97074 Wurzburg, Germany..
    Peel, John S.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Middle Cambrian trilobites from the Ekspedition Brae Formation of North Greenland, with a reappraisal of the genus Elrathina2017In: Journal of Paleontology, ISSN 0022-3360, E-ISSN 1937-2337, Vol. 91, no 2, p. 265-293Article in journal (Refereed)
    Abstract [en]

    The richly fossiliferous Ekspedition Brae Formation of North Greenland yields a typical oligospecific fossil assemblage with well-preserved trilobites, helcionelloids, and lingulate brachiopods. The trilobites include Itagnostus subhastatus new species, Itagnostus sp. cf. I. gaspensis (Rasetti, 1948), Elrathina aphrodite new species, Elrathina athena new species, Elrathina hera new species, and Elrathia groenlandica new species-a fossil assemblage typical of the Bathyuriscus-Elrathina Zone as known from the Cordilleran regions of Laurentia. Excellent preservation allows a detailed assessment of the prosopon and elucidates aspects of the ontogenetic development of Elrathina and Elrathia. An evaluation of Elrathina includes a redescription of its type species, E. cordillerae (Rominger, 1887), based on the type material, and indicates that most specimens collected from the Burgess Shale and previously dealt with as E. cordillerae represent a new species.

  • 242.
    Geyer, Gerd
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Peel, John Stuart
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Streng, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
    Voigt, Sebastian
    Fischer, Jan
    Preusse, Marvin
    A remarkable Amgan (Middle Cambrian, Stage 5) fauna from the Sauk Tanga, Madygen region, Kyrgyzstan2014In: Bulletin of Geosciences, ISSN 1214-1119, E-ISSN 1802-8225, Vol. 89, no 2, p. 375-400Article in journal (Refereed)
    Abstract [en]

    Early Middle Cambrian bituminous coquinoid limestones from a tectonically isolated outcrop in southwestern Kyrgyzstan yield a remarkably diverse fauna, with stem-group cnidarians, trilobites, rhynchonelliformean brachiopods, and other shelly fossils. The fossil site is in the northern foothills of the Turkestan Range and thus forms part of the westernmost extension of the South Tien Shan. The fauna includes two fairly well known trilobite species, Glabrella ventrosa Lermontova, 1940 and Dorypyge richthofeniformis Lermontova, 1940, that provide confident support for an Amgan age of the rocks. New described taxa include the stem-group cnidarian Cambroctoconus kyrgyzstanicus Peel sp. nov., the trilobite Olenoides sagittatus Geyer sp. nov., and the helcionelloid Manasoconus bifrons Peel gen. et sp. nov. Additional fossils within the samples include the trilobites Olenoides sp. A, Kootenia sp., and Pseudoeteraspis? sp.; the rhynchonelliform brachiopods Narynella cf. ferganensis (Andreeva, 1962), Narynella? sp., Austrohedra? sp. nov., and two species of uncertain generic affinity; the tommotiid Tesella sp.; the hyolithelminth Hyolithellus sp.; and the palaeoscolecid Hadimopanella oezgueli Gedik, 1977. Of particular interest is Cambroctoconus kyrgyzstanicus with an octagonal corallum and a sparsely septate calyx.

  • 243. Ghasemi, A
    et al.
    Talbot, Christopher J.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    A new tectonic scenario fro the Sanandaj-Sirjan Zone (Iran)2006In: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 26, no 6, p. 683-693Article in journal (Refereed)
    Abstract [en]

    Recent geochemical studies of volcanic rocks forming part of the ophiolites within the Zagros and Naien-Baft orogen indicate that most of them were developed as supra-subduction ophiolites in intra-oceanic island arc environments. Intra-oceanic island arcs and ophiolites now forming the Naien-Baft zone were emplaced southwestward onto the northeastern margin of the South Sanandaj-Sirjan Zone, while those now in the High Zagros were emplaced southwestward onto the northern margin of Arabia. Thereafter, subduction continued on opposite sides of the remnant oceans. The floor of Neo-Tethys Ocean was subducted at a low angle beneath the entire Sanandaj-Sirjan Zone, and the floor of the Naien-Baft Ocean was subducted beneath the Central Iranian Micro-continent. The Naien-Baft Ocean extended into North-West Iran only temporarily. This failed ocean arm (between the Urumieh-Dokhtar Magmatic Assemblage and the main Zagros Thrust) was filled by thick Upper Triassic-Upper Jurassic sediments. The Naien-Baft Ocean finally closed in the Paleocene and Neo-Tethys closed in the Early to Middle Eocene. After Arabia was sutured to Iran. the Urumieh-Dokhtar Magmatic Assemblage recorded slab break-off in the Middle Eocene.

  • 244.
    Ghosh, Devanita
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Distribution and Biogeochemical Cycling of Arsenic In Grey and Brown Sand Aquifers in the Bengal Delta Plains (India)2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    An elevated level of Arsenic (As) in aquifers from India and Bangladesh affecting the human health has been widely reported since the late 1980s. The thesis aim is to investigate the present status of As contamination and biogeochemical cycling with direct role of diverse indigenous bacterial communities in As cycling in the Bengal Delta Plain (BDP) aquifers in Nadia district, West Bengal (India). The As(III) oxidizing bacterial communities were predominant in grey sand aquifers (GSA), but were characteristically absent in brown sand aquifers (BSA). Rainwater recharge containing inorganic and organic dissolved compounds played an important role in shaping the different groups of bacterial phenotypes. It included thearsenite-oxidizing bacteria as revealed by the aioA and 16S rRNA phylogeny. These bacterial communities in BDP groundwater were assumed to utilize the dissolved and sedimentary organic carbon (DOC and SOC) as the primary carbon source for respiration, and remobilization/immobilization of As involving reductive dissolution of iron oxyhydroxides. Hence, sediment and groundwater of these aquifer waters were characterized for their different inorganic constituents (metals) and organic compound classes. There were notable differences between the groundwater DOC and SOC pools. The only similarity between these carbon pools is presence of petroleum-derived hydrocarbons. The SOC in BSA has good correlation with the clay and silt-rich fraction. Notably, As formed complexes with iron, but not manganese. Biomarker characterization in sediments showed presence of terrigenous inputs along with petroleum-derived hydrocarbons. However, these hydrocarbons were absent in BSA sediments, and so were the arsenite oxidizing bacterial communities. Although DOC in groundwater plays an important role in sustaining the microorganisms, the contrasting character of SOC in BSA and GSA strongly influence the shaping of microbial community structure and biogeochemical cycling of As. This particularly affects the natural ‘safe’ drinking water capacity. Overall, the study gives a new directionfor long-term research on As biogeochemical cycling in the contaminated BDP aquifers.

  • 245. Giesler, Reiner
    et al.
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Karlsson, Jan
    Lundin, Erik J.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Humborg, Christoph
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Spatiotemporal variations of pCO(2) and delta C-13-DIC in subarctic streams in northern Sweden2013In: Global Biogeochemical Cycles, ISSN 0886-6236, E-ISSN 1944-9224, Vol. 27, no 1, p. 176-186Article in journal (Refereed)
    Abstract [en]

    Current predictions of climate-related changes in high-latitude environments suggest major effects on the C export in streams and rivers. To what extent this will also affect the stream water CO2 concentrations is poorly understood. In this study we examined the spatiotemporal variation in partial pressure of CO2 (pCO(2)) and in stable isotopic composition of dissolved inorganic carbon (delta C-13-DIC) in subarctic streams in northern Sweden. The selected watersheds are characterized by large variations in high-latitude boreal forest and tundra and differences in bedrock. We found that all streams generally were supersaturated in pCO(2) with an average concentration of 850 mu atm. The variability in pCO(2) across streams was poorly related to vegetation cover, and carbonaceous bedrock influence was manifested in high DIC concentrations but not reflected in either stream pCO(2) or delta C-13-DIC. Stream water pCO(2) values were highest during winter base flow when we also observed the lowest delta C-13-DIC values, and this pattern is interpreted as a high contribution from CO2 from soil respiration. Summer base flow delta C-13-DIC values probably are more affected by in situ stream processes such as aquatic production/respiration and degassing. A challenge for further studies will be to disentangle the origin of stream water CO2 and quantify their relative importance.

  • 246. Gilg, H. Albert
    et al.
    Hall, Adrian M.
    University of St Andrews, Scotland, UK.
    Ebert, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Cool kaolins in Finland2013In: Palaeogeography, Palaeoclimatology, Palaeoecology, ISSN 0031-0182, E-ISSN 1872-616X, Vol. 392, p. 454-462Article in journal (Refereed)
    Abstract [en]

    We use D/H and 18O/16O ratios to explore the age of kaolins on the Fennoscandian Shield. Sub-Cretaceous kaolins in southern Scandinavia have isotopic compositions indicative of weathering under warm mean annual temperatures (MATs) of > 15 °C. Deep kaolins on the shield surface in Finland previously also have been regarded as products of humid tropical weathering of Mesoproterozoic to Eocene age. New oxygen and hydrogen isotope ratios indicate, however, weathering by cool groundwater under MATs of 13–15 °C. Isotope ratios are also not consistent with deep (> 1 km) burial by cover rocks, indicating that a very old age for the weathering is unlikely. Palaeotemperatures are below Cretaceous MATs, yet substantially above Plio-Pleistocene MATs. Comparisons with palaeotemperatures in N Europe and around the Arctic Ocean indicate that the Finnish kaolins developed on the shield surface in the Palaeogene or, alternatively, Miocene. Deep weathering was selectively developed in highly fractured shield rocks and took place in response to latest Cretaceous and Palaeogene uplift and after stripping of Palaeozoic cover rocks. The cool kaolins in Finland indicate that previous routine attributions of kaolinitic weathering products in the geological record to humid tropical environments should be closely scrutinised.

  • 247. Giosan, Liviu
    et al.
    Clift, Peter D.
    Macklin, Mark G.
    Fuller, Dorian Q.
    Constantinescu, Stefan
    Durcan, Julie A.
    Stevens, Thomas
    Department of Geography, Royal Holloway, University of London, United Kingdom.
    Duller, Geoff A. T.
    Tabrez, Ali R.
    Gangal, Kavita
    Adhikari, Ronojoy
    Alizai, Anwar
    Filip, Florin
    VanLaningham, Sam
    Syvitski, James P. M.
    Fluvial landscapes of the Harappan civilization2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 26, p. E1688-E1694Article in journal (Refereed)
  • 248.
    Giosan, Liviu
    et al.
    Woods Hole Oceanog, Geol & Geophys, Woods Hole, MA 02543 USA.
    Naing, Thet
    Tun, Myo Min
    Clift, Peter D.
    Louisiana State Univ, Geol & Geophys, Baton Rouge, LA 70803 USA.
    Filip, Florin
    Inst Fluvial & Marine Syst, Bucharest, Romania.
    Constantinescu, Stefan
    Bucharest Univ, Geog Dept, Bucharest, Romania.
    Khonde, Nitesh
    Woods Hole Oceanog, Geol & Geophys, Woods Hole, MA 02543 USA;Birbal Sahni Inst Palaeosci, Lucknow, Uttar Pradesh, India.
    Blusztajn, Jerzy
    Woods Hole Oceanog, Geol & Geophys, Woods Hole, MA 02543 USA.
    Buylaert, Jan-Pieter
    Tech Univ Denmark, Ctr Nucl Technol, DTU Nutech, Roskilde, India.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Thwin, Swe
    Mawlamyine Univ, Dept Marine Sci, Mawlamyine, Myanmar.
    On the Holocene evolution of the Ayeyawady megadelta2018In: Earth Surface Dynamics, ISSN 2196-6311, Vol. 6, no 2, p. 451-466Article in journal (Refereed)
    Abstract [en]

    The Ayeyawady delta is the last Asian megadelta whose evolution has remained essentially unexplored so far. Unlike most other deltas across the world, the Ayeyawady has not yet been affected by dam construction, providing a unique view on largely natural deltaic processes benefiting from abundant sediment loads affected by tectonics and monsoon hydroclimate. To alleviate the information gap and provide a baseline for future work, here we provide a first model for the Holocene development of this megadelta based on drill core sediments collected in 2016 and 2017, dated with radiocarbon and optically stimulated luminescence, together with a reevaluation of published maps, charts and scientific literature. Altogether, these data indicate that Ayeyawady is a mud-dominated delta with tidal and wave influences. The sediment-rich Ayeyawady River built meander belt alluvial ridges with avulsive characters. A more advanced coast in the western half of the delta (i.e., the Pathein lobe) was probably favored by the more western location of the early course of the river. Radiogenic isotopic fingerprinting of the sediment suggests that the Pathein lobe coast does not receive significant sediment from neighboring rivers. However, the eastern region of the delta (i.e., Yangon lobe) is offset inland and extends east into the mudflats of the Sittaung estuary. Wave-built beach ridge construction during the late Holocene, similar to several other deltas across the Indian monsoon domain, suggests a common climatic control on monsoonal delta morphodynamics through variability in discharge, changes in wave climate or both. Correlation of the delta morphological and stratigraphic architecture information on land with the shelf bathymetry, as well as its tectonic, sedimentary and hydrodynamic characteristics, provides insight on the peculiar growth style of the Ayeyawady delta. The offset between the western Pathein lobe and the eastern deltaic coast appears to be driven by tectonic-hydrodynamic feedbacks as the extensionally lowered shelf block of the Gulf of Mottama amplifies tidal currents relative to the western part of the shelf. This situation probably activates a perennial shear front between the two regions that acts as a leaky energy fence. Just as importantly, the strong currents in the Gulf of Mottama act as an offshore-directed tidal pump that helps build the deep mid-shelf Mottama clinoform with mixed sediments from the Ayeyawady, Sittaung and Thanlwin rivers. The highly energetic tidal, wind and wave regime of the northern Andaman Sea thus exports most sediment offshore despite the large load of the Ayeyawady River.

  • 249.
    Githumbi, Esther N.
    et al.
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Kariuki, Rebecca
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Shoemaker, Anna
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History.
    Courtney Mustaphi, Colin
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History. Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Chuhila, Maxmillian
    Department of History, University of Dar es Salaam, Dar es Salaam, Tanzania.
    Richer, Suzi
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.; Department of Archaeology, University of York, York, United Kingdom.
    Lane, Paul
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Arts, Department of Archaeology and Ancient History. School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa.
    Marchant, Rob
    Environment Department, York Institute for Tropical Ecosystems, University of York, York, United Kingdom.
    Pollen, People and Place: Multidisciplinary Perspectives on Ecosystem Change at Amboseli, Kenya2018In: Frontiers in Earth Science, ISSN 1096-231X, E-ISSN 1664-8021, Vol. 5, p. 1-26, article id 113Article in journal (Refereed)
    Abstract [en]

    This study presents a multidisciplinary perspective for understanding environmental change and emerging socio-ecological interactions across the Amboseli region of southwestern Kenya. We focus on late Holocene (<5,000 cal yr. BP) changes and continuities reconstructed from sedimentary, archeological, historical records and socio-ecological models. We utilize multi-disciplinary approaches to understand environmental-ecosystem-social interactions over the longue durée and use this to simulate different land use scenarios supporting conservation and sustainable livelihoods using a socio-ecological model. Today the semi-arid Amboseli landscape supports a large livestock and wildlife population, sustained by a wide variety of plants and extensive rangelands regulated by seasonal rainfall and human activity. Our data provide insight into how large-scale and long-term interactions of climate, people, livestock, wildlife and external connections have shaped the ecosystems across the Amboseli landscape. Environmental conditions were dry between ~5,000 and 2,000 cal yr. BP, followed by two wet periods at ~2,100–1,500 and 1,400–800 cal yr. BP with short dry periods; the most recent centuries were characterized by variable climate with alternative dry and wet phases with high spatial heterogeneity. Most evident in paleo and historical records is the changing woody to grass cover ratio, driven by changes in climate and fire regimes entwined with fluctuating elephant, cattle and wild ungulate populations moderated by human activity, including elephant ivory trade intensification. Archeological perspectives on the occupation of different groups (hunter-gatherers, pastoralists, and farmers) in Amboseli region and the relationships between them are discussed. An overview of the known history of humans and elephants, expanding networks of trade, and the arrival and integration of metallurgy, livestock and domesticated crops in the wider region is provided. In recent decades, increased runoff and flooding have resulted in the expansion of wetlands and a reduction of woody vegetation, compounding problems created by increased enclosure and privatization of these landscapes. However, most of the wetlands outside of the protected area are drying up because of the intensified water extraction by the communities surrounding the National Park and on the adjacent mountains areas, who have increased in numbers, become sedentary and diversified land use around the wetlands.

  • 250. Glimskär, Anders
    et al.
    Skånes, Helle
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Land Type Categories as a Complement to Land Use and Land Cover Attributes in Landscape Mapping and Monitoring2015In: Land Use and Land Cover Semantics: Principles, Best Practices, and Prospects / [ed] Ola Ahlqvist, Dalia Varanka, Steffen Fritz, and Krzysztof Janowicz, Boca Raton: CRC Press, 2015, p. 171-190Chapter in book (Refereed)
    Abstract [en]

    The purpose of land cover and land use descriptions varies, and this influences how these concepts are perceived in different contexts. The increasing need for spatial data for multipurpose monitoring and modeling also increases the demands for compatibility, repeatability, detail, and well-documented criteria. We suggest that threshold values along a continuous scale can be used to create nominal classes for a common conceptual framework. However, the exact values of these thresholds need to be based on well-defined functional and systematic criteria. Ecological and environmental gradients are often mosaic and complex, and several types of land use may coexist at the same site. In reality, land use can be seen as a “shifting cloud” of activities varying in both time and space. We advocate the use of strict definitions of land cover as physical structures and land use as human activities, which raises the need for a complementary concept, which we call “land type,” with stable threshold values based on mutually exclusive functional criteria. Such functional criteria often put clear limits to what spatial resolution is appropriate, since the suitability for a certain purpose (e.g., agriculture or forestry) is determined by the user of the land, rather than by the independent observer. Our example of land type categories comprises a two-level hierarchical classification with seven main types and altogether 28 subtypes. As an example, we discuss the overlapping Swedish definitions of forest and arable land. The criteria that define our main land types are less dependent on how the area is managed at a specific moment in time, and they are therefore less sensitive to short-term variation. The land types define the limits for what land cover and land use can be expected at a certain site, given, for example, ground conditions, water, or artificial structures. Since such land types need to incorporate functional and qualitative understanding and interpretation, human visual interpretation is needed, whereas automated remote sensing methods are suitable mainly for the structural aspects of land cover.

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