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  • 201.
    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.

  • 202.
    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)
  • 203.
    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.

  • 204.
    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.

  • 205.
    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)
  • 206.
    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.

  • 207.
    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)
  • 208.
    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.

  • 209.
    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.

  • 210.
    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.

  • 211.
    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.

  • 212. 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)
  • 213.
    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)
  • 214.
    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)
  • 215.
    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.

  • 216.
    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)
  • 217. 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.

  • 218.
    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.

  • 219.
    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.

  • 220.
    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.

  • 221.
    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)
  • 222.
    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.

  • 223. 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

  • 224.
    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.

  • 225.
    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.

  • 226. 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.

  • 227.
    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.

  • 228. 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.

  • 229. 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.

  • 230. 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)
  • 231.
    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.

  • 232.
    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.

  • 233. 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.

  • 234.
    Goehring, Brent, M.
    et al.
    Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University.
    Lohne, Öystein S.
    Department of Earth Science, University of Bergen.
    Mangerud, Jan
    Department of Earth Science, University of Bergen.
    Svendsen, John Inge
    Department of Earth Science, University of Bergen.
    Gyllencreutz, Richard
    Univ Bergen, Dept Earth Sci, Bergen, Norway.
    Schaefer, Joerg
    Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory, Columbia University.
    Finkel, Robert
    Earth and Planetary Science Department, University of California-Berkeley.
    Late Glacial and Holocene 10Be production rates for western Norway2012In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 27, no 1, p. 89-96Article in journal (Refereed)
    Abstract [en]

    We present a new regional calibration of the 10Be production rate from two well-dated surfaces insouthern Norway: a rock avalanche with 14C-dated wood and a precisely dated Younger Dryas moraine. Calculated10Be production rates are 4.260.13 and 4.650.14 at g1 a1 for the Lal/Stone and Lifton scaling models,respectively. Our regional production rate for southern Norway is 5% lower than the canonical global 10Be productionrate with lower uncertainties. Our 10Be production rate agrees with regional 10Be production rates from north-easternNorth America and New Zealand. The 10Be production rate estimate presented here can be used to improve theprecision and accuracy of exposure-dated ice-marginal features, as well as other surfaces, in northern Europe.

  • 235. Goldner, A.
    et al.
    Huber, M.
    Caballero, Rodrigo
    Stockholm University, Faculty of Science, Department of Meteorology .
    Does Antarctic glaciation cool the world?2013In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 9, no 1, p. 173-189Article in journal (Refereed)
    Abstract [en]

    In this study, we compare the simulated climatic impact of adding an Antarctic ice sheet (AIS) to the greenhouse world of the Eocene and removing the AIS from the modern world. The modern global mean surface temperature anomaly (Delta T) induced by Antarctic Glaciation depends on the background CO2 levels and ranges from -1.22 to -0.18 K. The Eocene Delta T is nearly constant at similar to-0.25 K. We calculate an climate sensitivity parameter S[Antarctica] which we define as Delta T divided by the change in effective radiative forcing (Delta Q(Antarctica)) which includes some fast feedbacks imposed by prescribing the glacial properties of Antarctica. The main difference between the modern and Eocene responses is that a negative cloud feedback warms much of the Earth's surface as a large AIS is introduced in the Eocene, whereas this cloud feedback is weakly positive and acts in combination with positive sea-ice feedbacks to enhance cooling introduced by adding an ice sheet in the modern. Because of the importance of cloud feedbacks in determining the final temperature sensitivity of the AIS, our results are likely to be model dependent. Nevertheless, these model results suggest that the effective radiative forcing and feedbacks induced by the AIS did not significantly decrease global mean surface temperature across the Eocene-Oligocene transition (EOT -34.1 to 33.6 Ma) and that other factors like declining atmospheric CO2 are more important for cooling across the EOT. The results illustrate that the efficacy of AIS forcing in the Eocene is not necessarily close to one and is likely to be model and state dependent. This implies that using EOT paleoclimate proxy data by itself to estimate climate sensitivity for future climate prediction requires climate models and consequently these estimates will have large uncertainty, largely due to uncertainties in modelling low clouds.

  • 236. Goodrich, Katherine A.
    et al.
    Ergun, Robert E.
    Wilder, Frederick D.
    Burch, James
    Torbert, Roy
    Khotyaintsev, Yuri
    Lindqvist, Per-Arne
    KTH, School of Electrical Engineering (EES), Space and Plasma Physics.
    Russell, Christopher
    Strangeway, Robert
    Magnes, Werner
    Gershman, Daniel
    Giles, Barbara
    Nakamura, Rumi
    Stawarz, Julia
    Holmes, Justin
    Sturner, Andrew
    Malaspina, David M.
    MMS Multipoint electric field observations of small-scale magnetic holes2016In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 12, p. 5953-5959Article in journal (Refereed)
    Abstract [en]

    Small-scale magnetic holes (MHs), local depletions in magnetic field strength, have been observed multiple times in the Earth's magnetosphere in the bursty bulk flow (BBF) braking region. This particular subset of MHs has observed scale sizes perpendicular to the background magnetic field (B) less than the ambient ion Larmor radius (rho(i)). Previous observations by Time History of Events and Macroscale Interactions during Substorms (THEMIS) indicate that this subset of MHs can be supported by a current driven by the E x B drift of electrons. Ions do not participate in the E x B drift due to the small-scale size of the electric field. While in the BBF braking region, during its commissioning phase, the Magnetospheric Multiscale (MMS) spacecraft observed a small-scale MH. The electric field observations taken during this event suggest the presence of electron currents perpendicular to the magnetic field. These observations also suggest that these currents can evolve to smaller spatial scales.

  • 237.
    Grabs, T.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Bishop, K.
    Laudon, H.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Seibert, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Riparian zone hydrology and soil water total organic carbon (TOC): implications for spatial variability and upscaling of lateral riparian TOC exports2012In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 9, no 10, p. 3901-3916Article in journal (Refereed)
    Abstract [en]

    Groundwater flowing from hillslopes through riparian (near-stream) soils often undergoes chemical transformations that can substantially influence stream water chemistry. We used landscape analysis to predict total organic carbon (TOC) concentration profiles and groundwater levels measured in the riparian zone (RZ) of a 67 km(2) catchment in Sweden. TOC exported laterally from 13 riparian soil profiles was then estimated based on the riparian flow-concentration integration model (RIM). Much of the observed spatial variability of riparian TOC concentrations in this system could be predicted from groundwater levels and the topographic wetness index (TWI). Organic riparian peat soils in forested areas emerged as hotspots exporting large amounts of TOC. These TOC fluxes were subject to considerable temporal variations caused by a combination of variable flow conditions and changing soil water TOC concentrations. Mineral riparian gley soils, on the other hand, were related to rather small TOC export rates and were characterized by relatively time-invariant TOC concentration profiles. Organic and mineral soils in RZs constitute a heterogeneous landscape mosaic that potentially controls much of the spatial variability of stream water TOC. We developed an empirical regression model based on the TWI to move beyond the plot scale and to predict spatially variable riparian TOC concentration profiles for RZs underlain by glacial till.

  • 238. Graham, Alastair G. C.
    et al.
    Dutrieux, Pierre
    Vaughan, David G.
    Nitsche, Frank O.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Larter, Robert D.
    Jenkins, Adrian
    Seabed corrugations beneath an Antarctic ice shelf revealed by autonomous underwater vehicle survey: Origin and implications for the history of Pine Island Glacier2013In: Journal of Geophysical Research: Earth Surface, ISSN 2169-9011, Vol. 118, no 3, p. 1356-1366Article in journal (Refereed)
    Abstract [en]

    [1] Ice shelves are critical features in the debate about West Antarctic ice sheet change and sea level rise, both because they limit ice discharge and because they are sensitive to change in the surrounding ocean. The Pine Island Glacier ice shelf has been thinning rapidly since at least the early 1990s, which has caused its trunk to accelerate and retreat. Although the ice shelf front has remained stable for the past six decades, past periods of ice shelf collapse have been inferred from relict seabed “corrugations” (corrugated ridges), preserved 340 km from the glacier in Pine Island Trough. Here we present high-resolution bathymetry gathered by an autonomous underwater vehicle operating beneath an Antarctic ice shelf, which provides evidence of long-term change in Pine Island Glacier. Corrugations and ploughmarks on a sub-ice shelf ridge that was a former grounding line closely resemble those observed offshore, interpreted previously as the result of iceberg grounding. The same interpretation here would indicate a significantly reduced ice shelf extent within the last 11 kyr, implying Holocene glacier retreat beyond present limits, or a past tidewater glacier regime different from today. The alternative, that corrugations were not formed in open water, would question ice shelf collapse events interpreted from the geological record, revealing detail of another bed-shaping process occurring at glacier margins. We assess hypotheses for corrugation formation and suggest periodic grounding of ice shelf keels during glacier unpinning as a viable origin. This interpretation requires neither loss of the ice shelf nor glacier retreat and is consistent with a “stable” grounding-line configuration throughout the Holocene.

  • 239.
    Graham, Robert M.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    The role of Southern Ocean fronts in the global climate system2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The location of fronts has a direct influence on both the physical and biological processes in the Southern Ocean. However, until recently fronts have been poorly resolved by available data and climate models. In this thesis we utilise a combination of high resolution satellite data, model output and ARGO data to improve our basic understanding of fronts.

    A method is derived whereby fronts are identified as local maxima in sea surface height gradients. In this way fronts are defined locally as jets, rather than continuous-circumpolar water mass boundaries. A new climatology of Southern Ocean fronts is presented. This climatology reveals a new interpretation of the Subtropical Front. The currents associated with the Subtropical Front correspond to the western boundary current extensions from each basin, and we name these the Dynamical Subtropical Front. Previous studies have instead suggested that the Subtropical Front is a continuous feature across the Southern Ocean associated with the super gyre boundary.

    A comprehensive assessment of the relationship between front locations and wind stress is conducted. Firstly, the response of fronts to a southward shift in the westerly winds is tested using output from a 100 year climate change simulation on a high resolution coupled model. It is shown that there was no change in the location of fronts within the Antarctic Circumpolar Current as a result of a 1.3° southward shift in the westerly winds. Secondly, it is shown that the climatological position of the Subtropical Front is 5-10° north of the zero wind stress curl line, despite many studies assuming that the location of the Subtropical Front is determined by the zero wind stress curl.

    Finally, we show that the nutrient supply at ocean fronts is primarily due to horizontal advection and not upwelling. Nutrients from coastal regions are entrained into western boundary currents and advected into the Southern Ocean along the Dynamical Subtropical Front. 

  • 240.
    Graham, Robert M.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    De Boer, Agatha M.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kohfeld, Karen E.
    Schlosser, Christian
    Identifying sources and transport pathways of iron in the Southern OceanIn: Deep Sea Research Part I: Oceanographic Research Papers, ISSN 0967-0637, E-ISSN 1879-0119Article in journal (Refereed)
    Abstract [en]

    Over large regions of the global ocean primary productivity is limited by the availability of dissolved iron. Changes in the supply of iron to these regions could have major impacts on primary productivity and the carbon cycle. One of the largest sources of dissolved iron to the ocean is thought to be from shelf sediments, and this source is often parameterized in biogeochemical models as a depth dependent iron flux through the seafloor. Using the knowledge that Southern Ocean surface waters are iron limited, we infer source regions of iron to the Southern Ocean by identifying where the most intense chlorophyll blooms develop. We further derive surface current patterns from satellite sea surface height fields to assess the role of the ocean circulation in transporting iron away from these source regions. We find a tight relationship between satellite chlorophyll concentrations and sea surface height. Large chlorophyll blooms develop on the shelf and where the western boundary currents detach from the continental shelves and turn eastward into the Southern Ocean. This is likely due to shelf supplied iron becoming entrained into western boundary currents and advected into the Southern Ocean along the Dynamical Subtropical Front. The most intense chlorophyll blooms are located along coastal margins of islands and continents. Blooms do not develop over submerged seamounts or plateaus in the open ocean. This suggests that shelf sediments in coastal regions act as large bioavailable iron sources to the Southern Ocean. We recommend that a more accurate method of parameterizing the shelf sediment iron flux could be to prescribe this flux only through grid cells neighboring coastlines. Finally, we hypothesize how changes in sea level during glacial-interglacial cycles may have altered the distribution of shelf sediment iron sources in the Southern Ocean and helped to drive export production anomalies in the Sub-Antarctic Zone.

  • 241.
    Granit, Jakob
    Stockholm International Water Institute (SIWI).
    Identifying Business Models for Transboundary River Basin Institutions2010In: Transboundary Water Management: Principles and Practise / [ed] Anton Earle, Anders Jägerskog and Joakim Öjendal, London: Earthscan , 2010, p. 143-154Chapter in book (Refereed)
  • 242.
    Granit, Jakob
    Stockholm International Water Institute (SIWI).
    Reconsidering Integrated Water Resources Management: Promoting Economic Growth and Tackling Environmental Stress2011In: Coping with Global Environmental Change, Disasters and Security: Threats, Challenges, Vulnerabilities and Risks / [ed] Brauch, H.G., Spring, U. O., Mesjaz, C., Grin, J.,Kamere – Mbote, P., Chourou. B., Dunay, P. & Birkman, J., Berlin, Heidelberg: Springer, 2011, p. 947-955Chapter in book (Refereed)
    Abstract [en]

    Integrated Water Resources Management (IWRM) is today widely advocated by natural resources managers and the scientific community as the preferred approach to manage water. IWRM stresses the river basin as the single management unit and the integration of freshwater using sectors and stakeholders across society.

  • 243.
    Granit, Jakob J.
    et al.
    Stockholm International Water Institute (SIWI).
    King, R. Michael
    Noël, Raymond
    Strategic Environmental Assessment as a tool to Develop Power in Transboundary Water Basin Settings2011In: International Journal of Social Ecology and Sustainable Development, ISSN 1947-8402, Vol. 2, no 4, p. 1-11Article in journal (Refereed)
    Abstract [en]

    This paper proposes a generic consultative process for undertaking Strategic Environmental Assessments (SEA) in a transboundary river basin context to bring up front environmental and social issues of major development programs into the transboundary planning, project development and investment finance processes. The paper demonstrates through an analysis of two case studies from the Nile Basin in East and North Africa how an SEA approach with a focus on hydropower development is a transparent pre-investment tool that allows for consensus building in support of transboundary and regional strategic decision making and integration. Further, it demonstrates how an SEA can guide public and private sector investors seeking to develop the power sector in general and hydropower options in particular by allowing for a first level understanding of challenges and opportunities of power development and the development scenarios preferred by riparian governments.

  • 244.
    Greenwood, Sarah L.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gyllencreutz, Richard
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jakobsson, Martin
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Anderson, John B.
    Ice-flow switching and East/West Antarctic Ice Sheet roles in glaciation of the western Ross Sea2012In: Geological Society of America Bulletin, ISSN 0016-7606, E-ISSN 1943-2674, Vol. 124, no 11-12, p. 1736-1749Article in journal (Refereed)
    Abstract [en]

    The long-term behavior of the East and West Antarctic Ice Sheets, and their respective responses to forcing provide essential context for assessment of modern dynamic changes in ice-flow regimes and ice-sheet and shelf margins. The western Ross Sea discharges ice from both the East and West Antarctic Ice Sheets, and the paleoglacial record from this region is therefore valuable in unraveling their long-term behavior. New, high-resolution multibeam bathymetric data reveal snapshots of well-preserved glacial landforms on the seafloor around Ross Island and McMurdo Sound. Glacial lineations, grounding zone wedges, draped recessional moraines, and meltwater channels record a series of different ice-flow events in the region, contradictions between which require major phases of ice-flow reorganization. From the glacial geomorphology, we reconstruct a four-stage model of ice-flow evolution for the last glacial cycle, consisting of: (1) northeastward flow into the Ross Sea from McMurdo Sound; (2) westward flow from the Ross Sea, around Ross Island, and onto the Victoria Land coast and coastal seafloor trough; (3) a deglacial phase of ice-sheet thinning, minor shifts in flow, and grounding line retreat into McMurdo Sound; and (4) grounding line pinning on Ross Island during regional retreat, uncoupling of a remnant Ross Island ice cap, and local oscillation of Victoria Land outlet glaciers. We find that East Antarctic Ice Sheet ice discharge had a strong influence on ice-flow geometry in this part of the Ross Sea during the last glacial stage, but that it was not necessarily in phase with the behavior of the West Antarctic Ice Sheet. It is similarly evident that the ice streams that drained the Ross Sea over the continental shelf at the Last Glacial Maximum did not all operate synchronously, and exerted different drawdown power at different times. Finally, we conclude that Ross Island acts as an important pinning point in the Ross Sea ice-sheet-shelf system, stabilizing grounding line retreat and encouraging lasting ice-shelf development.

  • 245. Grimm, Guido
    et al.
    Bouchal, Johannes M.
    Swedish Museum of Natural History, Department of Paleobiology.
    Denk, Thomas
    Swedish Museum of Natural History, Department of Paleobiology.
    Potts, Alastair
    Fables and foibles: A critical analysis of the Palaeoflora database and the Coexistence Approach for palaeoclimate reconstruction2016In: Review of Palaeobotany and Palynology, ISSN 0034-6667, E-ISSN 1879-0615, Vol. 233, p. 216-235Article in journal (Refereed)
    Abstract [en]

    The ‘Coexistence Approach’ is amutual climate range (MCR) technique combinedwith the nearest-living relative (NLR) concept. It has been widely used for palaeoclimate reconstructions based on Eurasian plant fossil assemblages; most of them palynofloras (studied using light microscopy). The results have been surprisingly uniform, typically converging to subtropical, per-humid or monsoonal conditions. Studies based on the Coexistence Approach have had a marked impact in literature, generating over 10,000 citations thus far. However, recent studies have pointed out inherent theoretical and practical problems entangled in the application of this widely used method. But so far little is known how results generated by the Coexistence Approach are affected by subjective errors, data errors, and violations of the basic assumptions. The majority of Coexistence Approach studies make use of the Palaeoflora database (the combination of which will be abbreviated to CA + PF). Testing results produced by CA + PF studies has been hindered by the general unavailability of the contents in the underlying Palaeoflora database; two exceptions are the mean-annual temperature tolerances and lists of assigned associations between fossils and nearest-living relatives. Using a recently published study on the Eocene of China,which provides the first and only insight into the data structure of the Palaeoflora database,we compare the theory and practice of Coexistence Approach using the Palaeoflora database (CA+PF).We show that CA+PF is riddled by association and climate data error.We reveal flaws in the application of the Coexistence Approach,which is often in stark contrast to the theory of the method. We show that CA + PF is highly vulnerable against numerous sources of errors, mainly because it lacks safeguards that could identify unreliable data. We demonstrate that the CA+PF produces coherent, pseudo-precise results even for artificially generated, randomplant assemblages. AlternativeMCR-NLR methods can surpass the most imminent deficits of the Coexistence Approach, and may be used as a stop-gap until more accurate bioclimatic and distribution data on potential Eurasian NLRs, and theoretically and statistically robust methods will become available. Finally, general guidelines are provided for the future application of methods using the mutual climatic range with nearest living relatives approach when reconstructing climate from plant fossil assemblages.

  • 246. Grímsson, F.
    Meller, Barbara (Contributor)
    Bouchal, Johannes M. (Contributor)
    Swedish Museum of Natural History, Department of Paleobiology.
    Grimm, Guido (Contributor)
    Combined LM and SEM study of the middle Miocene (Sarmatian) palynoflora from the Lavanttal Basin, Austria: Part III. Magnoliophyta 1 – Magnoliales to Fabales2015In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 54, p. 85-128Article in journal (Refereed)
    Abstract [en]

    Previous studies on the palynoflora from the Lavanttal Basin show that it contains a rich

    assemblage of spores and gymnosperm pollen. Present and ongoing investigations of

    dispersed angiosperm pollen suggest a high diversity within this group, and due to the

    excellent preservation of the material some rare pollen types are recognized. The Magnoliales

    to Fabales pollen record documented here contains 30 different taxa. Only a few pollen types

    are assigned to Magnoliids (four taxa); these are rare in the pollen record. Similarly, the

    Commelinids comprise five taxa and are also rare. Most of the angiosperm pollen originate

    from Eudicots, 21 taxa. Of the angiosperm taxa documented here, Magnolia , Carex ,

    Ranunculaceae, Platanus , Trochodendron , Buxus , Cercidiphyllum , Daphniphyllum ,

    Distylium , Fortunearia , Parrotia , Parthenocissus , Vitis , Euphorbia , Salix , and

    Papilionoideae are recorded for the first time from the Lavanttal Basin. This also includes the

    first fossil pollen record of Trochodendron  worldwide and the first reliable pollen record of

    Daphniphyllum . Several of the taxa described here had a wide Northern Hemispheric

    distribution from Eocene until the end of the Miocene. Also, key relatives of the fossil taxa

    are presently confined to humid warm-temperate environments, suggesting a very mild

    climate during the middle Miocene (Sarmatian) of the Lavanttal area. Some of the taxa

    encountered also support previous observations that the sediments of the Lavanttal Basin

    accumulated in a lowland wetland environment. This is based on pollen from aquatic taxa

    thriving in lakes, streams and swamps, and pollen of terrestrial plant taxa occupying margins

    of lakes and streams, backswamps, floodplains, river plains, and hummocks. Other 

     angiosperm pollen clearly originate from plants thriving on drier substrates, reflecting various

    vegetation units of the mixed evergreen/deciduous broad-leaved/conifer forests surrounding

    the wetland basin.

  • 247. Grímsson, F.
    Bouchal, Johannes M. (Contributor)
    Swedish Museum of Natural History, Department of Paleobiology.
    Meller, Barbara (Contributor)
    Zetter, Reinhard (Contributor)
    Combined LM and SEM study of the middle Miocene (Sarmatian) palynoflora from the Lavanttal Basin, Austria: part IV. Magnoliophyta 2 – Fagales to RosalesIn: Grana, ISSN 0017-3134, E-ISSN 1651-2049Article in journal (Refereed)
    Abstract [en]

    An ongoing investigation of the middle Miocene (Sarmatian) palynoflora from the Lavanttal Basin continues to show that it contains an extremely rich assemblage of angiosperm taxa. The Fagales to Rosales pollen record documented here contains 34 different taxa belonging to the Betulaceae (Alnus, Betula, Carpinus, Corylus, Ostrya), Fagaceae (Castanea, Fagus, Quercus Groups Cerris, Ilex, Cyclobalanopsis, Quercus/Lobatae), Juglandaceae (Engelhardioideae, Carya, Juglans, Pterocarya), Myricaceae (Morrella vel Myrica), Cannabaceae (Celtis), Elaeagnaceae (Elaeagnus), Rhamnaceae, Rosaceae (Prunus) and Ulmaceae (Cedrelospermum, Ulmus, Zelkova). Two of the pollen types represent extinct genera, Trigonobalanopsis and Cedrelospermum, and are also reported for the first time from the Lavanttal Basin along with pollen of Rhamnaceae and Prunus. The different types of Quercus pollen are now affiliated with Groups Cerris, Cyclobalanopsis, Ilex and Quercus/Lobatae based on sculpturing elements observed using scanning electron microscopy (SEM). Köppen signatures of potential modern analogues of the fossil Fagales and Rosales suggest a subtropical (Cfa, Cwa) climate at lower elevation and subsequent subtropical to temperate climate with altitudinal succession (Cfa→Cfb/Dfa→Dfb; Cwa→Cwb→Dwb) in the Lavanttal area during accumulation of the palynoflora. Most of the fossil taxa have potential modern analogues that can be grouped as nemoral and/or merido-nemoral vegetation elements, and the diversity of Fagales indicates a varying landscape with a high variety of niches.

  • 248. Grímsson, F.
    et al.
    Bouchal, Johannes M.
    Swedish Museum of Natural History, Department of Paleobiology.
    Grimm, Guido
    Zetter, Reinhard
    Evaluating the mid Miocene paleoclimate of Lower Carinthia (Austria) based on high resolution palynological studies from the Lavanttal Basin2016Conference paper (Other academic)
    Abstract [en]

    Köppen signatures (Denk et al. 2013, Grímsson et al. 2015) can be used to generalize the climatic niche occupied by potential modern analogues (PMA) of fossil plants (here: palynological) assemblages. The Köppen climate system distinguishes climate zones by certain abiotic parameters or combinations thereof and represents them in a three letter code referring to the general climate types (first letter), the seasonal distribution of precipitation (second letter) and the seasonal distribution or general level of warmth (third letter). Based on their Köppen signatures PMAs can be categorized as arctic-alpine, boreal, nemoral, meridio-nemoral, tropical-meridional, tropical, eurytropical, and/or semihumid meridional vegetation elements (see also Denk et al. 2013, Velitzelos et al. 2014, Grímsson et al. 2015). Based on the climatic preferences of their PMAs, the Fagales and Rosales lineages present at the Lavanttal site rule out tropical (A-)climates and climates with pronounced (summer) draught (B-, Cs-, Ds-climates). The same holds for boreal/subarctic climates with short but humid summers (Cfc, Dfc, Dfd, Dwc). The Fagales are represented by 23 lineages at the Lavanttal site including genera that are today composed (predominately or exclusively) of nemoral and meridio-nemoral elements. This points to climate conditions not unlike those found today in the lowlands and adjacent mountain regions of the (south-)eastern United States, the humid-meridional region of western Eurasia (e.g. northern Italy, Black Sea region, western Caucasus), central and southern China, or Honshu (Japan). These regions are characterised by subtropical conditions at lower elevations (Cfa-, Cwa-climates) and subsequent altitudinal successions: Cfa! Cfb/Dfa! Dfb in eastern United States, western Eurasia, central China and Japan, or Cwa! Cwb! Dwb in southern China. The climax vegetation in these areas are mixed mesophytic forests and various mixed evergreen/deciduous broad-leaved forests, characteristic for the humid and semi-humid, summer-rain areas of the meridional and nemoral zone. (Co-)Dominant genera in these forests are the various members of the northern hemispheric Fagales. Important indicator taxa include Fagus , one of the most common and widespread genera in temperate, mixed mesophytic forests of North America, China and Japan, and Quercus Group Ilex, a co-dominant group in the East Asian monsoon influenced, winter-dry or fully humid southern foothills of the Himalayas and montane regions of south-western and central China. Equally informative is Corylus, and the co-occurrence of Carya , Juglans , Pterocarya  and Engelhardioideae, pinpointing towards forests as today found in south-western China and the warm subtropical parts of the southeastern United States.

  • 249.
    Gueriau, Pierre
    et al.
    Univ Paris 06, CNRS, MNHN,CR2P,UMR 7207, Univ Paris 04,Ctr Rech Paleobiodiversite & Paleoe, 57 Rue Cuvier,CP 38, F-75005 Paris, France.;Museum Natl Hist Nat, 57 Rue Cuvier,CP 38, F-75005 Paris, France.;Univ Paris Saclay, IPANEMA, CNRS, Minist Culture & Commun,USR3461, F-91192 Gif Sur Yvette, France.;Synchrotron SOLEIL, BP 48 St Aubin, F-91192 Gif Sur Yvette, France..
    Rabet, Nicolas
    Univ Paris 06, Univ Paris 04, MNHN,BOREA,UMR 7208, UCBN,CNRS,IRD,Unite Biol Organismes & Ecosyst Aqu, 57 Rue Cuvier,CP 26, F-75005 Paris, France.;Museum Natl Hist Nat, 57 Rue Cuvier,CP 26, F-75005 Paris, France..
    Clement, Gael
    Univ Paris 06, CNRS, MNHN,CR2P,UMR 7207, Univ Paris 04,Ctr Rech Paleobiodiversite & Paleoe, 57 Rue Cuvier,CP 38, F-75005 Paris, France.;Museum Natl Hist Nat, 57 Rue Cuvier,CP 38, F-75005 Paris, France..
    Lagebro, Linda
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Vannier, Jean
    Univ Lyon 1, UMR CNRS 5276, Lab Geol Lyon Terre Planetes Environm LGLTPE, Geode, Campus LyonTech la Doua,2 Rue Dubois, F-69622 Villeurbanne, France..
    Briggs, Derek E. G.
    Yale Univ, Dept Geol & Geophys, POB 208109, New Haven, CT 06520 USA.;Yale Univ, Yale Peabody Museum Nat Hist, POB 208109, New Haven, CT 06520 USA..
    Charbonnier, Sylvain
    Univ Paris 06, CNRS, MNHN,CR2P,UMR 7207, Univ Paris 04,Ctr Rech Paleobiodiversite & Paleoe, 57 Rue Cuvier,CP 38, F-75005 Paris, France.;Museum Natl Hist Nat, 57 Rue Cuvier,CP 38, F-75005 Paris, France..
    Olive, Sebastien
    Royal Belgian Inst Nat Sci, Directorate Earth & Hist Life Palaeobiosphere & E, Rue Vautier 29, B-1000 Brussels, Belgium.;Univ Liege, Dept Geol, Evolut & Div Dynam Lab, B18,Allee Six Aout, B-4000 Liege, Belgium..
    Bethoux, Olivier
    Univ Paris 06, CNRS, MNHN,CR2P,UMR 7207, Univ Paris 04,Ctr Rech Paleobiodiversite & Paleoe, 57 Rue Cuvier,CP 38, F-75005 Paris, France.;Museum Natl Hist Nat, 57 Rue Cuvier,CP 38, F-75005 Paris, France..
    A 365-Million-Year-Old Freshwater Community Reveals Morphological and Ecological Stasis in Branchiopod Crustaceans2016In: Current Biology, ISSN 0960-9822, E-ISSN 1879-0445, Vol. 26, no 3, p. 383-390Article in journal (Refereed)
    Abstract [en]

    Branchiopod crustaceans are represented by fairy, tadpole, and clam shrimps (Anostraca, Notostraca, Laevicaudata, Spinicaudata), which typically inhabit temporary freshwater bodies, and water fleas (Cladoceromorpha), which live in all kinds of freshwater and occasionally marine environments [1, 2]. The earliest branchiopods occur in the Cambrian, where they are represented by complete body fossils from Sweden such as Rehbachiella kinnekullensis [3] and isolated mandibles preserved as small carbonaceous fossils [4-6] from Canada. The earliest known continental branchiopods are associated with hot spring environments [7] represented by the Early Devonian Rhynie Chert of Scotland (410 million years ago) and include possible stem-group or crown-group Anostraca, Notostraca, and clam shrimps or Cladoceromorpha [8-10], which differmorphologically fromtheirmodern counterparts [1, 2, 11]. Here we report the discovery of an ephemeral pool branchiopod community from the 365-million-year-old Strud locality of Belgium. It is characterized by new anostracans and spinicaudatans, closely resembling extant species, and the earliest notostracan, Strudops goldenbergi [12]. These branchiopods released resting eggs into the sediment in a manner similar to their modern representatives [1, 2]. We infer that this reproductive strategy was critical to overcoming environmental constraints such as seasonal desiccation imposed by living on land. The pioneer colonization of ephemeral freshwater pools by branchiopods in the Devonian was followed by remarkable ecological and morphological stasis that persists to the present day.

  • 250.
    Guillemette, Francois
    et al.
    Uppsala University, Sweden.
    von Wachenfeldt, Eddie
    Uppsala University, Sweden; Swedish University of Agriculture Science, Sweden.
    Kothawala, Dolly N.
    Uppsala University, Sweden.
    Bastviken, David
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Tranvik, Lars J.
    Uppsala University, Sweden.
    Preferential sequestration of terrestrial organic matter in boreal lake sediments2017In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 122, no 4, p. 863-874Article in journal (Refereed)
    Abstract [en]

    The molecular composition and origin has recently been demonstrated to play a critical role in the persistence of organic matter in lake water, but it is unclear to what degree chemical attributes and sources may also control settling and burial of organic matter in lake sediments. Here we compared the annual contribution of allochthonous and autochthonous sources to the organic matter settling in the water column and present in the sediments of 12 boreal lakes. We used the fluorescence properties and elemental composition of the organic matter to trace its origin and found a consistent pattern of increasing contribution of terrestrial compounds in the sediments as compared to the settling matter, with an annual average allochthony of similar to 87% and similar to 57%, respectively. Seasonal data revealed a predominance of in-lake-produced compounds sinking in the water column in summer. Yet only a slight concurrent decrease in the contribution of terrestrial C to lake sediments was observed during the same period, and sediment allochthony increased again to high levels in autumn. Our results reveal a preferential preservation of allochthonous matter in the sediments and highlight the role of lakes as sequesters of organic carbon primarily originating from the surrounding landscape.

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