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  • 1. Alwmark, Carl
    et al.
    Ormö, Jens
    Nielsen, Arne T.
    Shocked quartz grains in the early Cambrian Vakkejokk Breccia, Sweden—Evidence of a marine impact2019In: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 54, no 3, p. 609-620Article in journal (Refereed)
    Abstract [en]

    Here we present a study of the abundance and orientation of planar deformation features (PDFs) in the Vakkejokk Breccia, a proposed lower Cambrian impact ejecta layer in the North-Swedish Caledonides. The presence of PDFs is widely accepted as evidence for shock metamorphism associated with cosmic impact events and their presence confirms that the Vakkejokk Breccia is indeed the result of an impact. The breccia has previously been divided into four lithological subunits (from bottom to top), viz. lower polymict breccia (LPB), graded polymict breccia (GPB), top sandstone (TS), and top conglomerate (TC). Here we show that the LPB contains no shock metamorphic features, indicating that the material derives from just outside of the crater and represents low-shock semi-autochthonous bombarded strata. In the overlying, more fine-grained GPB and TS, quartz grains with PDFs are relatively abundant (2?5% of the grain population), and with higher shock levels in the upper parts, suggesting that they have formed by reworking of more distal ejecta by resurge of water toward the crater in a marine setting. The absence of shocked quartz grains in the TC indicates that this unit represents later slumps associated with weathering and erosion of the protruding crater rim. Sparse shocked quartz grains (<0.2%) were also found in sandstone beds occurring at the same stratigraphic level as the Vakkejokk Breccia 15?20 km from the inferred crater site. It is currently unresolved whether the sandstone at these distal sites is related to the impact or just contains rare reworked quartz grains with PDFs.

  • 2. Andréasson, Per-Gunnar
    et al.
    Allen, Ann
    Aurell, Oskar
    Boman, Daniel
    Ekestubbe, Jonas
    Goerke, Ute
    Lundgren, Anders
    Nilsson, Patrik
    Sandelin, Stefan
    Seve terranes of the Kebnekaise Mts., Swedish Caledonides, and their amalgamation, accretion and affinity2018In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 140, no 3, p. 264-291Article in journal (Refereed)
    Abstract [en]

    A major allochthon of the Scandinavian Caledonides, the Seve belt has traditionally been considered to be derived from the rifted margin and continent-ocean transition (COT) of Baltica. However, geochronological results obtained from its inferred northern equivalent, the Kalak Nappe Complex (KNC), have been taken to indicate an exotic affinity of this complex and of also Seve terranes, an interpretation adopted in recent palaeogeographic models. In the Kebnekaise Mts., the COT is represented by the Kebnekaise terrane composed of amphibolitized dykes of gabbro and dolerite of depleted magma source and rare felsic and ultramafic rocks. Coronitic dolerite and gabbro with abundant rutile suggest high pressures before or during amalgamation with the underlying Mårma terrane, composed of quartzofeldspathic gneisses intruded by mafic and granitic rocks, the latter including a previously dated c. 845 Ma-old granite. The granite mingled with mildly alkaline dolerites chemically similar to transitional basalts of continental rifts. Following emplacement at shallow (andalusite stability) crustal levels, the igneous complex and host rocks underwent extensive deformation, metamorphism within the sillimanite-kyanite stability field and local migmatization. The Kebnekaise and Mårma terranes amalgamated in early Ordovician as indicated by the U-Pb age of 487±7 Ma obtained from titanite fabrics of deformed granite in thrust vicinity, and by 40Ar-39Ar results. The pressure increase in both terranes suggests that amalgamation occurred during initial subduction and imbrication. Correlation of the Mårma terrane with the KNC is discussed. Results obtained in this study give no reason to ascribe an exotic affinity to the Seve terranes of the Kebnekaise Mts.

  • 3.
    Becher, Marina
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Olid, Carolina
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Klaminder, Jonatan
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Buried soil organic inclusions in non-sorted circles fields in northern Sweden: Age and Paleoclimatic context2013In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 118, no 1, p. 104-111Article in journal (Refereed)
    Abstract [en]

    Although burial of surface organic soil horizons into deeper mineral soil layers helps drive the long-term buildup of carbon in arctic soils, when and why buried horizons formed as result of cryoturbation in northern Sweden remain unclear. In this study, we used C-14 and Pb-210 dating to assess when organic matter was buried within non-sorted circles fields near Abisko in northern Sweden. In addition, we used aerial photos from 1959 and 2008 to detect eventual trends in cryogenic activities during this period. We found that organic matter from former organic horizons (stratigraphically intact or partly fragmented) corresponds to three major periods: 0-100 A. D., 900-1250 A. D., and 1650-1950 A. D. The latter two periods were indicated by several dated samples, while the extent of the oldest period is more uncertainty (indicated by only one sample). The aerial photos suggest a net overgrowth by shrub vegetation of previously exposed mineral soil surfaces since 1959. This overgrowth trend was seen in most of the studied fields (92 out of 137 analyzed fields), indicating that the cryogenic activity has mainly decreased in studied non-sorted circles fields since the 1950s. This latter interpretation is also supported by the absence of buried organic layers formed during the last decades. We suggest that the organic matter was buried during the transition from longer cold periods to warmer conditions. We believe these climatic shifts could have triggered regional scale burial of soil organic matter and thus affected how these soils sequestered carbon.

  • 4. Deng, J.
    et al.
    Li, C.
    Frolking, S.
    Zhang, Y.
    Bäckstrand, Kristina
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Crill, Patrick
    Stockholms universitet, Institutionen för geologiska vetenskaper.
    Assessing effects of permafrost thaw on C fluxes based on multiyear modeling across a permafrost thaw gradient at Stordalen, Sweden2014In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 11, no 17, p. 4753-4770Article in journal (Refereed)
    Abstract [en]

    Northern peatlands in permafrost regions contain a large amount of organic carbon (C) in the soil. Climate warming and associated permafrost degradation are expected to have significant impacts on the C balance of these ecosystems, but the magnitude is uncertain. We incorporated a permafrost model, Northern Ecosystem Soil Temperature (NEST), into a biogeochemical model, DeNitrification-DeComposition (DNDC), to model C dynamics in high-latitude peatland ecosystems. The enhanced model was applied to assess effects of permafrost thaw on C fluxes of a subarctic peatland at Stordalen, Sweden. DNDC simulated soil freeze-thaw dynamics, net ecosystem exchange of CO2 (NEE), and CH4 fluxes across three typical land cover types, which represent a gradient in the process of ongoing permafrost thaw at Stordalen. Model results were compared with multiyear field measurements, and the validation indicates that DNDC was able to simulate observed differences in seasonal soil thaw, NEE, and CH4 fluxes across the three land cover types. Consistent with the results from field studies, the modeled C fluxes across the permafrost thaw gradient demonstrate that permafrost thaw and the associated changes in soil hydrology and vegetation not only increase net uptake of C from the atmosphere but also increase the annual to decadal radiative forcing impacts on climate due to increased CH4 emissions. This study indicates the potential of utilizing biogeochemical models, such as DNDC, to predict the soil thermal regime in permafrost areas and to investigate impacts of permafrost thaw on ecosystem C fluxes after incorporating a permafrost component into the model framework.

  • 5. Doguzhaeva, Larisa A
    et al.
    Bengtson, Stefan
    Reguero, Marcelo A
    Mörs, Thomas
    An Eocene orthocone from Antarctica shows convergent evolution of internally shelled cephalopods.2017In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 12, no 3, article id e0172169Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: The Subclass Coleoidea (Class Cephalopoda) accommodates the diverse present-day internally shelled cephalopod mollusks (Spirula, Sepia and octopuses, squids, Vampyroteuthis) and also extinct internally shelled cephalopods. Recent Spirula represents a unique coleoid retaining shell structures, a narrow marginal siphuncle and globular protoconch that signify the ancestry of the subclass Coleoidea from the Paleozoic subclass Bactritoidea. This hypothesis has been recently supported by newly recorded diverse bactritoid-like coleoids from the Carboniferous of the USA, but prior to this study no fossil cephalopod indicative of an endochochleate branch with an origin independent from subclass Bactritoidea has been reported.

    METHODOLOGY/PRINCIPAL FINDINGS: Two orthoconic conchs were recovered from the Early Eocene of Seymour Island at the tip of the Antarctic Peninsula, Antarctica. They have loosely mineralized organic-rich chitin-compatible microlaminated shell walls and broadly expanded central siphuncles. The morphological, ultrustructural and chemical data were determined and characterized through comparisons with extant and extinct taxa using Scanning Electron Microscopy/Energy Dispersive Spectrometry (SEM/EDS).

    CONCLUSIONS/SIGNIFICANCE: Our study presents the first evidence for an evolutionary lineage of internally shelled cephalopods with independent origin from Bactritoidea/Coleoidea, indicating convergent evolution with the subclass Coleoidea. A new subclass Paracoleoidea Doguzhaeva n. subcl. is established for accommodation of orthoconic cephalopods with the internal shell associated with a broadly expanded central siphuncle. Antarcticerida Doguzhaeva n. ord., Antarcticeratidae Doguzhaeva n. fam., Antarcticeras nordenskjoeldi Doguzhaeva n. gen., n. sp. are described within the subclass Paracoleoidea. The analysis of organic-rich shell preservation of A. nordenskjoeldi by use of SEM/EDS techniques revealed fossilization of hyposeptal cameral soft tissues. This suggests that a depositional environment favoring soft-tissue preservation was the factor enabling conservation of the weakly mineralized shell of A. nordenskjoeldi.

  • 6.
    Elbrächter, Malte
    et al.
    Deutsches Zentrum für Marine Diversitätsforschung.
    Gottschling, Marc
    Department of Geosciences, Oslo university.
    Hildebrand-Habel, Tania
    University of Stavanger.
    Keupp, Helmut
    Abisko Scientific Research Station.
    Kohring, Rolf
    Freie Universität Berlin.
    Lewis, Jane
    University of Westminster.
    Meier, Sebastian
    Christian-Albrechts-Universität zu Kiel.
    Montresor, Marina
    Stazione Zoologica ‘A. Dohrn’, Napoli.
    Streng, Michael
    Uppsala universitet, Paleobiologi.
    Versteegh, Gerard
    Universität Hamburg.
    Willems, Helmut
    Universität Bremen.
    Zonneveld, Karin
    Universität Bremen.
    Establishing an Agenda for Calcareous Dinoflagellate Research (Thoracosphaeraceae, Dinophyceae) including a nomenclatural synopsis of generic names2008In: Taxon, ISSN 0040-0262, E-ISSN 1996-8175, Vol. 57, no 4, p. 1289-1303Article in journal (Refereed)
    Abstract [en]

    Calcareous dinoflagellates are considered to be a monophyletic group of peridinoid taxa that have the potential to produce calcified exoskeletal structures during the life cycle, or that derive from such forms. Frequently, these calcareous bodies are excellently preserved in the fossil record and have received increased attention during the past three decades with regard to their use in biostratigraphy, climate and environmental reconstruction. Fossil and extant taxa have been classified in various, partly concurring, systematic concepts, using character complexes of the theca, cyst wall ultrastructure and archaeopyle/operculum morphology. The significance of such character complexes is briefly discussed in the light of molecular data that have been accumulated during the past decade. Over the years, the number of published taxonomic names has increased, partly due to nomenclatural changes. We propose that the entirety of calcareous dinoflagellates, and non-calcareous relatives derived from them, is accommodated in a single family of the order Peridiniales, the Thoracosphaeraceae, combining the former segregated taxonomic units Calciodinelloideae, a subfamily within Peridiniaceae, and Thoracosphaerales, a separate dinoflagellate order. As a result of a meeting of calcareous dinoflagellate specialists, we outline major subjects that are in need of re-investigation and -evaluation (an Agenda for Calcareous Dinoflagellate Research). In order to contribute to a consistent and stable nomenclature and taxonomy of calcareous dinoflagellates, we list 97 published generic names assigned to known calcareous dinoflagellates in a nomenclatural synopsis, with species names indicating their types and information on type locality and stratigraphy. We evaluate the status of these names—whether validly published and, if so, whether legitimate—,a crucial first step for any revisionary work in the future.

  • 7.
    Erickson, Lance
    Gustavus Adolphus College.
    Mercury Dynamics In Sub-Arctic Lake Sediments Across A Methane Ebullition Gradient2014Independent thesis Basic level (degree of Bachelor)Student thesis
  • 8. JADWISZCZAK, Piotr
    et al.
    Mörs, Thomas
    Naturhistoriska riksmuseet, Enheten för paleobiologi.
    First report on quill pits in early penguins2016In: Antarctic Science, ISSN 0954-1020, E-ISSN 1365-2079Article in journal (Refereed)
  • 9. Ormö, J.
    et al.
    Minde, P.
    Nielsen, A. T.
    Alwmark, C.
    Resurge deposits associated with the shallow marine early Cambrian Vakkejokk impact, north Sweden2019In: Meteoritics and Planetary Science, ISSN 1086-9379, E-ISSN 1945-5100, Vol. 54, no 6, p. 1246-1261Article in journal (Refereed)
    Abstract [en]

    The lower Cambrian Vakkejokk Breccia is a proximal ejecta layer from a shallow marine impact. It is exposed for ~7 km along a steep mountainside in Lapland, northernmost Sweden. In its central parts, the layer is up to ~27 m thick. Here the breccia shows a vertical differentiation into (1) a lower subunit consisting of strongly deformed target sediments mixed with up to decameter size, mainly crystalline basement clasts (i.e., lower polymict breccia [LPB]); (2) a middle subunit consisting of a polymict, blocky to gravelly breccia, commonly graded (i.e., graded polymict breccia [GPB]), that, in turn, is sporadically overlain by (3) a few dm thick, sandy bed (i.e., top sandstone [TS]). Previous work interpreted the graded beds as deposited by resurging water during early crater modification. We made three short (<1.35 m) core drillings through the graded beds. The line-logging technique previously used on cores from other marine-target craters was complemented by logging of equal-sized cells in photos made along the cores. Granulometry and clast lithology determinations provide further evidence for the top beds of the breccia being resurge deposits. However, the magnitude of this resurge can only be assessed by future deep core drilling of the infill of the crater hidden below the mountain.

  • 10.
    Stein, Ruediger
    et al.
    Alfred Wegener Institute for Polar and Marine Research, Germany.
    Weller, Petra
    Alfred Wegener Institute for Polar and Marine Research, Germany.
    Backman, Jan
    Stockholms universitet.
    Brinkhuis, Henk
    Royal Institute for Sea Research, NIOZ, Netherlands.
    Moran, Kate
    University of Victoria, Canada.
    Pälike, Heiko
    University of Bremen, Germany.
    Cenozoic Arctic Ocean climate history: Some highlights from the Integrated Ocean Drilling Program Arctic Coring Expedition2014In: Earth and Life Processes Discovered from Subseafloor Environments / [ed] R. Stein, D. Blackman, F. Inagaki, H-C Larsen, Amsterdam: Elsevier , 2014, 1, p. 259-293Chapter in book (Refereed)
  • 11. Tegner, Christian
    et al.
    Andersen, Torgeir B.
    Kjøll, Hans Jørgen
    Brown, Eric L.
    Hagen-Peter, Graham
    Corfu, Fernando
    Planke, Sverre
    Torsvik, Trond H.
    A Mantle Plume Origin for the Scandinavian Dyke Complex: A “Piercing Point” for 615 Ma Plate Reconstruction of Baltica?2019In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 20, no 2, p. 1075-1094Article in journal (Refereed)
    Abstract [en]

    Abstract The origin of Large Igneous Provinces (LIPs) associated with continental breakup and the reconstruction of continents older than ca. 320 million years (pre-Pangea) are contentious research problems. Here we study the petrology of a 615?590 Ma dolerite dyke complex that intruded rift basins of the magma-rich margin of Baltica and now is exposed in the Scandinavian Caledonides. These dykes are part of the Central Iapetus Magmatic Province (CIMP), a LIP emplaced in Baltica and Laurentia during opening of the Caledonian Wilson Cycle. The >1,000-km-long dyke complex displays lateral geochemical zonation from enriched to depleted basaltic compositions from south to north. Geochemical modelling of major and trace elements shows these compositions are best explained by melting hot mantle 75?250 °C above ambient mantle. Although the trace element modelling solutions are nonunique, the best explanation involves melting a laterally zoned mantle plume with enriched and depleted peridotite lithologies, similar to present-day Iceland and to the North Atlantic Igneous Province. The origin of CIMP appears to have involved several mantle plumes. This is best explained if rifting and breakup magmatism coincided with plume generation zones at the margins of a Large Low Shear-wave Velocity Province (LLSVP) at the core mantle boundary. If the LLSVPs are quasi-stationary back in time as suggested in recent geodynamic models, the CIMP provides a guide for reconstructing the paleogeography of Baltica and Laurentia 615 million years ago to the LLSVP now positioned under the Pacific Ocean. Our results provide a stimulus for using LIPs as piercing points for plate reconstructions.

  • 12. Zaton, Michal
    et al.
    Niedzwiedzki, Grzegorz
    Blom, Henning
    Kear, Benjamin P.
    Boreal earliest Triassic biotas elucidate globally depauperate hard substrate communities after the end-Permian mass extinction2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6Article in journal (Refereed)
    Abstract [en]

    The end-Permian mass extinction constituted the most devastating biotic crisis of the Phanerozoic. Its aftermath was characterized by harsh marine conditions incorporating volcanically induced oceanic warming, widespread anoxia and acidification. Bio-productivity accordingly experienced marked fluctuations. In particular, low palaeolatitude hard substrate communities from shallow seas fringing Western Pangaea and the Tethyan Realm were extremely impoverished, being dominated by monogeneric colonies of filter-feeding microconchid tubeworms. Here we present the first equivalent field data for Boreal hard substrate assemblages from the earliest Triassic (Induan) of East Greenland. This region bordered a discrete bio-realm situated at mid-high palaeolatitude (> 30 degrees N). Nevertheless, hard substrate biotas were compositionally identical to those from elsewhere, with microconchids encrusting Claraia bivalves and algal buildups on the sea floor. Biostratigraphical correlation further shows that Boreal microconchids underwent progressive tube modification and unique taxic diversification concordant with changing habitats over time. We interpret this as a post-extinction recovery and adaptive radiation sequence that mirrored coeval subequatorial faunas, and thus confirms hard substrate ecosystem depletion as a hallmark of the earliest Triassic interval globally.

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