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  • 1
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    Muséum national d'histoire naturelle
    In:  In: Stratigraphy and evolution of Peri-Tethyan platforms. , ed. by Crasquin-Soleau, S. Mémoires du Muséum national d'histoire naturelle, 177 . Muséum national d'histoire naturelle, Paris, pp. 129-150.
    Publication Date: 2019-10-15
    Type: Book chapter , NonPeerReviewed
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  • 2
    Publication Date: 2019-10-15
    Description: Highlights • Determination of the tectonomagmatic evolution of the NW Atlantic • Mapping of the breakup-related magmatism using the vocanostratigraphy concept • Mapping of the magnetic and gravimetric crustal domain patterns and their boundaries using integrated SGM method • Analyses of seabed and onshore samples and field analogues work • New plate tectonic reconstruction for the NW Atlantic Abstract Passive margins are the locus of tectonic and magmatic processes leading to the formation of highly variable along-strike and conjugate margins structures. Using extensive new seismic, gravity, and magnetic datasets, complemented by seabed samples and field work, we investigate the tectonomagmatic evolution of the northwest (NW) Atlantic where breakup-related igneous rocks were emplaced during several Paleogene events associated with lithospheric stretching, continental breakup, and the formation of new oceanic basins. Interpretational methods include integrated seismic-gravity-magnetic (SGM) interpretation and seismic volcanostratigraphy. In addition, seabed and field samples were collected and analyzed to constrain the basin stratigraphy, hydrocarbon potential, and the geochronology and geochemistry of the volcanic sequences. Offshore, 2D seismic data reveal several Seaward Dipping Reflector (SDR) wedges and escarpments in the Labrador Sea, Davis Strait, and Baffin Bay. Onshore, eastward prograding foreset-bedded hyaloclastite delta deposits and overlying horizontal lava successions outcrop on Nuussuaq. These hyaloclastites and lava successions are world class analogues to the Lava Delta and Landward Flows volcanic seismic facies units identified offshore. Our mapping results document an aerial extent of the Paleogene breakup-related volcanics of 0.3 × 106 km2, with an estimated volume of 0.5–0.6 × 106 km3. Basalt samples recovered by dredging the Upernavik Escarpment have late Paleocene to/early Eocene ages, whereas the sedimentary samples provide an excellent seismic tie with the stratigraphy and the geology in this frontier area. From the integrated SGM interpretation, we identify a rapidly thinning crust and changes in top and intra-basement seismic reflection characteristics in the oceanic domain correlated with transition between different magnetic domains. The mapping results were subsequently integrated in a plate tectonic model. The plate tectonic reconstruction and basalt geochronology suggest that the majority of the volcanism in the NW Atlantic occurred between ~62 and ~58 Ma, associated with an increased spreading rate in the Labrador Sea, starting from the onset of the Selandian (~61.6 Ma). A change in the spreading direction during the Eocene (~56 Ma), synchronously with a shift of volcanic activity from the NW to the NE Atlantic, correspond to a northward drift of Greenland and the initiation of the Eurekan Orogeny. Finally, our interpretations reveal a complex rift configuration along the NW Atlantic conjugate margins both prior to and during breakup.
    Type: Article , PeerReviewed
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  • 3
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    In:  (PhD/ Doctoral thesis), Christian-Albrechts-Universität Kiel, Kiel, 161 pp
    Publication Date: 2019-10-15
    Description: This PhD project investigates the impact of Fe limitation i) on heme b abundance in phytoplankton and marine particulate matter, and ii) on the production, utilization and degradation processes of heme b by field work and laboratory experiments. The main research questions driving this work are 1) Can heme b be used as a proxy of Fe limitation in field phytoplankton populations? 2) Is phytoplankton able to regulate their heme b pool to reduce Fe requirements under Fe limitation? 3) Does heme b regulation originate from a modification in the gene expression of proteins involved in its cycling?
    Type: Thesis , NonPeerReviewed
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  • 4
    Publication Date: 2019-10-14
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 5
    Publication Date: 2019-10-14
    Description: The chlorine isotope composition of Earth’s interior can place strong constraints on deep-Earth cycling of halogens and the origin of mantle chemical heterogeneity. However, all mantle-derived volcanic samples studied for Cl isotopes thus far originate from submarine volcanic systems, where the influence of seawater-derived Cl is pervasive. Here, we present Cl isotope data from subglacial volcanic glasses from Iceland, where the mid-ocean ridge system emerges above sea level and is free of seawater influence. The Iceland data display significant variability in δ37Cl values, from −1.8‰ to +1.4‰, and are devoid of regional controls. The absence of correlations between Cl and O isotope ratios and the lack of evidence for seawater-derived enrichments in Cl indicate that the variation in δ37Cl values in Icelandic basalts can be solely attributed to mantle heterogeneity. Indeed, positive correlations are evident between δ37Cl values and incompatible trace element ratios (e.g., La/Y), and long-lived radiogenic Pb isotope ratios. The data are consistent with the incorporation of altered lithosphere, including the uppermost sedimentary package, subducted into the Iceland mantle plume source, resulting in notable halogen enrichments in Icelandic basalts relative to lavas from adjacent mid-ocean ridges.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2019-10-14
    Description: Highlights: • Sponges, evolutionary basal animals, represent a reservoir of novel viral diversity • Viromes of neighboring sponges are individually unique and species specific • Phages encode ankyrins to aid bacteria in evading the eukaryotic immune system • Such “Ankyphages” are widespread in host-associated environments, including humans Summary: Phages are increasingly recognized as important members of host-associated microbiomes, with a vast genomic diversity. The new frontier is to understand how phages may affect higher order processes, such as in the context of host-microbe interactions. Here, we use marine sponges as a model to investigate the interplay between phages, bacterial symbionts, and eukaryotic hosts. Using viral metagenomics, we find that sponges, although massively filtering seawater, harbor species-specific and even individually unique viral signatures that are taxonomically distinct from other environments. We further discover a symbiont phage-encoded ankyrin-domain-containing protein, which is widely spread in phages of many host-associated contexts including human. We confirm in macrophage infection assays that the ankyrin protein (ANKp) modulates the eukaryotic host immune response against bacteria. We predict that the role of ANKp in nature is to facilitate coexistence in the tripartite interplay between phages, symbionts, and sponges and possibly many other host-microbe associations.
    Type: Article , PeerReviewed
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  • 7
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    GEOMAR Helmholtz Centre for Ocean Research
    In:  GEOMAR Helmholtz Centre for Ocean Research, 2 pp.
    Publication Date: 2019-10-14
    Description: 7.10.2019 - 13.10.2019
    Type: Report , NonPeerReviewed
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  • 8
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    American Geophysical Union
    In:  Journal of Geophysical Research, 94 (B5). pp. 5585-5602.
    Publication Date: 2019-10-14
    Description: We examine the closure of the current plate motion circuit between the African, North American, and Eurasian plates to test whether these plates are rigid and whether the Gloria fault is an active transform fault. We also investigate the possible existence of microplates that have been previously proposed to lie along these plate boundaries, and compare the predicted direction of motion along the African‐Eurasian plate boundary in the Mediterranean with the direction of slip observed in earthquakes. From marine geophysical data we obtain 13 transform fault azimuths and 40 3‐m.y.‐average spreading rates, 34 of which are determined from comparison of synthetic magnetic anomaly profiles to ∼140 observed profiles. Slip vectors from 32 earthquake focal mechanisms further describe plate motion. Detailed magnetic surveys north of Iceland provide 11 rates in a region where prior plate motion models had few data. Magnetic profiles north of the Azores triple junction record a rate of 24 mm/yr, 4 mm/yr slower than used by prior models. Gloria and Sea Beam surveys accurately measure the azimuths of seven transform faults; our plate motion model fits six of the seven within 2°. Two transform faults surveyed by Gloria side scan sonar lie near FAMOUS area transform faults A and B and give azimuths 13° clockwise of them. Because recent studies show that short‐offset transforms, such as transforms A and B, are in many places oblique to the direction of plate motion, we exclude azimuths from transforms with less than 35‐km offset. The best fitting and closure‐enforced vectors fit the data well, except for a small systematic misfit to the slip vectors: On right‐lateral slipping transforms, slip vectors tend to be a few degrees clockwise of plate motion and mapped fault azimuths, whereas on left‐lateral slipping transforms, slip vectors tend to be a few degrees counterclockwise of plate motion and mapped fault azimuths. We search the long Eurasia‐North America boundary for evidence of an additional plate, but find no systematic misfits to the data. In particular, if a Spitsbergen plate exists and moves relative to Eurasia, its motion is less than 3 mm/yr. An Africa‐Eurasia Euler vector determined by adding the Eurasia‐North America and Africa‐North America Euler vectors is consistent with the Gloria fault trend and with slip vectors from eastern Azores‐Gibraltar Ridge focal mechanisms. A small circle, centered at the Africa‐Eurasia closure‐enforced pole, fits the trace of the Gloria fault. The model in which closure was enforced predicts ∼4 mm/yr slip across the Azores‐Gibraltar Ridge, and west‐northwest convergence near Gibraltar, ∼45° more oblique than suggested by a recent model based on compressive axes of focal mechanisms. Moreover, our model predicts directions of plate motion that agree well with northwest trending slip vectors from thrust earthquakes between Gibraltar and Sicily. Because closure‐enforced vectors fit the data nearly as well as the best fitting vectors, we conclude that the data are consistent with a rigid plate model and with the Gloria fault being a transform fault.
    Type: Article , PeerReviewed
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  • 9
    Publication Date: 2019-10-14
    Description: Highlights • Common HIMU end member in adjacent continental and oceanic volcanic provinces. • End member St. Helena HIMU derived from deep upwelling(s)/plume(s). • Plateau collision & plume interaction with Gondwana active margin causes breakup. • Hybrid volcanic-tectonic margins resulted from Zealandia – Antarctica breakup. Abstract Margins resulting from continental breakup are generally classified as volcanic (related to flood basalt volcanism from a starting plume head) or non-volcanic (caused by tectonic processes), but many margins (breakups) may actually be hybrids caused by a combination of volcanic and tectonic processes. It has been postulated that the collision of the Hikurangi Plateau with the Gondwana margin ∼110 Ma ago caused subduction to cease, followed by large-scale extension and ultimately breakoff of the Zealandia micro-continent from West Antarctica through seafloor spreading which started at ∼85 Ma. Here we report new geochemical (major and trace element and Sr-Nd-Pb-Hf isotope) data for Late Cretaceous (99-69 Ma) volcanism from Zealandia, which include the calc-alkalic, subduction-related Mount Somers (99-96 Ma) and four intraplate igneous provinces: 1) Hikurangi Seamount Province (99-88 Ma), 2) Marlborough Igneous Province (98-94 Ma), 3) Westland Igneous Province (92-69 Ma), and 4) Eastern Chatham Igneous Province (86-79 Ma). Each of the intraplate provinces forms mixing arrays on incompatible-element and isotope ratio plots between HIMU (requiring long-term high U/204Pb) and either a depleted (MORB-source) upper mantle (DM) component or enriched continental (EM) type component (located in the crust and/or upper mantle) or a mixture of both. St. Helena end member HIMU could be the common component in all four provinces. Considering the uniformity in composition of the HIMU end member despite the type of lithosphere (continental, oceanic, oceanic plateau) beneath the igneous provinces, we attribute this component to a sublithospheric source, located beneath all volcanic provinces, and thus most likely a mantle plume. We propose that the plume material rose beneath the active Gondwana margin and flowed along the subducting lithosphere beneath the Hikurangi Plateau and neighboring seafloor and through slab tears/windows beneath the Gondwana (later to become Zealandia) continental lithosphere. We conclude that both plateau collision, resulting in subduction cessation, and the opening of slab tears/windows, allowing hot asthenosphere and/or plume material to upwell to shallow depths, were important in causing the breakup of Zealandia from West Antarctica. Combined tectonic-volcanic processes are also likely to be responsible for causing breakup and the formation of other hybrid type margins.
    Type: Article , PeerReviewed
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  • 10
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    GEOMAR Helmholtz Centre for Ocean Research Kiel
    In:  GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany, 3 pp.
    Publication Date: 2019-10-14
    Description: Walvis Bay - Recife, 07.10.-13.10.2019
    Type: Report , NonPeerReviewed
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