Quantification of biogeomorphic interactions between small-scale sediment transport and primary vegetation succession on proglacial slopes of the Gepatschferner,Austria

Proglacial slopes provide suitable conditions for observing the co-development of abiotic and biotic systems. The frequency and magnitude of geomorphic processes and plant composition govern this interplay, which is described in the model of biogeomorphic succession. In high mountain environments, this model has only been tested in a limited number of studies. The study aimed to quantify small-scale sediment transport via erosion plots along a plant cover gradient and to investigate the influence of sediment transport on plant communities. We aimed to generate quantitative data to test existing biogeomorphic models. Small-scale biogeomorphic interactions were investigated on 30 test plots of 2 × 3 m size on proglacial slopes of the Gepatschferner (Kaunertal) in the Austrian Alps during the snow-free summer months over three consecutive years. The experimental plots were established on slopes along a plant cover gradient. A detailed vegetation survey was carried out to capture biotic conditions, and specific sediment yield was measured at each plot. Species abundance and composition at each site reflected successional stages. Additional environmental parameters, such as terrain age, geomorphometry, grain size distribution, soil nutrients, and precipitation, were also included in the analyses. We observed two pronounced declines in geomorphic activity on plots with both above 30% and above 75% plant cover. Nonmetric multidimensional scaling showed distinct clusters of vegetation composition that mainly followed a successional gradient. Sites that were affected by high-magnitude geomorphic events showed different environmental conditions and species communities. Quantified process rates and observed species composition support the concept of biogeomorphic succession. The findings help to narrow down a biogeomorphic feedback window.     

The antiquity indicator argon‐40/argon‐36 for lunar surface samples calibrated by uranium‐235‐xenon‐136 dating

Abstract— Several solar gas rich lunar soils and breccias have trapped ⁴⁰Ar/³⁶Ar ratios >10, although solar Ar is expected to yield a ratio of <0.01. Radiogenic ⁴⁰Ar produced in the lunar crust from ⁴⁰K decay was outgassed into the lunar atmosphere, ionized, accelerated in the electromagnetic field of the solar wind, and reimplanted into lunar surface material. The ⁴⁰Ar loss rate depends on the decreasing abundance of ⁴⁰K. In order to calibrate the time dependence of the ⁴⁰Ar/³⁶Ar ratio in lunar surface material, the period of reimplantation of lunar atmospheric ions and of solar wind Ar was determined using the ²³⁵U‐¹³⁶Xe dating method that relies on secondary cosmic‐ray neutron‐induced fission of ²³⁵U. We identified the trapped, fissiogenic, and cosmogenic noble gases in lunar breccia 14307 and lunar soils 70001‐8, 70181, 74261, and 75081. Uranium and Th concentrations were determined in the 74261 soil for which we obtain the ²³⁵U‐¹³⁶Xe time of implantation of 3.25^+0.38_‐0.60 Ga ago. On the basis of several cosmogenic noble gas signatures we calculate the duration of this near surface exposure of 393 ± 45 Ma and an average shielding depth below the lunar surface of 73 ± 7 g/cm². A second, recent exposure to solar and cosmic‐ray particles occurred after this soil was excavated from Shorty crater 17.2 ± 1.4 Ma ago. Using a compilation of all lunar data with reliable trapped Ar isotopic ratios and pre‐exposure times we infer a calibration curve of implantation times, based on the trapped⁴⁰ Ar/³⁶Ar ratio. A possible trend for the increase with time of the solar ³He/⁴He and ²⁰Ne/²²Ne ratios of about 12%/Ga and about 2%/Ga, respectively, is also discussed.     

Noble gases in D’Orbigny, Sahara 99555 and D’Orbigny glass—Evidence for early planetary processing on the angrite parent body

We analyzed the spallogenic, trapped, fissiogenic and radiogenic noble gas components in various bulk samples of the angrites D’Orbigny and Sahara 99555 as well as in glass separates of D’Orbigny. The D’Orbigny glass samples show hints of solar-like noble gases, as deduced from the trapped elemental and Ne isotopic compositions; the bulk samples do not contain detectable amounts of trapped gases. These observations indicate that D’Orbigny experienced a complex history shortly after its formation 4.56 Ga ago. The glass of D’Orbigny most likely represents magma that rose from the interior of the angrite parent body (APB) and was quenched near the surface. Hence, the APB may contain—similar to the interior of Earth and Mars—solar noble gases. This would call into question the suggested trapping mechanism for solar noble gases in the Earth and Mars, which involves the solution of early atmospheres into magma oceans, due to the APB’s inability to retain a primordial atmosphere. The first detection of—possibly parentless—radiogenic excess ¹²⁹Xe and solar noble gases in the glass of D’Orbigny indicates that the interior of APB degassed to a lesser degree than the outer regions. Therefore primordially trapped, fossil ¹²⁹I was kept. The APB was not completely devolatilized. Sahara 99555 yields a cosmic-ray exposure age of 6.8 ± 0.3 Ma, while D’Orbigny was exposed to cosmic rays for 11.9 ± 1.2 Ma. Both ages are different than those found in the other angrites. Hence, the angrites analyzed so far sampled surface material from the APB that was ejected in at least five events. In contrast to the bulk sample, the D’Orbigny glass separates yield concordant ages of only 3.0 ± 1.1 Ma, apparently suggesting a pre-exposure of the host material. However, such a scenario is unlikely, due to very similar Mn-Cr ages found in the bulk and glass of D’Orbigny. Most likely, this discrepancy is the result of additional, secondary gas-free glass. Such glass might have been formed during the meteorite’s entry into the Earth’s atmosphere. Isotopically anomalous Xe due to the decay of ²⁴⁷Cm has not been found. The presence of ²⁴⁷Cm in glass of D’Orbigny has been suggested based on Pb isotope constraints.     

Occurrence and distribution of tetraether membrane lipids in soils: Implications for the use of the TEX86 proxy and the BIT index

A diverse collection of globally distributed soil samples was analyzed for its glycerol dialkyl glycerol tetraether (GDGT) membrane lipid content. Branched GDGTs, derived from anaerobic soil bacteria, were the most dominant and were found in all soils. Isoprenoid GDGTs, membrane lipids of Archaea, were also present, although in considerably lower concentration. Crenarchaeol, a specific isoprenoid membrane lipid of the non-thermophilic Crenarchaeota, was also regularly detected and its abundance might be related to soil pH. The detection of crenarchaeol in nearly all of the samples is the first report of this type of GDGT membrane lipid in soils and is in agreement with molecular ecological studies, confirming the widespread occurrence of non-thermophilic Crenarchaeota in the terrestrial realm. The fluvial transport of crenarchaeol and other isoprenoid GDGTs to marine and lacustrine environments could possibly bias the BIT index, a ratio between branched GDGTs and crenarchaeol used to determine relative terrestrial organic matter (TOM) input. However, as crenarchaeol in soils is only present in low concentration compared to branched GDGTs, no large effect is expected for the BIT index. The fluvial input of terrestrially derived isoprenoid GDGTs could also bias the TEX₈₆, a proxy used to determine palaeo surface temperatures in marine and lacustrine settings and based on the ratio of cyclopentane-containing isoprenoid GDGTs in marine and lacustrine Crenarchaeota. Indeed, it is shown that a substantial bias in TEX₈₆-reconstructed sea and lake surface temperatures can occur if TOM input is high, e.g. near large river outflows.     

Concerning the derivation of the KS-transformation

The Kustaanheimo-Stiefel (KS) transformation is shown to follow naturally from the general solution of the two-body motion if half-arguments are introduced. Application to collision orbits and to the exact triangular solutions of Lagrange (vide E. Stiefel and G. Scheifele: 1971,Linear and Regular Celestial Mechanics, Springer, Berlin-Heidelberg-New York, p. 23–35).Notations x Position vector (x, y, z) - r=|x| Distance from the origin - 1/2h Energy constant or Kepler motion - c Angular momentum vector of Kepler motion - t physical time ()^·=d/dt () - new independent variable ()=d/d () Note by editor: This is the well-known Three-dimensional regularization, published in 1965 by P. Kustaanheimo and E. Stiefel, Perturbation Theory of Kepler Motion Based on Spinor Regularization,J. reine angewandte Mathematik 218, 204. The present article was written during Professor Volk's stay at the Zurich Technische Hochschule in 1972, when he also celebrated his 80th birthday.     

Determination Of The Surface Drag Coefficient

This study examines the dependence of the surface drag coefficienton stability, wind speed, mesoscale modulation of the turbulent flux and method of calculation of the drag coefficient. Data sets over grassland, sparse grass, heather and two forest sites are analyzed. For significantly unstable conditions, the drag coefficient does not depend systematically on z/L but decreases with wind speed for fixed intervals of z/L, where L is the Obukhov length. Even though the drag coefficient for weak wind conditions is sensitive to the exact method of calculation and choice of averaging time, the decrease of the drag coefficient with wind speed occurs for all of the calculation methods. A classification of flux calculation methods is constructed, which unifies the most common previous approaches.The roughness length corresponding to the usual Monin–Obukhovstability functions decreases with increasing wind speed. This dependence on wind speed cannot be eliminated by adjusting the stability functions. If physical, the decrease of the roughness length with increasing wind speed might be due to the decreasing role of viscous effectsand streamlining of the vegetation, although these effects cannot be isolated from existing atmospheric data.For weak winds, both the mean flow and the stress vector often meander significantly in response to mesoscale motions. The relationship between meandering of the stress and wind vectors is examined. For weak winds, the drag coefficient can be sensitive to the method of calculation, partly due to meandering of the stress vector.     

Plastic debris collars on juvenile carcharhinid sharks (Rhizoprionodon lalandii) in southwest Atlantic

Three juvenile Brazilian sharpnose sharks (Rhizoprionodon lalandii) caught in gillnets in southeast Brazil, southwest Atlantic, were found with plastic debris rings around their gill or mouth region. The rings caused severe abrasion on the sharks' tissues as the animal grew, the collars probably hampering normal feeding and/or ventilation since two of the collared individuals were emaciated. The rings were identified as detachable lid parts from plastic bottles, likely thrown overboard by fishery and/or recreation boats. As several carcharhinid shark species dwells and reproduce in shallow waters, the impact of discarded plastic debris likely is greater on this shark type.     

Orogenically controlled sedimentation in the Lechtaler Kreideschiefer (Lechtal shale; Cretaceous) and geodynamics of the inner western NCA (Northern Calcareous Alps; Lechtal Alps)

Only recently have sedimentological studies been integrated with orogenic research. The analysis of the Lechtaler Kreideschiefer (Lechtal Shale; Lower Cretaceous) demonstrates that these sediments reflect orogeny. Subduction and compressive tectonics resulted in the formation of a nappe pile. Folding of the epicontinental shelf formed long syn- and anticlines. In contrast to the uplifting anticlines the synclines represent subsiding depocenters with continuous sedimentation. Sheet-like olistostromes migrated in a broad front towards the axes of the Inner-Calcalpine synclines. The line-source character of unchannelized clastic influx from anticlines is different from fault-scarp breccias, slope aprons and the point-source of fan models. Some olistostromes document the initial tectonic elimination of various depocenters and can be recognized below following tectonic units: The Lechtal and the Inntal Nappe, the Braunarlspitz Wedge, the Hasenfluh Klippe, the Krabachjoch Thrust Outlier. These tectonic bodies arose from apparent overturning (UeberfaltungBlumer, 1905; UntermuldungLeiss, 1988, 1989 1990) and lie on synclines filled with synorogenic sediments. The thrust distance is 5–10 km.After the transport of the Inntal Nappe into the depocenter of the Lechtal Syncline, the Upper-Cretaceous Muttekopf Gosau was deposited in a depression on the back of the Inntal Nappe. The basal Gosau marks a molasse. The axial plane of the Muttekopf Syncline coincides with that of the Lechtal Syncline. The framework of the dominant Lechtal Syncline does not just contain a Lower but also an Upper Cretaceous profile separated by the Inntal Nappe.The so-called Klesenza Window represents not a true tectonic window of uncovered Arosa Zone, but a deposit of Lechtal Shale with spilite olistoliths.

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Zusammenfassung Erst in jüngster Zeit wird die Sedimentologie in die Orogenese einbezogen. Die Lechtaler Kreideschiefer (Unter-/Mittelkreide) der Lechtaler Alpen wurden mittels der Beckenanalyse auf synorogene Ablagerungen untersucht. Die beginnende Faltung zerteilt den epikontinentalen Schelf in weithin aushaltende Synklinal- und Antiklinalzüge. Während die Antiklinalen als Hebungsareale in Erscheinung treten, akkumulieren die Synklinalen als Depozentren Sedimente mit durchgehenden Profilen. Eingeschaltete Olistostrome in Hemipelagiten entlang den Beckenachsen sind typisch für diese Intraplate-Tröge. Rezente Fächermodelle vom Kontinentalhang sind nicht vergleichbar. Olistostrome als finale orogene Serien wurden in den Depozentren unterhalb folgenden tektonischen Einheiten erkannt: Lechtal Decke, Braunarlspitz Schuppe, Hasenfluh Klippe, Inntal Decke, Krabach Masse, Laagers (Larsenn) Deckscholle.Nach der tektonischen Platznahme der westlichen Inntal Decke im ehemaligen Sedimentationsraum der Lechtal Synklinale wird dort nach einem Hiatus die Gosau der Oberkreide als Molasse abgelagert. Die Sedimentationsräume der Lechtal Synclinale/Synclinorium und der Muttekopf Gosau liegen in senkrechter Projektion, nur durch die Gesteinsplatte der Inntal Decke getrennt. Hiermit vergleichbar ist der NW-Rand der Lechtal Decke.Schuppen und Decken der Lechtaler Alpen entwickeln sich aus abgescherten Falten (Blumer, 1905), wobei die dislozierten Antiklinalfirste die Synklinalen mit ihrer Sedimentfüllung überfahren. Der Tektonismus beruht auf Subduktion.Das sogenannte Klesenza-Fenster stellt als Vorkommen der Lechtaler Kreideschiefer mit einem Schwarm von Spilit-Olistholithen kein echtes tektonisches Fenster dar.

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Résumé Ce n'est qu'à une époque récente que la sédimentologie a été intégrée aux recherches orogéniques. L'analyse des bassins, appliquée aux «Lechtaler Kreideschiefer» (Crétacé inférieur à moyen, Alpes de Lechtal) montre le caractère synorogénique de cette formation. Le début du plissement a engendré dans le shelf épicontinental une série d'anticlinaux et de synclinaux allongés. Tandis que les anticlinaux formaient des zones soulevées, les synclinaux ont constitué des aires subsidentes de sédimentation continue. Des olistostromes intercalaires mis en place tout le long de ces structures caractérisent ces bassins intraplaques. Ce dispositif n'est pas comparable aux modèles récents de dépôts en éventail effectués à partir du talus continental ou d'escarpements de failles. Certains de ces olistostromes peuvent être identifiés sous les unités tectoniques suivantes, dont la mise en place sur les aires de sédimentation synorogénique a marqué la fin de celles-ci: la nappe du Lechtal, l'écaille du Braunarlspitz, la clippe de Hasenfluh, la nappe de l'Inntal, la masse charriée de Krabach. La flèche de ces charriages est de 5 à 10 km. Le transport de la nappe de l'Inntal occidentale sur le bassin du synclinal du Lechtal a été suivi, après un hiatus, du dépôt, au Crétacé supérieur, de la formation molassique du Gosau du Muttekopf, dans une dépression située sur le dos de la nappe. Il en résulte que l'ensemble du Lechtal comporte une série crétacée inférieure et une série crétacée supérieure, séparées par la nappe de l'Inntal. La bordure nord-ouest de la nappe du Lechtal présente une disposition analogue.La prétendue «fenêtre de Klesenza» n'est pas une vraie fenêtre tectonique découvrant la zone d'Arosa, mais une zone d'affleurement des schistes des schistes de Lechtal accompagnés d'ophiolites spillitiques.

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Neue Aspekte zur Geodynamik und Deckenbildung als Ergebnis der Beckenanalyse von synorogenen Kreidevprkommen innerhalb der Nördlichen Kalkalpen (Österreich)

Zusammenfassung Die Beckenanalyse von Gosauvorkommen zeigt für die tiefere Gosau (Coniac-Unt.-Santon), daß Sedimentation und Biofazies vom vorgegebenen geomorphologischen Relief abhängen. Dieses erhält seine Prägung durch geodynamische orogenetische Prozesse im Untergrund, deren Motor die Subduktion penninischer Anteile ist. Fazielle Studien ergeben eine frühe Anlage von intraplate-Trögen, die zunächst den alluvialen Schutt von antiklmalen Erhebungen aufnehmen, bevor sich flachmarine Bedingungen einstellen. Durch sedimentologische und biofazielle Analysen ergibt sich eine Beckengeometrie von asymmetrischer Gestalt mit weiten flachen Nordschenkeln und steilen kurzen Südschenkeln. Dabei repräsentieren diese Becken den Muldenbereich von Flexuren. Die Anlage von Flexuren ist die Konsequenz der durch subduktive Vorgänge hervorgerufenen Raumverengung, wobei der Muldenbereich als Depotraum für synorogene Sedimente zur Verfügung steht. Diese Sedimente reagieren rasch auf Veränderungen der Liefergebiete und der Beckenmorphologie und verkörpern Zeugen jener orogenetischen Prozesse und Bewegungen, die sich bis an die Oberfläche der austroalpinen Krustenscholle durchpausen und damit das Sedimentationsgeschehen kontrollieren. Für manche Kreidevorkommen konnte somit eine direkte Beteiligung am Ausformungsprozeß von höchsten kalkalpinen Decken gezeigt werden, da sich aufgrund der Beckenanalyse die Entwicklung dieser Tröge dechiffrieren läßt. Die orogene Kompression führt zu Subsidenz und Versteilung der Beckenschultern, so daß die für intraplate-Tröge typischen Olisthostrome gebildet werden, die mit ihren teils riesigen Olistholithen tektonische Prozesse wie Abscherungen des Untergrundes markieren. Bruchdeformation und Abscherung bilden sich im Deformationsmaximum aus, so daß sich entlang listrischen Bewegungsflächen eine Deckenstapelung vollzieht. In Anlehnung anBlumer's Modell der Deckengenese durch Überfaltung (Blumer, 1905) wird hier unter besonderer Berücksichtigung der Unterströmungstheorie vonAmpferer (1906) undAmpferer &Hammer (1911) eineDeckenbildung durch »Untermuldung« vorgeschlagen. Jacobshagen (1986) beschrieb in den Helleniden die synorogenen sedimentären Prozesse in Abhängigkeit von der jeweiligen tektonischen Einheit. Die gleiche Art der Sedimentation mit einemSystempaar eines finalen Flyschs auf der tieferen tektonischen Einheit und einem Molassestadium auf der höheren tektonischen Einheit konnte in den Nördlichen Kalkalpen erkannt werden. Hier beendet der finale Flysch (d. h. synorogene Olisthostrome) die kontinuierliche Sedimentation auf der tieferen tektonischen Einheit, wohingegen nach einem Hiatus ein neuer Sedimentationszyklus mit der molasseähnlichen basalen Gosau im Coniac auf der höheren tektonischen Einheit einsetzt.Seit der Unterkreide offenbart das sedimentologische Geschehen als Zeitzeuge die Auflösung und Zerteilung eines epikontinentalen Schelfgebietes, dem infolge Einengung die Bildung eines Deckenstapels durch Unterschiebungen aufgezwungen wird.

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The basin analysis of the Gosau deposits demonstrates that the sedimentation and the biofacies depend in the lower series of the Gosau from the existing morphology being controlled by geodynamic orogenic processes in the basement. Thereby the subduction of the Penninic elements represents a dominating factor of orogeny.The facial studies reveal an early construction of intraplate troughs, at first collecting the alluvial debris of anticlinal elevations before epicontinental conditions can extend. Sedimentological and biofacial analysis indicates a basin geometry of asymmetric shape with flat northern limbs and short steep southern limbs. These basins represent the basin area of wide flexures. The construction of flexures is the response to the spatial shortening provoked by subductional processes, whereby the troughs act as depocentres of synorogenic sediments. While filling the compressional troughs these sediments quickly react to changes of the source areas and of the basin morphology and represent as a whole witnesses of orogenic movements which trace over up to the surface of the Austroalpine block and control the dynamics of sedimentation.It was possible to demonstrate a direct participation of some Cretaceous deposits in the slow and steady processes of modelling some highest tectonic units of the Northern Calcareous Alps.The orogenic compression leads to subsidence and steepening of basin flanks. The olistostromes being typical for intraplate troughs mark tectonic processes like the decollement of the basement with the incorporation of partly huge olistolithes. Fractional deformation and decollement develop in the centre of deformation after a long period of sole prevailing of bending stress; hence it follows the nappe piling along listric dislocation planes. Referring toBlumer's model of nappe genesis by overfolding (Blumer, 1905), here aformation of nappes is proposed by the process of »undertroughing« with special respect to the »Unterströmungstheorie« ofAmpferer (1906) andAmpferer &Hammer (1911). Jacobshagen (1986) described in the Hellenids the synorogenic sedimentary processes dependent on each tectonic unit. The same type of sedimentation with acouplet of a final flysch on the lower tectonic unit and a molasse stage on the higher unit could be found in the Northern Calcareous Alps. Here the final flysch (i.e. synorogenic olistostromes) terminates the continuous sedimentation on the lower tectonic unit, while after a hiatus a new sedimentation cycle starts with the molasse-like basal Gosau in the Coniacian on the higher unit.Since the Lower Cretaceous the sedimentology presents as a witness the break up of an epicontinental shelf area reacting to compression by forming a nappe pile.

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Résumé L'analyse de bassins, appliquée aux dépôts de Gosau montre, particulièrement dans la partie inférieure de cette série, que la sédimentation et le biofacies sont en relation avec le paléorelief; celui-ci résulte des processus géodynamiques dans le socle, processus dont le moteur est la subduction des unités penniques. L'étude des faciès révèle l'existence de dépressions intra-plaque initiales dans lesquelles se sont d'abord accumulés les produits alluviaux provenant de l'érosion des reliefs anticlinaux, avant que s'établissent des conditions néritiques épicontinentales. De l'étude sédimentologique et biofacielle se déduit une géométrie asymétrique des bassins, avec de larges flancs nord peu inclinés et des flancs sud raides et étroits. Ces bassins correspondent ainsi aux parties synclmales de larges flexures. Ces flexures sont une réponse au raccourcissement provoqué par le processus de subduction, et leurs parties synclinales sont les réceptacles des sédiments synorogéniques. Ces sédiments répercutent rapidement les changements qui surviennent dans leur aire d'origine et dans la morphologie du bassin; ils sont donc les témoins des mouvements orogéniques qui se sont développés jusqu'à la surface du bloc austro-alpin et ont déterminé la dynamique de la sédimentation. Il a été ainsi possible de montrer la connexion directe de plusieurs formations crétacées avec l'élaboration des nappes supérieures des Alpes calcaires. La compression orogénique provoque la subsidence et le redressement des flancs des bassins; dans ce contexte prennent naissance les olisthostromes, typiques des bassins intra-plaque qui, avec les olistholites parfois volumineux qui les accompagnent, témoignent du phénomène de décollement par rapport au socle. La déformation cassante et le décollement surviennent lors du maximum de la phase déformative, d'où résulte l'empilement des nappes de long de surfaces listriques. Par référence au modèle de Blumer de formation des nappes par »Überfaltung« (Blumer, 1905), l'auteur propose un modèle par »Untermuldung« avec référence à l' »Unterströmungstheorie« d'Amferer (1906) et d'Amperer etHammer (1911).Jacobshagen (1986) a décrit dans les Hellénides des processus sédimentaires synorogènes, en relation avec les unités tectoniques de même âge. Dans les Alpes calcaires septentrionales, on peut reconnaître le même type de sédimentation, comportant le duo: flysch terminal sur l'unité tectonique basse et molasse sur l'unité tectonique élevée. Le flysch terminal (c-a-d les olisthostromes synorogéniques) exprime ici la fin de la sédimentation continue sur l'unité tectonique basse, tandis que, après un certain hiatus, un nouveau cycle sédimentaire s'installe sur l'unité tectonique élevée avec le Gosau basal de type molassique ou Coniacien.A partir du Crétacé inférieur, la sédimentation témoigne du frationnement du shelf épicontinental qui réagit au raccourcissement par la formation d'un empilement de nappes.

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