The Glarus thrust: excursion guide and report of a field trip of the Swiss Tectonic Studies Group (Swiss Geological Society, 14.–16. 09. 2006)

This excursion guide results form a field trip to the Glarus nappe complex organized by the Swiss Tectonic Studies Group in 2006. The aim of the excursion was to discuss old and recent concepts related to the evolution of the Glarus thrust. The major aspects were (i) the interplay between deformation, fluid flow and geochemical alteration, (ii) episodic versus continuous deformation and fluid flow, and (iii) the link between large-scale structures, microstructures, and geochemical aspects. Despite 150 years of research in the Glarus nappe complex and the new results discussed during the excursion, there exist controversies that still are unsolved.     

Northwest Africa 11024—A heated and dehydrated unique carbonaceous (CM) chondrite

Based on the high abundance of fine‐grained material and its dark appearance, NWA 11024 was recognized as a CM chondrite, which is also confirmed by oxygen isotope measurements. But contrary to known CM chondrites, the typical phases indicating aqueous alteration (e.g., phyllosilicates, carbonates) are missing. Using multiple analytical techniques, this study reveals the differences and similarities to known CM chondrites and will discuss the possibility that NWA 11024 is the first type 3 CM chondrite. During the investigation, two texturally apparent tochilinite–cronstedtite intergrowths were identified within two thin sections. However, the former phyllosilicates were recrystallized to Fe‐rich olivine during a heating event without changing the textural appearance. A peak temperature of 400–600 °C is estimated, which is not high enough to destroy or recrystallize calcite grains. Thus, calcites were never constituents of the mineral paragenesis. Another remarkable feature of NWA 11024 is the occurrence of unknown clot‐like inclusions (UCLIs) within fine‐grained rims, which are unique in this clarity. Their density and S concentration are significantly higher than of the surrounding fine‐grained rim and UCLIs can be seen as primary objects that were not formed by secondary alteration processes inside the rims. Similarities to chondritic and cometary interplanetary dust particles suggest an ice‐rich first‐generation planetesimal for their origin. In the earliest evolution, NWA 11024 experienced the lowest degree of aqueous alteration of all known CM chondrites and subsequently, a heating event dehydrated the sample. We suggest to classify the meteorite NWA 11024 as the first type 3 CM chondrite similar to the classification of CV3 chondrites (like Allende) that could also have lost their matrix phyllosilicates by thermal dehydration.     

Classification of CM chondrite breccias—Implications for the evaluation of samples from the OSIRIS‐REx and Hayabusa 2 missions

CM chondrites are complex impact (mostly regolith) breccias, in which lithic clasts show various degrees of aqueous alteration. Here, we investigated the degree of alteration of individual clasts within 19 different CM chondrites and CM‐like clasts in three achondrites by chemical analysis of the tochilinite‐cronstedtite‐intergrowths (TCIs; formerly named “poorly characterized phases”). To identify TCIs in various chondritic lithologies, we used backscattered electron (BSE) overview images of polished thin sections, after which appropriate samples underwent electron microprobe measurements. Thus, 75 lithic clasts were classified. In general, the excellent work and specific criteria of Rubin et al. (2007) were used and considered to classify CM breccias in a similar way as ordinary chondrite breccias (e.g., CM2.2‐2.7). In BSE images, TCIs in strongly altered fragments in CM chondrites (CM2.0‐CM2.2) appear dark grayish and show a low contrast to the surrounding material (typically clastic matrix), and can be distinguished from TCIs in moderately (CM2.4‐CM2.6) or less altered fragments (CM2.7‐CM2.9); the latter are bright and have high contrast to the surroundings. We found that an accurate subclassification can be obtained by considering only the “FeO”/SiO₂ ratio of the TCI chemistry. One could also consider the TCIs’ S/SiO₂ ratio and the metal abundance, but these were not used for classification due to several disadvantages. Most of the CM chondrites are finds that have suffered terrestrial weathering in hot and cold deserts. Thus, the observed abundance of metal is susceptible to weathering and may not be a reliable indicator of subtype classification. This study proposes an extended classification scheme based on Rubin’s scale from subtypes CM2.0‐CM2.9 that takes the brecciation into account and includes the minimum to maximum degree of alteration of individual clasts. The range of aqueous alteration in CM chondrites and small spatial scale of mixing of clasts with different alteration histories will be important for interpreting returned samples from the OSIRIS‐REx and Hayabusa 2 missions in the future.     

Experimental impact cratering: A summary of the major results of the MEMIN research unit

This paper reviews major findings of the Multidisciplinary Experimental and Modeling Impact Crater Research Network (MEMIN). MEMIN is a consortium, funded from 2009 till 2017 by the German Research Foundation, and is aimed at investigating impact cratering processes by experimental and modeling approaches. The vision of this network has been to comprehensively quantify impact processes by conducting a strictly controlled experimental campaign at the laboratory scale, together with a multidisciplinary analytical approach. Central to MEMIN has been the use of powerful two-stage light-gas accelerators capable of producing impact craters in the decimeter size range in solid rocks that allowed detailed spatial analyses of petrophysical, structural, and geochemical changes in target rocks and ejecta. In addition, explosive setups, membrane-driven diamond anvil cells, as well as laser irradiation and split Hopkinson pressure bar technologies have been used to study the response of minerals and rocks to shock and dynamic loading as well as high-temperature conditions. We used Seeberger sandstone, Taunus quartzite, Carrara marble, and Weibern tuff as major target rock types. In concert with the experiments we conducted mesoscale numerical simulations of shock wave propagation in heterogeneous rocks resolving the complex response of grains and pores to compressive, shear, and tensile loading and macroscale modeling of crater formation and fracturing. Major results comprise (1) projectile–target interaction, (2) various aspects of shock metamorphism with special focus on low shock pressures and effects of target porosity and water saturation, (3) crater morphologies and cratering efficiencies in various nonporous and porous lithologies, (4) in situ target damage, (5) ejecta dynamics, and (6) geophysical survey of experimental craters.     

Impact of clouds on the surface radiation balance of the Arctic Ocean

Summary The relationship between clouds and the surface radiative fluxes over the Arctic Ocean are explored by conducting a series of modelling experiments using a one-dimensional thermodynamic sea ice model. The sensitivity of radiative flux to perturbations in cloud fraction and cloud optical depth are determined. These experiments illustrate the substantial effect that clouds have on the state of the sea ice and on the surface radiative fluxes. The effect of clouds on the net flux of radiation at the surface is very complex over the Arctic Ocean particularly due to the presence of the underlying sea ice. Owing to changes in surface albedo and temperature associated with changing cloud properties, there is a strong non-linearity between cloud properties and surface radiative fluxes. The model results are evaluated in three different contexts: 1) the sensitivity of the arctic surface radiation balance to uncertainties in cloud properties; 2) the impact of interannual variability in cloud characteristics on surface radiation fluxes and sea ice surface characteristics; and 3) the impact of climate change and the resulting changes in cloud properties on the surface radiation fluxes and sea ice characteristics.With 11 Figures     

Experimentelle Untersuchungen über die Wasserausscheidung des Goldhamsters und ihre Beeinflussung durch meteorologische Vorgänge

Zusammenfassung Bei der Bestimmung der täglich von Goldhamstern ausgeschiedenen Harnmenge wurden Schwankungen beobachtet, die nicht von einem vorhandenen Tages- oder Jahresrhythmus der Hamster verursacht sein können. Diese Schwankungen traten stets bei allen Tieren, die sich im Versuch befanden, gleichmäßig auf, obwohl sie stets unter konstanten Bedingungen gehalten wurden. Dabei wurde festgestellt, daß sich nur der Wassergehalt des Harnes und damit die Konzentration änderte, während die Menge der ausgeschiedenen festen Stoffe gleich blieb. Die Ursache für diese Mengenschwankungen des Harnes konnte in einer Beeinflussung der Wasserausscheidung durch meteorologische Vorgänge gefunden werden, und zwar wurde festgestellt, daß der Wechsel zwischen einer hauptsächlich durch tagesrhythmische Strahlung bestimmten Witterung und einer vorwiegend durch aperiodisch überlagerte Advektiveinflüsse bestimmten Wetterlage eine statistisch gesicherte Wirkung auf den Organismus ausübt. Dagegen konnte eine Beziehung zu einem einzelnen Wetterelement nicht festgestellt werden.

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Summary With the determination of the urine quantity daily secreted by gold-hamsters, variations have been registered, which cannot likely be caused by an existing daily or annual rhythm of hamsters. These variations have shown a uniform shape with all animals experimented with, though having been kept under constant conditions. It could be found that only the water-percentage of the urine and with it the concentration varied, while the quantity of secreted solid particles remained unchanged. The cause for these variations of the urine quantity could be traced in an influence of the meteorological situation on the water secretion; it has been stated that the change between a weather condition, which is mainly determined by the diurnal rhythm of radiation, and one mainly determined by superimposed aperiodical advective influences, shows an effect on the organism which is statistically significant. A relation, however, to a particular weather element could not be traced.

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Résumé En déterminant la quntité d'urine journalière secrétée par des hamsters dorés, on a observé des variations qui ne pouvaient provenir d'un rythme journalier ou annuel propre aux hamsters Ces variations ont été observées uniformément chez tous les animaux avec lesquels on fit les expériences, bien qu'ils aient été soumis à des conditions constantes. On a remarqué que seul le pourcentage en eau, donc la concentration de l'urine variait, tandis que la quantité de matière solide restait la même. En outre, on a pu constater que ces variations de la quantité d'urine étaient causées par l'influence des conditions météorologiques sur la secrétion d'eau. Ainsi, on a observé que le changement d'une situation déterminée principalement par le rythme diurne du rayonnement à une situation déterminée surtout par des influences advectives apériodiques superposées, produisait un effet sur l'organisme; cet effect est significant au point de vue statistique, mais il n'a pas été possible d'établir une relation avec un élément météorologique déterminé.

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Mit 11 Textabbidlungen

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Nach einer Dissertation der Naturwissenschaftlichen Fakultät der Universität München, 1956.     

Beitrag zur Gliederung des Präkambriums in Minas Gerais

Zusammenfassung Aufnahmen im Kristallin südostwärts und südlich der EsphinhaÇo-Zone, ausgedehnt bis an die Südgrenze des Staates Minas Gerais, ergaben eine neue stratigraphische und tektonische Gliederung. Große Gebiete, die bisher als tiefstes Archaikum galten, erhielten ihre metamorphe Überprägung erst in der assyntischen Phase. Auch die vormetamorphe sedimentäre Substanz ist weithin algonkischen, wahrscheinlich neo-algonkischen Alters. Im Inneren besitzen diese Sedimente nur schwache epizonale Metamorphose und erlauben weitgehende stratigraphische Gliederung (Formationen Tiradentes, Carandaí, Barroso, Prados). Sie sind Überwiegend klastisch. Küstenwärts folgen die sedimentär-lithologisch gleichen, aber stärker (mesozonal) metamorphe Andrelandia-Serie und die katazonalen Juiz de Fora- bzw. Paraíba-Serien (Metamorphose charnockitisch bzw. mikroklingranitisch). Die Küstenzone stellt daher eine kristalline Zentralzone dar, von der aus die Bewegungen binnenwärts gerichtet sind. An der Westgrenze des Arbeitsgebietes erfolgt eine Virgation der Faltenzüge in Araxaiden und Paraibiden. Das ordovizische Alter der Füllung des Beckens des Rio SÃo Francisco (Bambuí) ist zu bezweifeln. Die EsphinhaÇo-Zone ist algomisch konsolidiert, die alt-algonkische Minas-Serie auf diese Zone beschränkt. Sie bildet, zusammen mit dem Bambuí-Becken, das Vorland der assyntischen Faltenzüge. Eine Aufgliederung des Archaikums ist begonnen; im bisher untersuchten Gebiet sind die archäischen Strukturen co-axial den jüngeren.     

Zur Resistenz von Blaualgen gegen kurzwellige Strahlung

Zusammenfassung 13 Klone von Blaualgen verschiedener taxonomischer Stellung (Chroococcales, Chamaesiphonales, Nostocales) und verschiedener ?kologischer Gruppen (Plankter, Litoralformen, Aerophyten schattiger und sonniger Standorte), wurden mit Gamma-und UV-Strahlen behandelt. Plankter erwiesen sich unabh?ngig von ihrer taxonomischen Stellung als wenig widerstandsf?hig: Die maximale Gammastrahlentoleranz betrug je nach Klon 65 bis 260 krad bei Bestrahlungszeiten von rund 10 bis 40 Minuten, die maximale UV_Strahlentoleranz belief sich (mit einer Ausnahme) unter unseren Versuchsbedingungen auf eine Bestrahlungszeit von 32 Minuten. Begleitbakterien tolerierten durchwegs h?here Strahlendosen. Dagegen erwiesen sich Aerophyten bzw. Lithophyten von Standorten mit extremem natürlichem Strahlungsklima auch im Experiment als sehr resistent. So überlebtenChamaesiphon polonicus undScytonema burmanicum siebenstündige Exposition in Gammastrahlen (totale Dosis 2500 krad) sowie vierstündige UV-Bestrahlung. Begleitbakterien überlebten zwar die UV-Behandlung, nicht aber die hohen Gammastrahlendosen. Behandlung mit Gammastrahlen eignet sich daher zur Gewinnung axenischer Kulturen von Cyanophyten extremer Naturstandorte. Mehrere Monate alte axenische Kulturen vonScytonema burmanicum und vonS. lyngbyoides riechen übel, w?hrend bakterienhaltige Kulturen geruchlos bleiben. Vermutlich bauen die Begleitbakterien von den Algen ausgeschiedene, übelriechende Stoffwechselprodukte zu geruchlosen Verbindungen ab.

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Summary Thirteen strains of blue-green algae including members of the Chroococcales, Chamaesiphonales and Nostocales and belonging to various ecological groups have been exposed to various doses of gamma and UV radiation. Tolerances were independent of the taxonomic position but correlated with the ecological behaviour of the taxa involved. While planktonic species were quite sensitive to both UV and gamma radiation (maximum tolerance in the range of 65 to 260 krad) aerophytic and lithophytic species tolerated up to more than 2500 krad of gamma radiation and more than 4 hours of exposition to UV radiation. In cultures of planktonic species, gamma radiation killed the algae prior to the associated bacteria so that no axenic cultures could be obtained. In some cultures of aerophytic and lithophytic taxa however, bacteria were killed prior to the algae. Thus, axenic cultures of these strains could be obtained. Old axenic cultures ofScytonema burmanicum and ofS. lyngbyoides display a bad smell, whereas cultures with bacteria are odourless. Probably, the bacteria are reducing to odourless compounds the smelling substances excreted by the algae.

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Résumé Treize souches cloniques de Cyanophycées d’eau douce appartenant aux ordres des Chroococcales, des Chamaesiphonales et des Nostocales et représentant divers types écologiques à savoir des formes du plancton et du littoral ainsi que des espèces saxicoles aériennes et subaériennes de habitats ombreux et fort ensoleillés ont été traité aux rayons et UV. Les espèces planctoniques se montraient peu résistantes, indépendemment de leur position taxonomique: Dans nos conditions, elles supportaient au maximum 32 minutes d’irradiation de rayons UV, et, selon la souche clonique, de 65 à 260 krad de rayons gamma. Les bactéries accompagnant les algues supportaient partout des doses d’irradiation plus élevées. Par contre, les espèces saxicoles provenant de stations aériennes ou subaériennes se montraient très résistantes.Chamaesiphon polonicus etScytonema burmanicum par exemple supportaient dans nos conditions une irradiation UV de 4 heures et une exposition aux rayons gamma de 6 heures (dose totale: 2500 krad). Les bactéries accompagnant ces espèces supportaient les rayons UV, mais non les rayons gamma. Le traitement avec des rayons gamma peut donc aboutir à des cultures axéniques de Cyanophycées d’habitats aériens ou subaériens. Les cultures axéniques deScytonema burmanicum et deS. lyngbyoides agées de quelques mois sentent mauvais, tandis que les cultures parallèles dont les algues sont accompagnées de bactéries restent sans odeur. Il semble que les bactéries décomposent les substances d’odeur désagréable produites par les deux espèces.

     

Validating a rapid-update satellite precipitation analysis across telescoping space and time scales

In order to properly utilize remotely sensed precipitation estimates in hydrometeorological applications, knowledge of the accuracy of the estimates are needed. However, relatively few ground validation networks operate with the necessary spatial density and time-resolution required for validation of high-resolution precipitation products (HRPP) generated at fine space and time scales (e.g., hourly accumulations produced on a 0.25° spatial scale). In this article, we examine over-land validation statistics for an operationally designed, meteorological satellite-based global rainfall analysis that blends intermittent passive microwave-derived rainfall estimates aboard a variety of low Earth-orbiting satellite platforms with sub-hourly time sampling capabilities of visible and infrared imagers aboard operational geostationary platforms. The validation dataset is comprised of raingauge data collected from the dense, nearly homogeneous, 1-min reporting Automated Weather Station (network of the Korean Meteorological Administration during the June to August 2000 summer monsoon season. The space-time RMS error, mean bias, and correlation matrices were computed using various time windows for the gauge averaging, centered about the satellite observation time. For ±10 min time window, a correlation of 0.6 was achieved at 0.1° spatial scale by averaging more than 3 days; coarsening the spatial scale to 1.8° produced the same correlation by averaging over 1 h. Finer than approximately 24-h and 1° time and space scales, respectively, a rapid decay of the error statistics was obtained by trading-off either spatial or time resolution. Beyond a daily time scale, the blended estimates were nearly unbiased and with an RMS error of no worse than 1 mm day^?1.     

Thermal evolution of an ancient subduction interface revealed by Lue Hf garnet geochronology,Halilba■? Complex(Anatolia)

The thermal structure of subduction zones exerts a major influence on deep-seated mechanical and chemical processes controlling arc magmatism, seismicity, and global element cycles. Accretionary complexes exposed inland may comprise tectonic blocks with contrasting pressureetemperature(Pe T)histories, making it possible to investigate the dynamics and thermal evolution of former subduction interfaces. With this aim, we present new Lue Hf geochronological results for mafic rocks of the Halilbag?Complex(Anatolia) that evolved along different thermal gradients. Samples include a lawsoniteeepidote blueschist, a lawsoniteeepidote eclogite, and an epidote eclogite(all with counter-clockwise Pe T paths),a prograde lawsonite blueschist with a "hairpin"-type Pe T path, and a garnet amphibolite from the overlying sub-ophiolitic metamorphic sole. Equilibrium phase diagrams suggest that the garnet amphibolite formed at w0.6 -0.7 GPa and 800 -850℃, whereas the prograde lawsonite blueschist records burial from 2.1 GPa and 420℃ to 2.6 GPa and 520℃. Well-defined Lue Hf isochrons were obtained for the epidote eclogite(92.38 ± 0.22 Ma) and the lawsoniteeepidote blueschist(90.19 ± 0.54 Ma),suggesting rapid garnet growth. The lawsoniteeepidote eclogite(87.30 ± 0.39 Ma) and the prograde lawsonite blueschist(ca. 86 Ma) are younger, whereas the garnet amphibolite(104.5 ± 3.5 Ma) is older.Our data reveal a consistent trend of progressively decreasing geothermal gradient from granulite-facies conditions at ~104 Ma to the epidote-eclogite facies around 92 Ma, and the lawsonite blueschist-facies between 90 Ma and 86 Ma. Three Lue Hf garnet dates(between 92 Ma and 87 Ma) weighted toward the growth of post-peak rims(as indicated by Lu distribution in garnet) suggest that the HP/LT rocks were exhumed continuously and not episodically. We infer that HP/LT metamorphic rocks within the Halilbag?Complex were subjected to continuous return flow, with "warm" rocks being exhumed during the tectonic burial of "cold" ones. Our results, combined with regional geological constraints, allow us to speculate that subduction started at a transform fault near a mid-oceanic spreading centre. Following its formation, this ancient subduction interface evolved thermally over more than 15 Myr, most likely as a result of heat dissipation rather than crustal underplating.