Elektronenstrahl-Mikroanalyse des Meteoriten von Steinbach

Zusammenfassung Eine uns vom Naturhistorischen Museum in Wien freundlicherweise zur Verfügung gestellte Probe des Meteoriten von Steinbach wurde mit einem Elektronenstrahl-Mikroanalysator vom Typ CAMECA qualitativ und quantitativ auf die chemische Zusammensetzung der einzelnen Phasen untersucht.Besonders eingehend wurde dabei die Metallphase analysiert, da diese sich durch die Anwesenheit einer gut ausgebildeten Widmanstättenschen Struktur in Gegenwart von Tridymit als Druckindikator auszeichnet.Die nichtmetallischen Phasen wurden ebenfalls quantitativ bestimmt und ergeben leicht abweichende Ergebnisse von den Analysen vonN. Story-Maskelyne, O. Winkler undF. Heide. Interessant sind vor allem der relativ hohe Mangangehalt in Bronzit und Chromit sowie der Chromgehalt des Troilits.Die Anwendung der neuen Berechnungen über die Abkühlungsgeschichte der Meteoritenmutterkörper vonWood auf unsere quantitativen Analysen ergab eine Abkühlungsgeschwindigkeit von 10°/Million Jahre, was einem Mutterkörper von ca. 50–90 km Durchmesser und einem Zentraldruck von 200 b entspricht.

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Summary A sample of the meteorite of Steinbach, made available by the Naturhistorisches Museum at Vienna, has been analyzed qualitatively and quantitatively by a CAMECA electron-beam microanalyzer.Detailed examination has been made on the structure of the metal phase, as the presence of a well-grown Widmanstätten-structure in contact with trydimite as a pressure-indicator is a direct proof for the formation of the Widmanstätten-structure without pressure.The nonmetallic phases have been analyzed quantitatively and the results are slightly different from those ofStory-Maskelyne, Winkler andHeide. Very interesting is the relatively high content of manganese in bronzite and chromite, also the chromium content of troilite.The application of the new computations ofWood, dealing with the cooling history of meteorite-parentbodies to our quantitative analyses indicate a cooling rate of 10° C/Million years, according to a parentbody of appr. 50–90 km diameter and a central pressure of appr. 200 b.

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Mit 8 Textabbildungen

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Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet.     

Spectral and geological study of the sulfate-rich region of West Candor Chasma, Mars

Sulfates have been discovered by the OMEGA spectrometer in different locations of the planet Mars. They are strongly correlated to light toned layered deposits in the equatorial regions. West Candor Chasma is the canyon with the thickest stack of layers and one with the largest area covered by sulfates. A detailed study coupling mineralogy derived from OMEGA spectral data and geology derived from HRSC imager and other datasets leads to some straightforward issues. The monohydrated sulfate kieserite is found mainly over heavily eroded scarps of light toned material. It likely corresponds to a mineral present in the initial rock formed either during formation and diagenesis of sediments, or during hydrothermal alteration at depth, because it is typically found on outcrops that are eroded and steep. Polyhydrated sulfates, that match any Ca-, Na-, Fe-, or Mg-sulfates with more than one water molecule, are preferentially present on less eroded and darker outcrops than outcrops of kieserite. These variations can be the result of a diversity in the composition and/or of the rehydration of kieserite on surfaces with longer exposure. The latter possibility of rehydration in the current, or recent, atmosphere suggests the low surface temperatures preserve sulfates from desiccation, and, also can rehydrate part of them. Strong signatures of iron oxides are present on sulfate-rich scarps and at the base of layered deposits scarps. They are correlated with TES gray hematite signature and might correspond to iron oxides present in the rock as sand-size grains, or possibly larger concretions, that are eroded and transported down by gravity at the base of the scarp. Pyroxenes are present mainly on sand dunes in the low lying terrains. Pyroxene is strongly depleted or absent in the layered deposits. When mixed with kieserite, local observations favor a spatial mixing with dunes over layered deposits. Sulfates such as those detected in the studied area require the presence of liquid water to form by precipitation, either in an intermittent lacustrine environment or by hydrothermal fluid circulation. Both possibilities require the presence of sulfur-rich groundwater to explain fluid circulation. The elevation of the uppermost sulfate signatures suggests the presence of aquifers up to 2.5 km above datum, only 1 km below the plateau surface.     

Effects of lava flows on lunar crater populations

It is shown that endogenic lava flow processes can be identified by their characteristic effects on lunar crater size distributions without necessarily being able to recognise individual flows on the photographs studied. The thickness of lava flows or a series of flows can be estimated from these crater size distribution characteristics. The lava flow histories of the Apollo landing sites 11, 12 and 15 are discussed in detail. The thicknesses of the most recent (3–3.4 × 10⁹ years ago) flows there and of the youngest flows in an area in south-west Mare Imbrium (3 × 10⁹ years) are found to range between 30 and 60 m. The subsequent flow episodes at the landing sites showing up in the crater size distributions can be related to differences in the radiometric ages of the respective lunar rocks.     

Mass fluxes of xenobiotics below cities: challenges in urban hydrogeology

Urban areas are the focus of major ecological, social and economical activity. They are thus also prime locations of increasing conflict with regard to water use and water protection. As a direct and/or indirect consequence of urban land use and human activity, urban water systems are frequently polluted with organic contaminants including waste water-born xenobiotics such as pharmaceuticals, personal care products (collectively known as PPCPs) and endocrine-active substances. This study reviews new integrated methodologies including flux calculations as well as chemical investigations for determining the impact of human activities on urban water systems and on processes within the urban watershed. The use of indicator substances, representing different contaminant sources and pathways, integral pumping tests and mass balance approaches are suitable alternatives within these environments. The issues are explored using contaminant mass balance examples from Halle/Saale and Leipzig, Germany.     

Methane exchange between coal-bearing basins and the atmosphere: the Ruhr Basin and the Lower Rhine Embayment, Germany

A precise knowledge of methane exchange processes is required to fully understand the recent rise of atmospheric methane concentration. Three of these processes take place at the lithosphere/atmosphere boundary: bacterial consumption of methane and emission of bacterial or thermogenic methane. This study was initiated to quantify these processes on a regional scale in the Ruhr Basin and the Lower Rhine Embayment. Since these areas are subject to bituminous coal and lignite mining, natural and anthropogenically-induced methane exchange processes could be studied. The methane emission and consumption rates and their carbon isotope signal were measured at the lithosphere/atmosphere boundary using flux chambers. On most of the soils studied, methane consumption by bacteria was identified. Thermogenic methane was released only at some of the natural faults examined. In active and abandoned bituminous coal mining areas methane emissions were restricted to small areas, where high emission rates were measured. The carbon isotope composition of methane at natural faults and in mining subsidence troughs was typical of thermogenic methane (−45 to −32 ‰ δ¹³C). Methane exchange balancing revealed that natural methane emissions from these two basins represent no source of atmospheric importance. However, methane release by upcast mining shafts dominates the methane exchange processes and is by about two orders of magnitude greater than methane consumption by bacterial oxidation in the soils.     

Der Einfluß der Küstengestalt und des vorgelagerten Meeresbodens auf den windbedingten Anstau des Wassers,betrachtet am Beispiel der Westküste Schleswig-Holsteins

Zusammenfassung Die Einwirkung des Windes auf den Wasserstand bei Hochwasser entlang der deutschen Nordseeküste ist im allgemeinen verschieden. Die Gründe hierfür sind der ungleichmäßige Küstenverlauf und das von zahlreichen Prielen durchzogene flache Küstenvorland. Ausführliche Methoden zur Vorausberechnung des Windstaus unter Beachtung dieser morphologischen Bedingungen liegen noch nicht vor. Es wird deshalb ein Verfahren vorgeschlagen, den Windstau entlang der Küste im Anschluß an den Windstau eines geeigneten Bezugsortes zu bestimmen. Am Beispiel von acht Häfen der schleswig-holsteinischen Westküste wird gezeigt, daß dies mit gutem Erfolg möglich ist. Es wird eine Tabelle vorgelegt, die nach diesem Vorschlag beim Deutschen Hydrographischen Institut berechnet wurde und seit einiger Zeit für die Wasserstandsvorhersagen im Windstau- und Sturmflutwarndienst dieses Institutes verwendet wird. Die Tabelle enthält den Windstauunterschied der acht Orte gegen Cuxhaven in Abhängigkeit von Windrichtung und -stärke. Der Einfluß des Windes auf den Wasserstand wird für die Häfen einzeln besprochen. Die Untersuchung des Verhaltens der Häfen untereinander führt zur Aufstellung von sogenannten Normalgefällen. Abschließend werden Betrachtungen über die Genauigkeit des Verfahrens, die sich als befriedigend ergibt, angestellt.

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The influence exercised by the coast's shape and the topography of the tidal flats on the piling up of water due to stress of wind, exemplified by the conditions on the coast of Schleswig-Holstein

Summary The influences exercised by the wind on the water level at high water along the German North Sea coast show, in general, great differences which are due to the irregular coast line and the tidal flats with their numerous transversal tideways. Detailed methods of forecasting the piling up of water which take into consideration this sort of morphological conditions are so far not developed. Therefore, a method is proposed which permits to determine the piling up of water along the coast by relating it to the piling up at a suitable port of reference. Eight ports on the coast of Schleswig-Holstein are chosen as examples; they show that good results will be obtained from this method. A table is submitted which has been calculated by the German Hydrographic Institute in accordance with this proposal and which is used for the prediction of water level by the Storm Surge Warning Service of this institute. The table includes the difference in height of the piling up phenomenon at the eight places as compared with the data obtained at the port of Cuxhaven as a function of direction and strength of wind. The wind's influence on the water level at the different ports is discussed in detail. The behaviour of the eight ports is studied and a list of normal gradients is drawn up. In conclusion, the accuracy of the method is considered and is found to be satisfactory.

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L'influence de la configuration de la côte et des bas-fonds sur la montée du niveau due à la pression du vent, phénomène étudié à l'exemple de la côte du Schleswig-Holstein

Résumé La montée du niveau de la mer à l'époque de la pleine mer qui est causée par le vent subit, en général, des variations tout le long de la côte allemande de la mer du Nord. Les causes en sont le contour irrégulier de la côte et les bas-fonds traversés par beaucoup de petits chenaux de marée. Il n'existe pas encore de méthodes précises qui permettent à la fois de prédire la montée du niveau en tenant compte de ces conditions morphologiques. Donc, pour déterminer la montée du niveau le long de la côte, l'auteur propose un procédé qui se base sur la montée de niveau dans un port de référence convenable. A l'exemple de huit ports sur la côte d'ouest du Schleswig-Holstein, il montre que ce procédé donne de bons résultats. Une table est présentée qui fut calculée à l'Institut Hydrographique Allemand en conformité de cette proposition et qui y est employée depuis quelque temps pour les prévisions quotidiennes du niveau de la mer. La table contient les différences en montée du niveau entre les huit ports et le port de Cuxhaven en fonction de la direction et de la force du vent. L'influence du vent sur le niveau d'eau de chacun de ces huit ports est discutée. Le comportement des huit ports est étudie et il en résulte une table de gradients normaux. Enfin, l'auteur considère la précision du procédé qu'il trouve satisfaisante.

     

Fazieswechsel und Metamorphose in der westlichen Serra Negra (Espinhaço-Zone,Minas Gerais,Brasilien)

Zusammenfassung Es wird eine Übersichtskarte für die Serra Negra (Ostrand der Espinhaço-Zone) im Maßstab 1250 000 vorgelegt.Lithologische Faziesübergänge und das Vorkommen ultrabasischer bis basischer Gesteine belegen einen mio-/eugeosynklinalen Übergangsbereich der Minas-Geosynklinale. In der jüngeren, die Minas-Serie diskordant überlagernde São-Francisco-Serie (Macaúbas-Fazies) wurden erstmals magmatische Gesteine nachgewiesen.Die metamorphen Mineralneubildungen in der Minas-Serie weisen auf eine nach Osten zunehmende Regionalmetamorphose hin. Der größte Teil des Arbeitsgebietes liegt im Übergangsbereich Grünschiefer-/Amphibolit-Fazies.

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A regional study of the Serra Negra (eastern region of the Serra do Espinhaço) was carried out at the scale 1250 000.Lithologic facies changes and occurences of ultrabasic and basic rocks allow to delimit a mio/eugeosynclinal transition within the Precambrian Minas-Geosyncline. Within a post-Minas sequence (Macaúbas-Facies of the São Francisco Series) magmatic rocks have been encountered for the first time.Regional metamorphism within the Minas-Series is increasing to the east. The major part of the area belongs to a transitional zone between the greenshist- and amphibolite-Facies.

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Resumo Foi mapeada a região da Serra Negra (margem oriental da Serra do Espinhaço) na escala 1250 000.Mudanças de fácies, ocorrênicias de rochas ultrabásicas e básicas permitiram delimitar uma região de transição entre condições mio- e eugeossinclinais na Série Minas. Dentro da fácies Macaúbas, na Série São Francisco, discordante da Série Minas, foram reconhecidas rochas magmáticas pela primeira vez.O metamorflsmo regional da Série Minas cresce em direção leste. A maior parte da área em estudo situa-se na região de transição entre a fácies xisto verde e a anfibolítica.

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Serra Negra ( Espinhaco) 1 : 250000. / . - ( Macaubas), . . .

     

Verification of the Weather Research and Forecasting Model when Forecasting Daily Surface Conditions in Southern Alberta

The Weather Research and Forecasting (WRF) model was compared with daily surface observations to verify the accuracy of the WRF model in forecasting surface temperature, pressure, precipitation, wind speed, and direction. Daily forecasts for the following two days were produced at nine locations across southern Alberta, Canada. Model output was verified using station observations to determine the differences in forecast accuracy for each season.

Although there were seasonal differences in the WRF model, the summer season forecasts generally had the greatest accuracy, determined by the lowest root mean square errors, whereas the winter season forecasts were the least accurate. The WRF model generally produced skillful forecasts throughout the year although with a smaller diurnal temperature range than observed. The WRF model forecast the prevailing wind direction more accurately than other directions, but it tended to slightly overestimate precipitation amounts. A sensitivity analysis consisting of three microphysics schemes showed relatively minor differences between simulated precipitation as well as 2?m surface temperatures.