Die Petrographie des Knollenmergel,Mittlerer Keuper,Trias

In Württemberg, the upper part of the Middle Keuper is referred to as “Knollenmergel” (= “nodular marl”, a marly claystone containing carbonate nodules), 24 samples were studied from a test well located near Hechingen. X-ray diffraction was used for the determination of the mineral composition of whole rocks and of the clay fractions. The coarser fractions were studied under the petrographic microscope. The fractions < 2π Ø consist chiefly of an mixed-layer mineral with illite and expandable, montmorillonite-like layers as the components. There are about 30 % of expandable layers. A low-angle reflection near 31 Å is indicative of considerable order among component-layer species approaching that of rectorite. In the lower part of the section, moderate amounts of sudoite are present in addition. Illite as a discrete phase could not be determined with certainty. The microscopic fractions consist partly of monomineralic grains of quarz, dolomite, and calcite. In addition, they contain considerable amounts of polymineralic aggregates, which were not dispersed by the rather mild disintegration method used in the present study. Accordingly, the rocks are claystones characterized by the same degree of lithification as those occurring in other parts of the Keuper in Württemberg. The interstratified mineral is tentatively derived from the erosion of a uniform body of volcanogenic material of Paleozoic age. On the basis of grain-size distribution, the Knollenmergel is a water-laid sediment. Eolian transport as advocated by some geologists can be excluded. The difficulties experienced with the Knollenmergel as a building ground are explained by the high percentage of the expandable interstratified mineral and the dearth of a genuine sand fraction.     

Quantitative Recovery of Elemental Sulfur and Improved Selectivity in a Chromium-Reducible Sulfur Distillation

Chromium-reducible sulfur (CRS) distillations are intended to recover only reduced inorganic sulfur compounds (RIS) including elemental sulfur. However, the quantitative recovery of elemental sulfur is not ensured in common CRS-distillations. The new method presented here was designed to remedy this deficiency. An increase in ethanol concentration assured the quantitative recovery of elemental sulfur in various forms and, in addition, all other RIS-compounds were quantitatively recovered. Furthermore, the selectivity of the procedure was improved by an additional filtration step to eliminate zinc particles from the Cr(II)-solution. Thus, the recovery of sulfates and organic sulfur compounds was significantly decreased by a factor of up to 35, depending on the compound analysed. Exhaustive testing with a variety of pure phases, rock and soil samples demonstrated the precision and accuracy of the new method. The new protocol eliminated the constraints of previous procedures. The improved distillation efficiency for elemental sulfur ensured the quantitative recovery of all RIS-compounds in a single-step distillation.     

Crust and upper mantle structure of the Bohemian Massif from the dispersion of seismic surface waves

Summary The phase velocity dispersion of Rayleigh waves for the Moxa-Vienna (MOX-VIE) and Moxa-Kaperské Hory (MOX-KHC) profiles, and of both Rayleigh and Love waves for the Kaperské Hory-Ksi (KHC-KSP) profile have been measured and inverted into models of shearwave velocity vs. depth. The three paths cross, respectively, the central part of the Bohemian Massif, its western margin, and the Bohemian Pluton and Cretaceous. For the MOX-VIE profile mean and lower crustal shear wave velocities of 3.7 and 3.9 km/s, respectively, a mean Moho depth of 34 km, and no existence of a low-velocity layer in the lower crust were found. The model obtained for the MOX-KHC profile is characterized by a slightly lower velocity in the lower crust (3.8 km/s), by a slightly lower Moho depth (32 km), and by the appearance of a weak low-velocity channel between 55 and 140 km. The crustal section of the final model for the KHC-KSP profile agrees well with the KHKS82 model derived by Novotný from results of DSS along international profile VII. Our final Rayleigh-wave model has significantly lower shear-wave velocities down to 215 km in the mantle. A systematic difference of 0.18 km/s between the average velocities of Rayleigh and Love waves has been revealed for the depth range from 30 to 215 km. Since almost no contamination of the fundamental Love mode with higher modes has been observed, and since the investigated structure hardly contains an unresolved system of thin, alternately low- and high-velocity layers, the cause of the difference is evidently polarization anisotropy of the upper mantle beneath the Bohemian Massif. It is recommended that the discussed investigations should be supplemented with data from the fan of KSP-GRF (Gräfenberg Array, Germany) paths and from the KHC-BRG (Berggiesshübel, Germany) profile.     

On the determination of heliographic positions and rotation velocities of sunspots

In an earlier paper of this series it was shown how the Wilson depression influences the determination of sunspot rotation velocities. Using this finding and the fact that stable recurrent sunspots show a very constant rotation velocity it is possible to determine the effect of wrong solar image radii on the determination of sunspot rotation velocities and correct them.Mitteilungen aus dem Kiepenheuer-Institut Nr. 238.     

Quantifizierung von Verwitterungsvorgängen

Zusammenfassung Geochemische Verwitterungsvorgänge vollziehen sich im wesentlichen in der wasserungesättigten Zone und im erdoberflächennahen Grundwasser. In diesem Bereich bestimmen klimatische, biologische, biochemische und geochemische Vorgänge die Zersetzung des Ausgangsgesteins. Als Transportmittel für gelöste und flüchtige Umsetzungsprodukte wirken Sickerwasser, Grundwasser und Grundluft.Zur Quantifizierung des Stofftransportes wurden im Felde die vertikale Feuchtigkeitsverteilung mit einer Neutronensonde ermittelt und mit Hilfe eines Rechenmodells die Sickerraten bestimmt. Zur Erfassung der geochemischen Vorgänge wurden mit unterschiedlich langen Lysimetern der Stoffaustrag aus den einzelnen Bodenhorizonten und mit Hilfe hydrologischer und hydrochemischer Messungen der Stoffaustrag aus dem Grundwassersystem pauschal ermittelt. Mit einer geeigneten Stahlsonde wurden CO₂-Konzentrationsverteilungen in der Grundluft gemessen und mit Hilfe eines Rechenmodells bodenhorizontspezifische CO₂-Produktionsraten errechnet.Geochemische Verwitterungsvorgänge, wie Abbau der organischen Stoffe, Kalklösung, Hydrolyse der Silikate und Adsorptionsvorgänge an Festsubstanzen werden für unterschiedliche Bodenhorizonte eines Podsols unter verschiedener Vegetation dargestellt. Anhand des quantifizierten CO₂-Haushaltes werden die engen Wechselbeziehungen zwischen Grundluft- und Sickerwasserzusammensetzung aufgezeigt.

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Geochemical weathering reactions take place in the unsaturated zone and shallow groundwater. In this region climatic, biological, biochemical and geochemical processes control the degradation of the primary rocks. The dissolved and volatile substances are transported with seepage water, groundwater and ground air.For quantification of the substance transport the vertical moisture distribution was measured with a neutron-probe and the soil horizon specific seepage rates were calculated with help of a mathematical model. To investigate the geochemical processes and the transport rates of dissolved substances lysimeters of different lengths were installed. Furthermore the bulk output of dissolved substances was determined with spring flow measurements and spring water analyses. A suitable steel probe was used for measuring the vertical CO₂-concentration distribution in the ground air and the horizon specific CO₂-production rates were determined with help of a mathematical model.Geochemical weathering processes, such as decomposition of organic substances, carbonate dissolution, hydrolysis of silicates and adsorption on solid substances are described for the different horizons of a podsol soil under various vegetations. The quantified CO₂-balance was used to show the interaction between ground air and seepage water composition.

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Résumé Des processus géochimiques d'altération se produisent en grande partie dans la zone d'eau non saturée et dans les eaux souterraines proches de la surface du sol. Dans ce domaine, ce sont les processus climatiques, biologiques, biochimiques et géochimiques qui déterminent la décomposition des roches originelles. Les moyens de transport des produits de décomposition dissous et volatils sont les eaux et l'air souterrains.Pour la quantification du transport de substances, on a déterminé dans le terrain, avec la sonde à neutrons la répartition verticale de l'humidité et on a calculé, à l'aide d'un modèle mathématique, les taux de percolation. Pour cerner les processus géochimiques, on a établi globalement, avec des lysimètres de longueurs différentes, les transports de substances à partir des différents horizons du sol et, à l'aide de mesures hydrologiques et hydrochimiques, le transport de substances à partir du système des eaux souterraines. Avec une sonde de métal appropriée, on a mesuré les répartitions de concentration en CO₂ dans l'air souterrain et on a calculé, à l'aide d'un modèle mathématique les taux de production en CO₂ spécifiques à chaque horizon du sol.On a représenté, pour différents horizons du sol d'un podsol à végétation différente, des processus géochimiques d'alteration tels que la désagrégation des substances organiques, la dissolution du calcaire, l'hydrolyse des silicates et les processus d'adsorption par des substances solides. La teneur en CO₂ quantifiée à servi à montrer les interactions étroites entre la composition de l'air souterrain et de l'eau de percolation.

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. , , , . , . . , , — . CO_{2 2}. , - , , , . ₂ .

     

Dynamic finite element analysis of three-dimensional soil models with a transmitting element

A method for the dynamic finite element analysis of a non-axisymmetric soil model with an axisymmetric boundary is presented. In the non-axisymmetric soil domain an arbitrary discretization with three-dimensional isoparametric solid elements is used. At the boundary a transmitting element is arranged. It is based on the semi-analytical element of Waas and Kausel. The transformation of the stiffness matrix of the Waas/Kausel element with cyclic symmetric displacements to general displacement fields is presented. For earthquake excitation the forces acting on the discretized domain are given. The method is illustrated by the dynamic analysis of an embedded box-type building. The distribution and magnitude of significant section forces are discussed.     

Illite authigenesis in sandstones of the Guaritas Allogroup (Early Paleozoic): Implications for the depositional age,stratigraphy and evolution of the Camaquã Basin (Southern Brazil)

Several analytical studies performed on alluvial-eolian sandstones of the Early Paleozoic Guaritas Allogroup (Camaquã Basin, southern Brazil) indicate illite to be abundant, showing different morphologies as authigenic grain rims and pore-bridging filaments. Authigenic illite separates of variable grain sizes from distinct stratigraphic intervals of the Guaritas Allogroup yielded ⁴⁰K–⁴⁰Ar ages from 521.7 ± 10.3 to 473.7 ± 9.4 Ma. These ages, interpreted to record the timing of illite authigenesis, are coincident with the age of emplacement of the Rodeio Velho andesites (470 ± 19 Ma). Moreover, field structures suggest interaction between hot, andesite lava flows and wet, poorly consolidated sediments of the Pedra Pintada Alloformation (lower strata of the Guaritas Allogroup). This set of data indicates that the Rodeio Velho volcanism could have been responsible for a widespread remobilization of interstitial fluids and consequent authigenic illite precipitation in the sandstones of the Guaritas Allogroup.     

Mobility of heavy metals in harbour sediments: an environmental aspect for the reuse of contaminated dredged sediments

Different methods to determine the source strength of two harbour sediment fractions were applied and are discussed with a focus on As, Cd, Cr, Co, Cu, Mo, Ni, Pb, and Zn. Four different batch experiments were performed with both the sandy and the silty fractions of harbour sediments sampled at the disposal site for dredged material in Bremen Seehausen, north Germany. In addition to the batch experiments a modified centrifugation tube was used in order to obtain pore water from the unsaturated silty fraction. Column experiments were run with the sandy fraction of the material under saturated and unsaturated conditions, irrigated with artificial acid rain water. The results show that the legal threshold value applying to Mo and Pb is not exceeded in any of the methods applied to the sandy or the silty fractions. As for the sandy fraction, Cr and Co were also below this limit. Cd, Ni, Cu and Zn exceeded the threshold values in some of the batch experiments applied to both fractions, depending on the pH value and the elution agent used in the experiment. All results obtained from saturated column leaching were below the respective threshold values; however, it should be noted that the pH was between 7 and 8 throughout the entire experiment. This pH also applied to the unsaturated column, with the exception of the first flush. This first sample had a pH value of 3.8, which was due to sulphide oxidation at the beginning of the experiment and led to strong leaching of all the elements under study. As a consequence, arsenic, Cu and Ni values exceeded their respective threshold values.