Der Untere Buntsandstein des Germanischen Beckens

Zusammenfassung Das Germanische Becken, das sich von der südlichen Nordsee bis nach Polen erstreckte, sank vom Perm bis einschließlich Trias mehr oder minder kontinuierlich ab. Die Absenkung wurde im Unteren Buntsandstein durch die Ablagerung von Klastika kompensiert, die vornehmlich aus dem sich hebenden südlichen Vorland herantransportiert wurden. Im allgemeinen nehmen die Korngrößen in Richtung Becken-Mitte ab, entsprechend der Entfernung zum Liefergebiet.In der Becken-Mitte bildete sich ein flacher, leicht übersalzener Playa-See, der häufig trockenfiel. Zu den Bändern hin herrschte ein fluviatiles Regime (braided rivers). Mariner Einfluß ist im zentralen und westlichen Teil nicht nachweisbar.Eingeschaltet in die sonst klastische Abfolge des Buntsandsteins sind zahlreiche niveaubeständige Oolith-Horizonte, die sich auf weite Entfernung korrelieren lassen. Das Maximum ihrer Verbreitung liegt südlich der Becken-Achse. Sie sind wahrscheinlich isochron sedimentiert worden und bildeten sich bei größerer Kalkübersättigung des Wassers und bei nachlassender oder fehlender Sedimentation von Klastika.Die fazielle Analyse der Oolith- und der sie begleitenden Stromatolith-Horizonte legt eine diskontinuierliche Zufuhr von Klastika nahe, die durch die unterschiedliche Hebungsintensität des Vorlandes gesteuert wird.

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The center of the Germanic Basin extended from the North Sea to Poland. The basin subsided more or less continuously from Permian to Triassic times. Subsidence was compensated during the Lower Buntsandstein by the deposition of clastic material, which arrived mainly from southern directions. Grain-sizes decrease toward the center correspondingly with the distance to the supplying area.The depositional environment of the basin was a shallow slightly hypersaline playa lake or inland sabkha with frequent periods of desiccation. Braided rivers dominated toward the rims. There is no marine influence in the central and western part of the basin.Numerous oolite-beds are intercalated in the usually clastic sequence of the Lower Buntsandstein. They occur within and mainly south of the basin center and can be traced over distances of more than 100 km and are used as marker horizons. They are associated with stromatolites and most likely deposited isochronously.Facies analysis suggests a discontinuous supply of clastic material to the basin, which is controlled by the temporally changing intensity of the uplift of the foreland. Oolites and stromatolites were formed during the intervals.

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Résumé La centre du bassin germanique s'étendait de la Mer du Nord jusqu'en Pologne. Le bassin subsidant de façon plus ou moins continue du Permien jusqu'en Triasique. Cette subsidence du Buntsandstein inferieur était compensé par la sedimentation clastique. Les sediments étaient provenaient principalement de la bordure meridionale du bassin en voie de soulèvement. Avec la distance de la source du matériel, on constate une diminuation de la grosseur des grains vers le centre du bassin.Au centre se développait un lac de playa hypersaline de faible profondeur, qui était souvent, desséché. Vers la bordure il existait une régime fluviatile (braided rivers). Une influence marine n'est décelable ni au centre ni dans la partie occidentale du bassin. Il y a de nombreux niveaux oolithiques (Rogenstein) qui peuvent être correlés sur de grandes distances. Leur plus grande répartition se trouve au sud de l'axe du bassin. Ils se sont vraisemblabement déposés de façon isochrone. La formation des oolites eut lieu quand l'eau était sursaturée en carbonate et pendant la diminuation ou même l'absence de la sédimentation clastique.L'analyse facielle suggère un apport clastique discontinu, controllé par les soulèvements variables de la bordure du bassin. La formation des oolithes et des stromatolithes est liée aux movements de l'activité tectonique minimale.

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Time patterns of polarization currents generated in measuring the electrical conductivity of rocks

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Numerical solution of the two-dimensional inverse geomagnetic induction problem

Summary An effective numerical approach to the solution of the two-dimensional inverse geomagnetic induction problem using the linearization method is presented. The numerical realization of the inversion is based on Marquardt's algorithm, for which the solution of the direct problem and the partial derivatives of this solution with respect to the electrical parameters of the medium are computed by the finite difference method. Theoretical models are studied and numerical results are presented.     

CATCHMENT-WIDE ANALYSIS OF THE SEDIMENT REGIME WITH RESPECT TO RESERVOIR SEDIMENTATION

1 INTRODUCTIONIn Anstria reservoirs are frequentiy multi-purpose schemes, being used for power generation, floodprotechon and for wate suPPly downstream. These reservoirs have some adVerse imPaCts on theenvironment around the reservoir and also on the dOwnstream pat:. in rivers with mean annual discharge above 30 m3ls about 36 % of the total length of l884 lQn isimpounded, and only 35% remains as free flowing sections (Muhar, l992),. flooding has been, and continues to be, a serious pr…     

Finite-difference modelling of magnetotelluric fields in two-dimensional anisotropic media

An algorithm for the numerical modelling of magnetotelluric fields in 2-D generally anisotropic block structures is presented. Electrical properties of the individual homogeneous blocks are described by an arbitrary symmetric and positive-definite conductivity tensor. The problem leads to a coupled system of partial differential equations for the strike-parallel components of the electromagnetic field. E _x, and H _x These equations are numerically approximated by the finite-difference (FD) method, making use of the integro-interpolation approach. As the magnetic component H _x, is constant in the non-conductive air, only equations for the electric mode are approximated within the air layer. The system of linear difference equations, resulting from the FD approximation, can be arranged in such a way that its matrix is symmetric and band-limited, and can be solved, for not too large models, by Gaussian elimination. The algorithm is applied to model situations which demonstrate some non-trivial phenomena caused by electrical anisotropy. In particular, the effect of 2-D anisotropy on the relation between magnetotelluric impedances and induction arrows is studied in detail.     

Area-preserving Poincaré mappings of the unit disk

The best way to investigate the long-time behaviour of dynamical systems is to introduce an appropriate Poincaré mapping P and study its iterates.Two cases of physical interest arise: Conservative and dissipative systems. While the latter has been considered by a great many authors, much less is known for the first one (according to Liouville's theorem, here the mapping leaves a certain measure in phase space invariant). In this paper, we concentrate our attention on compact phase spaces (or, rather, surfaces of section). This assumption is mathematically useful and physically reasonable.We consider the simplest possible (2-dimensional) systems whehre the phase space is the compact unit disk D in ². A family of simple area-preserving mappings from D onto itselves will be given and discussed in detail.It is shown that general characteristics of the dynamics are quite similar to those of e.g. the Hénon-Heiles system, while other features, as the structure of invariant curves, are different.     

A possible rotation period for the minor planet 164 Eva

The minor planet 164 Eva passed through opposition on December 1, 1975 with a magnitude B_opp = 11.3 mag. Photoelectric observations at the Observatory of Torino, Italy, were carried out in two nights on Oct. 27/28 and Nov. 11, each with a run of about 3 hr. Two further successful photoelectric observations were carried out at the OHP, France, each with a run of about 6 hr. From all observed parts of the lightcurve a resulting synodic period of rotation of about 27.3 hr can be deduced, with a range of the total amplitude of at least Δm = 0.07 mag. With this period of 27.3 hr the minor planet 164 Eva is one more long period object, falling now between 654 Zelinda (H. J. Schober, 1975, Astron. Astrophys.44, 85–89) and 139 Juewa (J. Goguen et al., 1976, Icarus29, 137–142), at the high end in the histogram of the distribution of minor planet rotation periods.     

A photometric investigation of the asteroid (89) Julia

New photometric data of the light curve of the minor planet (89) Julia were obtained on nine nights during the 1972 opposition using the 60cm telescope at OHP. A synodic period of 11^h23^m14^s ± 7^s and an amplitude of 0.25mag were derived from the measurements. The light curve is rather unsymmetric and no plausible explanation for this has been offered so far. The measurements have been carried out in instrumental V′; the data obtained in B′ and U′ supplement all conclusions from V′ data concerning the rotation of Julia.