A discussion of the Alternating Field method and new paleointensity measurements of the Miocene geomagnetic field in Oregon

Summary Thirty eight cores from five Miocene lavas and their underlying baked zones from South Eastern Oregon have provided a test for the Alternating Field method of determining geomagnetic paleointensities, by allowing external consistency tests as well as internal consistency tests. All specimens were run regardless of the reliability tests results. The susceptibility change reliability test is useful as some of the specimens which failed it nevertheless gave misleadingly plausible results, but is shown to be unsufficient, as some specimens which were retained on that test failed to yield valid results. Different specimens from the same core behaved differently during the various experiments, proving that two specimens from a same core cannot reliably be assumed to be identical. A relation between the oxidation state and a change of susceptibility upon heating is seen.The paleofield intensities varied from 0.17±0.04 Oe and 0.31±0.08 Oe, corresponding to Virtual Dipole Moments of 1.23×10²⁵ to 2.15×10²⁵ Oe cm³. These low values are not accompanied by Virtual Geomagnetic Pole instability, but suggest an instability of the strength of the main dipole.     

Die Verwendung von Mineralen mariner Evaporite als Indikatoren der Luftfeuchtigkeit

Vapor-pressure measurements in the seawater system are used to show how far evaporites can be used as humidity indicators.

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Der Deutschen Forschungsgemeinschaft danken wir für eine Sachbeihilfe. Dr. H. Nielsen, Zentrallabor für Geochemie der Isotope, Göttingen, danken wir für Ratschläge beim Aufbau der Apparatur.     

Polymorphism of wollastonite

Different superstructures of wollastonite from the regional metamorphic Lepontine zone (Southern Alps) and other localities (e.g., Sierra Nevada, California) have been found. Besides well ordered normal 1T, 2M (2T ?), 4T-wollastonite, all disordered intermediate states exist. The various polymorphs were studied with the precession method. The superstructure is observed in reflections hkl k=odd. 4T-wollastonite is described with a ₀=31.659 Å and is shown to be a common polymorph. The superstructure seems to be independent of metamorphic grade (in the well-zoned Lepontine area it does not follow any mineralogical isograds) and occurs only in strained rocks with well developed lineation and strong preferred orientation. Thus the formation of the superstructure is explained as a deformation effect. Contrary to temperature and pressure, both stress and strain show large local variations and inhomogeneities. Experimental deformation of a 2T-wollastonite at 4 kb and 700° C produced complete disorder. It is suggested that consecutive annealing of strained disordered wollastonite causes periodic stacking sequences of [SiO₃]-chains along the a^*-axis. It appears from these studies that superstructures in chainsilicates are more common than presently known and that they might be useful petrogenetic indicators for the deformation and cooling history of a rock.     

Compressional angles of isallo stress theory for a circular-cylindrical,spherical and elliptic-cylindrical elastic inhomogeneity in an elastic medium

Summary The compressional angle of isallo stress theory for the case of a cylindrical (circular and elliptic) and spherical subsurface inhomogeneity, assuming that the conjugate fracture surfaces are inclined at a Mohr angle of 30° toward the largest compression, has been calculated. The solution for a spherical and cylindrical inclusion in an infinite medium subject to a uniform stress field (at infinity) were taken as the basis for the stress analysis. The stress angle was then calculated for the mentioned types of inclusions.     

Determination of magnitude by use of seismographs recording ground velocity

Summary Two electromagnetic seismographs HSJ-I, which are coupled with short-period galvanometers, record the velocity of the ground motion in the range of periods from 0.3 to 20 s in the seismological station Moxa. In this way the magnitude of an earthquake can be calculated without respect to the period of the ground motion. The results of such a determination of magnitudes are compared with those reached in the usual manner from short and long-period seismographs recording the ground displacement.Publication No. 45 of the Institut für Geodynamik, 69 Jena (DDR), Burgweg 11, der Deutschen Akademie der Wissenschaften zu Berlin, Forschungsgemeinschaft. Presented at the IUGG-Assembly, Zurich 1967.     

Gleichzeitige Messungen des Seegangs mit nicht-stabilisierten Beschleunigungsschreibern an Orten mit unterschiedlicher Wassertiefe in der Deutschen Bucht

Zusammenfassung Es werden Ergebnisse von simultanen Seegangsmessungen an sieben Pl?tzen mit verschiedener Wassertiefe im Küstengebiet der Deutschen Bucht behandelt. An Hand einiger Gegenüberstellungen wird dargelegt, in welcher Weise die Windsee mit abnehmender Wassertiefe niedriger und kürzer wird.

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Simultaneous measurements of waves by means of non-stabilized recording accelerometers at various places in the German Bight with different water depths

Summary Treated are the results of simultaneous measurements of waves at seven places in the coastal area of the German Bight with different water depths. A comparison demonstrates the way in which the wind sea is getting lower and shorter with decreasing water depth.

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Mesures simultanées de l'agitation de la mer avec accéléromètres enregistreurs non stabilisés en points de profondeurs différentes de la Baie Allemande

Résumé On a traité les résultats obtenus de mesures simultanées de l'agitation de la mer en sept endroits de profondeurs différentes dans les eaux c?tières de la Baie Allemande. En utilisant quelques comparaisons on expose de quelle manière la mer due au vent diminue de hauteur et de longueur en même temps que la profondeur.

     

Dünung und Windstau

Summary These remarks trie to explain the behaviour of local wind effect on the coast under the additional influence of swell approximately running parallel to the wind's direction. Owing to the high speed of long swell waves the wind's tangential shearing strain on the water masses may become less effective than it would do if no coincidence with swell waves would occur.

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La houle et l'effet local du vent

Résumé Cet essai cherche à expliquer le comportement de l'effet local du vent sous l'influence additionnelle d'une houle qui suit approximativement la direction du vent. Par suite de la grande vitesse de propagation d'une longue houle, l'effet de cisaillement tangentiel que le vent exerce sur l'eau diminuera dans le cas où l'effet local du vent coincide avec le phénomène additionnel de la houle.