Meeresoptische Messungen während schwerer Stürme auf der Forschungsplattform “Nordsee” vom 14. November bis zum 8. Dezember 1980

Ocean Dynamics - Meeresoptische Messungen auf der Forschungsplattform “Nordsee” haben gezeigt, daß dort während schwerer Stürme, hauptsächlich durch den Einfluß...     

Development and changes in the Eastern Province of Saudi Arabia

Due to a particularly favourable geologic and tectonic setting in the Eastern Province, Saudi Arabia has the world largest oil reserves and is the third largest oil-producing nation in the world. Based on oil and gas revenues, the Kingdom experienced an overwhelming development during the last few decades, changing a desert country into a modern industrialized nation. Main characteristics of spatial changes are based on processes of urbanization and industrialization, on agricultural reclamations and infra-structural developments. Since the natural environment of deserts and semi-deserts in the Eastern Province is determined by an extremely sensitive equilibrium, environmental impacts, shortages in water resources, as well as limited human resources are causing basic problems, which will influence future developments.     

Rates of sulfur dioxide and particle emissions from White Island volcano,New Zealand,and an estimate of the total flux of major gaseous species

Airborne correlation spectrometry (COSPEC) was used to measure the rate of SO₂ emission at White Island on three dates, i.e., November 1983, 1230 ± 300 t/d; November 1984, 320 ± 120 t/d; and January 1985, 350 ± 150 t/d (t = metric tons). The lower emission rates are likely to reflect the long-term emission rates, whereas the November 1983 rate probably reflects conditions prior to the eruption of December 1983. The particle flux in the White Island plume, as determined with a quartz crystal microbalance/cascade in November 1983, was 1.3 t/d, unusually low for volcanic plumes. The observed plume particles, as shown from scanning electron microscopy, include halite, native sulfur, and silicates and are broadly similar to other volcanic plumes.Gas analyses from high-temperature volcanic fumaroles collected from June 1982 through November 1984 werde used together with the COSPEC data to estimate the flux of other gas species from White Island. The rates estimated are indicative of the long-term volcanic emission, i.e., 8000–9000 t/d H₂O, 900–1000 t/d CO₂, 70–80 t/d HCl, 1.5–2 t/d HF, and about 0.2 t/d NH₃. The long-term thermal power output at White Island is estimated at about 400 MW.     

The stream function and Gauss' principle of least constraint: Two useful concepts for structural geology

To the extent that rock deformation can be approximated by a two-dimensional Newtonian model, a powerful stream-function simulation method is applicable. The significance of stream functions is that velocity, strain, stress and energy derived from the same stream function satisfy automatically three basic conditions of dynamics:

1. (1) the condition of continuity.

2. (2) the Navier-Stokes equations.

3. (3) conservation of energy.

Hence we state with Jaeger: “If a stream function can be found which satisfies the boundary conditions of a dynamic model the complete solution follows.” All pertinent bits of dynamic information are implied in the stream function from which they can be directly derived, guaranteed—so to speak—not to violate the basic conditions of dynamics. Stream functions useful in structural geology are solutions of: A double-polynomial solution of max. degree 14 is developed, in which the coefficients are related controlled by the ⁴ψ = 0 constraint, and their absolute values are determined by the boundary conditions of specific models and by the condition of maximum rate of energy dissipation or maximum rate of decline of potential energy. The polynomial stream function is applied to a collapsing viscous “nappe” consisting of a thin basal layer with low viscosity on which a thicker layer with high viscosity slides due to gravitational spreading. The velocity of forward movement depends upon absolute and relative values of the following parameters: viscosity, thickness, the aspect ratio and density. The velocity of a variety of nappes with different thicknesses, aspect ratios, viscosities and densities is determined.     

Synthetic seismograms from generalized ray tracing1

A new method of numerical computation of elastic wavefields in regions containing caustics is tested. The method is an extension of the asymptotic ray theory (ART). The essential features of the method consist of the application of expressions which are well defined at caustics and expressed in terms of ray tracing combined with complex ray tracing in caustic shadows. The method and an outline of the underlying theory are briefly presented, followed by a comparison with finite differences on a test model involving a caustic cusp. The comparison reveals the unexpectedly high degree of accuracy of the new method.     

Excess K-Ar ages of glauconite from the Upper Marine Molasse and evidence for glauconitization of mica

K-Ar age determinations along with optical investigations were used to examine whether glauconite from the Upper Marine Molasse (OMM) is of authigenic, allogenic or transformed origin. For this purpose 16 glauconite samples from 14 different localities were investigated from the Burdigalian Muschelsandstein collected along a traverse from Lake Constance to west of Geneva.Optical observations on washed grain concentrates reveal the presence of different alteration products of biotite, confirming earlier studies. Moreover, thin-section preparations of sample aliquots showed that the glauconite grains contain biotite-relics, which might account for the elevated absolute ages.The optical evidence is confirmed by individual mineral fractions, which show chlorite with biotite-»nucleii«, chlorite-lamellae, and »layered«-glauconites. All these observations point to glauconite genesis by transformation of biotite. The complete transformation from biotite via chlorite to glauconite apparently results in a chemically more stable state.The K-content of the samples varies from 5.6 to 7.0% K₂O, indicating mature but not highly evolved glauconite. 19 apparent K-Ar dates range from 17.7 to 34.9 Ma. In comparison with the biostratigraphy and the estimated Burdigalian age of about 18 Ma nearly all dates are too high. These strongly scattered dates are thus stratigraphically meaningless and seem to exclude an authigenic formation of these glauconites from faecal pellets. Furthermore, geologic arguments exclude an allogenic (= detrital) origin.Glauconite genesis in the Upper Marine Molasse must therefore be distinguished from both authigenic and allogenic formation mechanisms. A new term »meta-allogenic« is therefore used to describe glauconite growth by transformation of allogenic mica.

---

Zusammenfassung Um zu prüfen, ob Glaukonite aus der Oberen Meeresmolasse (OMM) authigen, allothigen oder durch Umwandlung aus anderen Mineralien entstanden sind, wurden sie — nebst mineraloptischen und röntgenographischen Untersuchungen — mit der K-Ar-Methode datiert. Aus 14 verschiedenen Lokalitäten zwischen Bodensee und einigen Kilometern westlich von Genf wurden 16 Glaukonit-Proben aus dem burdigalen Muschelsandstein entnommen.Sedimentpetrologische Studien an Körner-Konzentraten offenbarten verschiedene Umwandlungsprodukte von Biotit. Zudem zeigten Aliquots von Dünnschliff-Präparaten, daß einzelne Körner unterschiedlich große Relikte von Biotit enthalten, die die zu hohen Alterswerte verursachen können.Die verschiedenen Mineralfraktionen bestätigen den Charakter von Übergangsstadien: Chlorit mit Biotit-Kernen, Chloritlamellen und »Schicht«-Glaukonit. Alle diese Beobachtungen deuten auf eine Glaukonitgenese aus der Umwandlung von Biotit. Die vollständige Umwandlung von Biotit über Chlorit zu Glaukonit scheint mit dem End-produkt einen chemisch stabileren Zustand anzustreben.Der K₂O-Gehalt aller Proben variert von 5.6 bis 7.0%. Dies weist auf »reifen«, aber nicht hochentwickelten Glaukonit hin. Die 19 K-Ar-»Alter« liegen zwischen 17.7 und 34.9 Ma. Im Vergleich mit der Biostratigraphie und dem geschätzten burdigalen Alter von ca. 18 Ma, sind diese Daten zu hoch und daher stratigraphisch bedeutungslos. Eine authigene Bildung von Glaukonit aus Kotpillen (faecal pellets) muß somit ausgeschlossen werden. Außerdem kommt aus geologischen Gründen eine detritische (allothigene) Herkunft ebenfalls nicht in Betracht.Für die Glaukonit-Genese in der Oberen Meeresmolasse muß daher ein anderer Bildungsprozess verantwortlich sein. Um die Umwandlung von eingeschwemmtem (= allothigenem) Biotit zu Glaukonit zu beschreiben, wurde der neue Term »meta-allothigen« eingeführt.

---

Résumé Afin de rechercher si les glauconites de la OMM (= molasse marine supérieure) sont authigènes, allothigènes ou proviennent de la transformation d'autres minéraux, on les a datées par la méthode K-Ar, conjointement à une étude optique et röntgenographique. 14 localités, situées depuis de lac de Constance jusqu'à quelques kilomètres à l'ouest de Genève, ont fourni 16 échantillons de glauconite du Muschelsandstein burdigalien.L'étude optique des grains, effectuée sur des concentrés, a révélé divers produits de transformation de la biotite. En outre, les examens en coupes minces ont montré, dans les grains de glauconite, des restes de biotite d'importance variable. Ces restes de biotite peuvent être responsables de valeurs trop élevées obtenues dans les mesures d'âge.L'examen des diverses fractions minérales permet de préciser les stades de transformation: chlorite avec noyaux de biotite, lamelles de chlorite et glauconite »stratifiées«. Toutes ces observations indiquent une genèse de la glauconite par transformation de la biotite. La transformation complète de la biotite en chlorite puis en glauconite semble ainsi correspondre à un état chimique plus stable.La teneur en K₂O de tous les échantillons varie entre 5,6 et 7,0%, indiquant une glauconite »mature«, mais pas très évoluée. Les 19 »âges« K-Ar sont compris entre 17,7 et 34,9 Ma. Comparés à la biostratigraphie et à l'âge burdigalien, estimé à environ 18 Ma, ces résultats sont nettement trop élevés et ne présentent donc aucune valeur stratigraphique. Il faut ainsi exclure une formation authigène de la glauconite à partir de pelotes fécales. De plus, une origine détritique (= allothigène) ne peut être envisagée pour des raisons géologiques.En conséquence, c'est bien un processus différent qui est responsable de la genése de la glauconite dans la OMM. Le terme nouveau »méta-allogénique« est proposé pour indiquer la transformation de la biotite détritique en glauconite.

---

- , , , (OMM) , , /. 14- 16 . - . , . : , « ». , . , , . K₂O 5,6 7,0%. / 17,7 34,9 . , 18 . (faecal pellets) . , ., . , «-».

     

Dynamic behaviour of rigid foundations of arbitrary shape on a halfspace

An approximate method for computation of the compliance functions of rigid plates resting on an elastic or visco-elastic halfspace excited by forces and moments in all degrees of freedon is presented. The method is based on a Green's function approach. These functions are given for all degrees of freedom in form of well-behaved integrals. The numerical procedure is described and is used to evaluate the vertical, horizontal, rocking and torsion compliance functions of rectangular plates with side ratios 1 ≤ b/a ≤ 10 and non-dimensional frequency 0≤a₀≤10. It is shown how this method can be extended to problems concerning a linear visco-elastic halfspace and a halfspace with variable stiffness.     

Behavior of diorite under impact by variously-shaped projectiles

SummaryBehavior of Diorite Under Impact by Variously-Shaped Projectiles The effects of striker diameter and tip geometry on the crater and crack network produced in diorite by normal projectile impact in the energy range from 4–30 J was investigated. Ejecta kinematics were determined by high-speed photography; elastic strain wave propagation was measured by embedded gages in a composite specimen; and the damage pattern was ascertained from an examination of the sectioned specimen. It was found that the projectile nose shape exerts a strong influence on the shape of the elastic transient, on the crater geometry, on the extent of the crack network and on the average size of the ejecta. The crater depth was found to be the most repeatable parameter in identical tests using the same striker and initial kinetic energy.With 7 Figures