Phase boundaries in finite amplitude mantle convection

Summary. Phase boundaries are included in dynamical finite element models of mantle convection. They are represented by point chains which act as additional sources of buoyancy forces when distorted, and as additional source or sink of heat. The influence of the exothermic olivine-spinel transition is studied in both shallow and deep convection models. The flow is only slightly enhanced by the transition. The increase of temperature due to latent heat release is step-like in the deep model, in the case of shallow convection it is more diffuse. Other quantities like ocean-floor topography, gravity anomalies, and stress distribution are no more than moderately affected. In a further investigation the effect of spinel post-spinel transition, whether endothermic or exothermic, on deep convection is examined. The effect on the flow is negligibly small in both cases.     

The long-term dynamics of crustacean communities in Lake Constance (Obersee, 1962–1986)

The long-term development of crustacean associations in the Obersee of Lake Constance was studied at one central station from 1962 to 1986. In a simultaneously managed program with four additional stations from the eastern part (Bregenz Bay) to the western überlinger See mainly the differences in horizontal distribution were focussed. It was one aim of these investigations, to get an idea or an indication of a connexion between the recently observed eutrophication of the Obersee, and its crustacean communities. Due to the immigration of several species (cyclopids) or genotypes (Daphnia), the communities had changed in genetical structures, in reproduction rates and in predation or grazing impact. Dependent on the specific annual cycles, there resulted an extermination (Heterocope, Diaphanosoma), or a long-term decrease in annual means (Mesocyclops, Cyclops abyssorum) of the “old-settled” species. A general tendency was seen in an increase of annual averages until the middle of the seventies, and a following decrease of population density of most of the species. The horizontal differences in the species associations were remarkable. The Bregenz Bay showed an own aspect in its crustacean community with high total numbers and in earlier spring development. Most of the newcomers were concentrated in the eastern part of the lake.     

Towards the detection and attribution of an anthropogenic effect on climate

It has been hypothesized recently that regional-scale cooling caused by anthropogenic sulfate aerosols may be partially obscuring a warming signal associated with changes in greenhouse gas concentrations. Here we use results from model experiments in which sulfate and carbon dioxide have been varied individually and in combination in order to test this hypothesis. We use centered [R (t)] and uncentered [C (t)] pattern similarity statistics to compare observed time-evolving surface temperature change patterns with the model-predicted equilibrium signal patterns. We show that in most cases, the C (t) statistic reduces to a measure of observed global-mean temperature changes, and is of limited use in attributing observed climate changes to a specific causal mechanism. We therefore focus on R (t), which is a more useful statistic for discriminating between forcing mechanisms with different pattern signatures but similar rates of global mean change. Our results indicate that over the last 50 years, the summer (JJA) and fall (SON) observed patterns of near-surface temperature change show increasing similarity to the model-simulated response to combined sulfate aerosol/CO₂ forcing. At least some of this increasing spatial congruence occurs in areas where the real world has cooled. To assess the significance of the most recent trends in R (t) and C (t), we use data from multi-century control integrations performed with two different coupled atmosphere-ocean models, which provide information on the statistical behavior of 'unforced' trends in the pattern correlation statistics. For the combined sulfate aerosol/CO₂ experiment, the 50-year R (t) trends for the JJA and SON signals are highly significant. Results are robust in that they do not depend on the choice of control run used to estimate natural variability noise properties. The R (t) trends for the CO₂-only signal are not significant in any season. C (t) trends for signals from both the CO₂-only and combined forcing experiments are highly significant in all seasons and for all trend lengths (except for trends over the last 10 years), indicating large global-mean changes relative to the two natural variability estimates used here. The caveats regarding the signals and natural variability noise which form the basis of this study are numerous. Nevertheless, we have provided first evidence that both the largest-scale (global-mean) and smaller-scale (spatial anomalies about the global mean) components of a combined CO₂/anthropogenic sulfate aerosol signal are identifiable in the observed near-surface air temperature data. If the coupled-model noise estimates used here are realistic, we can be highly confident that the anthropogenic signal that we have identified is distinctly different from internally generated natural variability noise. The fact that we have been able to detect the detailed spatial signature in response to combined CO₂ and sulfate aerosol forcing, but not in response to CO₂ forcing alone, suggests that some of the regional-scale background noise (against which we were trying to detect a CO₂-only signal) is in fact part of the signal of a sulfate aerosol effect on climate. The large effect of sulfate aerosols found in this study demonstrates the importance of their inclusion in experiments designed to simulate past and future climate change. Received: 10 November 1994 / Accepted: 19 July 1995     

Stockwerktektonische Untersuchungen im Ruhrkarbon

Zusammenfassung Nach einer Erläuterung des Begriffes Stockwerktektonik wird über derartige Untersuchungen im südlichen Ruhrkarbon berichtet. Hier lassen sich drei durch fließende Übergänge verbundene tektonische Stockwerke unterscheiden: Das Flözleere ist durch das Vorherrschen tektonischer Formen niederer Größenordnung gekennzeichnet, die sich an bestimmten Stellen summieren. Das nächst höhere Stockwerk zeichnet sich durch eine sanfte Faltung und einige typische Faltenformen aus. Ein weiteres Stockwerk ist in seinem Formenschatz stärker differenziert. Über höhere Stockwerke liegen Untersuchungen vonKukuk, Kienow undSeidel vor. - Der vorliegende Bericht bringt nur Ergebnisse aus dem südlichen Revier; eine Gesamtdarstellung kann damit noch nicht gegeben werden.     

Computation of 5-day temperature normals in western Europe and the Mediterranean area

Summary UsingCraddock's method of representing the annual temperature variation by a two-term harmonic form fitted to monthly means, the harmonic coefficients of 63 stations in western Europe and around the Mediterranean Sea, as well as the 5-day normals for 24 Mediterranean stations, were computed and tabulated. In addition, some of the harmonic coefficients were charted and isoplethed, showing very distinctly the influence of continentality and topography. These charts, together withCraddock's charts for northern and northwestern Europe, provide fairly complete coverage of Europe and the Mediterranean area.This paper was prepared in the offices of the Technical Support Division of the 2d Weather Wing, United States Air Force, as a matter of routine business. The information contained herein was presented at the 5th Meeting of the Italian Society of Geophysics and Meteorology by Dr.Ingrid Weiss (Genoa: 23–25 April 1957). Since the paper is of general interest to all meteorologists of the Mediterranean area, it is published here with the permission of the originating agency as «Mémoire No. 3 du Centre International de Recherches sur la Météorologie de la Méditerranée (CIRMM)».     

Metallogenic provinces in South America

This paper discusses the broadscale distribution of some ore deposit types in South America, trying to discern possible relations with major geotectonic features. It does not cover all ore deposits but rather a selection based on available information, genetic types, geographic distribution, and a representation of deposit types which are either abundant or very rare in South America. Included are porphyry copper, zoned copper-zinc-lead-silver, contact-metasomatic, red-bed copper-uranium-vanadium, lead-zinc (including Mississippi Valley type), mercury, tin, pegmatite, carbonatite and alkalic complex, diamond, nickelcobalt-chromite-asbestos-talc, iron, bauxite, tungsten, titanium, uranium, gold, potash and phosphate deposits. Comparisons are made with the distribution of these deposit types in other continents, especially in North America and Africa. This leads to some speculations bearing on theories of ore genesis. The evidence suggests that upper crustal processes predominate in the formation of the majority of ore deposits considered (excepting carbonatites, alkalic complexes and diamond pipes). Also, the relative level of an orogenic belt exposed by erosion seems to be an important factor bearing on the presently known distribution of many ore deposit types. Furthermore, the fact that ore deposits of given types tend to be aligned along the Cordillera in more or less defined belts with changing chemical composition accross the Andes, which partake in all its inflections, and in patterns which are similar in North and South America, indicates that they are either dependent on the distribution of eugeosynclinal vs miogeosynclinal sediments in the original geosynclinal prism, or that their character is related to distance from the major batholitic masses or to shallow stocks and volcanic activity. The indicated correlation with sediment character and evaporites speaks in favor of modem concepts viewing hydrothermal fluids as mainly meteoric but heated and circulated largely by igneous activity. This study raises more questions than it can answer and calls attention to a number of problems requiring further research. From a practical point of view, this investigation reveals several possibilities for future exploration, as well as opportunities for further development of mineral resources in South America. Several countries could probably improve or diversify their mineral production significantly, thus raising the standard of living of their increasing population. Whereas in North America both Canada and the U.S.A. span from east to west the whole range of geological environments, from cratonic to geosynclinal and orogenic, in South America the distribución of countries is essentially either along the Cordillera or over shield areas, a fact of obvious geopolitical implications with regard to mineral resources.     

Petrographische Untersuchungen des Suevit aus den Bohrungen Deiningen und Wörnitzostheim im Ries von Nördlingen

Zusammenfassung In den Bohrungen Deiningen (D.) und Wörnitzostheim (W.) im Nördlinger Ries wurde unter tertiären Seesedimenten eine 40 m bzw. 70 m mächtige Suevitabfolge aufgeschlossen. Diese Breccie, bestehend aus zertrümmertem kristallinem Grundgebirge mit verschiedenen Anzeichen einer Stoßwellenmetamorphose und aus Glasbomben, wurde mineralogisch und petrographisch untersucht.Korngrößenanalysen zeigen in beiden Profilen eine allmähliche Zunahme des Mediandurchmessers von oben nach unten (D.: 0,1···0,4 mm; W.: 1···6 mm). Die Kornverteilungskurve von W. ist bimodal; das Hauptmaximum wird überwiegend aus grobkörnigen Gesteinsgläsern gebildet, ein kleineres Maximum liegt bei 0,2–0,6 mm und enthält bevorzugt Grundgebirgseinschlüsse.Das Verhältnis von Gesteinsgläsern: Kristallinkomponenten beträgt in D. etwa 30 70, in W. 60 40. Der Suevit von W. enthält durchschnittlich 28% Porenraum und 1–2% Neubildungen; seine Glassubstanz ist überwiegend frisch. Im Suevit von D. sind die Gläser sekundär zersetzt und bedingen höhere Porenvolumina (34–36%) und eine stärkere Verwitterungsneubildung (6–10%; Montmorillonit, Montmorillonit-Illit-Wechsellagerung, Karbonate und Analcim).Einzelminerale in der Kornfraktion 0,063–0,125 mm verteilen sich bei den Leicht-mineralen (d<2,96 g/cm³; Neubildungen nicht berücksichtigt) auf Feldspäte (D.: 56%; W.: 44%), Quarz (D.: 32%; W.: 28%), Biotit (D.: 5%; W.: <1%), Hornblende (D.: 2%; W.: -) und Gläser (D.: 3%; W.: 27%); der Anteil der Schwerminerale beträgt in D. 3–4% (Biotit, Opakes — Hornblende, Granat, Turmalin), in W. 0,5–0,8% (Opakes, Zirkon — Biotit, Rutil).Die chemische Zusammensetzung der Suevit- und Glasproben von W. ist dem granodioritischen Magmentyp ähnlich; die Suevitproben von D. weisen höhere Alkaligehalte auf.

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Underlying miocene lake sediments, suevite was found in the drill holes of Deiningen (D.) and Wörnitzostheim (W.), 40 meters and 70 meters thick, respectively. This breccia, containing glass and shattered crystalline rocks, in different stages of shock metamorphism, was examined by mineralogical and petrographical methods.In the two suevite profiles medians of grain size distributions gradually increase from top to bottom (D.: 0,1···0,4 mm; W.: 1···6 mm). The grain size distributions of W. are bimodal; the first maximum is mainly formed by coarse grained glass, the second (smaller) maximum (0,2···0,6 mm) contains crystalline components. The ratio of melted rocks: crystalline components is 3070 at D. and 6040 at W. Suevite from the latter locality has a total porosity of 28% (average) and contains 1–2% autigenic minerals; the glasses are mostly fresh. In the D. suevite decomposition of the glass has produced higher porosities (34–36%) and more autigenic minerals (6–10%: montmorillonite, mixed-layer minerals montmorillonite-illite, carbonates, analcime).Mineral composition was determined for the grain sizes from 0,063 to 0,125 mm. The light minerals (d<2,96 g/cm³, without autigenic minerals) comprise: feldspars (D.: 56%; W.: 44%), quartz (D.: 32%; W.: 28%), biotite (D.: 5%; W.: < 1%), hornblende (D.: 2%; W.: -) and glass (D.: 3%; W.: 27%); heavy-mineral content is 3–4% at D. (biotite, opaque minerals — hornblende, garnet, tourmaline) and 0,5–0,8% at W. (opaque minerals, zircon — biotite, rutile).The chemical composition of suevite and glass samples from W. is similar to granodiorite type rock. The suevite of D. contains more potassium and sodium.

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Meinem verehrten Lehrer, Herrn Prof. Dr. W. v. Engelhardt, danke ich für die Überlassung des Themas und alle Förderung meiner Arbeit. Für fördernden Rat danke ich ferner den Herren Dr. F. Lippmann und Dr. D. Stöffler.

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Der Deutschen Erdöl AG, insbesondere Herrn Prof. Dr. F. Hecht, danke ich für die Überlassung der Bohrkerne von Deiningen.

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Der Deutschen Forschungsgemeinschaft danke ich für die finanzielle Unterstützung dieser Arbeit.