Neue Beobachtungen zur Paläogeographie des Devon auf dem brasilianischen Block

Zusammenfassung Neuere Beobachtungen im Jatobá-Becken (Pernambuco — Brasilien), dem nördlichsten Ausläufer der Reconcavo-Zone von Bahia haben überraschenderweise dort eine Vertretung von Unterdevon und unterstem Unterkarbon ergeben. Das Cariri-Konglomerat im Liegenden der kretacischen Araripe-Serie (West-Pernambuco) muß nach neuen Beobachtungen ebenfalls ins Unterdevon eingereiht werden. Gleiches gilt für den stratigraphisch bisher in der Luft hängenden Tombador-Sandstein im zentralen Bahia, dessen Profil weitgehend dem Unterdevon-Profil von Piaui entspricht. Die Devondecke auf dem nordöstlichen Teil des brasilianischen Blockes war ursprünglich viel ausgedehnter als bisher vermutet werden konnte. Eigenartig ist die auf die weiten Entfernungen gleichförmige grobklastische Fazies auch in offensichtlich küstenferneren Bereichen, die kaum eine andere Deutung als driftglaziale Einflüsse im Unterdevon-Meer zuläßt, was früher auch schonMaack für das Unterdevon in Paraná vermutet hatte. Die aus paläomagnetischen Messungen erschlossene Lage des brasilianischen Blockes während des Devon stimmt damit gut überein.

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Recent observations in the basin of Jatobá (Pernambuco — Brasil), the extreme northern end of the Reconcavo-Zone of Bahia, resulted in the surprising discovery of Subdevonian and lowest Carboniferous. Recent studies also found out that the Cariri-conglomerat in the underlying bed of the cretaceous Araripe-series (West-Pernambuco) must also be classified in the Subdevonian, as well as the Tombador sandstone in central Bahia, whose profil resembles that of the Subdevonian of Piaui. The Devonian nappe on the north-eastern part of the Brasilian block was originally much larger than it has been assumed. The clastic facies even in regions far from the coast, is very strange. It can only be interpreted as glacial deposits in the subdevonian ocean, a suggestion which has already been made byMaack for the Subdevonian in Paraná. This agrees with the situation of the Brasilian block during the Devonian, infered from paleomagnetic measurements.

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Resumen Conforme as observações mais recentes há uma representação do Devoniano inferior e do Carbonífere mais inferior na bacia de Jatobá (Pernambuco — Brasil), a extremidade setentrional da zone de Revoncavo. O conglomerado de Cariri na lapa da série Araripe, deve ser atribuido ao Devoniano inferior conforme observações recentes. O arenito Tombador da Bahia, cujo perfil corresponde muito bem ao do Devoniano inferior de Piaui, tern a mesma posição estratigráfica. No bloco brasileiro, a capa, devoniana era originalmente muito mais extensa do que se supôs até agora. A fácies clástica, muito monótona por todas estas amplas áreas, é um fenomeno muito estranho que pode ser interpretado só pela idéia que no mar devoniano houve gelo flutuante. No Devoniano do Paraná, R.Maack pronunciou a mesma idéia. As medições paleomagnéticas indicam uma posição do bloco brasileiro durante o Devoniano, que bem corresponde a esta interpretação.

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Platform-induced clay-mineral fractionation along a northern Tethyan basin-platform transect: implications for the interpretation of Early Cretaceous climate change (Late Hauterivian-Early Aptian)

High-resolution clay-mineral analyses were performed on upper Hauterivian to lower Aptian sediments along a platform-to-basin transect through the northern Tethyan margin from the Neuchâtel area (Switzerland), to the Vocontian Trough (France) in order to investigate links between climate change, carbonate platform evolution, and fractionation patterns in clay minerals during their transport.During the Hauterivian, the northern Tethyan carbonate platform developed in a heterozoan mode, and the associated ramp-like topography facilitated the export of detrital material into the adjacent basin, where clay-mineral assemblages are dominated by smectite and kaolinite is almost absent, thereby suggesting dry-seasonal conditions. During the Late Hauterivian Balearites balearis ammonite zone, a change to a more humid climate is documented by the appearance of kaolinite, which reaches up to 30% of the clay fraction in sediments in the Vocontian Trough. This prominent change just preceded the Faraoni Oceanic Anoxic Event and the onset of the demise of the Helvetic Carbonate Platform, which lasted to the late early Barremian.From the Late Barremian onwards, the renewed growth of the northern Tethyan carbonate platform in a photozoan mode and the associated development of a marginally confined platform topography fractionated the clay-mineral assemblages exported into hemipelagic settings: kaolinite particles were preferentially retained in proximal, platform settings, due to their size and their relatively high specific weight. In the inner platform environment preserved in the Swiss Jura, an average of 32% of kaolinite in the clay fraction is observed during the latest Barremian–earliest Aptian, whereas clay-mineral assemblages of coeval sediments from deeper depositional settings are dominated by smectite and show only minor amounts of kaolinite.This signifies that besides palaeoclimate conditions, the morphology and ecology of the carbonate platform had a significant effect on the distribution and composition of clay assemblages during the Late Hauterivian–Early Aptian along the northern Tethyan margin.     

Adriatic coast as a microcosm for global genotoxic marine contamination--a long-term field study

Global changes in the marine environment and the continuing disposal of genotoxic xenobiotics are increasing the importance of environmental pollution monitoring and of biomonitoring programs. Current approaches focus on investigations at regional and local levels in an attempt to precisely define the nature and extent of any potential environmental crisis. We have initiated, for the first time, a long-term biomonitoring program focusing on the Croatian coast of the Adriatic Sea to contribute to a more detailed understanding of marine genotoxic effects using the mussels Mytilus galloprovincialis Lam., collected along the eastern Adriatic coast over a period of five years (1998-2002), as a key test organism. The integrity of DNA in its gill homogenate was examined by the Fast Micromethod. The strand scission factor (SSF) values, as a measure of DNA integrity, DNA damage or incomplete repair have been used for the ranking of sampling sites with respect to significant genotoxic stress due to the influence or effects of genotoxic xenobiotics. The region of Split (Kastela Bay) proved to be the area with the heaviest load of genotoxic agents. The investigation of harmful effects in the ecosystem based on biomonitoring of genetic and other agents, not only on local levels but also on a wider scale, is considered as an important step in marine environmental management.     

Kinetics of CO2 production on venus

Consideration of theoretical limits and experimental data for the kinetics of the reaction quartz + calcite → wollastonite + CO₂ supports the concept of a shortterm quasiequilibrium state for the atmosphere of Venus. These data indicate that the time scale of this reaction and of any competing CO₂ producing reaction may be as short as several hundred years or less at the inferred Venus surface temperatures.     

A Lagrangian Stochastic Model for Sea-Spray Evaporation in the Atmospheric Marine Boundary Layer

The dispersion of heavy particles subjected to a turbulent forcing is often simulated with Lagrangian stochastic models. Although these models have been employed successfully over land, the implementation of traditional LS models in the marine boundary layer is significantly more challenging. We present an adaptation of traditional Lagrangian stochastic models to the atmospheric marine boundary layer with a particular focus on the representation of the scalar turbulence for temperature and humidity. In this new model, the atmosphere can be stratified and the bottom boundary is represented by a realistic wavy surface that moves and deforms. Hence, the correlation function for the turbulent flow following a particle is extended to the inhomogenous, anisotropic case. The results reproduce behaviour for scalar Lagrangian turbulence in a stratified airflow that departs only slightly from the expected behaviour in isotropic turbulence. When solving for the surface temperature and the radius of evaporating heavy water droplets in the airflow, the modelled turbulent forcing on the particle also behaves remarkably well. We anticipate that this model will prove especially useful in the context of sea-spray dispersion and its associated sensible heat, latent heat, and gas fluxes between spray droplets and the atmosphere.     

Über Facies und Tektonik der Kreide im Westen der Pyrenäen

Zusammenfassung Zuerst wird eine gedrängte Übersicht über die Stratigraphie der basko-kantabrischen Kreidegeosynklinale und die Tektonik ihres baskischen, strukturell noch zu den Pyrenäen gehörigen Anteils gegeben. Dann werden gewisse, den klastischen Kreide-Schichtfolgen im allgemeinen fremde, sauber klassierte Grobpsammite und Geröllfacien als Spuren lokaler Ausgleichsströmungen an Untergrundsunebenheiten gedeutet. Diese ordnen sich, zusammen mit Mächtigkeitsminima insbesondere des Albien, und mit Diskordanzen in Albien und Cenoman auf Nordnordwest- bis Nord-streichenden Zonen an. Parallel dazu verlaufen Bruchstrukturen innerhalb der Kreide, die den Gang der posteozänen Pyrenäenfaltung örtlich beeinflußten und von dieser, so beherrschend und tiefgreifend sie hier im übrigen scheinen mag, nur unvollkommen überprägt wurden. Auf eine ältere Strukturierung des voralpidischen Untergrundes wird geschlossen. Tatsächlich ergab ein zu Vergleichszwecken angestelltes Literaturstudium in dem ostwärts anschließenden Gebiet der Westpyrenäen das Vorhandensein variscischer Achsen und Brüche gleicher Art und Orientierung.

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Stratigraphy and tectonics of the Basco-Cantabrian cretaceous geosyncline (Northern Spain) are briefly resumed. Lithofacial and structural peculiarities in it are described. They suggest meridional faulting of the basement, similarly as described by others in the older rocks exposed in the Western Pyrenees.

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Résumé Stratigraphie et tectonique du géosynclinal crétacé basco-cantabrique sont résumées brèvement. Des surélévements au fond de la mer aptienne-cénomanienne, conclus de certains faciès grossiers, d'épaisseurs-minimum et de discordances, s'élongeaient parallèles à des failles et des axes pré-pyrénéennes, disharmoniques, en direction Nord-nord-ouest ou Nord. Celles-ci ne sont retouchées qu'imparfaitement par le plissement post-éocène, entraînant et catégorique qu'il bien y paraisse. A l'Est de Tolosa, jusqu'à Pau, le sous-sol élevé du géosynclinal crétacé montre des axes et des failles méridionales, hercyniennes, tout-à-fait pareilles à celles qu'il me fallut admettre au-dessous du Crétacé basque pour y expliquer les particularités mentionnées ci-dessus.

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Erweitertes Manuskript eines Vortrages vor der Hauptversammlung der Geologischen Vereinigung in Wetzlar am 13. März 1961.     

Analysis of Signals from an Unique Ground-Truth Infrasound Source Observed at IMS Station IS26 in Southern Germany

Quantitative modeling of infrasound signals and development and verification of the corresponding atmospheric propagation models requires the use of well-calibrated sources. Numerous sources have been detected by the currently installed network of about 40 of the final 60 IMS infrasound stations. Besides non-nuclear explosions such as mining and quarry blasts and atmospheric phenomena like auroras, these sources include meteorites, volcanic eruptions and supersonic aircraft including re-entering spacecraft and rocket launches. All these sources of infrasound have one feature in common, in that their source parameters are not precisely known and the quantitative interpretation of the corresponding signals is therefore somewhat ambiguous. A source considered well-calibrated has been identified producing repeated infrasound signals at the IMS infrasound station IS26 in the Bavarian forest. The source results from propulsion tests of the ARIANE-5 rocket’s main engine at a testing facility near Heilbronn, southern Germany. The test facility is at a range of 320 km and a backazimuth of ~280° from IS26. Ground-truth information was obtained for nearly 100 tests conducted in a 5-year period. Review of the available data for IS26 revealed that at least 28 of these tests show signals above the background noise level. These signals are verified based on the consistency of various signal parameters, e.g., arrival times, durations, and estimates of propagation characteristics (backazimuth, apparent velocity). Signal levels observed are a factor of 2–8 above the noise and reach values of up to 250 mPa for peak amplitudes, and a factor of 2–3 less for RMS measurements. Furthermore, only tests conducted during the months from October to April produce observable signals, indicating a significant change in infrasound propagation conditions between summer and winter months.     

Isotopic geochemistry of Fernando de Noronha

Volcanic and hypabyssal rocks ranging in age from 12 to 3 Ma from the Fernando de Noronha archipelago in the western equatorial Atlantic Ocean can generally be divided into two age-compositional groups that have variable and distinct isotopic compositions. Predominantly older alkali basalts and trachytes are generally characterized by more radiogenic Sr-isotopic (⁸⁷Sr/⁸⁶Sr= 0.70457–0.70485) compositions and less radiogenic Nd-isotopic (¹⁴³/Nd¹⁴⁴Nd= 0.51271–0.51281) and Pb-isotopic (²⁰⁶Pb/²⁰⁴Pb= 19.132–19.282) compositions relative to the generally younger, more alkaline Si-undersaturated rocks which include nephelinites, ankaratrites, and melilitites (⁸⁷Sr/⁸⁶Sr= 0.70365–0.70418,¹⁴³Nd/¹⁴⁴Nd= 0.51277–0.51290,²⁰⁶Pb/²⁰⁴Pb= 19.317–19.565). These variations suggest the influence of at least two separate components in the source(s) of both series. One component is characterized by highRb/Sr and low μ, possibly derived from delaminated subcontinental lithosphere, whereas the other has high μ and lowRb/Sr similar to the source of St. Helena lavas. A third component is suggested by correlated compositions in the latest alkaline, Si-undersaturated lavas, and this component may be derived from depleted mantle. These isotopic variations in conjunction with the generally increasing degree of alkalinity with time are consistent with the temporal depletion of a low-μ, highRb/Sr component and increasing contributions from a high-μ component in the sources of the volanic rocks of Fernando de Noronha.     

Helmet Streamers with Triple Structures: Weakly Two-Dimensional Stationary States

Recent observations of the solar corona with the LASCO coronagraph on board the SOHO spacecraft have revealed the occurrence of triple helmet streamers even during solar minimum, which occasionally go unstable and give rise to particularly huge coronal mass ejections. We present a method to calculate (semi-)analytically self-consistent stationary configurations of triple helmet streamers which can serve as input for stability considerations and dynamical calculations. The method is based on an asymptotic expansion procedure using the elongated structure of the streamers. The method is very flexible and can be used in both Cartesian and spherical geometry. We discuss the effects of magnetic shear, gravity and field-aligned flow on open field lines. Example solutions illustrating the influence of each of these features on the solution structure are presented.