Precise two chronometer dating of Pleistocene travertine: The Th/U and Raex/Ra(0) approach

In order to determine the geochemical evolution of a freshwater limestone cave system located in central Switzerland (Hell Grottoes at Baar/Zug,) young postglacial tufaceous limestone and travertine precipitates were investigated using the ²³⁰Th/²³⁴U ingrowth system. Additional analyses of further radionuclides within the ²³⁸U decay chain, i.e. ²²⁶Ra and ²¹⁰Pb, showed that the Th/U chronometer started with insignificant inherited ²³⁰Th over the entire formation period of the travertine setting (i.e. ²³⁰Th(0)=0). A contribution from detrital impurities with ²³⁰Th/²³⁴U in secular equilibrium could be precisely subtracted by applying isochron dating of cogenetic phases and recently formed travertine. The resulting precise ²³⁰Th/²³⁴U formation ages were found to be consistent with the geological stratigraphy and were furthermore used to demonstrate the applicability of the next geologically important chronometer in the ²³⁸U-decay series, based on decay of excess ²²⁶Ra normalized to the initial, i.e.²²⁶Ra_ex/²²⁶Ra(0). This system is suitable for dating phases younger than 7000 yr when the correction of a detritus component increasingly limits the precision of the ²³⁰Th/²³⁴U chronometer. Analytical solutions of the coupled ²³⁴U/²³⁰Th/²²⁶Ra radionuclide system predicted that the ²²⁶Ra_ex/²²⁶Ra(0) chronometer is independent of the actual ²³⁰Th activity build up from decay of ²³⁴U, if the systems starts with zero inherited ²³⁰Th(0). The data set confirmed this hypothesis and showed furthermore that the initially incorporated ²²⁶Ra excess must have remained almost uniform in all limestone over a period of at least 7000 yr, i.e. 4–5 half-lives of ²²⁶Ra. This is concluded because (i) the ²²⁶Ra_ex/²²⁶Ra(0) ages agreed well with those derived from ²³⁰Th/²³⁴U, (ii) all data plot within uncertainty on the ²²⁶Ra_ex/²²⁶Ra(0) decay curve and (iii) the atomic Ba/Ca ratio was found to be constant in the travertine material independent of the sample ages. Provided that such boundary conditions hold, ²²⁶Ra_ex/²²⁶Ra(0) should be applicable to materials which are suitable for ²³⁰Th/²³⁴U dating in sedimentology and oceanography, i.e. travertine, corals, phosphorites, etc., and should strongly support ²³⁰Th/²³⁴U for samples that have been formed a few thousand years ago.     

Geological control of shallow gas and pockmarks in the Norwegian Channel; high resolution shallow subbottom profiling of small scale features

High resolution bathymetric and fine-scale parametric subbottom profiling along a line to the SW of Stavanger, Norway near the NE flank of the Norwegian Channel, show pockmarks clustered over neotectonic shallow fold structures in Quaternary sediments. Detailed profiles of the pockmarks indicate that they are collapsed gas seeps, rather than being collapse structures that followed doming and breaching with a more dramatic gas burst. The gentle folding and weak structures along the margin of a Mesozoic through Cenozoic sedimentary basin are probably due to differential uplift generating light compressional strain.     

Supply regimes in fisheries

Supply in fisheries is traditionally known for its backward bending nature, owing to externalities in production. Such a supply regime, however, exist only for pure open access fisheries. Since most fisheries worldwide are neither pure open access, nor optimally managed, rather between the extremes, the traditional understanding of supply regimes in fisheries needs modification. This paper identifies through a case study of the East Baltic cod fishery supply regimes in fisheries, taking alternative fisheries management schemes and mesh size limitations into account. An age-structured Beverton–Holt based bio-economic supply model with mesh sizes is developed. It is found that in the presence of realistic management schemes, the supply curves are close to vertical in the relevant range. Also, the supply curve under open access with mesh size limitations is almost vertical in the relevant range, owing to constant recruitment. The implications are that the effects on supply following from e.g. trade liberalisation and reductions of subsidies are small in several and probably most fisheries worldwide.     

Uptake and release of 51Cr(VI) and 51cr(III) by Barnacles (Balanus sp)

Barnacles (Balanus sp) were used to examine the uptake and release of chromium-51 added to sea water in two different valence states, ⁵¹Cr(VI) and ⁵¹Cr(III).Hexavalent chromium-51 (sodium chromate) forms a true ionic solution in filtered sea water and barnacles were able to accumulate chronium in soft tissues 543 times the levels found in sea water. The experiment showed that incorporated Cr(VI), is released to the water in such way that only 20%% of maximum uptake was lost by the organisms after 26 days. Addition of the hexavalent form to non filtered sea water showed that 2% of the total radioactivity was attached to the suspended particles. Here again chromium is mainly concentrated in soft tissues, showing a concentration factor of 380 related to total chromium available in aquarium (solution + suspended particles). From the total radioactivity incorporated by the organisms, 20 % was released after 56 days in the clearance experiment.Chromium, as trivalent chromic chloride, when added to sea water precipitates and is quickly removed from the water by the filter activity of the barnacles. Unlike the hexavalent form, trivalent chromium is not concentrated in soft tissues of the barnacles and is quickly released to the water through the organisms digestive system.     

Das Problem des alpinen Wildflysch

Ohne Zusammenfassung     

Die neue Periode des Vesuvs

Ohne Zusammenfassung     

Das Erdöl in Südbayern,geologische Stellung und Aussichten

Ohne Zusammenfassung     

Ein Präzisionszeitskalenschreiber mit Dekadischer Frequenz-Unterteilung für Zeitmarkierung und Frequenzmessung

Zusammenfassung Es wird ein Präzisionszeitskalenschreiber mit fünffacherdekadischer Frequenzunterteilung für Zeitmarkierung und Frequenzmessung beschrieben, der aus RC-Schwingungskreisen mit Gasentladungsröhren besteht, in deren Entladungskreis sich eine Registrierschleife befindet. Der erste Kreis wird nach einem Uhrenprinzip durch eine Stimmgabel synchronisiert, wobei zwecks Erhöhung der Genauigkeit der Antrieb stets im Nulldurchgang erfolgt. Die Synchronisierung der weiteren Kreise erfolgt in der Weise, dass man dem Gitter des Kippschwingungskreises Spannungsstösse des davor liegenden Kippschwingungskreises überlagert, und zwar derart, dass die Zündung bei jedem zehnten überlagernden Stoss erfolgt. Die freien Kippschwingungen werden dabei zu erzwungenen zwangläufig synchronisierten Schwingungen. Die Frequenzunterteilung erfolgt in fünf Dekaden (1000, 100, 10, 1 und 0.1 Hertz).

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Summary A new time marking arrangement is described, developped by the Author, based on the application of thyratrons, synchronized by means of a tuning fork, and recording automatically a scale, which is subdivided in 5 decades and which works with extremely high exactness. The arrangement is synchronized by means of a clock principle.

     

Die Interpretation von seismischen Refraktionsmessungen im Grenzfallc 0=0

Zusammenfassung Es wird im Anschluss an «Die Laufzeifunktion und ihre Interpretation in der Refraktionsseismik des einachsig inhomogenen Körpers» (4) die Interpretation von seismischen Refraktionsmessungen im Grenzfallc _o=0 eingehend behandelt.

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Summary In pursuance of «Die Laufzeifunktion und ihre Interpretation in der Refraktionsseismik des einachsig inhomogenen Körpers» (4) the special interpretation problem withc _o=0 is generally treated.