Labrador Sea convection and subpolar North Atlantic Deep Water export in the SODA assimilation model

Labrador Sea convection was most intense and reached the greatest depths in the early 1990s, followed by weaker, shallower, and more variable convection after 1995. The Simple Ocean Data Assimilation (SODA) version 2.0.2/2.0.4 assimilation model is used to explore convective activity in the North Atlantic Ocean for the period from 1992 to 2007. Hydrographic conditions, which are relatively well observed during this period, are used to compare modeled and observed winter mixed-layer depths and water mass anomalies in relation to Deep Western Boundary Current transports and meridional overturning circulation (MOC) changes at the exit of the subpolar basin. The assimilation differs markedly from local observations in the March mixed-layer depth, which represents deep convection and water mass transformation. However, mean MOC rates at the exit of the subpolar gyre, forced by stratification in the mid-latitudes, are similar to estimates based on observations and show no significant decrease during the 1992–2007 period. SODA reproduces the deep Labrador Sea Water formation in the western North Atlantic without any clear indication of significant formation in the Irminger Sea while the lighter upper Labrador Sea Water density range is reached in the Irminger Sea in the 1990s, in agreement with existing assumptions of deep convection in the Irminger Sea and also supported by computed lag correlations with the Labrador Sea. Deep Water transformation mainly takes place in the eastern North Atlantic. The introduction of CFC-11 into the SODA model as a tracer reproduces the mean and multiyear variations of observed distributions.     

Using neutrino diffraction to study the Earth's core

A Dominic Fortes, Ian G Wood and Lothar Oberauer think through the possibilities for an entirely new – and currently technologically impossible – means of examining the core of the Earth.     

Über Flechtenalgen

Zusammenfassung Die grosse Formenfülle der Flechtenalgen l?sst sich durch einige neue F?lle belegen: inBiatorella pruinosa trittMyrmecia Biatorellae auf, die bisher nur aus verh?ltnism?ssig wenigen Flechten bekannt ist; eineVerrucaria sp. enth?lt eine noch unbeschriebene Protococcale, deren Chromatophor eine eigentümliche Zwischenstellung zwischen zentraler und parietaler Lage zeigt und in dieser Hinsicht der GattungJaagia ?hnelt;Verrucaria acrotella undacrotella f.subathallina sowie zweiThelidium-Arten enthalten einen schon von anderen Flechten mehrfach bekannten oder ihm sehr ?hnlichen Protococcus.     

Supernova bounds on neutrino radiative decays

The Solar Maximum Mission satellite did not record any γ-ray counts in excess of the background for a time interval of 223 s after the arrival of the first _e's from the supernova 1987A. On the basis of the original data we derive a new 3σ upper limit on the γ fluence for this period and derive improved bounds on the ν_i → ν_jγ and ν_T → ν_ee⁻e⁺γ radiative decay channels for neutrino masses up to the experimentally allowed value of around 30 MeV.     

Methods for determining the in situ hydraulic conductivity of shallow aquitards – an overview

Shallow clay-rich aquitards limit groundwater recharge to underlying aquifers, but they also protect the aquifers from contamination. The bulk hydraulic conductivity of such shallow aquitards can range from less than 1 mm/year to more than 100 m/year and may be much greater than the hydraulic conductivity of small intact samples of the aquitard material. This enhanced hydraulic conductivity diminishes the qualities of the aquitards for the protection of underlying aquifers but allows a higher rate of recharge. For aquifers that are overlain by aquitards, management and protection of groundwater resources may be critically dependent on reliable determinations of aquitard permeability. A variety of methods for determining bulk hydraulic conductivities of shallow clay aquitards is available; each has drawbacks and advantages, and each is based on simplifying assumptions. These methods include slug tests, pumping tests, response of the aquitard to mechanical loading, and analysis of natural pore-pressure fluctuations. Several of the commonly used methods require an independent measurement of specific storage. Laboratory methods for determining specific storage are probably not representative of in situ conditions and may lead to overestimation of aquitard permeability. Much of the theory developed to date depends on the assumption that horizontal displacement of the solid material is negligible, and this may not be a valid assumption for highly deformable media such as clay aquitards. However, with judicious selection of the most suitable methods for a particular site, good test design, careful instrumentation, and respect for the underlying assumptions, reliable determinations of aquitard permeability can be obtained. Electronic Publication     

Die Kieselschiefer des Frankenwaldes

Zusammenfassung Das räumlich stark gegliederte Gebiet der bayerischen Entwicklung des Frankenwaldes war für den Absatz mächtigerer Kieselschieferkomplexe besonders geeignet. Die Unterschiede zwischen den gotlandischen und devonischen Kieselschiefern beruhen auf verschiedenen Sedimentationsbedingungen. Ein Teil dieser Gesteine ist aus Konkretionen hervorgegangen. Die Beziehungen zwischen der Kieselschieferbildung und dem Vulkanismus werden besonders deutlich und erklären regionale Besonderheiten. Organogen entstandene Kieselschiefer geben sich durch die Art der Lagerung zu erkennen.Vorgetragen im März 1957 auf der Tagung der Geologischen Vereinigung in Wiesbaden.     

Modellseismische Untersuchungen an 2- und 3-dimensionalen Testmodellen,Teil 1

Summary Following the recommendation of the European Seismological Commission (Copenhagen 1966) to carry out comparative measurements on simple seismic models with a prescribed velocity-depth distribution (test models), an attempt was made to compare results obtained with different model techniques. In the present paper, model investigations with the first two proposed test models carried out by 2- and 3-dimensional model techniques are described. Seismogrammes, travel-time curves and amplitude-distance curves of the models investigated are given. A quantitative comparison of the results shows a satisfactory agreement.     

Schubrichtungen im präkambrischen Unter- und Oberbau des Brasilischen Schildes

Zusammenfassung Arbeiten im Bereich der hochkristallinen präkambrischen Caraiba-Serie nordwestlich von Uauá/Nordost-Bahia/Brasilien erlauben es, Schlüsse zu ziehen, die auf einen großen Teil des Brasilischen Schildes zu übertragen sind.Es werden zwei vorassyntische Scherflächenscharen unterschieden, die in allen Maßstäben ausgebildet sind, und zwar eine rechtssinnig verschiebende mit Richtungen um NNE und eine linkssinnig verschiebende um WNW. Sie zeigen einen Schub ENE-WSW an, der in Wahrheit N-S gerichtet war, wenn man die Drehung des brasilischen Blockes gegenüber Afrika berücksichtigt. Zu den rechtssinnigen Flächen gehört das alte Nordost-Bahia-Lineament. Aus dem Schub bei der jüngeren, unstetigen Verformung im Oberbau kann auf den Schub bei der älteren, stetigen Verformung im Unterbau geschlossen werden, denn der Gneisbau bildet die gleichen Richtungen aus wie die aus ihm hervorgehenden (sub)konkordanten Verwerfungen. Die vorassyntischen Grundgebirgsgneise wurden also durch den gleichen Schub wie die Verwerfungen geformt. Nach Eintritt des Grundgebirges in den Oberbau infolge von Abtragung und Isostasie stellten sich die Scherflächen spitzwinklig zum herrschenden Schub ein. Aus einigen Umständen wird der Schluß gezogen, daß das Scherflächenpaar die Form der Ceará-, Sergipe- und Paraíba-Geosynkline und vielleicht noch weiterer Tröge vorzeichnete und ihre Füllmassen prägte.In der assyntischen Phase wurde die brasilische Masse einem um 90° veränderten Schub unterworfen. Nun bildeten sich rechtssinnige Scherbahnen um Ost-West und linkssinnige Bahnen um NE. Sie finden ihren stärksten Ausdruck in den jungen Lineamenten: Pernambuco-, Paraiba-Lineament mit rechtssinnigem, Pedro-SegundoSobral-Lineament u. a. mit linkssinnigem Versatz.Die Arbeitsergebnisse geben einen weiteren Beweis dafür, daß die Erdkruste in hohem Maße durch zweischarige Scherung gestaltet worden ist.Die Ausrichtung der präkambrischen Gefüge vereinbart sich mit einer Drehung des brasilischen Blocks von 45° im Uhrzeigersinne gegenüber dem afrikanischen Block. Die Drehung zu den Längenkreisen betrug wahrscheinlich um 55°.

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Geologic work in the region of the highly crystalline Precambrian Caraíba complex in the NW of Uauá, Northeastern Bahia, Brazil, permits to draw conclusions which are applicable to a large part of the Brazilian Shield.The author distinguishes two pre-Assyntian systems of shear-planes which were formed in all scales. There is one system striking about NNE with right-lateral sense of movement, and one striking about WNW with left-lateral sense of movement. The shear-planes indicate ENE-WSW directed stress. Taking into consideration the rotation of the Brazilian block (continental drift) the original direction of stress must have been N-S. The old Northeast Bahia Lineament is part of the right-lateral shear-planes. The stress of the older differential deformation of the lower crust can be inferred from the stress of the younger, faulting deformation in the upper crust, since the basement shows the same direction as those (sub)concordant faults developing from basement structures. Therefore the pre-Assyntian gneisses are assumed to be formed by the same stress as the faults. After the basement, as a result of erosion and isostasy, reached supracrustal position, the acute angle formed by the shear-planes opened toward the existing stress. Evidence suggests that the shear-planes determined the shape of the younger Precambrian geosynclines and affected their fillings.During the Assyntian phase, the Brazilian block was subjected to a stress differing from the former one by about 90°. Right-lateral shear-planes striking roughly E-W and left-lateral planes striking about NE were formed. Their most pronounced representatives are the young lineaments: Pernambuco, Paraíba Lineament with rightlateral dislocation, Pedro-Segundo-Sobral Lineament ect. with left-lateral dislocation.The results of this investigation prove once more the crust of the earth to be formed and deformed in a high degree by conjugate shearing.The directions of the Precambrian structures are compatible with a clockwise rotation of the Brazilian block of 45° in comparison with the African block. The rotation with respect to the meridians probably amounted to about 55°.

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Resumo Trabalhos na região do grupo Caraíba no embasamento cristalino NW de Uauá, Nordeste de Bahia, Brasil, permitem deduzir conclusões, as quais podem ser transferidas a uma grande parte do escudo brasileiro.Distinguem-se dois sistemas pre-assinticos de pianos de cizalhamento, que se formaram em todas escalas: uma de um rejeito dextrogiro aproximadamente na direção de NNE e uma de um rejeito levogiro mais ou menos na direção de WNW. Indicam uma pressão ENE-WNW que era dirigida de N-S, por que a rotação do bloco brasileiro deve ser considerada em relação com o bloco africano. O lineamento antigo do nordeste de Bahia pertence aos pianos dextrogiros. Da pressão na deformação mais jovem pode-se deduzir a pressão da deformação mais velha do embasamento, pois as estruturas dos gnaisses formam as mesmas direções que as falhas (sub)concordantes. Os gnaisses do embasamento pre-assintico foram formados pela mesma pressão que as falhas. Depois da entrada do embasamento na crusta superior — devido a erosão profunda e isostasía — os planos de cizalhamento se arranjaram em angulo agudo à direção da pressão. De algumas circumstâncias pode-sa deduzir a conclusão, que o par de cizalhamentos desenhou a forma das geossinclinais de Ceará, Sergipe e Paraíba, e, talvez, a de algumas bacias mais, e formou as suas massas, preenchendas.Na fase assintica, o bloco brasileiro foi submetido a uma pressão variada de 90°. Formaram-se planos de NE e E-W. Encontram a sua expressão mais forte nos lineamentos mais recentes de Pernambuco e Paraíba, con rejeito dextrogiro, e de Pedro Segundo-Sobral e outros, com rejeito levogiro.Os resultados do trabalho provam mais uma vez que a crusta da Terra é formada numa parte principal por planos de cizalhamento.As direções das estruturas pré-cambrianas são compatíveis com uma rotação do bloco brasileiro de 45° no sentido do ponteiro, em relação com o bloco africano. A rotação, relativamente aos meridianos, importa, provàvelmente, em 55°.

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