Talus Instability in a Recent Deglaciation Area and Its Relationship to Buried Ice and Snow Cover Evolution (Picacho Del Veleta, Sierra Nevada, Spain)     

Antonio Gómez  David Palacios  Enrique Luengo  Luis M. Tanarro  Lothar Schulte  Miguel Ramos 《Geografiska Annaler: Series A, Physical Geography》2003,85(2):165-182

The southernmost glacier in Europe formed during the Little Ice Age at the foot of the north wall of Picacho del Veleta (3 398 m) in Sierra Nevada, in the southeast region of the Iberian Peninsula (lat. 37δ03‘N, long. 3δ22‘W). The glacier gradually retreated during the last century, leaving a large talus slope at the base of the wall. The unconsolidated material covering the ice masses acted as a thermal insulator. Recent bottom temperature of snow (BTS) analyses and drillings indicate that the ice still exists within the talus. Evidence from field observations made during the period 1995–2001, revealed that large mass movements occurred during the driest summers (1998 and especially, 1999 and 2000) when the talus was snow free. These conditions suggest a direct relationship between talus stability and thermal insulation from the snow cover in areas where buried ice or decaying marginal permafrost exists.  相似文献   

Spatial distribution of sediment storage types and quantification of valley fill deposits in an alpine basin, Reintal, Bavarian Alps, Germany     

Lothar Schrott  Gabi Hufschmidt  Martin Hankammer  Thomas Hoffmann  Richard Dikau 《Geomorphology》2003,55(1-4):45

Spatial patterns of sediment storage types and associated volumes using a novel approach for quantifying valley fill deposits are presented for a small alpine catchment (17 km²) in the Bavarian Alps. The different sediment storage types were analysed with respect to geomorphic coupling and sediment flux activity. The most landforms in the valley in terms of surface area were found to be talus slopes (sheets and cones) followed by rockfall deposits and alluvial fans and plains. More than two-thirds of the talus slopes are relict landforms, completely decoupled from the geomorphic system. Notable sediment transport is limited to avalanche tracks, debris flows, and along floodplains. Sediment volumes were calculated using a combination of polynomial functions of cross sections, seismic refraction, and GIS modelling. A total of, 66 seismic refraction profiles were carried out throughout the valley for a more precise determination of sediment thicknesses and to check the bedrock data generated from geomorphometric analysis. We calculated the overall sediment volume of the valley fill deposits to be 0.07 km³. This corresponds to a mean sediment thickness of 23.3 m. The seismic refraction data showed that large floodplains and sedimentation areas, which have been developed through damming effects from large rockfalls, are in general characterised by shallow sediment thicknesses (<20 m). By contrast, the thickness of several talus slopes is more than twice as much. For some locations (e.g., narrow sections of valley), the polynomial-generated cross sections resulted in overestimations of up to one order of magnitude; whereas in sections with a moderate valley shape, the modelled cross sections are in good accordance with the obtained seismic data. For the quantification of valley fill deposits, a combined application of bedrock data derived from polynomials and geophysical prospecting is highly recommended.  相似文献   

Geochemistry and mineralogy of platinum-group elements at Hartley Platinum Mine,Zimbabwe     

Thomas?OberthürEmail author  Thorolf?W.?Weiser  Lothar?Gast  Kari?Kojonen 《Mineralium Deposita》2003,38(3):327-343

The behaviour of platinum-group elements (PGE) in the exogenic cycle was examined in profiles of oxidized Main Sulfide Zone (MSZ) ores, in which the general metal distribution patterns of the pristine MSZ are grossly preserved. However, at similar Pt grades, significant proportions of Pd have been lost from the system. This indicates that Pd is more mobile than Pt and is dispersed in the supergene environment. Sperrylite and cooperite/braggite are stable in the oxidized MSZ. In contrast, the (Pt,Pd)-bismuthotellurides, common in pristine MSZ ores, have disintegrated, and ill-defined (Pt,Pd)-oxides or (Pt,Pd)-hydroxides have formed. The assemblage of detrital PGM present in the Makwiro River close to the Hartley Platinum Mine indicates further mineralogical changes. Sperrylite largely remains stable whereas most cooperite/braggite grains have been partly altered or completely destroyed. Grains of Pt-Fe alloy are ubiquitous in the alluvial sediments. Most likely, these grains are neo-formations that formed either from pre-existing, unstable PGM or via a solution stage under low-temperature conditions.  相似文献   

Schubrichtungen im präkambrischen Unter- und Oberbau des Brasilischen Schildes     

Dr. Lothar Steiner 《International Journal of Earth Sciences》1972,61(1):140-165

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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- Uaua ( Bahia / ), , . , NNE WNW. ENE-WSW, N-S, . , - Bahia. , , , . . , / . , . , . , Ceara-, Sergipe — Paraiba, , . , 90°. : Pernambuco Paraiba , Pedro-Segundo-Sobral — . , . 45° . , , 55°.

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

Jörn Behrens  Lothar Dresen  Ludvík Waniek  Rezensent V. Červený 《Studia Geophysica et Geodaetica》1971,15(2):147-160

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.  相似文献   

Numerical investigations on the correction term for the free air anomalies according to the new theory of dynamical geodesy     

Kurt Arnold  Dietrich Schoeps  Lothar Stange 《Studia Geophysica et Geodaetica》1965,9(2):160-160

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Die Kieselschiefer des Frankenwaldes     

Lothar Greiling 《International Journal of Earth Sciences》1958,47(1):443-450

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.  相似文献   

Oxygen minimum zones in the eastern tropical Atlantic and Pacific oceans   总被引：2，自引：0，他引：2  

Johannes Karstensen  Lothar Stramma  Martin Visbeck 《Progress in Oceanography》2008,77(4):331-350

Within the eastern tropical oceans of the Atlantic and Pacific basin vast oxygen minimum zones (OMZ) exist in the depth range between 100 and 900 m. Minimum oxygen values are reached at 300–500 m depth which in the eastern Pacific become suboxic (dissolved oxygen content <4.5 μmol kg⁻¹) with dissolved oxygen concentration of less than 1 μmol kg⁻¹. The OMZ of the eastern Atlantic is not suboxic and has relatively high oxygen minimum values of about 17 μmol kg⁻¹ in the South Atlantic and more than 40 μmol kg⁻¹ in the North Atlantic. About 20 (40%) of the North Pacific volume is occupied by an OMZ when using 45 μmol kg⁻¹ (or 90 μmol kg⁻¹, respectively) as an upper bound for OMZ oxygen concentration for ocean densities lighter than σ_θ < 27.2 kg m⁻³. The relative volumes reduce to less than half for the South Pacific (7% and 13%, respectively). The abundance of OMZs are considerably smaller (1% and 7%) for the South Atlantic and only 0% and 5% for the North Atlantic. Thermal domes characterized by upward displacements of isotherms located in the northeastern Pacific and Atlantic and in the southeastern Atlantic are co-located with the centres of the OMZs. They seem not to be directly involved in the generation of the OMZs.OMZs are a consequence of a combination of weak ocean ventilation, which supplies oxygen, and respiration, which consumes oxygen. Oxygen consumption can be approximated by the apparent oxygen utilization (AOU). However, AOU scaled with an appropriate consumption rate (aOUR) gives a time, the oxygen age. Here we derive oxygen ages using climatological AOU data and an empirical estimate of aOUR. Averaging oxygen ages for main thermocline isopycnals of the Atlantic and Pacific Ocean exhibit an exponential increase with density without an obvious signature of the OMZs. Oxygen supply originates from a surface outcrop area and can also be approximated by the turn-over time, the ratio of ocean volume to ventilating flux. The turn-over time corresponds well to the average oxygen ages for the well ventilated waters. However, in the density ranges of the suboxic OMZs the turn-over time substantially increases. This indicates that reduced ventilation in the outcrop is directly related to the existence of suboxic OMZs, but they are not obviously related to enhanced consumption indicated by the oxygen ages. The turn-over time suggests that the lower thermocline of the North Atlantic would be suboxic but at present this is compensated by the import of water from the well ventilated South Atlantic. The turn-over time approach itself is independent of details of ocean transport pathways. Instead the geographical location of the OMZ is to first order determined by: (i) the patterns of upwelling, either through Ekman or equatorial divergence, (ii) the regions of general sluggish horizontal transport at the eastern boundaries, and (iii) to a lesser extent to regions with high productivity as indicated through ocean colour data.  相似文献   

Volcano-tectonic structures and CO2-degassing patterns in the Laacher See basin,Germany     

Andreas Goepel  Martin Lonschinski  Lothar Viereck  Georg Büchel  Nina Kukowski 《International Journal of Earth Sciences》2015,104(5):1483-1495

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Reservoirs as sentinels of catchments: the Rappbode Reservoir Observatory (Harz Mountains, Germany)   总被引：2，自引：2，他引：0  

Karsten Rinke  Burkhard Kuehn  Serghei Bocaniov  Katrin Wendt-Potthoff  Olaf Büttner  Jörg Tittel  Martin Schultze  Peter Herzsprung  Helmut Rönicke  Karsten Rink  Kristine Rinke  Maren Dietze  Marco Matthes  Lothar Paul  Kurt Friese 《Environmental Earth Sciences》2013,69(2):523-536

Reservoirs can be viewed as sentinels of their catchments and a detailed monitoring of reservoir systems informs about biogeochemical and hydrological processes at the catchment scale. We developed a comprehensive online monitoring system at Rappbode reservoir, the largest drinking water reservoir in Germany, and its inflows. The Rappbode Reservoir Observatory comprises of a set of online-sensors for the measurement of physical, chemical, and biological variables and is complemented by a biweekly limnological sampling schedule. Measurement stations are deployed at the four major inflows into the system, at the outlets of all pre-reservoirs, as well as in the main reservoir. The newly installed monitoring system serves both scientific monitoring and process studies, as well as reservoir management. Particular emphasis is paid to the monitoring of short-term dynamics and many variables are measured at high temporal resolution. As an example, we quantitatively documented a flood event which mobilised high loads of dissolved organic carbon and changed the characteristics of the receiving reservoir from eutrophic to dystrophic within a few days. This event could have been completely missed by conventional biweekly sampling programs, but is relevant for biogeochemical fluxes at the catchment scale. We also show that the high frequency data provide a deeper insight into ecosystem dynamics and lake metabolism. The Rappbode Reservoir Observatory; moreover, offers a unique study site to apply, validate, and develop state of the art lake models to improve their predictive capabilities.  相似文献