Numerical modelling of clast rotation during soft-sediment deformation: a case study in Miocene delta deposits     

M. Hölzel  B. Grasemann  M. Wagreich 《International Journal of Earth Sciences》2006,95(5):921-928

A numerical model for a rotated clast in a sedimentary matrix is presented, quantifying the deformation in associated soft-sediment deformation structures. All the structures occur in a southwards prograding deltaic sequence within the Miocene Ingering Formation, deposited at the northern margin of the Fohnsdorf Basin (Eastern Alps, Austria). Debris flow and pelitic strata contain boudins, pinch-and-swell structures, ptygmatic folds, rotated top-to-S reverse faults and rigid clasts, developed under different stress conditions within the same layers. The deformation around a 24×10 cm trapezoid-shaped rigid clast, resembling the δ-clast geometry in metamorphic rocks, has been modelled using a 2D finite element modelling software. Under the chosen initial and boundary conditions the rotational behaviour of the clast mainly depends on the proportions of pure and simple shear; best fitting results were attained with a dominantly pure shear deformation (~65–85%), with stretching parallel and shortening normal to the bedding. In this specific model set-up, the initial sedimentary thickness is reduced by 30%, explained by stretching due to sediment creeping and compaction. The high amount of pure shear deformation proposed is compatible with the observed layer-parallel boudinage and pinch-and-swell structures. Rotated faults and ptygmatic folds were caused by the minor component of bedding-parallel simple shear.  相似文献   

The Influence of Thermal Effects on the Wind Speed Profile of the Coastal Marine Boundary Layer   总被引：1，自引：3，他引：1  

Bernhard Lange  Søren Larsen  Jørgen Højstrup  Rebecca Barthelmie 《Boundary-Layer Meteorology》2004,112(3):587-617

The wind speed profile in a coastal marine environment is investigated with observations from the measurement program Rødsand, where meteorological data are collected with a 50 m high mast in the Danish Baltic Sea, about 11 km from the coast. When compared with the standard Monin—Obukhov theory the measured wind speed increase between 10 m and 50 m height is found to be systematically larger than predicted for stable and near-neutral conditions. The data indicate that the deviation is smaller for short (10–20 km) distances to the coast than for larger (>30 km) distances. The theory of the planetary boundary layer with an inversion lid offers a qualitative explanation for these findings. When warm air is advected over colder water, a capping inversion typically develops. The air below is constantly cooled by the water and gradually develops into a well-mixed layer with near-neutral stratification. Typical examples as well as scatter plots of the data are consistent with this explanation. The deviation of measured and predicted wind speed profiles is shown to be correlated with the estimated height and strength of the inversion layer.  相似文献   

Dry melting of muscovite+quartz in the range P s=7 kb to P s=20 kb     

Bernhard Storre 《Contributions to Mineralogy and Petrology》1972,37(1):87-89

Experimental data obtained for dry melting of muscovite + quartz show that the stability field of this assemblage is extended to higher temperatures compared with the corresponding melting reactions with excess vapor which have been determined by Storre and Karotke (1971, 1972).  相似文献   

Boreale Einflüsse im Oberjura Westeuropas?     

Doz. Dr. Bernhard Ziegler 《International Journal of Earth Sciences》1964,54(1):250-261

Zusammenfassung Die allmähliche Abnahme der Formen-Mannigfaltigkeit gegen Norden deutet ebenso wie die Nordgrenze des Vorkommens von Riff-Korallen, Diceraten, Nerineen und Oppelien auf Unterschiede in der Meeres-Temperatur. Einer südlichen tropischen Region steht eine gemä\igte (boreale) Zone im Norden gegenüber. Nordwesteuropa liegt im übergangsbereich.Während des Oberjura ist keine allgemeine änderung der Meeres-Temperaturen nachweisbar. Die faziellen und faunistischen Besonderheiten im Mittel- und Obermalm Nordwesteuropas lassen sich am besten durch eine Verlagerung von Meeres-Strömungen erklären.

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Summary In the Upper Jurassic of Europe there is a northern boundary in the distribution of reef-corals, Diceratids, Nerineids, and Oppeliids. This feature and the greater number of species and genera in southern regions than in the North points to differences in the temperature of the Sea. It is possible to separate a southern tropical region from a temperate (boreal) zone in the North. Northwestern Europe is situated in between.During the Upper Jurassic no general change in the temperature of the sea can be observed. Peculiarities in facies and fauna of the northwestern European Upper Jurassic are well explained by displacements of currents in the Sea.

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Résumé Dans le Jurassique supérieur de l'Europe une région tropicale méridionale peut Être séparée d'une zone (« boreale ») tempérée dans le Nord. L'Europe du nord-ouest est située dans le domaine transitaire. Pendant le Jurassique supérieur aucun changement de la température de la mer est à constater. Les particuliarités du facies et de la faune dans le Malm moyen et supérieur de l'Europe du nord-ouest sont très facilement à expliquer par un déplacement de courrents dans la mer.

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Für wertvolle Hinweise danke ich Dr. K. W.Barthel (München), Dr. O. F.Geyer (Stuttgart), Prof. Dr. E.Kuhn-Schnyder und Dr. H.Rieber (beide Zürich).  相似文献   

Early Paleozoic rifting and bimodal volcanism in the Ossa-Morena Zone of south-west Spain     

Uwe Giese  Bernhard Bühn 《International Journal of Earth Sciences》1994,83(1):143-160

Lower Paleozoic volcanic members have been investigated by geological, petrographical and geochemical means in a traverse across the Ossa-Morena Zone (OMZ) in south-west Spain.The volcanism lasted from the Early Cambrian to the Early Ordovician, with a peak in the Middle Cambrian. The volcanism is bimodal, starting up with acidic and ending with basic compositions. From north to south, peralkaline rhyolites change to rhyolites, and strongly enriched alkali basalts change via transitional basalts to mid-ocean ridge basalt (MORB-type basalts). The geological and magmatic evolution suggests an extensive Early Paleozoic rifting with its center along the southern boundary of the OMZ. Temporal, spatial and crustal aspects of the rifting event are presented in a geodynamic model.  相似文献   

UV‐Irradiation of the Antibiotic Sulfathiazole Surprisingly Leads to Former Antituberculotic Promizole          下载免费PDF全文

Astrid Spielmeyer  Myriam Heer  Siegrun A.I. Mohring  Heike Hausmann  Jessica Stahl  Manfred Kietzmann  Sebastian Dold  Bernhard Spengler  Gerd Hamscher 《洁净——土壤、空气、水》2015,43(4):490-495

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Analogue modeling of the role of multi-level decollement layers on the geometry of orogenic wedge: an application to the Zagros Fold–Thrust Belt,SW Iran     

Ghanadian  Mostafa  Faghih  Ali  Grasemann  Bernhard  Fard  Iraj Abdollahie  Maleki  Mehrdad 《International Journal of Earth Sciences》2017,106(8):2837-2853

International Journal of Earth Sciences - The presence of evaporate and incompetent formations (i.e., decollement horizons) within the sedimentary sequence of fold-thrust belts can control their...  相似文献   

Quantitative relationship between water-depth and sub-fossil ostracod assemblages in Lake Donggi Cona,Qinghai Province,China     

Steffen Mischke  Ulrich Bößneck  Bernhard Diekmann  Ulrike Herzschuh  Huijun Jin  Annette Kramer  Bernd Wünnemann  Chengjun Zhang 《Journal of Paleolimnology》2010,43(3):589-608

A calibration data set of 51 surface sediment samples from Lake Donggi Cona on the northeastern Tibetan Plateau was investigated to study the relationship between sub-fossil ostracod assemblages and water depth. Samples were collected over a depth range from 0.6 to 80 m. A total of 16 ostracod species was identified from the lake with about half of the species restricted to the Tibetan Plateau and its adjacent mountain ranges and poorly known in terms of ecological preferences, and the other half displaying a mainly Holarctic distribution. Living macrophytes and macroalgae were recorded in Lake Donggi Cona down to a depth of about 30 m, and bivalve (Pisidium cf. zugmayeri) and gastropod (Gyraulus, Radix) shells were found down to depths of 43 and 48 m, respectively. The ostracod-water-depth relationship was assessed by multivariate statistical analysis and ostracod-based transfer functions for water depth were constructed. Weighted averaging partial least squares (WA-PLS) regression provided the best model with a coefficient of determination r ² of 0.91 between measured and ostracod-inferred water depth, a root mean square error of prediction of 8% and a maximum bias of 10.6% of the gradient length, as assessed by leave-one-out cross-validation. Our results show the potential of ostracods as palaeo-depth indicators in appropriate settings. However, transfer-function applications using fossil ostracod assemblages for palaeo-depth estimations require a thorough understanding of the palaeolimnological conditions of lakes and therefore detailed multi-proxy analysis to avoid misinterpretation of ostracod-based inferences.  相似文献   

Sediment provenance of late Quaternary morainic,fluvial and loess‐like deposits in the southwestern Verkhoyansk Mountains (eastern Siberia) and implications for regional palaeoenvironmental reconstructions     

Steffen Popp  Innokenty Belolyubsky  Frank Lehmkuhl  Andrei Prokopiev  Christine Siegert  Valentin Spektor  Georg Stauch  Bernhard Diekmann 《Geological Journal》2007,42(5):477-497

A provenance analysis of late Quaternary deposits from tributaries of the Aldan and Lena rivers in Central Yakutia (eastern Siberia) was carried out using analysis of heavy minerals and clay mineralogy. Cluster analysis revealed one assemblage that is characterized by relatively high proportions of amphibole, orthopyroxene and garnet as well as pedogenic clay minerals, reflecting a sediment provenance from the wide catchment area of the Lena and Aldan rivers. In contrast, the three other clusters are dominated by stable heavy minerals with varying amounts of clinopyroxene, apatite and garnet, as well as high percentages of illite and chlorite that are indicative of source rocks of the Verkhoyansk Mountains. Glacial moraines reveal the local mountain source signal that is overprinted by the Lena‐Aldan signal in the oldest moraines by reworking processes. Alluvial sediments in the Verkhoyansk Foreland show a clear Lena source signal through intervals of the middle and late Pleistocene, related to a stream course closer to the mountains at that time. Loess‐like cover sediments are characterized by the dominant Lena provenance with increasing proportions of local mountain sources towards the mountain valleys. Aeolian sands in an alluvial terrace section at the mountain margin covering the time between 30 ka and 10 ka BP reflect temporarily dominant inputs of aeolian materials from the Lena Plains. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Development of Iron Speciation Reference Materials for Palaeoredox Analysis     

Lewis J. Alcott  Alexander J. Krause  Emma U. Hammarlund  Christian J. Bjerrum  Florian Scholz  Yijun Xiong  Andrew J. Hobson  Lesley Neve  Benjamin J. W. Mills  Christian Mrz  Bernhard Schnetger  Andrey Bekker  Simon W. Poulton 《Geostandards and Geoanalytical Research》2020,44(3):581-591

The development and application of geochemical techniques to identify redox conditions in modern and ancient aquatic environments has intensified over recent years. Iron (Fe) speciation has emerged as one of the most widely used procedures to distinguish different redox regimes in both the water column and sediments, and is the main technique used to identify oxic, ferruginous (anoxic, Fe(II) containing) and euxinic (anoxic, sulfidic) water column conditions. However, an international sediment reference material has never been developed. This has led to concern over the consistency of results published by the many laboratories that now utilise the technique. Here, we report an interlaboratory comparison of four Fe speciation reference materials for palaeoredox analysis, which span a range of compositions and reflect deposition under different redox conditions. We provide an update of extraction techniques used in Fe speciation and assess the effects of both test portion mass, and the use of different analytical procedures, on the quantification of different Fe fractions in sedimentary rocks. While atomic absorption spectroscopy and inductively coupled plasma‐optical emission spectrometry produced comparable Fe measurements for all extraction stages, the use of ferrozine consistently underestimated Fe in the extraction step targeting mixed ferrous–ferric minerals such as magnetite. We therefore suggest that the use of ferrozine is discontinued for this Fe pool. Finally, we report the combined data of four independent Fe speciation laboratories to characterise the Fe speciation composition of the reference materials. These reference materials are available to the community to provide an essential validation of in‐house Fe speciation measurements.  相似文献