Lake Floor Morphology and Sediment Architecture of Lake Torneträsk,Northern Sweden     

Hendrik Vogel  Bernd Wagner  Peter Rosén 《Geografiska Annaler: Series A, Physical Geography》2013,95(2):159-170

Here we present datasets from a hydroacoustic survey in July 2011 at Lake Torneträsk, northern Sweden. Our hydroacoustic data exhibit lake floor morphologies formed by glacial erosion and accumulation processes, insights into lacustrine sediment accumulation since the beginning of deglaciation, and information on seismic activity along the Pärvie Fault. Features of glacial scouring with a high‐energy relief, steep slopes, and relative reliefs of more than 50 m are observed in the large W‐basin. The remainder of the lacustrine subsurface appears to host a broad variety of well preserved formations from glacial accumulation related to the last retreat of the Fennoscandian ice sheet. Deposition of glaciolacustrine and lacustrine sediments is focused in areas situated in proximity to major inlets. Sediment accumulation in distal areas of the lake seldom exceeds 2 m or is not observable. We assume that lack of sediment deposition in the lake is a result of different factors, including low rates of erosion in the catchment, a previously high lake level leading to deposition of sediments in higher elevated paleodeltas, tributaries carrying low suspension loads as a result of sedimentation in upstream lakes, and an overall low productivity in the lake. A clear off‐shore trace of the Pärvie Fault could not be detected from our hydroacoustic data. However, an absence of sediment disturbance in close proximity to the presumed fault trace implies minimal seismic activity since deposition of the glaciolacustrine and lacustrine sediments.  相似文献   

Geology,mineral chemistry and tourmaline B isotopes of the Córrego Bom Sucesso area,southern Serra do Espinhaço,Minas Gerais,Brazil: Implications for Au–Pd–Pt exploration in quartzitic terrain     

Alexandre Raphael Cabral  Bernd Lehmann  Miguel Tupinambá  Michael Wiedenbeck  Michael Brauns 《Journal of Geochemical Exploration》2011

The Palaeo-Mesoproterozoic metasiliciclastic rocks of the southern Serra do Espinhaço, Minas Gerais, Brazil, are host to historically important alluvial deposits of diamonds and gold. Detrital gold grains often comprise Au–Pd–Pt intermetallic compounds, with low Ag contents, which contain inclusions of tourmaline and titaniferous hematite (up to ~ 6 wt.% TiO₂). The latter minerals connect the alluvial mineralisation to the rutile–hematite–quartz veins and tourmalinisation observed in the quartzitic country rocks of the alluvial gravel. The quartzite (Sopa-Brumadinho Formation of lacustrine to fan-deltaic origin) is affected by pervasive B metasomatism with F-bearing tourmaline replacing the recrystallised quartz fabric. The tourmaline belongs to the alkali group, with Mg/(Mg + Fe) and X/(X + Na) ratios in the ranges from 0.5 to 0.7 and 0.18 to 0.29, respectively, where X represents vacancies in the X site. Boron-isotopic values of tourmaline vary from ~ 1 to − 10.4‰ δ¹¹B. The B-isotope range, in conjunction with the Na–Mg-rich tourmaline composition, and the widespread occurrence of tourmalinite in the Sopa-Brumadinho Formation suggest a derivation from non-marine evaporitic brines. Brines are capable of transporting otherwise immobile Ti and explain, under oxidising conditions, the fractionation of Ag from Pd to precipitate palladiferous gold with extremely high Pd/Ag ratios. Zirconium-in-rutile and Ti-in-quartz temperatures for a variety of hematite-rich veins suggest episodic vein emplacement over a temperature range from around 500 °C to ~ 350 °C. Cross-cutting relationships and episodic vein emplacement indicate a late-Brasiliano age.  相似文献   

Lattice-preferred orientations of late-Variscan granitoids derived from neutron diffraction data: implications for magma emplacement mechanisms     

Axel Müller  Bernd Leiss  Klaus Ullemeyer  Karel Breiter 《International Journal of Earth Sciences》2011,100(7):1515-1532

The lattice-preferred orientation (LPOs) of two late-Variscan granitoids, the Meissen monzonite and the Podlesí dyke granite, were determined from high-resolution time-of-flight neutron diffraction patterns gained at the diffractometer SKAT in Dubna, Russia. The results demonstrate that the method is suitable for the LPO analysis of polyphase, relatively coarse-grained (0.1–6 mm) rocks. The Meissen monzonite has a prominent shape-preferred orientation (SPO) of the non-equidimensional minerals feldspar, mica and amphibole, whereas SPO of the Podlesí granite is unapparent at the hand-specimen scale. The neutron diffraction data revealed distinct LPOs in both granitoids. The LPO of the non-equidimensional minerals feldspar, mica and amphibole developed mainly during magmatic flow. In the case of the Meissen monzonite, the magmatic flow was superimposed by regional shear tectonics, which, however, had no significant effect on the LPOs. In both samples, quartz shows a weak but distinct LPO, which is atypical for plastic deformation and different in the syn-kinematic Meissen monzonite and the post-kinematic Podlesí granite. We suggest that, first of all, the quartz LPO of the Meissen monzonite is the result of oriented growth in an anisotropic stress field. The quartz LPO of the Podlesí granite, which more or less resembles a deformational LPO in the flattening field of the local strain field, developed during magmatic flow, whereby the rhombohedral faces of the quartz crystals adhered to the (010) faces of aligned albite and to the (001) faces of zinnwaldite. Due to shape anisotropy of their attachments, the quartz crystals were passively aligned by magmatic flow. Thus, magmatic flow and oriented crystal growth are the major LPO-forming processes in both granitoids. For the Meissen monzonite, the solid-state flow was too weak to cause significant crystallographic re-orientation of the minerals aligned by magmatic flow. Finally, the significance of our results for the evaluation of the regional tectonic environment during magma emplacement is discussed. The discussion on the regional implications of the more methodologically oriented results provides the basis for future, more regionally aimed studies in view of the fabric characteristics of such plutons and their developing mechanisms.  相似文献   

Microfacies and diagenesis of older Pleistocene (pre‐last glacial maximum) reef deposits,Great Barrier Reef,Australia (IODP Expedition 325): A quantitative approach     

Eberhard Gischler  Alex L. Thomas  André W. Droxler  Jody M. Webster  Yusuke Yokoyama  Bernd R. Schöne 《Sedimentology》2013,60(6):1432-1466

During Integrated Ocean Drilling Program Expedition 325, 34 holes were drilled along five transects in front of the Great Barrier Reef of Australia, penetrating some 700 m of late Pleistocene reef deposits (post‐glacial; largely 20 to 10 kyr bp ) in water depths of 42 to 127 m. In seven holes, drilled in water depths of 42 to 92 m on three transects, older Pleistocene (older than last glacial maximum, >20 kyr bp ) reef deposits were recovered from lower core sections. In this study, facies, diagenetic features, mineralogy and stable isotope geochemistry of 100 samples from six of the latter holes were investigated and quantified. Lithologies are dominated by grain‐supported textures, and were to a large part deposited in high‐energy, reef or reef slope environments. Quantitative analyses allow 11 microfacies to be defined, including mixed skeletal packstone and grainstone, mudstone‐wackestone, coral packstone, coral grainstone, coralline algal grainstone, coral‐algal packstone, coralline algal packstone, Halimeda grainstone, microbialite and caliche. Microbialites, that are common in cavities of younger, post‐glacial deposits, are rare in pre‐last glacial maximum core sections, possibly due to a lack of open framework suitable for colonization by microbes. In pre‐last glacial maximum deposits of holes M0032A and M0033A (>20 kyr bp ), marine diagenetic features are dominant; samples consist largely of aragonite and high‐magnesium calcite. Holes M0042A and M0057A, which contain the oldest rocks (>169 kyr bp ), are characterized by meteoric diagenesis and samples mostly consist of low‐magnesium calcite. Holes M0042A, M0055A and M0056A (>30 kyr bp ), and a horizon in the upper part of hole M0057A, contain both marine and meteoric diagenetic features. However, only one change from marine to meteoric pore water is recorded in contrast with the changes in diagenetic environment that might be inferred from the sea‐level history. Values of stable isotopes of oxygen and carbon are consistent with these findings. Samples from holes M0032A and M0033A reflect largely positive values (δ¹⁸O: ?1 to +1‰ and δ¹³C: +1 to +4‰), whereas those from holes M0042A and M0057A are negative (δ¹⁸O: ?4 to +2‰ and δ¹³C: ?8 to +2‰). Holes M0055A and M0056A provide intermediate values, with slightly positive δ¹³C, and negative δ¹⁸O values. The type and intensity of meteroric diagenesis appears to have been controlled both by age and depth, i.e. the time available for diagenetic alteration, and reflects the relation between reef deposition and sea‐level change.  相似文献   

In memory of Budagovskii Anatolii Ivanovich (1912–2008)     

Olaf Teschke  Bernd Wegner  Dirk Werner 《Water Resources》2009,36(2):240-241

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Interactive Visualization to Advance Earthquake Simulation     

Louise H. Kellogg  Gerald W. Bawden  Tony Bernardin  Magali Billen  Eric Cowgill  Bernd Hamann  Margarete Jadamec  Oliver Kreylos  Oliver Staadt  Dawn Sumner 《Pure and Applied Geophysics》2008,165(3-4):621-633

The geological sciences are challenged to manage and interpret increasing volumes of data as observations and simulations increase in size and complexity. For example, simulations of earthquake-related processes typically generate complex, time-varying data sets in two or more dimensions. To facilitate interpretation and analysis of these data sets, evaluate the underlying models, and to drive future calculations, we have developed methods of interactive visualization with a special focus on using immersive virtual reality (VR) environments to interact with models of Earth’s surface and interior. Virtual mapping tools allow virtual “field studies” in inaccessible regions. Interactive tools allow us to manipulate shapes in order to construct models of geological features for geodynamic models, while feature extraction tools support quantitative measurement of structures that emerge from numerical simulation or field observations, thereby enabling us to improve our interpretation of the dynamical processes that drive earthquakes. VR has traditionally been used primarily as a presentation tool, albeit with active navigation through data. Reaping the full intellectual benefits of immersive VR as a tool for scientific analysis requires building on the method’s strengths, that is, using both 3D perception and interaction with observed or simulated data. This approach also takes advantage of the specialized skills of geological scientists who are trained to interpret, the often limited, geological and geophysical data available from field observations.  相似文献   

湘西金矿及其区域马底驿组锑分布的多峰结构--累积概率格纸在金矿成因和找矿中的应用     

马东升  Bernd Lehmann 《矿物岩石地球化学通报》2000,19(4):218-220

湖南雪峰弧形构造隆起带(中-上元古界)囊括了该省80％以上的原生金矿(“沃溪式”金矿)和90％以上的砂金,也是世界名的金-锑-钨综合矿化带。其中,赋存于上元古界板溪群马底驿组紫红色板岩中,位于湘西北沅陵县的沃溪金-锑-钨矿,即湘西金矿为代表性矿床。它也是我国仅次于湘中锡矿山的第二大锑矿生产基地。  相似文献   

Backscattered Scanning Electron Microscopy and Image Analysis of Sediments and Sedimentary Rocks: D.H. Krinsley, K. Pye, S. Boggs, Jr., N.K. Tovey     

Bernd Zolitschka 《Journal of Paleolimnology》2000,23(2):223-224

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Spatial crime distribution and prediction for sporting events using social media     

Alina Ristea  Mohammad Al Boni  Bernd Resch  Matthew S. Gerber  Michael Leitner 《International journal of geographical information science》2020,34(9):1708-1739

ABSTRACT

Sporting events attract high volumes of people, which in turn leads to increased use of social media. In addition, research shows that sporting events may trigger violent behavior that can lead to crime. This study analyses the spatial relationships between crime occurrences, demographic, socio-economic and environmental variables, together with geo-located Twitter messages and their ‘violent’ subsets. The analysis compares basketball and hockey game days and non-game days. Moreover, this research aims to analyze crime prediction models using historical crime data as a basis and then introducing tweets and additional variables in their role as covariates of crime. First, this study investigates the spatial distribution of and correlation between crime and tweets during the same temporal periods. Feature selection models are applied in order to identify the best explanatory variables. Then, we apply localized kernel density estimation model for crime prediction during basketball and hockey games, and on non-game days. Findings from this study show that Twitter data, and a subset of violent tweets, are useful in building prediction models for the seven investigated crime types for home and away sporting events, and non-game days, with different levels of improvement.  相似文献   

Northern Eurasian lakes – late Quaternary glaciation and climate history – introduction     

Martin Melles  John Inge Svendsen  Grigory Fedorov  Bernd Wagner 《Boreas: An International Journal of Quaternary Research》2019,48(2):269-272

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