Rapid ground deformation corresponding to a mining-induced seismic event followed by a massive collapse

Natural Hazards - On 17 April 2015, the Wujek/?l?sk underground coal mine in Poland was struck by a strong induced tremor of magnitude M4.0. The event was followed by a massive rock burst...     

Root‐related rhodochrosite and concretionary siderite formation in oxygen‐deficient conditions induced by a ground‐water table rise

Sedimentological, mineralogical, stable carbon and oxygen isotope determinations and biomarker analyses were performed on siderite concretions occurring in terrestrial silts to understand their formation and to characterize the sedimentary and diagenetic conditions favouring their growth. High δ¹³C values (6·4‰ on average) indicate that siderite precipitated in an anoxic environment where bacterial methanogenesis operated. The development of anoxic conditions during shallow burial was induced by a change in sedimentary environment from flood plain to swamp, related to a rise of the ground‐water table. Large amounts of decaying plant debris led to efficient oxygen consumption within the pore‐water in the peat. Oxygen depletion, in combination with a decrease in sedimentation rate, promoted anoxic diagenetic conditions under the swamp and favoured abundant siderite precipitation. This shows how a change in sedimentary conditions can have a profound impact on the early‐diagenetic environment and carbonate authigenesis. The concretions contain numerous rhizoliths; they are cemented with calcium‐rhodochrosite, a feature which has not been reported before. The rhodochrosite cement has negative δ¹³C values (?16·5‰ on average) and precipitated in suboxic conditions due to microbial degradation of roots coupled to manganese reduction. The exceptional preservation of the epidermis/exodermis and xylem vessels of former root tissues indicates that the rhodochrosite formed shortly after the death of a root in water‐logged sediments. Rhodochrosite precipitated during the initial stages of concretionary growth in suboxic microenvironments within roots, while siderite cementation occurred simultaneously around them in anoxic conditions. These suboxic microenvironments developed because oxygen was transported from the overlying oxygenated soil into sediments saturated with anoxic water via roots acting as permeable conduits. This model explains how separate generations of carbonate cements having different mineralogy and isotopic compositions, which would conventionally be regarded as cements precipitated sequentially in different diagenetic zones during gradual burial, can form simultaneously in shallow burial settings where strong redox gradients exist around vertically oriented permeable root structures.     

Socioenvironmental issues of river bed material extraction in the Himalayan piedmont (India)

The present study focuses on the Balason river running through the Himalayan piedmont zone (near Siliguri, India). The objective of the study is an assessment of the environmental effects of river bed material extraction by humans and the dependence of indigenous people on the river and its ecosystem services. The analysis is based on results of field work consisting of geodetic measurements of the river channel and interviews among the local community from the Nimtijot village. Historical hydrological data were also used for the study. The results of the investigation show that the Balason river is heavily affected by excessive exploitation of river bed material during dry season and the replenishment of extracted material in a monsoon season is not always sufficient. It leads to channel deepening. The local community working in the river heavily depends for its livelihood on continuing this activity. A decreasing amount of bed material to be extracted may lead to degradation of the strong relationship between the local community and their natural environment (river).     

A mixing-length model for predicting vertical velocity distribution in flows through emergent vegetation

Abstract

The vertical profiles of streamwise velocities are computed on flood plains vegetated with trees. The calculations were made based on a newly developed one-dimensional model, taking into account the relevant forces acting on the volumetric element surrounding the considered vegetation elements. A modified mixing length concept was used in the model. An important by-product of the model is the method for evaluating the friction velocities, and consequently bed shear stresses, in a vegetated channel. The model results were compared with the relevant experimental results obtained in a laboratory flume in which flood plains were covered by simulated vegetation.     

Orthogneisses due to irrotational extension,a case from the Sudetes,Bohemian massif

Orthogneisses occurring in the core of the Orlica-Kodzko dome, NE part of the Bohemian massif, exibit a penetrative, N-S stretching lineation defined by mostly ductile elongation of quartz and dilation of K-feldspar crystals of the former granite, now turned into quartz rods and variously elongated K-feldspar porphyroclasts. N-S stretching of the granite seems to be inconsistent with W-E tectonic transport shown by major folds and thrusts developing concurrently in its schistose envelope. The two major lithologies of the dome, differing in their fabrics and rheological properties, offered a drastically different response to an overall shortening. It is interpreted that folds due to buckling evolved in the mantle rocks and after a certain definite range of incremental shortening suffered extension parallel to their hinges. At that time the statistically isotropic granite body was subjected to the same N-S extension and was deformed in common with its schistose mantle under conditions of irrotational strain which represents an early but significant part of the protracted deformation history related to the granite-gneiss transformation.

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Zusammenfassung Die Orthogneise, die im NE-Teil der Böhmischen Masse den Kern der Adlergebirge-Kodzko-Kuppel bilden, zeigen eine N-S-ausgerichtete Streckungslineation. Die Streckungsfaser ist an plastisch gedehnten Quarz-Aggregaten zu erkennen sowie an Klastenzügen von Kalifeldspat. Große Falten und Überschiebungen in der Schieferhülle des Granits hingegen geben eine W-E Richtung des tektonischen Transports an. Diese entspricht nicht der Längung des Granits.Zur Deutung werden die unterschiedlichen rheologischen Eigenschaften des Granits und seiner Hüllgesteine herangezogen, die auf Unterschieden der Zusammensetzung und des Gefüges beruhen. Diese Unterschiede bewirken, daß die Hüllgesteine zunächst Biegefaltung erleben bis weitere Einengung durch Faltung unmöglich wird. Daraufhin werden die Hüllgesteine parallel zur Faltenachse in N-S-Richtung gedehnt. Diese Dehnungsrichtung ist allein und von Anfang an den isotropen Graniten überprägt.Die Deformation erfolgte irrotational und nahezu als achsialsymmetrische Streckung. Sie stellt ein frühes, aber wichtiges Stadium der Umwandlung dieses Granits zu Gneisen dar.

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Résumé Les orthogneiss qui constituent le coeur du dôme d'Orlica-kodzko (région nord-est du massif de Bohème) présentent une linéation d'étirement pénétrative orientée nordsud. Cette linéation est exprimée principalement par l'allongement ductile en bâtonnets d'agrégats de quartz et par l'alignement de porphyroclastes de feldspath potassique. D'autre part, dans l'encaissant schisteux du granite, les grands plis et les charriages indiquent une direction ouest-est du transport tectonique, ce qui ne semble donc pas correspondre à la structure de l'orthogneiss central.Ce contraste est interprété par la différence entre les propriétés rhéologiques des deux ensembles lithologiques, qui ont répondu de manières différentes au processus de raccourcissement régional. Dans les roches de l'enveloppe, se sont formés d'abord des plis de courbure, jusqu'à un certain degré de raccourcissement, après quoi, ce processus n'étant plus possible, elles ont subi un étirement parallèle aux axes de ces plis. Le corps granitique isotrope, au contraire, a réagi dès le début par une extension nord-sud. Ces conditions de déformation irrotationnelle, à symétrie quasi-axiale, représentent un stade précoce, mais significatif de la transformation du granite en orthogneiss.

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Rip currents as a geological tool

This paper considers the nature and sedimentary significance of rip currents. Rip currents are the main factor responsible for the transport of coarse sediments from the littoral zone to greater depths. Such sediments, deposited outside the zone of wave deformation, may be identified as storm rip current increments within sediments deposited during fair weather. Composite beds deposited during a given wave cycle by storm rip currents are closely similar to ‘turbidites’ and many so called ‘fluxo-turbidites’ described from flysch deposits. Using data gathered in studies conducted on the modern Baltic coast, supplemented by experimental work and theoretical considerations, a sedimentary model is proposed. The model may be used to interpret possible rip current deposits among shallow water ‘turbidites’, and both modern storm sediments and ancient ‘tempestites’.     

A Late Tournaisian synmetamorphic folding and thrusting event in the eastern Variscan foreland: 40Ar/39Ar evidence from the phyllites of the Wolsztyn–Leszno High,western Poland

A Variscan foreland in western Poland comprises two NW-trending basement highs, which are concealed under Carboniferous through Triassic strata of the Fore-Sudetic Monocline (FSM). Both highs consist of multiply deformed quartz-sericite - albite - chlorite phyllites of unknown protolith age. ⁴⁰Ar/³⁹Ar laser probe dating of white micas in up to 0.5-mm-thick mica layers, which form the S₂ axial-plane foliation in phyllites of the Wolsztyn-Leszno High, yielded an age of 340.1DŽ.6 Ma for the lower greenschists facies metamorphism and probably also for the F₂ folding. This deformation was associated and followed by thrusting, which brought about the basement highs. The latter delivered clasts to overlying late Viséan-early Namurian flysch basin that was mainly sourced from the Saxothuringian Sudetes in which most of the deformation occurred between 345-335 Ma. The FSM basement may represent an independent terrane, referred to as the Wielkopolska terrane, belonging to the Armorican Terrane Assemblage.     

Studies on Intercorrelation between Ions Co-Occurring in Precipitation in the Gdańsk-Sopot-Gdynia Tricity (Poland)

The paper presents monitoring results and environmental pollution assessment for the Gdask-Sopot-Gdynia Tricity (Poland), based onanalysis of precipitation. Precipitation samples were collected over a period of 12 months (January–December 1998) at ten locations in the Tricity. The following selected ions were determined in the samples:SO₄ ^2–, F^–, Cl^–, NO₃ ^–,PO₄ ^3–, NH₄ ⁺, Na⁺,Mg²⁺, Ca²⁺, K⁺. The results were subjected to full statistical evaluation. Values of the parameters determined were correlated with each other. An attempt was made to explain co-occurrences of certain ions and the significance of their mutual effects. Pollutant concentrations and loads in precipitation were also correlated with data on wind direction and temperature in the region.Deposition of pollutants was very high in spring due to the prevailing air circulation patterns and low temperatures. Analysis of the correlations between co-occurring ions confirmed the significant impact of the location (sea coast) on the composition of rain water. Ionic ratios in rainwater were similar to those observed for sea salt samples. In addition, heavy traffic was most probably responsible for high concentrations of various forms of nitrogen and sulphates in the vicinity of major highways.     

Search for GRB related prompt optical emission and other fast varying objects with “Pi of the Sky” detector

Experiment “Pi of the Sky” is designed to search for prompt optical emission from GRB sources. 32 CCD cameras covering 2 steradians will monitor the sky continuously. The data will be analysed on-line in search for optical flashes. The prototype with 2 cameras operated at Las Campanas (Chile) since 2004 has recognised several outbursts of flaring stars and has given limits for a few GRB.