Pinched between the plates: Armenia's voluminous record of volcanic activity

Located in the heart of the Lesser Caucasus mountains, where the Arabian and Eurasian tectonic plates collide, Armenia occupies an exceptional geological position shaped through millions of years of subduction and collision. It is a unique place on the Earth recording extensive intrusive and volcanic activity related to the long-standing continental convergence. The volcanoes of Armenia provide a rare opportunity to study the sources and processes involved in this unusual type of magmatism. More than 500 Quaternary volcanoes have been mapped in Armenia, most of them formed from single eruptive episodes. Among several large composite volcanoes, the mighty Aragats stands out as the largest volcano in Armenia and the region altogether. Volcanic deposits testify to the range of eruptive styles—from the ignimbrites formed in eruptions as explosive and voluminous as any seen globally in the modern era to the enormous fissure-fed lava flows that form the Southern Caucasus flood basalt province, the smallest and youngest Large Igneous Province in the world. Several pre-historical and historical eruptions have been documented, highlighting the potential for future volcanic activity in the region. In recent years, research has focused on the volcanic hazards associated with the Armenian Nuclear Power Plant, located in the foothills of Aragats volcano. This article highlights some of the extraordinary volcanic and intrusive features observed in Armenia and summarizes aspects of recent volcanological and petrological research.     

Stepwise atmospheric carbon-isotope excursion during the Toarcian Oceanic Anoxic Event (Early Jurassic,Polish Basin)

During the Mesozoic (250–64 Ma) intervals of about 0.5 Myr were subject to severe environmental changes, including high sea-surface temperature and very low oxygen content of marine water. These Oceanic Anoxic Events, or OAEs, occurred simultaneously with profound disturbance to the carbon cycle. The carbon-isotope anomaly in the Early Jurassic that marks the Toarcian Oceanic Anoxic Event (T-OAE) at ~ 182 Ma is characterized in marine sections by a series of dramatic steps towards lighter values. Herein we present new carbon-isotope data from terrestrial organic matter (phytoclast separates), collected through a Late Pliensbachian–Middle Toarcian coastal and marginal marine succession in the Polish Basin, a setting where hinterland climate and sea-level change are well recorded. The results show that the shift to light carbon-isotope values in the woody organic matter, and therefore also in atmospheric carbon dioxide, similarly occurred in major steps. The steps are here correlated with those identified from marine organic matter, where they have previously been attributed to 100 kyr eccentricity forcing of climate. The results provide strong support for orbitally and climatically controlled release of isotopically light carbon from gas hydrates into the ocean–atmosphere system in a series of rapid bursts. Additionally, a link between the carbon-isotope steps and shoreline movements can be demonstrated. Individual peaks of the negative excursion are mostly associated with facies indicative of sea-level rise (flooding surfaces). However, at the same time inferred higher atmospheric carbon-dioxide content may be expected to have resulted in increased rainfall and temperature, leading to accelerated weathering and erosion, and consequently increased sediment supply, progradation and regression, causing some mismatches between isotope shifts and inferred sea-level changes. Enhanced abundance of megaspores derived from hydrophilic plant groups, and marked increase in kaolinite, are coincident with the overall development of the negative isotope excursion. The combined data suggest that each 100-kyr cycle in carbon-isotope values was characterized by increasingly severe palaeoclimatic change, culminating in extremely hot and humid conditions co-incident with the peak of the final most negative carbon-isotope excursion. The chemostratigraphic correlation allows very precise dating of the Late Pliensbachian–Middle Toarcian coastal and marginal marine sedimentary succession in the Polish Basin.     

Testing the anelastic nonhydrostatic model EULAG as a prospective dynamical core of a numerical weather prediction model Part II: Simulations of supercell

The anelastic nonhydrostatic model EULAG is a candidate for the future dynamical core of a numerical weather prediction model. Achieving such an objective requires a number of experiments focused on testing correctness of the solutions and robustness of the solver. In the spirit of this idea, a set of tests related to standard atmospheric problems was performed, of which the two regarding development and evolution of a supercell were employed as benchmarks of moist dynamics of the model. Their results are discussed in this paper. Development and evolution of a stormsystem with a set of characteristic features such as stormsplitting along with the generation of horizontal vorticity and cold pool formation is investigated. In addition, the influence of domain geometry, boundary conditions and subgrid-scale mixing is examined.     

Influence of selected fluorescent dyes on small aquatic organisms

Rhodamine B and Rhodamine WT are fluorescent dyes commonly used as tracers in hydrological investigations. Since introducing intensely red substances into rivers raises understandable doubts of ecological nature, the authors aimed at examining the influence of these dyes on small water fauna using bioindication methods. Quantitative results, calculated with the use of Bliss-Weber probit statistical method, were achieved by means of standardized ecotoxicological tests containing ready-to-hatch resting forms of fairy shrimp (Thamnocephalus platyurus). Qualitative studies included observation of water flea crustacean (Daphnia magna) and horned planorbis snail (Planorbis corneus), both typically present in rivers and representative for temperate climate, as well as guppy fish (Poecilla reticulata), paramecium protozoan (Paramaecium caudatum) and the above-mentioned fairy shrimp. The investigation revealed that both dyes in concentrations used for hydrological purposes are low enough to exert almost no toxic impact on water fauna considered.     

Spin and twist motions in the earthquake preparation processes: Analysis of records

Three seismic events in L’Aquila region and one in western Greece have been chosen for comparative analysis of two kinds of seismic motions, spin and twist. These torque components of the seismic field were detected in horizontal plane with the rotational seismometers. Homologous parts were sought in the signals of spin and twist components — curve of one component was compared to the other directly and after transformations: phase-shifting and sign reversal. To achieve better clarity, these operations were done on the data divided into several descendant signals with the use of band-pass filtration. Conformities of spin and twist, revealed in this way, are assumed to be results of distant processes in the source, where relations between rotational and shear motions include retardations.     

Mechanism of sulfide mineralization through successive metasomatic replacement stages of zoned host dolomite in Cracow-Silesian Zn-Pb deposits (Mississippi Valley type), Pomorzany Mine,Poland

Replacement of dolomite rhombs is zone selective in Cracow-Silesian Zn-Pb deposits. The discussed replacement of dolomite by sphalerite occurs as spotted sphalerite ore constituting about one-fourth of the economic sulfide mineralization of the Pomorzany Mine. Replacement is controlled by two factors, i.e., microporosity and chemical composition. The epigenetic host dolomite rhombs are zoned into three main zones, i.e., the outer rhombohedral rim which is hard and Fe rich with remarkable Zn content, the inner zone which is porous and Zn rich but usually low in Fe content, and the core of the dolomite rhombs which is Fe free but may contain some Zn. Zones rich in Zn were the first to be replaced by sphalerite; the same holds true for zones with higher microporosity showing a high degree of crystallographic disorder of cations. The other zones seem to be intact. There are four successive replacement stages, i.e., partial, moderate, intense, and advanced. During replacement the intact parts become more Zn-rich, consequently being replaced completely in the later stages, the greater the zinc content in the host dolomite is, the more reactive it is to replacement by sphalerite. The liberated iron from replaced Fe-rich zones is fixed as finely crystalline pyrite.     

Criteria for internal reliability of linear least squares models

An approach to analysis of internal reliability of linear least squares models is presented. It is based on the relationship between a single observational disturbance, i.e. a gross error or a blunder, and the model response being a certain pattern of distortions in the least squares residuals. Rigorous formulae describing this relationship in terms of internal reliability characteristics are derived both for the models with uncorrelated and correlated observations. A specific case of decorrelated observations is also taken into consideration. Finally, the criteria for the evaluation of the model internal reliability are proposed for all the above cases. It is worth mentioning that the criteria are obtained without resorting to any particular method of statistical testing. The theory is illustrated with two numerical examples, using simple measuring schemes.     

TL dating of partially bleached sediments by the regeneration method

Thermoluminescence dating of sediments in the Warsaw laboratory is based on blue-to-green emission. The ‘partial bleach + regeneration’ method is proposed for dating sediments which have not been completely bleached at the time of burial. Correct TL ages are reported for sediments covering organic deposits of the Eemian Interglacial and also for glacial sediments of Würm and Riss age. We obtained good results for dating till using the partial bleach + regeneration method. The TL zeroing in till is explained by the ‘rubbing’ or compression of grains beneath the glacier and by the freeze-thaw activity occurring during glacial transport and deglaciation.