Tectonic Phase Separation Applied to the Sudetic Marginal Fault Zone(NE part of the Czech Republic)

This study emphasizes the advantage of tectonic phase separation in determination of a tectonic evolution of complicated fault zones. The research focused on the Sudetic Marginal Fault Zone(SMFZ) –a 250 km long active fault zone with documented intraplate seismicity situated on the NE margin of the Bohemian Massif(the Czech Republic). The tectonic history of the SMFZ as well as its kinematic development has been rather complicated and not quite understood. A field structural investigation was carried out in extensive surroundings of the fault zone. The fault-slip data were collected in a number of natural outcrops and quarries with the aim at establishing a robust and field-constrained model for local brittle structural evolution of the studied area. A paleostress analysis was calculated using the collected fault-slip data inversion. The T-Tecto software was utilized for semiautomatic separation of the paleostress phases. Simultaneously three methods of data separation were employed:(1) the Gauss inverse method,(2) the Visualization of Gauss object Function, and(3) the frequency analysis. Within the fault zone multiphase movements were observed on various types of faults as well as wide range of the kinematic indicators orientations. The frequency analysis confirmed the multiphase history of the SMFZ. The calculated tectonic phases were divided according to their relative age as constrained by cross cutting relationships and, where observed, multiple striations on a single fault plane and classified from the oldest to the younger. Data separation and inversion usingT-Tecto software with the Gauss inverse method revealed four different stress phases which are 3 strike-slip stress regimes and one compressional regime. The strike-slip regimes are characterized by σ1 trending NW-SE(43), NNE-SSW(18), ENE-WSW(76) and the compressional one by σ1 trending W-E(26). First, compression occurred parallel to the SMFZ supposedly during the Variscan period. Second, compression at an angle of 60° to general direction of the SMFZ yielded right-lateral movement along the fault zone. This is considered to have occurred during the late-Variscan and post-Variscan period. Third, compression in the W-E direction with almost vertical extension led to reverse movement along the fault zone. This is considered to have occurred during Cenozoic. Fourth, compression almost perpendicular to the SMFZ led to left-lateral transpression along the SMFZ. This is considered to have occurred during Quaternary.     

Comparison of toxicity between populations of Gonyaulax tamarensis of eastern North American waters

Isolates of the dinoflagellate Gonyaulax tamarensis were established from benthic cysts or motile cells collected along the north-western Atlantic coast from the Bay of Fundy to Long Island. All clones were grown under the same conditions and assayed in a blind test for toxin content and composition. Differences in toxin content (μmouse unit per cell) spanning two orders of magnitude were found, with decreasing toxicity from north to south. Some isolates had undetectable toxin levels. The low toxicity of southern strains of G. tamarensis may explain the historical absence of paralytic shellfish poisoning (PSP) in areas where cysts and motile cells have been reported. The cause of the observed geographic pattern is unknown, but is does suggest that there may be an environmentally-determined southern limit to the regional PSP problem.Qualitative data on the toxin composition of some clones indicate that saxitoxin, neosaxitoxin and gonyautoxins -II, -III and -IV are generally present. A more quantitative approach (i.e. one which examines each isolate for all of the 12 Gonyaulax toxins) is needed to fully utilize the potential of toxin composition in discriminating between strains.     

Nitrile,Latex, Neoprene and Vinyl Gloves: A Primary Source of Contamination for Trace Element and Zn Isotopic Analyses in Geological and Biological Samples

Exogenic contamination is of primary concern for geochemical and biological clean laboratories working with sample sizes at the nanogram or even subpicogram level. Here, we determined sixty trace elements in fifteen different types of gloves from major suppliers world‐wide to evaluate whether gloves could be potential sources of contamination for routine trace element and isotope measurements. We found that all gloves contain some trace elements that can be easily mobilised in significant amounts. In weak acid at room temperature, the tested gloves released up to 17 mg of Zn, more than 1 μg of Mg, Ti, Mn, Fe, Rb, Sr, Zr, Sn, Hf and Pb and between 100 and 1000 ng of Li, Sc, V, Cr, Ni, Cu, Ga, As, Se, Y, Ag, Ba, La, Ce, Nd, Tl and Th. Vinyl gloves released lower quantities of biologically and geologically important elements, with the exception of In and Sn. Isotopic analyses indicate that all gloves share roughly the same Zn isotopic composition (average δ⁶⁶Zn = +0.10 ± 0.32‰ (2s)). A single contact between glove and labware releases an average of ~ 6 ng of Zn and hence can significantly shift δ⁶⁶Zn above the precision level when the amount of Zn determined is below 500 ng.     

Diarrhetic shellfish poisoning in Narragansett Bay

A two-year survey for diarrhetic shellfish poisoning (DSP) was conducted in Narragansett Bay using the mouse assay method. The suspected causative organisms,Dinophysis spp., were monitored at the same time. Only one shellfish sample, in September 1984, yielded an unequivocal positive result at a time when the dinoflagellate population was dominated byD. acuminata. False positive results were suspected in May, when the mussels appeared sexually matured, and in, the summer of 1985, at the time of an unusual massive picoplanktonic bloom. Evidence of toxin production byD. acuminata was obtained from an almost monospecific sample; we calculated that over 5.4×10⁵ cells would be necessary to produce one mouse unit. The specificity and sensitivity of the assay method are questioned and improvements for DSP detection are suggested.     

Preserving Continuity of Long-Term Daily Maximum and Minimum Temperature Observations with Automation of Reference Climate Stations using Overlapping Data and Meteorological Conditions

The seasonal-by-wind bias method for aligning time series of daily maximum and minimum temperatures from past conventional staffed and new automated sites using closely collocated, overlapping observations is presented for twenty-two modernized Reference Climate Stations in Canada. The method consists of adjusting for incompatible observing times and deriving biases from the daily “manual-minus-automated” temperature differences classified into seasons and wind-speed conditions. Most of the biases vary with the season, and many show limited wind dependency. Four sets of adjusted time series are prepared based on two-year and five-year overlapping data and on seasonal bias with or without wind conditions; the adjusted data are compared with the original observations. Based on the mean of the absolute differences and examination of box plots, the results show that, for this particular set of stations, the two-year versus five-year and seasonal versus seasonal-by-wind bias adjusted time series are overall similar. The largest contribution to the improvements in the adjusted observations came from matching the times of observation. Additionally, daily temperatures are adjusted using statistical methods applied with neighbouring station data but no overlapping observations at collocated stations; it is concluded that these do not necessarily resolve the bias between staffed and automated sites.     

Impact of the Phaeocystis globosa spring bloom on the intertidal benthic compartment in the eastern English Channel: a synthesis

From 1999 to 2005, studies carried out in the frame of regional and national French programs aimed to determine whether the Phaeocystisglobosa bloom affected the intertidal benthic communities of the French coast of the eastern English Channel in terms of composition and/or functioning. Study sites were chosen to cover most of the typical shore types encountered on this coast (a rocky shore, an exposed sandy beach and a small estuary). Both the presence of active Phaeocystis cells and their degradation product (foam) did have a significant impact on the studied shores. The primary production and growth rates of the kelp Saccharina latissima decreased during the bloom because of a shortage of light and nutrient for the macroalgae. On sandy sediments, the benthic metabolism (community respiration and community primary production), as well as the nitrification rate, were enhanced during foam deposits, in relation with the presence of bacteria and active pelagic cells within the decaying colonies. In estuarine sediments, the most impressive impact was the formation of a crust at the sediment surface due to drying foam. This led to anoxic conditions in the surface sediment and resulted in a high mortality among the benthic community. Some organisms also tended to migrate upward and were then directly accessible to the higher trophic level represented by birds. Phaeocystis then created a shortcut in the estuarine trophic network. Most of these modifications lasted shortly and all the systems considered came back to their regular properties and activities a few weeks after the end of the bloom, except for the most impacted estuarine area.     

Edifice and substrata deformation induced by intrusive complexes and gravitational loading in the Mull volcano (Scotland)

It is likely that the structure of a volcanic edifice can be significantly modified by deformation caused by large, shallow intrusions. Such deformation may interact with that caused by volcano loading. We explore such intrusion-related and loading-related deformation with field evidence and analogue models. To do this we have chosen the eroded Palaeogene Mull volcano (Scotland) that had a major edifice, has well exposed intrusions and significant deformation. There are thin Mesozoic sedimentary rocks forming ductile layers below the volcano, but their thickness is insufficient to allow the gravitational spreading of the volcanic edifice, especially when considering that a thick lava pile covers them. Thus intrusive push may have been the driving force for deformation. The Mull activity migrated toward the northwest, forming three successive intrusive complexes (Centres 1, 2 and 3). Our detailed fieldwork reveals that deformation due to these was accommodated on three levels; along thrust planes in lava sequences, along a décollement located in a thin clay-rich sediment succession and in basement schists. A relative chronology has been established between different groups of structures using dyke and sill cross-cutting relationships. Centre 1 is surrounded by a fold and thrust belt leading to radial expansion. In contrast, Centre 2 and 3 are connected to thrusts located to the south and east, bounded by strike-slip faults, leading to expansion to the southeast. The migration of centres and the directed sliding of the edifice may be related to the presence to the southeast of low-resistance Dalradian basement that failed significantly during growth of Centres 2 and 3. To study the observed relationships we have carried out scaled analogue models. Models are made with fine powder intruded by a viscous magma analogue. The models show an intimate relationship between intrusion growth, uplift of the volcano and subsequent flank sliding. The structures produced can be compared with Mull and suggest that the Centre 1 thrust belt probably formed following edifice gravitational sliding as a consequence of the uplift associated with Centre 1 formation. Centre 2 and 3 are responsible for the sector sliding of the edifice flank toward the southeast as the magmatic complex became more asymmetric. The features observed at Mull and in the models are similar to those seen on active volcanoes, such as Etna, providing a structural framework for their deformation and evolution.     

Evolution of paleostress fields and brittle deformation in Hronov-Poříčí Fault Zone,Bohemian Massif

This paper investigates the tectonic history and describes the paleostress evolution of the Hronov-Po?í?í Fault Zone in the northeastern part of the Bohemian Massif. A detailed structural research has been carried out in 50 localities. Faults and fractures have been investigated and measured. An analysis of the fault-slip data within the studied area resulted in the identification of four tectonic phases. The maximum principal stress was observed to be acting NE-SW during the first and youngest phase. The trend of the horizontal compression runs at 223° in the horizontal plane perpendicular to the reverse faults occurring in this phase, as well as to the studied fault zone. The minimum principal stress was found to be subvertical dipping at 87° and trending at 358°. Both the brittle tectonic investigations and paleostress analysis have documented that, at present, the Hronov-Po?í?í Fault Zone is under compressive regime with dextral component.     

Diffusion-controlled development of silica-undersaturated domains in felsic granulites of the Bohemian Massif (Variscan belt of Central Europe)

Plagioclase rims around metastable kyanite crystals appear during decompression of high-pressure felsic granulites from the high-grade internal zone of the Bohemian Massif (Variscan belt of Central Europe). The development of the plagioclase corona is a manifestation of diffusion-driven transfer of CaO and Na₂O from the surrounding matrix and results in isolation of kyanite grains from the quartz- and K-feldspar-bearing matrix. This process establishes Si-undersaturated conditions along the plagioclase–kyanite interface, which allow crystallization of spinel during low-pressure metamorphism. The process of the plagioclase rim development is modeled thermodynamically assuming local equilibrium. The results combined with textural observations enable estimation of equilibration volume and diffusion length for Na and Ca that extends ∼400–450 and ∼450–550 μm, respectively, around each kyanite crystal. Low estimated bulk diffusion coefficients suggest that the diffusion rate of Ca and Na is controlled by low diffusivity of Al across the plagioclase rim.     

Characterization of iron and manganese species in atmospheric aerosols from anthropogenic sources

Electron paramagnetic resonance (EPR) was used to study the chemical form of iron, manganese and other paramagnetic species in airborne particles collected on southern coastal part of the North Sea, located in France. In parallel, chemical analysis was performed to obtain the metal concentrations in samples whereas an individual analysis of particles was provided by scanning electron microscopy coupled to an energy-dispersive X-ray spectrometer (SEM-EDX). EPR spectra have evidenced Fe³⁺ and Mn²⁺ ions in the form of isolated or agglomerated species, as well as carbonaceous products with variable signal intensities according to the wind direction. The monitoring of a signal of isolated Mn²⁺ ions on a distance close to 90 km was proposed as tracer of particles from a Mn local emission source. Fe³⁺ signals are relative to agglomerated species and differences in the type of interaction between these species were evidenced following the wind direction. Fe³⁺ EPR signals parameters revealing antiferromagnetic contribution in Fe-rich particles were found for an industrial origin at Dunkerque.