Control of paths of quaternary volcanic products in western Bohemian Massif by rejuvenated Variscan triple junction of ancient microplates

Our objective is to look for deep paths of Cenozoic volcanism and migration routes of active mantle volatiles through the lithosphere of the western Bohemian Massif. We show that the rejuvenated junction of three mantle domains, delimited by different orientation of seismic anisotropy and belonging to originally separated microplates — the Saxothuringian (ST), Moldanubian (MD) and Teplá-Barrandian (TB) — can provide the easiest upward routes of fluids through the deep lithosphere. Geographic distribution of mantle-fluid escapes at the surface suggests fluid migration through the ductile lower crust and through partly open faults in the rigid upper crust, which is locally detached and shifted from its lower part and from the mantle lithosphere. Present-day escapes of mantle-derived helium and CO₂ concentrate mainly in two tectonically different crust edifices — in the Cheb Basin (CHB) and in an allochtonous block called the Mariánské Lázně Complex (MLC). Crystalline basement of the CHB developed above the Variscan ‘triple junction’ of the mantle lithosphere domains. The basement was extended during the Cenozoic and dissected by systems of faults into small partly sunken blocks. Thanks to buoyancy the mantle fluids migrate upwards along the lithosphere junction into the faulted basement of the CHB. The highest CO₂ flow and the highest ³He/⁴He ratios are observed at intersections of major normal faults and along the southern boundary of the Smrčiny (Fichtelgebirge) granite Pluton. The fluid escapes are separated from the earthquake swarm epicentres. Routes of the fluids to the MLC are longer and more complicated. Surface escapes tap the mantle fluids mainly from the Mariánské Lázně Fault (MLF) and from the tectonic boundaries along which the MLC block of the TB lower crust was thrust over the ST complexes. Hypocentres of earthquake swarms of the two major focal areas at Novy Kostel and Lazy, located mainly at depths of 6–13 km, reside either in granite or in underlying gneiss, while the escapes of mantle fluids follow major faults or boundaries of crystalline units outside the Smrčiny and Karlovy Vary granite Plutons. We suggest that primarily those parts of faults in the upper crust, which is strengthened by granite magmatism and rigid enough to selectively accumulate stresses, are seismoactive. On the other hand, other parts of the faults tapping ascending mantle volatiles are ‘lubricated’ by the fluids and secondary mineralogical changes, and thus they cannot accumulate sufficient stresses to be released by earthquakes. A comparison of the most probable paths of the mantle fluids with the space-time distribution of the Novy Kostel hypocentres does not seem to support the model of the earthquake swarms triggered by pressurized fluids of mantle origin.     

Comparison of the anisotropic-ray-theory rays and anisotropic common S-wave rays with the SH and SV reference rays in a velocity model with a split intersection singularity

We describe the behaviour of the anisotropic–ray–theory S–wave rays in a velocity model with a split intersection singularity. The anisotropic–ray–theory S–wave rays crossing the split intersection singularity are smoothly but very sharply bent. While the initial–value rays can be safely traced by solving Hamilton’s equations of rays, it is often impossible to determine the coefficients of the equations of geodesic deviation (paraxial ray equations, dynamic ray tracing equations) and to solve them numerically. As a result, we often know neither the matrix of geometrical spreading, nor the phase shift due to caustics. We demonstrate the abrupt changes of the geometrical spreading and wavefront curvature of the fast anisotropic–ray–theory S wave. We also demonstrate the formation of caustics and wavefront triplication of the slow anisotropic–ray–theory S wave.Since the actual S waves propagate approximately along the SH and SV reference rays in this velocity model, we compare the anisotropic–ray–theory S–wave rays with the SH and SV reference rays. Since the coupling ray theory is usually calculated along the anisotropic common S–wave rays, we also compare the anisotropic common S–wave rays with the SH and SV reference rays.     

Extreme precipitation and long-term precipitation changes in a Central European sedge-grass marsh in the context of flood occurrence

This study offers a detailed analysis of the extreme precipitation and long-term precipitation changes in a sedge-grass marsh in the “Wet Meadows” area in the Czech Republic (Central Europe) in the context of flood occurrence. Namely, trends in annual maxima of daily precipitation and trends in the occurrence and amount of rainfall are investigated. The analysis is based on daily measurements of precipitation from 1977 to 2015. We found out that extreme precipitation has become significantly more frequent in recent years, and there are also other significant changes in the rainfall distribution. Possible negative effects on the wetland can be linked to a change of carbon exchange between the ecosystem and the atmosphere and a change of biodiversity. Awareness of these changes is necessary for possible positive human intervention when a desirable wetland functioning is threatened.     

Role of single-domain magnetic particles in creation of inverse magnetic fabrics in volcanic rocks: A mathematical model study

The role of single-domain (SD) magnetic particles in creation of inverse magnetic fabrics is investigated on simple mathematical models using a realistic estimate for SD intrinsic susceptibility. In contrast to the fraction created by multi-domain (MD) particles, in which the anisotropy of magnetic susceptibility (AMS) is controlled by both the grain AMS and intensity of the preferred orientation of the particles, the AMS of the SD fraction is controlled solely by the intensity of the preferred orientation. The degree of AMS of ensemble of SD grains with a preferred orientation is therefore much higher than that of the same ensemble of MD particles implying the existence of frequent inverse magnetic fabrics. However, the occurrence of inverse magnetic fabrics due to SD particles is more the exception than the rule. Consequently, the amounts of SD particles is probably in general low. Nevertheless, the presence of SD particles in amounts insufficient to create inverse magnetic fabrics may diminish the whole rock AMS substantially. This can be one of the reasons for relatively low AMS in volcanic rocks whose magnetic particles may be really small obeying the conditions for the existence of SD particles.     

Laboratory study of the effect of temperature difference on the disintegration of redbed softrock

To explore the impact of temperature difference (TD) on the disintegration of redbed softrock, three types of redbed rock, collected from Nanxiong Basin, were analyzed under three different treatments: TD, wetting and drying (WD), and TDWD-temperature difference and WD. To better understand the influence of different ranges of TD on disintegration during WD cycles, pH (hydrogen ion concentration) values, electrical conductivity (EC) values, and concentration of cations in leachate released during treatment were measured. The results show that no significant change can be observed under single TD treatment but that TD can increase the disintegration rate by accelerating the water–rock interaction. The effect of TD is more significant for rock with weak resistance to disintegration.     

The Impact of Global/Local Bias on Task-Solving in Map-Related Tasks Employing Extrinsic and Intrinsic Visualization of Risk Uncertainty Maps

The form of visual representation affects both the way in which the visual representation is processed and the effectiveness of this processing. Different forms of visual representation may require the employment of different cognitive strategies in order to solve a particular task; at the same time, the different representations vary as to the extent to which they correspond with an individual’s preferred cognitive style. The present study employed a Navon-type task to learn about the occurrence of global/local bias. The research was based on close interdisciplinary cooperation between the domains of both psychology and cartography. Several different types of tasks were made involving avalanche hazard maps with intrinsic/extrinsic visual representations, each of them employing different types of graphic variables representing the level of avalanche hazard and avalanche hazard uncertainty. The research sample consisted of two groups of participants, each of which was provided with a different form of visual representation of identical geographical data, such that the representations could be regarded as ‘informationally equivalent’. The first phase of the research consisted of two correlation studies, the first involving subjects with a high degree of map literacy (students of cartography) (intrinsic method: N?=?35; extrinsic method: N?=?37). The second study was performed after the results of the first study were analyzed. The second group of participants consisted of subjects with a low expected degree of map literacy (students of psychology; intrinsic method: N?=?35; extrinsic method: N?=?27).The first study revealed a statistically significant moderate correlation between the students’ response times in extrinsic visualization tasks and their response times in a global subtest (r?=?0.384, p?<?0.05); likewise, a statistically significant moderate correlation was found between the students’ response times in intrinsic visualization tasks and their response times in the local subtest (r?=?0.387, p?<?0.05). At the same time, no correlation was found between the students’ performance in the local subtest and their performance in extrinsic visualization tasks, or between their scores in the global subtest and their performance in intrinsic visualization tasks. The second correlation study did not confirm the results of the first correlation study (intrinsic visualization/‘small figures test’: r?=?0.221; extrinsic visualization/‘large figures test’: r?=?0.135). The first phase of the research, where the data was subjected to statistical analysis, was followed by a comparative eye-tracking study, whose aim was to provide more detailed insight into the cognitive strategies employed when solving map-related tasks. More specifically, the eye-tracking study was expected to be able to detect possible differences between the cognitive patterns employed when solving extrinsic- as opposed to intrinsic visualization tasks. The results of an exploratory eye-tracking data analysis support the hypothesis of different strategies of visual information processing being used in reaction to different types of visualization.     

Geoidal Geopotential and World Height System

The geoidal geopotential value of W ₀ = 62 636 856.0 ± 0.5m ² s ^–2 , determined from the 1993 –1998 TOPEX/POSEIDON altimeter data, can be used to practically define and realize the World Height System. The W ₀ -value can also uniquely define the geoidal surface and is required for a number of applications, including General Relativity in precise time keeping and time definitions. Furthermore, the W ₀ -value provides a scale parameter for the Earth that is independent of the tidal reference system. All of the above qualities make the geoidal potential W ₀ ideally suited for official adoption as one of the fundamental constants, replacing the currently adopted semi-major axis a of the mean Earth ellipsoid. Vertical shifts of the Local Vertical Datum (LVD) origins can easily be determined with respect to the World Height System (defined by W ₀ ), in using the recent EGM96 gravity model and ellipsoidal height observations (e.g. GPS) at levelling points. Using this methodology the LVD vertical displacements for the NAVD88 (North American Vertical Datum 88), NAP (Normaal Amsterdams Peil), AMD (Australian Height Datum), KHD (Kronstadt Height Datum), and N60 (Finnish Height Datum) were determined with respect to the proposed World Height System as follows: –55.1 cm, –11.0 cm, +42.4 cm, –11.1 cm and +1.8 cm, respectively.     

Surface-sediment and epilithic diatom pH calibration sets for remote European mountain lakes (AL:PE Project) and their comparison with the Surface Waters Acidification Programme (SWAP) calibration set

A modern diatom-pH calibration data-set consisting of surface-sediment diatom assemblages from 118 lakes and 530 taxa is presented. The AL:PE data-set is from high-altitude or high-latitude lakes in the Alps, Norway, Svalbard, Kola Peninsula, UK, Slovenia, Slovakia, Poland, Portugal, and Spain (pH range = 4.5-8.0; DOC range = 0.2-3.2 mg l^-1). In addition, 92 epilithon samples from 22 high-altitude or high-latitude lakes comprise an AL:PE epilithon diatom-pH data-set. Weighted averaging partial least squares regression is used to develop pH-inference models. The AL:PE data-set has a root-mean-square-error of prediction (RMSEP) of 0.33 and a maximum bias of 0.36 pH units and r² of 0.82, as assessed by leave-one-out cross-validation. The epilithon data-set has, after data-screening and the deletion of one very obvious outlier, a RMSEP of 0.23 and a maximum bias of 0.18 pH units and r² of 0.88. The 167 sample SWAP diatom-pH data-set from lowland or upland lakes in the UK, Norway, and Sweden has a RMSEP of 0.29 and a maximum bias of 0.23 pH units and r² of 0.86.The pH optima, as estimated by weighted averaging and Gaussian regression, are compared for the three data-sets (AL:PE, SWAP, AL:PE epilithon). There is a good correspondence between the AL:PE and the AL:PE epilithon optima, but a consistent bias between the AL:PE and SWAP optima, with the SWAP optima being lower than the AL:PE estimates.The predictive performances of the AL:PE and SWAP calibration data-sets are compared using independent test samples and six core sequences, all from high-altitude lakes, one in south-east Siberia and five in eastern Scotland. The results show the importance of using the AL:PE data-set for inferring lake-water pH from diatom assemblages in high-altitude or high latitude lakes with low DOC concentrations.     

Temporary Array Data for Studying Seismic Anisotropy of Variscan Massifs – The Armorican Massif,French Massif Central And Bohemian Massif

We present the first results of a comparison of deep lithosphere structure of three Variscan massifs - the Armorican Massif, French Massif Central and Bohemian Massif, as revealed by recent tomographic studies of seismic anisotropy. The data originate from several field measurements made in temporary arrays of stations equipped with both short-period and broadband seismometers with digital recording. The study is based on teleseismic body waves and a joint inversion of anisotropic data (P-residual spheres, the fast shear-wave polarizations and split times) and demonstrates that the three Variscan massifs appear to consist of at least two parts with different orientation of large-scale fabric derived from seismic anisotropy. The boundaries of anisotropic lithospheric domains are related to prominent tectonic features recognised on the surface as sutures, shear zones or transfer fault zones, as well as grabens, thus indicating that some of them extend deep through the entire lithosphere.