Postglacial relative sea-level change and stratigraphy of raised coastal basins on Kola Peninsula, northwest Russia

A relative sea-level curve for the Holocene is constructed for Polyarny on the Kola Peninsula, northwest Russia. The curve is based on 18 radiocarbon dates of isolation contacts, identified from lithological and diatomological criteria, in nine lake basins situated between 12 and 57 m a.s.l. Most of the lakes show a conformable, regressive I–II–III (marine–transitional–freshwater) facies succession, indicating a postglacial history comprising an early (10,000–9000 radiocarbon years BP) phase of rapid, glacio-isostatically induced emergence (5 cm year⁻¹) and a later phase (after 7000 years BP,) having a moderate rate of emergence (<0.5 cm year⁻¹). Three lakes together record a phase of very low rate of emergence or slight sea-level rise at a level of 27 m a.s.l., between 8500 and 7000 years BP, which correlates with the regional Tapes transgression. Pollen stratigraphy in the highest lake shows that the area was deglaciated before the Younger Dryas and that previously reconstructed Younger Dryas glacier margins along the north Kola coast lie too far north.     

X-Ray radial distribution function analysis of acid volcanic glasses from the Eastern Rhodopes,Bulgaria

Five natural acid volcanic glasses (perlites) from the Eastern Rhodope mountains, Bulgaria, have been studied by X-ray diffraction. The quantity of the microlites varies from 1–3.5 weight percent. It is higher in the glasses from the rhyolite-perlite transition zone. Total pair correlation functions have been calculated for three of the glasses with less than 2 weight percent microlites. All total pair correlation functions are quite similar and have six well defined peaks up to 8 Å. Beyond 8 Å they are practically featureless. The general form of the curves and peak positions suggests that the short-range order in all the three glasses is compatible with a 6-membered tetrahedral ring polymerization scheme with some contribution of fourmembered rings. The T-01 (T=Si, Al) distance shows linear correlation with the weight percent ratio Al₂O₃/SiO₂. The averaged first nearest neighbour distances T-01, O-01 and T-T1 are 1.615±0.005 Å, 2.66±0.02 Å and 3.16±0.02 Å, respectively. The mean T-O-T bond angle is 157±4°. Energy minimization and topology considerations of the possible distribution of different tetrahedral rings are discussed.     

Kelvin–Helmholtz Instability in a Cool Solar Jet in the Framework of Hall Magnetohydrodynamics: A Case Study

We investigate the conditions under which the magnetohydrodynamic (MHD) modes in a cylindrical magnetic flux tube moving along its axis become unstable against the Kelvin–Helmholtz (KH) instability. We use the dispersion relations of MHD modes obtained from the linearized Hall MHD equations for cool (zero beta) plasma by assuming real wave numbers and complex angular wave frequencies/complex wave phase velocities. The dispersion equations are solved numerically at fixed input parameters and varying values of the ratio \(l_{\mathrm{Hall}}/a\), where \(l_{\mathrm{Hall}} = c/\omega_{\mathrm{pi}}\) (\(c\) being the speed of light, and \(\omega_{\mathrm{pi}}\) the ion plasma frequency) and \(a\) is the flux tube radius. It is shown that the stability of the MHD modes depends upon four parameters: the density contrast between the flux tube and its environment, the ratio of external and internal magnetic fields, the ratio \(l_{\mathrm{Hall}}/a\), and the value of the Alfvén Mach number defined as the ratio of the tube axial velocity to Alfvén speed inside the flux tube. It is found that at high density contrasts, for small values of \(l_{\mathrm{Hall}}/a\), the kink (\(m = 1\)) mode can become unstable against KH instability at some critical Alfvén Mach number (or equivalently at critical flow speed), but a threshold \(l_{\mathrm{Hall}}/a\) can suppress the onset of the KH instability. At small density contrasts, however, the magnitude of \(l_{\mathrm{Hall}}/a\) does not affect noticeably the condition for instability occurrence – even though it can reduce the critical Alfvén Mach number. It is established that the sausage mode (\(m = 0\)) is not subject to the KH instability.     

The Character and Formation of Elongated Depressions on the Upper Bulgarian Slope

Seafloor elongated depressions are indicators of gas seepage or slope instability. Here we report a sequence of slopeparallel elongated depressions that link to headwalls of sediment slides on upper slope. The depressions of about 250 m in width and several kilometers in length are areas of focused gas discharge indicated by bubble-release into the water column and methane enriched pore waters. Sparker seismic profiles running perpendicular and parallel to the coast, show gas migration pathways and trapped gas underneath these depressions with bright spots and seismic blanking. The data indicate that upward gas migration is the initial reason for fracturing sedimentary layers. In the top sediment where two young stages of landslides can be detected, the slopeparallel sediment weakening lengthens and deepens the surficial fractures, creating the elongated depressions in the seafloor supported by sediment erosion due to slope-parallel water currents.     

Holocenic Geological and Seismic Activity of the Fault System in Northeastern Bulgaria by the Complex of Geological-Geomorphological and Archeoseismological Methods

Izvestiya, Atmospheric and Oceanic Physics - The structure of the fault system of northeastern Bulgaria and, in particular, of the Intramoesian fault, is examined in order to assess their current...     

Light‐curve solutions of 20 ecipsing Kepler binaries,most of them with pronounced spot and flare activity

We carried out light curve solutions of the Kepler light curves of twenty detached eclipsing binaries with circular orbits and determined the orbital inclinations, temperatures. relative radii and luminosities of their components. We studied the quality of the solutions with respect to the adopted limb‐darkening law and its coefficients. The detailed tracing of the numerous and uninterrupted data of our targets gave us an unique possibility to detect and learn their spot and flare activity. We established that the out‐of‐eclipse variability of the most targets gradually changes from small‐amplitude two‐waved type to big‐amplitude one‐waved type and vice versa, i.e. their spot activity cycles pass through phase of two almost diametrically opposite spots and phase of big polar cool spot. We found that the low‐temperature targets show flare activity of UV Cet‐type with amplitudes of 0.002–0.22 mag and duration of up to several hours. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Soil aggregation estimates in CZO-Fuchsenbigl

The study presents results on the informativity and spatial variation of soil aggregation characteristics in one of the Critical Zone Observatories (CZO) in Europe – Fuchsenbigl, Austria. Water stable aggregates of different size were measured, and strong relationships between soil aggregation estimates were found. The horizontal variation of water stable aggregates at particular depths can be explained by certain vertical heterogeneity of the soil profiles in space. The water stable aggregates in 1–3 mm size dry aggregates in the upper layer vary from 44% to 76% under native vegetation, drop to 1% under intensive cultivation, and comprise 19% in land not tilled for 5 years. The results allow linking the characteristics of soil structure with other biotic and chemical properties for better estimation of the driving forces for soil aggregate formation.     

Mud volcanoes—a significant source of atmospheric methane

Mud volcanoes are recognized as a significant geological source of atmospheric carbon, particularly as methane gas. This paper considers the total number of mud volcanoes, types and frequency of their activity, quantities of emissions during quiescence and eruption, and composition of venting gases. Mud volcanoes approximate 1,950 prominent individuals worldwide and about 60 to 65 erupt every year. They sporadically or continuously emit to the atmosphere considerable volumes of gas, mainly methane, in average volumes of 3.3 to 3.6×10⁶ m³ per year during quiescent periods, and about 12×10⁶ m³ to more than 350×10⁶ m³ per single eruption. The total annual amount of methane emitted to the atmosphere through mud volcanoes is estimated to be about 5 Tg, containing almost equal quantities of fossil and modern carbon.     

Titan's aerosols: Comparison between our model and DISR findings

Our model [Dimitrov, V., Bar-Nun, A., 1999. A model of energy dependent agglomeration of hydrocarbon aerosol particles and implication to Titan's aerosol. J. Aerosol. Sci. 30(1), 35-49] describes the experimentally found polymerization of C₂H₂ and HCN to form aerosol embryos, their growth and adherence to form various aerosols objects [Bar-Nun, A., Kleinfeld, I., Ganor, E., 1988. Shape and optical properties of aerosols formed by photolysis of C₂H₂, C₂H₄ and HCN. J. Geophys. Res. 93, 8383-8387]. These loose fractal objects describe well the findings of DISR on the Huygens probe [Tomasko, M.G., Bézard, B., Doose, L., Engel, S., Karkoschka, E., 2008. Measurements of methane absorption by the descent imager/spectral radiometer (DISR) during its descent through Titan's atmosphere. Planet. Space Sci., this issue, doi:10.1016/j.pss.2007]. These include (1) various regular objects of R=(0.035-0.064)×10⁻⁶ m, as compared with DISR's 0.05×10⁻⁶ m; (2) diverse low and high fractal structures composed of random combinations of various regular and irregular objects; (3) the number density of fractal particles is 6.9×10⁶ m⁻³ at Z=100 km, as compared with DISR's finding of 5.0×10⁶ m⁻³ at Z=80 km; (4) the number of structural units per higher fractals in the atmosphere at Z∼100 km is (2400-2700), as compared with DISR's 3000, and their size being of R=(5.4-6.4)×10⁻⁶ m will satisfy this value and (5) condensation of CH₄ on the highly fractal structures could begin at the altitude where thin methane clouds were observed, filling somewhat the new open fractal structures.