The changes in the electric conductivity of the lithosphere in the source region of the strongest Olyutora earthquake in the Koryak highlands

The results of the magnetotelluric (MT) soundings before and after an earthquake are analyzed. The interpretation is based on the longitudinal and transverse MT curves (along and across the strike of the main tectonic elements, respectively). The MT curves are distorted by the ρ- and coast effect. The distortions due to the coast effect are estimated by the testing three-dimensional (3D) model. It is established that the coast effect distortion at the periods up to 1000 s is small and can be disregarded. The divergence of the longitudinal and transverse MT curves, which points to the presence of the deep faults, is thoroughly studied. The inversion of the MTsounding curves is carried out by the REBOCC program of the numerical two-dimensional modeling. This program implements the procedures of elimination of the ρ-effect and the joint inversion of the longitudinal and transverse MT sounding curves. The obtained geoelectrical cross sections provide an insight into the structure of electrical conductivity of the lithosphere before and after the earthquake. The more intense variations in the electric conductivity are observed in the zone of the deep faults. These variations are related to the changes in the porosity and saturation of the rocks by the highly mineralized fluids.     

On the probability of cryogenic mud volcanism on Titan

Juxtaposing images of the surface of Titan made by the Huygens probe and photos of the mud volcano region on Earth (the Taman peninsula, the Caucasus) reveals similar geomorphologic features. This has led us to suggest the existence of cryogenic mud-volcanic activity on Titan. The role of liquid methane in supporting this process on Titan can be the same as that of gaseous methane on Earth. For Titan, gas hydrates (hydrates of hydrocarbon gases) and water ice are analogs of terrestrial clay breccia. Note that gas hydrates are stable at P-T conditions typical of Titan. Assuming the existence of mud-volcanic activity on Titan allows us to explain: (i) the general view of the landscape near the Huygens probe landing site, (ii) the chains of bright “islets” noticed during the probe descent, which may be a marker of a tectonic fault line, (iii) the conic shape of the hill in the foreground of the image taken from an altitude of 8 km, (iv) the rounded pebble-like shape of the small solid blocks on the surface of Titan, and (v) the presence of long white strips, each of which seems to diverge at one of the ends (such a picture can be produced by methane wind carrying away the ejecta of a gaseous volcano from its crater).     

Magnetotelluric dispersion relations in a two-dimensional model of the coastal effect

Numerical modeling is performed for seafloor magnetotelluric sounding in a 2-D offshore zone in a period range of 0.25–16 h. An anomaly of the seafloor longitudinal impedance observed at distances of 20–260 km from the shore is analyzed. Dispersion relations are violated for the longitudinal impedance within the anomalous zone.     

“Sub-Triticites Beds” of the Donskaya Luka and lower boundary of the Kasimovian Stage

Micro- and macrofauna remains were studied from transitional deposits of Moscovian and Kasimovian Stages in the Donskaya Luka (Volgograd Region). The preliminary analysis of microfauna showed that “sub-Triticites Beds” of the Donskaya Luka contain fusulinid and conodont assemblages enabling correlation of the Middle and Upper Carboniferous deposits in the study region with the type sections of Moscow area and Donbass. Conodonts from the “sub-Triticites Beds” stratotype were studied for the first time. As is established, upper part of the Sukhov Fm. and the base of the Seleznev Fm. belong to the Protriticites pseudomontiparus-Obsoletes obsoletus Zone. Based on fusulinids, higher parts of the Seleznev Fm. belong to the Montiparus Zone of the Khamovnikian Substage, whereas conodonts suggest their correlation with lower part of the Khamovnikian Substage, i.e., with the Ratmirovo Fm. or a basal part of the Neverovo Fm. Middle part of the Seleznev Fm. is correlated to middle cycle of the Neverovo Fm. of the Khamovnikian Substage in Moscow area. The Middle-Upper Carboniferous boundary deposits of the Donskaya Luka are represented by deposits of extremely shallow-water settings and contain only sporadic microfauna. These sections cannot be considered as possible candidates for the GSSP of the Kasimovian Stage base.     

The Vendian age of granodiorites and plagiogranites of the Tallainskii complex (Baikal–Muya Belt): U–Pb isotope data

This work presents the results of U–Pb isotope dating of zircons from granodiorites and plagiogranites of the Tallainskii gabbro–granodiorite–plagiogranite complex of the Karalon–Mamakan zone of the Baikal–Muya belt, ascribed to the Tallainskii pluton. The age datings obtained for granodiorite of the Eleninskii massif (605 ± 6 Ma) and plagiogranite of the Ust-Berezovo massif (609 ± 6 Ma) are in close agreement within the limits of error. Taking into account previously published data, the emplacement of the Tallainskii complex occurred within the age interval of 615–603 Ma in connection with postcollision extension. The “island arc” geochemical characteristics of granodiorites and plagiogranites can be explained by magmatic differentiation and (or) participation in the formation of a melt source enriched in the suprasubduction component involved in petrogenesis during the preceding Neoproterozoic period.     

Investigation of Transformations of the Local Regions of Pollution in the Northwest Part of the Black Sea Caused by the Motion of a Cyclone

By the method of mathematical simulation, we study the evolution of local discharges of pollutants on the northwest shelf of the Black Sea induced by the motion of a cyclone. We use the nonlinear equations of motion of a homogeneous viscous fluid in the hydrostatic approximation and the equation of turbulent diffusion. A cyclonic formation is represented by a moving axisymmetric area of low pressures. The discharges of pollutants are caused by the action of instantaneous sources located on the sea surface. We perform the analysis of dependences of the paths of motion of polluted regions, the periods of their dissipation, and the depths of penetration of pollutants on the bottom topography and the intensity of diffusion processes. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 17–27, November–December, 2005.     

Propagation of passive impurities in the northwest part of the Black Sea under the action of cyclones moving to the north

We perform the theoretical analysis of the turbulent diffusion of impurities in the sea in the presence of long waves. The role of generators of long-wave motions is played by moving cyclonic baric formations. At the initial time, the zone of pollution is specified in the form of a spot of a passive substance localized near the Karkinitskii Bay in the Black Sea. The results of our investigations enable us to estimate the contribution of long waves to the process of diffusion of the spot of impurity depending on the trajectory of motion of the cyclonic formation. It is shown that, under the action of waves induced by the cyclone, the maximum concentration in the spot decreases more rapidly only for a certain period of time. Moreover, we observe a northwest displacement of the spot specified by the structure of the wave field.Translated from Morskoi Gidrofizicheskii Zhurnal, No. 4, pp. 3–18, July–August, 2004.     

Investigation of the fields of concentration of the suspension on the northwest shelf of the Black Sea in the case of roiling of the bottom sediments by a moving cyclone

The processes of roiling of the bottom sediments, diffusion transport of the suspension, and its repeated sedimentation on the northwest shelf of the Black Sea caused by a moving cyclone are studied by using a numerical sigma-coordinate model. It is supposed that bottom sediments are formed by particles of the same type. We determine the regions of the most intense rise of the suspension, directions of its transport by the flows of water, and the vertical profiles of concentration of suspended bottom sediments in different regions. In particular, it is shown that the distribution of suspended substances at a distance of 1 m from the bottom reflects the location of the active and inactive centers of erosion. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 3–20, January–February, 2007.     

Middle Jurassic continental biota and paleolandscape in the Dubinino locality (Sharypovo area,Krasnoyarsk krai)

On the basis of the lithological-facies analysis, it was established that deposits of the Upper Itat Subformation, comprising the Dubinino locality of the Middle Jurassic flora and insects (Sharypovo district, Krasnoyarsk krai), accumulated in alluvial and lacustrine and, to a lesser extent, floodplain environments (floodplain and alluvial fan facies). The occurrence of remains of insects, macroremains of flora, spores, and pollen allowed us to make a paleoreconstruction of an area with a strongly dissected relief: continental fresh-water reservoir (lake) with varying degree of overflow, surrounded by hills covered with gymnospermous and ginkgo forests.