Vol 483, No 2 (2018)

Based on geochronological data, it is shown that the formation of sediments of a 50–80 m terrace of Lake Baikal occurred during the Middle Pleistocene and its top part was formed in the Late Pleistocene. This conclusion is confirmed by polychronous burials of mammals related to the early and late mammoth faunal complexes: Canis, Mammuthus, Equus, Coelodonta, Cervus, Capreolus, and Bison.

The Sakmara Allochthon (Southern Urals) comprises a widely distributed folded stratum of rhyolites and ignimbrites, which are characterized by Nb–Zr–REE geochemical specification. This stratum overlies unconformably folded Paleozoic complexes, including Devonian ones. Rhyolites contain potassium feldspar and quartz phenocrysts, as well as granite xenoliths. According to geochemical features, volcaniс rocks were formed under the intraplate setting; in terms of the chemical composition, they belong to the A-type granites. The ⁴⁰Ar/³⁹Ar age of the felsic rock groundmass of rhyolites is 303 ± 2 Ma. The feldspar phenocrysts yielded ages of 306 ± 3 and 337 ± 3 Ma. The first estimate, as well as the matrix age, is associated with the formation of the volcanic complex, while the second value is probably associated with the age of xenogenic material. The complex of rare-metal enriched rhyolites characterizes the stage of the terminal Late Carboniferous rift magmatism in the rear part of the active continental margin. This complex formed prior to collision and thrusting of ophiolitic allochthons.

The results of isotope U–Pb dating of zircons from lherzolite and vein olivine orthopyroxenite composing the Roseta ultramafic massif are presented. The zircons differ in their morphological, optical, and geochemical properties and in their age. Lherzolite samples that are almost deprived of cathodoluminescence are represented by two age clusters 788 ± 15 and 638.2 ± 5.4 Ma. The zircons from the first cluster are relict. A later event recorded in the zircons from the second cluster was manifested in an intense metamict mineral transformation. The age of the zircons from vein olivine orthopyroxenite conforms to 608.9 ± 3.4 Ma. These zircons are considered to be syngenetic; therefore, their age is determined by the time of crystallization of olivine orthopyroxenites.

Laboratory experiments were conducted in a hermetically sealed growth chamber with two soil samples obtained from the arctic tundra zone with different levels of moisture. Samples were maintained at a growing season typical of the region from which they were taken, and for the sample with a high level of moisture it was made twice: with the temperature in accord with natural conditions and one increased by 2°C. It has been shown that heating of the overmoistened tundra soil by 2°C can increased the average carbon dioxide emissions by almost two times (from 75 to 100–150 mg m^–2 h^–1). Upon the application of heat, no significant increase in methane emission was observed.

The S isotope composition of single sulfide grains was studied taking into account the sequence of their formation in samples from the sulfide structures of hydrothermal fields confined to the Mid-Atlantic Ridge. The ranges of δ³⁴S values obtained for the structures of the Logachev, Krasnov, and Rainbow fields are the following (‰): from +3.9 to +6, from +7.1 to +9.8, and from +2.1 to +8.4, respectively. Sulfides of later generations within each of these fields are regularly enriched in the ³⁴S isotope relative to sulfides of earlier generations. Here, the S isotope composition does not depend on the composition and structure of the mineral. The data obtained show that in the sulfide generation zone, where seawater sulfate reduction takes place, the system is closed relatively to fluid. This leads to an increase in δ³⁴S values of reduced sulfur compounds in the hydrothermal fluid and to sulfides being crystallized.

The distribution of REEs and rare metals in the Paleocene and Lower–Middle Miocene brown coals of the Zeya–Bureya Basin is analyzed. The migration of minor elements on the NW flank of the basin (the Sergeevskoe deposit), in the mode of the static state of orogens in the Paleocene and Miocene, in the course of active expansion of the sedimentation area occurred with uniform development of denudation plains and with the steady processes of peat accumulation. The high dynamic activity of the region on the SE margin of the Zeya–Bureya Basin (the Yerkovetskoe deposit) provided contrasting forms of coupling in the flexure–uplift system and an uneven character of localization of ore components. It is shown that coals of the Sergeevskoye deposit are enriched in Be, Sc, V, Ga, Rb, Nb, Ta, and REE + Y and may be considered as a promising complex rare-metal raw material.

This paper reports the data obtained on the anomalous train of soliton-like internal record-high waves in the Black Sea (h = ~16 m). Such a train was detected at a depth of ~30 m in October 2015 on the shelf near Gelendzhik with the use of an acoustic Doppler current profiler and a chain of thermistors and by processing of a space radar image obtained from the SENTINEL-1A satellite. The intensive atmospheric front revealed by meteorological data generated such internal waves, which are anomalous for the Black Sea.

This paper reports on the seasonal changes in the regimes of mineralization in the Don delta. This study was based on the database of the automatic hydrometeorological stations located in the Don delta and on the pre-estuarine coastal waters of Taganrog Bay. The ionic composition of the water samples showed that the ratio of the groundwater flow increases during cold seasons in the girlos connecting the delta channels of the Don and Kagalnik rivers. The ingress of less mineralized waters from the Don River almost ceases during the negative surges, and stream flows are filled with saline groundwater. This is another consequence of the water scarcity in the Don River Basin.

The spatial structure, interannual variability, and pathways of the Labrador Sea water (LSW) in the Irminger Sea were analyzed during period of deep convection in 2014–2017. Four regions of the LSW were distinguished, that characterized by different thermohaline properties and dissolved oxygen saturation. The regions showed synchronous variability and complied with the main circulation (the Irminger Current, Irminger Gyre, and the western boundary current system including the recirculation of the Irminger Current). The flowing-out LSW from the Irminger Sea is warmer by 0.17°C and more saline by 0.02 PSU than the flowing-in waters because of the mixing with the Irminger Current.

This work is devoted to the problems of elaboration of the instrumental basis for low-frequency sensing of ambient noise of the ocean. The experimental data of testing of the technical parameters of a molecular-electronic hydrophone are given. The amplitude-frequency and noise parameters of prototypes have been studied. The operation of a hydrophone with a frequency range of 0.02–200 Hz and sensitivity of 0.75 mV/Pa is described. Ambient noise was measured with the use of correlation analysis.

The results of 20 years of field data (1963–1982) and 50 years of remote observations (1963–2012) on Medvezhy Glacier in the Pamirs by the Institute of Geography, Russian Academy of Sciences, are considered. The prevalence of the influence of climatic factors over internal ones (features of ice deformation) on glacial surges is shown. A conclusion is made about the uniqueness of the surge regime of Medvezhy Glacier connected with the structure of its bed. There are no analogues of this structure of the bed on any of the 82 surging glaciers in the Pamirs.

On the basis of three methods, the current seismic situation in the zone of the Central Sakhalin Fault is assessed and the scenarios of its development are predicted. It is shown that beginning from early 2017 seismic activity considerably increased in comparison with previous years. It is determined that there is a very high probability of occurrence of an earthquake with possible magnitude М_w = 5–6 in the area studied in the period until August–November 2018 (the former date is by the LURR method; the latter, by the SDP method). This forecast continues the series of strong earthquakes in Sakhalin—Onor (August 14, 2016, М_w = 5.8) and Shebunino (April 23, 2017, М_w = 5.3)—which occurred with the onset of the period of deceleration of the Earth’s rotation rate.