Vol 488, No 2 (2019)

This paper reports recently obtained research data on active faults in the Kerch Peninsula. The compiled Map of Active Faults demonstrates foci of Late Holocene strong earthquakes. This map is a regional seismotectonic model of strong earthquake foci, and a detailed basis for prediction of spatial seismic hazards. According to the research results, the Kerch Peninsula is characterized by the features of classical morphostructures, while the morphology of recent peninsula contours is caused by large active fault zones.

The mollusk species Watsonella crosbyi Grabau, 1900 was found among other mollusks in the Lower Botomian strata of the Xinji Formation on the Northern China Platform (Shaanxi Province). Taxonomically the mollusk assemblage is extremely similar to that from the Mernmerna Formation, Parara Limestone, and Sellick Hill Formation of Southern Australia, the Bastion Formation of Laurentia, and the uppermost Emyaksin Formation of the Siberian Platform. All these strata can be aged as Early Botomian. The new finding of Watsonella crosbyi confirms the significant time range of the species distribution (Tommotian–Botomian) and raises doubts about newly proposed correlations of the Lower Cambrian of Southern Australia making the previously determined age of the formations one or even two ages older.

New dates of detrital zircons from sandstones expand the possibilities to interpret their source areas. These interpretations are often constrained by a formal comparison of the geochronological and compositional features of detrital crystals with any very remote complexes. However, there is another situation when the local complexes pretend to be a source of detrital material. Analyses of isotope–geochronological (SHRIMP and TIMS) dates of zircons, the U and Th concentrations, and the comparison of age histograms of primary zircons from Riphean volcanics and rocks of the Taratash complex and detrital zircons from the Vendian (Asha Group) and Lower Riphean (Ai Formation) sandstones have shown that zircon age variations and source areas of zircons are comparable in many aspects. It follows that the geochronological features of primary zircons from the Riphean volcanics and rocks of the Taratash complex as sources of detrital zircons for the Riphean and Vendian sandstones in the Southern Urals are controlled by redeposition processes, though the influence of distant source areas remains possible.

Data on the species and strain specificity of micromycetes in the processes of toxic elements extraction from multicomponent solutions are obtained as results of modal experiments. The results also indicate the possibility of biogenic mineral formation in organic strata.

A Late Neoproterozoic U–Pb zircon age is established for the first time for arc metadacites (691 ± 8.8 Ma) and basalts (572 ± 6.5 Ma) from the Kiselikha Formation of the Kutukas Series. The manifestation of basaltic volcanism is associated with rifting processes. Our studies specify the Late Precambrian stratigraphy of the Yenisei Range and the evolutionary features of the Sayan–Yenisei accretion belt at the Neoproterozoic stage of its history. The fold-and-thrust structures of the junction zone between the Yenisei Range and the West Siberian Plate may be favorable in terms of the search for unconventional oil and gas traps.

Based on the data of atomic modeling, the different schemes of isomorphic incorporation of Cr³⁺ ions into the crystal structures of CaSiO₃ and MgSiO₃ were tested in the pressure range of 18–25 GPa and at temperatures of 1873–2223 K. Under these PT parameters, the content of Cr³⁺ in these structures was estimated quantitatively. The semi-empirical simulation data are in good agreement with the results of experiments.

Based on reconstruction of the thermal evolution of the Song-Chai gneiss–granite massif (Northern Vietnam), the long-term occurrence of granitoid magma at deep levels of the Earth’s crust (H = 15–20 km, Δt ~ 20–50 Ma) is established. The geodynamic analysis and mathematical modeling of the history of consolidation and cooling of the granitoid batholith shows that the magmatic chamber was a thermal trap at the lower level of the Earth’s crust, preserving the residual granite melt for a long time. The removal of this thermal trap from the quasi-stationary state occurs in the zones of transform sliding of lithospheric plates and is accompanied by tectonic exposure of large segments of the Earth’s crust. Ultimately, this leads to transformation of the batholiths into a metamorphic core complex of the Cordilleran-type, to emplacement of residual melts, and, consequently, to the formation of commercial rare-metal deposits.

The research results were received from studying the Pechenga ore-bearing Paleoproterozoic structure, which is located on the northwestern part of the Kola region. The U–Th–Pb zircon age was determined by Secondary Ion Mass Spectrometry (SIMS) on the Sensitive High-Resolution Ion microprobe (SHRIMP-II) spectrometer and Laser Ablation Inductively Coupled Mass Spectrometry (LA-ICPMS) on the ThermoQuest Finnigan MAT Neptune instrument. Basalt conglomerates of the Televi Formation, red gritstones of the Luchlompolo Formation, and high-siliceous turbidites from the middle part of the Matert Formation were tested. On the U–Pb concordia diagram, the part of analytical points for zircon from conglomerates are approximated by the discordia with a top intercept at 2792 ± 7 Ma. All zircon grains from gritstone are located on the concordia. Most of the values of their ages lie within 2700–2820 Ma, and the lesser part of the age values lies within 2840–3000 Ma. Single grains have an age from 3037 ± 4 Ma to 3698 ± 8 Ma. The concordant value of the ²⁰⁷Pb/²⁰⁶Pb age, which is 2640 ± 16 Ma, was established for turbidite zircon. Rocks of the basement at the northern rim of the Pechenga structure: gneisses of the Kirkenes, Varanger, and Svanvik complexes (2715, 2803, and 2825 Ma) and high-aluminous gneisses (2798–2830 Ma) were sources of zircon for conglomerates and gritstones. Granitoids from the southern flank of the structure were sources of zircon for turbidites. The predominant role of the zircon group with an age of 2.7 Ga proves the global increment of the continental crust during this period. The ancient age of zircon (3.0–3.7 Ga) of red-colored gritstones is related to deeper erosion of the basement and exposure of the Eoarchaean and Mezoarchaean rocks at the northern rim during the period of the first global “Oxygen revolution” (2.4–2.3 Ga).

The purpose of this work was to study the seismic attributes of the Podvodnikov Basin basement. It was found that these attributes, first of all, P-wave velocities of 5.9–6.2 km/s, the ratio V_P/V_S = 1.71, and the diffraction nature of the reflections from the basement indicate that the basin has a continental origin and that its tectonic development began at the pre-oceanic stage of evolution of the Arctic.

A description of the initial excitation of spheroidal mode ₀S₂ initiated by the 2013 Sea of Okhotsk earthquake (M_w = 8.3) is presented. It is based on the newly revealed fact of the origination of a standing P-wave in the epicenter of the Sea of Okhotsk earthquake and excitation of the traveling surface P-waves on the Earth’s surface by this wave. A new interpretation of the nature of the Earth’s free spheroidal oscillations in the case of a strong earthquake (M ≥ 7.5) is proposed. The spheroidal mode ₀S₂ is interpreted as a combination of standing and traveling P-waves, transferring the energy of Earth’s deformations.

On the basis of a 39-year record of satellite-based data, three basic types of large-scale structures of sea ice drift that are typical for the winter season have been distinguished. The types of atmospheric circulation that create the structure of sea ice drift fields have been revealed. The mechanism by which the drift field variations affect the interannual variations of the extent of sea ice in the Arctic Ocean has been described.

Based on analysis of the annual and seasonal variability of river runoff, the specificity of the water regime of the Ural River basin is determined. It is established that in recent decades there has been a trend to the redistribution of seasonal runoff expressed in an increase in the share of winter low-water runoff. Based on analysis of the difference integral curves, phases of different water content are revealed; the prevalence of common-mode runoff fluctuations indicates the leading role of climatic factors of runoff formation. An important feature of the regime of the rivers in the steppe regions is the intra-annual variability of runoff, which forms extreme hydrological situations (low water or high water). The results obtained should be considered in organizing cost-effective and environmentally safe water use in the Ural River basin.

The species climatic range of a dangerous locust pest, called the Italian locust, was modelled for the territories of Russia and neighboring countries over two time periods of 1956–1975 and 1996–2015. On the basis of analysis of the constructed schematic map, the northward expansion of the climatic range of the Italian locust in 1996–2015 in comparison to the period of 1956–1975 is shown. The expansion is explained by the increasing trend of the average global surface air temperature in recent decades. The obtained data can be used for monitoring locust pests in agriculture.

In 2016–2017, the yearly long measurements of the current velocities were carried out at 100 m depth below the thermocline and at 1700 m depth for the first time, which was about 100 m above the seabed using the mooring station in the deep central part of the Black Sea. The analysis of this new dataset allowed us to uncover the following. In the near-bottom layer, significant current velocities were recorded reaching a peak magnitude of 0.13 m/s. Near the frequency of 1 × 10^–6 Hz, in the transition region of the energy spectrum, the spectral energy of the deep current was close to that observed in the same range in the sea layer below the thermocline. In the range of the balanced geostrophic motions at a depth of 1700 m, the energy spectrum had a slope of –2.8, which should be compared to the spectrum slope of –1.8 obtained for the current below the thermocline at the depth of 100 m. Regular strong currents were observed around the local inertial frequency f_I. There was a “blue shift” of the inertial maximum up to 5% with respect to f_I in the energy spectrum.

This paper describes the technology for recording surface wave signals and sea level fluctuations in the coastal areas of the World Ocean based on real-time analysis of the surveillance camera “live video” presented on the Internet. A wave signal obtained by the method described in Crotone Port (Italy) is compared with the data from a nearby station of the Global Sea Level Observing System (GLOSS). This example demonstrates the high recording quality of the seiche oscillation system in the port with periods from 40 to 2 min, which is comparable to GLOSS. In addition, in contrast to the GLOSS stations, signals obtained through video contain responses of even shorter period (up to tens of seconds) seiches, swell waves, wind, and ship waves.