Biostratigraphy of Upper Jurassic of the Valy clay pit (Samarskaya Luka) by ammonites, ostracods and dinocysts

The results of integrate biostratigraphic study of Upper Jurassic deposits of the clay pit near the village of Valy (Syzran district, Samara region) are presented. For the first time a bed-by-bed description was made and the subdivision of the section into zones, subzones and biohorizons by ammonites was established. Bauhini and Kitchini zones (Bayi subzone) are established in the Lower Kimeridgian, while Upper Kimmeridgian is represented by Autissiodorensis zone only. In the Lower Volgian Sokolovi and Pseudoscythica zones were recognized, while the Middle Volgian is represented by the Panderi zone. The age of the regionally developed unconformity at the base of the Trazovo Formation has been clarified. As in the sections located to the south from studied section, this unconformity is located in the base of the Autissiodorensis zone, overlying different Oxfordian and lower Kimmeridgian. For the first time for Kimmeridgian of Central Russia in the marlstone band of the Kitchini zone (bayi biohorizon) solitary corals conditionally attributed to the genus Trochocyathus were found. Along with corals other warm-water taxa (belemnites Hibolithes, rare ammonites Taramelliceras) were found in the same bed, suggesting deposition of this bed during the short-time warming event. 6 biostratigraphic units (zone and beds with fauna) were recognized by ostracods, along with 2 dinocyst-based units (assemblage and zone) which are compared with the stratigraphic subdivisions by these groups, previously proposed for the Kimeridgian and Volgian stages of the Russian Platform. The paleo-ecological analysis has allowed to assume, that sediments have accumulated in the conditions of warm shallow eutrophic basin with depth to 50 m, with gradual increase of eutrophy through time. At some levels, short-term episodes of severe shallowing or freshening are recorded by ostracods.

On the relation of bottom valley-type reservoir hydrocarbon carbon flux and hydrological structure of water body

Circulation of carbon in water bodies is fundamental process of nutriens cycle in water ecosystems. Carbon flux from bottom sediments is the less studied chain of this circulation nowdays. The aim of investigation was the study of HCO3 flux from bottom sediments in the valley-type reservoir and identification of their relation with hydrological structure of water body. Field works and laboratory experiments were fulfilled at Mozhaisk reservoir in 2017-2019. These years differed by weather conditions, level regime and stability of water masses. Hydrological surveys were fulfilled three times during summer period of each year. They included measuring of vertical distribution of hydrological characteristic and sampling of water and bottom sediments. The Kuznetsov-Romanenko tube method was used to study exchange processes. Hydrocarbonate carbon flux from sediments into the water may have a wide range (50-900 mgC/m2day). By comparison of HCO3 flux with hydrological structure it was revealed that in deep (>8 m) regions it depends on stratification and thickness of uniform hypolymnion, where seiches and compensation currents may promote transsedimentation from shallow places to flooded river bed. At the regions with depth <8 m hydrocarbonate carbon flux from sediments depends much more from autochthonic organic matter, produced by phytoplankton. The relationship of the HCO3 flux with the content of organic matter in the soil and its hygroscopic humidity is insignificant.

Fractionation of polycyclic aromatic hydrocarbons at geochemical barriers

The purpose of the study was to identify patterns of fractionation at geochemical barriers (GCB) of associations of marker compounds - polycyclic aromatic hydrocarbons (PAHs). Based on thermodynamic parameters, the throughput of GCB in geochemical systems (GCS) in relation to organic substances at the molecular level is analyzed. PAHs are very informative indicators of the properties of GCB (up to singular surfaces). The processes of migration and selective penetration through GCB of 15 PAHs from the list of priority pollutants recommended by the US Environmental Protection Agency (widely used in the world EPA list): Naphthalene (Naph), acenaphthene (Ace), Fluorene (Flourene), Phenanthrene (Phen), Anthracene (An), Fluoranthene (Flu), Pyrene (Py), Benzo(a)Anthracene (BaA), Chrysene (Chr), Benzo(b)Fluoranthene (BbFlu), Benzo(k)fluoranthhene (BkFlu), Benzo(a)pyrene (BaP), benzo(ghi)perylene (Bghi), Dibenzo(a, h) anthracene (DbA), Indeno(1,2-cd)pyrene (Ip). Being geochemical markers, these compounds can accumulate on barriers and selectively penetrate through them, making them especially important objects of study. Despite numerous studies, these mechanisms of mass transfer have not been sufficiently studied. The types of GCB have been identified in terms of their permeability to PAHs. It is shown that the functions of GCB in systems are much more significant and consist not only in the separation of systems from the external environment and the regulation of mass transfer. The above models of migration and accumulation are based on quantitative estimates, which makes the results more reasonable in comparison with the “conceptual” representations of the behavior of substances on GCB in most studies. The most important point - the influence of the medium contact time for establishing a stable state (stability by the migration of compounds) on GCB has been demonstrated.

Petrofabric and geochemical features of ultramafic rocks on the example of restite metamorphites of the Kuznetsk Alatau (Western Siberia), olivine cumulates of the Yoko-Dovyren layered massif (Northern Cisbaikalia) and their analogues from ultrabasic xenoliths of the Canary Islands (Spain)

The article presents the results of petrostructural and mineralogical studies of olivine grains from ultrabasic and basic rocks of different genesis. In particular, they correspond to cumulative dunites of the Yoko-Dovyren layered massif (Northern Cisbaikalia), restite hyperbasites of the Velvet massif (Kuznetskiy Alatau), and xenoliths of peridotites from basalts of the Canary Islands (Spain). The relationship between the petrostructural and mineralogical features of ultrabasic rocks is shown, which makes it possible to identify their cumulative and restite varieties. An important element of the petrostructure of ultrabasites is the orientation of olivine, which reflects either the conditions for the formation of primary crystals in the magmatic melt, or the conditions for its recrystallization as a result of plastic deformations during exhumation to the Earth's surface. The mineral composition of rocks is an additional feature that reflects the real conditions of formation. In the presence of basic plagioclase, it is already quite difficult to speak about the restitic nature of these ultrabasic rocks. On the other hand, plastic deformations of olivine are characteristic of restitic hyperbasites, in which plagioclase is absent. The results of mineralogical studies in ultrabasic xenoliths of the Canary Islands showed the presence of basic plagioclase (labradorite), as well as chrysolite-type olivine (12-16 Fa), which corresponds to the attributes of ultrabasic layered intrusions such as the Yoko-Dovyren dunite-troctolite-gabbro pluton. For restite hyperbasites (by the example of the Kuznetsk Alatau), the iron content of olivine does not exceed 9-10% of the fayalite end, while plagioclase and clinopyroxene are absent. A characteristic feature of the xenoliths of the Canary Islands is the presence of endiopside, which is present in layered intrusions, but is absent in the restrained fragments of the upper and lower mantle. It is assumed that the xenoliths in the basalts of the Canary Islands are not of a mantle nature, but are fragments of a deep magma chamber. The studies of the optical orientation of olivine in xenoliths of the rocks of Lanzarote Island confirm these conclusions. The geochemical parameters of ultramafic xenoliths on Tenerife Island may well correspond to deeper formations.

Distribution of rare-earth elements in rock-forming minerals of corundum-bearing rocks of the Khitoostrov deposit (North Karelia)

The distribution of rare-earth elements (SIMS method) in minerals from the rocks of the Khitoostrov occurrence (Belomorian mobile belt of Eastern Fennoscandia) was studied: corundum-bearing metasomatites with anomalous isotopically light oxygen and hydrogen and garnet amphibolites after gabbro with normal isotopic composition. The study was accompanied by estimates of P-T parameters of rock formation using multi-equilibrium thermobarometry (TWEEQU method). Temperatures calculated for garnet amphibolites after gabbro fall within the range of 730–770 ° C, pressures - 13–14 kbar; for corundum-bearing rocks, temperatures were 680–710 ° C, pressures - 6.5–7.5 kbar. Corundum-bearing rocks were formed at slightly lower temperatures and at significantly lower pressures than garnet amphibolites after gabbro. The REE distribution spectra in garnets from apogabbroic amphibolites are characterized by a clearly pronounced slope from light to heavy REE, while in garnets from corundum-bearing rocks they have a less pronounced positive slope, which is associated with a noticeable enrichment of garnets in LREE and an insignificant depletion of HREE. Calcium amphiboles from corundum-bearing rocks are significantly enriched in rare-earth elements as compared to amphiboles from garnet amphibolites after gabbro, especially LREE (by more than an order of magnitude) and, to a lesser extent, MREE. Plagioclases from corundum-bearing rocks are also enriched in LREE against the background of garnet amphibolites. Thus, in all the studied minerals of corundum-bearing rocks LREE enrichment is recorded. It isn’t manifested in the minerals of amphibolites and, obviously, isn’t related to the difference in P-T parameters of rock formation. Consequently, LREE was transferred by a specific fluid during mineral-forming processes, which led to the formation of metasomatites with an anomalous isotopic composition of oxygen and hydrogen.

Monitoring of stable isotopes (δ2H, δ18O) in precipitations of Moscow city (Russia): comparison for 2005–2014 and 1970–1979 periods

The isotopic composition of oxygen (δ18O) and hydrogen (δ2H) of atmospheric precipitation in Moscow in 2005–2014 was studied by sampling single precipitations (a total of 842 measurements after rejection of unreliable samples). A comparison is made with similar studies carried out by VSEGINGEO and IVP RAS for the IAEA-WMO GNIP network in 1969–1979, when monthly average samples were taken by the accumulation method (61 pair determinations of deuterium and oxygen-18, mainly in 1975–1979). The 2005–2015 series is reduced to a similar form for the 1969–1979 series, recalculated through the data on the volume of precipitation at the nearest meteorological station. It was found that in the last decade there has been a significant change in the equation of the local line of meteoric waters, which for the first period had the form δ2H = 6.09×δ18O – 23.0 ‰ (R2 = 0.87), and is currently described by the relation δ2H = 6.93×δ18O – 11.3 ‰ (R2 = 0.944). There is also a decrease in depletion of the average values of δ2H and δ18O, compared with the first observation period, which apparently reflects the course of climatic changes. At the same time, within each of the periods, a negative (albeit relatively small) slope of the line of approximation of chronological data is noted. Deuterium excess naturally changes seasonally, taking negative values in summer, primarily due to non-equilibrium fractionation during evaporation. In 2005–2014, the temperature dependence of the isotopic composition of precipitation changed significantly in comparison with 1969–1979, which makes it impossible to reconstruct the composition of precipitation in the past from meteorological observations.

Assessing the hydrological impacts of coal resource development: a case study from Australia

The objective of this study is to predict regional-scale cumulative impacts on water resources caused by coal resource developments in the Gloucester subregion of New South Wales (NSW), Australia. A key outcome of the assessment is identifying areas where water resources are very unlikely to be impacted (with a less than 5% chance) from those where water resources are potentially impacted (at least a 5% chance). Governments, industry and the community can then focus on areas that are potentially impacted when making regulatory, water management and planning decisions. Potential impacts were ruled out using a zone of potential hydrological change. This zone was defined based on at least a 5% chance of exceeding defined thresholds in multiple hydrological response variables including groundwater drawdown and eight streamflow metrics (only reductions in annual streamflow are reported here). The zone of potential hydrological change in the Gloucester subregion covers 250 km2 and includes 242 km of stream network. This represents 52% of the area and 70% of the stream length assessed. Groundwater drawdown exceeding 0.2 m in the near surface aquifer due to additional coal resource development is very likely (>95% chance) for an area of 20 km2 but is very unlikely (<5% chance) to exceed an area of 100 km2. Although 242 km of streams are identified as being potentially impacted, changes in streamflow are small, with a little over 5% reduction in annual flow in some streams close to the coal mines, and reductions in annual flow in the major rivers not exceeding 1 - 5%.

Floods in Siberia: geographical and statistical analysis for the period of climate change

In Siberia, floods are one of dangerous natural disaster. The danger of floods varies under the climatic and anthropogenic changes, as well as socio-economic development. The aim was to study the current position of problems associated with flood hazard. A key to understanding the flood situation is geographical and statistical analysis of the floods for the period of climate change (1985-2019). Such analyzes addresses the following aspects: study of flood genesis and recurrence, the severity of the impact for floods of different genesis; maxima runoff analysis as the principal cause of floods; analysis of the spatial distribution of settlements vulnerable to flooding; analysis of the ice jams and ice dams as a specific natural factor causing the floods in Siberia; assessment of the degree of danger, and identification of areas with the different integral flood danger. In Siberia, more than 1400 settlements are flooded at regular intervals. Most of them are concentrated in the southern, most developed territories in the Ob, Tom and Yeniseiy basins. In Siberia, rainfall, mixed (from snow melting with rainfall) and ice-dam floods are the most dangerous. They have the highest recurrence and severity of the impact. The greatest floods risk is in the most populated and economically developed southern regions within the Ob, Lena and Yenisey rivers and Lake Baikal basins. Territories with the highest risk of floods were determined. For the Baikal region, one of the most developed territories of Siberia, the flood hazard was determined for all administrative districts. Flood hazard maps for Siberian regions can be the basis for developing the flood adaptation strategies.

Two stage of gold-bearing sulfide ores of early Proterozoic gabbroids in the north Ladoga area

In a study based on Pb isotopes, it has been shown that the formation of gold-sulfide mineralization in the Early Proterozoic gabbros of the Northern Ladoga region is associated with different tectonic phases. This conclusion is based on a comparative study of isotopic data for feldspars and lead sulfides in two Early Proterozoic intrusions; Velimäki and Alattu-Päkylä. The investigated intrusions have similar geological settings at the junction of the Svecofennian accretionary complex and the Karelian craton. Both massifs are characterized by manifestations of noble metal sulfide mineralization associated with zones of local shear deformations. The formation of the studied ore massifs is attributed to the Svecofennian and Caledonian tectonic stages. Feldspars of Velimäki intrusion have parameters and model age of Pb significantly older than U-Pb age of zircon (1.9 Ga), although they correspond to the Svecofennian time of magmatic crystallization of gabbro and clinopyroxenites, while sulfide pyrite-pyrrhotite mineralization is associated with gold in these rocks with the Caledonian stage of fluid-thermal processing of the Early Proterozoic magmatic mineral paracenteses. Feldspars and sulfides of the Alattu-Päkylä intrusion have similar lead isotopic parameters and Pb model age (~ 2 Ga), also somewhat older than the U-Pb age of zircon, but at the same time indicating the formation of rock-forming and ore sulfide associations with gold during the Svecofennian (Early Proterozoic) plutonic and tectonic-thermal events. The source of lead sulfides of the Velimäki massif is characterized by the parameters of the upper crust with high µ2 = 238U / 204Pb, while the µ2 parameter of the minerals of the Alattu-Päkylä massif is slightly lower, which indicates the participation of the mantle-lower crustal reservoir material in the formation of magma.

Seismotectonics of Armenia: main problems

The article describes the main problems in the existing researches on the seismotectonics of the territory of Armenia. A review was conducted on certain issues related to the accuracy of the initial seismological data, the problem of identifying possible focal zones of strong earthquakes, and the probabilistic assessment of the seismic hazard of the territory of Armenia. As the results of numerous studies show, the initial seismological data from catalogs and bulletins are characterized by their heterogeneity. Different observation systems and different methods of seismological data processing have led to the fact that when visualizing the spatial distribution of earthquake epicenters on the territory of Armenia, during the instrumental period of observations, an artificially lattice network of epicenters is obtained, which does not agree in any way with the fault tectonics of the territory. During the stud of distribution of earthquake hypocenters by depth, the discrete nature of their distribution was revealed. There is also a number of disadvantages in the area of allocation of focal zones of strong earthquakes. The main part of the conducted research was mainly based on data on previously recorded strong seismic events, as well as on data on historical earthquakes, as a result, for the most part of the studied territory, in fact, no research was conducted. In addition, there are relevant questions about the tectonic basis used in these studies. The last group of problems concerns the probabilistic assessment of the seismic hazard of the territory of Armenia. It is shown that in the existing works, there are quite a lot of unsubstantiated assumptions.Based on the analysis, it is concluded that in the field of seismotectonic studies of the territory of Armenia, there are a number of urgent tasks that require priority solutions.