Middle Caspian Research Articles

LATERAL GROWTH OBJECTS IN SEDIMENTARY COVER OF SOUTH CASPIAN BASIN

In this paper sedimentation process and lateral growth objects in deepwater uncompensated and shallow water epicontinental-paleo basins developed at various evolution stages of South Caspian and Middle Caspian basins are being considered. The role of boundary structures of Scythian-Turan platform in the Middle Caspian and avalanche sedimentation on the continental shelf in development of sedimentation units and specific shape objects of lateral growth in many kilometers long sedimentary cover of South-Caspian basin has been shown. According to the interpretation of seismo-stratigraphic data the inflow of paleodeltaic, avandeltaic and turbidite objects of lateral development for infill of the Early Pliocene basin has been proved

Пограничные юрско-меловые отложения акватории Среднего Каспия: строение, стратификация и перспективы нефтегазоносности (на примере Сарматско-Хвалынской зоны поднятий)

Пограничные юрско-меловые отложения акватории Среднего Каспия: строение, стратификация и перспективы нефтегазоносности (на примере Сарматско-Хвалынской зоны поднятий)

ОСОБЕННОСТИ РАННИХ ЭТАПОВ РАЗВИТИЯ АНЧОУСОВИДНОЙ КИЛЬКИ (CLUPEONELLA ENGRAULIFORMIS BORODIN)

For more than 50 years anchovy sprat fishing in the Caspian Sea has been a leading trend. Yearly sprat catch reached 440,000 tons. The main fishing object was anchovy sprat represented in the Caspian Sea by a single population consisting of a large number of non-separated reproductively biological groups occupying the area of the Middle and Southern Caspian at a depth more than 15-20 m. Studying the size of population in sprat generations is impossible without knowing embryonic and post embryonic periods of species development, because main elimination of generations takes place in early ontogenesis. This problem has not been studied thus far and requires further investigation. The study is based on the results of scientific surveys made in 2010-2017 in the Middle and Southern part of the Caspian Sea by the researchers of Caspian scientific institute of fisheries. The study of early stages of development was carried out at water temperature of 19-20°C, samples were taken every hour. Fecundation was made by dry method in Petri dishes; impregnated roe was transferred into aquariums. Early stages of impregnated eggs development: processes of swelling and forming a plasma knob, blastomeres, stages of forming morula, blastula, gastrulation turning into organogenesis (from segmentation up to emerging prolarvae from membrane). Post-embryonic development is characterized by forming rudimental fins, mouth opening, movements that precede swimmability, pigmentation of eyeballs, orientation to light. For 11th-14th day after hatching there takes place the change of mixed nutrition to food taken from the water, which means qualitatively new, larval stage of development.

The Sufficiency of Deep Hydrocarbons in the South Caspian Region for Turkey and European Union

The Caspian Sea region did not appear as an important hydrocarbon province during the Soviet Union. This is because that Soviet Russia has very rich and exploitable oil and gas reserves in areas outside the Caspian region. The Caspian Sea coastal states as Azerbaijan, Turkmenistan and Kazakhstan, after gained their independence, have prioritized assessing the hydrocarbon reserves of the region in line with their governance policies and have started to include external partners in their exploration and development study. In order to develop the long known hydrocarbon assets of the region, the exploration efforts carried out have enabled the discovery of new fields especially in the Azerbaijan sector of the southern Caspian region. In addition, hydrocarbons discovered in the onshore areas of both Kazakhstan and Turkmenistan have made the southern Caspian region the world's major hydrocarbon province. The tectonic evolution and petroleum systems of the hydrocarbon-bearing basins called as the North Caspian, Middle Caspian and South Caspian basins in the Caspian Sea region, differ in terms of both essential elements and processes. The most important differences of the South Caspian Basin are rapid deposition of more than twenty-five km thickness sediment fill resulting from an avalanche type sedimentation and the presence of the young Tertiary hydrocarbon source rocks and reservoirs. Therefore, generation-migration, accumulation and trapping processes of the South Caspian Basin petroleum system are still continuing.

Contourites in the Derbent Basin, Caspian Sea (Geophysical Data)

A high resolution seismic survey carried out by the Shirshov Institute of Oceanology, Russian Academy of Sciences in 2004–2012 near the foot of the continental slopes of the Derbent Basin (Middle Caspian) revealed evidence for active accumulation of contourites in the Pliocene–Holocene. The discovery of these forms and deposits in the Middle Caspian is of great importance for understanding the sedimentation and formation of the bottom topography of the Caspian Sea.

Seasonal Variations of Currents over the Western Slope of the Middle Caspian Bed

Results of field observations of current dynamics in the frontal zone of the western Middle Caspian are given. The cyclonic circulation over the western slope in winter is shown to be a unidirectional intense current with velocities up to 100 cm/s. In summer, the current slows down and separates into branches—it turns southwestward and westward at the slope depth down to 150 m, southward and southeastward at the depth of ~100–350 m, and eastward at larger depths. In summer, shelf currents interact with the flow of Middle Caspian cyclonic circulation, resulting in that anticyclonic vortices reach the shelf.

Contour Currents and Contourites of the Middle Caspian

Experimental data have shown that the cyclonic circulation in the Middle Caspian is a seasonal contour current surrounding the Middle Caspian megabasin along the slope during the cold half of the year. This current and the enormous influx of suspended particulate matter on the western slope of the Middle Caspian Basin provide conditions for the formation of contourites near the slope foot. In addition, the joint action of the contour current and slope gravity flows led to the formation of specific accumulative structures, sedimentary waves, on the western slope of the Middle Caspian.

Contour Flow and Countourites of the Middle Caspian

Contour Flow and Countourites of the Middle Caspian

СОВРЕМЕННОЕ СОСТОЯНИЕ И ПЕРСПЕКТИВЫ РАЗВИТИЯ ПРОМЫСЛА КАСПИЙСКИХ КИЛЕК

The article presents annual statistical data of the Caspian Research Institute of Fishery. There has been kept track of the long term dynamics of the stocks of three species of Caspian sprat (anchovy, big-eyed kilka, sprat) and investigated a process of substituting a food item of sprats Eurytemora grimmi to a small-celled copepod species Acartia tonsa Dana. According to the research results, there has been determined growth potential of stocks of each species. Ctenophoran-Mnemiopsis has an adverse effect on sprat population by eating fish eggs and larvae. Ctenophoram - Mnemiopsis is a nutritional competitor to the full-grown fishes. The article gives recommendations on reclamation of stocks of the most perspective species - common sprat, whose biological characteristics helped not to suffer during Ctenophoram outburst and to increase its population during change of the main food item. Hydroacoustic survey data prove the intensive growth of common sprat biomass in the north-west part of the Middle Caspian. According to the results of the research it may be concluded that to realize the volumes of recommended sprat catch it is necessary to organize the marine fishery of common sprat at the Russian Middle Caspian shelf.

The Structure of Currents in the Western Middle Caspian Sea: Present-Day Studies

Data on the dynamics of bottom currents along the western coast of the Middle Caspian are given. The contributions of the mean kinetic energy of currents and the energy of perturbation to the total energy of currents are shown at different space and time scales of variations and for different seasons of the year. The results of studies are based on experimental data collected by CTD sounding of water mass, measuring currents with the use of Potok-M instruments, ADCP Doppler acoustic current meters in the regime of sounding and towing, as well as stationary measurements at submerged buoy stations.

Hydrocarbons in the Surface Layer of Bottom Sediments in the Northwestern Caspian Sea

The paper presents research results on the concentrations and compositions of aliphatic and polycyclic aromatic hydrocarbons in the surface layer of bottom sediments in the Northwestern Caspian Sea (2014) and compares them to data for sediments of the Middle and Southern Caspian (2012–2013). The seepage of hydrocarbons out of the sediment mass, resulting in abnormally high concentrations of aliphatic hydrocarbons per dry weight (up to 468 μg/g), as well as within the Corg composition (up to 35.2%), is considered the main source of hydrocarbons in sediments in the surveyed area of the Northern Caspian. This is also confirmed by the absence of any correlation between the hydrocarbon and Corg distributions, as well as by the transformed oil composition of high-molecular alkanes. The distribution of markers within polycyclic aromatic hydrocarbons points to a mixed genesis—petrogenic and pyrogenic—with prevalence of the latter. Unlike the shallow-water northern part of the Caspian Sea, the content and composition of hydrocarbons in deep-seated sediments are affected by facial conditions of sedimentation and by matter exchange at the water–bottom interface. Therefore, despite high Corg concentrations (up to 9.9%), sediments in deep-water depressions are characterized by a quite low concentration of aliphatic hydrocarbons (52 μg/g on average; 0.2% of Corg) with prevailing natural allochthonous alkanes.

Stable Isotopic Composition of Particulate Organic Carbon in the Caspian Sea

The data on the isotopic composition of particulate organic carbon (δ13CPOC) in the Caspian Sea water in summer–autumn 2008, 2010, 2012, and 2013 are discussed in the paper. These data allowed as to reveal the predominant genesis of organic carbon in suspended particulate matter of the active seawater layer (from 0 to 40 m). The δ13CPOC =–27‰ (PDB) and δ13CPOC =–20.5‰ (PDB) values were taken as the reference data for terrigenous and planktonogenic organic matter, respectively. Seasonal (early summer, late summer, and autumn) variations in the composition of suspended particulate matter in the active sea layer were revealed. A shift of δ13CPOC towards greater values was seen in autumn (with a slight outburst in the development (bloom) of phytoplankton) in comparison with summer (with large accumulations and an extraordinary phytoplankton bloom confined to the thermocline area). The seasonal dynamics of autochthonous and allochthonous components in the suspended particulate matter of the Middle and Southern Caspian Sea was studied with the use of data on the concentration of particulate matter and chlorophyll a, the phytoplankton biomass and the POC content.

Structure of the Maikop complex of the Caspian Sea region based on seismic stratigraphic research

The paper reports on the structure of the Oligocene–Lower Miocene Maikop complex of the Caspian Sea and its margin on the basis of seismic and geological data. It is shown that the regional structure of Maikop deposits of Ciscaucasia and the Middle Caspian is characterized by large clinoform sedimentary bodies. New data on formation, structure, and occurrence of clinoforms in Maikop deposits are generalized for the researched region. Two main systems of clinoforms were defined in the Maikop complex: the single large cone located in the Middle Caspian and Eastern Ciscaucasia and the southeastern system of clinoforms located in the area of Kazakh Bay. Structural characteristics and sedimentogenesis of a clinoform formation are revealed using seismic and sequence stratigraphic methods.

Tidal oscillations in the Caspian Sea

Long-term hourly data from 12 tide gauge stations were used to examine the character of tidal oscillations in the Caspian Sea. Diurnal and semidiurnal tidal peaks are well-defined in sea level spectra in the Middle and South Caspian basins. High-resolution spectral analysis revealed that the diurnal sea level oscillations in the Middle Caspian Basin have a gravitational origin, while those in the South Caspian Basin are mainly caused by radiational effects: the amplitude of diurnal radiational harmonic S1 is much higher than those of gravitational harmonics О1, P1, and K1. In the North Caspian Basin, there are no gravitational tides and only weak radiational tides are observed. A semidiurnal type of tide is predominant in the Middle and South Caspian basins. Harmonic analysis of the tides for individual annual series with subsequent vector averaging over the entire observational period was applied to estimate the mean amplitudes and phases of major tidal constituents. The amplitude of the M2 harmonic reaches 5.4 cm in the South Caspian Basin (at Aladga). A maximum tidal range of 21 cm was found at the Aladga station in the southeastern part of the Caspian Sea, whereas the tidal range in the western part of the South Caspian Basin varies from 5 to 10 cm.

Diversity, morphology and karyotypes of species from genus Neogobius (Perciformes; Gobiidae) at coastal zone of the Caspian Sea (Aktau city)

The paper presents the results on the diversity, morphology and karyotypes of species from the genus Neogobius collected during the summer seasons 2012-2016 in the shallow coastal zone of the Caspian Sea (Aktau city). A total of 6 species of goby fish belonging to two genera were found: Neogobius Iljin, 1927 and Ponticola Ilijn, 1927. Most species are widespread in the Northeast and Middle Caspian. The results of the morphological analysis did not reveal any significant differences between the populations of goby fish of the Northern and Middle Caspian, and also in comparison with the literature data. Chromosome kits and karyotypes detected in the observed gobies N. fluviatilis pallasi, N. melanostomus affinis, N. caspius, P. gorlap and P. syrman eurystomus are represented in the diploid set mainly by 46 acrocentric chromosomes, and in one species previously identified by us as N.sp (P.iljini) 2n = 40 chromosomes with a number of chromosome arms (NF) 46.

Euxinia as a dominant process during OAE1a (Early Aptian) on the Eastern Russian Platform and during OAE1b (Early Albian) in the Middle Caspian

A detailed study of the mineral composition and microstructure of the black shales associated with OAE1a (Eastern Russian Platform), OAE1b (Middle Caspian), and the host rocks has been carried out using X-ray diffraction, scanning electron microscopic, and microprobe analyses. The results provide important constraints for depositional environments in the sedimentary basins. Black shales with pyrite framboids imply euxinic (sulfidic) conditions with increased organic matter preservation. Disintegrating framboids suggest partial or complete dissolution of the organic matter inside the framboids due to increasing water oxygenation. OAE1a on the Eastern Russian Platform is heterogeneous as it includes thin interbeds of concretionary coccolith limestones within the interval of bituminous shales, and correlates with the Lower Aptian Rhagodiscus angustus nannofossil zone. The coccolith limestones indicate short intermittent episodes of interrupted stagnation, rapid oxygenation, and restoration of normal marine conditions. The presence of montmorillonite, albite, microcline, and diopside in the bituminous siltstones and in the host siltstones of OAE1a on the Eastern Russian Platform, as well as a high content of titanium in the black siltstones correlated with OAE1b in the Middle Caspian allow proposing significant input of pyroclastic material into the extant sea.

NUMERICAL SIMULATION OF THE CASPIAN SEA CIRCULATION USING THE MARINE AND ATMOSPHERIC RESEARCH SYSTEM

The Marine and Atmospheric Research System (MARS) for simulation of the Caspian Sea meteorological characteristics is presented. It includes computation of the atmospheric forcing with the regional non-hydrostatic atmosphere model Weather Research and Forecasting model (WRF), as well as computation of currents, sea level, temperature, salinity and sea ice with the model of marine circulation INMOM (Institute of Numerical Mathematics Ocean Model), and the computation of wind wave parameters using the Russian wind-wave model (RWWM). The results on verification of the hydrometeorological characteristics simulated with MARS are presented. Also, the retrospective simulation of the thermohydrodynamic characteristics for the Caspian Sea was performed with MARS for the ice-free period 2003–2013. The important features of the Caspian Sea circulation are shown. The wind currents contribute the most significantly to the Caspian Sea circulation. The upwelling effect in the eastern part of Middle Caspian is caused by regional northerly winds. It should be noted that where the outputs of different models for North and Middle Caspian are in good agreement, there is significant difference in the estimates of the currents in South Caspian. The wind fields computed in MARS using the non-hydrostatic model WRF and those obtained by the formulas of geostrophic wind inferred from the pressure field from the same model are in good agreement in Middle and North Caspian. However, they differ significantly for South Caspian. This is especially noticeable at the eastern and southern coasts, where the wind computed in WRF is directed transversely to the isobars. It is shown that the wind field and the current field are interconnected. For the Caspian Sea, one should use non-hydrostatic atmospheric models such as WRF or COSMO for wind computation.

Geochemical anomalies in South Caspian sediments

Study of the element composition of ten samples of modern terrigenous and carbonate sediments from the northern part of the Caspian Sea by the ICP-MS method showed that these sediments were enriched in sulfur, nonferrous metals, and some related minor elements including Se, Te, Re, and others in comparison with the average composition of sedimentary rocks. It is assumed that local hydrothermal seeps similar to those known on the Cheleken Peninsula and which may be formed in other areas of this tectonically active zone are the sources of these elements. In addition, such a composition of sediments may indicate the sporadic contamination of bottom water with hydrogen sulfide, which has been observed in areas of the South and Middle Caspian by many researchers.

Changes in the strategy of migration of gulls (Laridae) along the western coast of the Caspian Sea as a result of environmental changes in space and time

This paper generalizes the data obtained in 1995–2014 in the regions of the Sulak and Turali lagoons of Dagestan (the western coast of the Middle Caspian). The lagoons are located in a “bottleneck” that is a narrow migration corridor traversed by one of the largest migration routes of trans-palearctic species in Russia. This route is a part of the West Siberian–East African migration range. The migration traffic and territorial localization of the Laridae populations participating in the total migratory flow along the western coast of the Caspian Sea have been determined. The present-day migratory range of Laridae that covers the space from West Europe to the Baikal Lake and West India is specified. It is determined that Dagestan is crossed not by one but two independent and stable migration flows of Laridae, which fly across the transit region in different migration routes, but at the same periods of time. Three types of migration intensity of Laridae across the study area are defined: weak, average, and mass migration. Both spring and autumn migrations include five peaks of migration activity (migratory waves). Migratory timing, taxonomical composition, and abundance of different Laridae species vary for each degree type of migratory waves. The key determinants of migratory wave intensities are the abundance of migratory populations and weather conditions of a year. Over the last 5–7 years there has been a steady decrease in the abundance of some Laridae species on the western coast of the Middle Caspian that takes place under the impact of a set of regulating factors, which act across the whole migration range. The decrease in the abundance of migratory Laridae leads to a “blurring” of clear boundaries between migratory waves and migration intensity, changing migration routes of some Laridae populations, which now have shifted from traditional wintering routes along the western coast of the Caspian Sea and countries of the Middle East and northeastern Africa to India.

Hydrodynamic basis of formation of large-scale water circulation in the Caspian Sea: 2. Numerical calculations

The contributions of wind, water baroclinicity, and evaporation to the formation of water circulation over the depressions of the Middle and Southern Caspian are calculated numerically. The results show that all three factors—the wind, baroclinicity, and evaporation—are involved in the formation and maintenance of cyclonic water circulation over the depressions. The hydrodynamic basis of the formation of upwelling at the western and eastern coasts of the Middle Caspian are analyzed. A hypothesis is proposed regarding a more complicated, binuclear structure of the upwelling at the eastern shore of the Middle Caspian, and a theoretical substantiation of this hypothesis is given. From theoretical considerations, it is derived that the upwelling at the western shore of the Middle Caspian is of wind nature, but is governed by the integral effect of the spatial distribution of wind, rather than local alongshore wind.