Structure Of Sedimentary Cover Research Articles

Morphology and Sedimentary Cover Structure of Long Segments of the Gakkel Ridge

The rift valley of the Gakkel Ridge was divided into three segments according to sub-bottom profiling and seismoacoustic studies carried out by R/V Akademik Fedorov at the Gakkel Ridge in 2019–2020, and on seismic data of 2011–2015. West of 75° E, the rift valley crosses the Gakkel Ridge approximately in the middle, as was expected based on the assumption that the rift valley runs along the spreading axis that formed this ridge. East of 75° E, the rift valley shifts to the southwestern edge of the ridge, and, thus, it can be concluded that the spreading axis jumped to its present position relatively recently (in the Pliocene). Finally, to the south of the the Gakkel caldera (about 120° E, 81° N), the rift valley is manifested in the sections as a young graben through many kilometers of sediments.

Role of glacial and lithodynamic factors in the formation of the sedimentary cover structure of the Great Salma Strait (White sea)

New data on the bottom relief in the waters adjacent to the Belomorskaya Biological Station of Moscow State University (Kandalaksha Bay), obtained with the help of a multipath echo sounder (MBE), allowed us to study the bottom relief in detail and clarify the structure of Quaternary sediments in this area, significantly detailing the previously obtained data of continuous seismoacoustic profi ling (CSP). In the western part of the studied water area, the de Geer moraines were first identifi ed in a complex of glacial deposits, which were formed during the retreat of the glacier in the late Pleistocene in an easterly direction towards the modern deep-water part of the White Sea. In the deep-water part of the water area, according to the data of the MBE and CSP, sediments were studied, the genesis of which is due to the intensive manifestation of gravitational processes at the end of the Late Pleistocene — Holocene. The new data obtained may indicate the existence of “dead” ice in the Belomorskaya Depression.

The Triassic of New Siberian Islands Archipelago and Its Position in the Structure of Sedimentary Cover of the Laptev Sea Shelf

AbstractThe geological study of the Mesozoic sections of the New Siberian Islands archipelago and Asian coastal sections of the Arctic Ocean plays a key role in tying the results of comprehensive studies with seismic data on the Laptev Sea shelf and the western part of the East Siberian Sea. Therefore, it is extremely important to improve the subdivision of the Triassic system of the New Siberian archipelago and to define the position of the system in the structure of the Laptev Sea shelf sedimentary basin. The results of our study were used to improve and refine the lithostratigraphic subdivision of the Triassic in the study area and to recognize a distinct interregional stratigraphic marker, i.e., the Czekanowski Formation (lower Olenekian). In terms of genetic, structural, and sedimentological features, the Triassic strata were grouped into two Groups: the Reshetnikov Group (Induan–upper Ladinian) and the Svetlaya Group (Ladinian–Rhaetian), reflecting major stages of sedimentation. For the Triassic of the eastern Laptev Sea shelf and adjacent onshore areas, the facies zonation scheme has been developed and refined on a unified basis. Based on their structure, the Phanerozoic sections of the study area can be considered as a part of the intermediate structural stage of the Laptev Sea plate at the margins of the Siberian craton.

The impact of active petroleum system on light hydrocarbons distribution in marine sediments

Integrated interpretation of regional geochemical data and results of the numerical BM&PSM performed at the east part of the Sea of Azov and northeast part of the Black Sea reveal a correlation between the spatial distribution of light hydrocarbons in seabed sediments and investigated petroleum systems. The obtained results point out that the spatial distribution of gaseous hydrocarbons in marine sediments reflects the geological structure of sedimentary cover, and the maturity of petroleum systems, located within the basins. The origin of background levels and anomalies of light hydrocarbons was explained depending on the present-day petroleum system activity and the structure of overburden rocks.

СЕЙСМОСТРАТИГРАФИЧЕСКАЯ МОДЕЛЬ АЛДАНО-МАЙСКОГО ОСАДОЧНОГО БАССЕЙНА (ЮГО-ВОСТОК СИБИРСКОЙ ПЛАТФОРМЫ)

Generations of the materials of the seismic exploratory works conducted in the Aldan-Maya sedimentary basin substantiated the seismostratigraphic model and construction of the lateral and longitudinal sections allowed an understanding of the specific features of the sedimentary cover structure and specifying the basin boundaries. Based on the seismic sections and geologic map at a scale of 1: 2 500 000 a scheme of structures formed in the Riphean was developed. These constructions made it possible the purposeful plan of the oil-and-gas searching and exploratory works, estimation of thickness and area of the parent material. The investigations made can be applied for clarification of the structure of the eastern Siberian Platform.

Sedimentary cover structure of fresh water lakes of Kindo peninsula near the White sea Biological station of Moscow State University according to georadiolocation and drilling data

The geological structure of two freshwater lakes (the Verkhneye and the Vodoprovodnoye) located near the White sea biological Station of the Moscow State University (the Kandalaksha Bay of the White sea) is considered for the first time according to the GPR data. The morphology of the top of the Archean basement, the structure of the Quaternary sedimentary cover and bottom relief were studied. Shallow marine sediments overlying the rocks of the Archean and a sequence of lacustrine-marsh sediments were identified using the drilling data in the Quaternary cover. Structural schemes were constructed for the main reflecting horizons, while isopach schemes were generated on the basis of the main sequences. The values of electrical resistivity and absorption coefficient are calculated and the possibilities of their use for the delineation of GPR facies are considered.

Morphostructures and the sedimentary cover structure of the Western Crimea inner shelf

The results of geophysical and geomorphological works on the Western shelf of the Crimea peninsula (Evpatoria-Balaklava) are presented. The structure of the sedimentary sequence, the bottom topography and paleogeographic reconstructions of the conditions of the western shelf formation in the Late PleistoceneHolocene are considered. Based on the analysis of geoacoustic profiles, the main morphostructures of the shelf are identified and their brief characteristic is given. An abrasion-accumulative complex consisting of an abrasion platform and an associated accumulative clinoform, the formation of which is associated with the coastal line of the Late Pleistocene Black Sea regression to depths of about -90 m, traced from Yevpatoria to Yalta, was selected. On the shelf of the Kalamitsky Bay, fragments of the flooded river network and coastal accumulative forms such as bars were investigated.

Morphostructures and Sedimentary Cover Structure of the Inner Shelf of Western Crimea

The article presents the results of geophysical and geomorphological works on the western shelf of the Crimean Peninsula (Yevpatoriya–Balaklava). The sedimentary sequence structure, seafloor topography, and paleogeographic reconstructions of the formation conditions of the western shelf in the Late Pleistocene–Holocene are considered. Geoacoustic profile analysis aided in identifying the main shelf morphostructures; a brief description is presented. The abrasion–accumulative complex is identified, which consists of the abrasion platform and associated accumulative clinoform, the formation of which is related to the coastline of Late Pleistocene Black Sea regression to depths of about 90 m, traced from Yevpatoriya to Yalta. On the shelf of Kalamita Bay, fragments of a drowned river network and coastal accumulative landforms such as bars were studied.

Towards а design of new generation digital seismic seabed seismographs – current state and future outlook

The paper presents the comparative characteristics of self-pop-up digital seabed seismometers that have been developed since the early 2000s. The requirements for the main technical characteristics that should be considered for developing the new-generation of self-pop-up seabed seismometers have been proposed. The microcontroller and reference frequency generator are the key parts for a seabed seismometer design. The paper provides the development results of these key components, which are essential for the seismometer performance (power consumption and functionality).
 A draft proposal for seabed seismic exploration project in the Russian sector of the Black Sea solving the current actual geological problems is presented. Implementation of the project will contribute to determination of the crystalline basement depth within the Shatsky ridge and the Tuapse depression; detection of P and S wave velocities in the lower part of sedimentary cover and in the basement, and to the refinement of the Earth’s crust thickness. The extension of regional seabed seismic lines from the Turkish to the Russian sector of the Black Sea will give the scientists a clearer picture of the Earth’s crust structure over the whole east Black Sea basin. The results of seabed studies will verify and improve the results of the Black Sea 2011 towed-streamer survey (with 10 km streamer) on the sedimentary cover structure and the Earth’s crust.

Horizontally deplacement geomasses in the continental rift geostruсtures (on the example of the Dnipro-Donets paleorift). Part 2. Structural parageneses of the reid deformation of the sedimentary cover

Formulation of the problem. The inversion stages of the structural-material evolution of the continental crust are characterized by regional scale of the deformation of volume tectonic flow of platform sedimentary rocks, which caused significant horizontally-healthy movements of tectonically activated geo-mass in the intra-plate graben-rift. The dynamic deformation of geomases manifests itself at the final stages of the geological development of such structures; therefore, it determines the main features of the systemic organization of the modern architecture of the basement and sedimentary cover complexes. Review of previous publications and studies. Secondary deformation linear slope, according to Patalakha E. (1979); Alekseev V. (1990) is considered as a set of local strike-slip zones, formed on spherically-located viscous faults, forming joint tectonic flows. The structural skeleton of tectonic flows, as the basis of the tectonic dislocation process, make offsets with the horizontally and rotational component movements. Horizontal landslides are typical disjunctive elements of the continental structures formed in the geodynamic conditions of the transtension (grabens, rifts), transpression (folded mobile belts, intra-plate activation zones), as well as the basic structural elements of the strike-slip tectonics of the sedimentary basin. The purpose of the article. The second part of the trilogy continues regional geotectonic studies of post-rift complications of the sedimentary cover structure of Dnipro-Donets Paleorift (DDP), covering the three main stages of the platform tectonic activation. Late Hercynian epoch was characterized by the formation of large linear anticlinal zones and salt-shafts against the background of the general syneclizal deflection of sedimentary basin, located within the paleorift. Cimmerian epoch of tectonic activity led to significant thrust deformations of the primary structural forms of the cover in the geodynamic setting of collision compression with intensification of the horizons of the sedimentary cover. The structural manifestation of strike-slip tectonics at Alpine epoch in sedimentary complexes are mainly horizontal displacements of geomases of blocks, lineaments, local tectonic elements and structures along dynamically interconnected coulisse of strike-slip domains. Methods. Structural kinematic analysis of transformations of the fracture systems of the Upper-Visean sedimentary complex under the influence of natural mechanism of reid tectonic flow of rocks. Results. The secondary structures of strike-slip deformation, structural kinematic parageneses, dislocations zones and subregional structural waves were identified in the structure of the platform cover, which are natural geological objects formed at the inversion stages of geological development of DDP. Scientific novelty and practical significance. The result of structural manifestation of volume tectonic flow in the platform complex was horizontal displacements of the original tectonic elements, blocks, segments, structures along dynamically-linked strike-slip domains. This is caused by the formation of secondary deformation structures of various scales, morphology and genesis, which comprise longitudinal structural waves of strips of post-rift deformations in the structure of the sedimentary cover of DDP.

Тектоника области сочленения ВосточноЕвропейской платформы и Соликамской депрессии Предуральского прогиба

Comparison of the geological structure of sedimentary cover of the eastern part of the East-European Platform and the Solikamsk Depression within the Pre-Urals Foredeep Basin was carried out. It is shown that halogen and clastic formations of this basin have lower mechanical properties compared to surrounding carbonate strata. Because of the horizontal compressive stress, the asymmetric plastic body formed by these rocks experienced intensive deformations. It is shown that the tectonic influence of the Urals extends through the Solikamsk Depression to the western edge of the Pre-Urals Foredeep basin.

Mid-Cretaceous Tuor-Yuryakh Section of Kotelnyi Island, New Siberian Islands: How Does the Probable Basement of Sedimentary Cover of the Laptev Sea Look on Land?

The model of geological structure of sedimentary cover of the Laptev Sea accepted by most geologists suggests that the lower seismic complex of the cover begins by the Aptian–Albian sedimentary rocks. They can be studied in natural outcrops of Kotelnyi Island. The section of the Tuor-Yuryakh Trough, which exposes the lower part of the Cretaceous complex, is described in the paper. It is composed of continental coaliferous rocks ~100 m thick. The marking beds divide it into five members, which are traced along the western wall of the trough at the distance up to 3 km. The spore–pollen complexes and plant megafossils indicate that almost the entire visible section of the mid-Cretaceous is Albian. Only its lower part no more than 14 m thick can probably belong to the Aptian. Marine facies with Albian foraminifers were found 15 m above the bottom of the Cretaceous complex. The section of the Cretaceous rocks is underlain by the Lower Jurassic marine clays and siltstones. The foraminifer assemblages of this part of the section are typical of the upper Sinemurian–Pliensbachian and fossil bivalves indicate late Sinemurian age of the host rocks. The hiatus ~70 Ma duration has no expression in the section and this boundary can de facto be substantiated only by microfossils. This vague contact between the Lower Jurassic and mid-Cretaceous rocks does not correspond to geophysical characteristics of the bottom of the lower seismic complex of the cover of the eastern part of the Laptev Sea. The latter is described as the most evident seismic horizon of the section of the cover, suggesting unconformable occurrence of the lower seismic complex on a peneplenized surface of lithified and dislocated rocks. This is mostly similar to the bottom of the Eocene sediments, which were observed on Belkovsky and Kotelnyi islands. The paper discusses possible application of our land results for interpretation of the shelf seismic sections of the Laptev Sea. It is concluded that local reasons are responsible for a vague boundary between the Lower Jurassic and mid-Cretaceous sequences in the section studied. Our observations support ideas on possible Aptian–Albian age of the rocks of the basement of the lower seismic complex; however, it is proposed to use also the previously popular idea on the Eocene age of the lower seismic complex of sedimentary cover of the eastern part of the Laptev Sea as one of the possible working scenarios.

Seismic basement in Poland

The area of contact between Precambrian and Phanerozoic Europe in Poland has complicated structure of sedimentary cover and basement. The thinnest sedimentary cover in the Mazury-Belarus anteclize is only 0.3–1 km thick, increases to 7–8 km along the East European Craton margin, and 9–12 km in the Trans-European Suture Zone (TESZ). The Variscan domain is characterized by a 1- to 2-km-thick sedimentary cover, while the Carpathians are characterized by very thick sediments, up to c. 20 km. The map of the basement depth is created by combining data from geological boreholes with a set of regional seismic refraction profiles. These maps do not provide data about the basement depth in the central part of the TESZ and in the Carpathians. Therefore, the data set is supplemented by 32 models from deep seismic sounding profiles and a map of a high-resistivity (low-conductivity) layer from magnetotelluric soundings, identified as a basement. All of these data provide knowledge about the basement depth and of P-wave seismic velocities of the crystalline and consolidated type of basement for the whole area of Poland. Finally, the differentiation of the basement depth and velocity is discussed with respect to geophysical fields and the tectonic division of the area.

Landslides on the eastern slope of Sakhalin Island as possible tsunami sources

An underwater landslide located in the central partof the eastern slope of Sakhalin Island was found andmapped during investigations under the auspices ofthe Korean–Russian Project Sakhalin Slope GasHydrates (SSGH) [1, 2]. The study region was confined to a depression oriented in the northeasterlydirection (Fig. 1a). The research in this region [1–4]demonstrated that closed depressions with round andslightly elongated forms in the northeasterly directionare characteristic peculiarities of the morphology ofthis depression (Fig. 1b). The slope angles of theirwalls are 7–10°, while the sizes are in the rangebetween 600 m and 10 km. They are located at depthsfrom 20 to 150 m. One of the largest depressions has anotable morphology. Its northern edge is quite flat(~7°), while the southern edge is steep (25–30°). Itconsists of one or a few cliffs with a total height up to100 m (Fig. 2).Two types of the sedimentary sections were foundwithin the study region. The first one is common. It ischaracterized by numerous reflecting levels that provide evidence about the layered structure of the sedimentary column. The second type of seismic section isobserved only in the southernmost depression crossedby seismic profile LV5603 (Fig. 2). Here, we distinguish a sedimentary body whose cover has a hillystructure, while the foot corresponding to a highamplitude reflecting level cuts off the underlyingreflectors. The body is acoustically transparentbecause there are no reflecting layers. Slope boundaries and diffracted reflections are seen on the highresolution section of seismic profiler SES2000DS,which is caused by the chaotic internal structure of thissedimentary body.The abovementioned peculiarities of the sedimentary cover structure together with the morphology ofthe depression give grounds to think that this sedimentary formation is a landslide. A section made usingseismic profiler SES2000DS with a resolution on theorder of 10 cm [4] does not demonstrate that the roofof the landslide is covered with horizontally locatedsediments. Taking into account that the rate of sediment deposition in this region during the Holocenewas 33 cm over 1000 years [2], the age of the landslideis less than 300 years. The breakoff wall of the landslide is very steep (25–30°). In some regions it consistsof two cliffs. Its form is undulating, and its length is22 km (Fig. 1b). The area occupied by the landslide is42 km@2, and its volume is approximately 4 km

Seismic wave velocities in the sedimentary cover of Poland: Borehole data compilation

A knowledge of seismic wave velocities in the sedimentary cover is of great importance for interpreting reflection and refraction seismic data, deep seismic soundings and regional and global seismic tomography. This is particularly true for regions characterized by significant thicknesses and a complex sedimentary cover structure. This paper presents the results of an analysis of seismic P-wave velocities in the sedimentary cover of Poland, a complex area of juxtaposition of major tectonic units: the Precambrian East European Craton, the Palaeozoic Platform of Central and Western Europe, and the Alpine orogen represented by the Carpathian Mountains. Based on vertical seismic profiling data from 1188 boreholes, the dependence of velocity versus depth was determined for regional geological units and for successions from the Tertiary and Quaternary to the Cambrian. The data have been approximated by polynomials, and velocity-depth formulas are given down to 6000 m depth. The velocities in the sedimentary cover have been compared with those from other areas in Europe.

Deep CMP seismic surveying along the Tatseis-2003 geotraverse across the Volga-Ural petroliferous province

The objective, methods, and main results of deep CMP seismic surveying along the Tatseis-2003 geotraverse are discussed. This geotraverse crosses the Volga-Ural petroliferous province from the northwest to the southeast for more than 1000 km and is linked with the well-known Uralseis-95 geotraverse by an additional profile. The main objective of this surveying was to study the structure of sedimentary cover and the Earth’s crust as a whole in the North Tatar Arch, Kazan-Kazhim Trough, Kotel’nich Arch, and the southeastern Moscow Syneclise in comparison with the petroliferous South Tatar Arch. The applied technology (telemetric stations, powerful vibrators, a 12-km spread, a common midpoint fold of 60, and a recording time of 20 s), the planning of seismic exploration with consideration of the available geological and geophysical information, and special processing of the data—all this provided the high-quality time sections that allowed solution of the geologic problems. The main scientific and applied results of the investigations are establishment of the links between petroleum resource potential of the sedimentary cover and the structure of the Earth’s crust and upper mantle. These data are of basic importance and testify to the considerable role of deep factors in the formation of hydrocarbon fields. After these factors are tested in other regions, the revealed indications may be used in petroleum exploration. The tectonic nature of inclined reflectors in the Earth’s crust and upper mantle is substantiated. It is shown that the near-vertical dynamic anomalies are caused by real geologic bodies. A complex of investigations is proposed for their further interpretation. The deep seismic surveying along the geotraverse fulfilled its task completely. At the same time, the results obtained allow recommending lines of further research and their methods. It would be expedient to perform generalizing scientific research aimed at coordinating the Uralseis-95 and Tatseis-2003 geotraverses in order to develop a common profile from the Urals to the Moscow Syneclise, provide complex interpretation of these data, and integrate the results of the previously performed deep CMP seismic surveying.

New data on the structure of sedimentary cover at the Cape Verde Seamount and the Cape Verde Basin (central Atlantic) based on continuous seismic profiling data

New data on the structure of sedimentary cover at the Cape Verde Seamount and the Cape Verde Basin (central Atlantic) based on continuous seismic profiling data

Mechanism of formation of deep basins in continental crust in fold belts

Formation of deep basins in continental crust is usually explained by stretching. Intense stretching produces typical deformations in sedimentary cover. These deformations are observed in rift valleys. Deformations produced by stretching can in principle be revealed in presentsedimentary basins. There are also simple ways to reveal such deformations in fold belts, where the remmants of numerous deep basins in the continental crust were found. The sedimentary cover structure was analyzed in the Urals, Appalachians, Scandinavian Caledonides, North-American Cordilleras and in the Alpine, Verkhoyansk and Franklinian fold belts, but no deformations that are typical for significant stretching of continental lithosphere have been found there in most of the deep basins in the continental crust. These basins were commonly formed in cool cratonic areas by very rapid subsidence of the duration of a few million years. Such subsidence cannot be explained by thermal relaxation. Thrust loading as a cause of subsidence can also be excluded in most cases. The authors suggest a gabbro to eclogite transformation with the destruction of the basaltic layer as a possible cause of rapid subsidence. This occurs under upwelling of wet asthenosphere of not too high temperature to the base of the crust. Crustal attenuation from destruction of the basaltic layer permits an intense subsequent crustal shortening. This may explain why continental crust was intensely compressed only in those regions, where rapid subsidence of large magnitude took place.

Mechanism of continental crust subsidence in fold belts: The Urals, Appalachians and Scandinavian Caledonides

Formation of deep basins on continental crust is usually explained by lithospheric stretching. Stretching produces the large deformations in the upper, brittle part of the crust that have been found in many rift valleys. The sedimentary cover of deep basins on continental crust is exposed at the surface in fold belts in many places. Some undeformed basins have been covered by detailed seismic profiling and drilling. The sedimentary cover structure in the Urals, Appalachians and in the Scandinavian Caledonides has been analysed. No deformations typical of stretching were found in the greater part of the basins on continental crust. High magnitude subsidence without stretching can be produced by thrust loading or by a large density increase in the crust or mantle. Paleotectonic conditions exclude thrust loading as a cause of formation of the major basins in the above fold belts. Most of them were formed in cool cratonic areas by rapid subsidence in a few m.y. Their initial depth was 1–3 km. Subsidence of this type cannot be produced by thermal relaxation without significant stretching. Gabbro-eclogite transformation in the lower crust is proposed as a possible mechanism. Intense shortening of continental crust is observed only where rapid subsidence of a large magnitude took place before the folding. Not one cratonic block was strongly compressed in the fold belts considered.