Geological structure of Russia. Geological structure and relief of Russia

The Omsk region is located within the young West Siberian Platform* (Hercynian Plate). The geological structure of its territory clearly distinguishes a folded foundation composed of rocks of Paleozoic and pre-Paleozoic age, and a platform cover with flat-lying deposits of the Mesozoic and Cenozoic.

The foundation has a complex structure and consists of igneous formations (granites, diabases, etc.), volcanic tuffs and metamorphosed rocks to varying degrees (gneisses, schists). The basement rocks are folded into complex folds and intersected by faults of northeastern and northwestern strike. Along these faults, some sections of the foundation blocks sank, while others rose. As a result of tectonic movements of the foundation blocks, deflections and protrusions formed on its surface.

As scientists have established using the latest geophysical data and satellite images, the foundation contains peculiar “basalt windows” - blocks composed of oceanic crust and ring structures.

The foundation surface plunges from south to north. Thus, in the south of the region, the foundation is exposed by wells at a depth of several hundred meters, in Omsk - 2936 m, in the Kormilovsky district (Novo-Alekseevsky state farm) - 4373 m.

The platform sedimentary cover in the lower part of the section repeats the relief of the foundation in its occurrence. Its upper horizons practically do not reflect the surface of the foundation.

The sedimentary rocks of the cover are represented by sands, sandstones, clays, mudstones, etc. The thick sedimentary cover formed tens of millions of years over six geological periods (240 million years).

During this time, the earth's crust experienced slow vertical vibrations. When it sank, sea waters flooded vast areas. In the resulting warm seas, a rich organic world, promoting the formation of marine sedimentary strata. Then the subsidence of the earth's crust was replaced by an uplift, the sea became shallow and gradually disappeared, the territory of the region became a flat land with numerous lakes and rivers. Ground vegetation was widely developed. These events were repeated several times.

Over the entire geological history of the formation of the West Siberian plate, a sedimentary cover was formed here, the thickness of which varies from 3000-3500 m in the north to 500-1000 m at the southern border of the region. The upper part of the cover (250-300 m) is composed of a sequence of continental Upper Paleogene-Neogene clays, loams and sands. Outcrops of these rocks are exposed along the banks of the river. Irtysh and its tributaries (Fig. 3), as well as in large lake basins. Most often, these deposits are overlain by thin Quaternary deposits.

Each geological period of time in the history of the region is marked by characteristic natural conditions and geological processes. To answer the question of what happened in the distant past, it is necessary to travel through the geochronological table (Table 1).

Table 1

GEOCHRONOLOGICAL TABLE

Eras	Periods (duration, million years)	Major geological events	Natural conditions	Organic world	Rock formation
KAYNOZOYSKAYA	Quaternary (anthropocene) 1.8	Repeated glaciations in the north of the West Siberian Plain, which influenced the natural conditions of the Omsk region.	Repeated flooding, formation of glacial lakes. At the maximum of glaciation, in the north of the region there was tundra, to the south of it there was forest-tundra, then forest-steppe.	Animals included mammoth, woolly rhinoceros, bison, and giant deer. The vegetation is close to modern.	Cover loams, sands, sandy loams, loams. Peat, lake sapropel.
Neogene (Neogene) 22.8	Slow vertical movements of the earth's crust - uplifts. Intensive development of rivers.	At the beginning of the Neogene, the plain was covered with coniferous-deciduous forests. The climate is moderately warm and humid. Towards the end of the period the temperature and humidity decrease. Forest-steppe and steppe appear.	Small-leaved tree species are becoming widespread. The animal world – mastodons, proboscis, ancient horses, rhinoceroses, hippopotamuses, saber-toothed tiger, etc. The emergence of man.	Sands, sandy loams, loams, clays, nodules, and lignites formed in lakes, swamps and rivers. Neogene rocks are found in the cliffs of the Irtysh, Om, Tara, etc. rivers.
KAYNOZOYSKAYA	Paleogene (Paleogene) 40.4	At the beginning of the Paleogene, there was a short rise of the earth's crust, and then a long subsidence and the advance of the sea onto the land. At the end of the period, the subsidence gave way to rising and retreat of the sea.	The Paleogene sea existed in the region for almost 30 million years. At the end of the Paleogene, the mora shallowed and broke up into lake basins. The resulting land was covered with coniferous and deciduous forests with an admixture of heat-loving plants. The climate is warm and humid.	Marine fauna predominates; The Paleogene sea is inhabited by mollusks, fish, simple animals - radiolarians, diatoms, etc. on land there is a flourishing of ungulates and predators.	Clays with layers of sand accumulated at the bottom of the sea. On land, in lakes - clays, silts, sands, brown coals
Mesozoic	Cretaceous (chalk) 79.0	With the onset of the Cretaceous period, the slow uplift of the earth's crust and the retreat of the sea began. In the second half of the Cretaceous, the earth's crust sank and the entire region was flooded by the sea.	In the first half of the Cretaceous, the region was a flat land covered with coniferous forests. The forests grew: pine, spruce, cedar and heat-loving tropical plants. The climate is subtropical, humid. Subsequently, a warm sea existed on the territory of the region, the water temperature was 20°C. At times, a cold current penetrated from the north and the water temperature dropped.	The sea was inhabited by cephalopods, fish and other animals, and various algae.	In lakes and rivers, thick strata of predominantly sands and sandstones were formed, to which underground thermal waters are confined. Various clays were formed in the sea - siliceous, calcareous.
Jurassic (Jurassic) 69.0	There was a slow subsidence of the earth's crust, which reached its maximum in the Late Jurassic era. This subsidence caused the advance of the sea.	In the first epochs of the Jurassic period, the region was represented by a low-lying plain with numerous lakes and rivers. The climate is warm and humid. In the Late Jurassic era, the entire area was occupied by a sea that existed for 25 million years.	The sea was inhabited by numerous cephalopods - ammonites, belemnites, fish, and algae. Conifers, ginkgo and other plants are widespread on land.	Sedimentary rocks accumulated in lakes and rivers - clays and sands, which later turned into mudstones and sandstones. The rocks contain a lot of plant remains and a layer of coal. Clays deposited in the sea contain a large amount of organic substances, from which hydrocarbons (oil and gas) can be formed.
Triassic (Triassic) 35.0	Slow vertical uplifts of the earth's crust. Intensive destruction and erosion of rocks. Volcanism in places.	Elevated plain. There were extensive forests. The climate is hot and arid.	The forests are dominated by gymnosperms.	Deposits are rare. Mudstones, siltstones, sandstones. Volcanic rocks are diabases.
Paleozoic	Perm (Perm) 38.0	General rise of the region. The entire territory is a single stable platform that connected the Siberian and Russian platforms.	An area of ​​plateaus and highlands with developed erosion processes. The climate is hot and arid.	On land, the development of terrestrial reptiles, conifers, and the appearance of ginkgos. At the end of the period, trilobites and four-rayed corals became extinct. some mollusks and brachiopods.	Clastic material supplied from surrounding mountain structures.
Hard coal (carbon) 74.0	A time of relatively quiet tectonic activity. Subduction of the territory and transgression of the sea. At the end of the period there was a general uplift of the earth's crust. Sea regression. No volcanic activity has been observed.	The sea is shallow, open, warm with a normal hydrochemical regime. At the end of the period, a large area was drained, a low plain.	The first reptiles. Tree ferns, horsetails and mosses, the first gymnosperms. Widespread distribution of large insects. In the seas there are bony and cartilaginous fish and invertebrates.	Volcanogenic and normal sedimentary marine rocks of all types.
Devonian (Devonian) 48.0	The regional uplift of the territory caused cracking of the earth's crust, revitalization of deep faults and an outbreak of volcanism.	The land is a desert, on the southern edge of which there were volcanoes.	Wide distribution of bony and cartilaginous fish. On land the tree contains prominent ferns, horsetails and mosses. The appearance of the first terrestrial aquatic animals and insects.	Volcanogenic sedimentary rocks. clays, sands, limestones.
Silurian (Silurian) 30.0	The West Siberian Platform is a continuation of the Siberian Platform. Active tectonic processes are observed on it.	Noticeable restructuring of paleolandscapes. At the beginning of the period, the territory is dominated by mountainous land, at the end there is a flat desert plain.	The first land plants (psilophytes). In the seas there are graptolites, corals, brachiopods, trilobites.	Terrigenous sediments, salt-bearing and gypsum-bearing, are likely.
Ordovician (Ordovician) 67.0	Deflection of the earth's crust.	The seas are warm and normally salty with numerous islands and underwater volcanoes.	The appearance of the first fish. The flourishing of trilobites and corals. On seabed bryozoans and graptolites are found.	Effusional and terrigenous formations.
Cambrian (Cambrian) 65.0	Most of the territory of Western Siberia has lost the features of a geosyncline. A para-platform was formed.	Bring sea transgression! to the dismemberment of land. Widespread areas of underwater volcanism. The sea is shallow with high salinity.	Wide distribution of marine invertebrates: trilobites, archaeocyaths, quadruple corals. Active development of blue-green algae.	Effusional and terrigenous formations.
Proterozoic	>2000	The Ural-Siberian geosynclinal belt occupies the entire space between the Siberian and Russian platforms. Active tectonic processes and volcanism.	Sharply dissected relief.	The appearance of the first plants - algae and invertebrates, sponges, radiolarians, brachiopods, arthropods. worms	Clayey and carbonate sediments and effusive rocks predominate.

Questions and assignments.

THE USSR. Geological structure

The largest elements of the structure of the earth's crust on the territory of the USSR: the East European and Siberian platforms and the folded geosynclinal belts separating them - the Ural-Mongolian, separating the East European platform from the Siberian and encircling the latter from the south; Mediterranean, bordering the East European Platform from the south and south-west; Pacific, forming the edge of the Asian continent; part of the Arctic, located within the northern coast of the Chukotka Peninsula. Within the folded geosynclinal belts there are: young areas that have not yet completed geosynclinal development, which are active modern geosynclines (the peripheral part of the Pacific belt); areas that completed geosynclinal development in the Cenozoic (the south of the USSR, belonging to the Alpine geosynclinal folded region), and more ancient areas that form the foundation of young platforms. The latter, depending on the time of completion of the processes of geosynclinal development, folding and metamorphism of sedimentary strata, are divided into folded regions of different ages: Late Proterozoic (Baikal), Middle Paleozoic (Caledonian), Late Paleozoic (Hercynian, or Variscan) and Mesozoic (Cimmerian). The geosynclinal type of structure of the earth's crust appears at earlier stages of development. Subsequently, geosynclinal areas turn into platform foundations, which are then covered in subsided areas by a cover of platform sediments (platform slabs). Thus, in the process of development of the earth's crust, the geosynclinal stage is replaced by the platform stage with a two-story structure typical of platforms. During the formation of the platform foundations, the oceanic crust of geosynclinal belts is transformed into continental crust with a thick granite-metamorphic layer. In accordance with the age of the foundation, the age of the platforms is determined. The foundation of ancient (Precambrian) platforms was formed mainly by the beginning of the Riphean (Late Proterozoic). Among the young platforms, they are distinguished: epi-Baikal (the Upper Proterozoic is involved in the structure of the basement, and Paleozoic, Mesozoic and Cenozoic rocks are developed in the cover), epi-Paleozoic (the basement was formed in the Paleozoic, and the cover - in the Mesozoic - Cenozoic) and epi-Mesozoic (Mesozoic rocks are involved in the structure of the basement ).

Some areas of ancient platforms and geosynclinal belts, which turned into young platforms, in the course of further evolution turned out to be covered by repeated processes of orogenesis (epiplatform orogenesis), which manifested itself many times in Siberia (Stanovoy Range, Western Transbaikalia, Sayan Mountains, Altai, Gissar-Alai, Tien Shan and etc.).

The structural areas of land directly continue on the bottom of the shelf seas bordering the north, east, and partly north-west. territory of the USSR.

Ancient platforms. The East European Platform includes 2 basement projections on the surface - the Baltic Shield and the Ukrainian Crystalline Massif - and the extensive Russian Plate, where the basement is submerged and covered by sedimentary cover. The structure of the basement involves Archean, Lower and Middle Proterozoic strata. Archean rocks form numerous massifs, within which two rock complexes of different composition and age are distinguished. More ancient rocks (over 3000 million years ago) compose the lower horizons of the Kola series (biotite and amphibole gneisses and amphibolites) on the Kola Peninsula, and in the Dnieper section of the Ukrainian massif (between Zaporozhye and Krivoy Rog) rocks of the Konsko-Verkhovtsev series are similar in composition . In Podolia and the Bug basin, the oldest rocks are represented by pyroxene-plagioclase garnet gneisses and charnockites. The younger Archean complex (from 2600 to 3000 million years) consists of thick series of biotite, two-mica, amphibole gneisses, amphibolites, crystalline schists, quartzites, and marbles. This complex is typically expressed along the shores of the White Sea (Belomorskaya series). The processes of metamorphism to which the rocks of the White Sea complex were subjected at the beginning of the Proterozoic were accompanied by the formation of granite massifs and migmatites.

Archean massifs are separated by bands of Lower Proterozoic (from 1900 to 2600 million years) folded structures composed of gneisses, crystalline schists, quartzites and diabases, which were subjected to strong folding and granitization at the end of the Early Proterozoic and repeated (superimposed) metamorphism in the Middle and in some places Late Proterozoic ( 1750-1600 and 1500-1350 million years).

Middle Proterozoic rocks on the Baltic shield and the Ukrainian massif lie unconformably and are represented by quartzites, phyllites, diabases, and dolomite marbles (Jatulian of Karelia, Iotnian of Finland, Ovruch series of Ukraine). These strata are characterized by products of metamorphism of kaolin weathering crusts, which could have formed in a quiet tectonic environment. They represent deposits of the most ancient Middle Proterozoic cover, after the accumulation of which large massifs of porphyritic rapakivi granites occurred (1670-1610 million years). These are the youngest granite intrusions in the platform basement.

The depth of the foundation on the Russian plate varies from several hundred m(on elevations) up to several thousand. m(in the depressions). The largest uplifts are the Voronezh, Belorussian and Volga-Ural anteclises. Among the depressions, the Moscow, Baltic, and Caspian syneclises stand out. The submerged parts of the platform adjacent to the Urals, the Timan Ridge, and the Carpathians correspond to pericratonic subsidence (See Pericratonic subsidence) (Pritimansky, Kama-Ufa, Transnistrian). A special type of structures - aulacogens , often forming entire systems. The largest system of aulacogens is the Central Russian one, stretching from Valdai to Pritimanye. In the northern, western and central parts of the Russian Plate, the Orsha-Kresttsovsky, Moscow, Ladoga and Dvina aulacogens are established, in the east - the Pachelmsky, Kazhimsky, Verkhnekamsky, etc. The largest aulacogen of the East European Platform is the Pripyat-Dnieper-Donetsk. Aulacogens and pericratonic troughs are the oldest depressions of the Russian plate. The aulacogens are filled with Riphean sediments. The pericratonic troughs are composed of Riphean and Vendian deposits.

The eastern part of the Pripyat-Dnieper-Donets aulacogen was founded in the Riphean, but as a separate structure it formed in the Devonian. Carboniferous and Permian deposits in its eastern part (Donetsk coal basin) are folded.

The rocks filling the syneclises range in age from the Vendian to the Cenozoic and form the upper floor of the structures of the Russian Plate. The largest anteclise, the Moscow one, separates the protrusion of the foundation of the Baltic Shield in the north from the Voronezh and Volga-Ural anteclises in the south and southeast. In its axial part, Triassic and Jurassic rocks are developed, on the wings - Permian and Carboniferous. The foundation in its central part is immersed to a depth of 3-4 km. The horizontal position of the cover on the wings is complicated by flexures. The deepest is the Caspian depression (on the south-eastern platform), the thickness of its sedimentary cover exceeds 20 km, the structure of the foundation and lower horizons of the cover is unknown; According to geophysical data, the basement rocks in the center of the depression are characterized by increased density, close to the density of basalt, and the structure of the cover is complicated by numerous domes of Permian salt.

Vendian and Cambrian deposits are developed in the Moscow and Baltic syneclises and in pericratonic troughs (Transnistria). They are represented by clays with sandstone units and, in some places, tuffs. Ordovician and Silurian deposits are common on the western platform (clayey shales with graptolites and limestones). The Ordovician includes oil shales - kukersites. Devonian deposits (clayey-carbonate, gypsum-bearing and salt-bearing) are developed everywhere on the Russian Plate; Volcanic tuffs and diabases are known in them near faults; The eastern platforms are characterized by bituminous limestones and clays. Carboniferous deposits are mainly represented by limestones and dolomites. The Lower Carboniferous is associated with a coal-bearing formation. In the Donetsk basin, carbon forms a powerful (up to 18 km) a series of sandstones, limestones, clays, alternating with layers of coal. Permian and Triassic deposits are common in syneclises (clastic rocks, dolomites, gypsum). Large reserves of rock salt are associated with Lower Permian deposits. Jurassic and Lower Cretaceous deposits in the central regions of the platform are represented by characteristic dark clays and glauconitic sands with phosphorites. In the section of widespread Upper Cretaceous deposits in the southern regions, marls and chalk are developed; in the north there are many clayey-siliceous rocks. Marine sandy-clayey Cenozoic deposits are found in the southern part of the Russian Plate.

The Siberian platform has an ancient, predominantly Archean basement, the highly metamorphosed rocks of which (gneisses, crystalline schists, marbles, quartzites) are exposed within two basement ledges (Anabar massif and Aldan shield). Among the Archean rocks, there are Lower Archean rocks (Iengra series, etc.), which make up several large massifs, and younger Upper Archean rocks, framing ancient massifs (Timpton, Dzheltulinskaya series, etc.); on the Aldan shield and the Stanovoy uplift, the basement rocks are intruded by Precambrian, Paleozoic and Mesozoic intrusions of granites and syenites. The Lower Archean complexes form dome-shaped folded structures, the Upper Archean complexes form large systems of linear folds in the northwest. prostrations. Under the sedimentary cover within the Central Siberian Plateau, according to aeromagnetic survey data, submerged ancient massifs (Tunguska, Tyunga) are established, which are framed by folded systems of the Upper Archean.

In the area of ​​distribution of the cover there are several platform deflections and uplifts. The northwestern part of the platform is occupied by the Paleozoic Tunguska syneclise. In the east there is the Mesozoic Vilyui syneclise, which opens into the deep Verkhoyansk Upper Jurassic-Cretaceous trough, separating the Siberian platform from the Verkhoyansk-Chukotka region of Mesozoic folding. The Mesozoic Khatanga and Leno-Anabar depressions stretch along the northern edge of the platform. The relatively elevated block between the listed troughs forms the complex Anabar anteclise with outcrops of Proterozoic and Cambrian sediments. On the southern platform, along the upper reaches of the river. Lena, there is an elongated shallow Angara-Lena trough filled with Cambrian (with a layer of rock salt), Ordovician and Silurian deposits. The southeastern edge of the trough is characterized by a system of ridge-like folds and faults; in the north it is separated from the Tunguska depression by the Katanga uplift. Near the southern border of the platform there is a series of depressions with coal-bearing Jurassic deposits: Kanskaya and Irkutskaya - along the northern spurs of the Eastern Sayan; Chulmanskaya, Tokkinskaya and others - in the south of the Aldan shield.

The platform cover includes deposits of the Upper Proterozoic, Paleozoic, Mesozoic and Cenozoic. The Upper Proterozoic sediments include thick strata of sandstones and algal limestones. Cambrian deposits are widespread, absent only on shields. Ordovician and Silurian deposits are known in the western and central parts. Devonian and Lower Carboniferous - marine carbonate-terrigenous strata in the north and east, continental - in the south. In the river basin. Vilyuy they contain basic tuffs and lavas.

Continental coal-bearing deposits of the Middle and Upper Carboniferous, Permian, as well as thick tuffaceous and lava series of the Triassic (Siberian traps) fill the Tunguska syneclise. Numerous trap intrusions are developed along its margins, on the slopes of the Anabar anteclise and in the southern regions of the platform, forming linear zones along faults cutting the foundation and sediments of the cover. In addition to the Upper Paleozoic trap intrusions and age-matched explosion pipes with kimberlites, similar Devonian and Jurassic igneous bodies are known. The Jurassic-Cretaceous Vilyui syneclise overlies Paleozoic aulacogens. Mesozoic deposits are represented by clastic rocks with interlayers of brown coals and limestones (in the north).

The Siberian platform, in contrast to the East European one, at the end of the Proterozoic and the beginning of the Paleozoic was an area of ​​general subsidence and almost universal accumulation of marine, which means. degree of carbonate deposits. In the 2nd half of the Paleozoic, in the Mesozoic and Cenozoic, it was relatively uplifted and mainly continental sediments accumulated on it. The Siberian platform is characterized by a high degree of tectonic activity. It has many faults crossing the cover and flexures, and mafic and alkaline magmatism is widespread.

Folded geosynclinal belts. By the beginning of the Mesozoic, the Ural-Mongolian belt acquired the structure of a platform, the base of which is formed in different areas by folded systems of different ages: Baikal and Salair, Caledonian, Hercynian. The cover on the Baikalids and Salairids is formed by Paleozoic, Mesozoic and Cenozoic sediments (on the Hercynides - only Mesozoic and Cenozoic). Paleozoic and Precambrian rocks come to the surface in the basement ledges (modern mountain regions of the Urals, Tien Shan, Central and Eastern Kazakhstan, Altai, Sayan, Transbaikalia, Taimyr, etc.). The sedimentary cover covers the foundation within the Timan-Pechora, West Siberian, northern Turan and Bureinskaya plates.

The structures of the Baikal folding zone form an arc that goes around the Siberian platform from the north-west. and southwest, and come to the surface in Northern Taimyr, the Yenisei Ridge, Eastern Sayan and the Baikal region. Under the cover of the eastern margins of the West Siberian plate, the Baikal structures stretch along the left bank of the river. Yenisei. The Baikal region also includes the Bureinsky massif in the Amur, Zeya and Bureya basins, partially covered by sedimentary cover, as well as the area stretched along the northeastern edge of the East European Platform (Timan Ridge, the foundation of the Pechora syneclise). In the structure of the areas of Baikal folding, the main role is played by thick Precambrian, especially Upper Proterozoic strata, folded into complex linear folds. They are represented by various types of sedimentary and sedimentary-volcanogenic geosynclinal formations. Upper Riphean, in places Vendian, clastic accumulations belong to molasse. Large massifs of granitoids of the late Riphean - Vendian are widespread, but younger alkaline intrusions (Devonian, Jurassic - Cretaceous) are also found.

The Baikalids of the Eastern Sayan are adjacent to the west and east by structures of the Early Caledonian or Salair folding, in the structure of which the most important role is played by powerful marine and volcanic geosynclinal strata of the Upper Proterozoic, Lower and Middle Cambrian, forming linear folds. The Salairid molasse complex begins in the Upper Cambrian, which is represented by red-colored clastic accumulations. The role of Salair folding and intrusive granptoid magmatism in areas previously classified as Baikal (Baikal-Vitim Plateau, etc.) is significant. The areas of Caledonian folding cover part of Altai and Tuva, as well as the Northern Tien Shan and Central Kazakhstan. Cambrian and Ordovician sedimentary and sedimentary-volcanogenic rocks, folded into linear folds, are widely developed in the structure of the Caledonides. In the cores of the anticlinoriums and on the massifs, the Precambrian is exposed. The Silurian and younger deposits are usually represented by molasse and terrestrial volcanics. In some places (Northern Tien Shan), Caledonian structures are melted by huge massifs of Lower Paleozoic (Ordovician) granitoids.

The areas of the Baikal, Salair and Caledonian folds are characterized by large intermountain depressions (Minusinsk, Rybinsk, Tuva, Dzhezkazgan, Teniz), filled with marine and continental, often molasse formations of the Devonian, Carboniferous and Permian. The depressions are superimposed structures, but some (Tuva) follow the largest deep faults.

The Hercynian folded regions include the Urals with the Pre-Ural foredeep, the Gissar-Alai and part of the Tien Shan (Turkestan, Zeravshan, Alai, Gissar, Kokshaltau ridges), the Balkhash part of Central Kazakhstan, the region of Lake Zaisan, Rudny Altai and a narrow strip of eastern Transbaikalia, sandwiched between the edge of the Siberian platform and the Bureinsky massif (Mongol-Okhotsk fold system). The Hercynian fold structures are formed mainly by marine geosynclinal sedimentary and volcanogenic formations of the Lower Paleozoic, Devonian and Lower Carboniferous, collected in linear folds and often composing extensive tectonic nappes. Precambrian metamorphic rocks within their boundaries come to the surface in the cores of anticlinoria. In some intermountain depressions they are overlain by continental molasse of the upper Carboniferous and Permian. Sedimentary and volcanogenic rocks in the Hercynian regions are intruded by large granite massifs (Upper Carboniferous - Permian). Late Paleozoic (Hercynian) intrusions were also developed in areas of earlier folding eras.

Within the vast area of ​​the plates of the Ural-Mongolian belt, the foundation is composed of the same folded systems as in the mountainous regions, but they are covered by a sedimentary cover. The basement includes individual Late Proterozoic (Baikal) massifs, which are bordered by younger Caledonian and Hercynian systems of structures. The main role in the structure of the plate cover is played by Jurassic, Cretaceous, Paleogene, Neogene and Anthropogene rocks, represented by marine and continental sedimentary rocks. Continental, volcanogenic and coal-bearing deposits of the Triassic - lower Jurassic form separate grabens (Chelyabinsk and others). The complete section of the cover on the West Siberian plate is represented below by continental coal-bearing deposits (Lower and Middle Jurassic), marine clay-sandstone strata of the Upper Jurassic - lower part of the Cretaceous, continental strata of the Lower Cretaceous; marine clay-siliceous strata of the Upper Cretaceous - Eocene, marine clays of the Oligocene. Neogene and anthropogenic deposits are usually continental. The Mesozoic-Cenozoic cover lies almost horizontally, forming separate arches and troughs; Flexures and faults are observed in places (see West Siberian oil and gas basin).

Within the Ural-Mongolian belt, Neogene processes of epiplatform orogenesis appeared, due to which the foundation is often curved and split into separate blocks raised to different heights. These processes occurred most intensively in Gissar-Alai, Tien Shan, Altai, Sayan Mountains, the Baikal region and Transbaikalia.

The Mediterranean belt is located to the southwest. and S. from the East European Platform. Along the Gissar-Mangyshlak deep fault, its structures are in contact with the structures of the Ural-Mongolian belt. The Mediterranean belt on the territory of the USSR includes external and internal zones. The outer zone (Scythian plate, southern part of the Turanian plate, Tajik depression and Northern Pamir) is a young platform. Within its boundaries, the Mesozoic and Cenozoic forms a gently lying platform cover on a folded, metamorphosed and intruded Paleozoic and Precambrian foundation. The Tajik depression and the Northern Pamirs in the Neogene - Anthropocene were covered by orogenesis, as a result of which the Mesozoic and Cenozoic deposits of the platform cover were folded here.

The Scythian plate, which includes the lowland territories of Crimea and Ciscaucasia, has a foundation that includes blocks of Upper Proterozoic rocks (fragments of Baikal structures), welded together by folded geosynclinal Paleozoic. On the Baikal massifs there is a cover of gently lying Paleozoic sediments, intruded by late Paleozoic intrusions. The platform cover everywhere includes sediments from Cretaceous to anthropogenic. The lower horizons of the cover (Triassic - Jurassic) are not developed everywhere - they often occur in grabens. In some places they are dislocated, broken through by intrusions (Kanev-Berezan folds North Caucasus, Tarkhankut folds of Crimea). In the structure of the cover, clayey-sandy strata (Lower Cretaceous, Paleogene) and marl-chalk strata (Upper Cretaceous) are developed. They make up a series of depressions and ledges, on which the largest are the Stavropol arch, the Simferopol ledge, the Kum and Azov depressions. The depth of the base of the cover on elevations is 500 m, in deflections up to 3000-4000 m.

The southern part of the Turan Plate has a foundation consisting of a number of Precambrian massifs (Central Karakum, Kara-Bogaz, North Afghan, etc.), covered by a cover of rocks (Carboniferous, Permian and Triassic in age), which is broken through by Late Paleozoic intrusions. The massifs are separated by Paleozoic fold systems (Tuarkyr, Mangyshlak, Nuratau). Large graben-shaped depressions in the basement are filled with dislocated marine terrigenous and volcanogenic Triassic sediments (Mangyshlak, Tuarkyr, Karabil). The slab cover as a whole is formed by a series of sediments from the Jurassic to the Anthropocene. The thickest cover is developed in the southeast, in the Murgab and Amudarya depressions. The central part of the plate is occupied by a large uplift - the Karakum arch; to the west there are elevated zones - the Tuarkyr meganticline and the Kara-Bogaz arch. The Mangyshlak system of uplifts stretches along the northern border, from the Caspian to the Aral Sea. The folded structures observed in the cover are caused by faults in the basement.

The internal zone of the Mediterranean belt (Carpathians, Mountain Crimea, Caucasus, Kopet Dag, Middle and Southern Pamirs) is distinguished by the fact that Mesozoic and Cenozoic deposits in it are represented by a geosynclinal type of formations. The separation of the outer and inner zones began from the Late Triassic - Jurassic.

The Ukrainian Carpathians form part of the Carpatho-Balkan arc. On the territory of the USSR it is formed mainly by Cretaceous and Paleogene flysch series. A subordinate role is played by the projections of the base of geosynclinal complexes (Lower Mesozoic, Paleozoic and Precambrian). The Carpathians are characterized by a complex folded structure with numerous thrusts. The Eastern Carpathians are separated from the East European Platform by the deep Ciscarpathian foredeep, over which they are thrust.

Mountain Crimea is a separate anticlinal structure, the southern wing of which is submerged below the level of the Black Sea. In the core of the Crimean anticlinal uplift, sandy-clayey, carbonate and volcanic deposits of the geosynclinal type (Upper Triassic, Jurassic, partially Lower Cretaceous) are exposed. The northern wing is formed by gently lying Cretaceous-Paleogene rocks of the platform type. The main manifestations of intrusive and effusive magmatism belong to the Middle Jurassic (diorites, granodiorites, gabbros, spilites, keratophyres, etc.).

The complex folded structure of the meganticlinorium of the Greater Caucasus is formed by geosynclinal complexes of the Paleozoic, Mesozoic and Paleogene of different compositions, disturbed by numerous faults and intruded by intrusions of different ages. Metamorphic rocks of the Upper Precambrian are exposed in the cores of the most uplifted structures. Precambrian and Paleozoic rocks make up the pre-Alpine basement, the Mesozoic and Paleogene - Alpine geosynclinal complex; its thickness reaches its maximum along the southern slope of the Greater Caucasus. The structure of the meganticlinorium is asymmetrical. Sandy-clayey and carbonate rocks of the Jurassic, Cretaceous, Paleogene on its northern wing lie predominantly flat, monoclinal; on the southern wing they lie steeply, crumpled into folds complicated by thrusts. Upper Jurassic-Paleogene deposits on the west and east of the southern wing are represented by flysch series. To the north of the Greater Caucasus are the Indolo-Kuban and Terek-Caspian marginal troughs of Neogene age, and to the south is the Riono-Kura zone of intermontane depressions, separating the meganticlinoria of the Greater and Lesser Caucasus. In the geological structure of the Lesser Caucasus, the main role belongs to sedimentary-volcanogenic formations of the Jurassic, Cretaceous and Paleogene ages (including ophiolite complexes). The structure of the Lesser Caucasus is block. Large areas are covered by thick, gently sloping lavas of Neogene and Anthropogenic age.

The Kopet Dag is a relatively simply constructed folded structure formed on the surface by carbonate-clay complexes of Cretaceous and Paleogene ages with folds tilted northward towards the Pre-Kopet Dag trough, separating the Kopet Dag from the Turan Plate. To the north-west from the Kopetdag, on the continuation of the Kopetdag regional deep fault, there is the Greater Balkhan meganticline with outcrops in the core of the geosynclinal Jurassic rock complex. The wings of the meganticline are formed by Cretaceous and Paleogene deposits of the platform type. Within the Central Pamirs, sedimentary geosynclinal complexes of Paleozoic and Mesozoic ages, collected in complex folds complicated by thrusts, are developed, and in the Southern Pamirs - Precambrian metamorphic rocks and large massifs of granites of various ages.

The Pacific belt covers the territory east of the Siberian Platform and the Bureya Massif. Its eastern border is the system of the Kuril-Kamchatka and Aleutian deep-sea trenches. The general orientation of the belt is close to meridional. The Pacific belt includes the Mesozoic folded regions (Verkhoyansk-Chukotka and Sikhote-Alin) and the structures of the modern geosynclinal region - geoanticlinal uplifts (Kamchatka, Sakhalin, Kuril Islands), as well as depressions marginal seas(Japanese, Okhotsk and Bering).

The Verkhoyansk-Chukotka folded region occupies the north-east. THE USSR. Within its boundaries, Permian, Triassic and Jurassic sediments are most widely developed (on the surface), forming several anticlinal and synclinal zones. The geosynclinal complex (cf. Carboniferous - Upper Jurassic) is formed by a thick series of marine clayey-sandstone deposits, among which volcanic rocks occupy a subordinate place. The largest will put. The structures of the region are the Verkhoyansk meganticlinorium, the Sette-Daban anticlinorium, Anyuisky, Chukotsky, Tas-Khayakhtakhsky, Momsky, Polousnensky, etc. In the structure of the last three, an important role belongs to the mesozoid base complex. The most important negative structure is the Yana-Indigirka (Yana-Kolyma) synclinor zone, composed of Triassic-Jurassic deposits on the surface. The molasse orogenic complex (Upper Jurassic - Lower Cretaceous), largely carbon-bearing, fills the Verkhoyansk marginal trough, as well as several large internal inherited troughs and intermountain depressions (Oldzhoyskaya, Momsko-Zyryanovskaya). An important role in the structure of the region belongs to the protrusions of the base, in some places covered by a cover of Paleozoic and Mesozoic sediments (Kolyma, Okhotsk, Omolon, Chukotka and other massifs). Late Jurassic - Early Cretaceous and Late Cretaceous - Paleogene granitoids form batholiths along deep fault zones. Upper Cretaceous - Cenozoic (post-geosynclinal) complex is developed to a limited extent; composed mainly of continental coal-bearing and volcanic series. In the lower reaches of the river. Yana, Indigirka, Kolyma, Cenozoic rocks cover geosynclinal and orogenic structures with a cloak, forming a platform cover lining the shelves of the Laptev and East Siberian seas.

The Sikhote-Alin folded region differs from the Verkhoyansk-Chukotka region in the wide distribution of volcanogenic-siliceous strata of the Middle and Upper Paleozoic and Mesozoic, as well as the later completion of geosynclinal sedimentation (2nd half of the Late Cretaceous). At the end of the Cretaceous and in the Cenozoic, the Sikhote-Alin region underwent orogenesis with the accumulation of clastic and volcanic rocks.

Mesozoic structures are separated from the modern geosynclinal region located to the east by a system of deep faults, which controlled volcanic eruptions and the introduction of intrusions throughout the Late Cretaceous and Cenozoic. The position of the faults corresponds to the Okhotsk-Chukotka and East Sikhote-Alin marginal volcanic belts - zones of development of Cretaceous and Paleogene effusives.

The modern geosynclinal region includes the Koryak Highlands, the Kamchatka Peninsula, the Kuril and Commander Islands, and Sakhalin and the bottom of the adjacent seas - Bering, Okhotsk, Japan. The eastern border of the region is the deep-sea Kuril-Kamchatka Trench, separating the modern geosynclinal region from the depression Pacific Ocean The location of the trench corresponds to the emergence to the surface of a zone of deep-focus earthquakes (the Zavaritsky-Benioff zone), associated with the largest deep faults in the earth's crust and upper mantle.

The island ridges are considered positive. geosynclinal structures (geoanticlines), deep-sea basins (Bering Sea, South Kuril) and deep-sea trenches (Kuril-Kamchatka, Aleutian) are negative structures (geosynclinal troughs), in the section of the earth’s crust there is no “granite” layer. Part of the bottom of the Sea of ​​Okhotsk and the Sea of ​​Japan is a submerged rigid middle massif among linearly elongated geosynclinal troughs and geoanticlinal uplifts. Most of the modern geosyncline Far East is an area of ​​sedimentation and is characterized by active seismicity and intense volcanism (volcanoes of Kamchatka and the Kuril Islands). The main role in the geological structure is played by thick sedimentary and volcanogenic-sedimentary complexes of Cretaceous, Paleogene and Neogene ages, as well as anthropogenic deposits collected in systems of folded structures. More ancient rocks are Triassic-Jurassic in age. Metamorphic complexes of the Paleozoic and Mesozoic are developed in Kamchatka. On the Kuril Islands, the most ancient are Upper Cretaceous volcanics and sandy-clayey deposits. Cm. cards.

M. V. Muratov, V. M. Tseysler, E. S. Chernova, E. A. Uspenskaya.

Features of their occurrence. Using various signs, he reconstructs geological events that occurred in the past. The occurrence of rocks is best observed in cliffs on a river or sea bank, on the sides of a ravine, on steep mountain slopes - wherever there are natural or artificial (quarries) outcrops of rocks on the earth's surface - outcrops.

Sands, clays, limestones and other sedimentary rocks usually lie in layers or layers, each of which is limited by two approximately parallel surfaces: the upper one is called roof, lower - sole. The formation has an approximately homogeneous composition. The thickness (thickness) reaches tens and hundreds of meters. Over large areas of the plains, strata usually lie horizontally, as they were originally deposited: each overlying strata is younger than the underlying one. This occurrence called undisturbed. Movements of the earth's crust often disrupt the original position of the layers, and they lie obliquely or are crushed into folds.

But it often happens that undisturbed layers are located disagree- horizontal layers lie on disturbed strata, crumpled into folds, the surface of which has been eroded and leveled. Then younger horizontal layers lay on this surface. Arose angular disagreement. This structure indicates complex and variable movements of the earth's crust. There is also stratigraphic unconformity, in which the parallelism of the layers is preserved, but their sequence is disrupted (there are no layers of any precisely determined geological age). This means that at this time the area came out from under sea level and, therefore, there was a break in sedimentation.

When the layers are inclined, it is important to determine the conditions under which the sedimentary rock strata occurs (the position of the layer in space). Each layer has stretch, i.e. length, and a fall, or slope. Strike and fall are the main elements of rock occurrence. To determine them, a flat area is selected on one of the formations in the outcrop, a mountain compass is placed on it with its edge, and the angle of incidence of the formation is measured. A line is drawn along the long edge of the compass die on the layer. This will be the dip line of the formation. If you draw a perpendicular line, it will show the strike of the formation. A right angle will be drawn on the surface of the formation. Now you should raise the compass to a horizontal position and measure the azimuth of the fall at the northern end of the magnetic needle. The strike is perpendicular to it, therefore, by adding or subtracting 90° from the dip azimuth, the strike azimuth is obtained. For example, the dip azimuth NE is 40°, then the strike azimuth SE is 130° (40°+90°). If the NE dip azimuth is 300°, then 90° is subtracted and the SW strike azimuth is obtained (300°−90°). To determine the angle of dip of the strata, the compass is equipped with a plumb line and a scale (protractor). The angle of incidence is determined by the inclination of the protractor: 20°, 30°, etc.

The sequence of occurrence, and therefore the formation of rock layers, studies stratigraphy- a special branch of geology. Layers of the same age are traced, their age is established, deposits of the same age are compared in different areas, etc. If, for example, in an outcrop there are limestones below and clays above, then it is obvious that the limestones formed earlier and, therefore, in age they more ancient than clay.

For a visual representation of the geological structure of a site or region, based on data obtained from studying rock outcrops or drill holes, they build stratigraphic column, i.e. a graphic representation of the sequence of occurrence of rocks of various ages in a given area or area. Conventional signs in the column depict rocks in the sequence in which they occur; their age, the thickness of each layer, the composition of its constituent rocks, as well as angular and stratigraphic unconformities are noted. The stratigraphic column, like the geological section, serves as an important addition to the geological map.

The area is located in the central part of the Moscow syneclise. Its geological structure includes highly dislocated crystalline rocks of Archean and Proterozoic age, as well as a sedimentary complex represented by deposits of the Riphean, Vendian, Devonian, Carboniferous, Jurassic, Cretaceous, Neogene and deposits of the Quaternary system.

Due to the fact that the description of this territory is based on the existing hydrogeological map of a scale of 1: 200,000, the geological structure of the area is given only up to the Moscow stage of the Carboniferous system.

Stratigraphy and lithology

The modern erosion network has exposed Quaternary, Cretaceous, Jurassic deposits and rocks of the upper and middle sections of the Carboniferous system (Appendix 1).

Paleozoic erathema.

Coal system.

The middle section is the Moscow stage.

Lower Moscow substage.

Sediments of the Moscow stage of the Middle Carboniferous are developed everywhere. Their total thickness is 120-125 m. Among the deposits of the Moscow stage, the following stand out: Vereisky, Kashira, Podolsky and Myachkovsky horizons.

The Vereisky horizon () is ubiquitous. It is represented by a pack of fatty and silty clays of cherry-red or brick-red color. There are interlayers of limestone, dolomite and flint up to 1 m thick. The Verei horizon is divided into three strata: Shat layers (red clays with ocher spots); Alyutovo strata (fine-grained red sandstone, brick-red clay, clay with silt interlayers); Horde layers (red clays with brachiopods, greenish dolomites, white dolomites with traces of worms). The total thickness of the Verei horizon ranges from 15-19 m in the south. Identified: Choristites aliutovensis Elvan.

The Kashira horizon () is composed of light gray (to white) and variegated dolomites, limestones, marls and clays with a total thickness of 50-65 m. According to lithological characteristics, the Kashira formation is divided into four strata, comparable with the Narskaya (16 m), Lopasninskaya (14 m ), Rostislavl (11 m) and Smedvinskaya strata (13 m) of the southern wing of the syneclise. The roof of the Kashira horizon contains Rostislavl variegated clays with thin layers of limestone and marls with a total thickness of 4-10 m. In the central part of the territory, the Rostislavl strata is absent. The Kashira deposits contain the fauna: Choristites sowerbyi Fisch., Marginifera kaschirica Ivan., Eostafella kaschirika Rails., Parastafella keltmensis Raus.

The Upper Moscow substage is developed everywhere and is subdivided into the Podolsk and Myachkovsky horizons.

Sediments of the Podolian horizon () within the pre-Jurassic erosion valley lie directly under Mesozoic and Quaternary deposits. In the rest of the territory they are covered by sediments of the Myachkovsky horizon, forming with it a single strata represented by gray fractured limestones with interlayers of clay. On the deposits of the Kashira horizon, the Podolsk strata lies with stratigraphic unconformity. The Podolsk horizon is represented by white, yellowish and greenish-gray fine- and fine-grained organogenic limestones with subordinate interlayers of dolomites, marls and greenish clays with flint nodules, with a total thickness of 40-60 m. Identified: Choristites trauscholdi stuck., Ch. jisulensis Stuck., Ch. mosquensis Fisch., Archaeocidaris mosquensis Ivan.

The Myachkovsky horizon () in the southern part of the territory under consideration lies directly under Mesozoic and Quaternary sediments, in the northern and northeastern parts it is covered by Upper Carboniferous sediments. In the area of ​​the village of V. Myachkovo and near the village. Kamenno-Tyazhino sediments of Myachkovsky age come to the surface. In the river valley The Pakhra and its tributaries, the Myachkovo deposits, are absent. The Myachkovsky horizon lies with stratigraphic unconformity on the sediments of the Podolsk horizon.

The horizon is represented mainly by pure organic limestones, sometimes dolomitized with rare interlayers of marls, clays and dolomites. The total thickness of deposits does not exceed 40 m. Myachkovo deposits contain an abundant fauna: brachiopods Choristites mosquensis Fish., Teguliferinamjatschkowensis Ivan.

Upper section.

Upper Carboniferous deposits are developed in the northern and northeastern parts of the region under consideration. They are exposed under Quaternary and Mesozoic formations, and in the area of ​​the city of Gzhel they emerge on the surface. The Upper Carboniferous is represented by deposits of the Kasimov and Gzhel stages.

Kasimovsky stage.

Sediments of the Kasimov stage are distributed in the northeastern part of the territory. They lie on Myachkovo deposits with erosion.

The Kasimovsky stage includes the Krevyakinsky, Khamovnichesky, Dorogomilovsky and Yauzsky horizons.

The Krevyakinsky horizon in the lower part is composed of limestones and dolomites, in the upper part - variegated clays and marls, which are a regional aquitard. The thickness of the horizon is up to 18 m.

The Khamovniche horizon is composed of carbonate rocks in the lower part and clayey-marly rocks in the upper part. The total thickness of sediments is 9-15 m.

The Dorogomilovsky horizon is represented in the lower part of the section by limestone strata, and in the upper part by clay and marls. Triticites acutus Dunb is widespread. Et Condra, Choristites cinctiformis Stuck. The thickness of the deposits is 13-15 m.

The Yauza layers are composed of dolomitized limestones and yellowish, often porous and cavernous dolomites with interlayers of red and bluish carbonate clays. Thickness 15.5-16.5 m. Triticites arcticus Schellw appears here, Chonetes jigulensis Stuck, Neospirifer tegulatus Trd., Buxtonia subpunctata Nic are widespread. The full thickness reaches 40-60 m.

The Gzhel Stage () is usually very thin.

The deposits of the Gzhel stage within the considered area are represented by Shchelkovo layers - light gray and brownish-yellow fine-grained or organogenic-clastic, sometimes dolomitized limestones and fine-grained dolomites, in the lower part there are red clays with limestone interlayers. The total thickness is 10-15m.

Among the Mesozoic deposits in the described area, formations of the Jurassic and lower part of the Cretaceous system were found.

Jurassic system.

Sediments of the Jurassic system are distributed everywhere, with the exception of places of high occurrence of Carboniferous deposits, as well as in ancient and partly modern Quaternary valleys, where they are eroded.

Among the Jurassic deposits, continental and marine sediments are distinguished. The first include undifferentiated sediments of the Bathonian and lower part of the Callovian stages of the middle section. The second group includes deposits of the Callovian stage of the middle section and Oxfordian stage of the upper section, as well as deposits of the Volgian regional stage.

Jurassic deposits lie with angular unconformity on deposits of the Carboniferous system.

Middle department.

Bathonian stage and lower part of the Callovian stage combined ()

Continental sediments of the Bathonian-Callovian age are represented by a thickness of sandy-clayey sediments, gray fine-grained, locally heterogeneous sands with gravel and black clays containing charred plant remains and carbonaceous layers. The thickness of these sediments ranges from 10 to 35 m, increasing in the lower parts of the pre-Jurassic erosion valley and decreasing on its slopes. They usually lie quite deep beneath Upper Jurassic marine sediments. The outcrop of continental Jurassic sediments to the surface is observed on the river. Pakhra. The age of the strata is determined by the remains of Middle Jurassic flora in similar clays. Identified: Phlebis whitbiensis Brongn., Coniopteris sp., Nilssonia sp., Equisetites sp.

Callovian Stage ()

In the territory under consideration, the Callovian stage is represented by the Middle and Upper Callovian.

The Middle Callovian lies transgressively on the eroded surface of the Upper and Middle Carboniferous or on continental Bathonian-Callovian sediments. In the territory under consideration, it has been preserved in the form of separate islands within the Main Moscow Hollow. Usually the deposits are represented by a sandy-clayey layer of brown-yellow and gray color with ferruginous oolites with nodules of oolitic marl. Fauna characteristic of the Middle Callovian: Erymnoceras banksii Sow., Pseudoperisphinctes mosquensis Fisch. ., Ostrea hemideltoidea Lah., Exogyra alata Geras., Pleurotomaria thouetensis Heb. Et Desl., Rhynchonella acuticosta Ziet, Rh. alemancia Roll, etc.

The thickness of the Middle Callovian ranges from 2 to 11; in the buried pre-Jurassic hollow it reaches 14.5 m. The maximum thickness is 28.5 m.

The Upper Callovian overlies the Middle Callovian with erosion and is represented by gray clays, often sandy, with phosphorite and marl nodules containing ferruginous oolites. The Upper Callovian is characterized by Quenstedticeras lamberti Sow. Due to their erosion during the Oxfordian time, the Upper Callovian sediments have insignificant thickness (1-3 m) or are absent altogether.

Upper section.

Oxford tier ()

Sediments of the Oxfordian stage lie with stratigraphic unconformity on the rocks of the Callovian stage and are represented in the study area by the lower and upper Oxford.

Lower Oxford is composed of gray, less often black, sometimes greenish clays with rare nodules of oolitic marl. The clays are fatty, plastic, sometimes schistose, slightly sandy and slightly micaceous. Phosphorites are dense, black inside. The fauna of the lower Oxford is often abundant: Cardioceras cordatom Sow., C. ilovaiskyi M. Sok., Astarta deprassoides Lah., Pleurotomaria munsteri Roem.

The thickness of the lower Oxford is very small (from 0.7 to several meters).

The Upper Oxford differs from the lower in the darker, almost black, color of the clays, greater sandiness, mica, and an increase in the admixture of glauconite. The boundary between upper and lower Oxford shows signs of erosion or shallowing. At the contact with lower Oxford, an abundance of pebbles from the underlying clays, the presence of rounded fragments of belemnite rostra, and bivalve shells were noted.

The upper Oxford is characterized by ammonites of the Amoeboceras alternans Buch group. Found here: Desmosphinctes gladiolus Eichw., Astarta cordata Trd. etc. The thickness of the Upper Oxford averages from 8 to 11 m, the maximum reaches 22 m. The total thickness of the Oxfordian stage ranges from 10 to 20 m.

Kimmeridgian Stage ()

The deposits of the Kimmeridgian stage lie with stratigraphic unconformity on the sequence of rocks of the Oxfordian stage. The deposits are represented by dark gray clays with layers of rare phosphorites and pebbles at the base of the sequence. Identified: Amoeboceras litchini Salt, Desmosphinctes pralairei Favre. etc. The thickness of the layer is about 10 m.

Volga regionarus.

Lower subtier ()

It lies with erosion on Oxford. Deposits of the lower Volgian stage emerge on the surface along the banks of the Moscow, Pakhra, and Mocha rivers.

Zone Dorsoplanites panderi. At the base of the lower Volgian stage lies a thin layer of clayey-glauconitic sand with rounded and thinned phosphorite nodules. The phosphorite layer is rich in fauna: Dorsoplanites panderi Orb., D. dorsoplanus Visch., Pavlovia pavlovi Mich. The thickness of the lower zone in outcrops does not exceed 0.5 m.

The Virgatites virgatus Zone is composed of three members. The lower member consists of thin gray-green glauconitic clayey sands, sometimes cemented into sandstone, with rare scattered clayey-glauconitic type phosphorites and phosphorite pebbles. Ammonites of the Virgatites yirgatus Buck group were found here for the first time. The thickness of the member is 0.3-0.4 m. The member is covered with a phosphorite layer. The upper member is composed of black glauconitic clayey sands and sandy clays. The thickness of the member is about 7 m. The total thickness of the zone is 12.5 m.

The Epivirgatites nikitini zone is represented by greenish-gray or dark green fine-grained glauconitic sands, sometimes clayey, cemented into loose sandstone; nodules of sandy phosphorite are scattered in the sands. The fauna includes Rhynchonella oxyoptycha Fisck, Epivirgatites bipliccisormis Nik., E. nikitini Mich. The thickness of the zone is 0.5-3.0 m. The total thickness of the Lower Volgian stage ranges from 7-15 m.

Upper subtier ()

The Upper Volga substage was penetrated by wells and reaches the surface near the Pakhra River.

It consists of three zones.

The Kachpurites fulgens zone is represented by dark green and brownish-green fine-grained, slightly clayey glauconitic sands with fine sandy phosphorites. Found here: Kachpurites fulgens Trd., K. subfulgens Nik., Craspedites fragilis Trd., Pachyteuthis russiensis Orb., Protocardia concirma Buch., remains of Inoceramus., sponges. The thickness of the zone is less than 1 meter.

The Garniericicaras catenulatum zone is represented by greenish-gray, slightly clayey, glauconitic sands with sandy phosphorites, rare at the bottom and numerous in the upper part of the sequence. The sandstones contain an abundant fauna: Craspedites subditus Trd. The thickness of the zone is up to 0.7 m.

The Craspedites nodiger zone is represented by sands of two fapial types. The lower part of the sequence (0.4 m) is composed of glauconitic sand or sandstone with phosphorite intergrowths. The thickness of this sequence does not exceed 3 m, but sometimes reaches 18 m. The characteristic fauna is: Craspedites nodiger Eichw., S. kaschpuricus Trd., S. milkovensis Strem., S. mosquensis Geras. The zone reaches a significant thickness from 3-4 m to 18 m, and in the Lytkarino quarries up to 34 m.

The total thickness of the Upper Volgian substage is 5-15 m.

Cretaceous system

Lower section.

Valanginian Stage ()

Sediments of the Valanginian stage lie with stratigraphic unconformity on rocks of the Volgian regional stage.

At the base of the Valanginian stage lies the Riasanites rjazanensis zone - the Ryazan horizon ", preserved in small islands in the basin of the 30th Moscow River. It is represented by a thin (up to 1 m) layer of sand with sandy phosphorite nodules, with Riasanites rjasanensis (Venez) Nik., R. subrjasanensis Nik., etc.

Barremian Stage ()

The Lower Valanginian sediments are transgressively overlain by a Barremian sandy-clayey sequence composed of interbedded yellow, brown, dark sands, sandy clays and highly micaceous clayey sandstones with siderite nodules with Simbirskites decheni Roem. The lower part of the Barremian stage, represented by light gray sands 3-5 m thick, is observed in many deposits on the Moscow, Mocha, and Pakhra rivers. At the top they gradually turn into Aptian sands. The total thickness of Barremian deposits reaches 20-25 m; however, due to Quaternary erosion, it does not exceed 5-10 m.

Aptian Stage ()

The deposits are represented by light (to white), fine-grained micaceous sands, sometimes cemented into sandstones, with interlayers of dark micaceous clays, and in places with plant remains. The total thickness of the Aptian deposits reaches 25 m; minimum thickness 3-5 m. Characteristic are Gleichenia delicata Bolch.

Albian Stage ()

Sediments of the Albian stage are preserved only on the Teplostan Upland. The Aptian deposits are overlain with stratigraphic unconformity. Under the coarse boulders, a 31 m thick layer of sandy-clayey sediments, overlying gray Aptian sands, was exposed.

Neogene system (N)

Sediments of the Neogene system lie with angular unconformity on Cretaceous sediments.

In the territory under consideration, a sandy layer of alluvial appearance was encountered. The most complete outcrops of sands of this type are located on the river. Pakhra. These deposits are represented by white and gray 31 fine-grained quartz sands, interbedded with coarse-grained and gravelly sands, with flint pebbles at the base, and in places with clay interlayers. The sands are diagonally layered and contain pebbles and boulders of local rocks - sandstone, flint and limestone. The total thickness of the Neogene does not exceed 8 m.

Quaternary system (O)

Quaternary sediments (Q) are widespread, overlying an uneven bed of bedrock. Therefore, the modern terrain largely repeats the buried terrain that formed at the beginning of the Quaternary period. Quaternary sediments are represented by glacial formations, which are represented by three moraines (Setun, Don and Moscow) and the fluvioglacial deposits separating them, as well as alluvial sediments of ancient Quaternary and modern river terraces.

Lower-middle Quaternary deposits of the Oka-Dnieper interglacial () are exposed by wells and reach the surface along the tributaries of the river. Pakhra. The water-bearing rocks are represented by sands with interlayers of loams and clays. Their thickness ranges from several meters to 20 m.

Moraine of the Dnieper glaciation (). It is widespread. It is represented by loams with pebbles and boulders. The thickness varies from 20 to 25 m.

Alluvial-fluvioglacial deposits lying between moraines of the Moscow and Dnieper glaciations (). Distributed over vast areas of the interfluve and along the river valleys. Moscow and r. Pakhra, as well as in the southwest, northwest and southeast of the territory. The deposits are represented by loams, sandy loams and sands, with a thickness of 1 to 20 m, sometimes up to 50 m.

Moraine of the Moscow glaciation and cover loams (). Distributed everywhere. The deposits are represented by red-brown boulder loam or sandy loam. The thickness is small, 1-2 m.

Fluvio-glacial deposits from the time of the retreat of the Moscow glacier () are distributed in the northwestern part of the territory and are represented by moraine loams. The thickness of the deposits reaches 2 m.

Valdai-Moscow alluvial-fluvioglacial deposits () are distributed in the southeast of this territory. The deposits are represented by fine-grained sands, about 5 m thick.

Middle-Upper Quaternary alluvial-fluvioglacial deposits () are distributed within three above-floodplain terraces in the valleys of the Moscow, Pakhra rivers and their tributaries. The deposits are represented by sands, in places with interlayers of loams and clays. The thickness of the deposits varies from 1.0 to 15.0 m.

Modern alluvial lake-marsh deposits () are distributed mainly in the northern part of the territory, on watersheds. The deposits are represented by sapropel (gyttia), gray gleyed lacustrine clays or sands. The thickness varies from 1 to 7 m.

Modern alluvial deposits () are developed within the floodplain terraces of rivers and streams, in the bottoms of ravines. The deposits are represented by fine-grained sands, sometimes silty, in the upper part with interlayers of sandy loam, loam and clay. The total thickness is 6-15 m, on small rivers and in the bottoms of ravines 5-8 m.

Features of tectonic structure. Territories different countries differ in the history of formation and geological structure. Belarus is located within the western part of the East European Plate, one of the nine largest ancient platforms on Earth. Belarus is characterized by a continental-type crust, the thickness of which ranges from 43 to 57 km. The platform has a two-tier structure: a sedimentary platform cover is located on the crystalline foundation. The presence of a solid crystalline foundation of great thickness determines the stability of the earth's crust. Belarus is characterized by slow vertical movements, the amplitude of which does not exceed 2 cm per year.

In the process of geological development, the crystalline foundation and platform cover were formed under the influence of tectonic movements. The different directions of the latter led to the formation of cracks - tectonic faults . They penetrate the crystalline basement and platform cover of all tectonic structures.

The territory of Belarus is characterized by a deep crystalline basement. Most of our country is located within Russian plate- the largest tectonic structure of the East European Platform. Southern regions belong to Volyn-Azov plate And Ukrainian shield(atlas, p. 9). The crystalline basement was formed more than 1650 million years ago. It is composed of igneous and metamorphic rocks crumpled into folds: granites, gneisses, quartzites. Tectonic faults break the foundation into blocks.

On top there is a platform cover, composed mainly of sedimentary rocks of a later age: clays, sands, limestones, chalk. They lie horizontally or are slightly folded by later movements of the earth's crust. The structure of the cover resembles a layer cake.

Geological chronology. The absolute age of the Earth is approximately 4.6 billion years. It is determined by the presence of radioactive elements and their decay products in rocks, as well as by the remains of plants and animals.

The stages of geological history differ in duration. They are associated with global changes in climate, the organic world, and the formation of certain rocks and minerals. The sequence of the main stages of the geological history of the Earth is reflected in geochronological table, or scale (Fig. 15). It is based on evolution organic life on the ground. Geological time is divided into 5 large segments called geological eras . Each era has its own stage in the development of the earth's crust, lasting several tens or hundreds of millions of years. The names of the eras reflect the nature of life on Earth in those times: Archean (translated from Greek means “the most ancient”), Proterozoic (era early life), Paleozoic ( ancient life), Mesozoic (middle life) and Cenozoic (new life).

During the Archean and Proterozoic eras (almost 90% of the entire geological history of the Earth), the foundation of ancient platforms was formed. At the end of the Proterozoic, a platform cover began to form. The accumulation of rocks in the sedimentary cover and the organic world differ over the course of eras, so the latter are divided into geological periods lasting tens of millions of years.

In the geological history of the Earth, several large mountain building cycles, the so-called folding : Baikal, Caledonian, Hercynian, Mesozoic, Alpine. During these periods, the collision of lithospheric plates led to the formation of mountain systems. The formation of tectonic structures in Belarus is associated with the eras of mountain building.

Tectonic structures. The crystalline basement represents an ancient Archean-Proterozoic mountain system. Under the influence of later tectonic movements, some parts of it rose and others sank, so the foundation in Belarus is located at different depths. Not far from the village of Glushkovichi, Lelchitsy district, it comes to the surface, and within the Pripyat trough it descends to a depth of 6 km. Large sections of the crystalline basement, which, as a rule, are separated by tectonic faults and have different thicknesses of the sedimentary cover, are called tectonic structures .

The largest tectonic structures in Belarus are the Russian Plate, the Volyn-Azov Plate and the Ukrainian Shield. Within the Russian plate, smaller tectonic structures are distinguished (Fig. 16). Depending on the depth of the foundation, they are divided into positive, negative And transitional .

Positive tectonic structures include anteclises and shields. Within their boundaries, the crystalline basement comes close to the surface. The largest of them is Belarusian anteclise. It occupies the northwestern and central parts of the country and extends latitudinally for 350 km. The platform cover within its boundaries usually does not exceed 500 m, and in its most elevated part - the Central Belarusian Massif - it has a thickness of only 80-100 m.

A small territory in the east of Belarus is occupied by the western slopes Voronezh anteclise. The surface of the crystalline basement in its most elevated part is located at a depth of 400 m. In the very south, the Ukrainian shield enters the territory of Belarus. Only within its boundaries do the rocks of the crystalline basement reach the surface.

Smaller positive structures are also visible. Among them Mikashevichi-Zhitkovichi ledge, within which the crystalline foundation comes close to the surface and building stone is mined.

Negative tectonic structures in Belarus are presented depressions And deflections. They are characterized by a deep foundation and different formation times. The oldest of them is Orsha depression. It was formed during the Baikal mountain building era in the northeast of the republic. The crystalline basement within the Orsha depression lies at a depth of 800 to 1800 m.

Brest depression has a latitudinal strike and occupies the southwestern part of Belarus. Its western part is located in Poland. The depression was formed at the beginning of the Paleozoic during the Caledonian folding. The foundation surface within its boundaries is at a depth of 700-1700 m.

Located in the southeast of Belarus Pripyat trough. This is the youngest tectonic structure formed in the Devonian, during the Hercynian folding. The Pripyat trough is divided into stages by numerous latitudinal faults. In some places, the crystalline basement descends to a depth of 6 km. The large thickness of sediments in the cover led to the formation of minerals of sedimentary origin: potassium and rock salts, brown coal, oil, gypsum, etc.

Transitional tectonic structures also stand out on the tectonic map of Belarus - saddles. The largest among them are Latvian, Zhlobin, Polesskaya And Braginsko-Loevskaya. They usually separate two positive and two negative tectonic structures. Due to this, the crystalline foundation within them is most often located at depths from 500 to 1000 m, and they themselves resemble a saddle in structure. (Determine what positive and negative tectonic structures are shared by the Zhlobin, Latvian, Polesie and BraginLoevskaya saddle.)

Bibliography

1. Geography 10th grade/ Tutorial for 10th grade institutions of general secondary education with Russian as the language of instruction/Authors: M. N. Brilevsky- “From the authors”, “Introduction”, § 1-32; G. S. Smolyakov- § 33-63 / Minsk "People's Asveta" 2012