This section describes the geological structure (stratigraphy, tectonics, history geological development, industrial oil and gas potential) of the Luginetskoye field.
Stratigraphy
The geological section of the Luginetskoye field is represented by a thick layer of terrigenous rocks of various lithological and facial compositions of Mesozoic-Cenozoic age, lying on the eroded surface of Paleozoic deposits of the intermediate complex. The stratigraphic division of the section was carried out according to data from deep wells on the basis of correlation schemes approved by the Interdepartmental Stratigraphic Committee in 1968 and refined and supplemented in subsequent years (Tyumen in 1991). The general scheme of stratified formations may look like this:
Paleozoic erathema - RJ
Mesozoic erathema - MF
Jurassic System - J
Lower-middle section - J 1-2
Tyumen Formation - J 1-2 tm
Upper section - J 3
Vasyugan Formation - J 3 vs
Georgievskaya Formation - J 3 gr
Bazhenov Formation - J 3 bg
Cretaceous system - K
Lower section - K 1
Kulomzinskaya Formation - K 1 kl
Tara Formation - K 1 tr
Kiyalinskaya suite - K 1 kl
Lower-upper section - K 1-2
Pokurskaya suite - K 1-2 pk
Upper section - K 2
Kuznetsovskaya formation - K 2 kz
Ipatovskaya suite - K 2 ip
Slavgorod Formation - K 2 sl
Gankinsky Formation - K 2 gn
Cenozoic erathema - KZ
Paleogene system - P
Paleocene - P 1
Lower section - P 1
Talitskaya suite - R 1 tl
Eocene - P 2
Middle section - P 2
Lyulinvor Formation - P 2 ll
Middle-upper section - P 2-3
Chegan Formation - P 2-3 cg
Oligocene - P 3
Quaternary system - Q
Paleozoic erathema - RJ
According to drilling data, the basement rocks in the study area are represented mainly by formations of an intermediate complex - limestones with interlayers of terrigenous and effusive rocks of varying thickness. The deposits of the intermediate complex were penetrated by ten wells: six exploration and four production. The most complete section of the intermediate complex (thickness 1525 m) was discovered in well. 170.
Mesozoic erathema - MF
Jurassic System - J
Jurassic deposits in the described area are represented by mixed-facies sediments of the Middle and Upper Jurassic. They are divided into three formations - Tyumen, Vasyugan and Bazhenov.
Lower-middle section - J 1-2
Tyumen Formation - J 1-2 tm
The retinue is named after the city of Tyumen, Western Siberia. Selected by Rostovtsev N.N. in 1954. Its thickness is up to 1000-1500 m. It contains: Clathropteris obovata Oishi, Coniopteris hymenophyloides (Bron gn.) Sew., Phoenicopsis angustifolia Heer.
The deposits of the Tyumen Formation lie on the eroded surface of the Jurassic intermediate complex. The productive horizon Yu 2 lies at the top of this formation.
The formation is composed of continental sediments - mudstones, siltstones, sandstones, carbonaceous mudstones and coals with a predominance of clayey-siltstone rocks in the section. Sandy layers, due to their continental origin, are characterized by sharp facies-lithological variability.
Upper section - J 3
Upper Jurassic deposits are represented mainly by rocks of transitional genesis from marine to continental. Represented by the Vasyugan, Georgievsk and Bazhenov formations.
Vasyugan Formation - J 3 vs
The formation is named after the Vasyugan River, West Siberian Lowland. Selected Sherihoda V.Ya. in 1961. Its thickness is 40-110 m. The formation contains: Quenstedtoceras and foraminiferal complexes with Recurvoides scherkalyemis Lev. and Trochammina oxfordiana Schar. Part of the midday series.
The deposits of the Vasyugan Formation lie conformably on the deposits of the Tyumen Formation. The deposits are composed of sandstones and siltstones interbedded with mudstones, carbonaceous mudstones and rare coal interbeds. According to the generally accepted division of the Vasyugan formation section, the main productive horizon Yu 1, distinguished in the formation section, is universally divided into three strata: sub-coal, inter-coal and supra-coal. The lower subcoal strata includes fairly consistent sand layers Yu 1 4 and Yu 1 3 of coastal-marine origin, the deposits of which contain the bulk of the oil and gas reserves of the Luginetskoye field. The intercoal strata is represented by mudstones and interlayers of coals and carbonaceous mudstones with rare lenses of sandstones and siltstones of continental origin. The upper - supra-coal strata is composed of layers of sandstones and siltstones Yu 1 2 and Yu 1 1 that are not consistent in area and section. Sandy-siltstone formation Yu 1 0, included in the productive horizon Yu 1, because It forms a single massive reservoir with the productive strata of the Vasyugan formation, and stratigraphically belongs to the Georgievsk formation, the deposits of which are absent in significant areas of the Luginetskoye field.
Georgievskaya Formation - J 3 gr
Name of the suite for the village of Georgievskoye, Olkhovaya River basin, Donbass. Selected: Blank M. Ya., Gorbenko V. F. in 1965. Stratotype on the left bank of the Olkhovaya River near the village of Georgievskoye. Its thickness is 40 m. It contains: Belemnitella Langei Langei Schatsk., Bostrychoceras polyplocum Roem., Pachydiscus wittekindi Schlut.
The rocks of the Vasyugan formation are overlain by deep-sea clays of the Georgievsk formation. Within the described zone the thickness of the formation is insignificant.
Bazhenov Formation - J 3 bg
The retinue is named after the village of Bazhenovo, Sargatsky district, Omsk region, Western Siberia. Highlighted by Gurari F.G. in 1959 Its thickness is 15-80 m. Stratotype - from one of the wells of the Sargat area. It contains: numerous remains of fish, crushed shells of Dorsoplanitinaeu, less commonly bukhia.
The Bazhenov Formation is widespread and is composed of deep-sea bituminous mudstones, which are a reliable cover for the oil and gas deposits of the Vasyugan Formation. Its thickness is up to 40m.
Marine sediments of the Bazhenov Formation are characterized by consistent lithological composition and areal distribution, and a clear stratigraphic reference. These factors, as well as a clear appearance on well logs, make the formation a regional benchmark.
Cretaceous system - K
Lower section - K 1
Kulomzinskaya Formation - K 1 kl
The formation is distributed in the southern and central regions of the West Siberian Plain. Highlighted by: Aleskerova Z.T., Osechko T.I. in 1957. Its thickness is 100-250 m. It contains Buchia cf. volgensis Lah., Surites sp., Tollia sp., Neotollia sibirica Klim., Temnoptychites sp. The retinue is part of the Poludinsky series.
The formation is composed of marine, predominantly clayey sediments, conformably overlying the Upper Jurassic. These are mainly gray, dark gray, dense, strong, silty mudstones, with thin interlayers of siltstone. In the upper part of the formation, a group of sandy layers B 12-13 is distinguished, and in the lower part, the Achimov member is distinguished, composed mainly of compacted sandstones and siltstones with interlayers of mudstones.
Tara Formation - K 1 tr
The formation is distributed in the southern and central region of the West Siberian Lowland. Identified from a reference well in the area of the city of Tara, Omsk region, Western Siberia by N.N. Rostovtsev. in 1955. Its thickness is 70-180 m. Contains: Temnoptycnites spp. The Tara Formation is part of the Poludinsky Series.
The formation sediments conformably overlie the rocks of the Kulomzin formation and represent sandy deposits of the final stage of the Upper Jurassic-Valanginian transgression of the sea. The main composition of the formation is a series of sandy layers of group B 7 - B 10 with subordinate interlayers of siltstone and mudstone.
Kiyalinskaya suite - K 1 kl
The formation is distributed in the south of the West Siberian Plain. It was identified from a well near the Kiyaly station, Kokchetav region, Central Kazakhstan, by A.K. Bogdanovich. in 1944 Its thickness is up to 600 m. Contains: Carinocyrena uvatica Mart. etvelikr., Corbicula dorsata Dunk., Gleichenites sp., Sphenopteris sp., Podozamites lanceolatus (L. et H.) Shimp., P. reinii Geyl., Pitiophyllum nordenskiodii (Heer) Nath.
The Kiyalinskaya formation is composed of continental sediments, correspondingly overlying the deposits of the Tara formation, and is represented by unevenly interbedded clays, siltstones and sandstones with a predominance of the former in the section. The sandy layers in the formation belong to the group of layers B 0 - B 6 and A.
Lower-upper section - K 1-2
Pokurskaya suite - K 1-2 pk
Lower-Upper Cretaceous deposits in the Aptalbsenomanian volume are combined into the Pokur Formation, which is the thickest. The formation is distributed in the West Siberian Lowland. The formation was named after a reference well near the village of Pokurka on the Ob River, Khanty-Mansiysk Autonomous Okrug. The formation was identified by N.N. Rostovtsev. in 1956. It lies conformably on the Sargat Group and is overlapped with a break by the Derbyshin
The formation is composed of continental sediments, represented by interlayering of clays, siltstones and sandstones. The clays are gray, brownish-gray, greenish-gray, silty in areas, lumpy, cross-bedded.
The sandy layers of the Pokur formation are unconsistent along the strike, their thickness varies from several meters to 20 m. The lower part of the formation is more sandy.
Upper section - K 2
The Upper Cretaceous sediments are represented by a thickness of marine, predominantly clayey rocks, which, according to the deposits of the Lower Cretaceous, are divided into four formations: Kuznetsovskaya (Turonian), Ipatovskaya (Upper Turonian + Coniacian + Lower Santonian), Slavgorodskaya (Upper Santonian + Campanian) and Gankinskaya (Maastrichtian + Denmark).
Kuznetsovskaya formation - K 2 kz
The formation was identified from the Kuznetsovo well, Tavda River, Sverdlovsk region by N.N. Rostovtsev. in 1955. Its thickness is up to 65 m. Contains: Baculites romanovskii Arkh., Inoceramus ef. labiatus Schloth. and foraminifera with Gaudryina filiformis Berth
The formation is composed of gray, dark gray, dense, foliated, sometimes calcareous or silty and micaceous clays.
Ipatovskaya suite - K 2 ip
The formation was identified from a well in the village of Ipatovo, Novosibirsk region Rostovtsev N.N. in 1955. Its thickness is up to 100 m. Contains: a complex of foraminifera with large Lagenidae; Clavulina haststs Cushm. and Cibicides westsibirieus Balakhm.
The formation is widespread in the southern and central parts of the West Siberian Lowland. It is part of the Derbyshin series and is divided into a number of units.
The sediments of the formation are represented by interlayering of siltstones, opoka-like clays and opoka. Siltstones are gray, dark gray, weakly cemented, sometimes glauconite, layered in areas; opoka-like clays are gray, light gray and bluish-gray, silty; the flasks are light gray, horizontally and wavy-layered, with a conchoidal fracture.
Slavgorod Formation - K 2 sl
The formation was identified from a reference well - the city of Slavgorod, Altai Territory by N.N. Rostovtsev. in 1954. The thickness of the formation is up to 177 m, contains foraminifera and radiolarians, is part of the Derbyshin series, distributed in the southern and central parts of the West Siberian Lowland.
The Slavgorod Formation is composed predominantly of gray, greenish-gray clays, homogeneous, greasy to the touch, plastic, sometimes with rare thin layers of sandstones and siltstones, with inclusions of glauconite and pyrite.
Gankinsky Formation - K 2 gn
The formation is distributed in the West Siberian Lowland and the eastern slope of the Urals. Identified from a well in the village of Gankino, Northern Kazakhstan by Bogdanovich A.K. in 1944. The thickness of the formation is up to 250 m. It contains: Baculites anceps leopoliensis Nowak., B. nitidus Clasun., Belemnitella lancealata Schloth., foraminiferal complexes with Gaudryina rugosa spinulosa Orb., Spiroplectammina variabilis Neckaja, Sp. kasanzevi Dain, Brotzenella praenacuta Vass.
The Gankin Formation is part of the Derbyshin Group and is subdivided into a number of members.
The formation is composed of gray, greenish-gray, siliceous, non-layered marls and gray clays, calcareous or silty areas, with thin layers of silt and sand.
Paleogene system - P
The Paleogene system includes marine, mainly clayey sediments of the Talitsky (Paleocene), Lyulinvor (Eocene), Chegan (Upper Eocene - Lower Oligocene) formations and continental sediments of the Nekrasovsky series (Middle - Upper Oligocene), which conformably overlie Cretaceous deposits.
Lower section - P 1
Talitskaya suite - R 1 tl
The formation is distributed in the West Siberian Lowland and the eastern slope of the Urals, named after the village of Talitsa, Sverdlovsk region, identified by Alekserova Z.T., Osyko T.I. in 1956. The thickness of the formation is up to 180 m. It contains: foraminiferal complexes of the Ammoscalaria inculta zones, spores and pollen from Trudopollis menneri (Mart.) Zakl., Quercus sparsa Mart., Normapolles, Postnor mapolles, radiolarians and ostracods, Nuculana biarata Koen., Tellina edwardsi Koen ., Athleta elevate Sow., Fusus speciosus Desh., Cylichna discifera Koen., Paleohupotodus rutoti Winkl., Squatina prima Winkl.
The Talitsky Formation is composed of dark gray to black clays, dense, viscous in areas, greasy to the touch, sometimes silty, with interlayers and powders of silts and fine-grained sands, quartz-feldspar-glauconitic, with pyrite inclusions.
Middle section - P 2
Lyulinvor Formation - P 2 ll
Formation, distributed on the Western Siberian Plain. The name is given from the Lyumin-Vor hill, Sosva river basin, Ural Li P.F. in 1956. The thickness of the formation is up to 255 m. It is divided into three subformations (the boundary between the subformations is drawn conditionally). Suite contains: complex diatoms, spore-pollen complex with Triporopollenites robustus Pfl. and with Triporopollenites excelsus (R. Pot) Pfl., a radiolarian complex with Ellipsoxiphus ckapakovi Lipm. and with Heliodiscus Lentis Lipm.
The formation is composed of clays that are greenish-gray, yellow-green, greasy to the touch, in the lower part opoka-like, in places turning into opoka. The clays contain interlayers of gray micaceous silts and heterogeneous quartz-glauconite sands and weakly cemented sandstones.
Middle-upper section - P 2-3
Chegan Formation - P 2-3 cg
The formation is distributed in Ustyurt, the northern Aral Sea region, the Turgai Plain and the south of the West Siberian Plain. Named after the Chegan River, Aral Sea region, Kazakhstan Vyalov O.S. in 1930. Its thickness is up to 400 m. Contains: assemblages of smallmouths with Turritella, with Pinna Lebedevi Alex., Glossus abichiana Rom., foraminiferal assemblages with Brotzenella munda N. Buk. and with Cibicides macrurus N. Buk., ostracod complexes with Trachyleberis Spongiosa Liep., spore and pollen complex with Qulreus gracilis Boitz. The formation is divided into two subformations.
The Chegan Formation is represented by bluish-green, greenish-gray, dense clays, with nests, powders and lens-shaped layers of gray quartz and quartz-feldspathic sands, inequigranular and siltstones.
Quaternary system - Q
Sediments of the Quaternary system are represented by gray, dark gray, fine-medium-grained sands, less often - coarser-grained, sometimes clayey, loams, brownish-gray clays, with lignite interlayers and a soil-vegetative layer.
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 carried out according to the existing hydro geological map on 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. Full power 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 units. 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 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.
Relief is a set of irregularities on the earth's surface. These irregularities are called landforms. The relief was formed as a result of the interaction of internal (endogenous) and external (exogenous) geological processes.
Landforms are distinguished by size, structure, origin, etc. There are convex (positive) and concave (negative) landforms.
The territory of Russia is distinguished by a very diverse topography. There are high lores and low plains here. The highest point in Russia is Mount Elbrus (5642 m), and the lowest is on the Caspian Lowland (28 m below sea level).
Most of the territory of Russia is an amphitheater, inclined to the north. A belt of high mountains stretches along the southern borders of the country: the Caucasus, Altai, Sayan Mountains, and the mountains of Transbaikalia. Therefore, most of the large rivers (Ob, Irtysh, Yenisei, Lena, Yana, Indigirka, Kolyma) flow from south to north. The general tilt of the relief to the north is associated with the subduction of the African-Arabian and Hindustan lithosphere plates under the Eurasian plate. At the point of their contact, the sedimentary layers of the earth's crust are uplifted and folded into folds, and high mountains are formed. In the plate contact zone, intense movements of sections of the earth's crust occur. They are accompanied by earthquakes.
In the east of our country, in the Baikal region and Transbaikalia, interaction between parts of the Eurasian lithospheric plate- Chinese and Siberian platforms. In the zone of their contact, vast areas of the earth’s crust crack, and a deep depression in Lake Baikal is formed.
The Yenisei Valley divides Russia into two parts - eastern elevated and western - with a predominance of low plains. Most of the country's territory is occupied by plains. This is due to the fact that within Russia there are several large platforms of different ages: the ancient Precambrian Russian and Siberian platforms, as well as younger (Paleozoic): West Siberian, Scythian, Turanian. The foundation of young platforms (slabs) is submerged to varying depths under the sedimentary cover. In the area of ancient platforms, the foundation in some places reaches the surface, forming the so-called shields (Baltic on the Russian platform, Anabar and Aldan on the Siberian platform).
The largest East European Plain is located on the Russian Platform. Its surface is characterized by alternating hills (Central Russian, Volga, Smolensk-Moscow) and lowlands (Oka-Don).
In the area between the Yenisei and Lena rivers there is the vast Central Siberian Plateau (with an average height of 500-800 m). It is complicated nearby large plateaus and ancient ridges (Putoraka plateau, Yenisei ridge, etc.). To the north, the plateau passes into the North Siberian Lowland, and to the east into the Central Yakut Plain.
Between the East European Plain and the Central Siberian Plateau lies the largest accumulative West Siberian Plain. It has a low-lying, swampy surface and a concave shape.
In the south, a section of the young Alpine geosynclinal belt adjoins the Russian Plain. In relief it is expressed by the Caucasian mountainous country, within which it is located highest point Russia - Elbrus (5642 m).
The entire territory of Siberia is also enclosed from the south by a mountain belt stretching along the Russian border. These are mainly medium-height mountain systems - Altai, Salair Ridge, Kuznetsk Alatau, Western and Eastern Sayans, the mountains of Tuva, the Baikal region, Transbaikalia and the Stanovoy Highlands. They were formed at different geological times (from the end of the Proterozoic to the end of the Paleozoic).
In the north-east of Russia, the relief of strongly dissected middle mountains prevails, confined to the massifs of Mesozoic folding (Chersky, Verkhoyansky, Kolyma and Kolyma and Koryak highlands).
Kamchatka, o. Sakhalin and the Kuril Islands ridge belong to the area of young Pacific folding. There are about 200 dormant and active volcanoes here, and many earthquakes are recorded annually. This indicates that intensive processes in the earth’s crust are ongoing today at the junction of the Pacific and Eurasian lithospheric plates.
The vast territory, the abundance of relief forms and the complexity of the geological structure of Russia have determined the presence of a wide range of mineral resources.
The largest and largest landforms owe their origin to the internal forces of the Earth. But many important details of their modern appearance were created by external forces.
Almost everywhere on the territory of Russia, the formation of modern relief occurred and continues to occur under the influence of flowing waters. As a result, erosional relief forms appeared - river valleys, gullies and ravines. The gully-gully network is especially dense in the Central Russian and Volga uplands and in the foothills.
The topography of many coastal plains is associated with the retreat and advance of the sea.
These are the plains of the Caspian, Azov, Pechora and northern parts of the West Siberian lowlands.
Cover Quaternary glaciations created specific forms of relief in the northern half of the European part, and also (to a lesser extent) in Siberia.
Mountain glaciers also significantly influenced the relief of mountains in Quaternary times. There are still glaciers on the highest mountains.
In some regions of Russia there are landforms created by wind activity (Caspian lowland, Kaliningrad region). 64% of Russia's territory is within the zone permafrost. This zone is also associated with special forms of relief - heaving mounds, pound drawdowns, etc.
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 Konsk-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). Special type 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. Along northern region The Mesozoic Khatanga and Leno-Anabar depressions stretch across the platforms. 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 outskirts, on the slopes of the Anabar anteclise and in southern regions platforms, forming linear zones along faults cutting the basement and cover deposits. 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-Alay and part of the Tien Shan (Turkestan, Zeravshan, Alay, Gissar, Kokshaltau ridges), the Balkhash part 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. 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. Along northern border, from the Caspian to the Aral Sea, the Mangyshlak system of uplifts stretches. 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. Separation of external and internal zones began with 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; power reaches it maximum values 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-clayey 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-Chukchi fold region widespread 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.
Geologically, the territory of Russia consists of a complex mosaic of blocks formed by a variety of rocks that arose over a period of 3.5–4 billion years.
There are large lithospheric plates 100–200 km thick, which experience slow horizontal movements at a speed of about 1 cm/year due to convection (flow of matter) in the deep layers of the Earth's mantle. When moving apart, deep cracks are formed - rifts, and later, during spreading, oceanic depressions appear. Heavy oceanic lithosphere, when plate movement changes, sinks under continental plates in subduction zones, along which oceanic trenches and island volcanic arcs or volcanic belts form at the edges of continents. When continental plates collide, a collision occurs with the formation of fold belts. When oceanic and continental plates collide big role assigned to accretion - the attachment of alien blocks of crust, which can be brought thousands of kilometers away during the immersion and absorption of oceanic in the process of subduction.
Currently most of territory of Russia is located within the Eurasian lithospheric plate. Only the folded region of the Caucasus is part of the Alpine-Himalayan collision belt. In the extreme east is the Pacific oceanic plate. It plunges under the Eurasian plate along the subduction zone, expressed by the Kuril-Kamchatka deep-sea trench and the volcanic arcs of the Kuril Islands and Kamchatka. Within the Eurasian plate, splits are observed along the Baikal and Momma rifts, expressed by the lake depression. Baikal and zones major faults V . Plate boundaries are distinguished by increased .
In the geological past, as a result of movement, the East European and Siberian platforms were formed. The East European Platform includes the Baltic Shield, where Precambrian metamorphic and igneous rocks are developed on the surface, and the Russian Plate, where the crystalline basement is covered by a cover of sedimentary rocks. Accordingly, within the Siberian platforms, the Aldan and Anabar shields, formed in the Early Precambrian, are distinguished, as well as vast spaces covered by sedimentary and volcanogenic rocks, which are considered to be the Central Siberian plate.
Between the East European and Siberian platforms stretches the Ural-Mongolian collision belt, within which folded systems of complex structure arose. A significant part of the belt is covered by the sedimentary cover of the West Siberian Plate, the formation of which began at the beginning of the Mesozoic. From the east, the Siberian Platform is adjacent to heterogeneous folded structures that arose largely as a result of accretion.
Archaea. Archean formations come to the surface on the Aldan and Anabar shields and participate in the structure of the foundation of the platforms. They are represented mainly by gneisses and crystalline schists. Archean rocks are highly metamorphosed, up to the granulite facies, and the processes of magmatization and granitization are intensely manifested. For Archean rocks, radiological dates are available in the range of 3.6–2.5 billion years. Archean rocks are intensively dislocated everywhere.
Proterozoic
The Lower and Upper Proterozoic are distinguished, sharply differing in the degree of metamorphism and dislocation.
The Lower Proterozoic participates in the structure of shields along with the Archean. Its composition includes: gneisses, crystalline schists, amphibolites, and in places metavolcanic rocks and marbles.
The Upper Proterozoic is divided into Riphean and Vendian in many regions. Compared to the Lower Proterozoic, these rocks are characterized by significantly less metamorphism and dislocation. They form the base of the cover of platform areas. On the Russian Plate in the Riphean, mafic volcanics are widely developed in places, while sandstones, gravelites, siltstones and clays predominate in the Vendian. On the Siberian Platform, the Upper Proterozoic is represented by practically unmetamorphosed sandy-clayey and carbonate rocks. In the Urals, the Upper Proterozoic section has been studied in the most detail. The Lower Riphean is composed of shales, quartzite-like sandstones, and carbonate rocks. In the Middle Riphean, along with terrigenous and carbonate rocks, basic and acidic volcanic rocks are common. The Upper Riphean is composed of various terrigenous rocks, limestones and dolomites. At the very top of the Riphean there are mafic volcanic rocks and tillite-like conglomerates. The Vendian is composed of sandstones, siltstones and mudstones of flyschoid structure. In the folded areas framing the Siberian Platform, the Upper Proterozoic has a similar structure.
Paleozoic
The Paleozoic consists of the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian systems.
On the Russian Plate in the Cambrian system, characteristic “blue clays” are developed, giving way to siltstones and fine-grained sandstones. On the Siberian Platform in the Lower and Middle Cambrian, dolomites with layers of anhydrites and rock salt are common. In the east, they are facies replaced by bituminous carbonate rocks with intercalations of oil shale, as well as reef bodies of algal limestones. The Upper Cambrian is formed by red sandy-clayey rocks and, in places, carbonates. In folded areas, the Cambrian is characterized by a variety of composition, great thickness and high dislocation. In the Urals, in the Lower Cambrian, basic and acidic volcanics, as well as sandstones and siltstones with reef limestones, are common. The Middle Cambrian falls out of the section. The Upper Cambrian is formed by conglomerates, glauconitic sandstones, siltstones and mudstones with siliceous shales and limestones in the form of separate layers.
The Ordovician system on the Russian plate is composed of limestones, dolomites, as well as carbonate clays with phosphorite nodules and oil shale. On the Siberian Platform in the Lower Ordovician, a variety of carbonate rocks developed. The Middle Ordovician is composed of calcareous sandstones with interlayers of shell limestones, sometimes with phosphorites. In the Upper Ordovician, sandstones and mudstones with siltstone interlayers are developed. In the Urals, the Lower Ordovician is represented by phyllitic shales, quartzite-like sandstones, gravelites and conglomerates with interlayers of limestone and, in places, basic volcanics. The Middle and Upper Ordovician is composed of predominantly terrigenous rocks in the lower part, and limestone and dolomites with interlayers of marls, mudstones and siltstones in the upper part; basalts, siliceous tuffites and tuffs predominate to the east.
The Silurian system on the Russian plate is composed of limestones, dolomites, marls and mudstones. On the Siberian Platform in the Lower Silurian, organogenic clayey limestones with interlayers of marls, dolomites and mudstones are common. The Upper Silurian contains red rocks, including dolomites, marls, clays and gypsum. In the Western Urals, dolomites and limestones, and in some places clay shales, are developed in the Silurian. To the east they are replaced by volcanic rocks, including basalts, albitophyres, and siliceous tuffites. Within the accretionary belt in northeastern Russia, Silurian deposits are diverse in composition. Carbonate rocks are developed in the Upper Silurian: red rocks and conglomerates appear in the center and east of the Urals. In the extreme east of the country (Koryak Autonomous Okrug), basalts and jaspers with limestones in the upper part of the section predominate.
The Devonian system on the Russian plate differs significantly in structure in its various parts. In the west, limestones, dolomites, marls and small pebbles are developed at the base of the Devonian. In the Middle Devonian, rock salt appeared together with red-colored terrigenous rocks. The upper part of the section is characterized by the development of clays and marls with layers of dolomite, anhydrite and rock salt. In the central part of the plate, the volume of terrigenous rocks increases. In the east of the plate, along with red rocks, bituminous limestones and shales are widespread, standing out as the Domanik formation. On the Siberian Platform, the Devonian in its northwestern part is composed of evaporites, carbonate and clay deposits, and in the eastern part - volcanic-sedimentary rocks with layers of rock salt and evaporites. In some areas in the south of the platform, coarse red-colored strata with basalt covers are developed. In the west of the Urals, the Lower Devonian is dominated by limestones, along with sandstones, siltstones and mudstones. In the Middle Devonian, limestones with admixtures of sandstones, siltstones, clayey and siliceous shales are also common. The Upper Devonian begins with a sandy-clayey sequence. Above are limestones with layers of marls, dolomites and bituminous shale. In the eastern regions of the Urals in the lower and middle Devonian, volcanic rocks of basic and acidic composition are developed, accompanied by jaspers, shales, sandstones and limestones. In places, bauxite is noted in the Devonian deposits of the Urals. In the Verkhoyansk-Chukchi fold system, the Devonian is represented mainly by limestones, shales and siltstones. The section of the Kolyma-Omolon massif has significant differences, where volcanic rocks, including rhyolites and dacites, accompanied by tuffs, became widespread in the Devonian. In the more southern regions of the accretion belt in northeastern Russia, predominantly terrigenous rocks are distributed, in some places reaching great thickness.
The Carboniferous system on the Russian Plate is formed mainly by limestones. Only at the southwestern limit of the Moscow syneclise do clays, siltstones and sands with coal deposits come to the surface. On the Siberian Platform in the lower part of the Carboniferous, limestones are predominantly common, and sandstones and siltstones are higher up. In the west of the Urals, the Carboniferous is formed mainly by limestones, sometimes with layers of dolomite and siliceous rocks, while only in the Upper Carboniferous terrigenous rocks with massive bodies of reef limestones predominate. In the east of the Urals, flyschoid strata are widespread, and in some places volcanic rocks of intermediate and basic composition are developed. In some areas, terrigenous coal-bearing strata are developed. Predominantly terrigenous rocks participate in the structure of the fold belt in northeastern Russia. In the southern regions of this belt, clayey and siliceous shales are common, often accompanied by volcanics of intermediate and basic composition.
The Permian system on the Russian plate in the lower part is represented by limestones, giving way up the section to evaporites, in places with rock salt. In the Upper Permian, sandy-clayey red deposits arose in the east of the plate. In more western areas, sediments of varied composition are common, including sandstones, siltstones, clays, marls, limestones and dolomites. In the upper part of the section, variegated marls and red clays are present among terrigenous rocks. On the Siberian Platform, the Permian is composed predominantly of terrigenous rocks, in places with layers of coal, as well as with interlayers of clayey limestone. In the folded systems of the Far East in the Permian, along with terrigenous rocks, siliceous shales and limestones, as well as volcanic rocks of various compositions, are developed.
Mesozoic
The Mesozoic consists of deposits of the Triassic, Jurassic and Cretaceous systems.
The Triassic system on the Russian Plate is composed of sandstones, coglomerates, clays and marls in the lower part. The upper part of the section is dominated by variegated clays with layers of brown coal and kaolin sands. On the Siberian Platform, Triassic rocks formed the Tunguska syneclise. Here, in the Triassic, lavas and basalt tuffs of great thickness were formed, attributed to the trap formation. Sandstones, siltstones and mudstones of great thickness are developed in the Verkhoyansk fold system. Within the accretionary belt in the Far East, limestones, siliceous rocks, and volcanic rocks of intermediate composition are found.
The Jurassic system on the Russian Plate is represented in the lower part by sandy-clayey rocks. In the middle part of the section, along with clays, sandstones and marls, limestones and brown coals appear. The Upper Jurassic is dominated by clays, sandstones and marls, in many areas with phosphorite nodules, sometimes with oil shale. On the Siberian Platform, Jurassic sediments fill individual depressions. In the Leno-Anabar depression, thick strata of conglomerates, sandstones, siltstones and mudstones are developed. In the extreme south of the platform, terrigenous deposits with coal seams occur in depressions. In the folded systems of the Far East in the Jurassic, terrigenous rocks predominate, accompanied by siliceous shales and volcanics of intermediate and felsic composition.
The Cretaceous system on the Russian Plate is composed of terrigenous rocks with phosphorite nodules and glauconite. The upper part of the section is distinguished by the appearance of limestones, as well as marls and chalk, flasks and tripoli, in places with abundant flint concretions. Various terrigenous rocks are widespread on the Siberian Platform, in some areas containing layers of coal and lignite. In the folded systems of the Far East, predominantly terrigenous rocks of great thickness are common, sometimes with siliceous shales and volcanics, as well as with coal seams. In the Cretaceous in the Far East, extended volcanic belts formed on the active margins of the continent. Volcanogenic rocks of various compositions are developed within the Okhotsk-Chukotka and Sikhote-Alin belts. The chalk is composed of terrigenous rocks of great thickness, along with siliceous rocks and volcanics.
Cenozoic
The Paleogene system on the Russian Plate is composed of opokas, sandstones and siltstones, and in some areas marls and phosphorite-bearing sands. On the West Siberian Plate, the Paleogene is formed by opoka, diatomites, mudstones, and sands. In some places there are interlayers of iron and manganese ores. In some areas there are lenses of brown coals and lignites. In the Far East, individual depressions are filled with terrigenous strata of great thickness. In volcanogenic belts they are accompanied by basalts. Andesites and rhyolites are developed in Kamchatka.
The Neogene system on the Russian Plate is composed of sands and clays of the Miocene, and higher up - limestones of the Pliocene. On the West Siberian Plate, the Neogene is represented predominantly by clays. In the Far East, pebbles, sands and clays were common in the Neogene. A significant role belongs to volcanic rocks, especially common in Kamchatka and the Kuril Islands.
The Quaternary system (Quarter) appears almost everywhere, but the thickness of sediments rarely exceeds the first tens of meters. A significant role belongs to boulder loams - traces of ancient cover glaciations.
Intrusive formations of various ages and compositions are widespread on shields and in folded belts. The most ancient Archean complexes on the shields are represented by orthoamphibolites and other ultramafic and mafic rocks. Younger Archean granitoids make up complexes with an age of 3.2–2.6 billion years. Large massifs form Proterozoic alkaline granites and syenites with a radiological age of 2.6–1.9 billion years. Rapakivi granites with an age of 1.7–1.6 billion years are common in the marginal part of the Baltic Shield. In the northern part of the shield there are intrusions of alkaline syenites of Carboniferous age - 290 million years. In the Tunguska syneclise, along with volcanics, formation intrusions - dolerite sills - are widespread. In the volcanic belts of the Far East, large intrusions of granitoids are developed, which together with volcanics form volcano-plutonic complexes.
In recent decades, extensive work has been carried out to study the adjacent waters, including marine geophysical work and well drilling. They were aimed at searching for hydrocarbon deposits on the shelf, which led to the discovery of a number of unique deposits. As a result, it became possible to show the structure of water areas on a geological map, although in the eastern seas of the Russian sector of the Arctic the map remains largely schematic. Due to insufficient knowledge, it was necessary to show undifferentiated deposits in some places. The marine basins are filled with Mesozoic and Cenozoic sedimentary rocks of great thickness with separate outcrops of Paleozoic and granitoids of different ages on the uplifts.
In the basin, on a Precambrian foundation, a cover of sedimentary rocks is developed with Triassic and Jurassic outcrops along its sides, and in the center - with a wide distribution of the Upper Cretaceous - Paleocene. Under the bottom, a continuation of the West Siberian plate with a cover of Cretaceous and Paleogene can be traced. IN eastern sector In the Arctic, significant parts of the water area are covered by Neogene sediments. Volcanic rocks are developed in the mid-ocean Gakkel Ridge and near the De Long Islands. Near the islands, continuations of Mesozoic and Paleozoic rock outcrops can be traced.
In Okhotsk and from under the continuous cover of Neogene deposits, in some places more ancient sedimentary rocks, volcanics and granitoids emerge, forming relics of microcontinents.
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