The area is located in the central part of the Moscow syneclise. Its geological structure includes heavily deformed crystalline rocks of the 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 available hydrogeological map at a scale of 1: 200,000, the geological structure of the region 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.
Carboniferous system.
The middle section is the Moscow Stage.
Lower Moscow Substage.
Deposits 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 Vereya, Kashirsky, Podolsky and Myachkovsky horizons stand out.
Vereisky horizon () is ubiquitous. Represented by a pack of oily and silty clays of cherry-red or brick-red color. There are interlayers of limestone, dolomite and flint up to 1m thick. The Vereisky horizon is divided into three strata: Shatsky layers (clays are red with ocher spots); Alyutovskie sequences (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 Vereian horizon in the south is 15-19 m. Determined: Choristites aliutovensis Elvan.
The Kashirsky 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 features, the Kashirsky stratum 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 flank of the syneclise. Rostislavl variegated clays with thin interlayers of limestones and marls with a total thickness of 4-10 m occur in the roof of the Kashirsky horizon. There is no Rostislavl stratum in the central part of the territory. Kashir deposits contain 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 Myachkov horizons.
The deposits of the Podolsky horizon () within the pre-Jurassic erosion valley lie directly under the Mesozoic and Quaternary deposits. In the rest of the territory, they are covered by deposits of the Myachkovo horizon, forming a single stratum with it, represented by gray fractured limestones with clay interlayers. On the deposits of the Kashirsky horizon, the Podolsky stratum overlies with a stratigraphic unconformity. The Podolsky 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 chert concretions, with a total thickness of 40-60 m. 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 the Mesozoic and Quaternary deposits, in the northern and northeastern parts it is overlain by Upper Carboniferous deposits. In the area of the village of V. Myachkovo and near the village. The Kamenno-Tyazhino deposits of the Myachkovian age come to the surface. In the river valley Pakhra and its tributaries have no Myachkovo deposits. The Myachkovsky horizon lies with a stratigraphic unconformity on the deposits of the Podolsky horizon.
The horizon is represented mainly by pure organogenic limestones, sometimes dolomitized with rare interlayers of marls, clays and dolomites. The total thickness of deposits does not exceed 40 m. Myachkovo deposits contain abundant fauna: brachiopods Choristites mosquensis Fish., Teguliferinamjatschkowensis Ivan.
Upper department.
Upper Carboniferous deposits are developed in the northern and northeastern parts of the area under consideration. They are exposed under the Quaternary and Mesozoic formations, and in the area of the city of Gzhel they come to the surface. The Upper Carboniferous is represented by deposits of the Kasimov and Gzhel stages.
Kasimovian stage.
Deposits of the Kasimovian stage are distributed in the northeastern part of the territory. They lie on the Myakkov deposits with erosion.
The Krevyakinsky, Khamovnichesky, Dorogomilovsky and Yauzsky horizons are distinguished in the Kasimovian stage.
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 aquiclude. Horizon thickness up to 18 m.
The Khamovniki horizon is composed of carbonate rocks in the lower part, and clay-marl rocks in the upper part. The total thickness of the deposits is 9-15 m.
The Dorogomilovsky horizon is represented in the lower part of the section by limestone strata, in the upper part by clay and marls. Triticites acutus Dunb are common. Et Condra, Choristites cinctiformis Stuck. The thickness of the deposits is 13-15 m.
The Yauz layers are composed of dolomitic limestones and yellowish, often porous and cavernous dolomites with interlayers of red and bluish carbonate clays. Thickness is 15.5-16.5 m. Triticites arcticus Schellw appears here, Chonetes jigulensis Stuck, Neospirifer tegulatus Trd., Buxtonia subpunctata Nic. The full thickness reaches 40-60 m.
The Gzhel tier () is usually very thin.
The deposits of the Gzhelian stage within the area under consideration are represented by Shchelkovo layers - light gray and brownish-yellow fine-grained or organogenic-clastic, sometimes dolomitic limestones and fine-grained dolomites, in the lower part red clays with limestone interlayers. The total capacity is 10-15m.
Among the Mesozoic deposits in the area described, there are formations of the Jurassic and lower parts of the Cretaceous system.
Jurassic system.
Sediments of the Jurassic system are ubiquitous, except in 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 stand out. The former include undivided deposits 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 the Oxfordian stage of the upper section, as well as deposits of the Volgian regional stage.
The Jurassic deposits rest with angular unconformity on deposits of the Carboniferous system.
Middle department.
The Bathonian and the lower part of the Callovian are combined ()
Continental sediments of the Batian-Callovian age are represented by a sequence of sandy-clayey sediments, gray fine-grained, in some places inequigranular sands with gravel and black clays containing charred plant remains and carbonaceous interlayers. The thickness of these sediments varies 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 under marine sediments of the Upper Jurassic. The output of continental Jurassic deposits on the day surface is observed on the river. Pakhra. The age of the sequence is determined from the remains of the 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 overlies transgressively on the eroded surface of the Upper and Middle Carboniferous or on continental Batian-Callovian deposits. On the territory under consideration, it has been preserved in the form of separate islands within the Main Moscow Hollow. Usually the deposits are brown-yellow and gray sandy-clayey strata with ferruginous oolites with concretions of oolitic marl. Middle Callovian fauna: 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 a 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 marsh nodules containing ferruginous oolites. The Upper Callovian is characterized by Quenstedticeras lamberti Sow. In connection with their erosion in the Oxfordian time, the Upper Callovian deposits have an insignificant thickness (1-3 m) or are completely absent.
Upper department.
Oxford Tier ()
The deposits 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, rarely black, sometimes greenish clays with occasional nodules of oolitic marl. The clays are oily, plastic, sometimes shaly, slightly sandy and slightly micaceous. Phosphorites are dense, black inside. The fauna of 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 insignificant (from 0.7 to several meters).
The upper Oxford differs from the lower in a darker, almost black, color of clays, greater grit content, micacity, and an increase in the admixture of glauconite. There are traces of erosion or shallowing at the boundary between upper and lower Oxford. 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 are noted.
Upper Oxford is characterized by ammonites of the Amoeboceras alternans Buch group. Here are found: Desmosphinctes gladiolus Eichw., Astarta cordata Trd. and others. The average thickness of the Upper Oxfordian ranges from 8 to 11 m, the maximum reaches 22 m. The total thickness of the Oxfordian stage ranges from 10 to 20 m.
Kimmeridgian ()
The deposits of the Kimmeridgian stage lie with a stratigraphic unconformity on the thickness of the rocks of the Oxfordian stage. The deposits are represented by dark gray clays with interlayers of rare phosphorites and pebbles at the base of the sequence. Identified: Amoeboceras litchini Salt, Desmosphinctes pralairei Favre. and others. The layer thickness is about 10 m.
Volga region.
Lower subtier ()
Occurs with erosion on Oxford. The deposits of the lower Volgian stage come to the surface along the banks of the Moscow, Pakhra, and Mocha rivers.
Dorsoplanites panderi Zone. At the base of the lower Volgian stage there is a thin layer of clay-glauconite sand with rounded and thinned phosphorite concretions. 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 consists of three members. The lower member is represented by thin gray-green glauconite clayey sands, sometimes cemented into sandstone, with rare disseminated phosphorites of the clayey-glauconite type and phosphorite pebbles. Here, for the first time, ammonites of the Virgatites yirgatus Buck group were found. The thickness of the member is 0.3-0.4 m. The upper member is composed of black glauconite clayey sands and sandy clays. The thickness of the pack 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 glauconite 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 varies from 7–15 m.
Upper substage ()
The Upper Volgian substage was exposed by boreholes and comes to 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 glauconite sands with fine sandy phosphorites. Here are found: 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, weakly clayey, glauconite sands with sandy phosphorites, rare at the bottom and numerous in the upper part of the sequence. The sandstones contain abundant fauna: Craspedites subditus Trd. Zone thickness 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 glauconite sand or sandstone with intergrowths of phosphorite. The thickness of this sequence does not exceed 3 m, but sometimes it reaches 18 m. Fauna is typical: Craspedites nodiger Eichw., C. kaschpuricus Trd., C. milkovensis Strem., C. mosquensis Geras. The zone reaches a considerable thickness from 3-4 m to 18 m, and in the Lytkarino quarries up to 34 m.
The total thickness of the Upper Volga substage is 5-15 m.
Cretaceous system
Lower section.
Valanginian stage ()
The deposits of the Valanginian stage overlie with stratigraphic unconformity on the rocks of the Volgian regional stage.
At the base of the Valanginian Stage, there is the Riasanites rjazanensis zone - the Ryazan Horizon" - preserved as small islands in the basin of the 30th Moskva 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 ()
The deposits of the lower Valanginian are overlain by the Barremian sandy-argillaceous sequence composed of intercalation of yellow, brown, dark sands, sandy clays, and strongly micaceous argillaceous sandstones with siderite concretions 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 Moskva, Mocha, and Pakhra rivers. At the top, they gradually pass into the Aptian sands. The total thickness of the Barrem 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, in places with plant remains. The total thickness of the Aptian deposits reaches 25 m; the minimum thickness is 3-5 m. Gleichenia delicata Bolch is characteristic.
Albian ()
The deposits of the Albian Stage have been preserved only on the Teplostan Upland. The Aptian deposits lie with stratigraphic unconformity. Under the rough boulders, a 31 m thick sandy-argillaceous deposit was exposed, lying on the gray sands of the Aptian.
Neogene system (N)
Deposits of the Neogene system rest with angular unconformity on Cretaceous deposits.
On the territory under consideration, an alluvial sandy stratum was found. 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 gravel sands, with flint pebbles at the base, in places with interlayers of clays. The sands are diagonally layered, containing pebbles and boulders of local rocks - sandstone, chert and limestone. The total thickness of the Neogene does not exceed 8 m.
Quaternary system (O)
Quaternary deposits (Q) are developed everywhere, overlapping an uneven bed of bedrocks. Therefore, the modern terrain to a large extent repeats the buried relief, which was formed by the beginning of the Quaternary period. Quaternary sediments are represented by glacial formations, which are represented by three moraines (Setun, Don and Moscow) and 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 opened by wells and come to the day surface along the tributaries of the river. Pakhry. Water-bearing rocks are represented by sands with interlayers of loams and clays. Their thickness varies from a few meters to 20 m.
Moraine of the Dnieper glaciation (). Has a wide circulation. Represented by loams with pebbles and boulders. The thickness varies from 20 to 25 m.
Alluvial-fluvioglacial deposits occurring between the moraines of the Moscow and Dnieper glaciations (). Distributed in vast spaces between the rivers and along the valleys of the river. 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.
Moscow glaciation moraine and cover loams (). Distributed everywhere. The deposits are represented by red-brown boulder loam or sandy loam. The thickness is small 1-2 m.
Water-glacial deposits of the time of the retreat of the Moscow glacier () are common 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 floodplain terraces in the valleys of the Moscow, Pakhra 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 loams, loams and clays. The total thickness is 6-15 m, on small rivers and in the bottoms of ravines 5-8 m.
FEDERAL AGENCY FOR EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION
STATE EDUCATIONAL INSTITUTION
HIGHER PROFESSIONAL EDUCATION
BASHKIR STATE UNIVERSITY
Faculty of Geography
Department of Geology and Geomorphology
geological structure of the TERRITORY
Coursework by discipline
"Structural geology and geomapping"
Compiled by: student of group 2.5
Rakhimov I. R.
Head: Associate Professor
Larionov Nikolai Nikolaevich
Ufa 2009
Introduction
1. Physical-geographical sketch
2. Stratigraphy and lithology
3. Tectonics
4. History geological development
5. Minerals
6. Spec (Sedimentary rocks)
Conclusion
INTRODUCTION
This course work sums up the study of the course of structural geology and geomapping.
The main goal of the course work is to consolidate the material in the course of Structural Geology and Geomapping and gain experience in analyzing a geological map, which is an image on a topographic basis using conventional signs, the distribution and condition of the occurrence of rocks on the earth's surface, divided by age, composition and origin.
The objectives of the course work are:
Detailed description of the geological structure of the region of the given area: compilation of a physical and geographical characteristic; study of stratigraphy, tectonics and lithology of the area
Drawing up a geological section
Drawing up an orohydrographic scheme
Drawing up a structural-tectonic scheme
Reconstruction of the history of geological development based on geological materials, section, stratigraphic column
Description of minerals that may be found in the proposed area.
To solve the above problems, an educational geological map No. 1, made on a scale of 1:50000, is analyzed. The relief is depicted by solid horizontal lines drawn every 10 m. Map compiled by D.N. Utekhin, editors: Yu.A. Year of publication - 1984.
The large stratigraphic units of this region are the Carboniferous, Jurassic and Cretaceous systems. The general character of the occurrence of the strata is horizontal.
1. PHYSICAL AND GEOGRAPHICAL OUTLINE
1) Orography
The relief of the described territory is mostly the valley of the Myshega River with its tributaries. The river is undergoing a stage of maturity, as evidenced by the relative flatness of this land area, as well as the widespread occurrence of alluvial deposits that form the river floodplain. Small hills can act as watersheds between the rivers Para and Olkhovka, Olkhovka and Severka, as well as Yagodnaya and Snezhet. The maximum absolute heights do not exceed 201 m. The minimum level is the floodplain in the lower reaches of the river. Myshegi - 115 m. The maximum relative height of 95 m characterizes the relief of a land area with an approximate area of 310 km 2 as flat. The highest mark of this area is a hill to the east of the source of the river. Severki - 200.5 m.
The hills mostly have gentle slopes. Composed of clays, sands and sandstones, they cannot have large values of absolute elevations.
2) Hydrography
The Myshega River is the main one and is a drainage basin for a number of tributaries. Geographically, the riverbed Myshega stretches from west to east. Right tributaries: r. Yagodnaya and r. Snow. Left tributaries: r. Vozha and R. Olkhovka and r. Severka. Also, the left tributaries include three small rivers that do not have a name. The Para River is a tributary of the second order in relation to the river. Myshege.
For this area, the density of the river network is quite high. The Myshega River has low and high floodplains, as well as at least one terrace above the floodplain. Judging by the fact that the river flows through a flat area, it can be judged with accuracy that lateral erosion prevails over bottom erosion. This allows the growth of large numbers of meanders and, given this, the river can be described as meandering.
3) Geographic and economic characteristics of the region
Within the map, we have the opportunity to observe several small settlements - villages. Listing these settlements from north to south, the following sequence will be established: Koty, Dubki, Rozhki, Shukhovo, Koptevo, Kalinovka, Ivanovka, Popovka, Petrovka, Uzkoye, Podlipki, Nelidovo, Petushki, Kolki, Rye, Zlobino, Zhdanovka, Kryukovo, Ermolino , Kuzmino, Olkhovka, Long, Steep, Spawning, Koltsovo, Desired, Berry.
If we talk about the patterns of distribution of these villages, then all of them are located along the banks of the above rivers. highest density settlements observed along the banks of the Myshega. As for the distribution of houses and other buildings in the settlements themselves, their shapes are elongated, apparently along two or three parallel streets.
Two country roads stretch in the meridional direction. The western road passes near the village of Rozhki, through the village of Popovka, the village of Kuzmino, the village of Dolgoe and between the village of Zhelannoye and the village of Yagodnoye. Through the river Myshega passes a wooden bridge connecting Kuzmino and Dolgoye.
The eastern road passes near the village of Ivanovka, then through the river. Myshega on a wooden bridge and through the village of Koltsovo.
In the northeast of the map is Railway and to the south of the village of Koty is the Koty station.
2. STRATIGRAPHY AND LITHOLOGY
The geological structure of this territory involves deposits of the Quaternary, Cretaceous, Jurassic and Carboniferous systems. A characteristic fact for these systems is that they are composed only of sedimentary rocks. The total thickness of the rocks that make up the territory is more than 160 m.
COAL SYSTEM
The deposits of this system are the oldest in the structure of the territory we are describing. The Carboniferous system has outlets in the northwestern and northeastern parts of the map. In addition, deposits of Carboniferous age are exposed in the banks of the Myshega River, as well as in all incised side valleys. The Carboniferous system is represented by the lower section, which includes 2 tiers: Visean and Serpukhovian.
The system is represented by limestones, clays, limestones with layers of dolomite.
Visean stage
The rocks that make up the Visean Stage are represented by dark gray, gray, massive and layered, organogenic-detrital limestones, limestones with interlayers of greenish-gray calcareous clays. Since they are the oldest in this area, the relationship with the underlying rocks has not been established. The total thickness of the stage exceeds 80 m. The stage is subdivided into 5 horizons: Aleksinsky, Mikhailovsky, Venevsky, Tarussky and Steshevsky.
The Aleksinsky Horizon (C1al) of the Visean Stage is represented by gray and dark gray limestones, massive and layered, organogenic-detrital. The total thickness of the deposits of the Aleksinsky horizon is more than 15 m.
The Mikhailovsky Horizon (C1mh) of the Visean Stage is represented by gray microgranular, organogenic-detrital limestones with interlayers of greenish-gray calcareous clays. The thickness of the Mikhailovsky horizon is 20 m.
The Venev Horizon (C1vn) of the Visean Stage is represented by massive light gray limestones with purple and brown spots. The thickness of this horizon is about 15 m.
The Tarusa Horizon (C1tr) of the Visean Stage is represented by light gray layered, microgranular, organogenic-detrital limestones. The thickness of this horizon is 10 m.
The Steshevsky Horizon (C1st) of the Visean Stage is represented by gray shale clays with interlayers of dolomite. Below - fat gray, cherry-red and green clays. The thickness of this layer is 20 m.
Namurian
The Namurian stage is represented by only one horizon, the Protvinsky horizon.
The Protvinsky Horizon (C1pr) of the Namurian Stage is represented by white massive, recrystallized, cavernous limestones. The thickness of the horizon is 15 m.
JURASSIC SYSTEM
The deposits of the Lower Carboniferous system unconformably overlie rocks of the Upper Jurassic system. The Jurassic system is represented by the upper section, which includes three stages: Callovian, Oxfordian, Kimmeridgian. Rock outcrops of this system are located throughout the map. The rocks of this system are represented by gray, silty and sandy clays. The total thickness is 30 m.
Callovian Stage (J3cl). The deposits of the Callovian stage unconformably lie on the Protvinsky horizon of the Serpukhovian stage of the lower part of the Carboniferous system. Gray silty and sandy, calcareous clays compose the Callovian Stage, which is 15 m thick.
Oxfordian Stage (J3ox). This stage is composed of gray, silty and sandy clays, calcareous in places. The layer thickness is 10 m.
Kimmeridgian Stage (J3km). This stage is composed of gray clays, which are about 5 m thick.
CHALK SYSTEM
The Lower Cretaceous deposits unconformably overlie the deposits of the Upper Jurassic system, since the Tithonian stage of the Upper Jura and the Berriasian stage of the Lower Cretaceous fall out of the chronological sequence. Cretaceous deposits have exits on the tops of hills or on their slopes. Only two tiers are presented - Valanginian and Aptian. The described system is composed of green, glauconite sands, quartz and white sandstones, and gray clays. The total thickness is 35 m.
Aptian Stage (K1ap). The deposits of the Aptian Stage unconformably overlie the deposits of the Valanginian Stage with azimuthal unconformity, because deposits of the Hauterivian, Barremian, and Aptian centuries of the late Cretaceous period fall out of the section. This stage unconformably overlies the previous one. It is composed of sands and white quartz sandstones, the thickness of which is 20 m.
3. TECTONICS
The tectonic setting of this region is calm. There are no discontinuous violations, faults. The absence of folding and the horizontal occurrence of sedimentary rocks indicate that this area belongs to the platform cover.
Only by restoring the history of the development of the area, by the presence of stratigraphic unconformities, one can say that the territory was uplifted at certain intervals of time. Namely, the absence of rocks of the middle and upper Carboniferous system and rocks of the Permian and Triassic systems in the section. Also, the Jurassic system is represented only by the upper section, and the Cretaceous only by the lower one. All these conditions characterize positive tectonic movements.
In the Quaternary, there was a decrease in the base of erosion of the main river of the described region.
In this area, 3 main structural stages can be distinguished, which are indicated by the surfaces of stratigraphic unconformities: Lower Carboniferous, Upper Jurassic and Lower Cretaceous.
Lower Carboniferous Floor
The deposits of this structural stage in the analyzed area are represented by only two tiers of the lower section of the Carboniferous system. The rocks of this structural stage come to the surface mainly in the northwestern and northeastern parts of the map; in addition, Carboniferous deposits are exposed in the banks of the Myshega River, as well as in all incised lateral river valleys. The floor is represented by sedimentary deposits - limestones and clays.
Upper Jurassic floor
The deposits of this structural stage in the analyzed area are represented only by the upper section. Outcrops are scattered throughout the map. The floor is represented by clays.
lower chalk floor
This structural stage has become widespread in the southwestern, southeastern, and central parts of the described map. The Lower Cretaceous stage has exits on the tops of hills or on their slopes. The floor is represented by sands, sandstones and clays.
4. HISTORY OF GEOLOGICAL DEVELOPMENT
The history of the geological development of this area can begin to be described from the Carboniferous period. In addition to this period, two more periods of sedimentation are distinguished: Jurassic and Cretaceous. The oldest rocks distributed on the territory of this map are deposits of the Visean Age of the Carboniferous period. Carbonate rocks indicate that this area was in marine conditions. In the Namurian, marine conditions of sedimentation persisted.
Subsequently, deposits of the Early Jurassic period with stratigraphic unconformity accumulated on the rocks of the Carboniferous age. This can be explained by the fact that the transgression of the sea occurred in the Permian period, as evidenced by sandstones in the deposits of the Callovian stage. During the Jurassic, the transgression of the sea continued, as the Kimmeridgian deposits are thinner than the Callovian deposits.
After the Jurassic, there was a break in sedimentation, as evidenced by the stratigraphic unconformity between the Jurassic and Cretaceous systems. This period is represented by sands and clays, which indicates further transgression of the sea. The area was uplifted. Also, after the Valangian age of the Cretaceous period, there was a break in sedimentation, as evidenced by the stratigraphic unconformity between the Valangian and Aptian stages. The sediments of the Aptian Stage are represented by white quartz sands, which suggest that sedimentation took place in the coastal zone.
In general, the sedimentation environment was stable, the tectonic regime was calm.
5.MINERAL RESOURCES
Sedimentary rocks of this territory can theoretically be minerals. Minerals include limestones of the Carboniferous period, which can be used for liming acidic soils in agriculture, can also be used in production. building materials. This natural material is also used to produce lime, cement; in metallurgy - as fluxes. In addition, limestone is used in decorative design exterior and interior walls of rooms.
Plastic gray clays of the Kimeridge stage of the Upper Jurassic, which can be used in sculpture, can also be attributed to minerals. Sandy clays of the Callovian stage can be widely used in the production of bricks.
The white sand of the Aptian stage of the Cretaceous system can be used in decorative plasters and roofing materials. Quartz sands are suitable for construction purposes, roads, and this rock can also be used for glass production.
Phosphorite pebbles are used in chemical raw materials.
Glauconite grains of the Valanginian stage of the Cretaceous system can be used to clean soil and hard surfaces (asphalt, concrete) from oil products, because glauconite has sorption properties.
6. SEDIMENTARY ROCKS
Sedimentary rocks are formed as a result of the redeposition of weathering products and the destruction of various rocks, chemical and mechanical precipitation from water, the vital activity of organisms, or all three processes simultaneously.
Classification of sedimentary rocks
Various geological factors are involved in the formation of sedimentary rocks: the destruction and redeposition of the destruction products of pre-existing rocks, mechanical and chemical precipitation from water, and the vital activity of organisms. It happens that several factors take part in the formation of a particular breed at once. However, some rocks can be formed in different ways. So, limestones can be of chemical, biogenic or detrital origin. This circumstance causes significant difficulties in the systematization of sedimentary rocks. There is no single scheme for their classification yet.
Various classifications of sedimentary rocks were proposed by J. Lapparan (1923), V. P. Baturin (1932), M. S. Shvetsov (1934), L. V. Pustovalov (1940), V. I. Luchitsky (1948), G. I. Teodorovich (1948), V. M. Strakhov (1960), and other researchers.
However, for ease of study, a relatively simple classification is used, which is based on the genesis (mechanism and conditions of formation) of sedimentary rocks. According to it, sedimentary rocks are subdivided into detrital, chemogenic, organogenic, and mixed.
Genesis of sedimentary rocks
"Sedimentary rocks" combine three fundamentally different groups of surface (exogenous) formations, between which there are practically no significant common properties. Actually, chemogenic (salts) and mechanogenic (detrital, partly terrigenous) sedimentary rocks are formed from sediments. Precipitation occurs on the surface of the earth, in its near-surface part and in water basins. But in relation to organogenic rocks, the term "sediment" is often not applicable. So if the sedimentation of the skeletons of planktonic organisms can still be attributed to sediments, then where to attribute the skeletons of benthic, and there more colonial, for example, corals, organisms is not clear. This suggests that the very term "Sedimentary rocks" is artificial, far-fetched, it is archaism. As a result, V. T. Frolov tries to replace it with the term "exolith". Therefore, the analysis of the formation conditions of these rocks should be carried out separately.
In the class of mechanogenic rocks, the first two concepts are equivalent and characterize different properties of this class: mechanogenic - reflects the mechanism of formation and transfer, clastic - composition (consists practically of fragments (the concept is not strictly defined)). The term "terrigenous" reflects the source of the material, although significant masses of detrital material formed under underwater conditions are also mechanogenic.
Mechanogenic sedimentary rocks
This group of rocks includes two main subgroups - clays and clastic rocks. Clays are specific rocks composed of various clay minerals: kaolinite, hydromicas, montmorillonite, etc. Clays released from suspension are called sedimentary clays, in contrast to the residual clays present in the preserved weathering crusts.
General properties of clastic rocks
Clastic rocks are the main part of mechanogenic rocks. Among sedimentary rocks, "clastic rocks" are one of the most common classes of rocks. The scope of this concept corresponds to the ideas of the early periods of the formation of lithology. Initially, they included rocks containing the actual fragments of rocks and minerals, on the one hand, and the products of their mechanical (physical) transformation - rounded grains of rocks and minerals - on the other. But the definition of "fragment" is missing. The situation is the same with the antagonist of "breccia" - pebbles: what is a pebble? There is a narrow definition of the concept of "pebbles", according to which pebbles are limited in linear dimensions. However, in lithology there are also objects that are similar in meaning to pebbles, but of different sizes: boulders, gravel, etc. In a broad sense, "pebbles" (or pellets according to L.V. Pustovalov) - "these are fragments of rocks rolled with water." There is a significant genetic difference between clasts and pellets. "Clastic rocks" - rocks composed only of fragments of parent rocks (minerals). The pellets are not debris in literally and therefore cannot be included in the group of "clastic rocks". They constitute an independent, very common group of sedimentary formations (conglomeroids), composed entirely or mainly of pellets. various sizes(pebbles, gravel, conglomerates, pebbles, gravelstones, etc.)
The main structures of sedimentary rocks are:
clastic - the rock consists of fragments of particles larger than 0.01 mm, pre-existing rocks;
fine-grained (clay or pelitic) - the rock consists of particles smaller than 0.01 mm in size (clay, marl);
crystalline inequigranular - crystals of minerals (rock salt, gypsum) are visually visible in the rock;
cryptocrystalline (afonite) - minerals in the rock are visible only under a microscope (chalk);
detrital - the rock is composed of fragments of shells or fragments of plants.
In sedimentary rocks, primary textures are distinguished - arising during the period of sedimentation (for example, layered) or in not yet hardened, plastic sediment (for example, underwater landslide) and secondary textures - formed at the stage of transformation of sediment into rock, as well as during its further changes (diagenesis, catagenesis, the initial stages of metamorphism).
CONCLUSION
In the course of the course work, the following goals and objectives were achieved:
1) We learned how to analyze geological maps
2) Described in detail the geological structure of the area, compiled a physical and geographical essay. The relief of this territory is generally flat, there are several hills. The main river of the described region is the Myshega River.
3) We found out the stratigraphy, tectonics and lithology of the area. Three systems are distinguished in this area: Carboniferous, Jurassic and Cretaceous, which are represented by sedimentary rocks: limestones, clays, sands, quartz sandstones. The total thickness is over 160 m.
4) This territory can be attributed to the platform cover; there are no folds, faults, or faults.
5) There are three main structural stages: Lower Carboniferous, Upper Jurassic, Lower Cretaceous.
6) Based on the information received about the stratigraphy, tectonics of the occupied territory, we have restored the history of geological development. The sedimentation environment is calm.
A geological profile of the map was drawn along the highlighted line.
Geologically, the territory of Russia consists of a complex mosaic of blocks formed by various rocks that arose over 3.5–4 billion years.
There are large lithospheric plates 100–200 km thick, which experience slow horizontal movements at a rate of about 1 cm/year due to convection (substance flow) in the deep layers of the Earth's mantle. Deep cracks - rifts - are formed during the spreading, and later, during spreading, oceanic depressions appear. The heavy oceanic lithosphere, when changing the movement of plates, sinks under the continental plates in subduction zones, along which oceanic trenches and island volcanic arcs or volcanic belts form at the edges of the continents. When continental plates collide, a collision occurs with the formation of folded belts. In the collision of oceanic and continental plates, an important role is played by accretion - the attachment of alien blocks of the crust, which can be brought thousands of kilometers away when immersed and absorbed by the oceanic in the process of subduction.
At present, most of the 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 volcanic arcs. Kuril Islands and Kamchatka. Within the Eurasian Plate, splits along the Baikal and Momsky rifts are manifested, expressed by the depression of the lake. Baikal and large fault zones in . The boundaries of the plates are highlighted with increased .
In the geological past, as a result of displacement, 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 sedimentary cover. Accordingly, the Aldan and Anabar shields, formed in the Early Precambrian, are distinguished within the Siberian Platforms, as well as vast spaces overlain by sedimentary and volcanic rocks, which are considered as the Central Siberian Plate.
Between the East European and Siberian platforms stretches the Ural-Mongolian collision belt, within which folded systems of a complex structure have arisen. A significant part of the belt is overlain 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 adjoined by heterogeneous folded structures, which arose largely as a result of accretion.
Archaeus. 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. The Archean rocks are highly metamorphosed, up to the granulite facies, and the processes of magmatization and granitization are intensively manifested. For Archean rocks, there are radiological datings in the range of 3.6–2.5 Ga. 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 the shields along with the Archaean. It includes: gneisses, crystalline schists, amphibolites, metavolcanic rocks and marbles in some places.
The Upper Proterozoic in many regions is subdivided into Riphean and Vendian. Compared with the Lower Proterozoic, these rocks are characterized by significantly less metamorphism and dislocation. They form the base of the cover of the platform areas. On the Russian Plate in the Riphean, basic volcanic rocks are widely developed in places, while sandstones, gravelstones, siltstones, and clays predominate in the Vendian. On the Siberian Platform, the Upper Proterozoic is represented by almost non-metamorphosed 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 felsic volcanic rocks are widespread. The Upper Riphean is composed of various terrigenous rocks, limestones and dolomites. At the very top of the Riphean, there are basic effusives and tillite-like conglomerates. The Vendian is composed of sandstones, siltstones, and flyschoid mudstones. In the folded areas framing the Siberian Platform, the Upper Proterozoic has a similar structure.
Paleozoic
The Paleozoic includes 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 facially replaced by bituminous carbonate rocks with interlayers of combustible shale, as well as with reef bodies of algal limestones. The Upper Cambrian is formed by red-colored sandy-clayey rocks, 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 felsic volcanics, as well as sandstones and siltstones with reef limestones, are widespread. The Middle Cambrian falls out of the section. The Upper Cambrian is formed by conglomerates, glauconite 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 limestone, dolomite, and carbonate clays with phosphorite nodules and oil shale. A variety of carbonate rocks are developed on the Siberian Platform in the Lower Ordovician. The Middle Ordovician is composed of calcareous sandstones with interlayers of shell limestones, sometimes with phosphorites. The Upper Ordovician contains sandstones and mudstones with siltstone interbeds. In the Urals, the Lower Ordovician is represented by phyllite-like shales, quartzite-like sandstones, gravelstones, and conglomerates with limestone interlayers and locally with basic volcanic rocks. The Middle and Upper Ordovician are composed mainly of terrigenous rocks in the lower part, and limestones 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 are common with interlayers of marls, dolomites, and mudstones. The Upper Silurian contains red-colored rocks, including dolomites, marls, clays, and gypsums. In the Western Urals, in the Silurian, dolomites and limestones are developed, in places clay shales. To the east, they are replaced by volcanic rocks, including basalts, albitophyres, and siliceous tuffites. Within the accretion belt in northeastern Russia, Silurian deposits are diverse in composition. Carbonate rocks are developed in the Upper Silurian: red-colored 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 predominate with limestones in the upper part of the section.
The Devonian system on the Russian plate differs significantly in structure in its various parts. In the west, at the base of the Devonian, limestones, dolomites, marls, and small-pebble conglomerates are developed. In the Middle Devonian, rock salt appears together with red-colored terrigenous rocks. The upper part of the section is distinguished by the development of clays and marls with layers of dolomites, anhydrites and rock salt. In the central part of the plate, the volume of terrigenous rocks increases. In the east of the plate, together with red-colored rocks, bituminous limestones and shales are widespread, which stand out as a domanic formation. On the Siberian platform, the Devonian in its northwestern part is composed of evaporites, carbonate and clayey deposits, in the eastern part - volcanic-sedimentary rocks with layers of rock salt and evaporites. In some areas in the south of the platform, coarse-clastic 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 are also common with an admixture of sandstones, siltstones, argillaceous and siliceous shales. The Upper Devonian begins with a sandy-clayey stratum. Limestones with layers of marls, dolomites and bituminous shales lie above. 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 some places in the Devonian deposits of the Urals, bauxites are noted. In the Verkhoyansk-Chukotka folded system, the Devonian is represented mainly by limestones, clay shales and siltstones. The section of the Kolyma-Omolon massif has significant differences, where volcanic rocks, including rhyolites and dacites, accompanied by tuffs, spread in the Devonian. In the more southern regions of the accretion belt in northeastern Russia, predominantly terrigenous rocks are distributed, in places reaching high power.
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, limestones are predominantly distributed in the lower part of the Carboniferous, and sandstones and siltstones are distributed above. In the west of the Urals, the Carboniferous is formed mainly by limestones, sometimes with layers of dolomites 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 sequences are common, 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 are involved in the structure of the folded belt in the northeast of Russia. Clayey and siliceous shales are common in the southern regions of this belt, often accompanied by volcanic rocks of intermediate and basic composition.
The Permian system on the Russian Plate in the lower part is represented by limestones, which are replaced up the section by evaporites, in places with rock salt. In the Upper Permian, in the east of the plate, sandy-argillaceous red-colored deposits arose. In the more western regions, deposits of mixed composition are common, including sandstones, siltstones, clays, marls, limestones, and dolomites. In the upper part of the section, among the terrigenous rocks, there are variegated marls and red-colored clays. On the Siberian platform, the Permian is composed mainly of terrigenous rocks, in places with coal beds, and also with interbeds of argillaceous limestones. In folded systems 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 includes 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 brown coal seams and kaolin sands. On the Siberian platform, the Tunguska syneclise was formed by Triassic rocks. Here, in the Triassic, lavas and tuffs of basalts of great thickness were formed, attributable to the trap formation. Sandstones, siltstones and mudstones of great thickness are developed in the Verkhoyansk folded system. Within the accretion belt in the Far East, limestones, siliceous rocks, and volcanic rocks of intermediate composition are manifested.
The Jurassic system on the Russian Plate is represented in the lower part by sandy-argillaceous 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 nodules of phosphorites, sometimes with oil shale. On the Siberian platform, Jurassic deposits fill individual depressions. In the Lena-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. The folded systems of the Far East in the Jurassic are dominated by terrigenous rocks, accompanied by siliceous shales and volcanic rocks of intermediate and felsic composition.
The Cretaceous system on the Russian Plate is composed of terrigenous and rocks with nodules of phosphorites and glauconite. The upper part of the section is distinguished by the appearance of limestones, as well as marls and writing chalk, flasks and tripoli, in places with abundant flint concretions. On the Siberian platform, various terrigenous rocks are widespread, in some areas containing layers of coals and lignites. In the folded systems of the Far East, mainly terrigenous rocks of large thickness are distributed, 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. On and chalk is composed of terrigenous rocks of great thickness, along with siliceous rocks and volcanic rocks.
Cenozoic
The Paleogene system on the Russian Plate is composed of flasks, sandstones and siltstones, in some areas marls and phosphorite-bearing sands. On the West Siberian Plate, the Paleogene is formed by flasks, diatomites, mudstones, and sands. In places there are interlayers of iron and manganese ores. Lenses of brown coals and lignites are present in some areas. 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 above - Pliocene limestones. On the West Siberian Plate, the Neogene is represented mainly by clays. Pebbles, sands and clays are widespread in the Far East in the Neogene. A significant role belongs to volcanic rocks, which are especially common in Kamchatka and the Kuril Islands.
The Quaternary system (quaternary) is manifested almost everywhere, but the thickness of the deposits rarely exceeds a few tens of meters. A significant role is played by boulder loams, traces of ancient ice sheets.
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 ultrabasic and basic rocks. Younger Archean granitoids compose complexes with an age of 3.2–2.6 Ga. Large massifs form alkaline granites and syenites of the Proterozoic with a radiological age of 2.6–1.9 Ga. In the marginal part of the Baltic Shield, rapakivi granites with an age of 1.7–1.6 Ga are common. Intrusions of alkaline syenites of Carboniferous age - 290 Ma are distinguished in the northern part of the shield. In the Tunguska syneclise, along with volcanics, bedded intrusions - dolerite sills - are widespread. In the volcanic belts of the Far East, large intrusions of granitoids are developed, which together with volcanic rocks form volcano-plutonic complexes.
In recent decades, extensive work has been carried out to study the adjacent water areas, including offshore geophysical work and well drilling. They were sent to search for hydrocarbon deposits on the shelf, which led to the discovery of a number of unique fields. 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 study, it was necessary to show undivided deposits in some places. The marine basins are filled with thick Mesozoic and Cenozoic sedimentary rocks with separate outcrops of Paleozoic and granitoids of different ages on uplifts.
In the basin, on the Precambrian basement, a cover of sedimentary rocks is developed with outcrops of the Triassic and Jurassic 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 Cretaceous and Paleogene cover is traced. In the eastern sector of the Arctic, significant parts of the water area are covered by Neogene sediments. Volcanic rocks are developed in the Gakkel mid-ocean ridge and near the De Long Islands. Near the islands, continuations of outcrops of Mesozoic and Paleozoic rocks can be traced.
In Okhotsk, and from under a continuous cover of Neogene deposits, older sedimentary rocks, volcanics and granitoids, forming relics of microcontinents, protrude in places.
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GEOLOGICAL STRUCTURE AND HISTORY OF THE DEVELOPMENT OF THE TERRITORY
The Omsk Region is located within the young West Siberian Platform* (Hercynian Plate). In the geological structure of its territory, a folded basement composed of Paleozoic and pre-Paleozoic rocks and a platform cover with gently sloping Mesozoic and Cenozoic deposits are clearly distinguished.
The foundation has a complex structure and consists of igneous formations (granites, diabases, etc.), volcanic tuffs, and metamorphosed rocks (gneisses, shales) to varying degrees. The basement rocks are folded into complex folds and crossed by faults of northeast and northwest strike. Along these faults, some sections-blocks of the foundation fell, others rose. As a result of tectonic movements of the foundation blocks, deflections and protrusions were formed on its surface.
As scientists have established with the help of the latest geophysical data and satellite images, there are peculiar “basalt windows” in the foundation - blocks made up of oceanic crust, and ring structures.
The surface of the foundation plunges from south to north. So, in the south of the region, the foundation is opened by wells at a depth of several hundred meters, in Omsk - 2936 m, in the Kormilovsky district (state farm "Novo-Alekseevsky") - 4373 m.
The platform sedimentary cover in the lower part of the section repeats the basement topography 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. A thick sedimentary cover was formed over tens of millions of years over six geological periods (240 million years).
During this time, the earth's crust experienced slow vertical oscillations. When lowering its sea waters flooded vast territories. In the warm seas formed, a rich organic world developed, contributing to the formation of marine sedimentary strata. Then the lowering of the earth's crust was replaced by an uplift, the sea became shallow and gradually disappeared, the territory of the region became flat land with numerous lakes and rivers. Terrestrial vegetation was widely developed. These events were repeated many times.
For the entire geological history 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. top The cover (250-300 m) is composed 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 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 (anthropogen) 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 glaciation in the north of the region there was tundra, to the south of it - forest-tundra, then forest-steppe. | Of the animals lived mammoth, woolly rhinoceros, bison, giant deer. The vegetation is close to modern. | Covering 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 is covered with coniferous-deciduous forests. The climate is moderately warm and humid. By the end of the period, temperature and humidity decrease. Forest-steppe and steppe appear. | Small-leaved tree species are widely used. Animal world – mastodons, proboscis, ancient horses, rhinos, hippos, saber-toothed tiger, etc. The emergence of man. | Sands, sandy loams, loams, clays, concretions, and lignites formed in lakes, swamps, and rivers. Neogene rocks are found in the bluffs of the Irtysh, Om, Tara, and other rivers. | |||||
| KAYNOZOYSKAYA | Paleogene (Paleogene) 40.4 | At the beginning of the Paleogene, a short uplift of the earth's crust, and then a long subsidence and the advance of the sea on land. At the end of the period, the subsidence was replaced by the rise and retreat of the sea. | For almost 30 million years, the Paleogene Sea existed in the region. At the end of the Paleogene, the mora becomes shallow and breaks up into lake basins. The resulting land was covered with coniferous-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, and protozoa - radiolarians, diatoms, and others. On land, the flowering of ungulates and predators. | Clays with interlayers 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 began, the retreat of the sea. In the second half of the Cretaceous, the earth's crust subsides and the entire area is flooded by the sea. | In the first half of the Cretaceous, the region was flat land covered with coniferous forests. In the forests grew: pine, spruce, cedar and heat-loving tropical plants. The climate is subtropical, humid. In the future, a warm sea existed on the territory of the region, the water temperature was 20 ° C. From time to time, 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 a maximum in the Late Jurassic. This sinking 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, the entire region was occupied by the sea, which existed for 25 million years. | The sea was inhabited by numerous cephalopods - ammonites, belemnites, fish, algae. Coniferous, 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 many plant remains and a layer of coals. 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. Locally volcanic. | Raised plain. There were vast forests. The climate is hot, arid. | The forests are dominated by gymnosperms. | Deposits are rare. Mudstones, siltstones, sandstones. Volcanic rocks - diabases. | |||||
| Paleozoic | Perm (Permian) 38.0 | General uplift of the region. The entire territory is a single stable paraplatform linking the Siberian and Russian platforms. | Area of plateaus and uplands with developed erosion processes. The climate is hot and dry. | On land, the development of terrestrial reptiles, conifers, the appearance of ginkgo. At the end of the period, the extinction of trilobites, four-pointed corals. some molluscs and brachiopods. | Clastic material supplied from surrounding mountain structures. | ||||
| Hard coal (carbon) 74.0 | A time of relatively calm tectonic activity. Deflection of the territory and transgression of the sea. At the end of the period, the general uplift of the earth's crust. Sea regression. Volcanic activity is not 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 club mosses, the first gymnosperms. Widespread distribution of large insects. In the seas there are bony and cartilaginous fish, 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, the revival of deep faults, and an outbreak of volcanism. | The land is a desert, on the southern outskirts of which volcanoes were located. | Wide distribution of bony and cartilaginous fish. On land, there are tree-like ferns, horsetails and club mosses. Appearance of the first amphibians and insects. | Volcanogenic sedimentary rocks. clay, sand, limestone. | |||||
| Silurian (Silur) 30.0 | The West Siberian Platform is a continuation of the Siberian Platform. It shows active tectonic processes. | Noticeable restructuring of paleolandscapes. At the beginning of the period, the territory is dominated by mountainous land, at the end by a flat desert plain. | The first land plants (psilophytes). In the seas there are graptolites, corals, brachiopods, trilobites. | Terrigenous sediments, saline and gypsum-bearing, are probable. | |||||
| Ordovician (Ordovician) 67.0 | Deflection of the earth's crust. | The seas are warm and normally salty with numerous islands and underwater volcanoes. | Appearance of the first fish. The flourishing of trilobites, corals. On the seabed there are bryozoans and graptolites. | Effusive and terrigenous formations. | |||||
| Cambrian (Cambrian) 65.0 | Most of the territory of Western Siberia has lost the features of the geosyncline. A para-platform was formed. | Bring the transgression of the sea! to the dismemberment of land. Widespread areas of underwater volcanism. The sea is shallow water with high salinity. | Wide distribution of marine invertebrates: trilobites, archaeocyaths, four-beam corals. Active development of blue-green algae. | Effusive 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 tasks.
Relief - a set of irregularities of 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) relief forms.
The territory of Russia is distinguished by a very diverse relief. Here are high lores and low plains. 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, Sayans, the mountains of Transbaikalia. Therefore, most of the major rivers (Ob, Irtysh, Yenisei, Lena, Yana, Indigirka, Kolyma) flow from south to north. The general slope of the relief to the north is associated with the subduction of the African-Arabian and Hindustan lithospheric plates under the Eurasian one. In the area of their contact, the sedimentary layers of the earth's crust are uplifted and crushed into folds, and high mountains are formed. In the zone of contact of plates, intensive movements of sections of the earth's crust occur. They are accompanied by earthquakes.
In the east of our country, in the Baikal and Transbaikalia, parts of the Eurasian lithospheric plate - the Chinese and Siberian platforms - interact. In the zone of their contact, vast areas of the earth's crust are cracking, and a deep basin of Lake Baikal is being formed.
Russia is divided by the Yenisei valley into two parts - the eastern uplifted and the 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) ones: West Siberian, Scythian, Turan. The foundation of young platforms (slabs) is submerged to various depths under the sedimentary cover. In the area of ancient platforms, the foundation in some places comes to the surface, forming the so-called shields (Baltic on the Russian platform, Anabar and Aldan - on the Siberian).
The largest East European Plain is located on the Russian platform. Its surface is characterized by an alternation of uplands (Central Russian, Volga, Smolensk-Moscow) and lowlands (Oka-Donskaya).
In the interfluve of the Yenisei and Lena, there is a vast Central Siberian Plateau (on average, it has a height of 500-800 m). It is complicated by a number of large plateaus and ancient ridges (the Putorak plateau, the 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 swampy surface and a concave shape.
In the south, a section of the young Alpine geosynclinal belt adjoins the Russian Plain. In the relief, it is expressed by the Caucasian mountainous country, within which the highest point of Russia, Elbrus (5642 m), is located.
The entire territory of Siberia from the south is also closed by a mountain belt stretching along the border of Russia. These are mainly mountain systems of medium height - Altai, Salair Ridge, Kuznetsk Alatau, Western and Eastern Sayans, mountains of Tuva, Baikal, Transbaikalia and Stanovoy Uplands. 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, confined to massifs of Mesozoic folding (Chersky, Verkhoyansk, Kolyma and Kolyma and Koryak highlands) prevails.
Kamchatka, about. Sakhalin and the ridge of the Kuril Islands belong to the area of young Pacific folding. There are about 200 sleeping and active volcanoes and many earthquakes are recorded every year. This testifies to the ongoing intensive processes in our days. earth's crust at the junction of the Pacific and Eurasian lithospheric plates.
The vast territory, the abundance of landforms and the complexity of the geological structure of Russia led to the presence of a wide range of minerals.
The largest and largest landforms owe their origin to the internal forces of the Earth. But many important details their modern appearance created by external forces.
Almost everywhere on the territory of Russia, the formation of the modern relief took place and is taking place under the influence of flowing waters. As a result, erosional landforms appeared - river valleys, gullies and ravines. The ravine-gully network is especially dense in the Central Russian and Volga uplands and in the foothills.
The relief of many coastal plains is associated with the retreat and advance of the sea.
Such are the plains of the Caspian, Azov, Pechora and northern parts of the West Siberian lowlands.
Covering Quaternary glaciations created specific landforms in the northern half of the European part, and also (to a lesser extent) in Siberia.
Mountain glaciers also significantly influenced the topography of the mountains in the Quaternary. For the most high mountains there are glaciers even now.
In some regions of Russia there are relief forms created by the activity of the wind (Caspian lowland, Kaliningrad region). 64% of Russia's territory is within the permafrost zone. Special landforms are also associated with this zone - heaving mounds, subsidence of the pound, etc.