The Jurassic period in brief. Jurassic system (period)

And Switzerland. The beginning of the Jurassic period is determined by radiometric method at 185±5 million years, the end - at 132±5 million years; the total duration of the period is about 53 million years (according to 1975 data).

Jurassic system in its modern volume, it was identified in 1822 by the German scientist A. Humboldt under the name “Jurassic formation” in the Jura mountains (Switzerland), Swabian and Franconian Alb (). In the territory, Jurassic deposits were first established by the German geologist L. Buch (1840). The first scheme of their stratigraphy and division was developed by the Russian geologist K. F. Roulier (1845-49) in the Moscow region.

Divisions. All the main divisions of the Jurassic system, which were subsequently included in the general stratigraphic scale, are identified in the territory of Central Europe and Great Britain. The division of the Jurassic system into departments was proposed by L. Buch (1836). The foundations of the staged division of the Jurassic were laid by the French geologist A. d'Orbigny (1850-52). The German geologist A. Oppel was the first to produce (1856-58) a detailed (zonal) division of Jurassic deposits. See table.

Most foreign geologists classify the Callovian Stage as the middle section, citing the priority of the three-member division of the Jurassic (black, brown, white) by L. Bukh (1839). The Tithonian Stage is recognized in the sediments of the Mediterranean biogeographical province (Oppel, 1865); for the northern (boreal) province, its equivalent is the Volgian stage, first identified in the Volga region (Nikitin, 1881).

general characteristics. Jurassic deposits are widespread on all continents and are present in the periphery, parts of ocean basins, forming the base of their sedimentary layer. By the beginning of the Jurassic period, two large continental masses were separated in the structure of the earth's crust: Laurasia, which included platforms and Paleozoic folded regions of North America and Eurasia, and Gondwana, which united the platforms of the Southern Hemisphere. They were separated by the Mediterranean geosynclinal belt, which was the Tethys oceanic basin. The opposite hemisphere of the Earth was occupied by the Pacific Ocean depression, along the margins of which geosynclinal regions of the Pacific geosynclinal belt developed.

In the Tethys oceanic basin, throughout the Jurassic period, deep-sea siliceous, clayey and carbonate sediments accumulated, accompanied in places by manifestations of submarine tholeiitic-basaltic volcanism. The wide southern passive margin of Tethys was an area of ​​accumulation of shallow-water carbonate sediments. On the northern margin, which in different places and at different times had both an active and passive character, the composition of sediments is more variegated: sandy-clayey, carbonate, in places flysch, sometimes with the manifestation of calc-alkaline volcanism. Geosynclinal areas of the Pacific belt developed in the regime of active margins. They are dominated by sandy-clayey sediments, a lot of siliceous ones, and volcanic activity was very active. The main part of Laurasia in the Early and Middle Jurassic was land. In the Early Jurassic, marine transgressions from geosynclinal belts captured only the territories Western Europe, the northern part of Western Siberia, the eastern margin of the Siberian Platform, and in the Middle Jurassic and southern part Eastern European. At the beginning of the Late Jurassic, the transgression reached its maximum, spreading to the western part of the North American platform, the Eastern European platform, all of Western Siberia, the Ciscaucasia and the Transcaspian region. Gondwana remained dry land throughout the Jurassic period. Marine transgressions from the southern edge of Tethys captured only the northeastern part of the African and northwestern part of the Hindustan platform. The seas within Laurasia and Gondwana were vast but shallow epicontinental basins where thin sandy-clayey sediments accumulated, and in the Late Jurassic in areas adjacent to the Tethys - carbonate and lagoonal (gypsum and salt-bearing) sediments. In the rest of the territory, Jurassic deposits are either absent or represented by continental sandy-clayey, often coal-bearing strata, filling individual depressions. The Pacific Ocean in the Jurassic was a typical oceanic basin, where thin carbonate-siliceous sediments and covers of tholeiitic basalts accumulated, preserved in the western part of the basin. At the end of the Middle - beginning of the Late Jurassic, the formation of “young” oceans began; The opening of the Central Atlantic, the Somali and North Australian basins of the Indian Ocean, and the Amerasian basin of the Arctic Ocean occurs, thereby beginning the process of dismemberment of Laurasia and Gondwana and the separation of modern continents and platforms.

The end of the Jurassic period is the time of manifestation of the Late Cimmerian phase of Mesozoic folding in geosynclinal belts. In the Mediterranean belt, folding movements manifested themselves in places at the beginning of the Bajocian, in Pre-Callovian time (Crimea, Caucasus), and at the end of the Jurassic (Alps, etc.). But they reached a particular scale in the Pacific belt: in the Cordillera of North America (Nevadian folding), and the Verkhoyansk-Chukotka region (Verkhoyansk folding), where they were accompanied by the introduction of large granitoid intrusions, and completed the geosynclinal development of the regions.

The organic world of the Earth in the Jurassic period had a typically Mesozoic appearance. Marine invertebrates are thriving cephalopods(ammonites, belemnites), bivalves and gastropods, six-rayed corals, "wrong" sea ​​urchins. Among vertebrates in the Jurassic period, reptiles (lizards) predominated sharply, reaching gigantic sizes (up to 25-30 m) and great diversity. There are known terrestrial herbivores and predatory lizards (dinosaurs), sea-swimming ones (ichthyosaurs, plesiosaurs), and flying lizards (pterosaurs). Fish are widespread in water basins; the first (toothed) birds appear in the air in the Late Jurassic. Mammals, represented by small, still primitive forms, are not very common. The land cover of the Jurassic period is characterized by the maximum development of gymnosperms (cycads, bennetites, ginkgos, conifers), as well as ferns.

Jurassic geological period, Jura, Jurassic system, middle period Mesozoic It began 206 million years ago and lasted 64 million years.

Jurassic deposits were first described in the Jura (mountains in Switzerland and France), hence the name of the period. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a wide variety of conditions.

190-145 million years ago in Jurassic period the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.

Climate

The climate in the Jurassic period was humid and warm (and by the end of the period - arid in the equator region).

During the Jurassic period, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.

Cycads- a class of gymnosperms that predominated in the green cover of the Earth. Nowadays they are found here and there in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Externally, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them among palm trees in his plant system.

During the Jurassic period, groves of ginkgo trees grew throughout the then temperate zone. Ginkgos are deciduous (unusual for gymnosperms) trees with an oak-like crown and small fan-shaped leaves. Only one species has survived to this day - Ginkgo biloba. The conifers were very diverse, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered temperate zone.

Marine organisms

Compared to the Triassic, the population of the seabed has changed greatly. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve mollusks fill all life niches of the seabed. Many stop collecting food from the ground and switch to pumping water using their gills. Folds up new type reef communities, approximately the same as what exists now. It is based on six-rayed corals that appeared in the Triassic.

Land animals

One of the fossil creatures of the Jurassic period, combining the characteristics of birds and reptiles, is Archeopteryx, or the first bird. His skeleton was first discovered in the so-called lithographic shales in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx still flew quite poorly (gliding from tree to tree), and was approximately the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak, jaws. It had free fingers on its wings (of modern birds, only hoatzin chicks have them).

During the Jurassic period, small, furry, warm-blooded animals called mammals lived on Earth. They live next to dinosaurs and are almost invisible against their background.

Dinosaurs of the Jurassic period (“terrible lizards” from Greek) lived in ancient forests, lakes, and swamps. The range of differences between them is so great that family ties between them are established with great difficulty. They could be the size of a cat or chicken, or they could reach the size of huge whales. Some of them walked on all fours, while others ran on their hind legs. Among them were dexterous hunters and bloodthirsty predators, but there were also harmless herbivores. The most important feature common to all their species is that they were terrestrial animals.

Jurassic period (Jurassic)- middle (second) period Mesozoic era. Began 201.3 ± 0.2 million years ago, ended 145.0 million years ago. Thus it continued for about 56 million years. A complex of sediments (rocks) corresponding to a given age is called the Jurassic system. In different regions of the planet, these deposits differ in composition, genesis, and appearance.

First time deposits of this period were described in the Jura (mountains in Switzerland and France); This is where the name of the period came from. The deposits of that time are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates, formed in a wide variety of conditions.

Flora

In the Jurassic, vast areas were covered with lush vegetation, primarily diverse forests. They mainly consisted of ferns and gymnosperms.

Cycads are a class of gymnosperms that predominated in the green cover of the Earth. Nowadays they are found in the tropics and subtropics. Dinosaurs roamed under the shade of these trees. Externally, cycads are so similar to low (up to 10-18 m) palm trees that even Carl Linnaeus placed them among palm trees in his plant system.

During the Jurassic period, groves of gingkovic trees grew throughout the then temperate zone. Ginkgos are deciduous (unusual for gymnosperms) trees with an oak-like crown and small fan-shaped leaves. Only one species has survived to this day - ginkgo biloba.

Conifers were very diverse, similar to modern pines and cypresses, which flourished at that time not only in the tropics, but had already mastered the temperate zone. The ferns gradually disappeared.

Fauna

Marine organisms

Compared to the Triassic, the population of the seabed has changed greatly. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve mollusks fill all life niches of the seabed. Many stop collecting food from the ground and switch to pumping water using their gills. A new type of reef community is emerging, approximately the same as what exists now. It is based on six-rayed corals that appeared in the Triassic.

Land animals of the Jurassic period

One of the fossil creatures that combines the characteristics of birds and reptiles is Archeopteryx, or the first bird. His skeleton was first discovered in the so-called lithographic shales in Germany. The discovery was made two years after the publication of Charles Darwin's On the Origin of Species and became a strong argument in favor of the theory of evolution. Archeopteryx still flew quite poorly (gliding from tree to tree), and was approximately the size of a crow. Instead of a beak, it had a pair of toothy, albeit weak, jaws. It had free fingers on its wings (of modern birds, only hoatzin chicks have them).

During the Jurassic period, small, furry, warm-blooded animals called mammals lived on Earth. They live next to dinosaurs and are almost invisible against their background. In the Jurassic, mammals were divided into monotremes, marsupials and placentals.

Dinosaurs (English Dinosauria, from ancient Greek δεινός - terrible, terrible, dangerous and σαύρα - lizard, lizard) lived in forests, lakes, and swamps. The range of differences between them is so great that family ties between them are established with great difficulty. There were dinosaurs ranging in size from a cat to a whale. Different types of dinosaurs could walk on two or four limbs. Among them were both predators and herbivores.

Scale

Jurassic System Division

The Jurassic system is divided into 3 divisions and 11 tiers:

Belemnite rostra Acrofeuthis sp. Early Cretaceous, Hauterivian

Shells of the brachiopod Kabanoviella sp. Early Cretaceous, Hauterivian

Shell of the bivalve Inoceramus aucella Trautschold, Early Cretaceous, Hauterivian

Skeleton of the saltwater crocodile Stenosaurus, Steneosaurus boltensis Jaeger. Early Jurassic, Germany, Holtzmaden. Among saltwater crocodiles, the Thalattosuchus stenosaurus was the least specialized form. It did not have flippers, but ordinary five-fingered limbs, like those of land animals, although somewhat shortened. In addition, a powerful bone armor made of plates has been preserved on the back and belly.

Three of the specimens presented on the wall (the crocodile Sthenosaurus and two ichthyosaurs - Stenopterygium and Eurynosaurus) were found at one of the world's largest sites of Early Jurassic marine fauna GOLZMADEN (about 200 million years ago; Bavaria, Germany). For several centuries, slate was mined here and used as a building and decorative material.

At the same time, a huge number of remains of invertebrate fish, ichthyosaurs, plesiosaurs and crocodiles were discovered. More than 300 ichthyosaur skeletons alone have been recovered.

Small flying lizards - Sordes were numerous in the vicinity of Lake Karatau. They probably ate fish and insects. Some specimens of Sordes have preserved remains of hair, which is extremely rare in other localities.

Thecodonts- a group pre-new for other archosaurs. The first representatives (1,2) were terrestrial predators with widely spaced limbs. In the process of evolution, some thecodonts acquired a semi-vertical and vertical paw position with a four-legged mode of movement (3,5,6), others - in parallel with the development of bipedality (2,7,8). Most thecodonts were terrestrial, but some of them led an amphibiotic lifestyle (6).

Crocodiles close to thecodonts. Early crocodiles (1,2,9) were terrestrial animals, marine forms with flippers and a caudal fin also existed in the Mesozoic (10), and modern crocodiles are adapted to an amphibiotic lifestyle (11).

Dinosaurs- the central and most striking group of archosaurs. Large predatory carnosaurs (14,15) and small predatory cepurosaurs (16,17,18), as well as herbivorous ornithopods (19,20,21,22) were bipedal. Others used quadrupedal locomotion: sauropods (12,13), ceratopsians (23), stegosaurs (24) and antiposaurs (25). Sauropods and duck-billed dinosaurs (21) adopted an amphibiotic lifestyle to varying degrees. One of the most highly organized among archosaurs were flying lizards (26,27,28), which had wings with a flying membrane, hairline and possibly a constant body temperature.

Birds- are considered direct descendants of Mesozoic archosaurs.

Small terrestrial crocodiles, united in the group of notosuchia (Notosuchia), were widespread in Africa and South America throughout Cretaceous period.

Part of the skull of a sea lizard - pliosaur. Pliosaurus cf. grandis Owen, Late Jurassic, Volga region. Pliosaurs, as well as their closest relatives, plesiosaurs, were perfectly adapted to the aquatic environment. They were distinguished by a large head, short neck and long, powerful, flipper-like limbs. Most pliosaurs had dagger-shaped teeth, and they were the most dangerous predators of the Jurassic seas. This sample, 70 cm long, is only the anterior third of the pliosaur skull, and the total length of the animal was 11-13 m. The pliosaur lived 150-147 million years ago.

Larva of the coptoclava beetle, Coptoclava longipoda Ping. This is one of the most dangerous predators in the lake.

Apparently, in the middle of the Cretaceous period, conditions in the lakes changed greatly and many invertebrates had to move into rivers, streams or temporary reservoirs (caddis flies, the larvae of which build tube houses from grains of sand; flies, bivalves). Bottom sediments of these reservoirs are not preserved, flowing waters wash them away, destroying the remains of animals and plants. Organisms that migrate to such habitats disappear from the fossil record.

Houses made of grains of sand, which were built and carried by caddisfly larvae, are very characteristic of Early Cretaceous lakes. In later eras, such houses are found mainly in flowing waters

Larvae of the caddisfly Terrindusia (reconstruction)

And was replaced by chalk, and had a duration of about 56 million years.

Geography and climate

During the Jurassic period, the supercontinent Pangea began to split into two separate continents:

• the northern part known as Laurasia (which eventually split into North America and Eurasia, opening basins to the Atlantic Ocean and the Gulf of Mexico)
• the southern part - Gondwanaland - drifted east (and eventually divided into Antarctica, Madagascar, India and Australia, and its western part formed Africa and South America).

This process of separation of Pangea, along with warmer global temperatures, allowed reptiles such as dinosaurs to diversify and dominate long time on the ground.

Plant life

During the Mesozoic era, plants developed the ability to lead a terrestrial lifestyle and not be limited only to the oceans. By the beginning of the Jurassic, life came from bryophytes, low-growing bryophytes and liverworts, which had no vascular tissue and were limited to wet, marshy areas.

Ginkgo trees

Ferns and gingaceae, which had roots and vascular tissue for transporting water and nutrients, and reproduced by spores, were the dominant plants of the Early Jurassic. Appeared during the Jurassic period new way plant propagation. Gymnosperms such as coniferous trees, have developed pollen that is distributed over long distances by the wind and pollinates female cones. This method of reproduction made it possible to significantly increase the number of gymnosperms by the end of the Jurassic period. Flowering plants did not evolve until the Cretaceous period.

Age of Dinosaurs

As depicted in the movie Jurassic Park, reptiles were the dominant animal life form during the Jurassic period. They overcame evolutionary obstacles that limited . Reptiles had strong, ossified skeletons with advanced muscular systems for support and movement of the body. Some of the largest animals that ever lived were the dinosaurs of the Jurassic period. Reptiles could also develop amniotic eggs that were incubated on land.

sauropods

Sauropods (lizard-footed dinosaurs) are herbivorous quadrupeds with long necks and heavy tails. Many sauropods, such as brachiosaurs, were huge. Representatives of some genera had a body length of about 25 m, and weight ranged from 50-100 tons, which makes them the largest land animals that have ever existed on Earth. Their skulls were relatively small, with nostrils raised high towards the eyes. Such small skulls meant very small brains. Despite their small brains, this group of animals flourished during the Jurassic period and had a wide geographic distribution. Sauropod fossils have been found on every continent except Antarctica. Other famous dinosaurs The Jurassic includes stegosaurs and flying pterosaurs.

Carnosaurs were one of the main predators of the Mesozoic era. The genus Allosaurus was one of the most widespread carnosaurs in North America. They are similar to later tyrannosaurs, although studies have shown that they have little in common. Allosaurs had strong hind limbs, heavy front legs and long jaws.

Early mammals

Adelobazilevs

Dinosaurs may have been the dominant land animals, but they were not the only fauna. Early mammals were mostly very small herbivores or insectivores, and did not compete with larger reptiles. Adelobasileus is a predatory ancestor of mammals. He had a special structure of the inner ear and jaws. This animal appeared at the end of the Triassic period.

In August 2011, scientists from China announced the discovery of Yuramaya. This tiny mid-Jurassic animal caused excitement among scientists because it was a clear ancestor of placental mammals, indicating that mammals evolved much earlier than previously thought.

Sea life

Plesiosaur

The Jurassic period was also very diverse. The largest sea ​​predators there were plesiosaurs. These carnivorous marine reptiles typically had wide bodies and long necks with four flipper-shaped limbs.

Ichthyosaur is a marine reptile that was most common in the Early Jurassic period. Because some fossils have been found with smaller individuals of their species inside their bodies, it is suggested that these animals may have been among the first to experience internal pregnancy and give birth to live young.

Cephalopods were also widespread during the Jurassic period and included the ancestors of modern squids. Among the most beautiful fossils of marine life are the spiral-shaped shells of ammonites.

According to modern ideas scientists, the geological history of our planet is 4.5-5 billion years. In the process of its development, it is customary to distinguish geological periods of the Earth.

general information

The geological periods of the Earth (the table below) represent the sequence of events that occurred during the development of the planet from the moment the earth's crust was formed on it. Over time, various processes occur on the surface, such as the emergence and destruction of land areas submerged under water and their rise, glaciation, as well as the appearance and disappearance different types plants and animals, etc. Our planet bears obvious traces of its formation. Scientists claim that they are able to record them with mathematical accuracy in different layers of rocks.

Main groups of sediments

Geologists, trying to reconstruct the history of the planet, study rock layers. It is customary to divide these deposits into five main groups, distinguishing the following geological eras of the Earth: ancient (Archean), early (Proterozoic), ancient (Paleozoic), middle (Mesozoic) and new (Cenozoic). It is believed that the border between them runs along the largest evolutionary phenomena that occurred on our planet. The last three eras, in turn, are divided into periods, since the remains of plants and animals are most clearly preserved in these deposits. Each stage is characterized by events that had a decisive influence on the current topography of the Earth.

The oldest stage

The Earth was characterized by rather violent volcanic processes, as a result of which igneous granite rocks appeared on the surface of the planet - the basis for the formation of continental plates. At that time, only microorganisms existed here that could do without oxygen. It is assumed that the deposits of the Archean era cover individual areas of the continents with an almost complete shield; they contain a lot of iron, silver, platinum, gold and ores of other metals.

Early stage

It is also characterized by high volcanic activity. During this period, the mountain ranges of the so-called Baikal fold were formed. They have practically not survived to this day; today they represent only isolated insignificant rises on the plains. During this period, the Earth was inhabited by simple microorganisms and blue-green algae, and the first multicellular organisms appeared. The Proterozoic rock layer is rich in minerals: mica, non-ferrous metal ores and iron ores.

Ancient stage

The first period of the Paleozoic era was marked by the formation of mountain ranges. This led to a significant reduction in sea basins, as well as the emergence of huge areas of land. Individual ridges of that period have survived to this day: in the Urals, Arabia, Southeast China and Central Europe. All these mountains are “worn out” and low. The second half of the Paleozoic is also characterized by mountain-building processes. Ranges were formed here. This era was more powerful; vast mountain ranges arose in the territories of the Urals and Western Siberia, Manchuria and Mongolia, Central Europe, as well as Australia and North America. Today they are represented by very low blocky massifs. Animals of the Paleozoic era are reptiles and amphibians, the seas and oceans are inhabited by fish. Algae predominated among the flora. Palaeozoic It is characterized by large deposits of coal and oil that arose during this era.

Middle stage

The beginning of the Mesozoic era is characterized by a period of relative calm and gradual destruction mountain systems, created earlier, submersion of lowland areas (part of Western Siberia). The second half of this period was marked by the formation of the Mesozoic folding ridges. Very vast mountainous countries appeared, which still have the same appearance today. Examples include the mountains of Eastern Siberia, the Cordillera, and certain areas of Indochina and Tibet. The earth was densely covered with lush vegetation, which gradually died and rotted. Thanks to the hot and humid climate active formation of peat bogs and swamps took place. This was the era of giant lizards - dinosaurs. The inhabitants of the Mesozoic era (herbivores and predators) spread throughout the entire planet. At the same time, the first mammals appeared.

New stage

Cenozoic era, which replaced middle stage, continues to this day. The beginning of this period was marked by an increase in the activity of the internal forces of the planet, which led to a general uplift of huge areas of land. This era is characterized by the emergence of mountain ranges within the Alpine-Himalayan belt. During this period, the Eurasian continent acquired its modern shape. In addition, there was a significant rejuvenation of the ancient massifs of the Urals, Tien Shan, Appalachians and Altai. The climate on Earth changed sharply, and periods of powerful ice sheets began. The movements of glacial masses changed the topography of the continents. As a result, hilly plains with a huge number of lakes were formed. Animals Cenozoic era- these are mammals, reptiles and amphibians, many representatives of the initial periods have survived to this day, others have become extinct (mammoths, woolly rhinoceroses, saber tooth tigers, cave bears and others) for one reason or another.

What is a geological period?

The geological stage as a unit of our planet is usually divided into periods. Let's see what the encyclopedia says about this term. Period (geological) is a large interval of geological time during which formations were formed. rocks. In turn, it is subdivided into smaller units, which are commonly called epochs.

The first stages (Archean and Proterozoic), due to the complete absence or insignificant amount of animal and plant deposits in them, are not usually divided into additional areas. The Paleozoic era includes the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian periods. This stage is characterized the largest number subintervals, the rest were limited to only three. The Mesozoic era includes the Triassic, Jurassic and Cretaceous stages. The Cenozoic era, the periods of which are the most studied, is represented by the Paleogene, Neogene and Quaternary subinterval. Let's take a closer look at some of them.

Triassic

The Triassic period is the first subinterval of the Mesozoic era. Its duration was about 50 million years (beginning 251-199 million years ago). It is characterized by renewal of marine and terrestrial fauna. At the same time, a few representatives of the Paleozoic continue to exist, such as spiriferids, tabulates, some elasmobranchs, etc. Among invertebrates, ammonites are very numerous, giving rise to many new forms important for stratigraphy. Among corals, six-rayed forms predominate, among brachiopods - terebratulides and rhynchonelids, and in the group of echinoderms - sea urchins. Vertebrates are mainly represented by reptiles - large lizard-hipped dinosaurs. Thecodonts are widely distributed - fast-moving land reptiles. In addition, during the Triassic period the first large inhabitants aquatic environment- ichthyosaurs and plesiosaurs, but they reached their peak only in the Jurassic period. Also at this time, the first mammals arose, which were represented by small forms.

Flora during the Triassic (geological) period loses Paleozoic elements and acquires an exclusively Mesozoic composition. Fern plant species, sago, conifers and ginkgos predominate here. Climatic conditions characterized by significant warming. This leads to the drying out of many inland seas, and in the remaining ones the salinity level increases significantly. In addition, the areas of inland water bodies are greatly reduced, resulting in the development of desert landscapes. For example, the Tauride formation of the Crimean Peninsula belongs to this period.

Yura

The Jurassic period gets its name from the Jurassic Mountains in Western Europe. It constitutes the middle part of the Mesozoic and most closely reflects the main features of the development of organic matter of this era. In turn, it is usually divided into three sections: lower, middle and upper.

The fauna of this period is represented by widespread invertebrates - cephalopods (ammonites, represented by numerous species and genera). In terms of sculpture and the nature of their shells, they differ sharply from the representatives of the Triassic. In addition, during the Jurassic period, another group of mollusks flourished - belemnites. At this time, six-rayed reef-building corals, lilies and urchins, as well as numerous elasmobranchs, reach significant development. But the Paleozoic brachiopod species completely disappear. The marine fauna of vertebrate species differs significantly from the Triassic; it reaches enormous diversity. During the Jurassic period, fish, as well as aquatic reptiles - ichthyosaurs and plesiosaurs, were widely developed. At this time, the transition from land and adaptation to marine environment crocodiles and turtles. Various types of terrestrial vertebrates - reptiles - achieve enormous diversity. Among them, dinosaurs come to their heyday, which are represented by herbivores, predators and other forms. Most of them reach 23 meters in length, for example, Diplodocus. In sediments of this period it is found the new kind reptiles - flying lizards, which are called "pterodactyls". At the same time, the first birds appear. The Jurassic flora reaches a lush flourishing: gymnosperms, ginkgos, cycads, conifers (araucarias), bennettites, cycads and, of course, ferns, horsetails and mosses.

Neogene

The Neogene period is the second period of the Cenozoic era. It began 25 million years ago and ended 1.8 million years ago. At this time, significant changes occurred in the composition of the fauna. A wide variety of gastropods and bivalves, corals, foraminifera and coccolithophores. Amphibians have developed widely, sea ​​turtles And bony fish. During the Neogene period, terrestrial vertebrate forms also reached great diversity. For example, rapidly progressing hipparion species appeared: hipparions, horses, rhinoceroses, antelopes, camels, proboscis, deer, hippopotamuses, giraffes, rodents, saber-toothed tigers, hyenas, great apes and others.

Under influence various factors At this time, the organic world is rapidly evolving: forest-steppes, taiga, mountain and lowland steppes appear. In tropical areas - savannas and rain forests. Climatic conditions are approaching modern ones.

Geology as a science

The geological periods of the Earth are studied by the science of geology. It appeared relatively recently - at the beginning of the 20th century. However, despite her youth, she was able to shed light on many controversial issues about the formation of our planet, as well as the origin of the creatures inhabiting it. There are few hypotheses in this science; mostly only observational results and facts are used. There is no doubt that the traces of the planet’s development stored in the earth’s layers will in any case provide a more accurate picture of the past than any written book. However, not everyone can read these facts and understand them correctly, so even in this exact science, erroneous interpretations of certain events may arise from time to time. Where traces of fire are present, it can be confidently stated that there was fire; and where there are traces of water, we can say with equal confidence that there was water, and so on. And yet, mistakes also happen. In order not to be unfounded, let's consider one such example.

"Frosty patterns on glass"

In 1973, the magazine “Knowledge is Power” published an article by the famous biologist A. A. Lyubimtsev, “Frosty patterns on glass.” In it, the author draws readers' attention to the striking similarity of ice patterns with plant structures. As an experiment, he photographed the pattern on the glass and showed the photograph to a botanist he knew. And without hesitation he recognized the fossilized footprint of a thistle in the picture. From a chemical perspective, these patterns arise due to gas-phase crystallization of water vapor. However, something similar happens when producing pyrolytic graphite by pyrolysis of methane diluted with hydrogen. Thus, it was found that dendritic forms are formed away from this flow, which are very similar to plant remains. This is explained by the fact that there are general laws, which control the formation of forms in inorganic matter and living nature.

For a long time, geologists dated each geological period based on traces of plant and animal forms found in coal deposits. And only a few years ago, statements by some scientists appeared that this method was incorrect and that all the fossils found were nothing more than a by-product of the formation of the earth's layers. There is no doubt that everything cannot be measured equally, but it is necessary to approach dating issues more carefully.

Was there a worldwide glaciation?

Let's consider another categorical statement by scientists, and not only geologists. All of us, starting from school, were taught about the worldwide glaciation that covered our planet, as a result of which many species of animals became extinct: mammoths, woolly rhinoceroses and many others. And the modern younger generation is being brought up on the Ice Age quadrology. Scientists unanimously assert that geology is an exact science that does not allow theories, but uses only verified facts. However, this is not the case. Here, as in many areas of science (history, archeology and others), one can observe the ossification of theories and the unshakability of authorities. For example, since the end of the nineteenth century, there have been heated debates on the sidelines of science about whether glaciation occurred or not. In the mid-twentieth century, the famous geologist I. G. Pidoplichko published a four-volume work “On ice age" In this work, the author gradually proves the inconsistency of the version of global glaciation. He does not rely on the works of other scientists, but on geological excavations he personally conducted (and he carried out some of them as a Red Army soldier, participating in battles against German invaders) throughout the Soviet Union and Western Europe. He proves that the glacier could not cover the entire continent, but was only local in nature, and that it was not it that caused the extinction of many species of animals, but completely different factors - these are catastrophic events that led to the displacement of the poles (“Sensational History of the Earth”, A . Sklyarov); and the economic activity of man himself.

Mysticism, or Why Scientists Don't Notice the Obvious

Despite the irrefutable evidence provided by Pidoplichko, scientists are in no hurry to abandon the accepted version of glaciation. And then it gets even more interesting. The author's works were published in the early 50s, but with the death of Stalin, all copies of the four-volume work were confiscated from the country's libraries and universities, preserved only in the library storerooms, and obtaining them from there is very difficult. IN Soviet time everyone who wanted to borrow this book from the library was registered by the secret services. And even today there are certain problems in obtaining this printed edition. However, thanks to the Internet, anyone can familiarize themselves with the works of the author, who analyzes the periods in detail geological history planets, explains the origin of certain traces.

Is geology an exact science?

It is believed that geology is an exclusively experimental science that draws conclusions only from what it sees. If the case is doubtful, then she does not assert anything, expresses an opinion that allows for discussion, and postpones the final decision until unambiguous observations are received. However, as practice shows, exact sciences also make mistakes (for example, physics or mathematics). Nevertheless, mistakes are not a disaster if they are accepted and corrected in a timely manner. Often they are not global in nature, but have local significance; you just need to have the courage to accept the obvious, draw the right conclusions and move on, towards new discoveries. Modern scientists show radically opposite behavior, because most of the luminaries of science at one time received titles, awards and recognition for their activities, and today they do not want to part with them. And this behavior has been noticed not only in geology, but also in other fields of activity. Only strong people are not afraid to admit their mistakes; they rejoice at the opportunity to develop further, because discovering a mistake is not a disaster, but, on the contrary, a new opportunity.