Jurassic period. Key Features. Jurassic system (period) Who lived in the Jurassic 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).

The Jurassic system in its modern extent was identified in 1822 by the German scientist A. Humboldt under the name “Jurassic formation” in the Jura mountains (Switzerland), Swabian and Franconian Albs (). 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 separated in the structure of the earth’s crust: Laurasia, which included platforms and Paleozoic folded areas of North America and Eurasia, and Gondwana, which united platforms 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 outskirts, which is in different places and in different time had both an active and passive character, the composition of the sediments was 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, northern part 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, transgression reached its maximum, spreading to the western part of the North American platform, the eastern European platform, the entire Western Siberia, Ciscaucasia and Transcaspian region. Gondwana remained dry land throughout the Jurassic period. Marine transgressions from the southern edge of Tethys involved only northeastern part African and northwestern part of the Hindustan platforms. 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 period- this is the middle Mesozoic era. This piece of history is primarily famous for its dinosaurs, it was very good time for all living things. During the Jurassic period, for the first time, reptiles dominated everywhere: in water, on land and in the air.
This period was named in honor mountain range in Europe. The Jurassic period began about 208 million years ago. This period was more revolutionary than the Triassic. This revolutionary spirit was with those estates that came from earth's crust, because it was during the Jurassic period that the continent of Pangea began to diverge. Since that time the climate has become warmer and more humid. In addition, the water level in the world's oceans began to rise. All this provided great opportunities for animals. Due to the fact that the climate became more favorable, plants began to appear on land. And corals began to appear in shallow waters.

The Jurassic period lasted from 213 to 144 million years ago. At the very beginning of the Jurassic period, the climate throughout the Earth was dry and warm. All around were deserts. But later they began to be saturated with moisture by heavy rains. And the world became greener, lush vegetation began to bloom.
Ferns, conifers and cycads formed vast swampy forests. Araucarias, thujas, and cycads grew on the coast. Ferns and horsetails formed extensive forested areas. At the beginning of the Jurassic period, about 195 million years ago. Throughout the northern hemisphere, the vegetation was quite monotonous. But already starting from the middle of the Jurassic period, about 170-165 million years ago, two (conditional) plant belts were formed: northern and southern. In the northern plant belt ginkgo and herbaceous ferns predominated. During the Jurassic period, ginkgos were very widespread. Groves of ginkgo trees grew throughout the belt.

The southern plant belt was dominated by cycads and tree ferns.
Ferns from the Jurassic period survive today in some parts of the wild. Horsetails and mosses were almost no different from modern ones. The habitats of ferns and cordaites of the Jurassic period are now occupied by tropical forests, consisting mainly of cycads. Cycads are a class of gymnosperms that dominated the green cover of the Jurassic 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 they were even initially identified as palm trees in the plant system.

In the Jurassic period, ginkgos were also common - deciduous (which is 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 first cypress and, possibly, spruce trees appear precisely during the brisk period. Coniferous forests of the Jurassic period were similar to modern ones.

During the Jurassic period, temperate climate. Even arid zones were rich in vegetation. Such conditions were ideal for the reproduction of dinosaurs. Among them are the lizard and ornithischians.

Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had a long neck, small head and long tail. They had two brains: one small one in the head; the second is much larger in size - at the base of the tail.
The largest of Jurassic dinosaurs there was a brachiosaurus that reached a length of 26 m and weighed about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of Jurassic lakes and fed on aquatic vegetation. Every day, the brachiosaurus needed at least half a ton of green mass.
Diplodocus is the oldest reptile, its length was 28 m. It had a long thin neck and a long thick tail. Like a brachiosaurus, Diplodocus walked on four legs, the hind legs being longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.

Brontosaurus was relatively tall, had a large hump on its back and a thick tail. Chisel-shaped small teeth were densely located on the jaws of the small head. The brontosaurus lived in swamps and on the shores of lakes. Brontosaurus weighed about 30 tons and was over 20 in length. Lizard-footed dinosaurs (sauropods) were the largest land animals known so far. All of them were herbivores. Until recently, paleontologists believed that such heavy creatures were forced to carry out most your life in the water. It was believed that on land his shin bones would “break” under the weight of the colossal carcass. However, the findings recent years(in particular, the remains of the legs) indicate that sauropods preferred to wander in shallow water; they also entered solid ground. Relative to body size, brontosaurs had an extremely small brain, weighing no more than a pound. There was an expansion in the area of ​​the sacral vertebrae of the Brontosaurus spinal cord. Being much larger than the brain, it controlled the muscles of the hind limbs and tail.

Ornithischian dinosaurs are divided into bipeds and quadrupeds. Different in size and appearance, they fed mainly on vegetation, but predators also appeared among them.

Stegosaurs are herbivores. Stegosaurs are especially abundant in North America, from where several species of these animals are known, reaching a length of 6 m. The back was steeply convex, the height of the animal reached 2.5 m. The body was massive, although the stegosaurus moved on four legs, its forelimbs were much shorter than its hind limbs. On the back there were large bone plates in two rows that protected the spinal column. At the end of the short, thick tail, used by the animal for protection, there were two pairs of sharp spines. Stegosaurus was a vegetarian and had an exceptionally small head and correspondingly tiny brain, little more than walnut. Interestingly, the expansion of the spinal cord in the sacral region, associated with the innervation of the powerful hind limbs, was much larger in diameter than the brain.
Many scaly lepidosaurs appear - small predators with beak-shaped jaws.

Flying lizards first appeared in the Jurassic period. They flew using a leathery shell stretched between the long finger of the hand and the bones of the forearm. Flying lizards were well adapted to flight. They had light tube-shaped bones. The extremely elongated outer fifth digit of the forelimbs consisted of four joints. The first finger looked like a small bone or was completely absent. The second, third and fourth fingers consisted of two, rarely three bones and had claws. The hind limbs were quite developed. There were sharp claws at their ends. The skull of flying lizards was relatively large, usually elongated and pointed. In old lizards, the cranial bones fused and the skulls became similar to the skulls of birds. The premaxillary bone sometimes grew into an elongated toothless beak. Toothed lizards had simple teeth and sat in recesses. The largest teeth were in the front. Sometimes they stuck out to the side. This helped the lizards catch and hold prey. The spine of animals consisted of 8 cervical, 10-15 dorsal, 4-10 sacral and 10-40 caudal vertebrae. The chest was wide and had a high keel. The shoulder blades were long pelvic bones have grown together. The most typical representatives of flying lizards are pterodactyl and rhamphorhynchus.

Pterodactyls were in most cases tailless, varying in size - from the size of a sparrow to a crow. They had wide wings and a narrow skull elongated forward with a small number of teeth in the front. Pterodactyls lived in large flocks on the shores of the lagoons of the Late Jurassic Sea. During the day they hunted, and at nightfall they hid in trees or rocks. The skin of pterodactyls was wrinkled and bare. They ate mainly fish, sometimes sea ​​lilies, mollusks, insects. In order to fly, pterodactyls were forced to jump from cliffs or trees.
Rhamphorhynchus had long tails, long narrow wings, a large skull with numerous teeth. Long teeth of varying sizes curved forward. The lizard's tail ended in a blade that served as a rudder. Rhamphorhynchus could take off from the ground. They settled on the banks of rivers, lakes and seas, feeding on insects and fish.

Flying lizards lived only in the Mesozoic era, and their heyday occurred in the Late Jurassic period. Their ancestors were, apparently, extinct ancient reptiles pseudosuchians. Long-tailed forms appeared earlier than short-tailed ones. At the end of the Jurassic period they became extinct.
It should be noted that flying lizards were not the ancestors of birds and bats. Flying lizards, birds and the bats each originated and developed in its own way, and there are no close ones between them family ties. The only thing they have in common is the ability to fly. And although they all acquired this ability due to changes in the forelimbs, the differences in the structure of their wings convince us that they had completely different ancestors.

The seas of the Jurassic period were inhabited by dolphin-like reptiles - ichthyosaurs. They had a long head, sharp teeth, big eyes surrounded by a ring of bone. The length of the skull of some of them was 3 m, and the length of the body was 12 m. The limbs of ichthyosaurs consisted of bone plates. The elbow, metatarsus, hand and fingers differed little from each other in shape. About a hundred bone plates supported the wide flipper. The shoulder and pelvic girdles were poorly developed. There were several fins on the body. Ichthyosaurs were viviparous animals.

Plesiosaurs lived alongside ichthyosaurs. Appearing in the Middle Triassic, they reached their peak already in the Lower Jurassic; in the Cretaceous they were common in all seas. They were divided into two main groups: long-necked with a small head (plesiosaurs proper) and short-necked with a rather massive head (pliosaurs). The limbs turned into powerful flippers, which became the main organ of swimming. More primitive Jurassic pliosaurs come mainly from Europe. A plesiosaur from the Lower Jurassic reached a length of 3 m. These animals often went ashore to rest. Plesiosaurs were not as agile in water as pliosaurs. This deficiency was to a certain extent compensated for by the development of a long and very flexible neck, with the help of which plesiosaurs could grab prey with lightning speed. They ate mainly fish and shellfish.
During the Jurassic period, new genera of fossil turtles appeared, and at the end of the period, modern turtles appeared.
Tailless frog-like amphibians lived in fresh water bodies.

IN Jurassic seas there were a lot of fish: bony fish, stingrays, sharks, cartilaginous fish, and ganoid fish. They had an internal skeleton made of flexible cartilaginous tissue impregnated with calcium salts: a dense bony scaly covering that protected them well from enemies, and jaws with strong teeth.
Among the invertebrates in the Jurassic seas, there were ammonites, belemnites, and crinoids. However, in the Jurassic period there were much fewer ammonites than in the Triassic. Jurassic ammonites differ from Triassic ammonites in their structure, with the exception of phyloceras, which did not change at all during the transition from the Triassic to the Jurassic. Certain groups of ammonites have preserved mother-of-pearl to this day. Some animals lived in the open sea, others inhabited bays and shallow inland seas.

Cephalopods - belemnites - swam in whole schools in the Jurassic seas. Along with small specimens, there were real giants - up to 3 m long.
Remains of belemnite internal shells, known as “devil's fingers,” are found in Jurassic sediments.
In the seas of the Jurassic period we received significant development also bivalves, especially those belonging to the oyster family. They begin to form oyster banks. The sea urchins that settled on the reefs are undergoing significant changes. Along with the round forms that have survived to this day, there lived bilaterally symmetrical irregular shape hedgehogs Their body was stretched in one direction. Some of them had a jaw apparatus.

The Jurassic seas were relatively shallow. Rivers brought muddy water into them, delaying gas exchange. The deep bays were filled with rotting remains and silt containing, a large number of hydrogen sulfide. That is why in such places the remains of animals brought in are well preserved. sea ​​currents or waves.
Many crustaceans appear: barnacles, decapods, phyllopods, freshwater sponges, among insects - dragonflies, beetles, cicadas, bugs.

Deposits of coal, gypsum, oil, salt, nickel and cobalt are associated with Jurassic deposits.

Geological events

213-145 million years ago, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them.

Climate

The climate in the Jurassic was highly variable.

From the Aalenian to the Bathonian ages, the climate was warm and humid. Then there was glaciation, which occupied most of the Callovian, Oxfordian and the beginning of the Kimmeridgian, and then the climate warmed again.

Vegetation

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

Land animals

One of the fossil creatures that combines characteristics of birds and reptiles is Archeopteryx. 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 work "On the Origin of Species" and became a strong argument in favor of the theory of evolution - it was initially considered transitional form from reptiles to birds. But later it was also proposed that this was a dead-end branch of evolution, not directly related to real birds. Archeopteryx flew rather poorly (gliding from tree to tree), and was approximately the size of a crow. Instead of

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 during the 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 what was 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.

Marine organisms

Compared to the Triassic, the population of the seabed has changed greatly. Bivalves push out 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 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. There were free fingers on his wings (from modern birds they are preserved only in hoatzin chicks).

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. Were among them clever hunters And bloodthirsty predators, but there were also harmless herbivorous animals. Key Feature common to all their species is that they were land animals.

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 up the basins to Atlantic Ocean, and the Gulf of Mexico)
• the southern part - Gondwanaland - drifted east (and eventually divided into Antarctica, Madagascar, India and Australia, and its West Side, formed Africa and South America).

This process of Pangea's separation, along with warmer global temperatures, allowed reptiles such as dinosaurs to diversify and dominate the Earth for long periods of time.

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 have roots and vascular tissue for transporting water, and nutrients, and also reproducing 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, which 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 to support and move 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 range of geographical 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 sea ​​life Spiral-shaped shells of ammonites can be distinguished.