Jurassic period. Key Features

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

For the first time deposits of the Jurassic period were 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 variety of conditions.

190-145 million years ago in Jurassic period the single supercontinent Pangea began to disintegrate 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).

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

cycads- a class of gymnosperms that prevailed in the green cover of the Earth. Now they are found here and there in the tropics and subtropics. Dinosaurs roamed under the canopy of these trees. Outwardly, 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. Ginkgoes are deciduous (unusually for gymnosperms) trees with an oak-like crown and small, fan-shaped leaves. Only one species has survived to this day - ginkgo biloba. Very diverse were conifers, 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 a lot. Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve molluscs fill all the vital niches of the seabed. Many stop collecting food from the ground and move on to pumping water with the help of gills. A new type of reef communities is emerging, approximately the same as it exists now. It is based on six-ray corals that appeared in the Triassic.

land animals

One of the fossil creatures of the Jurassic period, combining the features of birds and reptiles, is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates 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 rather poorly (planned from tree to tree), and was about 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, they were preserved only in hoatzin chicks).

In the Jurassic period, small, woolly warm-blooded animals - mammals - live 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, 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 a chicken, or they could reach the size of huge whales. Some of them moved on four limbs, while others ran on their hind legs. Among them were clever hunters and bloodthirsty predators, but there were also harmless herbivorous animals. The most important feature common to all their species is that they were land animals.

For the first time, deposits of this period were found in the Jura (mountains in Switzerland and France), hence the name of the period. The Jurassic period is subdivided into three divisions: leyas, doger and malm.

The deposits of the Jurassic period are quite diverse: limestones, clastic rocks, shales, igneous rocks, clays, sands, conglomerates formed in a variety of conditions.

Sedimentary rocks containing many representatives of fauna and flora are widely distributed.

Intensive tectonic movements at the end of the Triassic and at the beginning of the Jurassic contributed to the deepening of the large bays that gradually separated Africa and Australia from Gondwana. The gulf between Africa and America deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia.

Intense volcanism and mountain-building processes led to the formation of the Verkhoyansk fold system. The formation of the Andes and the Cordillera continued. Warm sea currents have reached the Arctic latitudes. The climate became warm and humid. This is evidenced by the significant distribution of coral limestones and the remains of thermophilic fauna and flora. There are very few deposits of a dry climate: lagoonal gypsum, anhydrites, salts and red sandstones. The cold season already existed, but it was characterized only by a decrease in temperature. There was no snow or ice.

The climate of the Jurassic period depended on more than just sunlight. Numerous volcanoes and outpourings of magma on the bottom of the oceans heated up the water and the atmosphere, saturating the air with the steam of water, which then fell as rain on land, flowing in stormy streams into lakes and oceans. Numerous freshwater deposits testify to this: white sandstones alternating with dark loams.

Warm and humid climate favored the flourishing flora. Ferns, cicadas, and conifers formed extensive marshy forests. Araucaria, arborvitae, cicadas grew on the coast. Ferns and horsetails formed the undergrowth. In the Lower Jurassic, the vegetation throughout the northern hemisphere was fairly uniform. But already starting from the Middle Jurassic, two plant belts can be identified: the northern one, dominated by ginkgo and herbaceous ferns, and the southern one, with bennetites, cicadas, araucaria, and tree ferns.

The characteristic ferns of the mountain period were matonii, which have survived to this day in the Malay

archipelago. Horsetails and club mosses almost did not differ from modern ones. The place of extinct seed ferns and cordaites is occupied by cycads, which still grow in tropical forests.

Ginkgoaceae were also widely distributed. Their leaves turned to the sun with an edge and resembled huge fans. From North America and New Zealand to Asia and Europe, dense forests of coniferous plants grew - araucaria and bennetites. The first cypress and, possibly, spruce trees appear.

The representatives of the Jurassic conifers also include sequoia - a modern giant California pine. Currently, sequoias remain only on the Pacific coast of North America. Separate forms have been preserved. even more ancient plants, such as glassopteris. But there are few such plants, since they were supplanted by more perfect ones.

The lush vegetation of the Jurassic period contributed to the widespread distribution of reptiles. Dinosaurs have greatly evolved. Among them are lizard and ornithischian. Lizards moved on four legs, had five toes on their feet, and ate plants. Most of them had long neck, small head and long tail. They had two brains: one small, in the head; the second is much larger in size - at the base of the tail.

The largest of the Jurassic dinosaurs was the brachiosaurus, reaching a length of 26 m, weighing about 50 tons. It had columnar legs, a small head, and a thick long neck. Brachiosaurs lived on the shores of the Jurassic lakes, 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 moved on four legs, the hind legs were longer than the front ones. Diplodocus spent most of its life in swamps and lakes, where it grazed and escaped from predators.

Brontosaurus was comparatively tall, had a large hump on its back and a thick tail. Its length was 18 m. The vertebrae of the brontosaurus were hollow. Chisel-shaped small teeth were densely located on the jaws of a small head. The brontosaurus lived in swamps, on the shores of lakes.

Jurassic geological period, Jura, Jurassic system, middle period of the Mesozoic. Began 200-199 million years ago. n. and ended with 144 million liters. n.

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

Jurassic tectonics: At the beginning of the Jurassic, the single supercontinent Pangea began to break up into separate continental blocks. Shallow seas formed between them. Intensive tectonic movements at the end of the Triassic and at the beginning of the Jurassic contributed to the deepening of the large bays that gradually separated Africa and Australia from Gondwana. The gulf between Africa and America deepened. Depressions formed in Eurasia: German, Anglo-Paris, West Siberian. The Arctic Sea flooded the northern coast of Laurasia. It is thanks to this that the climate of the Jurassic period became more humid. In the Jurassic, the outlines of the continents begin to form: Africa, Australia, Antarctica, North and south america. And although they are located differently than now, they formed precisely in the Jurassic period.

Climate and vegetation of the Jurassic period

The volcanic activity of the end of the Triassic - the beginning of the Jurassic period caused the transgression of the sea. The continents separated and the climate in the Jurassic became more humid than in the Triassic. In place of the deserts of the Triassic period, lush vegetation grew in the Jurassic period. Huge areas were covered with lush vegetation. The forests of the Jurassic period mainly consisted of ferns and gymnosperms.

The warm and humid climate of the Jurassic period contributed to the violent development of the plant world of the planet.

Ferns, conifers, and cycads formed extensive marshy forests. Araucaria, arborvitae, cicadas grew on the coast. Ferns and horsetails formed extensive woodlands. At the beginning of the Jurassic, about 195 million years. n. throughout the northern hemisphere, the vegetation was rather monotonous. Ginkgo and herbaceous ferns predominated in the northern vegetation belt. In the Jurassic period, Ginkgoaceae were very widespread. Groves of ginkgo trees grew throughout the belt.

In the southern vegetation belt, cycads and tree ferns predominated.

Ferns of the Jurassic period have survived to this day in some parts wildlife. Horsetails and club mosses almost did not differ from modern ones.

animals: Jurassic - the dawn of the dinosaur era. It was the violent development of vegetation that contributed to the emergence of many species of herbivorous dinosaurs. The growth in the number of herbivorous dinosaurs gave impetus to the growth in the number of predators. Dinosaurs settled all over the land and lived in forests, lakes, swamps. The range of differences between them is so great that family ties between them are established with great difficulty. The variety of dinosaur species in the Jurassic period was great. They could be the size of a cat or a chicken, or they could reach the size of huge whales.

Jurassic period - the time of habitation of many famous dinosaurs. Of the lizards, these are Allosaurus and Diplodocus. Of the ornithischians, this is a stegosaurus.

In the Jurassic period, winged lizards - pterosaurs reigned supreme in the air. They appeared in the Triassic, but their heyday fell on the Jurassic period. Pterosaurs were represented by two groups of pterodactyls and rhamphorhynchus.

In the Jurassic period, the first birds appear, or something in between birds and lizards. Creatures that appeared in the Jurassic period and have the properties of lizards and modern birds are called Archeopteryx. The first birds are Archeopteryx, the size of a dove. Archeopteryx lived in forests. They fed mainly on insects and seeds.

Bivalves displace brachiopods from shallow waters. Brachiopod shells are replaced by oysters. Bivalve molluscs fill all the vital niches of the seabed. Many stop collecting food from the ground and move on to pumping water with the help of gills. in warm and shallow seas other important events took place during the Jurassic period.

The Jurassic period gave rise to many species of plesiosaurs and ichthyosaurs that rivaled the fast-moving and extremely agile sharks. bony fish. and in sea ​​depths Leopleuradon patrolled its territory non-stop in search of food.

But one creature could rightfully be called the master of the Jurassic seas. This is a giant Liopleurodon weighing up to 25 tons. Liopleurodon was the most dangerous predator seas of the Jurassic period, and possibly throughout the history of the planet.

Era. Continued for 56 million years. It began 201 million years ago and ended 145 million years ago. The geochronological scale of the history of the Earth of all eons, eras and periods is located.

The name "Jura" was named after the mountain range of the same name in Switzerland and France, where deposits of this period were first discovered. Later, geological formations of the Jurassic period were discovered in many other places on the planet.

In the Jurassic period, the Earth almost completely recovered from the largest in history. Various forms life - marine organisms, land plants, insects and many animal species - begin to flourish and increase their species diversity. Dinosaurs reign in the Jurassic period - large, and sometimes just giant lizards. Dinosaurs existed almost everywhere and everywhere - in the seas, rivers and lakes, in swamps, forests, in open spaces. Dinosaurs received such a wide variety and distribution that over millions of years of evolution, some of them began to differ radically from each other. Dinosaurs included both herbivores and carnivores. Some of them were the size of a dog, while others reached a height of more than ten meters.

One of the species of lizards in the Jurassic period became the ancestor of birds. Archeopteryx, which existed just at this time, is considered an intermediate link between reptiles and birds. In addition to lizards and giant dinosaurs, warm-blooded mammals already lived on earth at that time. Mammals of the Jurassic period were mostly small in size and occupied rather insignificant niches in the living space of the earth of those times. Against the background of the prevailing number and diversity of dinosaurs, they were almost invisible. This will continue throughout the Jurassic and all subsequent periods. Mammals will become rightful owners Earth only after the Cretaceous-Paleogene extinction, when all dinosaurs disappeared from the face of the planet, opening the way for warm-blooded animals.

Jurassic period animals

Allosaurus

Apatosaurus

Archeopteryx

Barosaurus

Brachiosaurus

Diplodocus

Dryosaurs

Giraffatitan

Camarasaurus

Camptosaurus

Kentrosaurus

Liopleurodon

Megalosaurus

Pterodactyls

ramphorhynchus

Stegosaurus

Scelidosaurus

Ceratosaurus

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, conglomerates formed in a variety of conditions.

Jurassic subdivision

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

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

Vegetation

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

land animals

One of the fossil creatures that combine the features of birds and reptiles is Archeopteryx, or the first bird. For the first time, his skeleton was discovered in the so-called lithographic slates in Germany. The find was made two years after the publication of Charles Darwin's work " The Origin of Species" and became a strong argument in favor of the theory of evolution - it was initially considered a transitional form from reptiles to birds (in fact, it was a dead-end branch of evolution that was not directly related to real birds) . Archeopteryx flew rather poorly (planned from tree to tree), and was about 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, they were preserved only in hoatzin chicks).

In the Jurassic period, small, woolly warm-blooded animals live on Earth - mammals. They live next to dinosaurs and are almost invisible against their background. In the Jurassic, the division of mammals into monotremes, marsupials, and placentals took place.

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Notes

Literature

• Jordan N. N. development of life on earth. - M .: Enlightenment, 1981.
• Karakash N.I.,. Jurassic system and period // Brockhaus and Efron Encyclopedic Dictionary: in 86 volumes (82 volumes and 4 additional). - St. Petersburg. , 1890-1907.
• Koronovsky N.V., Khain V.E., Yasamanov N.A. Historical Geology: Textbook. - M .: Academy, 2006.
• Ushakov S.A., Yasamanov N.A. Continental drift and climates of the Earth. - M .: Thought, 1984.
• Yasamanov N.A. Ancient climates of the Earth. - L.: Gidrometeoizdat, 1985.
• Yasamanov N.A. Popular paleogeography. - M .: Thought, 1985.

Links

• - A site about the Jurassic period, a big library paleontological books and articles.

An excerpt characterizing the Jurassic period