Some periods of the geological history of the Earth, Paleogene, Devonian, Cambrian, for example, are characterized by intense changes on land. So, 570 million - 480 million years ago, suddenly a lot of fossils appeared. 400 million - 320 million years ago mountain formation movements reached their peak. On land, seed plants began to spread, amphibians appeared. It is believed that these are the most active periods of the geological history of the Earth. The Paleogene p-d is distinguished by the complexity of the structure of the cortex. In many ways, it was close to modern.
Features of natural conditions
On the whole, a relatively high temperature remained during the formation of the crust structure on the planet. This is evidenced by the prevalence of desert conditions, the distribution of reptiles, the evolution of insects (Paleogene, Permian). The Triassic period marked the emergence of primitive mammals, the first dinosaurs. On land, conifers dominated the plants. In the Paleogene period, the climate was mild. In the equatorial part, the temperature could reach 28 degrees, and in the area near the North Sea - 22-26.
Zoning
There were five belts throughout the Paleogene:
- 2 subtropical.
- Equatorial.
- 2 tropical.
High temperatures promoted active weathering. Relics of laterite and kaolinite crusts and products of their redeposition are known on the Brazilian shield, in California, India, Africa, and on the islands of the Indo-Malayan archipelago. In the equatorial part, humid evergreen forests began to develop. They had some similarities with the massifs existing today in Equatorial Africa and the Amazon. Wet tropics were characteristic of the territories of Western Europe, the USA, southern and central regions in Eastern Europe, western parts of China and Asia. Evergreen moisture-loving forests are common in the southern zone. Ferriallite and laterite weathering occurred here. The southern tropics covered the central parts of Australia, some areas of the South. America and South Africa.
Subtropics
They were distributed in the northern United States and the East European Platform, southern Canada, Japan, and the Far East. Along with evergreen vegetation, broadleaf plantings were common in these territories. In the Southern Hemisphere, subtropics were common in southern Chile and Argentina, in New Zealand and South. Australia The average surface water temperature in the epicontinental seas of the belt was no more than 18 degrees. Probably, conditions close to moderate prevailed in the territories of the far north of the North American continent, in Kamchatka and in Eastern Siberia. During the Eocene, the sizes of the tropical and equatorial belts will expand significantly, the conditions of the subtropics will shift far to the polar regions.
The characteristic of the Paleogene period
It began 65 million, and ended 23.5 million years ago. As a separate unit, the Paleogene period was identified by Naumann in 1866. Until that time, it was included in the tertiary system. In the structure of the crust, along with ancient platforms, young ones were also present. The latter spread over quite extensive areas in the geosynclinal fold belts. Their area, in comparison with the beginning of the Mesozoic, has significantly decreased in the Pacific region. Here, by the beginning of the Cenozoic era, extensive folded mountainous areas appeared. In the northern hemisphere were North America and Eurasia. These two platform arrays consisted of ancient and young formations. They were separated by the depression of the Atlantic Ocean, but in the area of the Bering Sea that exists today, they connected. In the southern part, the mainland of Gondwana no longer existed. Antarctica and Australia were separate continents. South America and Africa remained connected until the mid-Eocene.
Flora
The Paleogene period of the Cenozoic era was distinguished by the widespread dominance of angiosperms and conifers (gymnosperms). The latter were distributed exclusively in high latitudes. Forests prevailed in the equatorial part, in which mainly ficus, palm trees and various representatives of sandalwood grew. In the depths of the continents, light forests and savannas prevailed. Middle latitudes were the place of distribution of moisture-loving tropical plantations and plants of temperate latitudes. There were tree-like ferns, sandalwood, breadfruit and banana trees. In the region of high latitudes, the species composition radically changed. Here, in the Paleogene period, araucaria, thuja, cypress, oak, laurel, chestnut, sequoia, and myrtle grew. All of them were typical representatives of the subtropical flora. Vegetation in the Paleogene period was beyond the Arctic Circle. In America, Northern Europe and the Arctic, coniferous-deciduous deciduous forests predominated. However, subtropical plants mentioned above also grew in these territories. Their development and growth was not much affected by the polar night.
Fauna sushi
Animals in the Paleogene period radically differed from those that were before. Instead of dinosaurs, small primitive mammals appeared. They inhabited mainly the forest zone and swamps. The number of amphibians and reptiles decreased significantly. Proboscis , pig-like and tapir-like, indicoterium (resembling rhinos) began to spread. Most of them were adapted to spend most of their time in water. In the Paleogene period, the planet also began to inhabit the ancestors of horses, rodents of various species. A little later, creodonts (predators) appeared. The tops of the trees began to be occupied by toothless birds. Savannahs inhabited by predatory diatrims. These were birds that could not fly. Insects were presented in a wide variety of forms. At the beginning of the Paleogene, lemurs began to appear - representatives of the most primitive group of primates - semi-monkeys. Also, large marsupials began to inhabit land. Among them are known both herbivorous and predatory representatives.
Marine representatives
In the Paleogene period, bivalves and cephalopods bloomed. Unlike the previous species, they inhabited not only salty waters, but also brackish-water and freshwater pools. Some of the gastropods settled in the lowlands. Among other invertebrates, irregular sea urchins, sponges, bryozoans, corals, and arthropods have become especially common. Decopod crustaceans were represented in smaller numbers. These include, in particular, shrimp and crayfish. The role of brachoipods and bryozoans significantly decreased in comparison with earlier periods. As a result of recent studies, it was found that representatives of nanoplankton - microscopic coccolithophids, were of particular importance among organisms at that time. The heyday of these golden algae falls on the Eocene. Together with them, siliceous and diatom flagellates were of rock-forming importance. The sea was also inhabited by vertebrates. Among them, bony fish were the most widespread. Also present at sea were representatives of cartilage - stingrays and sharks. The ancestors of whales, sirens, dolphins began to appear.
East European platform
During the Paleogene, as well as the Neogene, formations were located in continental conditions. The exception was their marginal parts. They experienced slight bending and began to become covered by shallow seas. The development of the East European Platform in the Cenozoic is associated with changes in the Mediterranean belt. First, mainly lowerings, and then - large ups. In the Paleogene, the southern part of the platform, which adjoins the Mediterranean belt, caved in. In shallow seas carbonate-clay and sand sediments began to accumulate. By the end of the Paleogene, the basin began to decrease rapidly, and in the next period, the Neogene, a continental regime formed.
Siberian platform
She was in slightly different conditions than the East European. During the Cenozoic era, the Siberian platform was represented as a rather high elevated erosion area. The mountain system of the north-east direction began to form. The height of the chains increased in the direction of the uplift, which is called the Baikal arch. By the end of the era, a mountainous relief appeared, with individual peaks reaching 3 thousand meters. In the axial part, a system of long and narrow depressions was formed. They stretched to a distance of more than 1.7 thousand km from the Mongolian border to the middle reaches of the river. Olekma. The largest is the basin of Lake. Baikal - the maximum depth is 1620 m.