The Ordovician period (system) is the second layer of sediments of the Paleozoic group in the history of the geology of our planet. The name comes from the ancient Ordovician tribe. They lived in Wales, Britain. This period was recognized as an independent system. It existed five hundred million years ago and lasted sixty million years. The period is distinguished on most of the modern islands and on all continents.
Geology of the Ordovician system
At the beginning of the period, North and South America were close to Europe and Africa. Australia was next to Africa and was part of Asia. One of the poles was in northern Africa, the other in the northern Pacific. At the very beginning of Ordovician, most of the south of the Earth was occupied by the mainland of Gondwana. It included present South America, the south of the Atlantic Ocean, Australia, Africa, the north of Asia and the Indian Ocean. Gradually, Europe and North America (Lawrence) began to move away from each other. Sea level was rising. Most of the land was in warm latitudes. Mountain and later continental glaciers appeared in Gondwana. In South America and in northwestern Africa, sediments of bottom moraines have survived, which the Paleozoic era left behind .
The Ordovician period on the Arabian Peninsula, in the south of France, Spain is characterized by icing. Traces of ice are also found in Brazil and not in the western Sahara. The expansion of the sea occurred in the middle of the Ordovician period. In the western part of North and South America, Britain, in the Ural-Mongolian belt, in southeast Australia, traces of Ordovician deposits reach up to ten thousand meters. In these places there were many volcanoes, accumulated strata of lavas. Siliceous rocks are also found: jasper, phthanides. In Russia, the Ordovician period is clearly visible on the East European, Siberian platforms, the Urals, Novaya Zemlya, the Novosibirsk Islands, Taimyr, Kazakhstan and Central Asia.
Climatic situation in the Ordovician system
In the Ordovician period, the climate was divided into four types: tropical, temperate, subtropical, nival. In the late Ordovician, a cooling occurred. In tropical areas, the temperature dropped by five degrees, in subtropical areas - by fifteen. It became very cold in high latitudes. On average, the Ordovician observed a warmer climate, compared with the previous era. This proves the spread of limestone rocks.
Minerals in the Ordovician system
Among the minerals formed in this period, oil and gas are isolated. Especially many deposits of this period in North America. Deposits of oil shale and phosphorites are also distinguished. These deposits are explained by geological processes in which magma was involved. For example, in Kazakhstan there are deposits of manganese ores, as well as barite.
Seas in the Ordovician period
In the middle Ordovician there is an expansion of sea spaces. The bottom of the seas is getting lower. These changes strongly influenced the accumulation of a large layer of sedimentary rocks, which are represented by black silt. It consists of volcanic ash, debris and sand. On the territory of modern North America and Europe, shallow seas were located.
Plant world of Ordovician and fauna
Algae in the Ordovician period did not change, if we compare them with the previous period. The very first plants appear on earth. They are mainly represented by mosses.
Life in water in this period is quite diverse. That is why it is considered very important in the history of the Earth. The main species of sea creatures formed. The first fish appear. Only they are very small, about five centimeters. Solid creatures began to appear in marine creatures. This was because living organisms began to rise above the bottom sediments and feed above the bottom of the sea. More and more animals are emerging that feed on seawater. Some groups of vertebrates have already evolved, others have just begun to develop. Vertebrate organisms appear at the end of the Ordovician. From echinoderms appeared sea bubbles, sea lilies. Currently, organisms such as sea lilies and starfish also exist.
A flock of jellyfish swims over the sea lilies - this is a beautiful picture from ancient times. Shell owners also begin their life activities. Gastropods and lamellabine are represented by a large number of species. In the Ordovician, the development of four-branchial cephalopods takes place - these are primitive representatives of nautiloids. These organisms still live in the depths of the Indian Ocean. The shells of the ancient representatives of these living creatures were straight, in contrast to the bent shells of modern types of nautilus. These mollusks led a predator's lifestyle.
New animals during this period were graptolites. They multiplied by budding. Graptolites created colonies. Previously, they were referred to as intestinal, now - to the winged invertebrate animals. At this time, graptolites do not live, but their distant relatives exist. One of them lives in the North Sea - this is Rhabdopleura normanni. A group of organisms also appears that helps corals build reefs. They also appeared at this time - they are bryozoans. They exist now, these organisms look like beautiful lace bushes. These were the aromorphoses of the Ordovician period in living organisms.
Inhabitants of the seas
Fragments of jawless fish were discovered in sandstones in Colorado . Other shark-like vertebrate creatures have been recovered. Fossils indicate that the jawless Ordovician are different from today's species.
The first animals that had teeth were conodonts. These creatures are like eels. Their jaws are different from the jaws of living things. Scientists have counted six hundred species of living creatures that lived in the seas in the above period. Cooling has become one of the causes of the extinction of many species. The shallow seas turned into plains, and the animals of these seas perished. The flora of this period comprehended the same result.
The reason for the extinction of animal organisms
There are many versions of the mass extinction of creatures:
- A burst of gamma rays within the solar system.
- The fall of large bodies from space. Their fragments or meteorites are found to this day.
- The result of the formation of mountain systems. Under the influence of wind, rocks erode and fall into the soil. As a result of these processes, little carbon remains, which affects warming.
- The movement of Gondwana to the South Pole led to cooling, and then glaciation, a decrease in water levels in the oceans.
- Saturation of the oceans with metals. The studied plankton of that period contains an elevated level of a wide variety of metals. Water poisoned by metals.
Which of these versions seems reliable, and why the animals of the Ordovician period became extinct, is currently not known for certain.