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 the northern part of Africa, the other in the northern part of the Pacific Ocean. At the very beginning of the Ordovician, most of the south of the Earth was occupied by the mainland Gondwana. It included what is now South America, the south Atlantic Ocean, Australia, Africa, northern Asia, and the Indian Ocean. Gradually, Europe and North America (Laurentia) began to move away from each other. The sea level was rising. Largest piece of landwas in warm latitudes. Mountain and later continental glaciers appeared in Gondwana. In South America and in the northwestern part of Africa, sediments of bottom moraines, which were left behind by the Paleozoic era, have been preserved.
The Ordovician period in the Arabian Peninsula, in the south of France, Spain is characterized by icing. Traces of ice have also been found in Brazil and non-western Sahara. The expansion of maritime spaces took place in the middle of the Ordovician period. In the western part of North and South America, Britain, in the Ural-Mongolian belt, in the southeast of Australia, traces of Ordovician deposits reach up to ten thousand meters. There were many volcanoes in these places, lava strata were accumulated. Siliceous rocks are also found: jasper, ftanides. On the territory of Russia, the Ordovician period is clearly visible on the East European, Siberian platforms, in the Urals, on Novaya Zemlya, on the New Siberian Islands, on Taimyr, in 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. Cooling occurred in the late Ordovician. In tropical regions, the temperature dropped by five degrees, in subtropical regions - by fifteen. It got very cold in high latitudes. The Middle Ordovician experienced a warmer climate than the previous era. This proves the distribution of limestone rocks.
Ordovician Minerals
Among the fossils formed in this period are oil and gas. There are especially many deposits of this period in North America. Oil shale and phosphorite deposits 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 barites.
Ordovician seas
In the Middle Ordovician there is an expansion of marine spaces. The bottom of the seas is getting lower. These changes greatly influenced the accumulation of a large layer of sedimentary rocks, which are represented by black silt. It consists of volcanic ash, clastic rocks and sand. Shallow seas were located on the territory of modern North America and Europe.
Ordovician flora and fauna
Algae in the Ordovician period did not change when compared to the previous period. The very first plants appear on earth. They are mainly represented by mosses.
Life in the water in this period is quite diverse. That is why it is considered very important in the history of the Earth. The main types of sea creatures have formed. The first fish appear. Only they are very small, about five centimeters. Sea creatures began to develop hard covers. This happened because living organisms began to rise above the sediments of the bottom and feed above the bottom of the sea. There are more and more animals that feed in sea water. Some groups of vertebrates have already evolved, others have just begun to develop. At the end of the Ordovician, vertebrate organisms appear. Sea bladders, sea lilies appeared from echinoderms. Currently, organisms such as sea lilies and starfish also exist.
A flock of jellyfish swims over sea lilies - this is a beautiful picture from ancient times. The owners of the shells also begin their livelihoods. Gastropods and laminabranchs are represented by a large number of species. In the Ordovician, the development of four-gill 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 curved shells of modern nautilus species. These mollusks led a predatory lifestyle.
New animals in this period were graptolites. They reproduced by budding. Graptolites created colonies. Previously, they were classified as coelenterates, now they are classified as wing-gill invertebrates. At present, 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 is also emerging that helps corals build reefs. They also appeared at this time - these are bryozoans. They exist even now, these organisms look like beautiful lacy bushes. These are the aromorphoses of the Ordovician period in living organisms.
Inhabitants of the seas
Fragments of jawless fish have been found in sandstones in Colorado. Other remains of vertebrate creatures similar to sharks have also been recovered. Fossil evidence suggests that jawlessOrdovician are different from today's species.
The first animals to have teeth are conodonts. These creatures are like eels. Their jaws are different from the jaws of living beings. Scientists have counted six hundred species of living beings that lived in the seas during the period described above. Cooling has become one of the reasons for the extinction of many species. The shallow seas turned into plains, and the animals of these seas perished. The same result befell the plant world of this period.
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 are weathered and fall into the soil. These processes leave little carbon to contribute to warming.
- The movement of Gondwana to the South Pole led to a cooling, and then glaciation, a decrease in the water level in the oceans.
- Saturation of the oceans with metals. The studied plankton of that period contains an increased level of various metals. Water poisoning with metals has occurred.
Which of these versions seems to be reliable, and why the animals of the Ordovician period became extinct, is currently not known for certain.
