The Perm is on the geological time scale, the last system ( or period in geochronology ) in the Paleozoic. The Permian began about 298.9 million years ago and ended about 252.2 million years. The Permian follows the Carboniferous and is overlain by the Triassic. At the Permian - Triassic boundary, the largest known mass extinction of Earth's history happened.
History and naming
The name Perm is of the former Russian province of Perm derived (about today's Perm region accordingly) at the foot of the Ural Mountains. The digested here rocks this time served Roderick Murchison in 1841, the basis of his scientific description. The Perm in Germany and Central Europe is mainly represented by the two lithostratigraphic groups of the Rotliegend and Zechstein. According to this dichotomy, this system was in Germany originally named Dyas, who, however, did not prevail internationally. The term Dyas was but lithologically defined in the first place and is therefore now also used for a lithostratigraphic supergroup, comprising the Permian Zechstein and.
Definition and GSSP
The beginning of the Permian (and the Asselian stage and the Cisuralium series) is defined by the first appearance of the conodont species Streptognathodus isolatus. The end of the Permian (and the beginning of the Triassic) is set with the first appearance of the conodont species Hindeodus parvus and the end of the negative carbon anomaly of the Permian. The set by the IUGS type locality ( GSSP = Global Stratotype Section and Point) for the base of the Permian (and the Asselian - level) is located in the valley of Aidaralash, near the city of Aktobe (Russian Aktjubinsk ) in the southern Urals (Kazakhstan).
Subdivision of the Permian
The Perm was formerly divided mostly in Permian ( 299-270 million years ago ) and Permian ( 270-251 million years ago ), which would be called with the current terms as series. Today, the Permian is divided into three series with a total of nine levels.
- System: Perm ( 298.9 to 252.2 mya ) Series: Lopingium (Upper Permian) ( 259.9 to 252.2 mya ) Level: Changhsingium ( 254.2 to 252.2 mya )
- Level: Wuchiapingium ( 259.9 to 254.2 mya )
- Level: Capitanium ( 265.1 to 259.9 mya )
- Level: Wordium ( 268.8 to 265.1 mya )
- Level: Roadium ( 272.3 to 268.8 mya )
- Level: Kungurian ( 279.3 to 272.3 mya )
- Level: Artinskian ( 290.1 to 279.3 mya )
- Level: Sakmarium ( 295.5 to 290.1 mya )
- Level: Asselian ( 298.9 to 295.5 mya )
The collision of Sibiria with the combined carbon already in the United continents Gondwana supercontinent Pangaea and the Laurussia had arisen in the Permian. A mountain-building phase in which the Ural was unfolded, was the result of this collision. In the equatorial region, the Tethys opened like a wedge to the east. An inlet in the western Tethys submitted to the European land mass. In Europe, formed large grave fault systems and epicontinental basins, which were filled with debris from the Variscan mountain now largely eroded and volcanic rocks ( Permian Basin). As early as the Permian, there are the first signs of the beginning of the disintegration of Pangaea.
The Permo-Carboniferous glaciation of the southern continents took in the Lower Permian initially still on. It ended in Asselian or at the latest in Sakmarium. In the cold zones of Gondwana ( about 60 ° to 90 ° S ) spread the Glossopteris flora. During the Permian prevailed in many areas of the world, a relatively dry climate, the richest salt deposits in the earth's history emerged during this period.
In Perm there seem to be several times come to a greenhouse effect. At the end of this period about 95 % of all marine species and 65 % of all land animals became extinct in the biggest mass extinction of Earth's history. The cause is probably a gigantic volcanic eruption in Siberia ( Siberian Trapp ), as a result, the Earth's climate by more than 5 degrees heated. The associated chemical changes in the atmosphere and in the sea water are likely to have caused the mass extinction.
Development of the fauna
Among terrestrial vertebrates, there was a first major radiation of the groups that you previously summed up as " reptiles ". Numerous species-rich groups first appeared during the Permian and already disappeared at the end of this period, such as the Pareiasauridae ( anapside reptiles). The amphibian -like groups that dominated the Carboniferous, were in decline.
The therapsids ( synapside reptiles), formerly known as " mammal -like reptiles ", are from the Ocher complex ( after the archaeological site near the town of Otschor (Russian Очёр ), Perm region ) in Russia and the Xidagou formation known in China, which the reflect the form of diversity in Laurasia. On the southern continent Gondwana they are limited to the Eodicynodon - Assemblage Zone of the Beaufort Group of the South African Karoo. This fauna includes a variety of therapsids, including Dinocephalia that are represented by the carnivorous and herbivorous Anteosauria Tapinocephalia, Anomodontia such as Dicynodontia, Gorgonopsidae and Therocephalia.
In the summer of 2010, scientists found in the Thuringian Forest, the 60 -centimeter-tall skeleton of a 300 million year old dinosaur, which could be a precursor of the dinosaurs appeared about 100 million years later.
Among the unicellular foraminifera provide the large breed fusulinids important key forms. They disappear at the end of the Permian. Among the coelenterates die from the taboo deferred corals. The brachiopods underwent a final major radiation. In Perm, for example, coral -like shapes (compare with the rudists ) and forms with slashed Dorsalklappen ( Oldhaminiden ) were developed, which have entered into a symbiosis with photosynthetic bacteria driving. These specialized groups and some other groups ( Productiden, Davidsoniiden and spiriferids ) died from partially or totally. Among the arthropods trilobites and Eurypteriden died out. A number of insect orders is first detected in the Permian. In the molluscs, the class of beak Schaler disappears ( rostroconchs ). Among the cephalopods the Bactriten and goniatites died out; the ceratites arise. The line of echinoderms ( Echinodermata ) the buds radiator ( Blastoidea ) and the crinoid groups Camerata and Flexibilia died out.
Development of Flora
The change from Palaeophytic to Mesophytic as the change from Paleozoic to Mesozoic has already taken place earlier. The Palaeophytic ended at about 256 Ma in Wuchiapingium. The previously dominant Farnpflanzengruppen were replaced by the dry Nacktsamigen more resistant plants ( gymnosperms ). On the Gondwana continent, the Glossopteris flora, whose representatives were deciduous, cold tolerant gymnosperms with the prevailing order Glossopteridales developed.
The Permian in Central Europe
In Germany there is the traditional division of the Permian Rotliegend and Zechstein in from the striking change that has taken place at the boundary between the two formations. After a long time the mainland, which began in the Carboniferous penetrated about 257.3 million years ago the sea to North and Central Germany, which marks the beginning of the Zechstein. Only southern Germany remained at first mainland. At the base of the marine deposits of economically important copper shale was deposited. This geological brand is one of the most distinctive marker horizons in Germany.