The Ediacaran is a period of Earth's history before about 600 million years ago. During this time, the origin of the multi-cellular animal life occurred.
When Ediacaran is the youngest stratigraphic system and the recent geochronological period of the Proterozoic. It began about 635 million years ago and ended about 541 million years. It is under and overlaid by Cryogenium from the Cambrian.
History and naming
The term was in May 2004, officially adopted by the International Commission on Stratigraphy (ICS ) and confirmed by the International Union of Geological Sciences. Named the Ediacaran by the known fossils of the Ediacaran fauna of the Ediacara Hills, an area in the Flinders Ranges in South Australia. There, the geologist Reginald Sprigg found 1946 Claude footprints of apparently soft organisms that had survived mainly on the underside of quartzite and sandstone slabs. Older terms such as the term Vendian become invalid with this official name confirmation.
Definition and GSSP
The beginning of the Ediacaran is the basis of Marinoum - "cap carbonate" the Nuccaleena formation directly above the Elatina - diamictite. The upper limit is the base of the Cambrian, with the first appearance of the trace fossil Treptichnus ( Phycodes ) pedum is defined. The reference profile ( GSSP ) for the Ediacaran is the Enorama Creek profile at 31 ° 19 ' 53.2 "S, 138 ° 38' 0.2 " E - 31.331444444444138.63338888889 in the Flinders Ranges in South Australia. However, the absolute dating of the lower limit is still controversial. The maximum age is to be set at 635 million years, the minimum age at 600 million years ago. Here are even more accurate in the future datings expected.
Subdivision of the Ediacaran
The Ediacaran is despite its long period of probably more than 90 million years ago ( still) not divided as the systems or periods of the Phanerozoic in stages. This is mainly due to the rarity of fossils, which are used in the Phanerozoic primarily to further subdivision. Organisms were certainly not rare in the Ediacaran, but had this a few exceptions, no hard parts, and thus an extremely small Fossilisationspotenzial. Further, the rate of evolution of organisms in the Ediacaran seems to have been much lower, so that one knows virtually no biostratigraphically usable index fossils. Some striking events can still be used to a certain subdivision of the system. The occurrence of the first animal fossils, microscopic eggs, embryos and segmented tubes was geochronological dating to 599 ± 4 mya. After the regional spread Gaskiers glaciation, appear in Newfoundland (Canada) in the sediments immediately above the first macroscopic fossils. These are attributed to the Ediacaran fauna; they are thus interpreted as the first appearance of this fauna. These layers have been dated to about 575 million years. Around 555 mya appear the first traces of bilaterians, or Bilateria. Around 550 mya, shortly before the beginning of the Cambrian, the first organisms with mineralized hard parts are already proven. The most representative of the Ediacaran fauna died out at the beginning of the Cambrian.
Following the collapse of Rodinia three major continents ( Laurentia, Baltica and Sibiria ), and the supercontinent Gondwana had formed. Gondwana extends from the south pole to far across the equator into the northern hemisphere. Laurentia and Baltica were in high southern latitudes, Sibiria a little closer to the equator (around the 30 degree of latitude), but also in the southern hemisphere. The northern South America was then in the vicinity of the South Pole, the Panthalassa also covered the North Pole. Between Laurentia and Gondwana had opened before the beginning of the Ediacaran of the Iapetus Ocean, which during the Ediacaran constantly expanded. Between Baltica and Sibiria on one side, which were separated by the Aegir Ocean, Gondwana and on the other side a subduction zone had before Gondwana formed by this part of Gondwana was changed tectonically deformed and thermally ( Cadomian orogeny ). From this part of Gondwana broke in the Paleozoic multiple parts from which were later welded to Laurentia and Baltica and today 's underground parts of Central Europe and the east coast of North America form ( Avalonia and Hun - Super Terran ).
The beginning of the Ediacaran is marked by the end of the great ice ages of the Cryogenium. Accordingly, the climate is characterized at the beginning of the Ediacaran by a very sharp rise in temperatures. Only around 580 Ma is recorded with the Gaskiers - icing a regional glaciation and thus a drop in temperatures.
Development of the fauna
In the Ediacaran probably the first fabric animals ( Eumetazoa ) emerged. However, they were initially have no inner or outer mineralized skeletal parts. Their fossils are therefore very rare and only found in a few areas of the world. These are the first visible to the naked eye fossils. With the findings of the first Ediacaran fossils ( Vendobionten ) from around 575 mya into perspective, the notion of " Cambrian explosion " of life. We therefore speak better today from the Cambrian Radiation.
This development of the tissue animals took place after previously several global glaciations probably had dominated the climate on Earth ( Snowball Earth ). The Marinoische Ice Age was the last of the great ice ages and the base of the post-glacial "cap carbonates " and the beginning of the Ediacaran is defined. The "cap carbonates " are now seen as evidence of the strong warming after the end of the Ice Age or the very rapid melting of the ice and sea level rise. Occur immediately above the last tillites in the Doushantuo phosphorites of the lineup ( Prov. Guizhou, southern China ) the first animal fossils on: microscopic eggs, embryos and segmented tubes and first representative of Bilateralia as Vernanimalcula. They were geochronological dated to 599 ± 4 mya. The oldest macroscopically visible fossils were discovered in the dock lineup of Newfoundland in 2003. Charnia wardi is the oldest fossil of the Ediacaran fauna. These layers have been dated to about 575 million years. Kimberella, one of the oldest bilaterian fossils, was found on the White Sea coast in sediments of the Ust- Pinega Formation, which have been dated at about 555 Ma. In the same sediments also the first tracks and buildings were found. Around 550 Ma, shortly before the beginning of the Cambrian Period, the first organisms are already calcified hard parts demonstrated ( Cloudina, Namacalathus ). Of these layers, the oldest spicules of sponges have been described. At the end of the Ediacaran disappeared most Ediacaran forms, only about a handful crossed the Ediacaran - Cambrian boundary. The last Ediacaran forms are detected from the Upper Cambrian.
Development of Flora
About the flora of the Ediacaran is virtually nothing is known. The development of higher plants only took place during the Palaeozoic. Therefore, only microscopic plant life in the Ediacaran is to be assumed. Red algae, brown algae yellow and green algae were certainly already exists.
The Ediacaran in Europe
Layers of the Ediacaran are open in Europe in the Central German Uplands (Black Forest, Spessart, Harz, Thuringian Forest, Ore Mountains), in England and Wales, Scandinavia, Eastern Europe, mostly in small-scale areas. However, the typical Ediacaran fossils were only a few localities demonstrated ( eg, Russia, Sweden, England, etc.).