Pannotia

from Wikipedia, the free encyclopedia
Artist's impression of the earth 600 mya with the supercontinent Pannotia
Plate tectonic situation 550 mya. In this reconstruction it is assumed that Pannotia never existed as a real supercontinent: Laurentia (wine-red), Sibiria (pink) and Baltica (green) already broke away from “West-Gondwana” (yellow) before Australo-Antarctica (gray-blue ) is docked.

Pannotia , also Vendia or Greater Gondwana , is a hypothetical late neoproterozoic supercontinent . It possibly existed briefly from 600 to 540 mya due to the collision of some continental blocks with a very large land mass, while other continental blocks were already being detached from this land mass.

200 million years after the collapse of Rodinia , the three fragments united

again to a supercontinent. The world climate was, like today, in a so-called ice house phase . From today's perspective, however, the distribution of the land masses over the two hemispheres was “upside down”. Australia , parts of Africa , Antarctica , today's Arabian Peninsula and India were located in the tropics and were therefore free of ice or covered by a shelf sea . The two large Chinese cratons reached into the northern temperate latitudes and were partially glaciated. The rest of the land mass was in the temperate and polar latitudes of the southern hemisphere and was covered by an extensive ice sheet or ice shelf .

At the end of its relatively short existence, Pannotia split into four continents:

Around 300 mya - another 250 million years later - the last supercontinent to date, Pangea, was formed .

Pannotia is forming

The supercontinent Rodinia began to break apart between 750 and 720 mya. From 630 to 550 mya the remaining continents and crust fragments dissolved, so that Laurentia had also isolated. During this period, however, the fragments began to form anew to form the last, neoproterozoic supercontinent Pannotia, also known as Greater Gondwana or Gondwanaland.

The formation of Pannotia was shaped by the Pan-African Orogeny , which occurred on most of the land masses in the Gondwana area. After the preceding neoproterozoic decay and collision processes from around 780 mya onwards, a large number of mountain ranges emerged when the oceans began to close around the continents and cratons.

Already during the Rodinia formation, from 750 mya, the East African orogeny began with the accretion of terrans to the Arab-Nubian shield and the unfolding of the Mozambique belt, including the formation of Madagascar as a result of continental collisions on the east coast of Africa. These processes lasted up to about 550 mya.

A second phase followed between around 600 and 530 mya. It was dominated by the collision of Greater India ( India with NE Madagascar , Sri Lanka and the Seychelles ), Australia with East Antarctica and the cratons Congo-São Francisco and Kalahari. The Kuunga Belt was created. This belt contains several African orrogens between the Congo-São Francisco and Kalahari cratons, which connect to the Mozambique Belt to the south and run in a westerly direction to the western end of the Congo-São Francisco craton. In East Antarctica , mountain ranges had formed in Queen Maud Land along the west coast. The Brasiliano orogeny took place on the east coast of South America. B. the Dom Feliciano and Ribeira mountain ranges were created, these resulted from the collision between the western sides of the African cratons Congo-São Francisco and Kalahari and the eastern areas of the South American cratons Amazonia and Rio de la Plata. Orogens also arose in Greater India and Sri Lanka.

Between 650 and 630 mya, the Congo-São Francisco cratons collided with the Sahara Metacraton, West Africa with the Amazonia (Amazon shield). The Arab-Nubian shield was approaching the Sahara metacraton. The Mozambique Ocean between the east coast of Africa , Australia with East Antarctica and Greater India began to close. Amazonia was still connected to the south-west side of Laurentia and Baltica . The cratons Kalahari and Rio de la Plata were still docked on the north-west side of Laurentia. These land masses were located in southern subtropical to low latitudes. Sibiria (also Angaraland ) and the craton of North China had broken away from Laurentia and were grouped along the equator. South China, Australia with East Antarctica, Greater India and the Tarim Block were unconnected in tropical to northern subtropical latitudes.

Around 600 mya, the Congo-São Francisco cratons collided with the Rio de la Plata, which is still connected to Laurentia. A rift began to form between Laurentia and Amazonia, which caused complete separation from around 570 mya. Baltica had already broken away from Laurentia. This configuration was now in mid to low southern latitudes. Greater India, Australia with East Antarctica, the Tarim Block as well as Kalahari, Siberia and North China were individually in northern equatorial latitudes.

Around 550 mya the Arab-Nubian shield had united with the Sahara metacraton, which closed the Mozambique Ocean in this area. The Kalahari craton was approaching the Congo-São Francisco and Rio de la Plata cratons. This closed the Adamastor Ocean. West Gondwana had formed completely and had drifted further south, so that Amazonia now touched the South Pole. Baltica drifted to mid-southern latitudes and lay next to Siberia and Laurentia. Greater India had drifted towards Australia with East Antarctica and the Tarim Block. Like the cratons of northern and southern China, these were located in northern tropical to subtropical latitudes.

Between 540 and 530 mya, Australia collided with East Antarctica and Greater India with the Tarim Block, collectively referred to as East Gondwana, with the previously formed West Gondwana. This gave rise to the great continent of Gondwana .

West Gondwana was in mid to low southern latitudes, while East Gondwana was grouped around the equator. Laurentia, Siberia and Baltica were unrelated to the mid-southern latitudes. The cratons of northern and southern China had migrated to northern tropical to subtropical zones near Australia. Together with Gondwana, this continental configuration is called Pannotia, also known as Greater Gondwana or Gondwanaland.

Pannotia disintegrates

The accretions of the continental masses to Pannotia were briefly and from around 540 to 530 mya already marked in places by drifting apart again, with Laurentia, Siberia and Baltica moving further away from Gondwana.

Pannotia was surrounded by the global Panthalassa Ocean.

climate

The orogenes on the continents and cratons had a clear influence on the flow conditions in the atmosphere and the oceans . In particular, the East African Belt with the adjacent Antarctic mountain ranges (Transgondwanan Supermountain) formed an approximately 8000 km long and high barrier for the prevailing global west wind zone , comparable to today's Andes and Rocky Mountains . In cryogenian prevailed between about 660 and 635 worldwide ice age , the Marinoan glaciation . It was for the second time within the Proterozoic the Snowball Earth formed. Glacial sediments, such as B. Boulder clay , dropstones , varves and diamictites as well as rock scratches and paleomagnetic reconstructions clearly indicate glaciation up to the equator.

Evolutionary fauna development

The massive geological and climatic changes created diverse and seriously changed environmental conditions. The mountains provided large amounts of sediment, which significantly expanded the ocean shelves and thus potential new habitats. The sediment load also provided a very rich source of nutrients for living things in the seas. It also increased the oxygen in the atmosphere.

In particular, the end of the Maron Ice Age triggered the beginning of the faunal evolutionary processes, as the weathering of rocks increased significantly and thus set physical and chemical processes in the atmosphere and the seas in motion. Temperatures rose globally.

Between 580 and 540 mya, in shallow, warm seas near the coast, but also in deeper, cold zones of the deep sea, a peculiar community, the Ediacara fauna , developed. The evolutionary development of the fauna began. These creatures of the Ediacara fauna do not resemble later animals at all or only slightly. The Ediacara faunas were mainly single-celled , but the first multicellular cells have also been identified. No higher animals are known, but eukaryotes (living things with cell nuclei) were well developed from the start.

With the end of the Proterozoic at the turn of the Cambrian , the many tribes of the animal kingdom seemed to have already existed as the starting point for the Cambrian explosion that followed.

Web links, sources

Commons : Pannotia  - collection of images, videos and audio files

English:

Individual evidence

  1. ↑ Assembly, configuration, and break-up history of Rodinia: A synthesis ScienceDirekt Precambrian Research 160 (2008) 179-210
  2. ^ Pan-African Orogeny Encyclopedia 0f Geology (2004), vol. 1, Elsevier
  3. ↑ Orogen styles in the East African Orogen Science Direct Journal of African Earth Sciences, Vol. 86, October 2013, pp. 65-106
  4. ^ Araban Shield website Saudi Geological Survey
  5. ↑ TECTONIC EVOLUTION OF THE MOZAMBIQUE BELT, EASTERN AFRICA Cutten, HNC, Johnson, SP, & De Waele, B.
  6. ↑ THE PROTEROZOIC HISTORY OF THE PROTO-CONGO CRATON OF CENTRAL AFRICA Department of Earth Sciences, Royal Museum for Central Africa, B-3080 Tervuren, Belgium
  7. ^ Archean Accretion and Crustal Evolution of the Kalahari Craton Journal of Petrologie April 8, 2009
  8. ^ East African and Kuunga Orogenies in Tanzania - South Kenya; bibcode : 2012EGUGA..14.8754F .
  9. ↑ The Brasiliano collage in South America: a review Brazilian Journal of Geology, Braz. J. Geol. Vol. 44 no.3 São Paulo July / Sept. 2014
  10. ^ A connection between the Neoproterozoic Dom Feliciano (Brazil / Uruguay) and Gariep (Namibia / South Africa orogenic belts) Precambrian Research, Vol. 139, No. 3-4, September 9, 2005, pp. 195-221
  11. ↑ The Damara Ribeira orogen of the Pan-African / Brasiliano cycle in Namibia (South West Africa) and Brazil ReseachGate Geological and Paleontological Institute of the University of Goettingen, Goettingen, Federal Republic of Germany, Tectonophysics (Impact Factor: 2.87). 08/1979; doi : 10.1016 / 0040-1951 (79) 90150-1
  12. ↑ The Río de la Plata Craton website Springer Link
  13. ↑ The Saharan Metacraton Science Direct Journal of African Earth Sciences 34 (2002) 119-136
  14. ^ Structure, evolution and palaeogeography of the West African craton and bordering belts during the Neoproterozoic ScienceDirect Precambrian Research Vol. 69, No. 1-4, October 1994, pp. 307-326
  15. ^ The position of the Amazonian Craton in supercontinents Gondwana Research Vol. 15, No. 3-4, June 2009, pp. 396-407
  16. ^ Archean Accretion and Crustal Evolution of the Kalahari Craton Journal of Petrologie April 8, 2009
  17. ↑ The Río de la Plata Craton website Springer Link
  18. ↑ North China Kraton website Université Paris Sud
  19. ↑ The India and South China cratons at the margin of Rodinia SienceDirekt Lithos Vol. 123, No. 1-4, April 2011, pp. 176-187
  20. ^ Archean crustal evolution of the northern Tarim craton, NW China ScienceDirekt Precambrian Research
  21. ^ Tectonic framework and evolution of the Tarim Block in NW China ScienceDirekt Precambrian Research
  22. ↑ Late Vendian Closure of the Adamastor Ocean Gondwana Research (Impact Factor: 8.24). 07/2004; 7 (3): 685-699. doi : 10.1016 / S1342-937X (05) 71056-X
  23. ↑ Did the Transgondwanan Supermountain trigger the explosive radiation of animals on Earth? ScienceDirect Earth and Planetary Science Letters, Vol. 250, Nos. 1-2, October 15, 2006, pp. 116-133
  24. ^ The Neoproterozoic assembly of Gondwana and its relationship to the Ediacaran – Cambrian radiation ScienceDirect Gondwana Research 14 (2008) 5-21