Rodinia

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Proposed reconstruction of Rodinia for 750 Ma, with orogenic belts of 1.1 Ga age highlighted in green. Red dots indicate 1.3-1.5 Ga A-type granites. Rodinia reconstruction.jpg
Proposed reconstruction of Rodinia for 750 Ma, with orogenic belts of 1.1 Ga age highlighted in green. Red dots indicate 1.3–1.5 Ga A-type granites.

Rodinia (from the Russian родить, rodit, meaning "to beget, to give birth", [2] or родина, rodina, meaning "motherland, birthplace") [3] [4] was a Neoproterozoic supercontinent that assembled 1.1–0.9 billion years ago and broke up 750–633 million years ago. [5] Valentine & Moores 1970 were probably the first to recognise a Precambrian supercontinent, which they named 'Pangaea I'. [5] It was renamed 'Rodinia' by McMenamin & McMenamin 1990 who also were the first to produce a reconstruction and propose a temporal framework for the supercontinent. [6]

Contents

Rodinia formed at c. 1.23 Ga by accretion and collision of fragments produced by breakup of an older supercontinent, Columbia, assembled by global-scale 2.0–1.8 Ga collisional events. [7]

Rodinia broke up in the Neoproterozoic with its continental fragments reassembled to form Pannotia 633–573 million years ago. In contrast with Pannotia, little is known yet about the exact configuration and geodynamic history of Rodinia. Paleomagnetic evidence provides some clues to the paleolatitude of individual pieces of the Earth's crust, but not to their longitude, which geologists have pieced together by comparing similar geologic features, often now widely dispersed.

The extreme cooling of the global climate around 717–635 million years ago (the so-called Snowball Earth of the Cryogenian period) and the rapid evolution of primitive life during the subsequent Ediacaran and Cambrian periods are thought to have been triggered by the breaking up of Rodinia or to a slowing down of tectonic processes. [8]

Geodynamics

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Paleogeographic reconstructions

Rodinia at 900 Ma. "Consensus" reconstruction of Li et al. 2008. Rodinia 900Ma.jpg
Rodinia at 900 Ma. "Consensus" reconstruction of Li et al. 2008.

The idea that a supercontinent existed in the early Neoproterozoic arose in the 1970s, when geologists determined that orogens of this age exist on virtually all cratons. [9] [ failed verification ] Examples are the Grenville orogeny in North America and the Dalslandian orogeny in Europe.

Since then, many alternative reconstructions have been proposed for the configuration of the cratons in this supercontinent. Most of these reconstructions are based on the correlation of the orogens on different cratons. [10] Though the configuration of the core cratons in Rodinia is now reasonably well known, recent reconstructions still differ in many details. Geologists try to decrease the uncertainties by collecting geological and paleomagnetical data.

Most reconstructions show Rodinia's core formed by the North American craton (the later paleocontinent of Laurentia), surrounded in the southeast with the East European craton (the later paleocontinent of Baltica), the Amazonian craton ("Amazonia") and the West African craton; in the south with the Río de la Plata and São Francisco cratons; in the southwest with the Congo and Kalahari cratons; and in the northeast with Australia, India and eastern Antarctica. The positions of Siberia and North and South China north of the North American craton differ strongly depending on the reconstruction: [11] [12]

  • SWEAT-Configuration (Southwest US-East Antarctica craton): Antarctica is on the Southwest of Laurentia and Australia is at the North of Antarctica. [13]
  • AUSWUS-Configuration (Australia-western US): Australia is at the West of Laurentia.
  • AUSMEX-Configuration (Australia-Mexico): Australia is at the location of current day Mexico relative to Laurentia.
  • The "Missing-link" model by Li et al. 2008 which has South China between Australia and the west coast of Laurentia. [14] A revised "Missing-link" model is proposed in which Tarim Block serves as an extended or alternative missing-link between Australia and Laurentia. [15]
  • Siberia attached to the western US (via the Belt Supergroup), as in Sears & Price 2000. [16]
  • Rodinia of Scotese. [17]

Little is known about the paleogeography before the formation of Rodinia. Paleomagnetic and geologic data are only definite enough to form reconstructions from the breakup of Rodinia [16] onwards. Rodinia is considered to have formed between 1.3 and 1.23 billion years ago and broke up again before 750 million years ago. [18] Rodinia was surrounded by the superocean geologists call Mirovia (from Russian мировой, mirovoy, meaning "global").

According to J.D.A. Piper, Rodinia is one of two models for the configuration and history of the continental crust in the latter part of Precambrian times. The other is Paleopangea, Piper's own concept. [19] Piper proposes an alternative hypothesis for this era and the previous ones. This idea rejects that Rodinia ever existed as a transient supercontinent subject to progressive break-up in the latter part of Proterozoic times and instead that this time and earlier times were dominated by a single, persistent "Paleopangaea" supercontinent. As evidence, he suggests an observation that the palaeomagnetic poles from the continental crust assigned to this time conform to a single path between 825 and 633 million years ago and latterly to a near-static position between 750 and 633 million years. [8] This latter solution predicts that break-up was confined to the Ediacaran period and produced the dramatic environmental changes that characterised the transition between Precambrian and Phanerozoic times.

Breakup

In 2009 UNESCO's IGCP project 440, named 'Rodinia Assembly and Breakup', concluded that Rodinia broke up in four stages between 825–550 Ma: [20]

  • The breakup was initiated by a superplume around 825–800 Ma whose influence—such as crustal arching, intense bimodal magmatism, and accumulation of thick rift-type sedimentary successions—have been recorded in South Australia, South China, Tarim, Kalahari, India, and the Arabian-Nubian Craton.
  • Rifting progressed in the same cratons 800–750 Ma and spread into Laurentia and perhaps Siberia. India (including Madagascar) and the Congo-Säo Francisco Craton were either detached from Rodinia during this period or simply never were part of the supercontinent.
  • As the central part of Rodinia reached the Equator around 750–700 Ma, a new pulse of magmatism and rifting continued the disassembly in western Kalahari, West Australia, South China, Tarim, and most margins of Laurentia.
  • 650–550 Ma several events coincided: the opening of the Iapetus Ocean; the closure of the Braziliano, Adamastor, and Mozambique oceans; and the Pan-African orogeny. The result was the formation of Gondwana.

The Rodinia hypothesis assumes that rifting did not start everywhere simultaneously. Extensive lava flows and volcanic eruptions of Neoproterozoic age are found on most continents, evidence for large scale rifting about 750 million years ago. [2] As early as 850 and 800 million years ago, [18] a rift developed between the continental masses of present-day Australia, East Antarctica, India and the Congo and Kalahari cratons on one side and later Laurentia, Baltica, Amazonia and the West African and Rio de la Plata cratons on the other. [21] This rift developed into the Adamastor Ocean during the Ediacaran.

Around 550 million years ago, on the boundary between the Ediacaran and Cambrian, the first group of cratons eventually fused again with Amazonia, West Africa and the Rio de la Plata cratons. [22] This tectonic phase is called the Pan-African orogeny. It created a configuration of continents that would remain stable for hundreds of millions of years in the form of the continent Gondwana.

In a separate rifting event about 610 million years ago (halfway into the Ediacaran period), the Iapetus Ocean formed. The eastern part of this ocean formed between Baltica and Laurentia, the western part between Amazonia and Laurentia. Because the exact moments of this separation and the partially contemporaneous Pan-African orogeny are hard to correlate, it might be that all continental mass was again joined in one supercontinent between roughly 600 and 550 million years ago. This hypothetical supercontinent is called Pannotia.

Influence on paleoclimate and life

Unlike later supercontinents, Rodinia would have been entirely barren. Rodinia existed before complex life colonized dry land. Based on sedimentary rock analysis Rodinia's formation happened when the ozone layer was not as extensive as it is today. Ultraviolet light discouraged organisms from inhabiting its interior. Nevertheless, its existence did significantly influence the marine life of its time.

In the Cryogenian period the Earth experienced large glaciations, and temperatures were at least as cool as today. Substantial areas of Rodinia may have been covered by glaciers or the southern polar ice cap.

Low temperatures may have been exaggerated during the early stages of continental rifting. Geothermal heating peaks in crust about to be rifted; and since warmer rocks are less dense, the crustal rocks rise up relative to their surroundings. This rising creates areas of higher altitude, where the air is cooler and ice is less likely to melt with changes in season, and it may explain the evidence of abundant glaciation in the Ediacaran period. [2]

The eventual rifting of the continents created new oceans and seafloor spreading, which produces warmer, less dense oceanic lithosphere. Due to its lower density, hot oceanic lithosphere will not lie as deep as old, cool oceanic lithosphere. In periods with relatively large areas of new lithosphere, the ocean floors come up, causing the eustatic sea level to rise. The result was a greater number of shallower seas.

The increased evaporation from the larger water area of the oceans may have increased rainfall, which, in turn, increased the weathering of exposed rock. By inputting data on the ratio of stable isotopes 18O:16O [ failed verification ] into computer models, it has been shown that, in conjunction with quick weathering of volcanic rock, this increased rainfall may have reduced greenhouse gas levels to below the threshold required to trigger the period of extreme glaciation known as Snowball Earth. [23]

Increased volcanic activity also introduced into the marine environment biologically active nutrients, which may have played an important role in the development of the earliest animals.

See also

Related Research Articles

Proterozoic Third eon of the geologic timescale, last eon of the Precambrian Supereon

The Proterozoic is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life on the Earth. The name Proterozoic combines the two forms of ultimately Greek origin: protero- meaning "former, earlier", and -zoic, a suffix related to zoe "life". The Proterozoic Eon extended from 2500 mya to 541 mya, and is the most recent part of the Precambrian "supereon." The Proterozoic is the longest eon of the Earth's geologic time scale and it is subdivided into three geologic eras : the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.

Laurasia Northern supercontinent that formed part of the Pangaea supercontinent

Laurasia, a portmanteau for Laurentia and Asia, was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around 335 to 175 million years ago (Mya). It separated from Gondwana 215 to 175 Mya during the breakup of Pangaea, drifting farther north after the split and finally broke apart with the opening of the North Atlantic Ocean c. 56 Mya.

Iapetus Ocean ocean that existed in the late Neoproterozoic and early Paleozoic eras

The Iapetus Ocean was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale. The Iapetus Ocean was situated in the southern hemisphere, between the paleocontinents of Laurentia, Baltica and Avalonia. The ocean disappeared with the Acadian, Caledonian and Taconic orogenies, when these three continents joined to form one big landmass called Euramerica. The "southern" Iapetus Ocean has been proposed to have closed with the Famatinian and Taconic orogenies, meaning a collision between Western Gondwana and Laurentia.

Columbia (supercontinent) Ancient supercontinent of approximately 2,500 to 1,500 million years ago

Columbia, also known as Nuna and Hudsonland, was one of Earth's ancient supercontinents. It was first proposed by Rogers & Santosh 2002 and is thought to have existed approximately 2,500 to 1,500 million years ago in the Paleoproterozoic Era. Zhao et al. 2002 proposed that the assembly of the supercontinent Columbia was completed by global-scale collisional events during 2.1–1.8 Ga.

Arctica or Arctida was an ancient continent which formed approximately 2.565 billion years ago in the Neoarchean era. It was made of Archaean cratons, including the Siberian Craton, with its Anabar/Aldan shields in Siberia, and the Slave, Wyoming, Superior, and North Atlantic cratons in North America. Arctica was named by Rogers 1996 because the Arctic Ocean formed by the separation of the North American and Siberian cratons. Russian geologists writing in English call the continent "Arctida" since it was given that name in 1987, alternatively the Hyperborean craton, in reference to the hyperboreans in Greek mythology.

Pannotia Hypothesized Neoproterozoic supercontinent from the end of the Precambrian

Pannotia, also known as the Vendian supercontinent, Greater Gondwana, and the Pan-African supercontinent, was a relatively short-lived Neoproterozoic supercontinent that formed at the end of the Precambrian during the Pan-African orogeny, during the Cryogenian period and broke apart 560 Ma with the opening of the Iapetus Ocean, in the late Ediacaran and early Cambrian. Pannotia formed when Laurentia was located adjacent to the two major South American cratons, Amazonia and Río de la Plata. The opening of the Iapetus Ocean separated Laurentia from Baltica, Amazonia, and Río de la Plata.

Baltica Late-Proterozoic to early-Palaeozoic continent

Baltica is a paleocontinent that formed in the Paleoproterozoic and now constitutes northwestern Eurasia, or Europe north of the Trans-European Suture Zone and west of the Ural Mountains. The thick core of Baltica, the East European Craton, is more than three billion years old and formed part of the Rodinia supercontinent at c.Ga.

Congo Craton Precambrian craton that with four others makes up the modern continent of Africa

The Congo Craton, covered by the Palaeozoic-to-recent Congo Basin, is an ancient Precambrian craton that with four others makes up the modern continent of Africa. These cratons were formed between about 3.6 and 2.0 billion years ago and have been tectonically stable since that time. All of these cratons are bounded by younger fold belts formed between 2.0 billion and 300 million years ago.

Caledonian orogeny

The Caledonian orogeny was a mountain-building era recorded in the northern parts of the British Isles, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe. The Caledonian orogeny encompasses events that occurred from the Ordovician to Early Devonian, roughly 490–390 million years ago (Ma). It was caused by the closure of the Iapetus Ocean when the continents and terranes of Laurentia, Baltica and Avalonia collided.

The Pan-African orogeny was a series of major Neoproterozoic orogenic events which related to the formation of the supercontinents Gondwana and Pannotia about 600 million years ago. This orogeny is also known as the Pan-Gondwanan or Saldanian Orogeny. The Pan-African orogeny and the Grenville orogeny are the largest known systems of orogenies on Earth. The sum of the continental crust formed in the Pan-African orogeny and the Grenville orogeny makes the Neoproterozoic the period of Earth's history that has produced most continental crust.

Adelaide Superbasin A major geological province in central South Australia

The Adelaide Superbasin is a major Neoproterozoic to middle Cambrian geological province in central and south-east South Australia, western New South Wales, and western Victoria.

Gondwana Neoproterozoic to Carboniferous supercontinent

Gondwana or Gondwanaland was a supercontinent that existed from the Neoproterozoic and began to break up during the Jurassic, with the opening of the Drake Passage, separating South America and Antarctica occurring during the Eocene. Gondwana was not considered a supercontinent by the earliest definition, since the landmasses of Baltica, Laurentia, and Siberia were separated from it.

Laurentia A large continental craton that forms the ancient geological core of the North American continent

Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and also the northwestern part of Scotland, known as the Hebridean Terrane. During other times in its past, Laurentia has been part of larger continents and supercontinents and itself consists of many smaller terranes assembled on a network of Early Proterozoic orogenic belts. Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today.

Pangaea Supercontinent from the late Paleozoic to early Mesozoic eras

Pangaea or Pangea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from earlier continental units approximately 335 million years ago, and began to break apart about 175 million years ago. In contrast to the present Earth and its distribution of continental mass, Pangaea was centred on the Equator and surrounded by the superocean Panthalassa. Pangaea is the most recent supercontinent to have existed and the first to be reconstructed by geologists.

Carolina terrane exotic terrane from central Georgia to central Virginia in the United States

The Carolina Terrane, also called the Carolina Superterrane or Carolinia, is an exotic terrane running ~370 miles (600 km) approximately North-South from central Georgia to central Virginia in the United States. It constitutes a major part of the eastern Piedmont Province.

East African Orogeny The main stage in the Neoproterozoic assembly of East and West Gondwana

The East African Orogeny (EAO) is the main stage in the Neoproterozoic assembly of East and West Gondwana along the Mozambique Belt.

A paleocontinent or palaeocontinent is a distinct area of continental crust that existed as a major landmass in the geological past. There have been many different landmasses throughout Earth's time. They range in sizes, some are just a collection of small microcontinents while others are large conglomerates of crust. As time progresses and sea levels rise and fall more crust can be exposed making way for larger landmasses. The continents of the past shaped the evolution of organisms on Earth and contributed to the climate of the globe as well. As landmasses break apart, species are separated and those that were once the same now have evolved to their new climate. The constant movement of these landmasses greatly determines the distribution of organisms on Earth's surface. This is evident with how similar fossils are found on completely separate continents. Also, as continents move, mountain building events (orogenies) occur, causing a shift in the global climate as new rock is exposed and then there is more exposed rock at higher elevations. This causes glacial ice expansion and an overall cooler global climate. Which effects the overall global climate trend of Earth. The movement of the continents greatly affects the overall dispersal of organisms throughout the world and the trend in climate throughout Earth's history. Examples include Laurentia, Baltica and Avalonia, which collided together during the Caledonian orogeny to form the Old Red Sandstone paleocontinent of Laurussia. Another example includes a collision that occurred during the late Pennsylvanian and early Permian time when there was a collision between the two continents of Tarimsky and Kirghiz-Kazakh. This collision was caused because of their askew convergence when the paleoceanic basin closed.

East Antarctic Shield A cratonic rock body which makes up most of the continent Antarctica

The East Antarctic Shield or Craton is a cratonic rock body that covers 10.2 million square kilometers or roughly 73% of the continent of Antarctica. The shield is almost entirely buried by the East Antarctic Ice Sheet that has an average thickness of 2200 meters but reaches up to 4700 meters in some locations. East Antarctica is separated from West Antarctica by the 100–300 kilometer wide Transantarctic Mountains, which span nearly 3,500 kilometers from the Weddell Sea to the Ross Sea. The East Antarctic Shield is then divided into an extensive central craton that occupies most of the continental interior and various other marginal cratons that are exposed along the coast.

Terra Australis Orogen

The Terra Australis Orogen (TAO) was the oceanic southern margin of Gondwana which stretched from South America to Eastern Australia and encompassed South Africa, West Antarctica, New Zealand and Victoria Land in East Antarctica.

References

Notes

  1. "Research paper suggests East Antarctica and North America once linked". The Antarctic Sun. United States Antarctic Program. 26 August 2011. Retrieved 15 November 2012. Reconstruction originally published in Goodge et al. 2008 , Fig 3A, p. 238; research paper mentioned is Loewy et al. 2011. See also: Rejcek 2008.
  2. 1 2 3 McMenamin & McMenamin 1990 , chapter: The Rifting of Rodinia
  3. Redfern 2001 , p. 335
  4. Taube, Aleksandr M., R. S. Daglish, and M. A. Cantab. Russko-angliiskii Slovar' =: Russian-english Dictionary. Moskva: Russkii iazyk, 1993. Print. ISBN   5200018838
  5. 1 2 Li et al. 2008
  6. Meert 2012 , Supercontinents in Earth history, p. 998
  7. Zhao et al. 2002; Zhao et al. 2004
  8. 1 2 Piper 2013
  9. Dewey & Burke 1973; the name 'Rodinia' was first used in McMenamin & McMenamin 1990
  10. See for example the correlation between the North American Grenville and European Dalslandian orogenies in Ziegler 1990 , p. 14; for the correlation between the Australian Musgrave orogeny and the Grenville orogeny see Wingate, Pisarevsky & Evans 2002 , Implications for Rodinia reconstructions, pp. 124–126; fig. 5, p. 127
  11. For a comparison of the SWEAT, AUSWUS, AUSMEX, and Missing-link reconstructions see Li et al. 2008 , Fig. 2, p. 182. For a comparison between the "consensus" Rodinia of Li et al. 2008 and the original proposal of McMenamin & McMenamin 1990 see Nance, Murphy & Santosh 2014 , Fig. 11, p. 9.
  12. Examples of reconstructions can be found in Stanley 1999 , pp. 336–337; Weil et al. 1998 , Fig. 6, p. 21; Torsvik 2003 , Fig. 'Rodinia old and new', p. 1380; Dalziel 1997 , Fig. 11, p. 31; Scotese 2009 , Fig. 1, p. 69
  13. Moores 1991; Goodge et al. 2008
  14. Li et al. 2008 , Fig. 4, p. 188; fig. 8, p. 198
  15. Wen, Bin; Evans, David A. D.; Li, Yong-Xiang (2017-01-15). "Neoproterozoic paleogeography of the Tarim Block: An extended or alternative "missing-link" model for Rodinia?". Earth and Planetary Science Letters. 458: 92–106. Bibcode:2017E&PSL.458...92W. doi:10.1016/j.epsl.2016.10.030.
  16. 1 2 "Other Reconstructions for Rodinia based on sources for Mojavia". Department of Geological Sciences, University of Colorado Boulder. May 2002. Retrieved 20 September 2010.
  17. Scotese 2009; Torsvik, Gaina & Redfield 2008
  18. 1 2 Torsvik 2003 , p. 1380
  19. Piper 2010
  20. Bogdanova, Pisarevsky & Li 2009 , Breakup of Rodinia (825–700 Ma), pp. 266–267
  21. Torsvik 2003 , Fig. 'Rodinia old and new', p. 1380
  22. See for example reconstructions in Pisarevsky et al. 2008 , Fig. 4, p. 19
  23. Donnadieu et al. 2004 [ page needed ]

Bibliography