Columbia (supercontinent)

Rendering of the supercontinent Columbia about 1.6 billion years ago.

Columbia, also known as Nuna and Hudsonland, was one of Earth's ancient supercontinents. It was first proposed by Rogers & Santosh 2002[1] and is thought to have existed approximately 2.5 to 1.6 billion years (Ga) ago in the Paleoproterozoic Era. Zhao et al. 2002[2] proposed that the assembly of the supercontinent Columbia was completed by global-scale collisional events during 2.1–1.8 Ga.

Columbia consisted of proto-cratons that made up the cores of the continents of Laurentia, Baltica, Ukrainian Shield, Amazonian Shield, Australia, and possibly Siberia, North China, and Kalaharia as well.

The evidence of Columbia's existence is based upon geological[2][3] and paleomagnetic data.[4]

Size and location

Columbia is estimated to have been about 12,900 km (8,000 mi) from North to South, and about 4,800 km (3,000 mi) across at its broadest part. The eastern coast of India was attached to western North America, with southern Australia against western Canada. In this era most of South America was rotated such that the western edge of modern-day Brazil lined up with eastern North America, forming a continental margin that extended into the southern edge of Scandinavia.[5]

Assembly

Columbia was assembled along global-scale 2.1–1.8 Ga collisional orogens and contained almost all of Earth’s continental blocks.[2]

According to Zhao et al. 2002:[2]

Outgrowth

Following its final assembly at c. 1.8 Ga, the supercontinent Columbia underwent long-lived (1.8–1.3 Ga), subduction-related growth via accretion at key continental margins,[3] forming a 1.8–1.3 Ga great magmatic accretionary belt along the present-day southern margin of North America, Greenland, and Baltica.[6] It includes the 1.8–1.7 Ga Yavapai, Central Plains and Makkovikian Belts, 1.7–1.6 Ga Mazatzal and Labradorian Belts, 1.5–1.3 Ga St. Francois and Spavinaw Belts, and 1.3–1.2 Ga Elzevirian Belt in North America; the 1.8–1.7 Ga Ketilidian Belt in Greenland; and the 1.8–1.7 Transscandinavian Igneous Belt, 1.7–1.6 Ga Kongsberggian-Gothian Belt, and 1.5–1.3 Ga Southwest Sweden Granitoid Belt in Baltica.[7] Other cratonic blocks also underwent marginal outgrowth at about the same time.

In South America, a 1.8–1.3 Ga accretionary zone occurs along the western margin of the Amazonia Craton, represented by the Rio Negro, Juruena, and Rondonian Belts.[3] In Australia, 1.8–1.5 Ga accretionary magmatic belts, including the Arunta, Mount Isa, Georgetown, Coen, and Broken Hill Belts, occur surrounding the southern and eastern margins of the North Australia Craton and the eastern margin of the Gawler Craton.[3] In China, a 1.8–1.4 Ga accretionary magmatic zone, called the Xiong’er belt (Group), extends along the southern margin of the North China Craton.[3][8]

Fragmentation

Columbia began to fragment about 1.6 Ga ago, associated with continental rifting along the western margin of Laurentia (Belt-Purcell Supergroup),[3] eastern India (Mahanadi and the Godavari),[9] southern margin of Baltica (Telemark Supergroup), southeastern margin of Siberia (Riphean aulacogens), northwestern margin of South Africa (Kalahari Copper Belt), and northern margin of the North China Block (Zhaertai-Bayan Obo Belt).[3]

The fragmentation corresponded with widespread anorogenic magmatic activity, forming anorthosite-mangerite-charnockite-granite (AMCG) suites in North America, Baltica, Amazonia, and North China, and continued until the final breakup of the supercontinent at about 1.3–1.2 Ga, marked by the emplacement of the 1.27 Ga Mackenzie and 1.24 Ga Sudbury mafic dyke swarms in North America.[3] Other dyke swarms associated with extensional tectnics and the break-up of Columbia include the Satakunta-Ulvö dyke swarm in Fennoscandia and the Galiwinku dyke dwarm in Australia.[10]

Configuration

In the initial configuration of Rogers and Santosh (2002), South Africa, Madagascar, India, Australia, and attached parts of Antarctica are placed adjacent to the western margin of North America, whereas Greenland, Baltica (Northern Europe), and Siberia are positioned adjacent to the northern margin of North America, and South America is placed against West Africa. In the same year (2002), Zhao et al. (2002) proposed an alternative configuration of Columbia,[11] in which the fits of Baltica and Siberia with Laurentia and the fit of South America with West Africa are similar to those of the Rogers and Santosh (2002) configuration, whereas the fits of India, East Antarctica, and Australia with Laurentia are similar to their corresponding fits in the configuration of Rodinia.

This continental configuration is based on the available geological reconstructions of 2.1–1.8 Ga orogens and related Archean cratonic blocks, especially on those reconstructions between South America vs West Africa, Western Australia vs South Africa, Laurentia vs Baltica, Siberia vs Laurentia, Laurentia vs Central Australia, East Antarctica vs Laurentia, and North China vs India.[11][12] Of these reconstructions, the fits of Baltica and Siberia with Laurentia, South America with West Africa, and Southern Africa with Western Australia are also consistent with paleomagnetic data.[4]

The new configuration of the Columbia supercontinent was reconstructed by Guiting Hou (2008) based on the reconstruction of giant radiating dike swarms.[13]

See also

References

Notes

  1. ↑ Rogers & Santosh 2002, Introduction, p. 5
  2. 1 2 3 4 Zhao et al. 2002, Abstract
  3. 1 2 3 4 5 6 7 8 Zhao et al. 2004, Abstract
  4. 1 2 Pesonen et al. 2003; Bispo-Santos et al. 2008
  5. ↑ "New Supercontinent Dubbed Columbia Once Ruled Earth". SpaceDaily. 2002-04-18. Retrieved 2006-03-11.
  6. ↑ Zhao et al. 2004, Summary and discussion, pp. 114–115
  7. ↑ Zhao et al. 2004, Fig. 17, p. 114
  8. ↑ Zhao, He & Sun 2009
  9. ↑ Zhao et al. 2004, 2. Paleo-Mesoproterozoic supercontinent—Columbia, pp. 93–94
  10. ↑ Goldberg, Adrian S. (2010). "Dyke swarms as indicators of major extensional events in the 1.9–1.2 Ga Columbia supercontinent". Journal of Geodynamics. 50 (3–4): 176–190.
  11. 1 2 Zhao et al. 2002
  12. ↑ Zhao et al. 2004
  13. ↑ Hou et al. 2008

Sources

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