Columbia (continent)

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Columbia is the name of a hypothetical paleoproterozoic supercontinent in geological history, which is said to have existed from 1800 to about 1600 million years ago (around the same time as the Statherium ). It is said to have united almost all of the larger continental fragments that existed on earth at that time.

Naming

The term was coined by John JW Rogers and M. Santosh in a work from 2002. They indicate as derivatio nominis that the name should allude to the key connection between India and the Columbia region in the US state of Washington .

Columbia as a geological continent

Columbia was formed between 2100 and 1800 million years ago. It contained almost all of the larger continental blocks on earth that existed at the time. According to Rogers and Santosh (2002) the east coast of today's India touched western North America . Southern Australia was even further north on western Canada . Most of South America was shifted in such a way that the western edge of today's Brazil lay against eastern North America and reached as far as Scandinavia . After its reconstruction, Columbia was formed by the collision of three previously formed major continents, Arctica (North America, Siberia, Greenland, Baltica), Atlantica (eastern South America and western Africa) and a block consisting of parts of Australia, India, Madagascar, South Africa and Parts of Antarctica. However, the exact position of the cratons relative to one another is highly controversial. Thus, Zhao et al. (2004) Columbia completely different. In their reconstruction, Antarctica lies southwest of North America, then Australia and some smaller blocks to the north. To the west of Antarctica followed India and northern China. North of North America joined Siberia, Greenland and east of them Baltica . Atlantica was south of Baltica, separated from the eastern edge of North America by a larger marine area.

Following the “Pangea” situation, between 1800 and 1300 million long subduction and accretion processes took place at the margins. Between 1800 and 1300 million years, a wide magmatic accretion belt formed along the southern edge of what is now North America, Greenland and the core of the later Baltica . In South America there is a 1,800 to 1,300 million year old accretion zone along the western edge of the Amazonia craton. In Australia, an igneous belt that is 1,800 to 1,500 million years old surrounds the southern and eastern edges of the North Australian Craton and the eastern edge of the Gawler Craton . In China, an accretionary magmatic belt that is 1,800 to 1,400 million years old extends along the southern edge of the North China Craton. The disintegration of the supercontinent Columbia began around 1,600 million years ago with continental rifting on the western edge of Laurentia, the southern edge of Baltica, the southeastern edge of Siberia , the northwestern edge of South Africa, and the northern edge of northern China. The breaking and fragmentation of the supercontinent coincides with widespread igneous activity that formed anorthosite-mangerite-charnockite-granite (AMCG) suites in North America, Baltica, Amazonia and northern China. Magmatic activity lasted until the final collapse of Columbia around 1,300 to 1,200 million years ago, when the mafic MacKenzie and Sudbury gang swarms formed.

The existence of a supercontinent Columbia is assumed primarily due to approximately global magmatic events in the period from 2100 to 1300 million years. The north-south extension is assumed to be 12,900 kilometers, with 4800 kilometers at its widest point.

In the more recent literature, the originally differently defined geological continent Nuna is equated with Columbia.

Geological significance

After the formation of Columbia, the atmospheric conditions were relatively constant between 1.85 and 0.85 billion years ago, i.e. for about 1 billion years. During this time, the second warm climate phase in the earth's history, there were no major climatic changes or changes in the oceans, which is why some scientists call it the “ boring billion ”. As a result, between 1.7 and 1.2 billion years ago there was no major dramatic event like the one that caused mass extinction.

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literature

Web links

Individual evidence

  1. ^ Nick MW Roberts: The boring billion? - Lid tectonics, continental growth and environmental change associated with the Columbia supercontinent. In: Geoscience Frontiers. 4, 2013, p. 681, doi : 10.1016 / j.gsf.2013.05.004 .