Columbia_(supercontinent)

Columbia (supercontinent)

Columbia is the name of one of the Earth's oldest supercontinents. It was first proposed by J.J.W. Rogers and M. Santosh, and is thought to have existed approximately 1.8 to 1.5 billion years (Ga) ago in the Paleoproterozoic Era, making it the oldest hypothesized continent. It consisted of the proto-cratons that made up the former continents of Laurentia, Baltica, Ukraine, Amazonia, Australia, and possibly Siberia, North China and Kalahari as well. The existence of Columbia is based upon paleomagnetic data.

Size and location

Columbia is estimated to have been about 12,900 kilometres (8,000 miles) from North to South, and about 4,800 km (3,000 miles) across at its widest part. The east coast of India was attached to western North America, with southern Australia against western Canada. Most of South America rotated so 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.

Assembly

Columbia was assembled along global-scale 2.0-1.8 Ga collisional orogens and contained almost all of Earth’s continental blocks. The cratonic blocks in South America and West Africa were welded by the 2.1-2.0 Ga Transamazonian and Eburnean Orogens; the Kaapvaal and Zimbabwe Cratons in southern Africa were collided along the ~2.0 Ga Limpopo Belt; the cratonic blocks of Laurentia were sutured along the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava, Torngat and Nagssugtoqidain Orogens; the Kola, Karelia, Volgo-Uralia and Sarmatia (Ukrainian) Cratons in Baltica (Eastern Europe) were joined by the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian and Pachelma Orogens; the Anabar and Aldan Cratons in Siberia were connected by the 1.9–1.8 Ga Akitkan and Central Aldan Orogens; the East Antarctica and an unknown continental block were joined by the Transantarctic Mountains Orogen; the South and North Indian Blocks were amalgamated along the Central Indian Tectonic Zone; and the Eastern and Western Blocks of the North China Craton were welded together by the ~1.85 Ga Trans-North China Orogen.

Following its final assembly at ~1.8 Ga, the supercontinent Columbia underwent long-lived (1.8-1.3 Ga), subduction-related growth via accretion at key continental margins, forming a 1.8-1.3 Ga large magmatic accretionary belt along the present-day southern margin of North America, Greenland and Baltica. 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. 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. In Australia, 1.8-1.5 Ga accretionary magmatic belts, including the Arunta, Mt. 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. 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.

Fragmentation

Columbia began to fragment about 1.6 Ga ago, associated with continental rifting along the western margin of Laurentia (Belt-Purcell Supergroup), eastern India (Mahanadi and the Godavari), 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).

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 dike swarms in North America.

The rifted fragments formed the supercontinent Rodinia about 500 million years later. Recent studies on the rifting history of Columbia can be found in Hou, G., Santosh, M., Qian, X., Lister, G.S., Li, J. (2008) Configuration of the Late Paleoproterozoic supercontinent Columbia: insights from radiating mafic dyke swarms. Gondwana Research, in press, doi: 10.1016/j.gr.2008.01.010.