Adamastor Ocean
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The Adamastor Ocean was a "proto-Atlantic" ocean that formed with the break-up of the Rodinia supercontinent 780-750 . It separated the Río de la Plata Craton from the
Congo Craton The Congo Craton, covered by the Palaeozoic-to-recent Congo Basin, is an ancient Precambrian craton that with four others (the Kaapvaal, Zimbabwe, Tanzania, and West African cratons) makes up the modern continent of Africa. These cratons were fo ...
. The inversion of the Adamastor Ocean began about 640 Ma with the development of a large back-arc basin along the western margin of the
Kalahari Craton The Kalahari Craton is a craton, an old and stable part of the continental lithosphere, that occupies large portions of South Africa, Botswana, Namibia and Zimbabwe. It consists of two cratons separated by the Limpopo Belt: the larger Kaapvaal Cra ...
, and the ocean closed when Río de la Plata collided with Kalahari about 545 Ma along the sinistral Sierra Ballena Shear Zone. The
São Francisco Craton The São Francisco Craton is an ancient craton in the eastern part of South America. The craton crops out in the Brazilian states of Minas Gerais and Bahia. It includes a number of blocks of Archean basement, separated by orogenic belts. The b ...
and the Río de la Plata Craton amalgamated 630–620 Ma, closing the Adamastor Ocean on the South American side and forming the
Mantiqueira Mountains The Mantiqueira Mountains (Portuguese: ''Serra da Mantiqueira iterally: Mantiqueira Mountains Chain') are a mountain range in Southeastern Brazil, with parts in the states of São Paulo, Minas Gerais and Rio de Janeiro. It rises abruptly from the ...
around 600 Ma. In 2020 a group of geologists proposed an alternative model for the Adamastor Ocean in which it is reduced to a intracontinental rift system with only some minor oceanic crust developing in its southern part.


Etymology

South African geologist Chris Hartnady named the Precambrian ocean after the mythical giant Adamastor from
Luís de Camões Luís Vaz de Camões (; sometimes rendered in English as Camoens or Camoëns, ; c. 1524 or 1525 – 10 June 1580) is considered Portugal's and the Portuguese language's greatest poet. His mastery of verse has been compared to that of Shakespear ...
's poem ''
Os Lusíadas ''Os Lusíadas'' (), usually translated as ''The Lusiads'', is a Portuguese epic poem written by Luís Vaz de Camões ( – 1580) and first published in 1572. It is widely regarded as the most important work of Portuguese-language literature ...
'' which celebrates Vasco da Gama's discovery of the sea route to India. Hartnady thought it an appropriate name since the demigod was transformed into stone and personified the Cape of Storms and since
Atlas An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth. Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geograp ...
and Iapetus are associated with the oceans of the northern Atlantic, the North Atlantic Ocean and the Iapetus Ocean respectively.


Geological history

The Adamastor Ocean was narrow in the north, perhaps similar to the Red Sea, but widened southward. C isotope analyses indicate that the ocean water was strongly stratified and thus that it must have been a closed ocean, similar to the Mediterranean, but probably covered by ice during the
Sturtian The Sturtian glaciation was a Snowball Earth glaciation, or perhaps multiple glaciations, during the Cryogenian Period when the Earth experienced repeated large-scale glaciations. The duration of the Sturtian glaciation has been variously defined, ...
and
Marinoan glaciation The Marinoan glaciation, sometimes also known as the Varanger glaciation, was a period of worldwide glaciation that lasted from approximately 650 to 632.3 ± 5.9 Ma (million years ago) during the Cryogenian period. This glaciation possibly cover ...
s. Ocean floor adjacent to the Marmora Terrane (near the Orange River in South Africa) formed 740–580 Ma, dates that represent the first rifting and the first accretion respectively. The Adamastor Ocean closed in three episodes: the Río de la Plata Craton first collided with the Congo Craton, which then collided with the Kalahari Craton, which finally collided with Río de la Plata.


See also

* Brasiliano orogeny * Geology of Namibia


References


Notes


Sources

* * * * * {{Refend Historical oceans Precambrian Africa Precambrian South America