The Terra Australis Orogen (TAO) was the oceanic southern margin of

Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...

which stretched from

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

Eastern Australia The eastern states of Australia are the states adjoining the east continental coastline of Australia. These are the mainland states of Victoria, New South Wales and Queensland, and the island state of Tasmania. The Australian Capital Territory ...

and encompassed

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

West Antarctica West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of that continent that lies within the Western Hemisphere, and includes the Antarctic Peninsula. It is separated from East Antarctica by the Transant ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

and

Victoria Land Victoria Land is a region in eastern Antarctica which fronts the western side of the Ross Sea and the Ross Ice Shelf, extending southward from about 70°30'S to 78°00'S, and westward from the Ross Sea to the edge of the Antarctic Plateau. It ...

East Antarctica East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying on the Indian Ocean side of the continent, separated from West Antarctica by the Transantarctic Mountains. It lies almost ...

Origins

Terra Australis Orogen formed in the

Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...

and

Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...

. The decline of orogenic activity in the late Paleozoic is related to the assembly of the

supercontinent In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...

Pangea Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...

. The orogeny did not end by a

continental collision In geology, continental collision is a phenomenon of plate tectonics that occurs at convergent boundaries. Continental collision is a variation on the fundamental process of subduction, whereby the subduction zone is destroyed, mountains prod ...

and was succeeded by the

Gondwanide orogeny The Gondwanide orogeny was an orogeny active in the Permian that affected parts of Gondwana that are by current geography now located in southern South America, South Africa, Antarctica, Australia and New Guinea. The zone of deformation in Arge ...

. long and up to wide, the TAO was one of the longest and longest-lived active continental margin in the

history of Earth The history of Earth concerns the development of planet Earth from its formation to the present day. Nearly all branches of natural science have contributed to understanding of the main events of Earth's past, characterized by constant geologi ...

, lasting from the beginning of its formation during the break-up of the Neoproterozoic supercontinent

Rodinia Rodinia (from the Russian родина, ''rodina'', meaning "motherland, birthplace") was a Mesoproterozoic and Neoproterozoic supercontinent that assembled 1.26–0.90 billion years ago and broke up 750–633 million years ago. were probably ...

. The TAO evolved through a series of

extensional In any of several fields of study that treat the use of signs — for example, in linguistics, logic, mathematics, semantics, semiotics, and philosophy of language — an extensional context (or transparent context) is a syntactic environment in w ...

back-arcs separated by compressional events when the subducting oceanic plate got stuck in Gondwana's margin. As Gondwana was amalgamated in the Early Palaeozoic during the so-called Pan-African orogenies the TAO propagated along the southern (modern coordinates) Proto-Pacific/

Iapetus In Greek mythology, Iapetus (; ; grc, Ἰαπετός, Iapetós), also Japetus, is a Titan, the son of Uranus and Gaia and father of Atlas, Prometheus, Epimetheus, and Menoetius. He was also called the father of Buphagus and Anchiale in other ...

margin of the supercontinent. The TAO ended with the

. This and younger orogens covers most of the outboard margin of the TAO, and, likewise, the inboard margin is almost entirely covered by younger deposits and ice but remains exposed in Australia along the Torrens Hinge Line or Delamarian orogeny. One end of the TAO was a series of

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its own ...

s (

Avalonia Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of Wester ...

– Carolina– Cadomia) which were rifted off the western margin of Gondwana and added to

Laurentia 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 ...

in the Late Palaeozoic, while its other end probably reached past Australia into New Guinea. In 1937

Alexander du Toit Alexander Logie du Toit FRS ( ; 14 March 1878 – 25 February 1948) was a geologist from South Africa and an early supporter of Alfred Wegener's theory of continental drift. Early life and education Du Toit was born in Newlands, Cape Town in ...

proposed the Samfrau Orogeny as an evidence for Gondwana. His concept includes the orogenies of West Gondwana and orogenies that are now considered separate events but excludes those of East Gondwana.

References

; Notes ; Sources * * * {{Major South American geological formations Orogenies of Africa Orogenies of Antarctica Orogenies of Australia Orogenies of New Zealand Orogenies of South America Cambrian orogenies Geology of Antarctica Geology of Argentina Geology of Australia Geology of Chile Geology of South Africa Devonian orogenies Ediacaran orogenies Neoproterozoic orogenies Silurian orogenies Ordovician orogenies

Origins

See also

References