The Terra Australis Orogen ( TAO ) was a late Neoproterozoic - to Paleozoic -age accretionary orogen that ringed the ancient, active southern margin of the supercontinents Rodinia and later Pannotia (also called Greater Gondwana ). This vast orogenic belt stretched for c. 18,000 km (11,000 mi) along-strike and involved, from west to east (in the ancient, paleogeographic reference frame), landmasses belonging to the modern-day Andean margin of South America , the South African Cape , West Antarctica , Victoria Land in East Antarctica , Eastern Australia , Tasmania , and New Zealand . The formation of the Terra Australis Orogen is associated with the breakup of Rodinia at the end of the Neoproterozoic Era and the creation of Panthalassa , the paleo- Pacific Ocean , and it was succeeded by the Gondwanide orogeny with the formation of the supercontinent Pangea in the middle Paleozoic Era .
31-607: Terra Australis Orogen formed in the Neoproterozoic and Paleozoic . The decline of orogenic activity in the late Paleozoic is related to the assembly of the supercontinent Pangea . The orogeny did not end by a continental collision and was succeeded by the Gondwanide orogeny . c. 18,000 km (11,000 mi) long and up to 1,600 km (990 mi) wide, the TAO was one of the longest and longest-lived active continental margin in
62-920: A near-static position between 750 and 633 Ma. This latter solution predicts that break-up was confined to the Ediacaran period and produced the dramatic environmental changes that characterised the transition between the Precambrian and Phanerozoic . However, this theory has been widely criticized, as incorrect applications of paleomagnetic data have been pointed out. In 2009 UNESCO's International Geoscience Programme project 440, named "Rodinia Assembly and Breakup," concluded that Rodinia broke up in four stages between 825 and 550 Ma: The Rodinia hypothesis assumes that rifting did not start everywhere simultaneously. Extensive lava flows and volcanic eruptions of Neoproterozoic age are found on most continents, evidence for large scale rifting about 750 Ma. As early as 850 to 800 Ma,
93-669: A rift developed between the continental masses of present-day Australia, East Antarctica, India and the Congo and Kalahari cratons on one side and later Laurentia, Baltica, Amazonia and the West African and Rio de la Plata cratons on the other. This rift developed into the Adamastor Ocean during the Ediacaran . Around 550 Ma, near the boundary between the Ediacaran and Cambrian, the first group of cratons fused again with Amazonia, West Africa and
124-453: Is known about Rodinia's configuration and geodynamic history. Paleomagnetic evidence provides some clues to the paleolatitude of individual pieces of the Earth's crust , but not to their longitude, which geologists have pieced together by comparing similar geologic features, often now widely dispersed. The extreme cooling of the global climate around 717–635 Ma (the so-called Snowball Earth of
155-741: Is the last of the three geologic eras of the Proterozoic eon , spanning from 1 billion to 538.8 million years ago, and is the last era of the Precambrian "supereon". It is preceded by the Mesoproterozoic era and succeeded by the Paleozoic era of the Phanerozoic eon, and is further subdivided into three periods , the Tonian , Cryogenian and Ediacaran . One of the most severe glaciation event known in
186-696: The Mayanian (from 1000 to 850 Ma) followed by the Baikalian (from 850 to 650 Ma). The idea of the Neoproterozoic Era was introduced in the 1960s. Nineteenth-century paleontologists set the start of multicellular life at the first appearance of hard-shelled arthropods called trilobites and archeocyathid sponges at the beginning of the Cambrian Period. In the early 20th century, paleontologists started finding fossils of multicellular animals that predated
217-479: The Cryogenian period) and the rapid evolution of primitive life during the subsequent Ediacaran and Cambrian periods are thought to have been triggered by the breaking up of Rodinia or to a slowing down of tectonic processes . The idea that a supercontinent existed in the early Neoproterozoic arose in the 1970s, when geologists determined that orogens of this age exist on virtually all cratons . Examples are
248-728: The Grenville orogeny in North America and the Dalslandian orogeny in Europe. Since then, many alternative reconstructions have been proposed for the configuration of the cratons in this supercontinent. Most of these reconstructions are based on the correlation of the orogens on different cratons. Though the configuration of the core cratons in Rodinia is now reasonably well known, recent reconstructions still differ in many details. Geologists try to decrease
279-772: The Vendian , while Chinese geologists referred to it as the Sinian , and most Australians and North Americans used the name Ediacaran. However, in 2004, the International Union of Geological Sciences ratified the Ediacaran Period to be a geological age of the Neoproterozoic, ranging from 635 to 538.8 (at the time to 542) million years ago. The Ediacaran Period boundaries are the only Precambrian boundaries defined by biologic Global Boundary Stratotype Section and Points , rather than
310-533: The history of Earth , lasting from the beginning of its formation during the break-up of the Neoproterozoic supercontinent Rodinia . The TAO evolved through a series of extensional 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
341-761: The Cambrian. A complex fauna was found in South West Africa in the 1920s but was inaccurately dated. Another fauna was found in South Australia in the 1940s, but it was not thoroughly examined until the late 1950s. Other possible early animal fossils were found in Russia, England, Canada, and elsewhere (see Ediacaran biota ). Some were determined to be pseudofossils , but others were revealed to be members of rather complex biotas that remain poorly understood. At least 25 regions worldwide have yielded metazoan fossils older than
SECTION 10
#1732847922721372-402: The Neoproterozoic (early Tonian), but physical evidence for such animal life is lacking. Possible keratose sponge fossils have been reported in reefs dated to c. 890 million years before the present, but remain unconfirmed. The nomenclature for the terminal period of the Neoproterozoic Era has been unstable. Russian and Nordic geologists referred to the last period of the Neoproterozoic as
403-607: The Rio de la Plata cratons during the Pan-African orogeny, which caused the development of Gondwana. In a separate rifting event about 610 Ma, the Iapetus Ocean formed. The eastern part of this ocean formed between Baltica and Laurentia, the western part between Amazonia and Laurentia. Because the timeframe of this separation and the partially contemporaneous Pan-African orogeny are difficult to correlate, it might be that all continental mass
434-705: The TAO was a series of terranes ( Avalonia – Carolina – Cadomia ) which were rifted off the western margin of Gondwana and added to Laurentia in the Late Palaeozoic, while its other end probably reached past Australia into New Guinea. In 1937 Alexander du Toit 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. Neoproterozoic Gradstein et al., 2012 Ediacaran Period, 630–541.0 Ma The Neoproterozoic Era
465-495: The absolute Global Standard Stratigraphic Ages . 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 (Ga) and broke up 750–633 million years ago (Ma). Valentine & Moores 1970 were probably the first to recognise a Precambrian supercontinent, which they named "Pangaea I." It
496-452: The breakup of Rodinia onwards. Rodinia is considered to have formed between 1.3 and 1.23 Ga and broke up again before 750 Ma. Rodinia was surrounded by the superocean Mirovia . According to J.D.A. Piper, Rodinia is one of two models for the configuration and history of the continental crust in the latter part of Precambrian times. The other is Paleopangea , Piper's own concept. Piper proposes an alternative hypothesis for this era and
527-462: The classical Precambrian–Cambrian boundary (which is currently dated at 538.8 million years ago ). A few of the early animals appear possibly to be ancestors of modern animals. Most fall into ambiguous groups of frond-like organisms; discoids that might be holdfasts for stalked organisms ("medusoids"); mattress-like forms; small calcareous tubes; and armored animals of unknown provenance. These were most commonly known as Vendian biota until
558-532: The crustal rocks rise up relative to their surroundings. This rising creates areas of higher altitude where the air is cooler and ice is less likely to melt with changes in season, and it may explain the evidence of abundant glaciation in the Ediacaran. The rifting of the continents created new oceans and seafloor spreading , which produces warmer, less dense oceanic crust . Lower-density, hot oceanic crust will not lie as deep as older, cool oceanic lithosphere. In periods with relatively large areas of new lithosphere,
589-561: The equator—a state known as the " Snowball Earth ". Neoproterozoic time is subdivided into the Tonian (1000–720 Ma), Cryogenian (720–635 Ma) and Ediacaran (635–538.8 Ma) periods. In the regional timescale of Russia, the Tonian and Cryogenian correspond to the Late Riphean ; the Ediacaran corresponds to the Early to middle Vendian. Russian geologists divide the Neoproterozoic of Siberia into
620-846: The formal naming of the Period, and are currently known as Ediacaran Period biota. Most were soft bodied. The relationships, if any, to modern forms are obscure. Some paleontologists relate many or most of these forms to modern animals. Others acknowledge a few possible or even likely relationships but feel that most of the Ediacaran forms are representatives of unknown animal types. In addition to Ediacaran biota, two other types of biota were discovered in China. The Doushantuo Formation (of Ediacaran age) preserves fossils of microscopic marine organisms in great detail. The Huainan biota (of late Tonian age) consists of small worm-shaped organisms. Molecular phylogeny suggests that animals may have emerged even earlier in
651-488: The geologic record occurred during the Cryogenian period of the Neoproterozoic, when global ice sheets may have reached the equator and created a " Snowball Earth " lasting about 100 million years. The earliest fossils of complex life are found in the Tonian period in the form of Otavia , a primitive sponge , and the earliest fossil evidence of metazoan radiation are found in the Ediacaran period, which included
SECTION 20
#1732847922721682-571: The late Mesoproterozoic, straddled the equator. During the Tonian, rifting commenced which broke Rodinia into a number of individual land masses. Possibly as a consequence of the low-latitude position of most continents, several large-scale glacial events occurred during the Neoproterozoic Era including the Sturtian and Marinoan glaciations of the Cryogenian Period. These glaciations are believed to have been so severe that there were ice sheets at
713-421: The marine life of its time. In the Cryogenian , Earth experienced large glaciations , and temperatures were at least as cool as today. Substantial parts of Rodinia may have been covered by glaciers or the southern polar ice cap . Low temperatures may have been exaggerated during the early stages of continental rifting. Geothermal heating peaks in crust about to be rifted, and since warmer rocks are less dense,
744-497: The namesaked Ediacaran biota as well as the oldest definitive cnidarians and bilaterians in the fossil record. According to Rino and co-workers, the sum of the continental crust formed in the Pan-African orogeny and the Grenville orogeny makes the Neoproterozoic the period of Earth's history that has produced most continental crust. At the onset of the Neoproterozoic the supercontinent Rodinia , which had assembled during
775-418: The ocean floors come up, causing the sea level to rise. The result was a greater number of shallower seas. The increased evaporation from the oceans' larger water area may have increased rainfall, which in turn increased the weathering of exposed rock. By inputting data on the ratio of stable isotopes O: O into computer models, it has been shown that in conjunction with quick weathering of volcanic rock ,
806-448: The previous ones. This idea rejects that Rodinia ever existed as a transient supercontinent subject to progressive break-up in the late Proterozoic and instead that this time and earlier times were dominated by a single, persistent "Paleopangaea" supercontinent. As evidence, he suggests an observation that the palaeomagnetic poles from the continental crust assigned to this time conform to a single path between 825 and 633 Ma and latterly to
837-548: The southern (modern coordinates) Proto-Pacific / Iapetus margin of the supercontinent. The TAO ended c. 300 to 230 Ma with the Gondwanide orogeny . 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
868-537: The southwest with the Congo and Kalahari cratons ; and in the northeast with Australia , India and eastern Antarctica . The positions of Siberia and North and South China north of the North American craton differ strongly depending on the reconstruction: Little is known about the paleogeography before the formation of Rodinia. Paleomagnetic and geologic data are only definite enough to form reconstructions from
899-709: The uncertainties by collecting geological and paleomagnetical data. Most reconstructions show Rodinia's core formed by the North American Craton (the later paleocontinent of Laurentia ), surrounded in the southeast with the East European Craton (the later paleocontinent of Baltica ), the Amazonian Craton and the West African Craton ; in the south with the Río de la Plata and São Francisco cratons ; in
930-490: Was again joined in one supercontinent between roughly 600 and 550 Ma. This hypothetical supercontinent is called Pannotia . Unlike later supercontinents, Rodinia was entirely barren. It existed before complex life colonized on dry land. Based on sedimentary rock analysis, Rodinia's formation happened when the ozone layer was not as extensive as it is now. Ultraviolet light discouraged organisms from inhabiting its interior. Nevertheless, its existence significantly influenced
961-517: Was renamed "Rodinia" by McMenamin & McMenamin 1990 , who also were the first to produce a plate reconstruction and propose a temporal framework for the supercontinent. Rodinia formed at c. 1.23 Ga by accretion and collision of fragments produced by breakup of an older supercontinent, Columbia , assembled by global-scale 2.0–1.8 Ga collisional events. Rodinia broke up in the Neoproterozoic, with its continental fragments reassembled to form Pannotia 633–573 Ma. In contrast with Pannotia, little