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77-717: The Laurentian Region, as recognized by Natural Resources Canada, is part of the plateau and dissected southern rim of the Canadian Shield in the province of Québec . It is a western extension of the Laurentian Mountains , and continues across the Ottawa Valley into Ontario as the Opeongo Hills . Viewed from the valleys of the Ottawa and St. Lawrence Rivers , the south-facing escarpments of

154-400: A peneplain of modern relief. A peneplain with the occasional moderately high monadnocks left behind during the peneplanation of the rest of the surface. The erosion of the region must have been far advanced in prehistoric times, even practically completed, because the even peneplain surface is overlapped by fossiliferous marine strata from an early geological date, Cambrian . This shows that

231-412: A plateau ( / p l ə ˈ t oʊ , p l æ ˈ t oʊ , ˈ p l æ t oʊ / ; French: [plato] ; pl. : plateaus or plateaux ), also called a high plain or a tableland , is an area of a highland consisting of flat terrain that is raised sharply above the surrounding area on at least one side. Often one or more sides have deep hills or escarpments . Plateaus can be formed by

308-465: A GSSP, but it is expected to be defined in strata marking the first appearance of trilobites in Gondwana . There was a rapid diversification of metazoans during this epoch, but their restricted geographic distribution, particularly of the trilobites and archaeocyaths , have made global correlations difficult, hence ongoing efforts to establish a GSSP. The Miaolingian is the third series/epoch of

385-568: A number of processes, including upwelling of volcanic magma , extrusion of lava , and erosion by water and glaciers . Plateaus are classified according to their surrounding environment as intermontane, piedmont, or continental. A few plateaus may have a small flat top while others have wider ones. Plateaus can be formed by a number of processes, including upwelling of volcanic magma, extrusion of lava, plate tectonics movements, and erosion by water and glaciers. Volcanic plateaus are produced by volcanic activity . The Columbia Plateau in

462-638: A profound change in life on Earth ; prior to the Period, the majority of living organisms were small, unicellular and poorly preserved. Complex, multicellular organisms gradually became more common during the Ediacaran, but it was not until the Cambrian that the rapid diversification of lifeforms, known as the Cambrian explosion , produced the first representatives of most modern animal phyla . The Period

539-553: A river was already there, though not necessarily on exactly the same course. Then, subterranean geological forces caused the land in that part of North America to gradually rise by about a centimeter per year for millions of years. An unusual balance occurred: the river that would become the Colorado River was able to erode into the crust of the Earth at a nearly equal rate to the uplift of the plateau. Now, millions of years later,

616-517: A sliver of continental terrane rifted from Laurentia with the narrow Taconic seaway opening between them. The remains of this terrane are now found in southern Scotland, Ireland, and Newfoundland. Intra-oceanic subduction either to the southeast of this terrane in the Iapetus, or to its northwest in the Taconic seaway, resulted in the formation of an island arc . This accreted to the terrane in

693-558: A subduction zone was closing the narrow seaway between the North West Kunlun region of Tarim and the South West Kunlun terrane. North China lay at equatorial to tropical latitudes during the early Cambrian, although its exact position is unknown. Much of the craton was covered by shallow seas, with land in the northwest and southeast. Northern North China was a passive margin until the onset of subduction and

770-455: Is also unique in its unusually high proportion of lagerstätte deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. By the end of the Cambrian, myriapods , arachnids , and hexapods started adapting to the land, along with the first plants . The term Cambrian is derived from the Latin version of Cymru ,

847-441: Is characterised by complex, sediment-penetrating Phanerozoic-type trace fossils , and its upper part by small shelly fossils. The second series/epoch of the Cambrian is currently unnamed and known as Cambrian Series 2 . It lasted from c. 521 Ma to c. 509 Ma. Its two stages are also unnamed and known as Cambrian Stage 3 , c. 521 Ma to c. 514 Ma, and Cambrian Stage 4 , c. 514 Ma to c. 509 Ma. The base of Series 2 does not yet have

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924-622: Is divided into three main flat regions: the Bogotá savanna , the valleys of Ubaté and Chiquinquirá , and the valleys of Duitama and Sogamoso . The parallel Sierra of Andes delimit one of the world highest plateaux: the Altiplano , (Spanish for "high plain"), Andean Plateau or Bolivian Plateau. It lies in west-central South America, where the Andes are at their widest, is the most extensive area of high plateau on Earth outside of Tibet. The bulk of

1001-710: Is sometimes called the Roof of Africa due to its height and large area. Another example is the Highveld which is the portion of the South African inland plateau which has an altitude above approximately 1,500 metres, but below 2,100 metres, thus excluding the Lesotho mountain regions. It is home to some of the largest South African urban agglomerations . In Egypt are the Giza Plateau and Galala Mountain , which

1078-545: Is the Scottish Highlands . Plateaus are classified according to their surrounding environment. The highest African plateau is the Ethiopian Highlands which cover the central part of Ethiopia. It forms the largest continuous area of its altitude in the continent, with little of its surface falling below 1,500 metres (4,921 ft), while the summits reach heights of up to 4,550 metres (14,928 ft). It

1155-658: Is the province of the Laurentian Upland which projects into the United States west and south of Lake Superior . This upland, part of the Canadian Shield along with the Adirondacks , is a greatly deformed structure and is composed primarily of igneous and metamorphic crystalline rocks commonly associated with a rugged landscape. At some prehistoric period, this had a strong relief, but today

1232-572: Is the home of more than 70 million people. The Western Plateau , part of the Australian Shield , is an ancient craton covering much of the continent's southwest, an area of some 700,000 square kilometres. It has an average elevation between 305 and 460 metres. The North Island Volcanic Plateau is an area of high land occupying much of the centre of the North Island of New Zealand, with volcanoes, lava plateaus, and crater lakes,

1309-649: The Altai-Sayan terranes. Some models show a convergent plate margin extending from Greater Avalonia, through the Timanide margin of Baltica, forming the Kipchak island arc offshore of southeastern Siberia and curving round to become part of the Altai-Sayan convergent margin. Along the then western margin, Late Neoproterozoic to early Cambrian rifting was followed by the development of a passive margin. To

1386-587: The Arequipa-Antofalla block united with the South American sector of Gondwana in the early Cambrian. The Kuunga Orogeny between northern ( Congo Craton , Madagascar and India ) and southern Gondwana ( Kalahari Craton and East Antarctica ), which began c. 570 Ma, continued with parts of northern Gondwana over-riding southern Gondwana and was accompanied by metamorphism and the intrusion of granites . Subduction zones , active since

1463-895: The Deccan Plateau (≈1,900,000 km (730,000 sq mi), elevation 300–600 metres (980–1,970 ft)). A large plateau in North America is the Colorado Plateau , which covers about 337,000 km (130,000 sq mi) in Colorado , Arizona , New Mexico , and Utah . In northern Arizona and southern Utah the Colorado Plateau is bisected by the Colorado River and the Grand Canyon . This came to be over 10 million years ago,

1540-824: The Gatineau River in the west (mean elevation 400 m) some 550 km to the Saguenay River in the northeast. Here it attains its maximum elevation north of Quebec City in the Réserve faunique des Laurentides (over 1000 m). Individual summits rise above the plateau surface: Mont Sir Wilfrid (783 m) and Mont Tremblant in the west, Mont Sainte-Anne (815 m) at Quebec, Mont Raoul Blanchard (1166 m), Mont Bleu (1052 m) and Mont des Conscrits (1006 m) in Réserve faunique des Laurentides. Cap Tourmente (579 m) and Mont des Éboulements (770 m) are dramatic examples of

1617-553: The Jiangshanian c. 494 Ma to c. 489.5 Ma, which have defined GSSPs; and the unnamed Cambrian Stage 10 , c. 489.5 Ma to 485.4 ± 1.9 Ma. The GSSP for the Cambrian–Ordovician boundary is at Green Point , western Newfoundland , Canada, and is dated at 485.4 Ma. It is defined by the appearance of the conodont Iapetognathus fluctivagus . Where these conodonts are not found the appearance of planktonic graptolites or

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1694-626: The continental flood basalts of the Kalkarindji large igneous province (LIP) began to erupt. These covered an area of > 2.1 × 10 km across northern, central and Western Australia regions of Gondwana making it one of the largest, as well as the earliest, LIPs of the Phanerozoic. The timing of the eruptions suggests they played a role in the early to middle Cambrian mass extinction . The terranes of Ganderia , East and West Avalonia , Carolinia and Meguma lay in polar regions during

1771-568: The trilobite Jujuyaspis borealis can be used. The boundary also corresponds with the peak of the largest positive variation in the δ C curve during the boundary time interval and with a global marine transgression. Major meteorite impact structures include: the early Cambrian (c. 535 Ma) Neugrund crater in the Gulf of Finland , Estonia, a complex meteorite crater about 20 km in diameter, with two inner ridges of about 7 km and 6 km diameter, and an outer ridge of 8 km that formed as

1848-567: The " Roof of the World ", which is still being formed by the collisions of the Indo-Australian and Eurasian tectonic plates . The Tibetan Plateau covers approximately 2,500,000 km (970,000 sq mi), at about 5,000 m (16,000 ft) above sea level. The plateau is sufficiently high to reverse the Hadley cell convection cycles and to drive the monsoons of India towards

1925-701: The 19 km diameter Glikson crater (c. 508 Ma) in Western Australia; the 5 km diameter Mizarai crater (500±10 Ma) in Lithuania; and the 3.2 km diameter Newporte structure (c. 500 Ma or slightly younger) in North Dakota , U.S.A. Reconstructing the position of the continents during the Cambrian is based on palaeomagnetic , palaeobiogeographic , tectonic , geological and palaeoclimatic data. However, these have different levels of uncertainty and can produce contradictory locations for

2002-688: The Altiplano lies within Bolivian and Peruvian territory while its southern parts lie in Chile. The Altiplano plateau hosts several cities like Puno, Oruro, El Alto and La Paz the administrative seat of Bolivia. Northeastern Altiplano is more humid than the Southwestern, the latter of which hosts several salares , or salt flats, due to its aridity. At the Bolivia-Peru border lies Lake Titicaca ,

2079-550: The Amazonia region of Gondwana with a narrow Iapetus Ocean that only began to open once Gondwana was fully assembled c. 520 Ma. Those not in favour of the existence of Pannotia show the Iapetus opening during the Late Neoproterozoic, with up to c. 6,500 km (c. 4038 miles) between Laurentia and West Gondwana at the beginning of the Cambrian. Of the smaller continents, Baltica lay between Laurentia and Gondwana,

2156-516: The Cambrian and Early Ordovician. Gondwana was a massive continent, three times the size of any of the other Cambrian continents. Its continental land area extended from the south pole to north of the equator. Around it were extensive shallow seas and numerous smaller land areas. The cratons that formed Gondwana came together during the Neoproterozoic to early Cambrian. A narrow ocean separated Amazonia from Gondwana until c. 530 Ma and

2233-540: The Cambrian, Laurentia lay across or close to the equator.  It drifted south and rotated c. 20° anticlockwise during the middle Cambrian, before drifting north again in the late Cambrian. After the Late Neoproterozoic (or mid-Cambrian) rifting of Laurentia from Gondwana and the subsequent opening of the Iapetus Ocean, Laurentia was largely surrounded by passive margins with much of the continent covered by shallow seas. As Laurentia separated from Gondwana,

2310-738: The Cambrian, lasting from c. 509 Ma to c. 497 Ma, and roughly identical to the middle Cambrian in older literature [1] . It is divided into three stages: the Wuliuan c. 509 Ma to 504.5 Ma; the Drumian c. 504.5 Ma to c. 500.5 Ma; and the Guzhangian c. 500.5 Ma to c. 497 Ma. The name replaces Cambrian Series 3 and was ratified by the IUGS in 2018. It is named after the Miaoling Mountains in southeastern Guizhou Province , South China, where

2387-502: The Canadian Shield, the Adirondack Mountains of New York State might also be considered an extension of the Laurentian Upland. The Laurentian Upland is primarily made up of ancient Precambrian igneous , metamorphic , and sedimentary rock. With the exception of the river valleys and lacustrine basins, it is a rolling to mountainous peneplain that ranges from 800 to 1400 feet above sea level. The Superior Upland

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2464-544: The Ediacaran Timanian Orogeny was coming to an end. In this region the early to middle Cambrian was a time of non-deposition and followed by late Cambrian rifting and sedimentation. Its southeastern margin was also a convergent boundary , with the accretion of island arcs and microcontinents to the craton, although the details are unclear. Siberia began the Cambrian close to western Gondwana and north of Baltica. It drifted northwestwards to close to

2541-584: The GSSP marking its base is found. This is defined by the first appearance of the oryctocephalid trilobite Oryctocephalus indicus . Secondary markers for the base of the Miaolingian include the appearance of many acritarchs forms, a global marine transgression , and the disappearance of the polymerid trilobites, Bathynotus or Ovatoryctocara. Unlike the Terreneuvian and Series 2, all the stages of

2618-609: The ICS ratify rock units based on a Global Boundary Stratotype Section and Point (GSSP) from a single formation (a stratotype ) identifying the lower boundary of the unit. Currently the boundaries of the Cambrian System, three series and six stages are defined by global stratotype sections and points. The lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites . The recognition of small shelly fossils before

2695-475: The Iapetus and from Gondwana by the Ran Ocean. It was composed of two continents, Fennoscandia and Sarmatia , separated by shallow seas. The sediments deposited in these unconformably overlay Precambrian basement rocks. The lack of coarse-grained sediments indicates low lying topography across the centre of the craton. Along Baltica's northeastern margin subduction and arc magmatism associated with

2772-419: The Miaolingian are defined by GSSPs . The olenellids , eodiscids , and most redlichiids trilobites went extinct at the boundary between Series 2 and the Miaolingian. This is considered the oldest mass extinction of trilobites. The Furongian , c. 497 Ma to 485.4 ± 1.9 Ma, is the fourth and uppermost series/epoch of the Cambrian. The name was ratified by the IUGS in 2003 and replaces Cambrian Series 4 and

2849-423: The Neoproterozoic, extended around much of Gondwana's margins, from northwest Africa southwards round South America, South Africa , East Antarctica , and the eastern edge of West Australia. Shorter subduction zones existed north of Arabia and India. The Famatinian continental arc stretched from central Peru in the north to central Argentina in the south. Subduction beneath this proto- Andean margin began by

2926-721: The North Rim of the Grand Canyon is at an elevation of about 2,450 m (8,040 ft) above sea level , and the South Rim of the Grand Canyon is about 2,150 m (7,050 ft) above sea level. At its deepest, the Colorado River is about 1,830 m (6,000 ft) below the level of the North Rim. Another high-altitude plateau in North America is the Mexican Plateau . With an area of 601,882 km (232,388 sq mi) and average height of 1,825 metres, it

3003-457: The Ran Ocean (an arm of the Iapetus) opening between it and Gondwana. Siberia lay close to the western margin of Gondwana and to the north of Baltica. Annamia and South China formed a single continent situated off north central Gondwana. The location of North China is unclear. It may have lain along the northeast Indian sector of Gondwana or already have been a separate continent. During

3080-552: The Sedgwick's "Upper Cambrian", claiming all fossilised strata for "his" Silurian series. Matters were complicated further when, in 1852, fieldwork carried out by Sedgwick and others revealed an unconformity within the Silurian, with a clear difference in fauna between the two. This allowed Sedgwick to now claim a large section of the Silurian for "his" Cambrian and gave the Cambrian an identifiable fossil record. The dispute between

3157-534: The Shield give the appearance of mountains 500–800 meters high; looking across the plateau, the relief is more moderate and subdued. These scarps mark the dramatic southern edge of this Upland region, of which Mont Raoul Blanchard is the highest peak. Although the other limits are less well defined, this Laurentian Region in Quebec may be considered to extend 100–200 km northward from the scarps and to stretch from

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3234-791: The Welsh name for Wales, where rocks of this age were first studied. It was named by Adam Sedgwick in 1835, who divided it into three groups; the Lower, Middle, and Upper. He defined the boundary between the Cambrian and the overlying Silurian, together with Roderick Murchison , in their joint paper " On the Silurian and Cambrian Systems, Exhibiting the Order in which the Older Sedimentary Strata Succeed each other in England and Wales ". This early agreement did not last. Due to

3311-469: The beginning of the Ordovician Period 485.4 Ma. Most of the continents lay in the southern hemisphere surrounded by the vast Panthalassa Ocean . The assembly of Gondwana during the Ediacaran and early Cambrian led to the development of new convergent plate boundaries and continental-margin arc magmatism along its margins that helped drive up global temperatures. Laurentia lay across

3388-761: The crust. Tectonic plateaus are formed by tectonic plate movements which cause uplift, and are normally of a considerable size, and a fairly uniform altitude. Examples are the Deccan Plateau in India and the Meseta Central on the Iberian Peninsula . Plateaus can also be formed by the erosional processes of glaciers on mountain ranges, leaving them sitting between the mountain ranges. Water can also erode mountains and other landforms down into plateaus. Dissected plateaus are highly eroded plateaus cut by rivers and broken by deep narrow valleys. An example

3465-460: The depression of the region beneath an ancient sea took place after a long existence as dry land. The extent of the submergence and the area over which the Palaeozoic strata were deposited are unknown. Because of the renewed elevation without deformation, erosion in later periods has stripped off an undetermined amount of the covering strata. The valleys by which the uplands are here and there trenched to moderate depth appear to be, in part at least,

3542-416: The development of the Bainaimiao arc in the late Cambrian. To its south was a convergent margin with a southwest dipping subduction zone, beyond which lay the North Qinling terrane (now part of the Qinling Orogenic Belt ). South China and Annamia formed a single continent. Strike-slip movement between it and Gondwana accommodated its steady drift northwards from offshore the Indian sector of Gondwana to near

3619-402: The early Cambrian, and high-to-mid southern latitudes by the mid to late Cambrian. They are commonly shown as an island arc-transform fault system along the northwestern margin of Gondwana north of northwest Africa and Amazonia, which rifted from Gondwana during the Ordovician. However, some models show these terranes as part of a single independent microcontinent , Greater Avalonia, lying to

3696-501: The equator as the Ægir Ocean opened between it and Baltica. Much of the continent was covered by shallow seas with extensive archaeocyathan reefs . The then northern third of the continent (present day south; Siberia has rotated 180° since the Cambrian) adjacent to its convergent margin was mountainous. From the Late Neoproterozoic to the Ordovician, a series of island arcs accreted to Siberia's then northeastern margin, accompanied by extensive arc and back-arc volcanism. These now form

3773-428: The equator, separated from Gondwana by the opening Iapetus Ocean . The Cambrian was a time of greenhouse climate conditions, with high levels of atmospheric carbon dioxide and low levels of oxygen in the atmosphere and seas. Upwellings of anoxic deep ocean waters into shallow marine environments led to extinction events, whilst periods of raised oxygenation led to increased biodiversity . The Cambrian marked

3850-443: The first trilobites, and Ediacara biota substantially earlier, has led to calls for a more precisely defined base to the Cambrian Period. Despite the long recognition of its distinction from younger Ordovician rocks and older Precambrian rocks, it was not until 1994 that the Cambrian system/period was internationally ratified. After decades of careful consideration, a continuous sedimentary sequence at Fortune Head, Newfoundland

3927-466: The globe that corresponded to the base of the Cambrian. An early date of 570 Ma quickly gained favour, though the methods used to obtain this number are now considered to be unsuitable and inaccurate. A more precise analysis using modern radiometric dating yields a date of 538.8 ± 0.2 Ma. The ash horizon in Oman from which this date was recovered corresponds to a marked fall in the abundance of carbon-13 that correlates to equivalent excursions elsewhere in

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4004-506: The gods" in the native tongue of the Pemon , the Indigenous people who inhabit the Gran Sabana . Tepuis can be considered minute plateaus and tend to be found as isolated entities rather than in connected ranges, which makes them the host of a unique array of endemic plant and animal species. Some of the most outstanding tepuis are Neblina , Autana , Auyan and Mount Roraima . They are typically composed of sheer blocks of Precambrian quartz arenite sandstone that rise abruptly from

4081-416: The jungle, giving rise to spectacular natural scenery. Auyán-tepui is the source of Angel Falls , the world's tallest waterfall . The Colombian capital city of Bogota sits on an Andean plateau known as the Altiplano Cundiboyacense roughly the size of Switzerland. Averaging a height of 2,600 m (8,500 ft) above sea level, this northern Andean plateau is situated in the country's eastern range and

4158-430: The largest lake in South America. [REDACTED] Media related to Plateaus at Wikimedia Commons Cambrian The Cambrian ( / ˈ k æ m b r i . ə n , ˈ k eɪ m -/ KAM -bree-ən, KAYM - ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon . The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to

4235-431: The late Cambrian, triggering southeast-dipping subduction beneath the terrane itself and consequent closure of the marginal seaway. The terrane collided with Laurentia in the Early Ordovician. Towards the end of the early Cambrian, rifting along Laurentia's southeastern margin led to the separation of Cuyania (now part of Argentina) from the Ouachita embayment with a new ocean established that continued to widen through

4312-422: The late Cambrian. Along the northern margin of Gondwana, between northern Africa and the Armorican Terranes of southern Europe, the continental arc of the Cadomian Orogeny continued from the Neoproterozoic in response to the oblique subduction of the Iapetus Ocean. This subduction extended west along the Gondwanan margin and by c. 530 Ma may have evolved into a major transform fault system. At c. 511 Ma

4389-422: The lower boundary of the Cambrian at the base of the Tommotian Stage, characterized by diversification and global distribution of organisms with mineral skeletons and the appearance of the first Archaeocyath bioherms. The Terreneuvian is the lowermost series/ epoch of the Cambrian, lasting from 538.8 ± 0.2 Ma to c. 521 Ma. It is divided into two stages: the Fortunian stage, 538.8 ± 0.2 Ma to c. 529 Ma; and

4466-436: The major continents. This, together with the ongoing debate around the existence of the Neoproterozoic supercontinent of Pannotia , means that while most models agree the continents lay in the southern hemisphere, with the vast Panthalassa Ocean covering most of northern hemisphere, the exact distribution and timing of the movements of the Cambrian continents varies between models. Most models show Gondwana stretching from

4543-479: The most notable of which is the country's largest lake, Lake Taupō . The plateau stretches approximately 100 km east to west and 130 km north to south. The majority of the plateau is more than 600 metres above sea level. A tepui ( / ˈ t ɛ p w i / ), or tepuy ( Spanish: [teˈpuj] ), is a table-top mountain or mesa found in the Guiana Highlands of South America, especially in Venezuela and western Guyana . The word tepui means "house of

4620-442: The north-western United States is an example. They may be formed by upwelling of volcanic magma or extrusion of lava. The underlining mechanism in forming plateaus from upwelling starts when magma rises from the mantle , causing the ground to swell upward. In this way, large, flat areas of rock are uplifted to form a plateau. For plateaus formed by extrusion, the rock is built up from lava spreading outward from cracks and weak areas in

4697-415: The result of an impact of an asteroid 1 km in diameter; the 5 km diameter Gardnos crater (500±10 Ma) in Buskerud , Norway, where post-impact sediments indicate the impact occurred in a shallow marine environment with rock avalanches and debris flows occurring as the crater rim was breached not long after impact; the 24 km diameter Presqu'ile crater (500 Ma or younger) Quebec , Canada;

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4774-409: The scarcity of fossils, Sedgwick used rock types to identify Cambrian strata. He was also slow in publishing further work. The clear fossil record of the Silurian, however, allowed Murchison to correlate rocks of a similar age across Europe and Russia, and on these he published extensively. As increasing numbers of fossils were identified in older rocks, he extended the base of the Silurian downwards into

4851-413: The scarp face as it drops precipitously to the St Lawrence River. The more general Laurentian Upland Province may be considered to extend over a larger area of the Canadian Shield, into Northwestern Ontario and parts of Northern Minnesota , Wisconsin , Michigan , and New York State , and is recognized by the United States Geological Survey to include the Superior Upland . As a southern extension of

4928-403: The south of North China. To the south of these the Tarim microcontinent lay between Gondwana and Siberia. Its northern margin was passive for much of the Paleozoic, with thick sequences of platform carbonates and fluvial to marine sediments resting unconformably on Precambrian basement. Along its southeast margin was the Altyn Cambro–Ordovician accretionary complex, whilst to the southwest

5005-410: The south polar region to north of the equator. Early in the Cambrian, the south pole corresponded with the western South American sector and as Gondwana rotated anti-clockwise, by the middle of the Cambrian, the south pole lay in the northwest African region. Laurentia lay across the equator, separated from Gondwana by the Iapetus Ocean . Proponents of Pannotia have Laurentia and Baltica close to

5082-692: The south. The Deosai Plains in Pakistan are situated at an average elevation of 4,114 meters (13,497 ft) above sea level. They are considered to be the second highest plateaus in the world. Other major plateaus in Asia are: Najd on the Arabian Peninsula , elevation 762 to 1,525 m (2,500 to 5,003 ft), Armenian Highlands (≈400,000 km (150,000 sq mi), elevation 900–2,100 metres (3,000–6,900 ft)), Iranian Plateau (≈3,700,000 km (1,400,000 sq mi), elevation 300–1,500 metres (980–4,920 ft)), Anatolian Plateau , Mongolian Plateau (≈2,600,000 km (1,000,000 sq mi), elevation 1,000–1,500 metres (3,300–4,900 ft)), and

5159-416: The surrounding coastline through enormous glaciers . The polar ice cap is so massive that the echolocation measurements of ice thickness have shown that large areas are below sea level . But, as the ice melts, the land beneath will rebound through isostasy and ultimately rise above sea level. The largest and highest plateau in the world is the Tibetan Plateau , sometimes metaphorically described as

5236-493: The then north, Siberia was separated from the Central Mongolian terrane by the narrow and slowly opening Mongol-Okhotsk Ocean . The Central Mongolian terrane's northern margin with the Panthalassa was convergent, whilst its southern margin facing the Mongol-Okhotsk Ocean was passive. During the Cambrian, the terranes that would form Kazakhstania later in the Paleozoic were a series of island arc and accretionary complexes that lay along an intra-oceanic convergent plate margin to

5313-400: The traditional "Upper Cambrian". The GSSP for the base of the Furongian is in the Wuling Mountains , in northwestern Hunan Province , China. It coincides with the first appearance of the agnostoid trilobite Glyptagnostus reticulatus , and is near the beginning of a large positive δ C isotopic excursion. The Furongian is divided into three stages: the Paibian , c. 497 Ma to c. 494 Ma, and

5390-664: The two geologists and their supporters, over the boundary between the Cambrian and Silurian, would extend beyond the life times of both Sedgwick and Murchison. It was not resolved until 1879, when Charles Lapworth proposed the disputed strata belong to its own system, which he named the Ordovician. The term Cambrian for the oldest period of the Paleozoic was officially agreed in 1960, at the 21st International Geological Congress . It only includes Sedgwick's "Lower Cambrian series", but its base has been extended into much older rocks. Systems , series and stages can be defined globally or regionally. For global stratigraphic correlation,

5467-434: The unnamed Stage 2, c. 529 Ma to c. 521 Ma. The name Terreneuvian was ratified by the International Union of Geological Sciences (IUGS) in 2007, replacing the previous "Cambrian Series 1". The GSSP defining its base is at Fortune Head on the Burin Peninsula, eastern Newfoundland, Canada (see Ediacaran - Cambrian boundary above). The Terreneuvian is the only series in the Cambrian to contain no trilobite fossils. Its lower part

5544-466: The upland as a whole is gently rolling with the inter-streams surfaces being plateau-like in their evenness. Here they have elevations of 1,400 to 2,300 feet (700 m) in their higher areas, such as the Misquah Hills and Huron Mountains . In this province, we find a part of those ancient mountains regions that were initiated by crustal deformation and then reduced by a long continued erosion to

5621-415: The west of Baltica and aligned with its eastern ( Timanide ) margin, with the Iapetus to the north and the Ran Ocean to the south. During the Cambrian, Baltica rotated more than 60° anti-clockwise and began to drift northwards. This rotation was accommodated by major strike-slip movements in the Ran Ocean between it and Gondwana. Baltica lay at mid-to-high southerly latitudes, separated from Laurentia by

5698-651: The work of streams that have been superposed upon the peneplain through the now removed cover of stratified rocks. Glaciation has strongly scoured away the deeply weathered soils that presumably existed here in preglacial time. It left behind firm and rugged ledges in the low hills and swells of the ground and spread an irregular drift cover over the lower parts, whereby the drainage is generally disordered being deposited in lakes and swamps and elsewhere rushing down rocky rapids. 46°26′N 74°59′W  /  46.433°N 74.983°W  / 46.433; -74.983 Plateau In geology and physical geography ,

5775-556: The world, and to the disappearance of distinctive Ediacaran fossils ( Namacalathus , Cloudina ). Nevertheless, there are arguments that the dated horizon in Oman does not correspond to the Ediacaran-Cambrian boundary, but represents a facies change from marine to evaporite-dominated strata – which would mean that dates from other sections, ranging from 544 to 542 Ma, are more suitable. *Most Russian paleontologists define

5852-605: Was once called Gallayat Plateaus, rising 3,300 ft above sea level. Another very large plateau is the icy Antarctic Plateau , which is sometimes referred to as the Polar Plateau or King Haakon VII Plateau, home to the geographic South Pole and the Amundsen–Scott South Pole Station , which covers most of East Antarctica where there are no known mountains but rather 3,000 m (9,800 ft) high of superficial ice and which spreads very slowly toward

5929-509: Was settled upon as a formal base of the Cambrian Period, which was to be correlated worldwide by the earliest appearance of Treptichnus pedum . Discovery of this fossil a few metres below the GSSP led to the refinement of this statement, and it is the T. pedum ichnofossil assemblage that is now formally used to correlate the base of the Cambrian. This formal designation allowed radiometric dates to be obtained from samples across

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