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86-522: The major structural components of the Junggar Basin divided into six parts: In Precambrian section was made up of felsic - intermediate granite with the inclusion of greenstones and ophiolites , where the Paleozoic section consists of mainly potassium- and sodium-deficient extrusive rocks . The basalts in the basement which indicated trapped late Paleozoic oceanic crust that came from

172-708: A supereon , but this is also an informal term, not defined by the ICS in its chronostratigraphic guide. Eozoic (from eo- "earliest") was a synonym for pre-Cambrian , or more specifically Archean . A specific date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks (Archean Eon) from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia . Probable fossils 100 million years older have been found in

258-465: 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

344-735: A possible 2450 Ma red alga from the Kola Peninsula , 1650 Ma carbonaceous biosignatures in north China, the 1600 Ma Rafatazmia , and a possible 1047 Ma Bangiomorpha red alga from the Canadian Arctic. The earliest fossils widely accepted as complex multicellular organisms date from the Ediacaran Period. A very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota . Hard-shelled creatures appeared toward

430-638: 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

516-517: 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

602-558: 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

688-455: 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 ,

774-441: 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

860-694: Is dominant in Karamay , Baikouquan, Urho, Dushanzi , and Qigu . The oil and gas fields can be found on Tertiary Dushanzi sandstone. Besides, gas fields are found in the Karamay as well as the inland region of the basin. Besides, Tian Shan Foredeep in the southern Junggar Basin (including Urumqi ) is also available for the petroleum resources. The petroleum there were formed due to rapid subsidence, regional ductile with mobile intrusion , and cross-cutting on anticlines by orogenic activity (probably in Neogene) from

946-664: Is known to occur during the RNA replication of extant coronaviruses . Evidence of the details of plate motions and other tectonic activity in the Precambrian is difficult to interpret. It is generally believed that small proto-continents existed before 4280 Ma, and that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia , broke up around 750 Ma. A number of glacial periods have been identified going as far back as

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1032-613: Is the earliest part of Earth's history , set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian , the first period of the Phanerozoic Eon , which is named after Cambria , the Latinized name for Wales , where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean , Archean , Proterozoic ) of

1118-521: Is thought that the Earth coalesced from material in orbit around the Sun at roughly 4,543 Ma, and may have been struck by another planet called Theia shortly after it formed, splitting off material that formed the Moon (see Giant-impact hypothesis ). A stable crust was apparently in place by 4,433 Ma, since zircon crystals from Western Australia have been dated at 4,404 ± 8 Ma. The term "Precambrian"

1204-488: Is thought to have formed about 1300-900 Ma, to have included most or all of Earth's continents and to have broken up into eight continents around 750–600 million years ago. 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

1290-731: Is used by geologists and paleontologists for general discussions not requiring a more specific eon name. However, both the United States Geological Survey and the International Commission on Stratigraphy regard the term as informal. Because the span of time falling under the Precambrian consists of three eons (the Hadean , the Archean , and the Proterozoic ), it is sometimes described as

1376-649: 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

1462-587: 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

1548-534: The Huronian epoch, roughly 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a " Snowball Earth ". The atmosphere of the early Earth is not well understood. Most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and

1634-553: 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

1720-626: 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

1806-522: The geologic time scale . It spans from the formation of Earth about 4.6 billion years ago ( Ga ) to the beginning of the Cambrian Period, about 538.8 million years ago ( Ma ), when hard-shelled creatures first appeared in abundance. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history , and what is known has largely been discovered from

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1892-482: The oxygen catastrophe . At first, oxygen would have quickly combined with other elements in Earth's crust, primarily iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, and the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides. A terminology has evolved covering

1978-568: 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

2064-701: 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

2150-401: The 1960s onwards. The Precambrian fossil record is poorer than that of the succeeding Phanerozoic , and fossils from the Precambrian (e.g. stromatolites ) are of limited biostratigraphic use. This is because many Precambrian rocks have been heavily metamorphosed , obscuring their origins, while others have been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata. It

2236-550: 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,

2322-516: 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

2408-540: 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,

2494-738: 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

2580-544: 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

2666-584: 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

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2752-560: 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

2838-475: 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

2924-510: The Junggar Basin was reactivated. At the same time, there was rapid uplift of Tian Shan since Himalayan orogeny formed by the collision between Indo-plate and Eurasian Plate . This developed an alluvial-rich delta system around shallow lakes with the clastic sediments influx from uplifted Tian Shan and the northern part of the basin. Junggar Basin contains the third-largest petroleum reservoirs in China. About two-thirds of oil can be found in

3010-585: The Karamay-Urho monocline area. There was formed in Carboniferous deep-sea sedimentary rocks and lake sedimentary layers from Permian to Tertiary. For Carboniferous oil and gas deposits in this area, they were moved upward and accumulated in the Permian period and Mesozoic era sandstones . Then, the layers altered as the structural trap locations by tectonic activities in the later stage. Petroleum

3096-419: 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

3182-423: 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

3268-457: 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

3354-552: 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

3440-697: The Tian Shan. Part of the oil-bearing sedimentary rocks was deposited in the salty oxygen-deficient lake environment during Permian. The crude oil in this sedimentary rocks formed by remains of algae and humus. Bituminous coal was found in Tian Shan Foredeep. It was deposited in the lake or swamp environment in the Early to Middle Jurassic periods. For example, Badaowan, Sangonghe, and Xishanyao Formation. About 18 gigatonnes of coal can be recovered in Tian Shan Foredeep. Apart from Tian Shan Foredeep,

3526-791: 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

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3612-633: The coal can be found in the base of alluvial fan and nearby the margin of lakes in the eastern and western margin of Junggar Basin. Ore deposits in the Junggar Basin were mainly formed in the Paleozoic era which was related to tectonic development. The followings are the available ore deposits in Junggar Basin: Precambrian The Precambrian ( / p r i ˈ k æ m b r i . ə n , - ˈ k eɪ m -/ pree- KAM -bree-ən, -⁠KAYM- ; or Pre-Cambrian , sometimes abbreviated pC , or Cryptozoic )

3698-772: The converged plates. This revealed the partial melting of the oceanic crust. This also marked as the last subduction event following the post-collisional stage in Late-Carboniferous. Besides, Such intrusive rocks demonstrated that this was the last melting episode of oceanic crust. As part of the Eurasian plate started to combine continental crusts for the three plates, to consolidate them as another modern stable continental block . The mafic-ultramafic igneous rocks formed due to underplating with crustal stretching during Carboniferous to Permian. The magma underplating during Carboniferous to Permian (330-250 Ma) period heated up

3784-401: The current scheme based upon numerical ages. Such a system could rely on events in the stratigraphic record and be demarcated by GSSPs . The Precambrian could be divided into five "natural" eons, characterized as follows: The movement of Earth's plates has caused the formation and break-up of continents over time, including occasional formation of a supercontinent containing most or all of

3870-469: The delta formed along the margin of the basin. Also, the deeper lake was at the basin centre during Lower Cretaceous . Afterward, the southward lake depression leading the basin centre shift to the south in the Upper Cretaceous period. In Paleogene, braid-delta developed over the basin where sediments entered from the mountains of the surrounding basin. Starting from Neogene , the thrust fault in

3956-663: 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

4042-461: 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

4128-453: The early years of the Earth's existence, as radiometric dating has allowed absolute dates to be assigned to specific formations and features. The Precambrian is divided into three eons: the Hadean (4567.3–4031 Ma), Archean (4031-2500 Ma) and Proterozoic (2500-538.8 Ma). See Timetable of the Precambrian . It has been proposed that the Precambrian should be divided into eons and eras that reflect stages of planetary evolution, rather than

4214-472: The effect of continental monsoonal climate. From middle to late Jurassic, the climate shifted as a seasonal arid climate that initiated from the northeast and then widespread to the whole basin. This is because the Pangea started to break apart that halted the effect from the mega-monsoon system. Therefore, the basin became affected by westerlies . The westerlies contained the lesser moisture that has come from

4300-705: The end of that time span, marking the beginning of the Phanerozoic Eon. By the middle of the following Cambrian Period, a very diverse fauna is recorded in the Burgess Shale , including some which may represent stem groups of modern taxa. The increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Tracks from an animal with leg-like appendages have been found in what

4386-545: The end of the preceding Ediacaran period 538.8 Ma (million years ago) to 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

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4472-557: 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

4558-428: 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

4644-443: 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

4730-482: The fluvial and lake depositional environment. The climate in the late Permian showed the fluctuation between dry- or wet-dominated climate. The pieces of evidence included the presence of both organic beds and red beds. In the early Triassic, reddish sedimentary rocks formed that indicated the dominance of semi-arid climate . During Late Triassic-Early Jurassic, the Junggar basin was in a warm and wet climate due to

4816-517: 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

4902-466: The influence of Variscan orogeny , Early Permian marine facies changed into the terrestrial environment during Late Permian. This is because orogenic compression and crustal thickening resulted in higher sedimentation and withdrawn of the sea. At that time, widespread uplift occurred with subsidence formed a graben at first. Then, the area gradually became a mountain-trapped peripheral foreland basin due to high-temperature and relaxing subsidence from

4988-541: The landmass. The earliest known supercontinent was Vaalbara . It formed from proto-continents and was a supercontinent 3.636 billion years ago. Vaalbara broke up c. 2.845–2.803 Ga ago. The supercontinent Kenorland was formed c. 2.72 Ga ago and then broke sometime after 2.45–2.1 Ga into the proto-continent cratons called Laurentia , Baltica , Yilgarn craton and Kalahari . The supercontinent Columbia , or Nuna, formed 2.1–1.8 billion years ago and broke up about 1.3–1.2 billion years ago. The supercontinent Rodinia

5074-553: 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

5160-613: 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

5246-422: 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

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5332-402: The lower crust and thus the crust got hotter. The following cooling crustal episode led to part of the mountain belt sink by thermal subsidence , which ended up forming the Junggar Basin. Another magma underplating event occurred in the Mesozoic era. This was forming heterogenic silica-rich igneous rocks due to the partial melting of numerous oceanic crusts contaminated with mantle wedge . With

5418-436: 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

5504-1219: The mantle. The sedimentary facies started to be dominant in Permian. The layers continuously deposited fluvial and lacustrine facies until the present day, mostly containing conglomerate, sandstone, siltstone, and mudstone. Major stratigraphic units in the Junggar basin from Carboniferous are shown in ascending order in the following table: (Dark-brown mudstone, siltstone & sandstone with thin conglomerate & limestone) (Thickly-bed shale interbedded with sandstone & calcite grains) (Mudstone, sandstone) (Shale with ostracods, dolomitic sandstone) (Orange-red sandy mudstone) (quartzose sandstone & mudstone) (Green shale with marls) (medium-grained sandstone & mudstone) (Orange-red sandy shale) (Mudstone at upper unit but conglomerate at lower unit) (Sandy shale, siltstone, sandstone & conglomerate, some calcite nodules) (Sandstone with marls, but mudstone and shale dominated in southern part. Conglomerate with cross-bedding structure at lowest unit. Presence of gypsum and fossil fish.) (Sandy mudstone to sandstone, with calcite materials and dinosaur fossils.) (Presence of mudcracks in lower unit, coal red beds and dinosaur tracks at

5590-417: The northwest since the marine areas gradually minimized to the recent Caspian Sea . With the continuous uplift along the Tian Shan , the orographic effect around the basin intensifies the rain-shadow effect . The prominent rain-shadow effect results in a warmer seasonal arid climate in the basin. At the same time, the lakes in the basin had higher salinity and lower sedimentation influx. Xinjiang paleocraton

5676-399: The presence of stromatolite) (Grey mudstone, sandstone, conglomerate) (Organe-red conglomerate, and fossil plant-bearing sandstone & volcanic flows) (pyroclastic turbidite, locally thinly-bedded limestone) (Conglomerate, sandstone, calcareous shale) (Grey tuff with regional limestone included brachiopod fossils, and pillow lava) Throughout Mesozoic, Junggar Basin was mainly in

5762-402: The regional extension. Some also suggested this landform caused by the combined effect of shearing and extension or thrusting from crustal shortening. Starting from Permian, Junggar Basin was formed to initiate the foreland basin cycle. There presented extensional shearing and continuous deposition of non-marine foreland basin-fill till Triassic . Since the level of the trapped lake in the basin

5848-415: 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;

5934-526: The same area. However, there is evidence that life could have evolved over 4.280 billion years ago. There is a fairly solid record of bacterial life throughout the remainder (Proterozoic Eon) of the Precambrian. Complex multicellular organisms may have appeared as early as 2100 Ma. However, the interpretation of ancient fossils is problematic, and "... some definitions of multicellularity encompass everything from simple bacterial colonies to badgers." Other possible early complex multicellular organisms include

6020-409: 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

6106-403: 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

6192-472: 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

6278-693: 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

6364-547: The third rifting event during lower-mid Devonian . Eventually, the Junggar ocean and Kulumudi Ocean moved towards the north and undergone the subduction from upper Devonian to Late- Carboniferous . At the same time, several volcanic arcs were developed during subduction. Three plates (Tarim, Kazakhstan, and Siberian) converged together to form a trapped ocean that surrounded volcanic arc and orogens in Mid-Carboniferous. Alkali-rich granites with gold deposits intruded

6450-901: The top unit. Petrified woods were preserved.) (Conglomerates in southern and eastern part. Massive mudstone beds and soft-sediment deformation in northwest. Widespread coals were present. Petrified woods and plant fossils were preserved.) (Yellow silty shale with some coal) (Yellow conglomerate, sandstone, mudstone & shale) (Greyish-green sandstone & mudstone) (Conglomerate, sandstone with graded bedding) (Red conglomerate, sandstone & mudstone) (orange-red conglomerate with red mudstone) (siltstone, sandstone & conglomerate) (Greyish-green mudstone with sandstone, with some purple-red conglomerate and plant fossils) (orange-red alluvial sandstone & conglomerate, with shale) (Greyish-green feldspathic sandstone & mudstone, some fossiliferous limestone and black oil-shale) (orange-red clastic sedimentary rocks) (limestone with

6536-577: 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

6622-664: 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,

6708-569: 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

6794-415: 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

6880-505: 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

6966-482: Was lacking in free oxygen . There is, however, evidence that an oxygen-rich atmosphere existed since the early Archean. At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism . This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis , sometimes called

7052-852: Was mud 551 million years ago. The RNA world hypothesis asserts that RNA evolved before coded proteins and DNA genomes. During the Hadean Eon (4,567–4,031 Ma) abundant geothermal microenvironments were present that may have had the potential to support the synthesis and replication of RNA and thus possibly the evolution of a primitive life form. It was shown that porous rock systems comprising heated air-water interfaces could allow ribozyme - catalyzed RNA replication of sense and antisense strands that could be followed by strand-dissociation, thus enabling combined synthesis, release and folding of active ribozymes. This primitive RNA replicative system also may have been able to undergo template strand switching during replication ( genetic recombination ) as

7138-557: Was over passive margin . Another rifting event established the Mayilashan ocean basin and back-arc basin in east Junggar during Silurian . However, the compressional environment restricted the two landforms so that they ended up shut and folded in the late Silurian. This eventually led to the convergence of Tarim , Kazakhstan and Siberian paleo-plates. They were from the original Xinjiang paleocraton that puzzled each other again. Junggar Ocean and Kulumudi Ocean were produced from

7224-580: Was pulled apart for a continental rifting episode to form extensional basins in Late Cambrian . The continuous divergence of the continental crust during late Cambrian to Ordovician shaped the West Junggar Ocean. The West Junggar Ocean presented as the present Tangbale and Honguleleng ophiolites from intra-plate volcanism, and then this volcanism shut in mid-upper Ordovician. The Ordovician first ocean basin indicated that eastern Junggar

7310-470: Was rising, finer deposits covered widespread the basin with denudation . This also marked as the end of the foreland basin cycle. From Jurassic to Palaeogene , the Junggar Basin undergone intra-continental depression. There was covered in braided delta with few lakes and increasing subsidence rate towards the south from 20 to 120 m/Ma during Jurassic. The collision of the Lhasa block from the south resulted that

7396-444: 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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