Paleoproterozoic Era ( /pælioʊˌproʊtərəˈzoʊɪk-/;), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's geological history. It was during this era that the continents first stabilized.
Paleontological evidence suggests that the Earth's rotational rate during this era resulted in 20-hour days ~1.8 billion years ago, implying a total of ~450 days per year.
2500–1600 million years ago
Before the enormous increase in atmospheric oxygen, almost all existing lifeforms were Anaerobic_organism, i.e., their metabolism was based upon a form of cellular respiration that did not require oxygen. Indeed, free oxygen in large amounts is toxic to most anaerobic organisms. Consequently, the majority of the anaerobic lifeforms on Earth died when the atmospheric free-oxygen levels soared. The only lifeforms that survived were either those resistant to the oxidizing and poisonous effects of oxygen, or those sequestered in oxygen-free environments. The sudden increase of atmospheric free oxygen and the ensuing extinction of the vulnerable lifeforms (an event called, among numerous other similarly suggestive titles, the Oxygen Holocaust or Oxygen Catastrophe) is widely considered to be the first of the most significant mass extinctions in the history of the Earth.
Many crown node eukaryotes (from which the modern-day eukaryotic lineages would have arisen)—or the divergences that imply them between various groups of eukaryotes—have been ostensibly dated to around the time of the Paleoproterozoic era. However, these conclusions (as is the case in virtually any contemporaneously "hot" areas of biological study and research) are likely to be readjusted—if not outright abandoned—as more data become available, and should not be considered conclusive proof by any means. Nevertheless, given the number of and the peer respect assigned to many of the authors of these studies (and related analyses corroborating the validity of the methodologies used by those studies ...even though those very analyses are themselves also sometimes called into question), the final revisions will likely place the emergence of the oldest eukaryotic divergences around this period of time.
During this era, the earliest global-scale continent-continent collision belts developed.
These continent and mountain building events are represented by the 2.1–2.0 Ga Trans-Amazonian and Eburnean orogens in South America and West Africa; the ~2.0 Ga Limpopo Belt in southern Africa; the 1.9–1.8 Ga Trans-Hudson, Penokean, Taltson–Thelon, Wopmay, Ungava and Torngat orogens in North America, the 1.9–1.8 Ga Nagssugtoqidain Orogen in Greenland; the 1.9–1.8 Ga Kola–Karelia, Svecofennian, Volhyn-Central Russian, and Pachelma orogens in Baltica (Eastern Europe); the 1.9–1.8 Ga Akitkan Orogen in Siberia; the ~1.95 Ga Khondalite Belt and ~1.85 Ga Trans-North China Orogen in North China.
These continental collision belts are interpreted as having resulted from one or more 2.0–1.8 Ga global-scale collision events that then led to the assembly of a Proterozoic supercontinent named Columbia or Nuna.
Amelia Creek crater is an impact structure (or astrobleme), the eroded remnant of a former impact crater, located in the Davenport Range, Northern Territory, Australia. It lies within a low range of Paleoproterozoic sedimentary and volcanic rocks, which are extensively folded and faulted, thus making an eroded impact crater difficult to recognize. It was only discovered by the identification of shatter cones near its centre. The central shatter cone locality is surrounded by a 20 by 12 km (12.4 by 7.5 mi) area of anomalous deformation, the asymmetry being possibly related to very oblique impact, but may be at least partly due to the pre-existing structural complexity of the rocks. This deformed zone gives the best estimate for the original size of the crater. Impact took place after folding of the Paleoproterozoic rocks but before deposition of Neoproterozoic and Cambrian rocks which overlie them, thus constraining the impact event to the interval between about 1660 and 600 Ma.Belomorian Province
The Belomorian Province (also known as Belomorian Terrane and Belomorian Domain) is an area of the Fennoscandian Shield spanning the parts of the Republic of Karelia and Murmansk Oblast in Russia. The province is named after the russian name of the White Sea. The main rock types are orthogneiss (derived from the Tonalite-Trondhjemite-Granodiorite association), greenstone and paragneiss. Although these rocks formed in the Mesoarchean and Neoarchean, they were disturbed by tectonic movements and heat 1900–1800 million years ago in the Paleoproterozoic. Located between the Kola and Karelian domains the collision of these two blocks would have caused the disturbance. According to one view the Belomorian Province could just be a more metamorphosed part of the Karelian Province to the west.Eburnean orogeny
The Eburnean orogeny, or Eburnean cycle was a series of tectonic, metamorphic and plutonic events in what is now West Africa during the Paleoproterozoic era about 2200–2000 million years ago.
During this period the Birimian domain in West Africa was established and structured.Eburnian faults are found in the Eglab shield to the north of the West African craton and in the Man Shield to the south of the craton.
There is evidence of three major Eburnean magmatic events in the Eglab shield.
Between 2210 and 2180 Ma, a metamorphosed batholith was formed in the Lower Reguibat Complex (LRC).
Around 2090 Ma, a syntectonic trondhjemitic pluton intruded into the Archaean reelects of the Chegga series. Around 2070 Ma an asthenospheric upwelling released a large volume of post-orogenic magmas.
Eburnian trends within the Eglab shield were repeatedly reactivated from the Neoproterozoic to the Mesozoic.Flin Flon greenstone belt
The Flin Flon greenstone belt, also referred to as the Flin Flon – Snow Lake greenstone belt, is a Precambrian greenstone belt located in the central area of Manitoba and east-central Saskatchewan, Canada (near Flin Flon). It lies in the central portion of the Trans-Hudson orogeny and was formed by arc volcanism during the Paleoproterozoic period. The Flin Flon – Snow Lake greenstone belt is 250 km long by 75 km wide and is exposed just north of McClarty Lake. The belt is bounded by metasedimentary gneisses and metavolcanics of the Kisseynew Domain to the north and extends to the south where it is unconformably overlain by Ordovician age dolomite.Gothian orogeny
The Gothian orogeny (Swedish: Gotiska orogenesen) or Kongsberg orogeny was an orogeny in western Fennoscandia that occurred between 1750 and 1500 million years ago. It precedes the younger Sveconorwegian orogeny that has overprinted much of it. The Gothian orogeny formed along a subduction zone and resulted in the formation of calc-alkaline igneous rocks 1700 to 1550 million years ago, including some of the younger members of the Transscandinavian Igneous Belt.The deformation associated with the orogeny can be seen in metatonalite, paragneiss and biotite orthogneisses in southeast Norway. These rocks were all subject to amphibolite facies metamorphism.Huronian glaciation
The Huronian glaciation (or Makganyene glaciation) was a glaciation that extended from 2.4 billion years ago (Gya) to 2.1 Gya, during the Siderian and Rhyacian periods of the Paleoproterozoic era. The Huronian glaciation followed the Great Oxygenation Event (GOE), a time when increased atmospheric oxygen decreased atmospheric methane. The oxygen combined with the methane to form carbon dioxide and water, which do not retain heat as well as methane does.
It is the oldest and longest ice age, occurring at a time when only simple, unicellular life existed on Earth. This ice age led to a mass extinction on Earth.Lewisian complex
The Lewisian complex or Lewisian gneiss is a suite of Precambrian metamorphic rocks that outcrop in the northwestern part of Scotland, forming part of the Hebridean Terrane and the North Atlantic Craton. These rocks are of Archaean and Paleoproterozoic age, ranging from 3.0–1.7 Ga. They form the basement on which the Torridonian and Moine Supergroup sediments were deposited. The Lewisian consists mainly of granitic gneisses with a minor amount of supracrustal rocks. Rocks of the Lewisian complex were caught up in the Caledonian orogeny, appearing in the hanging walls of many of the thrust faults formed during the late stages of this tectonic event.Marathon Large Igneous Province
The Marathon Large Igneous Province is a Paleoproterozoic large igneous province along the southern Superior craton of Ontario, Canada, located around the northern margin of Lake Superior. It consists of three diabase dike swarms known as Marathon, Kapuskasing and Fort Frances. The Kapuskasing and Marathon dike swarms range in age from about 2,126 to 2,101 million years old while the Fort Frances dike swarm is between 2,076 and 2,067 million years old.A single, periodically active mantle plume was responsible for the creation of the Marathon Large Igneous Province due to the lack of apparent polar wander during the formation of the igneous province. The large magmatic event covers an area of at least 400,000 km2 (150,000 sq mi) and the entire large igneous province was constructed in 60 million years.Matachewan dike swarm
The Matachewan dike swarm is a large 2,500 to 2,450 million year old Paleoproterozoic dike swarm of Northern Ontario, Canada. It consists of basaltic dikes that were intruded in greenschist, granite-greenstone, and metamorphosed sedimentary terrains of the Superior craton of the Canadian Shield. With an area of 360,000 km2 (140,000 sq mi), the Matachewan dike swarm stands as a large igneous province.Mistassini dike swarm
The Mistassini dike swarm is a 2.5 billion year old Paleoproterozoic dike swarm of western Quebec, Canada. It consists of mafic dikes that were intruded in the Superior craton of the Canadian Shield. With an area of 100,000 km2 (39,000 sq mi), the Mistassini dike swarm stands as a large igneous province.Orosirian
The Orosirian Period ( ; Greek: ὀροσειρά, romanized: oroseirá, meaning "mountain range") is the third geologic period in the Paleoproterozoic Era and lasted from 2050 Mya to 1800 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
The later half of the period was an episode of intensive orogeny on virtually all continents.
Two of the largest known impact events on Earth occurred during the Orosirian. At the very beginning of the period, 2023 Mya, a large asteroid collision created the Vredefort impact structure. The event that created the Sudbury Basin structure occurred near the end of the period, 1850 Mya.
For the time period from about 2060 to 1780 Mya, an alternative period based on stratigraphy rather than chronometry, named the Columbian, was suggested in the geological timescale review 2012 edited by Gradstein et al., but as of February 2017, this has not yet been officially adopted by the IUGS.Proterozoic
The Proterozoic ( ) is a geological eon spanning the time from the appearance of oxygen in Earth's atmosphere to just before the proliferation of complex life (such as trilobites or corals) on the Earth. The name Proterozoic combines the two forms of ultimately Greek origin: protero- meaning "former, earlier", and -zoic, a suffix related to zoe "life". The Proterozoic Eon extended from 2500 mya to 541 mya (million years ago), and is the most recent part of the Precambrian "supereon." The Proterozoic is the longest eon of the Earth's geologic time scale and it is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic, Mesoproterozoic, and Neoproterozoic.The well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; several glaciations, which produced the hypothesized Snowball Earth during the Cryogenian Period in the late Neoproterozoic Era; and the Ediacaran Period (635 to 541 Ma) which is characterized by the evolution of abundant soft-bodied multicellular organisms and provides us with the first obvious fossil evidence of life on earth.Rhyacian
The Rhyacian Period ( ; Greek: ῥύαξ, romanized: rhýax, meaning "stream of lava") is the second geologic period in the Paleoproterozoic Era and lasted from 2300 Mya to 2050 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.The Bushveld Igneous Complex and other similar intrusions formed during this period.The Huronian (Makganyene) global glaciation began at the start of the Rhyacian and lasted 100 million years.For the time period from 2250 Ma to 2060 Ma, an alternative period based on stratigraphy rather than chronometry, named either the Jatulian or the Eukaryian, was suggested in the geological timescale review 2012 edited by Gradstein et al., but as of February 2017, this has not yet been officially adopted by the IUGS. The term Jatulian is, however, used in the regional stratigraphy of the Paleoproterozoic rocks of Fennoscandia.Siderian
The Siderian Period ( ; Greek: σίδηρος, romanized: sídēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from 2500 Ma to 2300 Ma (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
The laying down of the banded iron formations (BIFs) peaked early in this period. BIFs were formed as anaerobic cyanobacteria produced waste oxygen that combined with iron, forming magnetite (Fe3O4, an iron oxide). This process removed iron from the Earth's oceans, presumably turning greenish seas clear. Eventually, with no remaining iron in the oceans to serve as an oxygen sink, the process allowed the buildup of an oxygen-rich atmosphere. This second, follow-on event is known as the oxygen catastrophe, which, some geologists believe triggered the Huronian glaciation.Since the time period from 2420 Ma to 2250 Ma is well-defined by the lower edge of iron-deposition layers, an alternative period named the Oxygenian, based on stratigraphy instead of chronometry, was suggested in 2012 by Gradstein et al. in a geological timescale review but, as of February 2017, this has not yet been officially adopted by the IUGS.Statherian
The Statherian Period ( ; Greek: σταθερός (statherós), meaning "stable, firm") is the final geologic period in the Paleoproterozoic Era and lasted from 1800 Mya to 1600 Mya (million years ago). Instead of being based on stratigraphy, these dates are defined chronometrically.
The period was characterized on most continents by either new platforms or final cratonization of fold belts.
By the beginning of the Statherian, the supercontinent Columbia had assembled.Trans-Hudson orogeny
The Trans-Hudson orogeny or Trans-Hudsonian orogeny was the major mountain building event (orogeny) that formed the Precambrian Canadian Shield, the North American Craton (also called Laurentia), and the forging of the initial North American continent. It gave rise to the Trans-Hudson orogen (THO), or Trans-Hudson Orogen Transect (THOT), (also referred to as the Trans-Hudsonian Suture Zone (THSZ) or Trans-Hudson suture) which is the largest Paleoproterozoic orogenic belt in the world. It consists of a network of belts that were formed by Proterozoic crustal accretion and the collision of pre-existing Archean continents. The event occurred 2.0-1.8 billion years ago.
The Trans-Hudson orogen sutured together the Hearne-Rae, Superior, and Wyoming cratons to form the cratonic core of North America in a network of Paleoproterozoic orogenic belts. These orogenic belts include the margins of at least nine independent microcontinents that were themselves sections of at least three former major supercontinents, including Laurasia, Pangaea and Kenorland (ca. 2.7 Ga), and contain parts of some of the oldest cratonic continental crust on Earth. These old cratonic blocks, along with accreted island arc terranes and intraoceanic deposits from earlier Proterozoic and Mesozoic oceans and seaways, were sutured together in the Trans-Hudson Orogen (THO) and resulted in extensive folding and thrust faulting along with metamorphism and hundreds of huge granitic intrusions.The THO is a right-angled suture zone that extends eastward from Saskatchewan through collisional belts in the Churchill province, through northern Quebec, parts of Labrador and Baffin Island, and all the way to Greenland as the Rinkian belt and Nagssugtodidian Orogen. Westward it goes across Hudson Bay through Saskatchewan and then extends 90 degrees south through eastern Montana and the western Dakotas, downward through eastern Wyoming and western Nebraska, and is then cut off by the Cheyenne belt - the northern edge of the Yavapai province (see Trans-Hudson Orogen map and the THOT Transect map. To the south, the orogen contributed to the subsurface Phanerozoic strata in Montana and the Dakotas that created the Great Plains.Ungava magmatic event
The Ungava magmatic event was a widespread magmatic event that began about 2.22 billion years ago during the Proterozoic Eon.Vredefort crater
The Vredefort crater is the largest verified impact crater on Earth. More than 300 kilometres (190 mi) across when it was formed, what remains of it is in the present-day Free State province of South Africa. It is named after the town of Vredefort, which is near its centre. Although the crater itself has long since been worn away, the remaining geological structures at its centre are known as the Vredefort Dome or Vredefort impact structure. The crater is estimated to be 2.023 billion years old (± 4 million years), with impact being in the Paleoproterozoic Era. It is the second-oldest known crater on Earth.
In 2005, the Vredefort Dome was added to the list of UNESCO World Heritage sites for its geologic interest.Winagami sill complex
The Winagami sill complex, also called the Winagami sills, is a Paleoproterozoic large igneous province of northwestern Alberta, Canada. It consists of a series of related sills that were formed between 1.89 and 1.76 billion years ago. The Winagami sill complex covers an area of 120,000 km2 (46,000 sq mi).
(541.0 Mya–2.5 Gya)
|Archean eon (2.5–4 Gya)|
|Hadean eon (4–4.6 Gya)|