When did the Phanerozoic Eon begin?
Geological history of Earth
The Phanerozoic Eon is the current eon in the geologic timescale. It covers roughly 541 million years. During this period continents drifted about, eventually collected into a single landmass known as Pangea and then split up into the current continental landmasses.
Paleoarchean
The Paleoarchean (), also spelled Palaeoarchaean (formerly known as early Archean), is a geologic era within the Archaean Eon. It spans the period of time —the era is defined chronometrically and is not referenced to a specific level of a rock section on Earth. The name derives from Greek "Palaios" "ancient". The oldest ascertained life form of fossilized bacteria in microbial mats, old, found in Western Australia, is from this era. The first supercontinent Vaalbara formed during this period.
Eonothem
Eonothems have the same names as their corresponding eons, which means during the history of the Earth only four eonothems were formed. Oldest to newest these are the Hadean, Archean, Proterozoic, and Phanerozoic.
Geology of England
The Phanerozoic comprises the Palaeozoic, Mesozoic and Cenozoic eras, each of which are represented in English geology.
History of the Middle East
The Arabian Tectonic Plate was part of the African Plate during much of the Phanerozoic Eon (Paleozoic–Cenozoic), until the Oligocene Epoch of the Cenozoic Era. Red Sea rifting began in the Eocene, but the separation of Africa and Arabia occurred in the Oligocene, and since then the Arabian Plate has been slowly moving toward the Eurasian Plate.
Precambrian
The term "Precambrian" is recognized by the International Commission on Stratigraphy as the only "supereon" in geologic time; it is so called because it includes the Hadean (~4.6—4 billion), Archean (4—2.5 billion), and Proterozoic (2.5 billion—541 million) eons. (There is only one other eon: the Phanerozoic, 541 million-present.) "Precambrian" is still used by geologists and paleontologists for general discussions not requiring the more specific eon names. , the United States Geological Survey considers the term informal, lacking a stratigraphic rank.
Triassic
The Triassic () is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.9 million years ago (Mya), to the beginning of the Jurassic Period Mya. The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events.
Biodiversity
Since life began on Earth, five major mass extinctions and several minor events have led to large and sudden drops in biodiversity. The Phanerozoic eon (the last 540 million years) marked a rapid growth in biodiversity via the Cambrian explosion—a period during which the majority of multicellular phyla first appeared. The next 400 million years included repeated, massive biodiversity losses classified as mass extinction events. In the Carboniferous, rainforest collapse led to a great loss of plant and animal life. The Permian–Triassic extinction event, 251 million years ago, was the worst; vertebrate recovery took 30 million years. The most recent, the Cretaceous–Paleogene extinction event, occurred 65 million years ago and has often attracted more attention than others because it resulted in the extinction of the dinosaurs.
Oligocene
The Oligocene () is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the exact dates of the start and end of the epoch are slightly uncertain. The name Oligocene was coined in 1854 by the German paleontologist Heinrich Ernst Beyrich; the name comes from the Ancient Greek ("olígos", "few") and ("kainós", "new"), and refers to the sparsity of extant forms of molluscs. The Oligocene is preceded by the Eocene Epoch and is followed by the Miocene Epoch. The Oligocene is the third and final epoch of the Paleogene Period.
The Oligocene is often considered an important time of transition, a link between the archaic world of the tropical Eocene and the more modern ecosystems of the Miocene. Major changes during the Oligocene included a global expansion of grasslands, and a regression of tropical broad leaf forests to the equatorial belt.
Cenozoic
The Cenozoic Era () meaning "new life", is the current and most recent of the three Phanerozoic geological eras, following the Mesozoic Era and extending from 66 million years ago to the present day.
Jan Veizer
In a letter to "Nature", Veizer et al.(2000), compared the reconstruction of tropical sea surface temperatures throughout the Phanerozoic eon (the past ~550 Myr) with the variable galactic cosmic rays and concluded that their results can be reconciled if atmospheric carbon dioxide concentrations were not the principal driver of climate variability on geological timescales for at least one-third of the Phanerozoic eon, or if the reconstructed carbon dioxide concentrations are not reliable.
Geology of West Virginia
In the Cenozoic Era, which extended from 66 million years ago to present day, igneous activity was renewed in the eastern part of the State. Approximately 45 million years ago, a complex of dikes and sills with compositions ranging from basalt to rhyolite were intruded into the Paleozoic sedimentary rocks in the area in and around Pendleton County. These unusual igneous rocks are some of the youngest in eastern North America. Late in the Cenozoic Era, in fact extending to less than 100,000 years ago, glaciers covered the northern part of the North American continent, extending almost to the Northern Panhandle of West Virginia, but not into the State. Prior to the advance of these ice sheets, drainage of the Monongahela River was northward to the St. Lawrence River system. The ice sheet caused damming and a lake extended as far south as Weston. Important lake deposits, predominantly clay, were thus laid down in the Monongahela River basin. Drainage was diverted westward into the Ohio River system. Divergence of the New River system that formerly drained northwestward caused the deposition of similar deposits in the old Teays River channel between Charleston and Huntington. Except for recent alluvial deposits, there are no other known Cenozoic rocks.
Geologic temperature record
The Phanerozoic eon, encompassing the last 542 million years and almost the entire time since the origination of complex multi-cellular life, has more generally been a period of fluctuating temperature between ice ages, such as the current age, and "climate optima", similar to what occurred in the Cretaceous. Roughly 4 such cycles have occurred during this time with an approximately 140 million year separation between climate optima. In addition to the present, ice ages have occurred during the Permian-Carboniferous interval and the late Ordovician-early Silurian. There is also a "cooler" interval during the Jurassic and early Cretaceous, with evidence of increased sea ice, but the lack of continents at either pole during this interval prevented the formation of continental ice sheets and consequently this is usually not regarded as a full-fledged ice age. In between these cold period, warmer conditions were present and often referred to as climate optima. However, it has been difficult to determine whether these warmer intervals were actually hotter or colder than occurred during the Cretaceous optima.
History of Earth
The Proterozoic eon lasted from 2.5 Ga to 542 Ma (million years) ago. In this time span, cratons grew into continents with modern sizes. The change to an oxygen-rich atmosphere was a crucial development. Life developed from prokaryotes into eukaryotes and multicellular forms. The Proterozoic saw a couple of severe ice ages called snowball Earths. After the last Snowball Earth about 600 Ma, the evolution of life on Earth accelerated. About 580 Ma, the Ediacaran biota formed the prelude for the Cambrian Explosion.
Phanerozoic
The time span of the Phanerozoic starts with what appears to be the rapid emergence of a number of animal phyla; the evolution of those phyla into diverse forms; the emergence and development of complex plants; the evolution of fish; the emergence of insects and tetrapods; and the development of modern fauna. Plant life on land appeared in the early Phanerozoic eon. During this time span, tectonic forces caused the continents to move and eventually collect into a single landmass known as Pangaea (the most recent supercontinent), which then separated into the current continental landmasses.
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pЄ, or Cryptozoic) 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 Latinised name for Wales, where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time.
Phanerozoic
The Proterozoic-Phanerozoic boundary is at  million years ago. In the 19th century, the boundary was set at time of appearance of the first abundant animal (metazoan) fossils but several hundred groups (taxa) of metazoa of the earlier Proterozoic era have been identified since the systematic study of those forms started in the 1950s. Most geologists and paleontologists would probably set the Proterozoic-Phanerozoic boundary either at the classic point where the first trilobites and reef-building animals (archaeocyatha) such as corals and others appear; at the first appearance of a complex feeding burrow called "Treptichnus pedum"; or at the first appearance of a group of small, generally disarticulated, armored forms termed 'the small shelly fauna'. The three different dividing points are within a few million years of each other.
Evolution of tetrapods
The Cenozoic era began with the end of the Mesozoic era and the Cretaceous epoch; and continues to this day. The beginning of the Cenozoic was marked by the Cretaceous-Paleogene extinction event during which all non-avian dinosaurs became extinct. The Cenozoic is sometimes called the "Age of Mammals".
Timeline of the evolutionary history of life
The Phanerozoic Eon, literally the "period of well-displayed life," marks the appearance in the fossil record of abundant, shell-forming and/or trace-making organisms. It is subdivided into three eras, the Paleozoic, Mesozoic and Cenozoic, which are divided by major mass extinctions.
Bronze Age Europe
The Minoan civilization based on Knossos, Crete, appears to have coordinated and defended its Bronze Age trade. One crucial lack in this period was that modern methods of accounting were not available. The eruption of Thera, which according to archaeological data occurred in c. 1500 BC, resulted in the decline of the Minoan. This turn of events gave the opportunity to the Mycenaeans to spread their influence throughout the Aegean. Around c. 1450 BC, they were in control of Crete itself and colonized several other Aegean islands, reaching as far as Rhodes. Thus the Mycenaeans became the dominant power of the region, marking the beginning of the Mycenaean 'Koine' era (from , common), a highly uniform culture that spread in mainland Greece and the Aegean. The Mycenaean Greeks introduced several innovations in the fields of engineering, architecture and military infrastructure, while trade over vast areas of the Mediterranean was essential for the Mycenaean economy. Their syllabic script, the Linear B, offers the first written records of the Greek language and their religion already included several deities that can be also found in the Olympic Pantheon. Mycenaean Greece was dominated by a warrior elite society and consisted of a network of palace states that developed rigid hierarchical, political, social and economic systems. At the head of this societies was the king, known as wanax.
Cenozoic
The Pliocene epoch lasted from 5.333 to 2.58 million years ago. The Pliocene featured dramatic climactic changes, which ultimately led to modern species and plants. The Mediterranean Sea dried up for several million years (because the ice ages reduced sea levels, disconnecting the Atlantic from the Mediterranean, and evaporation rates exceeded inflow from rivers). "Australopithecus" evolved in Africa, beginning the human branch. The isthmus of Panama formed, and animals migrated between North and South America, wreaking havoc on local ecologies. Climatic changes brought: savannas that are still continuing to spread across the world; Indian monsoons; deserts in central Asia; and the beginnings of the Sahara desert. The world map has not changed much since, save for changes brought about by the glaciations of the Quaternary, such as the Great Lakes, Hudson Bay, and the Baltic sea.
Aeon
Although the term aeon may be used in reference to a period of a billion years (especially in geology, cosmology or astronomy), its more common usage is for any long, indefinite, period. Aeon can also refer to the four aeons on the Geologic Time Scale that make up the Earth's history, the Hadean, Archean, Proterozoic, and the current aeon Phanerozoic.
Mesozoic–Cenozoic radiation
The Mesozoic–Cenozoic Radiation is the third major extended increase in biodiversity in the Phanerozoic, after the Cambrian Explosion and the Great Ordovician Biodiversification Event. The Mesozoic–Cenozoic Radiation began in the mid-Mesozoic and extends through the Cenozoic, with no indication of having yet ended. It differs from the earlier radiations in that the diversity appears largely in the variety of species and other taxa below the level of order. "The spectacular radiation of the angiosperms, mammals and certain reptile groups (such as the snakes) on land is matched by that of the planktonic foraminifera, neogastropods, heteroconch bivalves, cheilostome bryozoans, decapod crustaceans and teleost fish in shallow seas." The marine diversification is largely that represented by the modern evolutionary fauna, and there are also the terrestrial diversifications of the birds and among the insects.
Geology of the Pyrenees
In "Ilerdian" and "Cuisian" times (Paleocene/Eocene boundary, Thanetian/Ypresian, about 55 million years ago), the Pyrenees underwent very strong compression in the upper crust, bringing about the orogen's actual zonation and structural organisation. The orogen was squeezed into an asymmetric fan-like structure due to the aborted subduction of Iberia underneath Aquitania. This is inferred from the behaviour of the Mohorovicic discontinuity, which at the North Pyrenean Fault abruptly jumps from 30 to 50 km depth. This "Pyrenean Main Phase" lasted till about 47 million years ago (beginning of the Lutetian), showing high shortening rates of 4.0 to 4.4 mm/year and emplacing for example the Lower Pedraforca and the Montsec thrust sheets.
Phanerozoic
It has been demonstrated that changes in biodiversity through the Phanerozoic correlate much better with the hyperbolic model (widely used in demography and macrosociology) than with exponential and logistic models (traditionally used in population biology and extensively applied to fossil biodiversity as well). The latter models imply that changes in diversity are guided by a first-order positive feedback (more ancestors, more descendants) or a negative feedback that arises from resource limitation, or both. The hyperbolic model implies a second-order positive feedback. The hyperbolic pattern of the human population growth arises from a second-order positive feedback, caused by the interaction of the population size and the rate of technological growth. The character of biodiversity growth in the Phanerozoic Eon can be similarly accounted for by a feedback between the diversity and community structure complexity. It is suggested that the similarity between the curves of biodiversity and human population probably comes from the fact that both are derived from the superposition on the hyperbolic trend of cyclical and random dynamics.
Geology of Arizona
Due to flat subduction during the final phase of the Laramide orogeny from 54 to 43 million years ago in the Eocene epoch of the Cenozoic, deep intrusion of granite and pegmatite took place, 23 kilometers below the surface. Granitic plutons tended to form near well-developed crush zone and often have tungsten and quartz rich veins in garnet-muscovite granitoids and pegmatite dikes. The Santa Catalina Mountains north and northeast of Tucson contain the Wilderness Granite, which formed as an intrusion 14 miles below the surface. The Colorado Plateau uplifted and began to erode during the Eocene.
Prehistoric Planet
220,000,000 BC, Late Triassic (Arizona) − This episode follows the evolution of the first dinosaurs and other prehistoric creatures in the late Triassic period.152,000,000 BC, Late Jurassic (Colorado) − This episode follows the story of a young female "Diplodocus" and her brothers and sisters in the late Jurassic period.149,000,000 BC, Late Jurassic (Oxfordshire) − This episode follows the life of several baby "Ophthalmosaurus" and a bull "Liopleurodon" in the late Jurassic period.127,000,000 BC, Early Cretaceous (Brazil) − This episode follows a male "Ornithocheirus" on his long journey to the mating grounds in the early Cretaceous period.106,000,000 BC, Early Cretaceous (Antarctica) − This episode follows the hardships of an Antarctican "Leaellynasaura" clan in the early Cretaceous period.65,500,000 BC, Late Cretaceous (Montana) − This episode follows the final years of the dinosaurs and a mother "Tyrannosaurus rex" and her babies in the late Cretaceous period.49,000,000 BC, Early Eocene (Germany) − This episode follows the life of a mother "Leptictidium" and her babies in the dense forests of Germany in the early Eocene epoch.36,000,000 BC, Late Eocene (Pakistan) − This episode follows the sea journey of a pregnant female "Basilosaurus" search for food in the late Eocene epoch.25,000,000 BC, Late Oligocene (Mongolia) − This episode follows the life of a young "Paraceratherium" and his mother from his birth in the late Oligocene epoch.3,200,000 BC, Late Pliocene (Ethiopia) − This episode follows the hardships of an "Australopithecus" group and a young called Blue in the late Pliocene epoch.1,000,000 BC, Early Pleistocene (Paraguay) − This episode follows a male "Smilodon" called Half-Tooth after he lost his territory in the early Pleistocene epoch.30,000 BC, Late Pleistocene (North Sea, Belgium, and Swiss Alps) − This episode follows a herd of woolly mammoth journey to the Alps in the last Ice Age of the late Pleistocene epoch.This episode details a list of animals from the first season that the developers thought were the most impressive creatures on Earth.
History of Earth
The Paleozoic ("old life") era was the first and longest era of the Phanerozoic eon, lasting from 542 to 251 Ma. During the Paleozoic, many modern groups of life came into existence. Life colonized the land, first plants, then animals. Two major extinctions occurred. The continents formed at the break-up of Pannotia and Rodinia at the end of the Proterozoic slowly moved together again, forming the supercontinent Pangaea in the late Paleozoic.
History of Earth
The Cenozoic ("new life") era began at  Ma, and is subdivided into the Paleogene, Neogene, and Quaternary periods. These three periods are further split into seven sub-divisions, with the Paleogene composed of The Paleocene, Eocene, and Oligocene, the Neogene divided into the Miocene, Pliocene, and the Quaternary composed of the Pleistocene, and Holocene. Mammals, birds, amphibians, crocodilians, turtles, and lepidosaurs survived the Cretaceous–Paleogene extinction event that killed off the non-avian dinosaurs and many other forms of life, and this is the era during which they diversified into their modern forms.
Euxinia
There is evidence for multiple euxinic events during the Phanerozoic. It is most likely that euxinia was periodic during the Paleozoic and Mesozoic, but geologic data is too sparse to draw any large scale conclusions. In this eon, there is some evidence that euxinic events are potentially linked with mass extinction events including the Late Devonian and Permian–Triassic.
Liaoning
Since then, dozens of ground-breaking finds have been discovered throughout the Jehol group. These including the earliest flower, earliest eutherian mammal, known as "Eomaia", the earliest known metatherian, an intact embryo of a pterosaur, "Repenomamus robustus"—a 15 kg heavy mammal that ate dinosaurs, "Sinornithosaurus millenii", as well as many birds and feathered dinosaurs. Discoveries such as "Dilong paradoxus", another feathered theropod, date to the early Cretaceous Period. This is some 60 million years before "Tyrannosaurus", and thus these discoveries push the evolution of feathers earlier than previously thought.
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.
Phanerozoic
The Miocene spans from 23.03 to 5.333 million years ago and is a period in which grass spread further across, effectively dominating a large portion of the world, diminishing forests in the process. Kelp forests evolved, leading to the evolution of new species, such as sea otters. During this time, perissodactyla thrived, and evolved into many different varieties. Alongside them were the apes, which evolved into a 30 species. Overall, arid and mountainous land dominated most of the world, as did grazers. The Tethys Sea finally closed with the creation of the Arabian Peninsula and in its wake left the Black, Red, Mediterranean and Caspian Seas. This only increased aridity. Many new plants evolved, and 95% of modern seed plants evolved in the mid-Miocene.
Geological history of Earth
The Phanerozoic is divided into three eras – the Paleozoic, the Mesozoic and the Cenozoic.
Minoan civilization
The Early Bronze Age (3500 to 2100 BC) has been described as indicating a "promise of greatness" in light of later developments on the island. The Bronze Age began on Crete around 3200 BC. In the late third millennium BC, several locations on the island developed into centers of commerce and handiwork, enabling the upper classes to exercise leadership and expand their influence. It is likely that the original hierarchies of the local elites were replaced by monarchies, a precondition for the palaces.
Copernican period
Its Earth equivalents are the Neoproterozoic era of the Proterozoic eon and the whole of the Phanerozoic eon. So, while animal life bloomed on Earth, the Moon's geologic activity was coming to an end.
Phanerozoic
The Paleogene spans from the extinction of the non-avian dinosaurs, some 66 million years ago, to the dawn of the Neogene 23 million years ago. It features three epochs: Paleocene, Eocene and Oligocene.
Eoarchean
The Eoarchean (; also spelled Eoarchaean) is the first era of the Archean Eon of the geologic record for which the Earth has a solid crust. It spans 400 million years from the end of the Hadean Eon 4 billion years ago (4000 Mya) to the start of the Paleoarchean Era 3600 Mya. The beginnings of life on Earth have been dated to this era and evidence of cyanobacteria date to 3500 Mya, just outside this era. At that time, the atmosphere was without oxygen and the pressure values ranged from 10 to 100 bar (around 10 to 100 atmospheres).
Phanerozoic
The Middle Triassic spans from 247 million to 237 million years ago. The Middle Triassic featured the beginnings of the breakup of Pangaea, and the beginning of the Tethys Sea. The ecosystem had recovered from the devastation of the Great Dying. Phytoplankton, coral, and crustaceans all had recovered, and the reptiles began increasing in size. New aquatic reptiles, such as ichthyosaurs and nothosaurs, proliferated in the seas. Meanwhile, on land, pine forests flourished, as well as mosquitoes and fruit flies. The first ancient crocodilians evolved, which sparked competition with the large amphibians that had long ruled the freshwater world.
Paleozoic
The Paleozoic (or Palaeozoic) Era (; from the Greek "palaios" (παλαιός), "old" and "zoe" (ζωή), "life", meaning "ancient life") is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era.
Cryogenian
Before the start of the Cryogenian, around 750 Ma, the cratons that made up the supercontinent Rodinia started to rift apart. The superocean Mirovia began to close while the superocean Panthalassa began to form. The cratons (possibly) later assembled into another supercontinent called Pannotia, in the Ediacaran.
Geology of Ghana
The Phanerozoic, the current eon in which multicellular life became commonplace is mainly recorded along the coast of Ghana. The Accraian Series deposited in the Early Devonian and Middle Devonian while the Sekondian Series formed between the Middle Devonian and the Early Cretaceous, overlapping with the Late Jurassic to Early Cretaceous Amisian Group. The Late Cretaceous Apollonian Group is among the most recent rock units. The past 66 million years of the Cenozoic are mainly recorded with marine, lagoonal and riverine sedimentary rocks as well as with unconsolidated sediments that cover most of the country and form soils.
Era (geology)
A geologic era is a subdivision of geologic time that divides an eon into smaller units of time. The Phanerozoic Eon is divided into three such time frames: the Paleozoic, Mesozoic, and Cenozoic (meaning "old life", "middle life" and "recent life") that represent the major stages in the macroscopic fossil record. These eras are separated by catastrophic extinction boundaries, the P-T boundary between the Paleozoic and the Mesozoic and the K-Pg boundary between the Mesozoic and the Cenozoic. There is evidence that catastrophic meteorite impacts played a role in demarcating the differences between the eras.
Geological history of Earth
The geologic record of the Proterozoic () is more complete than that for the preceding Archean. In contrast to the deep-water deposits of the Archean, the Proterozoic features many strata that were laid down in extensive shallow epicontinental seas; furthermore, many of these rocks are less metamorphosed than Archean-age ones, and plenty are unaltered. Study of these rocks show that the eon featured massive, rapid continental accretion (unique to the Proterozoic), supercontinent cycles, and wholly modern orogenic activity. Roughly , the earliest-known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia, 600–540 Ma.
History of Earth
The Phanerozoic is the current eon on Earth, which started approximately 542 million years ago. It consists of three eras: The Paleozoic, Mesozoic, and Cenozoic, and is the time when multi-cellular life greatly diversified into almost all the organisms known today.
Tuareg Shield
At the start of the Phanerozoic the shield was eroded and covered by Ordovician sandstones. More recently, around 95 Ma - 90 Ma, the area was partly submerged by a seaway linking the Mediterranean and the proto-Atlantic. Since then, starting around 30 Ma the area rose by as much as 3000 meters.
Early Jurassic
The Early Jurassic epoch (in chronostratigraphy corresponding to the Lower Jurassic series) is the earliest of three epochs of the Jurassic period. The Early Jurassic starts immediately after the Triassic-Jurassic extinction event, 201.3 Ma (million years ago), and ends at the start of the Middle Jurassic 174.1 Ma.
Phanerozoic
The Phanerozoic is divided into three eras: the Paleozoic, Mesozoic, and Cenozoic, which are further subdivided into 12 periods. The Paleozoic features the rise of fish, amphibians and reptiles. The Mesozoic is ruled by the reptiles, and features the evolution of mammals, birds and more famously, dinosaurs. The Cenozoic is the time of the mammals, and more recently, humans.
Ōnin War
Warfare begins
Phanerozoic
The Early Cretaceous Epoch spans from 145 million to 100 million years ago. The Early Cretaceous saw the expansion of seaways, and as a result, the decline and extinction of sauropods (except in South America). Many coastal shallows were created, and that caused ichthyosaurs to die out. Mosasaurs evolved to replace them as apex species of the seas. Some island-hopping dinosaurs, like "Eustreptospondylus", evolved to cope with the coastal shallows and small islands of ancient Europe. Other dinosaurs, such as "Carcharodontosaurus" and "Spinosaurus", rose to fill the empty space that the Jurassic-Cretaceous extinction had created. Of the most successful would be the "Iguanodon" which spread to every continent. Seasons came back into effect and the poles grew seasonally colder. Dinosaurs such as the "Leaellynasaura" inhabited the polar forests year-round, while many dinosaurs, such as the "Muttaburrasaurus", migrated there during summer . Since it was too cold for crocodiles, it was the last stronghold for large amphibians, such as the "Koolasuchus". In this epoch Pterosaurs reached their maximum diversity and grew larger, as species like "Tapejara" and "Ornithocheirus" took to the skies. The first true birds evolved, possibly sparking competition between them and the pterosaurs.
Paleozoic
The Cambrian spans from 541 million years to 485 million years and is the first period of the Paleozoic era of the Phanerozoic. The Cambrian marked a boom in evolution in an event known as the Cambrian explosion in which the largest number of creatures evolved in any single period of the history of the Earth. Creatures like algae evolved, but the most ubiquitous of that period were the armored arthropods, like trilobites. Almost all marine phyla evolved in this period. During this time, the supercontinent Pannotia begins to break up, most of which later became the supercontinent Gondwana.
Phanerozoic
The Late Cretaceous Epoch spans from 100 million to 66 million years ago. The Late Cretaceous featured a cooling trend that would continue into the Cenozoic Era. Eventually, tropical ecology was restricted to the equator and areas beyond the tropic lines featured extreme seasonal changes of weather. Dinosaurs still thrived as new species such as "Tyrannosaurus", "Ankylosaurus", "Triceratops" and Hadrosaurs dominated the food web. Whether or not Pterosaurs went into a decline as birds radiated is debated, however many families survived until the end of the Cretaceous, alongside new species such as the gigantic "Quetzalcoatlus". Marsupials evolved within the large conifer forests as scavengers. In the oceans, Mosasaurs ruled the seas to fill the role of the ichthyosaurs, and huge plesiosaurs, such as "Elasmosaurus", evolved. Also, the first flowering plants evolved. At the end of the Cretaceous, the Deccan Traps and other volcanic eruptions were poisoning the atmosphere. As this was continued, it is thought that a large meteor smashed into Earth, creating the Chicxulub Crater creating the event known as the K-T Extinction, the fifth and most recent mass extinction event, during which 75% of life on Earth became extinct, including all non-avian dinosaurs. Every living thing with a body mass over 10 kilograms became extinct, and the age of the dinosaurs came to an end.
Climate across Cretaceous–Paleogene boundary
The Paleocene (the first epoch of the Paleogene) immediately followed the asteroid impact that destroyed the dinosaurs and the Cretaceous world. It marks the transition between the dinosaurs of the Mesozoic and the emergence of the larger mammals of the Eocene (Cenozoic). The early part of the period experienced cooler temperatures and a more arid climate than existed before the asteroid. This is most likely due to atmospheric dust reflecting sunlight for an extended time. But in the latter part of the epoch, the temperatures warmed significantly, resulting in the absence of glaciated poles and the presence of verdant, tropical forests. The warmer climate increased ocean temperatures leading to a proliferation of species such as coral and other invertebrates.
Phanerozoic
The Devonian spans from 419 million years to 359 million years ago. Also informally known as the "Age of the Fish", the Devonian features a huge diversification in fish, including armored fish like "Dunkleosteus" and lobe-finned fish which eventually evolved into the first tetrapods. On land, plant groups diversified; the first trees and seeds evolved. By the Middle Devonian, shrub-like forests of primitive plants existed: lycophytes, horsetails, ferns, and progymnosperm. This event also allowed the diversification of arthropod life as they took advantage of the new habitat. The first amphibians also evolved, and the fish were now at the top of the food chain. Near the end of the Devonian, 70% of all species became extinct in an event known as the Late Devonian extinction, which is the second mass extinction known to have happened.
Mesozoic
The Triassic was generally dry, a trend that began in the late Carboniferous, and highly seasonal, especially in the interior of Pangaea. Low sea levels may have also exacerbated temperature extremes. With its high specific heat capacity, water acts as a temperature-stabilizing heat reservoir, and land areas near large bodies of water—especially oceans—experience less variation in temperature. Because much of Pangaea's land was distant from its shores, temperatures fluctuated greatly, and the interior probably included expansive deserts. Abundant red beds and evaporites such as halite support these conclusions, but some evidence suggests the generally dry climate of was punctuated by episodes of increased rainfall. The most important humid episodes were the Carnian Pluvial Event and one in the Rhaetian, a few million years before the Triassic–Jurassic extinction event.
Geologic time scale
The primary defined divisions of time are eons, in sequence the Hadean, the Archean, the Proterozoic and the Phanerozoic.
The first three of these can be referred to collectively as the Precambrian supereon. 
Eons are divided into eras, which are in turn divided into periods, epochs and ages.
Proterozoic
The geologic record of the Proterozoic Eon is more complete than that for the preceding Archean Eon. In contrast to the deep-water deposits of the Archean, the Proterozoic features many strata that were laid down in extensive shallow epicontinental seas; furthermore, many of those rocks are less metamorphosed than are Archean ones, and many are unaltered. Studies of these rocks have shown that the eon continued the massive continental accretion that had begun late in the Archean Eon. The Proterozoic Eon also featured the first definitive supercontinent cycles and wholly modern mountain building activity (orogeny).
Greenhouse gas
Ice cores provide evidence for greenhouse gas concentration variations over the past 800,000 years (see the following section). Both and vary between glacial and interglacial phases, and concentrations of these gases correlate strongly with temperature. Direct data does not exist for periods earlier than those represented in the ice core record, a record that indicates mole fractions stayed within a range of 180 ppm to 280 ppm throughout the last 800,000 years, until the increase of the last 250 years. However, various proxies and modeling suggests larger variations in past epochs; 500 million years ago levels were likely 10 times higher than now. Indeed, higher concentrations are thought to have prevailed throughout most of the Phanerozoic eon, with concentrations four to six times current concentrations during the Mesozoic era, and ten to fifteen times current concentrations during the early Palaeozoic era until the middle of the Devonian period, about 400 Ma. The spread of land plants is thought to have reduced concentrations during the late Devonian, and plant activities as both sources and sinks of have since been important in providing stabilising feedbacks.
Earlier still, a 200-million year period of intermittent, widespread glaciation extending close to the equator (Snowball Earth) appears to have been ended suddenly, about 550 Ma, by a colossal volcanic outgassing that raised the concentration of the atmosphere abruptly to 12%, about 350 times modern levels, causing extreme greenhouse conditions and carbonate deposition as limestone at the rate of about 1 mm per day. This episode marked the close of the Precambrian eon, and was succeeded by the generally warmer conditions of the Phanerozoic, during which multicellular animal and plant life evolved. No volcanic carbon dioxide emission of comparable scale has occurred since. In the modern era, emissions to the atmosphere from volcanoes are approximately 0.645 billion tons of per year, whereas humans contribute 29 billion tons of each year.
Cenozoic
The Eocene Epoch ranged from 56 million years to 33.9 million years ago. In the Early-Eocene, species living in dense forest were unable to evolve into larger forms, as in the Paleocene. There was nothing over the weight of 10 kilograms. Among them were early primates, whales and horses along with many other early forms of mammals. At the top of the food chains were huge birds, such as Paracrax. The temperature was 30 degrees Celsius with little temperature gradient from pole to pole. In the Mid-Eocene, the Circumpolar-Antarctic current between Australia and Antarctica formed. This disrupted ocean currents worldwide and as a result caused a global cooling effect, shrinking the jungles. This allowed mammals to grow to mammoth proportions, such as whales which, by that time, had become almost fully aquatic. Mammals like "Andrewsarchus" were at the top of the food-chain. The Late Eocene saw the rebirth of seasons, which caused the expansion of savanna-like areas, along with the evolution of grass. The end of the Eocene was marked by the Eocene-Oligocene extinction event, the European face of which is known as the Grande Coupure.
Phanerozoic
The Paleozoic is a time in Earth's history when complex life forms evolved, took their first breath of oxygen on dry land, and when the forerunners of all life on Earth began to diversify. There are six periods in the Paleozoic era: Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian.
History of Eurasia
In the beginning of the last ice age a supervolcano erupted in Indonesia. Theory states the effects of the eruption caused global climatic changes for many years, effectively obliterating most of the earlier cultures. Y-chromosomal Adam (90000 - 60000 BP, dated data) was initially dated here. Neanderthals survived this abrupt change in the environment, so it's possible for other human groups too. According to the theory humans survived in Africa, and began to resettle areas north, as the effects of the eruption slowly vanished. Upper Paleolithic revolution began after this extreme event, the earliest finds are dated c.50000 BCE.
Paleontology in Oklahoma
Paleontology in Oklahoma refers to paleontological research occurring within or conducted by people from the U.S. state of Oklahoma.
Oklahoma has a rich fossil record spanning all three eras of the Phanerozoic Eon. Oklahoma is the best source of Pennsylvanian fossils in the United States due to having an exceptionally complete geologic record of the epoch. From the Cambrian to the Devonian, all of Oklahoma was covered by a sea that would come to be home to creatures like brachiopods, bryozoans, graptolites and trilobites. During the Carboniferous, an expanse of coastal deltaic swamps formed in areas of the state where early tetrapods would leave behind footprints that would later fossilize. The sea withdrew altogether during the Permian period. Oklahoma was home a variety of insects as well as early amphibians and reptiles. Oklahoma stayed dry for most of the Mesozoic. During the Late Triassic, carnivorous dinosaurs left behind footprints that would later fossilize. During the Cretaceous, however, the state was mostly covered by the Western Interior Seaway, which was home to huge ammonites and other marine invertebrates. During the Cenozoic, Oklahoma became home to creatures like bison, camels, creodonts, and horses. During the Ice Age, the state was home to mammoths and mastodons. Local Native Americans are known to have used fossils for medicinal purposes. The Jurassic dinosaur "Saurophaganax maximus" is the Oklahoma state fossil.
Phanerozoic
The Neogene spans from 23.03 million to 2.58 million years ago. It features 2 epochs: the Miocene, and the Pliocene.
Museum of Paleontology Egidio Feruglio
MEF's permanent exhibition is a journey into the natural past of Patagonia. It begins about 10,000 years ago, with the first human settlements in the area. In each room, specimens from both terrestrial and marine life forms are shown for each geological period, up to the early Paleozoic. The Mesozoic hall depicting the giant dinosaurs of Patagonia is perhaps the most popular attraction in the museum. The journey goes on at the mini-theatre with a film showing the evolution of the Universe back to the Big Bang itself.
Mycenaean Greece
The eruption of Thera, which according to archaeological data occurred in c. 1500 BC, resulted in the decline of the Minoan civilization of Crete. This turn of events gave the opportunity to the Mycenaeans to spread their influence throughout the Aegean. Around c. 1450 BC, they were in control of Crete itself, including Knossos, and colonized several other Aegean islands, reaching as far as Rhodes. Thus the Mycenaeans became the dominant power of the region, marking the beginning of the Mycenaean 'Koine' era (from , common), a highly uniform culture that spread in mainland Greece and the Aegean.
Paleozoic
While macroscopic plant life appeared early in the Paleozoic Era and possibly late in the Neoproterozoic Era of the earlier eon, plants mostly remained aquatic until the Silurian Period, about 420 million years ago, when they began to transition onto dry land. Terrestrial flora reached its climax in the Carboniferous, when towering lycopsid rainforests dominated the tropical belt of Euramerica. Climate change caused the Carboniferous Rainforest Collapse which fragmented this habitat, diminishing the diversity of plant life in the late Carboniferous and Permian.
Era
In large-scale natural science, there is need for another time perspective, independent from human activity, and indeed spanning a far longer period (mainly prehistoric), where "geologic era" refers to well-defined time spans. 
The next-larger division of geologic time is the eon. The Phanerozoic Eon is subdivided into eras. There are currently three eras defined in the Phanerozoic; the following table lists them from youngest to oldest (BP is an abbreviation for "before present").
The Ocean (band)
On 14 February 2018, a photo was posted on the Instagram account of the band, depicting a recording studio. Three days later, another picture reached the surface stating that the "phanerozoic" recordings are in progress at the Sundlaugin studios in Iceland. The 22nd of August 2018, the band announced on their Instagram, that the new album will be split in two. "Phanerozoic I: Palaeozoic" was released on 2 November 2018 while "Phanerozoic II" is expected to be released in 2019. These albums will respectively be the band's seventh and eighth studio albums.
Atmosphere of Earth
Before this time, any oxygen produced by photosynthesis was consumed by oxidation of reduced materials, notably iron. Molecules of free oxygen did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials that removed oxygen. This point signifies a shift from a reducing atmosphere to an oxidizing atmosphere. O showed major variations until reaching a steady state of more than 15% by the end of the Precambrian. The following time span from 541 million years ago to the present day is the Phanerozoic Eon, during the earliest period of which, the Cambrian, oxygen-requiring metazoan life forms began to appear.
Dinosaur
Non-avian dinosaur remains are occasionally found above the Cretaceous–Paleogene boundary. In 2001, paleontologists Zielinski and Budahn reported the discovery of a single hadrosaur leg-bone fossil in the San Juan Basin, New Mexico, and described it as evidence of Paleocene dinosaurs. The formation in which the bone was discovered has been dated to the early Paleocene epoch, approximately 64.5 million years ago. If the bone was not re-deposited into that stratum by weathering action, it would provide evidence that some dinosaur populations may have survived at least a half million years into the Cenozoic Era. Other evidence includes the finding of dinosaur remains in the Hell Creek Formation up to above the Cretaceous–Paleogene boundary, representing  years of elapsed time. Similar reports have come from other parts of the world, including China. Many scientists, however, dismissed the supposed Paleocene dinosaurs as re-worked, that is, washed out of their original locations and then re-buried in much later sediments. Direct dating of the bones themselves has supported the later date, with U–Pb dating methods resulting in a precise age of 64.8 ± 0.9 million years ago. If correct, the presence of a handful of dinosaurs in the early Paleocene would not change the underlying facts of the extinction.
Prehistory of Iran
The end of the Palaeolithic, called Epipalaeolithic, is in a period of about 7000 years from c. 18,000 to 11,000 BC. In those days groups of hunter-gatherers were mostly living in the caves of the Zagros Mountains. Compared to earlier groups of game hunters, a tendency towards increasing the number of the kinds of plants and animals, which were collected and hunted, can be observed. Not only smaller vertebrates were hunted but also pistachios and wild fruit were collected. Finally, consuming snails and smaller aquatic animals like crabs is new (Flannery 1973).
Almost nothing is known about the 2500 years which followed the Epipalaeolithic after 11,000 BC. Only when discovering the place of Asiab (c. 8500-8000) in the Kermanshah area we are in better known periods. Asiab was a small camp of hunter-gatherers, only seasonally inhabited. Besides the fact that wild goats and sheep were hunted, great numbers of snail shells were found. These finds were interpreted in the way that from time to time the hunting activities of the inhabitants of Asiab were unsuccessful and that then they were forced to consume food which they usually did not like.
Geological history of Earth
The Paleozoic spanned from roughly (Ma) and is subdivided into six geologic periods; from oldest to youngest they are the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian. Geologically, the Paleozoic starts shortly after the breakup of a supercontinent called Pannotia and at the end of a global ice age. Throughout the early Paleozoic, the Earth's landmass was broken up into a substantial number of relatively small continents. Toward the end of the era the continents gathered together into a supercontinent called Pangaea, which included most of the Earth's land area.
Phanerozoic
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers million years to the present, and began with the Cambrian Period when diverse hard-shelled animals first appeared. Its name was derived from the Ancient Greek words () and (), meaning "visible life", since it was once believed that life began in the Cambrian, the first period of this eon. The term "Phanerozoic" was coined in 1930 by the American geologist George Halcott Chadwick (1876–1953). The time before the Phanerozoic, called the "Precambrian", is now divided into the Hadean, Archaean and Proterozoic eons.
Paleogene
This period consists of the Paleocene, Eocene, and Oligocene epochs. The end of the Paleocene (55.5/54.8 Mya) was marked by the Paleocene–Eocene Thermal Maximum, one of the most significant periods of global change during the Cenozoic, which upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and on land, a major turnover in mammals. The terms 'Paleogene System' (formal) and 'lower Tertiary System' (informal) are applied to the rocks deposited during the 'Paleogene Period'. The somewhat confusing terminology seems to be due to attempts to deal with the comparatively fine subdivisions of time possible in the relatively recent geologic past, for which more details are preserved. When the Tertiary Period is divided into two periods instead of directly into five epochs, the periods are more closely comparable to the duration of 'periods' of the preceding Mesozoic and Paleozoic Eras.
History of invertebrate paleozoology
In 1947, paleontologist Reg Sprigg discovered the Ediacaran fauna -- the "best-preserved" fossil invertebrates of the billion-year-long Proterozoic eon. Darwin's 1859 embarrassment at the absence of Pre-Cambrian fossils was now put at rest.
Phanerozoic
The Early Jurassic Epoch spans from 201 million to 174 million years ago. The climate was much more humid than the Triassic, and as a result, the world was very tropical. In the oceans, plesiosaurs, ichthyosaurs and ammonites dominated the seas. On land, dinosaurs and other reptiles dominated the land, with species such as "Dilophosaurus" at the apex. The first true crocodiles evolved, pushing the large amphibians to near extinction. The reptiles rose to rule the world. Meanwhile, the first true mammals evolved, but never exceeded the height of a shrew.
Ediacaran
The Ediacaran Period (), spans 94 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 541 Mya. It marks the end of the Proterozoic Eon, and the beginning of the Phanerozoic Eon. It is named after the Ediacara Hills of South Australia.
Eocene Thermal Maximum 2
The hyperthermals were geologically brief time intervals (<200,000 years) of global warming and massive carbon input. The most extreme and best-studied event, the Paleocene-Eocene Thermal Maximum (PETM or ETM-1), occurred about 1.8 million years before ETM-2, at approximately 55.5 Ma. Other hyperthermals likely followed ETM-2 at nominally 53.6 Ma (H-2), 53.3 (I-1), 53.2 (I-2) and 52.8 Ma (informally called K, X or ETM-3). The number, nomenclature, absolute ages and relative global impact of the Eocene hyperthermals are the source of much current research.
In any case, the hyperthermals appear to have ushered in the Early Eocene Climatic Optimum, the warmest interval of the Cenozoic Era. They also definitely precede the Azolla event at about 49 Ma.
Cenozoic
The Holocene began 11,700 years ago and lasts to the present day. All recorded history and "the history of the world" lies within the boundaries of the Holocene epoch. Human activity is blamed for a mass extinction that began roughly 10,000 years ago, though the species becoming extinct have only been recorded since the Industrial Revolution. This is sometimes referred to as the "Sixth Extinction". It is often cited that over 322 recorded species have become extinct due to human activity since the Industrial Revolution, but the rate may be as high as 500 veterbrate species alone, the majority of which have occurred after 1900.
Paleocene
The end of the Paleocene (≈55.8 Ma) was also marked by a time of major change, one of the most significant periods of global change during the Cenozoic. The Paleocene–Eocene Thermal Maximum upset oceanic and atmospheric circulation and led to the extinction of numerous deep-sea benthic foraminifera and a major turnover in mammals on land.
Cretaceous
The Cretaceous (, ) is a geologic period and system that spans 79 million years from the end of the Jurassic Period million years ago (mya) to the beginning of the Paleogene Period mya. It is the last period of the Mesozoic Era, and the longest period of the Phanerozoic Eon. The Cretaceous Period is usually abbreviated K, for its German translation "Kreide" (chalk, "creta" in Latin).
Stratigraphy of the Cambrian
The base of the Cambrian is officially defined as the first appearance of a certain trace fossil, "Treptichnus pedum". However, this fossil also appears in older rocks than the locality which officially marks the start of the period. However, there is a period of biological change which makes this time period a good one to demarkate the Cambrian from the earlier Phanerozoic eon's periods and the Precambrian supereon. Consensus holds that fossils of the Ediacara biota disappear here, as do some shelly fossils and acritarchs; and a new small shelly fossil biota emerges.
Cambrian
The Cambrian Period ( or ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago (mya) to the beginning of the Ordovician Period mya. Its subdivisions, and its base, are somewhat in flux. The period was established (as “Cambrian series”) by Adam Sedgwick, who named it after Cambria, the Latin name of Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of sedimentary deposits, sites of exceptional preservation where "soft" parts of organisms are preserved as well as their more resistant shells. As a result, our understanding of the Cambrian biology surpasses that of some later periods.
Phanerozoic
The Mesozoic ranges from 252 million to 66 million years ago. Also known as "the Age of the dinosaurs", the Mesozoic features the rise of reptiles on their 150 million year conquest of the Earth on the land, in the seas, and in the air. There are three periods in the Mesozoic: Triassic, Jurassic, and Cretaceous.
History of Earth
The Cryogenian period was followed by the Ediacaran period, which was characterized by a rapid development of new multicellular lifeforms. Whether there is a connection between the end of the severe ice ages and the increase in diversity of life is not clear, but it does not seem coincidental. The new forms of life, called Ediacara biota, were larger and more diverse than ever. Though the taxonomy of most Ediacaran life forms is unclear, some were ancestors of groups of modern life. Important developments were the origin of muscular and neural cells. None of the Ediacaran fossils had hard body parts like skeletons. These first appear after the boundary between the Proterozoic and Phanerozoic eons or Ediacaran and Cambrian periods.
Paleoproterozoic
Paleoproterozoic Era (;), 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.
Geological period
The twelve currently recognised periods of the present eon – the Phanerozoic – are defined by the International Commission on Stratigraphy (ICS) by reference to the stratigraphy at particular locations around the world.
Geology of Somaliland
Major Event III happened 700 to 640 million years ago, bringing crustal thinning and extension, mafic volcanism in the Abdulkadir complex and Mait complex, regional heating, metamorphism and the emplacement of gabbro and syenite through the thinned crust. Major Event IV continued for 100 million years, from 600 to 500 million years ago, spanning into the Paleozoic Era of the Phanerozoic Eon. Granites were emplaced and the deposition of the low-grade, metasedimentary Inda Ad sequence occurred, followed by more deformation and regional heating.
Paleocene–Eocene Thermal Maximum
Earth surface temperatures increased by about 6 °C from the late Paleocene through the early Eocene, culminating in the "Early Eocene Climatic Optimum" (EECO). Superimposed on this long-term, gradual warming were at least two (and probably more) "hyperthermals". These can be defined as geologically brief (<200,000 year) events characterized by rapid global warming, major changes in the environment, and massive carbon addition. Of these, the PETM was the most extreme and perhaps the first (at least within the Cenozoic). Another hyperthermal clearly occurred at approximately 53.7 Ma, and is now called ETM-2 (also referred to as H-1, or the Elmo event). However, additional hyperthermals probably occurred at about 53.6 Ma (H-2), 53.3 (I-1), 53.2 (I-2) and 52.8 Ma (informally called K, X or ETM-3). The number, nomenclature, absolute ages, and relative global impact of the Eocene hyperthermals are the source of considerable current research. Whether they only occurred during the long-term warming, and whether they are causally related to apparently similar events in older intervals of the geological record (e.g. the Toarcian turnover of the Jurassic) are open issues.
Changhsingian
The greatest mass extinction in the Phanerozoic eon, the Permian–Triassic extinction event, occurred during this age. The extinction rate peaked about a million years before the end of this stage.
Paleoclimatology
The constant rearrangement of continents by plate tectonics influences the long-term evolution of the atmosphere by transferring carbon dioxide to and from large continental carbonate stores. Free oxygen did not exist in the atmosphere until about 2.4 billion years ago, during the Great Oxygenation Event, and its appearance is indicated by the end of the banded iron formations. Until then, any oxygen produced by photosynthesis was consumed by oxidation of reduced materials, notably iron. Molecules of free oxygen did not start to accumulate in the atmosphere until the rate of production of oxygen began to exceed the availability of reducing materials. That point was a shift from a reducing atmosphere to an oxidizing atmosphere. O showed major variations until reaching a steady state of more than 15% by the end of the Precambrian. The following time span was the Phanerozoic eon, during which oxygen-breathing metazoan life forms began to appear.
Eocene
The Eocene is not only known for containing the warmest period during the Cenozoic, but it also marked the decline into an icehouse climate and the rapid expansion of the Antarctic ice sheet. The transition from a warming climate into a cooling climate began at ~49 million years ago. Isotopes of carbon and oxygen indicate a shift to a global cooling climate. The cause of the cooling has been attributed to a significant decrease of >2000 ppm in atmospheric carbon dioxide concentrations. One proposed cause of the reduction in carbon dioxide during the warming to cooling transition was the azolla event. The increased warmth at the poles, the isolated Arctic basin during the early Eocene, and the significantly high amounts of carbon dioxide possibly led to azolla blooms across the Arctic Ocean. The isolation of the Arctic Ocean led to stagnant waters and as the azolla sank to the sea floor, they became part of the sediments and effectively sequestered the carbon. The ability for the azolla to sequester carbon is exceptional, and the enhanced burial of azolla could have had a significant effect on the world atmospheric carbon content and may have been the event to begin the transition into an ice house climate. Cooling after this event continued due to continual decrease in atmospheric carbon dioxide from organic productivity and weathering from mountain building.
Neogene
The International Commission on Stratigraphy (ICS) once proposed that the Quaternary be considered a sub-era (sub-erathem) of the Neogene, with a beginning date of 2.58 Ma, namely the start of the Gelasian Stage. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs. The International Union for Quaternary Research (INQUA) counterproposed that the Neogene and the Pliocene end at 2.58 Ma, that the Gelasian be transferred to the Pleistocene, and the Quaternary be recognized as the third period in the Cenozoic, citing key changes in Earth's climate, oceans, and biota that occurred 2.58 Ma and its correspondence to the Gauss-Matuyama magnetostratigraphic boundary. In 2006 ICS and INQUA reached a compromise that made Quaternary a subera, subdividing Cenozoic into the old classical Tertiary and Quaternary, a compromise that was rejected by International Union of Geological Sciences because it split both Neogene and Pliocene in two.
Phanerozoic
The Carboniferous spans from 359 million to 299 million years ago. During this period, average global temperatures were exceedingly high: the early Carboniferous averaged at about 20 degrees Celsius (but cooled to 10 degrees during the Middle Carboniferous). Tropical swamps dominated the Earth, and the large amounts of trees created much of the carbon that became coal deposits (hence the name Carboniferous). The high oxygen levels caused by these swamps allowed massive arthropods, normally limited in size by their respiratory systems, to proliferate. Perhaps the most important evolutionary development of the time was the evolution of amniotic eggs, which allowed amphibians to move farther inland and remain the dominant vertebrates throughout the period. Also, the first reptiles and synapsids evolved in the swamps. Throughout the Carboniferous, there was a cooling pattern, which eventually led to the glaciation of Gondwana as much of it was situated around the south pole, in an event known as the Permo-Carboniferous glaciation or the Carboniferous Rainforest Collapse.
Phanerozoic
The Quaternary spans from 2.58 million years ago to present day, and is the shortest geological period in the Phanerozoic Eon. It features modern animals, and dramatic changes in the climate. It is divided into two epochs: the Pleistocene and the Holocene.
Geology of the Massif Central
At the beginning of the Cenozoic the Massif Central started to feel the effects of the pyrenean and the alpine orogeny, especially along its southern and eastern edges that were uplifted quite drastically. The consequences of these strong stresses on the crust initiated explosive volcanism already during the Paleocene. The volcanic activities have continued since then practically up to this day.
Phanerozoic
The Cambrian is the first period of the Paleozoic Era and starts from . The Cambrian sparked a rapid expansion in evolution in an event known as the Cambrian Explosion during which the greatest number of creatures evolved in a single period in the history of Earth. Plants like algae evolved, and the fauna was dominated by armored arthropods, such as trilobites. Almost all marine phyla evolved in this period. During this time, the super-continent Pannotia began to break up, most of which later recombined into the super-continent Gondwana.
Geology of Iran
In Iran the Cenozoic begins with the Cretaceous–Paleocene boundary that is characterized by striking changes in sedimentary environments (e.g., Alborz, Central Iran). An unconformity has been reported from many locations in Iran. Both continuous and discontinuous transitions have been discovered between Paleocene and Eocene strata; as is the case with Eocene and Oligocene (e.g., Central Iran). The Oligocene and Miocene stages are characterized by rapid subsidence, deposition, and facies changes in both marine and continental sedimentary basins (e.g., Mahneshan and Halab south of Zanjan). Oligocene sediments in most parts of Iran are of shallow marine character, turning into marine facies in Upper Oligocene through Lower Miocene (e.g., Qom). The Middle–Upper Miocene sediments are mostly of continental nature. The Quaternary is the prominent feature of the plains of Iran.
Archean
Instead of being based on stratigraphy, the beginning and end of the Archean Eon are defined chronometrically. The eon's lower boundary or starting point of 4 Gya (4 billion years ago) is officially recognized by the International Commission on Stratigraphy.
Geological history of Earth
The first-known glaciations occurred during the Proterozoic, one began shortly after the beginning of the eon, while there were at least four during the Neoproterozoic, climaxing with the Snowball Earth of the Varangian glaciation.
Pliocene
The Pliocene (; also Pleiocene) Epoch is the epoch in the geologic timescale that extends from 5.333 million to 2.58 million years BP. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch. Prior to the 2009 revision of the geologic time scale, which placed the four most recent major glaciations entirely within the Pleistocene, the Pliocene also included the Gelasian stage, which lasted from 2.588 to 1.806 million years ago, and is now included in the Pleistocene.