Chibanian | |||||||||
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Chronology | |||||||||
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Etymology | |||||||||
Name formality | Formal | ||||||||
Name ratified | January 2020 | ||||||||
Synonym(s) | Middle Pleistocene Ionian | ||||||||
Usage information | |||||||||
Celestial body | Earth | ||||||||
Regional usage | Global (ICS) | ||||||||
Time scale(s) used | ICS Time Scale | ||||||||
Definition | |||||||||
Chronological unit | Age | ||||||||
Stratigraphic unit | Stage | ||||||||
Time span formality | Formal | ||||||||
Lower boundary definition | 1.1 m below the directional midpoint of the Brunhes-Matuyama magnetic reversal | ||||||||
Lower boundary GSSP | Chiba, Japan 35°17′39″N140°08′47″E / 35.2943°N 140.1465°E | ||||||||
Lower GSSP ratified | January 2020 [2] | ||||||||
Upper boundary definition | Not formally defined | ||||||||
Upper boundary definition candidates | Marine Isotope Substage 5e | ||||||||
Upper boundary GSSP candidate section(s) | None |
The Chibanian, more widely known as the Middle Pleistocene (its previous informal name), is an age in the international geologic timescale or a stage in chronostratigraphy, being a division of the Pleistocene Epoch within the ongoing Quaternary Period. [3] The Chibanian name was officially ratified in January 2020. It is currently estimated to span the time between 0.7741 Ma (774,100 years ago) and 0.129 Ma (129,000 years ago), also expressed as 774.1–129 ka. [1] [4] It includes the transition in palaeoanthropology from the Lower to the Middle Paleolithic over 300 ka.
The Chibanian is preceded by the Calabrian and succeeded by the Late Pleistocene. [1] The beginning of the Chibanian is the Brunhes–Matuyama reversal, when the Earth's magnetic field last underwent reversal. [5] Its end roughly coincides with the termination of the Penultimate Glacial Period and the onset of the Last Interglacial period (corresponding to the beginning of Marine Isotope Stage 5). [6]
The term Middle Pleistocene was in use as a provisional or "quasi-formal" designation by the International Union of Geological Sciences (IUGS). While the three lowest ages of the Pleistocene, the Gelasian, Calabrian and Chibanian have been officially defined, the Late Pleistocene has yet to be formally defined. [7]
The International Union of Geological Sciences (IUGS) had previously proposed replacement of the Middle Pleistocene by an Ionian Age based on strata found in Italy. In November 2017, however, the Chibanian (based on strata at a site in Chiba Prefecture, Japan) replaced the Ionian as the Subcommission on Quaternary Stratigraphy's preferred GSSP proposal for the age that should replace the Middle Pleistocene sub-epoch. [8] The "Chibanian" name was ratified by the IUGS in January 2020. [3]
By early Middle Pleistocene, the Mid-Pleistocene Transition had changed the glacial cycles from an average 41,000 year periodicity present during most of the Early Pleistocene to a 100,000 year periodicity, [9] with the glacial cycles becoming asymmetric, having long glacial periods punctuated by short warm interglacial periods. [10] Millennial-scale climatic variability continued to be highly sensitive to precession and obliquity cycles. [11]
In central Italy, the climate became noticeably more arid from 600 ka to 400 ka. [12]
The late Middle Pleistocene was a time of regional aridification in the Levant, with a shallow lake covering what is now the Shishan Marsh drying and developing into a marsh. [13]
Eastern Africa's hydroclimate was governed primarily by orbital precession, although modulated significantly by the 100 kyr eccentricity cycle. [14]
Along the northwestern Australian coast, the intensification of the Leeuwin Current resulted in an expansion of reefs coincident with the Great Barrier Reef's formation. [15]
The Early-Middle Pleistocene boundary saw the migration of true horses out of North America and into Eurasia. [16] Also around this time, the European mammoth species Mammuthus meridionalis became extinct and was replaced by the Asian species Mammuthus trogontherii (the steppe mammoth). This was coincident with the migration of the elephant genus Palaeoloxodon out of Africa and into Eurasia, including the first appearance of species like the European straight-tusked elephant (Palaeoloxodon antiquus). [17] With the extinction of Sinomastodon in East Asia at the Early-Middle Pleistocene boundary, gomphotheres became completely extinct in Afro-Eurasia, [18] [19] but continued to persist in the Americas into the Late Pleistocene. [19] There was a major extinction of carnivorous mammals in Europe around the Early-Middle Pleistocene transition, including the giant hyena Pachycrocuta. [20] The mid-late Middle Pleistocene saw the emergence of the woolly mammoth (Mammuthus primigenius), and its replacement of Mammuthus trogontherii, with the replacement of M. trogontherii in Europe by woolly mammoths being complete by around 200,000 years ago. [17] [21] The last member of the notoungulate family Mesotheriidae, Mesotherium , has its last records around 220,000 years ago, leaving Toxodontidae as the sole family of notoungulates to persist into the Late Pleistocene. [22] During the late Middle Pleistocene, around 195,000-135,000 years ago, the steppe bison (the ancestor of the modern American bison) migrated across the Bering land bridge into North America, marking the beginning of the Rancholabrean faunal stage. [23] Around 500,000 years ago, the last members of the largely European aquatic frog genus Palaeobatrachus and by extension the family Palaeobatrachidae became extinct. [24]
The Chibanian includes the transition in palaeoanthropology from the Lower to the Middle Paleolithic: i.e., the emergence of Homo sapiens sapiens between 300 ka and 400 ka. [25] The oldest known human DNA dates to the Middle Pleistocene, around 430,000 years ago. This is the oldest found, as of 2016 [update] . [26]
After analyzing 2,496 remains of Castor fiber (Eurasian beaver) and Trogontherium cuvieri found at Bilzingsleben in Germany, a team of scientists concluded that, around 400 ka, hominids in the area hunted and exploited beavers. They may have been targeted for their meat (based on cut marks on the bones) and skin. [27]
A mammoth is any species of the extinct elephantid genus Mammuthus. They lived from the late Miocene epoch into the Holocene until about 4,000 years ago, with mammoth species at various times inhabiting Africa, Asia, Europe, and North America. Mammoths are distinguished from living elephants by their spirally twisted tusks and in at least some later species, the development of numerous adaptions to living in cold environments, including a thick layer of fur.
The Pleistocene is the geological epoch that lasted from c. 2.58 million to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in 2009 by the International Union of Geological Sciences, the cutoff of the Pleistocene and the preceding Pliocene was regarded as being 1.806 million years Before Present (BP). Publications from earlier years may use either definition of the period. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology. The name is a combination of Ancient Greek πλεῖστος (pleîstos) 'most' and καινός 'new'.
The Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the Phanerozoic eon. It follows the Neogene Period and spans from 2.58 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene ; a proposed third epoch, the Anthropocene, was rejected in 2024 by IUGS, the governing body of the ICS.
Elephantidae is a family of large, herbivorous proboscidean mammals collectively called elephants and mammoths. These are large terrestrial mammals with a snout modified into a trunk and teeth modified into tusks. Most genera and species in the family are extinct. Only two genera, Loxodonta and Elephas, are living.
Palaeoloxodon is an extinct genus of elephant. The genus originated in Africa during the Early Pleistocene, and expanded into Eurasia at the beginning of the Middle Pleistocene. The genus contains the largest known species of elephants, over 4 metres (13 ft) tall at the shoulders and over 13 tonnes (29,000 lb) in weight, representing among the largest land mammals ever, including the African Palaeoloxodon recki, the European straight-tusked elephant and the South Asian Palaeoloxodon namadicus. P. namadicus has been suggested to be the largest known land mammal by some authors based on extrapolation from fragmentary remains, though these estimates are highly speculative. In contrast, the genus also contains many species of dwarf elephants that evolved via insular dwarfism on islands in the Mediterranean, some like Palaeoloxodon falconeri less than 1 metre (3.3 ft) in shoulder height as fully grown adults, making them the smallest elephants known. The genus has a long and complex taxonomic history, and at various times, it has been considered to belong to Loxodonta or Elephas, but today is usually considered a valid and separate genus in its own right.
There have been five or six major ice ages in the history of Earth over the past 3 billion years. The Late Cenozoic Ice Age began 34 million years ago, its latest phase being the Quaternary glaciation, in progress since 2.58 million years ago.
Gomphotheres are an extinct group of proboscideans related to modern elephants. First appearing in Africa during the Oligocene, they dispersed into Eurasia and North America during the Miocene and arrived in South America during the Pleistocene as part of the Great American Interchange. Gomphotheres are a paraphyletic group ancestral to Elephantidae, which contains modern elephants, as well as Stegodontidae.
Dwarf elephants are prehistoric members of the order Proboscidea which, through the process of allopatric speciation on islands, evolved much smaller body sizes in comparison with their immediate ancestors. Dwarf elephants are an example of insular dwarfism, the phenomenon whereby large terrestrial vertebrates that colonize islands evolve dwarf forms, a phenomenon attributed to adaptation to resource-poor environments and lack of predation and competition.
Panthera spelaea, commonly known as the cave lion, is an extinct Panthera species that was native to Eurasia and northwest North America during the Pleistocene epoch. Genetic analysis of ancient DNA has revealed that while closely related, it was a distinct species genetically isolated from the modern lion, with the genetic divergence between the two species estimated at around 500,000 years ago. The earliest fossils of the P. spelaea lineage in Eurasia date to around 700,000 years ago. It is closely related and probably ancestral to the American lion. The species ranged from Western Europe to eastern Beringia in North America, and was a prominent member of the mammoth steppe fauna, and an important apex predator across its range. It became extinct about 13,000 years ago. It closely resembled living lions with a coat of yellowish-grey fur though unlike extant lions, males appear to have lacked manes.
The pygmy mammoth or Channel Islands mammoth is an extinct species of dwarf mammoth native to the northern Channel Islands off the coast of southern California during the Late Pleistocene. It was descended from the Columbian mammoth of mainland North America, which are suggested to have colonised the islands around 250–150,000 years ago. At only 1.72–2.02 m (5.6–6.6 ft) tall at the shoulder, it was around 17% the size of its mainland ancestor. The species became extinct around 13,000 years ago, co-inciding with major environmental change and the arrival of humans in the Channel islands.
The Columbian mammoth is an extinct species of mammoth that inhabited North America from southern Canada to Costa Rica during the Pleistocene epoch. The Columbian mammoth descended from Eurasian steppe mammoths that colonised North America during the Early Pleistocene around 1.5–1.3 million years ago, and later experienced hybridisation with the woolly mammoth lineage. The Columbian mammoth was among the last mammoth species, and the pygmy mammoths evolved from them on the Channel Islands of California. The closest extant relative of the Columbian and other mammoths is the Asian elephant.
The mammoth steppe, also known as steppe-tundra, was once the Earth's most extensive biome. During glacial periods in the later Pleistocene it stretched east-to-west, from the Iberian Peninsula in the west of Europe, then across Eurasia and through Beringia and into the Yukon in northwest Canada; from north-to-south, the steppe reached from the Arctic southward to southern Europe, Central Asia and northern China. The mammoth steppe was cold and dry, and relatively featureless, though climate, topography, and geography varied considerably throughout. Certain areas of the biome—such as coastal areas—had wetter and milder climates than others. Some areas featured rivers which, through erosion, naturally created gorges, gulleys, or small glens. The continual glacial recession and advancement over millennia contributed more to the formation of larger valleys and different geographical features. Overall, however, the steppe is known to be flat and expansive grassland. The vegetation was dominated by palatable, high-productivity grasses, herbs and willow shrubs.
The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as the Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently defined as the time between c. 129,000 and c. 11,700 years ago. The late Pleistocene equates to the proposed Tarantian Age of the geologic time scale, preceded by the officially ratified Chibanian. The beginning of the Late Pleistocene is the transition between the end of the Penultimate Glacial Period and the beginning of the Last Interglacial around 130,000 years ago. The Late Pleistocene ends with the termination of the Younger Dryas, some 11,700 years ago when the Holocene Epoch began.
Mammuthus meridionalis, sometimes called the southern mammoth, is an extinct species of mammoth native to Eurasia, including Europe, during the Early Pleistocene, living from around 2.5 million years ago to 800,000 years ago.
Mammuthus trogontherii, sometimes called the steppe mammoth, is an extinct species of mammoth that ranged over most of northern Eurasia during the Early and Middle Pleistocene, approximately 1.7 million to 200,000 years ago. The evolution of the steppe mammoth marked the initial adaptation of the mammoth lineage towards cold environments, with the species probably being covered in a layer of fur. One of the largest mammoth species, it evolved in East Asia during the Early Pleistocene, around 1.8 million years ago, before migrating into North America around 1.3 million years ago, and into Europe during the Early/Middle Pleistocene transition, around 1 to 0.7 million years ago. It was the ancestor of the woolly mammoth and Columbian mammoth of the later Pleistocene.
The woolly mammoth is an extinct species of mammoth that lived from the Middle Pleistocene until its extinction in the Holocene epoch. It was one of the last in a line of mammoth species, beginning with the African Mammuthus subplanifrons in the early Pliocene. The woolly mammoth began to diverge from the steppe mammoth about 800,000 years ago in Siberia. Its closest extant relative is the Asian elephant. The Columbian mammoth lived alongside the woolly mammoth in North America, and DNA studies show that the two hybridised with each other. Mammoth remains had long been known in Asia before they became known to Europeans. The origin of these remains was long a matter of debate and often explained as being remains of legendary creatures. The mammoth was identified as an extinct species of elephant by Georges Cuvier in 1796.
The Pre-Illinoian Stage is used by Quaternary geologists for the early and middle Pleistocene glacial and interglacial periods of geologic time in North America from ~2.5–0.2 Ma.
The Early Pleistocene is an unofficial sub-epoch in the international geologic timescale in chronostratigraphy, representing the earliest division of the Pleistocene Epoch within the ongoing Quaternary Period. It is currently estimated to span the time between 2.580 ± 0.005 Ma and 0.773 ± 0.005 Ma. The term Early Pleistocene applies to both the Gelasian Age and the Calabrian Age.
Villafranchian age is a period of geologic time spanning the Late Pliocene and Early Pleistocene used more specifically with European Land Mammal Ages. Named by Italian geologist Lorenzo Pareto for a sequence of terrestrial sediments studied near Villafranca d'Asti, a town near Turin, it succeeds the Ruscinian age, and is followed by the Galerian.
The Mid-Pleistocene Transition (MPT), also known as the Mid-Pleistocene Revolution (MPR), is a fundamental change in the behaviour of glacial cycles during the Quaternary glaciations. The transition lasted around 550,000 years, from 1.25 million years ago until 0.7 million years ago approximately, in the Pleistocene epoch. Before the MPT, the glacial cycles were dominated by a 41,000-year periodicity with low-amplitude, thin ice sheets, and a linear relationship to the Milankovitch forcing from axial tilt. Because of this, sheets were more dynamic during the Early Pleistocene. After the MPT there have been strongly asymmetric cycles with long-duration cooling of the climate and build-up of thick ice sheets, followed by a fast change from extreme glacial conditions to a warm interglacial. This led to less dynamic ice sheets. Interglacials before the MPT had lower levels of atmospheric carbon dioxide compared to interglacials after the MPT. One of the MPT's effects was causing ice sheets to become higher in altitude and less slippery compared to before. The MPT greatly increased the reservoirs of hydrocarbons locked up as permafrost methane or methane clathrate during glacial intervals. This led to larger methane releases during deglaciations. The cycle lengths have varied, with an average length of approximately 100,000 years.