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 [3] | ||||||||
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 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. [4] The Chibanian name was officially ratified in January 2020. It is currently estimated to span the time between 0.770 Ma (770,000 years ago) and 0.129 Ma (129,000 years ago), also expressed as 770–126 ka. 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 proposed Tarantian. [5] The beginning of the Chibanian is the Brunhes–Matuyama reversal, when the Earth's magnetic field last underwent reversal. [6] 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). [7]
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. [8]
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. [9] The "Chibanian" name was ratified by the IUGS in January 2020. [4]
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, [10] with the glacial cycles becoming asymmetric, having long glacial periods punctuated by short warm interglacial periods. [11] Millennial-scale climatic variability continued to be highly sensitive to precession and obliquity cycles. [12]
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. [13]
The Early-Middle Pleistocene boundary saw the migration of true horses out of North America and into Eurasia. [14] 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). [15] With the extinction of Sinomastodon in East Asia at the Early-Middle Pleistocene boundary, gomphotheres became completely extinct in Afro-Eurasia, [16] [17] but continued to persist in the Americas into the Late Pleistocene. [17] There was a major extinction of carnivorous mammals in Europe around the Early-Middle Pleistocene transition, including the giant hyena Pachycrocuta. [18] 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. [15] [19] 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. [20] 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. [21] Around 500,000 years ago, the last members of the largely European aquatic frog genus Palaeobatrachus and by extension the family Palaeobatrachidae became extinct. [22]
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. [23] The oldest known human DNA dates to the Middle Pleistocene, around 430,000 years ago. This is the oldest found, as of 2016 [update] . [24]
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. [25]
A mammoth is any species of the extinct elephantid genus Mammuthus. They lived from the late Miocene epoch into the Holocene about 4,000 years ago, and various species existed in Africa, Europe, Asia, 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), meaning "most", and καινός, meaning "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). It follows the Neogene Period and spans from 2.58 million years ago to the present. As of 2023, the Quaternary Period is divided into two epochs: the Pleistocene and the Holocene ; a third epoch, the Anthropocene, has recently been proposed, but it is not officially recognised by 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 some of the largest known species of elephants, over 4 metres (13 ft) tall at the shoulders, 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 only 1 metre (3.3 ft) in height, 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.
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.
The Hoxnian Stage was a middle Pleistocene stage of the geological history of the British Isles. It was an interglacial which preceded the Wolstonian Stage and followed the Anglian Stage. It is equivalent to Marine Isotope Stage 11. Marine Isotope Stage 11 started 424,000 years ago and ended 374,000 years ago. The Hoxnian is divided into sub-stages Ho I to Ho IV. It is likely equivalent to the Holstein Interglacial in Central Europe.
The Wolstonian Stage is a middle Pleistocene stage of the geological history of Earth from approximately 374,000 until 130,000 years ago. It precedes the Last Interglacial and follows the Hoxnian Stage in the British Isles.
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 Illinoian Stage is the name used by Quaternary geologists in North America to designate the Penultimate Glacial Period c.191,000 to c.130,000 years ago, during the late Middle Pleistocene (Chibanian), when sediments comprising the Illinoian Glacial Lobe were deposited. It precedes the Sangamonian Stage and follows the Pre-Illinoian Stage in North America. The Illinoian Stage is defined as the period of geologic time during which the glacial tills and outwash, which comprise the bulk of the Glasford Formation, accumulated to create the Illinoian Glacial Lobe. It occurs at about the same time as the penultimate glacial period.
During the Last Glacial Maximum, the mammoth steppe, also known as steppe-tundra, was once the Earth's most extensive biome. It stretched east-to-west, from the Iberian Peninsula in the west of Europe, across Eurasia to North America, through Beringia and Canada; from north-to-south, the steppe reached from the arctic islands southward to 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.
The straight-tusked elephant is an extinct species of elephant that inhabited Europe and Western Asia during the Middle and Late Pleistocene. One of the largest known elephant species, adult males are suggested to have reached 3.81–4.2 metres (12.5–13.8 ft) in shoulder height, and 11.3–15 tonnes in weight. Like modern elephants, the straight-tusked elephant lived in herds, flourishing during interglacial periods, when its range would extend as far north as Great Britain. Skeletons found in association with stone tools and wooden spears suggest they were scavenged and hunted by early humans, including Neanderthals. It is the ancestral species of most dwarf elephants that inhabited islands in the Mediterranean.
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-200,000 years ago. 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 1.5 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.
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.
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 occurred gradually, taking place approximately 1.25–0.7 million years ago, 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.