Middle Pleistocene
| Chibanian | |||||||||
|---|---|---|---|---|---|---|---|---|---|
The Chibanian Stratum, located at the Yoro River near Ichihara City, Japan | |||||||||
| 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″N 140°08′47″E / 35.2943°N 140.1465°E | ||||||||
| Lower GSSP ratified | January 2020 | ||||||||
| 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. 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. 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. The beginning of the Chibanian is the Brunhes–Matuyama reversal, when the Earth's magnetic field last underwent reversal. 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).
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.