| Chibanian | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Chronology | |||||||||
| |||||||||
| 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[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]
- ^ Cohen, K. M.; Finney, S. C.; Gibbard, P. L.; Fan, J.-X. (January 2020). "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. Retrieved 23 February 2020.
- ^ Mike Walker; et al. (December 2018). "Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period)" (PDF). Episodes. 41 (4). Subcommission on Quaternary Stratigraphy (SQS): 213–223. doi:10.18814/epiiugs/2018/018016. Retrieved 11 November 2019.
- ^ "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 26 December 2020.
- ^ Hornyak, Tim (30 January 2020). "Japan Puts Its Mark on Geologic Time with the Chibanian Age". Eos – Earth & Space Science News. American Geophysical Union. Retrieved 31 January 2020.
- ^ Cohen, K. M.; Finney, S. C.; Gibbard, P. L.; Fan, J.-X. (January 2020). "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. Retrieved 23 February 2020.
- ^ Gradstein, Felix M.; Ogg, James G.; Smith, Alan G., eds. (2004). A Geological Time Scale 2004 (3rd ed.). Cambridge: Cambridge University Press. p. 28. ISBN 9780521786737.
- ^ D. Dahl-Jensen & others (2013). "Eemian interglacial reconstructed from a Greenland folded ice core" (PDF). Nature. 493 (7433): 489–494. Bibcode:2013Natur.493..489N. doi:10.1038/nature11789. PMID 23344358. S2CID 4420908.
- ^ P. L. Gibbard (17 April 2015). "The Quaternary System/Period and its major sub-divisions". Russian Geology and Geophysics. Special Issue: Topical Problems of Stratigraphy and Evolution of the Biosphere. 56 (4). Elsevier BV: 686–688. Bibcode:2015RuGG...56..686G. doi:10.1016/j.rgg.2015.03.015. Retrieved 13 November 2019.