Chibanian

Chibanian
0.774 – 0.129 Ma
Chronology
Etymology
Name formalityFormal
Name ratifiedJanuary 2020
Synonym(s)Middle Pleistocene
Ionian
Usage information
Celestial bodyEarth
Regional usageGlobal (ICS)
Time scale(s) usedICS Time Scale
Definition
Chronological unitAge
Stratigraphic unitStage
Time span formalityFormal
Lower boundary definition1.1 m below the directional midpoint of the Brunhes-Matuyama magnetic reversal
Lower boundary GSSPChiba, Japan
35°17′39″N 140°08′47″E / 35.2943°N 140.1465°E / 35.2943; 140.1465
Lower GSSP ratifiedJanuary 2020[3]
Upper boundary definitionNot formally defined
Upper boundary definition candidatesMarine Isotope Substage 5e
Upper boundary GSSP candidate section(s)None
The Chibanian stratum, which dates back to the Chiba period, is located along the Yoro River in Ichihara City, Chiba Prefecture. At the bottom left is a golden spike that marks the boundary between eras. The color-coded stakes on the right mark the boundaries of geological formations, indicating that the Earth's magnetic field was reversing.

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]

  1. ^ 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.
  2. ^ 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.
  3. ^ "Global Boundary Stratotype Section and Point". International Commission of Stratigraphy. Retrieved 26 December 2020.
  4. ^ 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.
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.
  8. ^ 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.