|Subdivisions of the Quaternary System|
The Middle Pleistocene is a subdivision of the Pleistocene Epoch, from 781,000 to 126,000 years ago (781–126 ka). It is preceded by the Calabrian stage, beginning with the Brunhes–Matuyama reversal, and succeeded by the Tarantian stage (equivalent to the Late or Upper Pleistocene), taken as beginning with the last interglacial (MIS 5).
The tripartite subdivision of the Pleistocene into Lower (Early), Middle and Upper (Late) has been in use since the 1930s. It is in use as a provisional or "quasi-formal" designation by the International Union of Geological Sciences (IUGS) as of 2018, pending the ratification of the 2017 proposal by the International Commission on Stratigraphy (Subcommission on Quaternary Stratigraphy, ICSSQS) of the Chibanian stage.
The Middle Pleistocene contains the transition from the Lower to Middle Paleolithic in palaeoanthropology, i.e. the emergence of Homo sapiens at 300,000 years ago. The oldest known human DNA dates to the Middle Pleistocene.
Around 2000, the ICS Subcommission on Quaternary Stratigraphy had intended to formally divide the Pleistocene Epoch into three subepochs/subseries: the Early/Lower Pleistocene, the Middle Pleistocene and the Late/Upper Pleistocene. In 2009, however, the ICS's governing body (the IUGS), overruled this approach, preferring instead to divide the Pleistocene Epoch into four ages/stages. Some GSSP candidate sites were selected and informal names based on these locations were proposed. This resulted in the 2009 proposal that the Middle Pleistocene subepoch/subseries should be replaced by the Ionian age/stage, the start/base of which would be defined at a location in Italy.
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The Ionian stage includes all of the European Sicilian Stage and the first part of the Tyrrhenian Stage. Suitable sections for defining the base of the Ionian Stage are located in southern Italy. During Lower and Middle Pleistocene the Adriatic-Ionian margin was characterized by high sedimentation rates, in response to intense differential tectonic subsidence and massive sedimentary yield. Specifically, candidate sections are the “Montalbano Jonico” Section (Bradanic Trough, Basilicata Region) and the “Valle di Manche Nord” Section (San Mauro Marchesato, Crotone Basin, Calabria Region). In the former, a spectacular succession of marls laid in the Apennine foredeep is exposed which, however, are unfortunately unsuitable for magnetostratigraphic analyses. The latter, which is represented by a shallowing-upward succession that developed in an outer-shelf environment, has the bonus of a sharp biomagnetostratigraphic record, which provides tighter age control.
Besides these exposures, a number of Ocean Drilling Program cores drilled either in the Ionian Sea (Site 964) and in the Sicily Channel-Capo Rossello area (Site 963) are available, which correlate well with the on-land sections mentioned above based on a significant number of criteria (magnetostratigraphy, biostratigraphy, sapropel stratigraphy, stable isotopes and tephrochronology). The interval corresponding to the Ionian Stage is especially well represented in Site 963, where no turbidites and/or hiatuses are recognized. Presently, the Montalbano Ionico section is possibly the main candidate for defining the Lower - Middle Pleistocene boundary, when a reliable magnetostratigraphic record is found.
In November 2017, the Chibanian (defined at a site in Chiba Prefecture, Japan) replaced the Ionian as the Subcommission on Quaternary Stratigraphy's preferred GSSP proposal for the age/stage that should replace the Middle Pleistocene subepoch/subseries. Until the Chibanian is ratified by the IUGS, the Chibanian will remain an unofficial informal, proposed stratigraphic division and Middle Pleistocene remains the provisional or quasi-formal name used by the IUGS, for example on its International Chronostratigraphic Chart for 2018.
- Cohen, K.M.; Finney, S.C.; Gibbard, P.L.; Fan, J.-X. "International Chronostratigraphic Chart". International Commission on Stratigraphy. Retrieved July 10, 2018.
- "IUGS ratifies Holocene". Retrieved 18 August 2018.
- "announcement ICS chart v2018/07". Retrieved 9 August 2018.
- International Commission on Stratigraphy, ICS International Chronostratigraphic Chart 2018/02 (February 2018).. The chart uses "Middle" and "Upper" (printed in italics) as the younger two of three divisions of the Pleistocene, indicated as spanning 781–126 and 126–11.7 ka, respectively. The preceding division of the Pleistocene is labelled "Calabrian", spanning 1.80–0.781 Ma.
- Second International Quaternary Association (INQUA) Congress in Leningrad in 1932.
- "At present the SQS Working Group on the Lower-Middle Pleistocene Boundary is considering candidate sections in Italy and Japan, having resolved at the 32nd International Geological Congress in Florence in 2004 to place the boundary as close as possible to the MBB. The age of the MBB is estimated to be 781 ka in the astronomically tuned timescale. Italian workers have proposed an 'Ionian Stage' above the Calabrian Stage in Italian marine sections. The basal boundary of the 'Ionian Stage' is represented in two sections, Valle di Manche in Calabria and Montalbano Jonico in the central part of the Apennine foredeep. Both sequences have been correlated using multiple parameters, including calcareous nannofossil biochronology, palynology, isotope stratigraphy and tephrostratigraphy. The Montalbano Jonico section would represent the more suitable boundary stratotype , except that attempts to obtain a magnetostratigraphy from this section have been unsuccessful (Sagnotti et al. 2010). It is proposed that the Middle Pleistocene Subseries be comprised of a single stage – the Ionian Stage. A Working Group of the ICS Subcommission for Quaternary Stratigraphy is currently considering three candidate sections for the GSSP – the Montalbano Jonico and Valle di Manche sections in Italy and the Chiba section in Japan." "Formal subdivision of the Pleistocene Series/Epoch". Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy). 1 December 2010. Archived from the original on 2017-11-17. Retrieved 17 March 2018.
- Richter, D.et al. 2017 The Age of Hominin Fossils from Jebel Irhoud, Morocco, and the origins of the Middle Stone Age. Nature, Vol. 546 p. 293-296.
- "Japan-based name 'Chibanian' set to represent geologic age of last magnetic shift". The Japan Times. 14 November 2017. Retrieved 17 March 2018.
- Crew, Bec (2016-03-15). "The Oldest Human Genome Ever Has Been Sequenced, And It Could Rewrite Our History". ScienceAlert. Retrieved 5 June 2019.
- Middle Pleistocene at the GeoWhen database