The Chibanian, widely known by its previous designation of Middle Pleistocene, is an
age in the international
geologic timescale or a
stage in
chronostratigraphy
Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time.
The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologic ...
, being a division of the
Pleistocene
The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
Epoch within the ongoing
Quaternary Period.
The Chibanian name was officially ratified in January 2020. It is currently estimated to span the time between 0.770
Ma (770,000 years ago) and 0.126 Ma (126,000 years ago), also expressed as 770–126 ka. It includes the transition in
palaeoanthropology from the
Lower to the
Middle Palaeolithic
The Middle Paleolithic (or Middle Palaeolithic) is the second subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. The term Middle Stone Age is used as an equivalent or a synonym for the Middle Pale ...
over 300 ka.
The Chibanian is preceded by the
Calabrian and succeeded by the proposed
Tarantian.
The beginning of the Chibanian is the
Brunhes–Matuyama reversal, when the Earth's magnetic field last underwent reversal. It ends with the onset of the
Eemian interglacial period (
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, along with consideration of a proposed
Anthropocene sub-division of the
Holocene
The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...
.
Definition process
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
is a prefecture of Japan located in the Kantō region of Honshu. Chiba Prefecture has a population of 6,278,060 (1 June 2019) and has a geographic area of . Chiba Prefecture borders Ibaraki Prefecture to the north, Saitama Prefecture to t ...
, 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.
The "Chibanian" name was ratified by the IUGS in January 2020.
Palaeoanthropology
The Chibanian includes the transition in
palaeoanthropology from the
Lower to the
Middle Palaeolithic
The Middle Paleolithic (or Middle Palaeolithic) is the second subdivision of the Paleolithic or Old Stone Age as it is understood in Europe, Africa and Asia. The term Middle Stone Age is used as an equivalent or a synonym for the Middle Pale ...
: i.e., the emergence of ''
Homo sapiens sapiens'' between 300 ka and 400 ka.
[.] The oldest known human DNA dates to the Middle Pleistocene, around 430,000 years ago. This is the oldest found, .
Chronology
See also
*
Mid-Pleistocene Transition
*
100,000-year problem
*
Pleistocene megafauna
References
{{Geological history, p, c
*02
Geological ages
Pleistocene geochronology
Cenozoic geochronology