|Subdivisions of the Quaternary System|
|Subdivision of the Quaternary period
according to the ICS, as of 2017.
In Europe and North America, the Holocene is subdivided into Preboreal, Boreal, Atlantic, Subboreal, and Subatlantic stages of the Blytt-Sernander time scale. There are many regional subdivisions for the Upper or Late Pleistocene; usually these represent locally recognized cold (glacial) and warm (interglacial) periods. The last glacial period ends with the cold Younger Dryas substage.
The Middle Pleistocene, more specifically referred to as the Ionian stage, is a period of geologic time from ca. 781 to 126 thousand years ago.
The base of the Ionian Stage succeeds the Calabrian Stage (the beginning of the Brunhes-Matuyama reversal) and precedes the Tarantian Stage or Upper Pleistocene, which in turn spans from the beginning of the last interglacial (Marine isotopic stage 5) to the base of the Holocene (~10.5 ka).
Although experts are not yet in agreement on how to subdivide the stages of the Pleistocene epoch, a possible international consensus on one subdivision called the Ionian Stage exists. 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, 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. The oldest known human's DNA dates to the Middle Pleistocene era.