Middle Pleistocene

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So far, the Pleistocene Series is not subdivided into formal units (i.e., Stages). Several solutions were proposed, and dedicated working groups are presently pursuing an agreed solution. Since the base of the Pleistocene is already pinned down at Vrica (Calabria, Southern Italy), only Middle and Upper Pleistocene are to be formally defined yet. Concerning the Middle Pleistocene, an agreement has been achieved by proposing the so-called “Ionian” Stage. Upon international agreement, the base of the Ionian Stage should be located close to the bottom of the Brunhes Chron, while its top would coincide with the base of the Upper Pleistocene, which in turn spans from the beginning of the last interglacial (i.e. Marine isotopic stage 5) to the base of the Holocene (~10.5 Ka). Especially suitable sections for defining the base of the Ionian stage are located in Southern Italy. In fact, 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 ODP 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, once a reliable magnetostratigraphic record is found.

[edit] References

• GeoWhen Database - Middle Pleistocene