Members of the International Commission on Stratigraphy (ICS) have controversially discussed the Redefinition of Quaternary, Pleistocene, Neogene, and Pliocene during the last months. The discussion was initiated by the ICS to find a definete agreement on the structure of upper part of the International Stratigraphic Chart (See one of my older posts on the 'prelude' of this issue).
The ICS has proposed three scenarios to vote on in a first round:
The Quaternary proposal received the majority of votes in this first round. The results of the following second round of voting which only included the Quaternary proposal have recently been published here.
- “Status Quo” Proposal: Pleistocene Series/Epoch remains defined by Vrica GSSP. The base of the Quaternary System/Period is formally defined also by the Vrica GSSP, corresponding to the base of the Pleistocene Series/Epoch and Calabrian Stage/Age, and serving also as the Neogene-Quaternary boundary.
- “Quaternary” Proposal: Base of Pleistocene Series/Epoch is lowered such that the Pleistocene includes the Gelasian Stage/Age and its base is defined by the Monte San Nicola GSSP, which also defines the base of the Gelasian. In addition, the base of the Quaternary System/Period, and thus the Neogene-Quaternary boundary, is formally defined by Monte San Nicola GSSP and is coincident with the bases of the Pleistocene and Gelasian. With these definitions the Gelasian Stage/Age is transferred from the Pliocene Series/Epoch to the Pleistocene.
- “Neogene” Proposal: Pleistocene Series/Epoch remains defined by Vrica GSSP. The Pliocene Series/Epoch is split into two series/epochs named Lower/Early Pliocene and Upper/Late Pliocene, with the later composed of the Gelasian Stage/Age and with its base defined by the Monte San Nicola GSSP. The rank of the Quaternary is changed from system/period to subsystem/subperiod; its base is formally defined by the Monte San Nicola GSSP. As a result, the Quaternary is composed of the Upper/Late Pliocene, Pleistocene, and Holocene series/epochs. The Neogene System/Period extends upwards such that it includes the Miocene, Lower/Early Pliocene, Upper/Late Pliocene, Pleistocene, and Holocene series/epochs.
And the winner is ... the Quaternary is back! The proposal received a 89% majority of yes votes. The proposal will now be forwarded to the IUGS Executive Committee for ratification.
An exciting documentation on this historic discussion can be found on the new bulletin board of the International Stratigraphic Comission.