Gelasian

Subdivisions of the Quaternary System
System	Series	Stage	Age (Ma)
Quaternary	Holocene		0–0.0117
	Pleistocene	Tarantian (Upper)	0.0117–0.126
		Ionian (Middle)	0.126–0.781
		Calabrian (Lower)	0.781–1.806
		Gelasian (Lower)	1.806–2.588
Neogene	Pliocene	Piacenzian	older
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 Gelasian is an age in the international geologic timescale or a stage in chronostratigraphy, being the earliest or lowest subdivision of the Quaternary period/system and Pleistocene epoch/series. It spans the time between 2.588 ± 0.005 Ma (million years ago) and 1.806 ± 0.005 Ma. It follows the Piacenzian stage (part of the Pliocene) and is followed by the Calabrian stage.

During the Gelasian the Red Crag of Butley and Newbourn and the Norwich and Weybourn Crags, all from East Anglia (England) were deposited. The Gelasian is an equivalent of the Praetiglian and Tiglian stages as defined in the Netherlands, which are commonly used in northwestern Europe.

Definition

The Gelasian was introduced in the geologic timescale in 1998. It is named after the Sicilian city of Gela in the south of the island. In 2009 it was moved^{[citation needed]} from the Pliocene to the Pleistocene in order that the geologic time scale be more consistent with the key changes in Earth's climate, oceans, and biota that occurred 2.588 million years ago.

The base of the Gelasian is defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone (at the Gauss-Matuyama magnetostratigraphic boundary), isotopic stage 103. Above this point there are notable extinctions of the calcareous nannofossils: Discoaster pentaradiatus and Discoaster surculus. The GSSP for the Gelasian is located at the Monte Sant Nicola near Gela.

The top of the Gelasian is defined magnetostratigraphically as the end of the Olduvai (C2n) chronozone, and faunally as the extinction level of the calcareous nannofossil Discoaster brouweri (base of biozone CN13). Above the Gelasian as the first occurrences of the calcareous nannofossil Gephyrocapsa sp. and the extinction level of the planktonic foraminifer Globigerinoides extremus.

During the Gelasian the ice sheets in the Northern Hemisphere began to grow, which is seen as the beginning of the Quaternary ice age.

References

Literature

• Gradstein, F.M.; Ogg, J.G. & Smith, A.G. (eds.) (2005) A Geologic Time Scale 2004 Cambridge University Press, Cambridge, UK, ISBN 0-521-78142-6.
• Rio, D., R. Sprovieri, D. Castradori, and E. Di Stefano, 1998. The Gelasian Stage (Upper Pliocene): A new unit of the global standard chronostratigraphic scale. Episodes, 21(2): 82-87.