Gelasian

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.[3] It follows the Piacenzian stage (part of the Pliocene) and is followed by the Calabrian stage.

Subdivisions of the Quaternary Period
System/
Period		 Series/
Epoch		 Stage/
Age		 Age
Quaternary Holocene Meghalayan 0 4,200
Northgrippian 4,200 8,200
Greenlandian 8,200 11,700
Pleistocene 'Upper' 11,700 129ka
Chibanian 129ka 774ka
Calabrian 774ka 1.80Ma
Gelasian 1.80Ma 2.58Ma
Neogene Pliocene Piacenzian 2.58Ma 3.60Ma
Notes and references[1][2]
Subdivision of the Quaternary Period according to the ICS, as of January 2020.[1]

For the Holocene, dates are relative to the year 2000 (e.g. Greenlandian began 11,700 years before 2000). For the beginning of the Northgrippian a date of 8,236 years before 2000 has been set.[2] The Meghalayan has been set to begin 4,250 years before 2000.[1]

'Tarantian' is an informal, unofficial name proposed for a stage/age to replace the equally informal, unofficial 'Upper Pleistocene' subseries/subepoch.

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.

Definition

The Gelasian was introduced in the geologic timescale in 1998.[4] It is named after the Sicilian city of Gela in the south of the island. In 2009 it was moved from the Pliocene to the Pleistocene so that the geologic time scale would be more consistent with the key changes in Earth's climate, oceans, and biota that occurred 2.588 million years ago.[5]

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 line notable extinctions of the calcareous nanofossils occur: Discoaster pentaradiatus and Discoaster surculus.[3][6][4] 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 nanofossil Discoaster brouweri (base of biozone CN13). Above the Gelasian as the first occurrences of the calcareous nanofossil Gephyrocapsa sp. and the extinction level of the planktonic foraminifer Globigerinoides extremus.[3][7][4]

Climate

During the Gelasian the ice sheets in the Northern Hemisphere began to grow, which is seen as the beginning of the Quaternary ice age. Deep sea core samples have identified approximately 40 marine isotope stages (MIS 103 – MIS 64) during the age. Thus, there have probably been about 20 glacial cycles of varying intensity during the Gelasian.

Europe

In the regional glacial history of the Alps this age is now called Biber. It corresponds to Pre-Tegelen and Tegelen in Northern Europe.[8]

During the Gelasian, the Red Crag Formation of Butley, the Newbourn Crag, the Norwich Crag Formation and the Weybourne Crag Formation (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.

References

Notes
  1. Cohen, K. M.; Finney, S. C.; Gibbard, P. L.; Fan, J.-X. (January 2020). "International Chronostratigraphic Chart" (PDF). International Commission on Stratigraphy. Retrieved 23 February 2020.
  2. Mike Walker; et al. (December 2018). "Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period)" (PDF). Episodes. Subcommission on Quaternary Stratigraphy (SQS). 41 (4): 213–223. doi:10.18814/epiiugs/2018/018016. Retrieved 11 November 2019. This proposal on behalf of the SQS has been approved by the International Commission on Stratigraphy (ICS) and formally ratified by the Executive Committee of the International Union of Geological Sciences (IUGS).
  3. Gelasian at the GeoWhen database
  4. Rio, D., Sprovieri, R., Castradori, D., Di Stefano, E. "The Gelasian Stage (Upper Pliocene): A new unit of the global standard chronostratigraphic scale", Episodes, Vol. 21, No. 1, March 1998. pp 82-87. Retrieved March 18, 2020.
  5. Gibbard, Philip L.; Head, Martin J.; Walker, Michael J. C. (2009), "Formal ratification of the Quaternary System/Period and the Pleistocene Series/Epoch with a base at 2.58 Ma", Journal of Quaternary Science, 25 (2): 96, doi:10.1002/jqs.1338
  6. Gradstein et al. (2005), p. 28
  7. Gradstein et al. (2005)
  8. German Stratigraphic Commission: Stratigraphische Tabelle von Deutschland 2016

Literature
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