Gelasian
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| Subdivisions of the Quaternary period | |||
|---|---|---|---|
| System | Series | Stage | Age (Ma) |
| Quaternary | Holocene | 0–0.0117 | |
| Pleistocene | Tarantian (Upper) | 0.0117–0.126 | |
| Ionian (Middle) | 0.126–0.781 | ||
| Calabrian (Middle) | 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 a stage whose belonging to either the Pliocene or the Pleistocene Epochs is currently discussed. It spans the time between 2.588 ± 0.005 Ma (million years ago) and 1.806 ± 0.005 Ma.[1]. The Gelasian correlates with the period covering the deposition of the Red Crag of Butley and Newbourn and the Norwich and Weybourn Crags, all from East Anglia (England). Likewise the Gelasian is an equivalent of the Praetiglian and Tiglian stages as defined in the Netherlands.
The International Union for Quaternary Research (INQUA) has proposed that the Gelasian be moved 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 then (2.588 Ma) and corresponding to the Gauss-Matuyama magnetostratigraphic boundary.[2]
[edit] Boundaries
The beginning of the Gelasian is defined magnetostratigraphically as the base of the Matuyama (C2r) chronozone, isotopic stage 103. Above this point there are notable extinctions of the calcareous nannofossils: Discoaster pentaradiatus and Discoaster surculus.[1][3][4]
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. Above the Gelasian as the first occurrences of the calcareous nannofossil medium Gephyrocapsa spp. and the extinction level of the planktonic foraminifer Globigerinoides extremus.[1][5][4]
[edit] References
- ^ a b c GeoWhen Database - Gelasian December 2007, from Internet archive
- ^ Clague, John et al. (2006) "Open Letter by INQUA Executive Committee" Quaternary Perspective, the INQUA Newsletter International Union for Quaternary Research 16(1):
- ^ Gradstein, Felix M.; Ogg, James G. and Smith, A. Gilbert (eds.) (2005) A Geologic Time Scale 2004 Cambridge University Press, Cambridge, UK, p. 28, ISBN 0-521-78142-6
- ^ a b Rio, D.; Sprovieri, R.; Castradori, D. and Di Stefano, E. (1998) "The Gelasian Stage (Upper Pliocene): a new unit of the global standard chronostratigraphic scale" Episodes 21: pp. 82-87
- ^ Gradstein, Felix M.; Ogg, James G. and Smith, A. Gilbert (eds.) (2005) A Geologic Time Scale 2004 Cambridge University Press, Cambridge, UK, p. 66, ISBN 0-521-78142-6
| Neogene period | ||
|---|---|---|
| Quaternary | ||
| Pliocene | Pleistocene | Holocene |
| ← Neogene | Gelasian | Early | Middle | Late | |
