Concept information
Terme préférentiel
Gelasian
Définition
- 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 2.58 Ma (million years ago) and 1.80 Ma. It follows the Piacenzian Stage (part of the Pliocene) and is followed by the Calabrian Stage. 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 nannofossils occur: 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 nanofossil 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. 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. (Adapted from: https://en.wikipedia.org/wiki/Gelasian)
Concept générique
Traductions
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URI
http://data.loterre.fr/ark:/67375/QX8-XM8BBG7Z-5
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