Ediacaran
| Supereon | Eon | Era | Period | Start Million years ago |
|---|---|---|---|---|
| Phanerozoic | Palaeozoic | Cambrian | 0541 | |
| Precambrian | Proterozoic | Neoproterozoic | Ediacaran | 0635 |
| Cryogenian | 0850 | |||
| Tonian | 1000 | |||
| Mesoproterozoic | 1600 | |||
| Palaeoproterozoic | 2500 | |||
| Archaean | 4000 | |||
| Hadean | 4567 | |||
The Ediacaran period (about 635–541 million years ago),[1] was named after the Ediacara Hills of South Australia. It is the last geological period of the Proterozoic Eon. The Edicaran is followed by the Cambrian, the first period of the Palaeozoic Era and the Phanerozoic Eon.
The period is famous for the first larger-bodied fossils, which are probably the first recorded metazoans. These were trace fossils, first found in England's Charnwood Forest, Leicestershire.[2][3] They did not know what it was that they had found, and it was over 60 years later before fossils from the same period were found in South Australia.[4][5]
The status of the Ediacaran as an official geological period was confirmed in 2004 by the International Union of Geological Sciences (IUGS). This made it the first new geological period declared in 120 years.[6]
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The Vendian [change]
The Ediacaran period was previously called the Vendian period. The Vendian period was proposed in 1952 by Russian geologist/paleontologist Boris Sokolov.[7][8] The term Vendian is still widely used.
The two terms are not the same. The Vendian was a longer period: it included the whole of the Marinoan glaciation, of Snowball Earth fame. In other words, the Vendian included the last part of the Cryogenian period.
Borders of the Ediacaran [change]
The Ediacaran Period represents the time from the end of global Marinoan glaciation to the first appearance worldwide of certain trace fossils (Trichophycus pedum) at the base of the Cambrian.[9] Although the Ediacaran period does contain soft-bodied fossils (the Ediacaran biota), its start is defined at the base of a carbonate layer, referred to as a "cap carbonate". This caps glacial deposits and shows a sudden climatic change at the end of the Marinoan ice age.
The Ediacaran lasts for about 90 million years, of which only the last 50 million years show the soft-bodied fossils. The period starts with the end of the 200-million year long Cryogenian (Snowball Earth) period. Between that and the fossils comes another severe but short glacial period known as the Gaskiers glaciation.
The period ends with the mass extinction of virtually all the Ediacaran fauna: Cambrian fauna are quite different. The causes of this extinction are poorly understood.
Related pages [change]
References [change]
- ↑ International Chronostratigraphic Chart. [1]
- ↑ Hill E & Bonner T.G. 1877. The PreCarboniferous rocks of Charnwood Forest. Q.J. Geol Soc. 33, 754-789.
- ↑ Bottjer, David J. 2002. Enigmatic Ediacara fossils: ancestors or aliens? In Bottjer et al. (eds) Exceptional fossil preservation: a unique view on the evolution of marine life. Columbia, N.Y.
- ↑ Sprigg R.C. 1947. Early Cambrian (?) jellyfish from the Flinders Ranges, South Australia. Trans Roy Soc South Australia 71, 212-224.
- ↑ Glaessner M.F. 1984. The dawn of animal life: a biohistorical study. Cambridge.
- ↑ Knoll A.H. 2002. A new period for the geologic time scale. Science 305, 621.
- ↑ Sokolov B. (1952). "On the age of the old sedimentary cover of the Russian Platform". Izvestiya Akademii Nauk SSSR, Seriya eologicheskaya 5: 21–31.
- ↑ Sokolov B. 1997. Essays on the advent of the Vendian System. KMK Scientific Press, Moscow. (in Russian)
- ↑ A. Knoll, M. Walter, G. Narbonne, and N. Christie-Blick 2004. The Ediacaran Period: a new addition to the geologic time scale. Submitted on behalf of the Terminal Proterozoic Subcommission of the International Commission on Stratigraphy.
| Precambrian (4.567 gya – 541 mya) | |
|---|---|
| In the left column are Eons, bold are Eras, not bold are Periods. gya = billion years ago, mya = million years ago | |
| Hadean (4.567 gya – 4 gya) | |
| Archaean (4 gya – 2.5 gya) | |
| Proterozoic (4 gya – 2.5 gya) | Palaeoproterozoic (2.5 gya – 1.6 gya)
Mesoproterozoic (1.6 gya – 1 gya) Neoproterozoic (1 gya - 541 mya) Tonian (1 gya – 850 mya) Cryogenian (850 mya – 635 mya) Ediacaran (635 mya – 541 mya) |
| Source | International Chronostratigraphic Chart 2013. International Commission on Stratigraphy, retrieved 8 April 2013. Divisions of geologic time – major chronostratigraphic and geochronologic units USGS, retrieved 8 April 2013. |
