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The Ediacaran period (about 635–541 million years ago), 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.
The period is famous for the first larger-bodied fossils, which are probably the first recorded metazoans. These were impressions or trace fossils, first found in England's Charnwood Forest, Leicestershire. Geologists did not know what they had found. It was over 60 years later before fossils from the same period were found in South Australia.
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.
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
The Ediacaran lasted for about 90 million years. It began at the end of the Cryogenian Snowball Earth. It ended with the first appearance worldwide of some kinds of trace fossils (Trichophycus pedum) at the base of the Cambrian. The Ediacaran period's 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 period ended with the mass extinction of almost all the Ediacaran fauna.
The Ediacaran biota include the oldest definite multicellular organisms. The fossils are traces or impressions of soft-bodies forms with segments, fronds, disks, or bags. Skeletons or shells are not found.
- 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 et al 2004. The Ediacaran period: a new addition to the geologic time scale.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)||Chaotian||Zirconian||Archaean (4 gya – 2.5 gya)||Eoarchaean (4 gya – 3.6 gya)|
|Proterozoic (4 gya – 2.5 gya)||Palaeoproterozoic (2.5 gya – 1.6 gya) Siderian (2.5 gya – 2.3 gya) Rhyacian (2.3 gya – 2.05 gya) Orosirian (2.05 gya – 1.8 gya) Statherian (1.8 gya – 1.6 gya)|
|Phanerozoic (541 mya – today)|
|In the left column are Eras, bold are Periods, not bold or italics are Epochs, Italics are stages. kya = thousand years ago, mya = million years ago|
|Palaeozoic (541 mya – 252.17 mya)||Cambrian (541 mya – 485.4 mya)|
|Mesozoic (252.17 mya – 66.0 mya)||Triassic (252.17 mya – 201.3 mya) Lower Triassic (252.17 mya – 247.2 mya) Middle Triassic (247.2 mya – 237 mya) Upper Triassic (237 mya – 201.3 mya)|
|Cainozoic (66.0 mya – today)||Palaeogene (66.0 mya – 23.03 mya) Palaeocene (66.0 mya – 56 mya) Eocene (56 mya - 33.9 mya) Oligocene (33.9 mya – 23.03 mya)|