Ediacaran

The Ediacaran period (about 635–541 million years BC), is 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 animals. These were impressions or trace fossils, first found in England's Charnwood Forest, Leicestershire.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. 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.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.

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.Knoll A.H. 2002. A new period for the geologic time scale. Science 305, 621.

 The Vendian 
The Ediacaran period was previously called the Vendian period. The Vendian period was proposed in 1952 by Russian geologist/paleontologist Boris Sokolov.Sokolov B. 1997. Essays on the advent of the Vendian System. KMK Scientific Press, Moscow. (in Russian) 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, which might have been a Snowball Earth. 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 (Treptichnus pedum) at the base of the Cambrian.A. Knoll et al. 2004. The Ediacaran period: a new addition to the geologic time scale.International Commission on Stratigraphy. 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.

No exact dating has been possible at the type section of the Ediacaran period in South Australia.

 Ediacaran biota 

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.

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