Ediacaran

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Ediacaran period
Geologic timescale of the Precambrian
(millions of years ago)
(expand)

The Ediacaran Period (from the Ediacara Hills of South Australia) is the last geological period of the Neoproterozoic Era, just before the Cambrian. It ranges from approximately 635 to 542 million years before the present. Historically this name has been variously used by researchers, but its status as an official geological period was ratified in March 2004 by the International Union of Geological Sciences (IUGS) and announced on May 13, 2004, the first new such period declared in 120 years. It was also called the Vendian period; this name arose in Russia.

The animal fossil record from this era is sparse, possibly because animals had yet to evolve hard shells, which make for easier fossilization.

1 Ediacaran dating
2 Ediacaran biota
3 References
4 External links

[edit] Ediacaran dating

The period is unusual because its beginning is not defined by a change in the fossil record. Unusual soft bodied fossils do occur in the Ediacaran Period, but these are limited to the latter parts of the Period, after about 580 million years ago. Rather, the beginning is defined by the appearance of a new texturally and chemically distinctive carbonate layer that indicates a climatic change (the end of a global ice age). There is an unusual depletion of ¹³C that marks the end of the global ice ages of the preceding Cryogenian period. The date of the boundary is fairly well constrained at 635 million years ago based on U-Pb (uranium-lead) dates from Namibia and China.