Ediacaran

From Wikipedia, the free encyclopedia

Ediacaran period

(millions of years ago)

<timeline> ImageSize = width:175 height:355 PlotArea = left:40 right:5 bottom:135 top:45 AlignBars = justify

Period = from:542 till:670 TimeAxis = orientation:vertical ScaleMajor = unit:year increment:25 start:550 ScaleMinor = unit:year increment:10 start:550

Colors =

 id:eon  value:rgb(1,0.7,1)  legend:Proterozoic_eon  # light purple
 id:era  value:rgb(1,1,0.7)  legend:Neoproterozoic_era   # light yellow
 id:period  value:rgb(1,0.7,0.7)  legend:Ediacaran_period  # light red
 id:black  value:black

Legend = left:15 top:60

BarData =

 bar:eon
 bar:era
 bar:period

PlotData=

 width:80 align:center textcolor:black mark:(line,black)

 bar:eon color:eon

 from:542  till:end  width:100  mark:none
 at:660  mark:none  text:Proterozoic~(542-2500)

 bar:era color:era

 from:542  till:650  width:100  mark:none
 at:640  mark:none  text:Neoproterozoic~(542-1000)

 bar:period color:period

 from:542  till:630  text:Ediacaran~(542-630)

TextData =

 tabs:(25-left)

 pos:(15,350)
 text:"Preceded by:"
 text:^Cryogenian period

 pos:(15,125)
 text:"Followed by:"
 text:^Phanerozoic eon,
 text:^Paleozoic era and
 text:^Cambrian period

</timeline> (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.