The EDIACARAN Period ( /iːdiˈækərən/ ), spans 94 million years
from the end of the
Cryogenian Period 635 million years ago (Mya), to
the beginning of the
Cambrian Period 541 Mya. It marks the end of the
Proterozoic Eon , and the beginning of the
Phanerozoic Eon . It is
named after the
Ediacara Hills of
South Australia .
Ediacaran Period's status as an official geological period was
ratified in 2004 by the International Union of Geological Sciences
(IUGS), making it the first new geological period declared in 120
years. Although the Period takes its name from the Ediacara Hills
Reg Sprigg first discovered fossils of the eponymous
Ediacara biota in 1946, the type section is located in the bed of the
Enorama Creek within Brachina Gorge in the
Flinders Ranges of South
Australia , at 31°19′53.8″S 138°38′0.1″E /
31.331611°S 138.633361°E / -31.331611; 138.633361 .
Ediacaran and Vendian
* 2 Upper and lower boundaries
* 3 Subdivisions
* 5 Biota
* 6 Astronomical factors
* 7 Documentaries
* 8 See also
* 9 References
* 10 External links
EDIACARAN AND VENDIAN
Ediacaran Period overlaps, but is shorter than the VENDIAN
Period, a name that was earlier, in 1952, proposed by Russian
geologist and paleontologist Boris Sokolov . The Vendian concept was
formed stratigraphically top-down, and the lower boundary of the
Cambrian became the upper boundary of the Vendian.
Paleontological substantiation of this boundary was worked out
separately for the siliciclastic basin (base of the Baltic Stage of
the Eastern European Platform ) and for the carbonate basin (base of
Tommotian Stage of the
Siberian Platform ). The lower boundary of
the Vendian was suggested to be defined at the base of the Varanger
(Laplandian ) tillites .
The Vendian in its type area consists of large subdivisions such as
Redkino , Kotlin and
Rovno Regional stages with the
globally traceable subdivisions and their boundaries, including its
The Redkino, Kotlin and
Rovno regional stages have been substantiated
in the type area of the Vendian on the basis of the abundant
organic-walled microfossils , megascopic algae, metazoan body fossils
and ichnofossils .
The lower boundary of the Vendian could have a biostratigraphic
substantiation as well taking into consideration the worldwide
occurrence of the Pertatataka assemblage of giant acanthomorph
UPPER AND LOWER BOUNDARIES
The 'golden spike' (bronze disk in the lower section of the
image) or 'type section' of the Global Boundary Stratotype Section and
Point (GSSP) for the base of
Ediacaran period. The 'golden
spike' marking the
GSSP Elatina Fm diamictite below Ediacaran
GSSP site in the
Flinders Ranges NP , South Australia. A$1 coin for
Ediacaran Period (ca. 635-542 Mya) represents the time from the
end of global
Marinoan glaciation to the first appearance worldwide of
somewhat complicated trace fossils (
Treptichnus pedum (Seilacher,
Ediacaran Period does contain soft-bodied fossils , it
is unusual in comparison to later periods because its beginning is not
defined by a change in the fossil record. Rather, the beginning is
defined at the base of a chemically distinctive carbonate layer that
is referred to as a "cap carbonate ," because it caps glacial
This bed is characterized by an unusual depletion of 13C that
indicates a sudden climatic change at the end of the
Marinoan ice age
. The lower boundary
GSSP of the
Ediacaran is at the base of the cap
carbonate (Nuccaleena Formation), immediately above the Elatina
diamictite in the Enorama Creek section, Brachina Gorge, Flinders
Ranges, South Australia.
GSSP of the upper boundary of the
Ediacaran is the lower boundary
Cambrian on the SE coast of Newfoundland approved by the
International Commission on Stratigraphy as a preferred alternative to
the base of the
Tommotian Stage in
Siberia which was selected on the
basis of the ichnofossil
Treptichnus pedum (Seilacher, 1955). In the
history of stratigraphy it was the first case of usage of
bioturbations for the System boundary definition.
Nevertheless, the definitions of the lower and upper boundaries of
Ediacaran on the basis of chemostratigraphy and ichnofossils are
Cap carbonates generally have a restricted geographic distribution
(due to specific conditions of their precipitation) and usually
siliciclastic sediments laterally replace the cap carbonates in a
rather short distance but cap carbonates do not occur above every
tillite elsewhere in the world.
The C-isotope chemostratigraphic characteristics obtained for
contemporaneous cap carbonates in different parts of the world may be
variable in a wide range owing to different degrees of secondary
alteration of carbonates, dissimilar criteria used for selection of
the least altered samples, and, as far as the C-isotope data are
concerned, due to primary lateral variations of δ l3Ccarb in the
upper layer of the ocean.
Furthermore, Oman presents in its stratigraphic record a large
negative carbon isotope excursion, within the Shuram Formation that
is clearly away from any glacial evidence strongly questioning
systematic association of negative δ l3Ccarb excursion and glacial
events. Also, the Shuram excursion is prolonged and is estimated to
last for ~9.0 Myrs.
As to the Treptichnus pedum, a reference ichnofossil for the lower
boundary of the Cambrian, its usage for the stratigraphic detection of
this boundary is always risky, because of the occurrence of very
similar trace fossils belonging to the Treptichnids group well below
the level of T. pedum in
Spain and Newfoundland , and
possibly, in the western United States . The stratigraphic range of T.
pedum overlaps the range of the
Ediacaran fossils in Namibia, and
probably in Spain.
Ediacaran period is not yet formally subdivided, but a proposed
scheme recognises an Upper
Ediacaran whose base corresponds with the
Gaskiers glaciation , a Terminal
Ediacaran Stage starting around 550
million years ago, a preceding stage beginning around 557 Ma with the
Ediacaran biota fossils; two proposed schemes
differ on whether the lower strata should be divided into an Early and
Ediacaran or not, because it's not clear whether the Shuram
excursion (which would divide the Early and Middle) is a separate
event from the Gaskiers, or whether the two events are correlated.
The dating of the rock type section of the
Ediacaran Period in South
Australia has proven uncertain. Therefore, the age range of 635 to 542
million years is based on correlations to other countries where dating
has been possible. The base age of approximately 635 million years is
based on U-Pb (uranium -lead ) isochron dating from
Applying this age to the base of the
Ediacaran assumes that cap
carbonates are laid down synchronously around the world and that the
correct cap carbonate layers have been selected in such diverse locals
as Australian and Namibia. This is controversial because an age of
about 580 million years has been obtained for glacial rocks in
Tasmania which some scientists tentatively assign to those just
Ediacaran rocks of the Flinders Ranges. The age of the
top is the same as the widely recognised age for the base of the
Cambrian Period 542± 0.3 Mya, producing a misalignment, as the end
of the Edicarian Period should mark the start of the
The fossil record from the
Ediacaran Period is sparse, as more easily
fossilized hard-shelled animals had yet to evolve. The
include the oldest definite multicellular organisms (with specialized
tissues), the most common types of which resemble segmented worms,
fronds, disks, or immobile bags.
Ediacara biota bear little resemblance to modern lifeforms, and their
relationship even with the immediately following lifeforms of the
Cambrian explosion is rather difficult to interpret. More than 100
genera have been described, and well known forms include
Marywadea , Onega ,
There is evidence that Earth's first mass extinction happened during
this period when early animals changed the environment.
The relative proximity of the Moon at this time meant that tides were
stronger and more rapid than they are now. The day was 21.9±0.4
hours, and there were 13.1±0.1 synodic months/year and 400±7 solar
A few English language documentaries have featured the Ediacaran
period and biota:
* The Time Traveller\'s Guide To Australia (2012, ABC Network
Australia; Part 1 of 4).
* The Geological History of Canada, as part of The Nature of Things
series, CBC-SRC; 2011; Eastern Canada.
* The first episode of a BBC documentary titled Life on Earth , with
David Attenborough as narrator.
* Another documentary narrated by
David Attenborough titled First
Funisia , and
Kimberella animated in CGI .
* BBC podcast - In our time - Edicara Biota - 9 July 2009 -
List of fossil sites (with link directory)
* ^ Image:Sauerstoffgehalt-1000mj.svg
* ^ File:OxygenLevel-1000ma.svg
* ^ Image:Phanerozoic
* ^ Image:All palaeotemps.png
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