UNIVERSITY OF SOUTH ALABAMA
Last time we covered…
Archean Oceans Discussion
(Robbie)
MAS 603: Geological Oceanography
Banded Iron Formations
(Evolution of the Earth’s atmosphere and hydrosphere)
Lecture 10: Ediacarins
1) The Early Atmosphere
2) The Oceans and Hydrosphere
3) The Change
Oxygen
The how is easy:
Cyanobacteria (e.g., the
microorganisms comprising
stromatolites)
and photosynthesis
Oxygen
Of particular interest
are banded iron
formations (BIFs)
that are composed of
alternating layers of
hematite (Fe2O3) and
silica.
Photosynthesis
6CO2 + 6H2O → C6H12O6 (“sugar”) + 6O2
BIFs
The first BIFs formed
around 3.1 GA and
peaked in abundance
at 2.7-2.5 GA
BIFs
BIFs are thought to
have been formed
through oxygenation
of sea water
containing Fe2+
(reduced iron).
Fe2+
Soluble
→
Fe3+
Insoluble
http://jersey.uoregon.edu/~mstrick/myimages/Banded%20Iron.gif
http://www.ldeo.columbia.edu/edu/dees/U4735/lectures/03.html
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Oxygen in the Atmosphere
Oxygen in the Atmosphere
What about the
atmosphere?
Around the world, we
see a shift in color of
river floodplain shale
Green
Fe2+
to Red
→ Fe3+
At 1.8 GA
http://www.grisda.org/colorado/images
http://www.ldeo.columbia.edu/edu/dees/U4735/lectures/03.html
Today’s Agenda
Proterozoic Beasties
1)
2)
Eukaryotes (Acritarchs)
Metazoans (Ediacarin Fauna)
Proterozoic Fossils
During the Proterozoic,
something wonderful happens:
the rise of the eukaryotes:
Proterozoic Fossils
During the Archean, we saw
the rise of the prokaryotes:
•Small
•No nucleus
•DNA spread throughout the
cell
•Asexual reproduction
•Could only be single-celled
Proterozoic Fossils
The first eukaryotes appeared around 2 GA. Archritarchs were
small, single celled silica beasties that floated in the oceans
(pelagic). They peaked in abundance at 750 MA and then went
away…
•Larger (>0.06 mm)
•A nucleus and organelles
•DNA contained within the
nucleus
•Sexual reproduction
•Could be multi-celled
(metazoans)
0.1mm
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Proterozoic Fossils
Proterozoic Fossils
… or did they? They might in fact be ancestors to equally small
single celled organisms that are around today called
dinoflaggelates
Another big change in the Proterozoic was the appearance of
the first Metazoans
5 cm
0.1mm
Proterozoic Fossils
They are known as
the Ediacarin Fauna
Proterozoic Fossils
What were the
Ediacarins?
And they are found
around the world
Three major “forms”
http://www.cartage.org.lb/en/themes/Sciences
http://www.snowballearth.org/end.html
http://www.cartage.org.lb/en/themes/Sciences
Proterozoic Fossils
What happened to
them?
Proterozoic Fossils
What happened to
them?
1) a now extinct line
of beasties
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Proterozoic Fossils
What happened to
them?
Proterozoic Fossils
What were the
Ediacarins?
Kimberella sp.
1) a now extinct line
of beasties
1) a now extinct line
of beasties
2) ancestors to living
phyla
2) ancestors to living
phyla
Dickinsonia sp.
http://www.ucmp.berkeley.edu/vendian/kimberella.jpg
Proterozoic Fossils
Proterozoic Fossils
More likely, severe
environmental
changes drives
evolutionary
adaptation.
Whatever they were,
they “exploded” onto the
scene immediately after
the last Snowball Earth.
Coincidence?
We need bad things
to happen in order to
evolve.
http://pharyngula.org/index/science/2004/08/
Proterozoic Fossils
http://www.snowballearth.org/end.html
The Cambrian Explosion
Not so much an explosion…
…more of a shift… to hard
body parts
The “Cambrian
Explosion”
http://www.snowballearth.org/end.html
http://arjournals.annualreviews.org/na101/home/literatum/publisher/
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The Cambrian Explosion
The Cambrian Explosion
Burgess Shale Fauna
Chengjiang Fauna
What we know about the early
development of all of the
current phyla is limited to sites
where we have lots of beasties
preserved
http://arjournals.annualreviews.org/na101/home/literatum/publisher/
The Burgess Shale
Burgess Shale Site
The Burgess Shale
The Burgess Shale
Burgess Shale Site
The Burgess Shale
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The Burgess Shale
The Burgess Shale
The Burgess Shale
The Burgess Shale
http://www.hao.ucar.edu/Public/models/pikaia/pikaia.gif
Pikaia gracilens (phylum: Chordata)
The Burgess Shale
The Burgess Shale
http://www.hrw.com/science/si-science/biology/animals/burgess/phallu.html
Limb
Anomalocaris canadensis
Hallucigenia sparsa
(phylum: Arthropoda?)
(Proto-Arthropod; Problematica)
(phylum: Arthropoda)
http://www.karencarr.com/Images/Gallery/2004_gallery_hallucigenia.jpg
http://www.search4dinosaurs.com/burgess_shale.jpg
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The Burgess Shale
The Burgess Shale
http://www.hrw.com/science/si-science
Jaws
Anomalocaris canadensis
(phylum: Arthropoda?)
(Proto-Arthropod; Problematica)
http://www.search4dinosaurs.com/burgess_shale.jpg
http://home.earthlink.net/~airdpacoima/sitebuildercontent/sitebuilderpictures/burgess__s.jpg
Next Time
1. Monday: Proterozoic Evolution Discussion (Isabella)
2. Wednesday: Sedimentary Facies
Warning: Take home exam issued next Monday
(No reading next week)
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