Precambrian Era

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Precambrian Era
Archean
Proterozoic
Hadean
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Precambrian Era
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Precambrian Era

• Includes Earths history from creation up to 590
  million years ago.
• Makes up 7/8 of the Earths history
• The Precambrian starts with the solidifying of
  the Earths crust and ends with the first life
  forms.

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• Represents about 87 of the Earths history.
• Broken down into 3 periods
• Haden 4.5 3.8 BYA
• Archean 3.8 2.5 BYA
• Proterozoic 2.5 - .5 BYA

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Hadean

• 4500 to 3800 million years ago
• Volcanic activity
• Meteor impacts
• Unaware of life that existed during this time

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Hadean Period

• The Hadean or Hades like period was from 4.5 to
  3.8 billion years ago.
• Between the ages of the oldest extraterrestrial
  rocks and the oldest of our own.

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Archaean Eon

• 2500 to 3800 million years ago
• Earth cooled down
• Life began in the ocean
• Blue-green algae floating in the ocean
• Islands from the volcanoes are the only land
  surfaces
• Age of the oldest rocks on Earth

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Archaean Period

• From 3.8 to 2.5 Bya.
• The surface had cooled and water vapor condensed
  forming a global ocean.
• Active volcanism formed island chains.

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Climate

• Earths crust during Archean time was much
  thinner and hotter, and more unstable.
• Earth may have still been cooling off.
• Then atmosphere is steamy and hot.
• Evidence in Lake Superior area and Scandinavia of
  violent volcanism.
• This means the Earth was still forming its
  harder, more stable crust.

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Environment and Life

• All life during this Era was aquatic.
• Life began as bacteria, photosynthetic, blue
  green algae.
• Top a Stromatolite.
• Middle underwater depiction of late Precambrian.
• Bottom photosynthetic bacteria.

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Eubacteria
First life Single-celled prokaryotic organisms
with no DNA
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Cyanobacteria
Earliest fossils
Blue-green algae
Phylum of bacteria that obtain their energy
through photosynthesis.
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Blue-green Algae

• These photosynthetic bacteria were unicellular,
  but would often grow together in great strings
  and mats that would float about in the oceans
  and began to colonize rock formations.

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Stromatolites would cling to rock, adding a layer
of algae, then sediment would cling to it. After
this the Cyanobacteria would grow up through it,
and begin again perpetuating the system.
During the Archean, and through out the
Proterozoic photo synthetic bacteria known as
Cyanobacteria began colonizing the oceans.
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Stromatolites
Attached, lithified sedimentary growth
Structures. Mats of algae overlaying each other
to form layered fossils.
Formed by the trapping, binding, and cementation
of sedimentary grains by microorganisms,
especially Cyanobacteria.
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Fossilized Stromatolites

• These layered fossils show generations of
  bacteria preserved within the rock.

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• Stromatolites grow in arches, but mostly in
  layered formations, and domes.
• Shallow water pools are vital to the formation of
  Stromatolites.

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Stromatolites Today?

• These living fossils still exist today growing in
  Australia, Yellowstone and few other places.
• Hamlin Pool, Australia.

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Yellowstone Octopus Spring

• In Yellowstone National Parks octopus spring
  layered Stromatolites formed by multiple bacteria
  are growing.

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The beginnings of dome Stromatolites

• In Yellowstone the stratified layers of different
  bacteria begin to show cylindrical and dome
  shaped replication of Stromatolites.

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Banded Iron Archaean (2.87 bya)South Pass,
Wyoming
Stromatolites Archaean (2.58 bya)Lower Whalen
Group, Wyoming
Brecciated Banded Iron Archaean (2.73
bya)Jackson County, Wisconsin
Hadrophycus Immanus stromatolites Archaean (2.58
bya)Medicine Bow Range, Wyoming
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Proterozoic Eon

• 542 to 2500 million years ago

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The Proterozoic Period

• The Proterozoic Period took place between 2.5 Bya
  to 570 Mya.
• During this period island chains grouped together
  and expanded from volcanic activity and plate
  tectonics.
• Cores or shields, which are shallow igneous
  formations from the Precambrian are incorporated
  in every present day continent.
• They all come from the original super continent.

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Proterozoic Eon

• The early continents can be dated by determining
  the age of the oldest continental rocks that
  have not been reheated or chemically altered.
• Atmosphere was mostly nitrogen with little water
  vapor and carbon dioxide
• Two super continents
• Land masses formed by collisions of many islands
  made by volcanoes.
• Very cold, with huge bluish glacial ice sheets

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Life in the Proterozoic

• Microscopic organisms
• Most organisms lived in the water.
• The were soft bodies.
• No hard parts for fossilization.

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Life diversified Achaea, Bacteria, Eukaryotes

• Over time, primitive cells evolved into
  multi-cellular life.
• By the end of the Precambrian there were life
  forms called Metazoans. They all had soft
  bodies.
• Jellyfish,
• flat worms,
• annelid worms, etc.

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First multi-cellular, soft bodied animals
By the end of the Precambrian there were life
forms called Metazoans.
Worms
Seapens
Jellyfish
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Fossil Rocks of Precambrian
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Cores Continents

• The cores that formed the super continent became
  the bases upon which our current continents are
  formed. There is a core or shield present
  within each.

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Precambrian Rocks
The metamorphic rocks exposed Along this route
consist of Precambrian schist and gneiss
Many Igneous rocks are Precambrian Granites.