Banded Iron Formations: The Evolution of Earth’s Surface and Life

Mike Tice6 August 2009

Earth History

The Most Important Organisms in Earth History:

https://eapbiofield.wikispaces.com/file/detail/I11-30-cyanobacteria.jpg

The Cyanobacteria!

• Bacteria

• The first organisms to produce oxygen during photosynthesis

• The ultimate source of all oxygen in our atmosphere

Banded Iron Formation

This is a photograph of a slab of banded iron formation cut with a rock saw.

This is a photograph of a slab of banded iron formation cut with a rock saw.

This image uses color to represent the composition of a small part of the slab. Here, red represents the element Fe.

• Is this piece of banded iron formation more like a shale or a conglomerate?

• Why are they similar?

shale conglomerate

http://commons.wikimedia.org/wiki/File:Limestone_on_shale.jpg http://en.wikipedia.org/wiki/File:Lehigh_conglom.jpg

Model of BIF Deposition

• Dissolved iron (and no oxygen) in the deep ocean

• Cyanobacteria producing oxygen in the shallow ocean

Another Model of BIF Deposition

• Dissolved iron (and no oxygen) in the deep ocean

• UV light passing through the upper atmosphere with no ozone layer

UV light

Another Model of BIF Deposition

• Dissolved iron (and no oxygen) in the deep ocean

• Non-oxygen producing (anoxygenic) photosynthetic bacteria in shallow water

anoxygenic bacteria

Questions

• What do banded iron formations tell us about changing environments in the Earth’s oceans?

• What do banded iron formations tell us about the evolution of photosynthesis?

• How were changing conditions in the atmosphere and oceans related in time? How would organisms living in the shallow and deep oceans have reacted to changing environmental conditions?