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Banded Iron Formations: The Evolution of Earth’s Surface and Life Mike Tice 6 August 2009 Earth History The Most Important Organisms in Earth History: The Cyanobacteria! • Bacteria • The first organisms to produce oxygen during photosynthesis • The ultimate source of all oxygen in our atmosphere https://eapbiofield.wikispaces.com/file/detail/I11-30-cyanobacteria.jpg Banded Iron Formation 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. This is a photograph of a slab of banded iron formation cut with a rock saw. • Is this piece of banded iron formation more like a shale or a conglomerate? • Why are they similar? shale http://commons.wikimedia.org/wiki/File:Limestone_on_shale.jpg conglomerate 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 UV light • Dissolved iron (and no oxygen) in the deep ocean • UV light passing through the upper atmosphere with no ozone layer Another Model of BIF Deposition anoxygenic bacteria • Dissolved iron (and no oxygen) in the deep ocean • Non-oxygen producing (anoxygenic) photosynthetic bacteria in shallow water 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?
