EARTH 20 Lecture Notes - Lecture 14: Ediacaran Biota, Cambrian Explosion, Snowball Earth
Document Summary
Age of the earth: 4. 567 ga (billion years) Apparent evidence for isotope signatures of life @ 3. 8 ga (very controversial) Good evidence for stromatolites in shark bay, australia (@3. 5 ga) Preservation of fossil bacteria from ~3. 43 ga kelly group in australia. First evidence of eukaryotes (organism whose cells contain a nucleus and other organelles enclosed within membranes) @1. 7 ga. Banded iron formations (bif): iron dissolved in the ocean reacted with o2, forming world-wide iron oxide deposits (@2. 5 ga-present day) Came from photosynthesis (6co2 + 6h20 = c6h12o6 + 6o2) When ice went away, life started to diversify rapidly (but no hard parts) Ediacara biota (575-542 ma): first abundant, worldwide, macroscopic multicellular fossils. Could have been more, but didn"t have way of measuring them. Volcanic eruptions (anoxia in oceans, increased amounts of co2 and sow > global warming and acid rain. Very well dated (65 +/- . o1 ma)
