GEOL 107 Lecture Notes - Lecture 8: Great Oxygenation Event, Pilbara Craton, Gunflint Chert
18 Oct 2016
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Lecture will end up on midterm, final, or both. Most important global change on our planet. Warrawoona, australia pilbara craton: reliable indicator of 1st microscopic life forms on earth (stromatolites) Layers of sediment that reflect the presence of mats of unicellular organisms, but the actual micro-organisms that made the layers are seldom preserved. Flat, conical, or dome-shaped in different environments from <1cm to >10m wide. Still form today in extreme environments: ex. Shark bay in australia or the persian gulf. They are relatively rare in the archean and are mostly associated in shallow- water environments and became very abundant in the proterozoic. Filaments and spheres of carbon that reflect the cell walls of unicellular organisms. Oldest known organic microfossils are from warrawoona. Filamentous microfossils 3. 25 ga from nearby sulphur springs in the pilbara. Both the microfossils from warrawoona and sulphur springs formed in submarine hot springs rather than shallow sea or warm little pond.
