GEOL 2155 Lecture Notes - Lecture 17: Sidneyia, Authigenesis, Holdfast
18 Jan 2017
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Document Summary
88% of earth"s history occurs in the pre-cambrian. Those that are exposed have often been severely deformed and altered by orogenic events. Orogenic events result in formation of metamorphic rocks under extreme pressure (and heat) Earth"s formation (~4. 6ga) through to the start of the. Although an exceptionally long timespan , the precambrian forms less than 20% of rocks at. Life forms are unicellular , rarely preserved, difficult to identify/differentiate from one another. Liquid oceans were present by the beginning of the archean (3. 8ga) Found pillow basalts from the isua formation of greenland. Isua formation also preserves some of the oldest evidence of life: C12 (98. 89% of earth"s carbon; 6 protons, 6 neutrons) C13 (1. 11% of earth"s carbon; 6 protons, 7 neutrons) It is more metabolically efficient to use the lighter atom (it weighs less), so living organisms tend to be enriched in. Pass down a tube in a stream of inert gas.
