EESA06H3 Lecture Notes - Lecture 6: Geologic Time Scale, Cambrian Explosion, Aragonite
18 Apr 2016
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Lecture 6 the biological record: the story of life on. Earth & the evolution of the planet"s biosphere. Step 1: the earliest bacteria (about 3. 8 bya) Reason why earliest bacteria were not around 4. 56 bya: earth was very hosile, and lots of magma (excessive heat) so bacteria couldn"t be formed. Step 2: the cambrian explosion (5. 42 mya came much later than earliest organisms) Step 3: diversiicaion during the paleozoic (400-250 mya) Mineralizaion: process which most fossils formaion occur. It is coloured by: chemical addiions (most minerals are coloured by impuriies) Rocks have been uplited by tectonic forces and eroded (lost some materials, via wind, ice, rain, etc wore away some rocks) and let fossils. Trace fossils: don"t show the appearance of the organisms, but can see what the organisms did. Very common in carbonate rocks such as limestones. Locaion of rocks that have broken sea lilies, shells, coral: shallow environments. Morphology: study of the way something looks.
