9proterohist - 2/22/12 Proterozoic 2.5bya-540mya...

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2/22/12 1 Proterozoic 2.5bya-540mya Proterozoic compared to Archean. . • Proterozoic has a more “modern type of plate tectonics, sedimentation, and climate. • First major Wilson cycle. • First large ice age –most of Earth cooled. • Most BIFs. • 42% of Earth’s history! Proterozoic day • NOT the same as today’s day – about 18 hours long • BUT year was >400 days! • How do we know? Heliophyllum • Earth is slowing down. Evidence for longer day Proterozoic • Paleoproterozoic – 2.5-1.6 byr • Mesoproterozoic – 1.6-1.0 byr • Neoproterozoic – 1.0 byr - Paleozoic PALEOPROTEROZOIC Highlights • First ice age • Increase of Oxygen • High amount of Plate Tectonics
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2/22/12 2 First supercontinents • Laurentia • Rodinia Evidence of Wilson cycle • Opening of an ocean basin • Sedimentation along continental margins • Closing of an ocean basin • WOPMAY OROGENY Wopmay orogeny Wopmay evidence Early North America Formation of North America
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2/22/12 3 4 stages to form North America 1- 2 byr- several small Archean granitic continents accreted together. 2- ~ 1.5 byr, Siberia and possibly Australia & Antarctica were fused to western N.A. and Baltica (the Scandinavian nucleus of Europe) was converging with Eastern N.A. They collided ~ 1.2 byr Another continent of unknown size - Mazatzal, was converging from the south to make a supercontinent about 1.3-1.4 byr. 3-
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This note was uploaded on 03/26/2012 for the course GEOL 102 taught by Professor Kysar during the Spring '06 term at George Mason.

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9proterohist - 2/22/12 Proterozoic 2.5bya-540mya...

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