GEOL 102 Lecture Notes - Lecture 15: Annelid, Western Australia, Rodinia

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31 Mar 2017
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Geology 102 Lecture 15 Notes
Proterozoic Eon
Proterozoic Eon
2.5 bya to 542 mya
Many processes which had started in the Archean continued into the Proterozoic
Oxygen
Photosynthetic organisms flourished
Continuing rise in atmospheric oxygen
Organisms
Increase in number and type of fossils
Stromatolites become very very diverse and common
Oxygen
Banded iron formations disappear around 2 bya
New sediments were largely oxidized often appearing red from iron oxide
minerals
Plate Tectonics
Volcanic arcs formed chains of islands at subduction zones
Continents grew larger from collisions with these arcs and one another-
continental accretion
During collisions sediments from shallow seas between continents were
compressed and metamorphosed orogenic stabilization
Thickens and hardens crust
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Early Continents
Evidence for components and locations for early continents and supercontinents
Geologic comparisons
Paleomagnetic data
Radiometric dating
Plate Tectonics
Extensive reworking makes understanding the original size and shape of these
early continents problematic
Early Supercontinents
Proposed early supercontinents include
Vaalbara- 3.6-2.5 bya
Included parts of West Australia and South Africa
Ur- 3.0 bya- Rodinia
Included parts of Africa Australia and India
Kenorland- 2.7 bya- Rodinia
Included parts of North and South America, Australia, and
Antarctica and Eurasia
Arctica- 2.5 bya- Rodinia
Included parts of Canada and and Siberia
Atlantica- 2.0 bya- Rodinia
Included parts of South America and western Africa
Nena- 1.8 bya- Columbia
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Document Summary

Many processes which had started in the archean continued into the proterozoic. Increase in number and type of fossils. Stromatolites become very very diverse and common. Banded iron formations disappear around 2 bya. New sediments were largely oxidized often appearing red from iron oxide minerals. Volcanic arcs formed chains of islands at subduction zones. Continents grew larger from collisions with these arcs and one another- continental accretion. During collisions sediments from shallow seas between continents were compressed and metamorphosed orogenic stabilization. Evidence for components and locations for early continents and supercontinents. Extensive reworking makes understanding the original size and shape of these early continents problematic. Included parts of west australia and south africa. Included parts of africa australia and india. Included parts of north and south america, australia, and. Included parts of canada and and siberia. Included parts of south america and western africa. Included parts of north america and northern europe. Laurentia (north america), siberia, western india, baltica, china,

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