208_Lect10_color - The Proterozoic: 2.5-0.542 Ga Early...

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1 The Proterozoic: 2.5-0.542 Ga • Early Proterozoic Orogenesis ~ modern • Growth of continents and Supercontinents • Life and Environments of Proterozoic Archean-early Proterozoic Continents: First large continent at ~3 Ga Pangola Supergroup of S. Africa (regressive sediments) cover ~40k km 2 Nuna is assembled ~2.5 to 1.6 Ga from suturing together of small Archean continents. Nuna Many of the small Archean continents are now exposed in the Canadian Shield Shield = exposed craton. – Craton = old continental crust not involved in orogenesis since ~1Ga Let’s look at part of the assembly of Nuna: Wapmay, Yavapai and Grenville Orogenies Wapmay Orogeny = first example of modern orogenesis ( draw)
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2 Wopmay Orogeny ~1.9 Ga modern tectonics and large rigid continents! Yavapai Province sutured to Nuna ~1.8 Ga Begin forming Rhodinia Forms the Mazatzal Mountains - Vishnu Schist and Zoroaster Granite of the Grand Canyon! Yavapai Province underlies mid-continent of US.
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3 Mid-Continental Rifting 1.2 to 1 Ga • Failed rifting from Great Lakes to Kansas • Produced rift grabens (now covered) and flood basalts (some exposed in upper Michigan Notice the ‘Sed. Basins’ these are failed rifts from ~1.5 Ga e.g. Belt Supergroup Grenville Orogeny ~1.1 Ga marks assembly of Rhodinia Rhodinia Rifts ~750 Ma Break-out of Laurentia
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208_Lect10_color - The Proterozoic: 2.5-0.542 Ga Early...

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