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The Mesozoic

The Mesozoic. Periods of the Mesozoic. Triassic Jurassic Cretaceous. Breakup of Pangaea. Stage one (Triassic) Rifting and volcanism, normal faulting Tensional stresses separate N. America from Gondwanaland Similarly, Mexico from S. America Sea floor generated during opening of ocean.

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The Mesozoic

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  1. The Mesozoic

  2. Periods of the Mesozoic • Triassic • Jurassic • Cretaceous

  3. Breakup of Pangaea • Stage one (Triassic) • Rifting and volcanism, normal faulting • Tensional stresses separate N. America from Gondwanaland • Similarly, Mexico from S. America • Sea floor generated during opening of ocean

  4. Breakup of Pangaea • Stage two (Triassic-Jurassic) • Rifting of narrow Oceans between S. Africa and Antarctica, Africa and India • Massive outpouring of basaltic lavas (7 million km2)

  5. Breakup of Pangaea • Stage three (Jurassic-Cretaceous) • Atlantic Ocean rift extended northward • Clockwise rotation of Eurasia • Closing of eastern Tethys Sea (Mediterranean) • S. America-Africa split apart • Australia-Antarctica remain intact • Eastern N. America and Greenland remain intact

  6. Post Mesozoic Breakup • Stage four • N. America and Eurasia split completely • Antarctica and Australia split

  7. Mesozoic history of N. America • Eastern and Southern areas • Triassic and Jurassic • Normal fault bounded basin develop due to rifting (Nova Scotia to North Carolina) • Troughs filled with terrestrial sediments and volcanics • Newark Group (upper Triassic-lower Jurassic) • Palisades Sill of NJ and NY (190mya)

  8. Triassic and Jurassic • Development of Gulf of Mexico • Occupied areas opening south of Appalachian-Ouachita folded mountains • Filled with Upper Triassic-Lower Jurassic salts and evaporates (indicating previous arid condition); over 1000m deposited (origin of Gulf Coast salt domes)

  9. Cretaceous • Flooding of coastal lowlands due to high sea levels • Atlantic and Gulf Coast plains inundated as they acted as subsiding shelves • Thick delta, barrier island, shelf and reef deposits • Florida: Shallow submarine bank for limestones • Reefs made of Rudistid bivalves rimmed Gulf Coastal area • Extensive chalk deposits due to massive production of calcerous plankton • Rifting and ocean opening on eastern side leads to closure and compression on western side

  10. Western Areas • Triassic • Accretionary tectonics- Characteristic of west coast subduction • Steeply dipping subduction zone • Volcanic Arcs and micro-continents carried to western margin • Massive accretion by subduction (including volcanics) • Tectonic collage of displaced terrain 70% of total western accretion

  11. Cordilleran Region • Western belt- Volcanics and siliceous deposits • Eastern belt- stable interior sediments

  12. Sonoma Orogeny (Permian- Triassic, Nevada) • Island arc collided with western margin • Then a west dipping subduction zone • Added 300km new area to west • Massive thrust faulting

  13. Eastern Belt deposition • Sandstones and limestones (shallow marine, 1000m in Idaho) • Lower Triassic red bed facies farther east • Upper Triassic sediments mostly from rivers (flowed west over area) • Upper Triassic- Jurassic Stratigraphy: Moenkopi fm, Shinarup Fm., Navajo Sandstone, Wingate Sandstone

  14. Jurassic-Early Tertiary • Nevadan Orogeny (eastward shift in orogenic effect) • Formation of Convergent mélange deposits • Franciscan belt of California (classic mélange) • Great volumes of granodiorite intruded: Sierra Nevada, Idaho, and coastal range batholiths

  15. Sevier Orogeny (middle Jurassic- earliest Tertiary) • Precedes batholith intrusion • basement-involved tectonics: multiple imbricated thrust faults (low angle) • Mainly seen in NV, UT and MT • Most famous thrust fault: Lewis Thrust (65km displacement)

  16. Jurassic and Cretaceous Sedimentation • Navajo Sandstone (Lower Jurassic): Clean recycled eolian sands deposited in coastal dune and shoreline environments • Sundance Formation (Middle Jurassic) Famous for fossil reptiles deposits of the Sundance Sea • Morris Formation (Upper Jurassic) Swampy plain deposits formed as Sundance Sea retreated upon rising Cordilleran • Early Cretaceous Seaway: marine intrusion leaving deposits south from Arctic ocean to Gulf of Mexico

  17. End of the Mesozoic • K/T Boundary • Marks the border between the Cretaceous (K) and the Tertiary (beginning of current era-Cenozoic)

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