Transcript The Mesozoic - This Old Earth

The Mesozoic
Periods of the Mesozoic
► Triassic
► Jurassic
► Cretaceous
Breakup of Pangaea
Stage one (Triassic)
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Rifting and volcanism, normal faulting
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Tensional stresses separate N. America from Gondwanaland
Similarly, Mexico from S. America
Sea floor generated during opening of ocean
Breakup of Pangaea
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Stage two (Triassic-Jurassic)
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Rifting of narrow Oceans between S. Africa
and Antarctica, Africa and India
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Massive outpouring of basaltic lavas (7 million
km2)
Breakup of Pangaea
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Stage three (Jurassic-Cretaceous)
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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
Post Mesozoic Breakup
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Stage four
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N. America and Eurasia split completely
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Antarctica and Australia split
Mesozoic history of N. America
Eastern and Southern areas
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Triassic and Jurassic
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Normal fault bounded basin develop due to
rifting (Nova Scotia to North Carolina)
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Troughs filled with terrestrial sediments and
volcanics
Newark Group (upper Triassic-lower Jurassic)
Palisades Sill of NJ and NY (190mya)
Triassic and Jurassic
Development of Gulf of Mexico
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Occupied areas opening south of AppalachianOuachita folded mountains
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Filled with Upper Triassic-Lower Jurassic salts
and evaporates (indicating previous arid
condition); over 1000m deposited (origin of
Gulf Coast salt domes)
Cretaceous
Flooding of coastal lowlands due to high
sea levels
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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
Western Areas
Triassic
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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
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Cordilleran Region
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Western belt- Volcanics and siliceous deposits
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Eastern belt- stable interior sediments
Sonoma Orogeny
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(Permian- Triassic, Nevada)
Island arc collided with western margin
Then a west dipping subduction zone
Added 300km new area to west
Massive thrust faulting
Eastern Belt deposition
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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)
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Upper Triassic- Jurassic Stratigraphy: Moenkopi fm,
Shinarup Fm., Navajo Sandstone, Wingate Sandstone
Jurassic-Early Tertiary
Nevadan Orogeny (eastward shift in
orogenic effect)
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Formation of Convergent mélange deposits
Franciscan belt of California (classic mélange)
Great volumes of granodiorite intruded: Sierra
Nevada, Idaho, and coastal range batholiths
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
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Most famous thrust fault: Lewis Thrust (65km
displacement)
Jurassic and Cretaceous Sedimentation
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Navajo Sandstone (Lower Jurassic): Clean recycled eolian sands
deposited in coastal dune and shoreline environments
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Sundance Formation (Middle Jurassic) Famous for fossil reptiles
deposits of the Sundance Sea
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Morris Formation (Upper Jurassic) Swampy plain deposits formed
as Sundance Sea retreated upon rising Cordilleran
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Early Cretaceous Seaway: marine intrusion leaving deposits south
from Arctic ocean to Gulf of Mexico
End of the Mesozoic
► K/T
Boundary
 Marks the border between the Cretaceous (K) and
the Tertiary (beginning of current era-Cenozoic)