The Mesozoic
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Periods of the Mesozoic
Triassic- First period of the Mesozoic eraJurassicCretaceous- Last period of the Mesozoic era
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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
Wednesday, November 30, 11
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
Wednesday, November 30, 11
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)
Wednesday, November 30, 11
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)
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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
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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
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Post Mesozoic Breakup
► Stage four
N. America and Eurasia split completely
Antarctica and Australia split
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Post Mesozoic Breakup
► Stage four
N. America and Eurasia split completely
Antarctica and Australia split
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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)
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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)
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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
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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
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Cordilleran Region
► Western belt- Volcanics and siliceous deposits
► Eastern belt- stable interior sediments
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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
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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
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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
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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
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Sevier Orogeny
► middle Jurassic- early 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)
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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
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End of the MesozoicK/T Boundary
Marks the border between the Cretaceous (K) and the Tertiary (beginning of current era-Cenozoic)
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Composition of the KT Boundary
Tektites and shock quartz
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Composition of the KT BoundaryIn 1980 a team of researches published an elemental analysis of the K/T boundary that showed high levels of the element iridium.
Since then these same results have been shown in multiple locations around the world
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What Caused the K/T boundary?
All the evidence points to a meteorite impact. The problem is where is the crater
Meteor Crater Arizona
Wednesday, November 30, 11
What Caused the K/T boundary?
All the evidence points to a meteorite impact. The problem is where is the crater
Meteor Crater Arizona
Wednesday, November 30, 11
Locating the Crater
Wednesday, November 30, 11
Locating the Crater
Wednesday, November 30, 11
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