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GY 112: Earth History
Lectures 31: Mesozoic Tectonics
Instructor: Dr. Douglas W. Haywick
UNIVERSITY OF SOUTH ALABAMA
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Last Time…
Mesozoic Overview A) The end of the Paleozoic
B) Mesozoic time frame and evolutionary developments C) Paleogeography and key tectonic events
(web notes 30)
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Phan
eroz
oic
Era Years Cenozoic (0 to 65 MA)
Mesozoic (65 to 245 MA)
Paleozoic (245 to 550 MA)
Phan
eroz
oic
Major Extinction
Major Extinction
Mass Extinctions
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Extinctions have always been a part of the rock record
Mass Extinctions
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The cause(s) of the Permian-Triassic extinction remain uncertain. •Asteroid strike •Cosmic radiation •Climate change •Plate tectonics •“Nemesis” •Flood basalts
Mass Extinctions
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The crater is approximately 180 km wide. The asteroid impacted in a shallow marine, tropical environment.
Mass Extinctions
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The cause(s) of the Permian-Triassic extinction remain uncertain…. … but whatever it was, it caused unprecedented changes
Mass Extinctions
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At the end of the Permian and the end of the Cretaceous, extensive basalt lava flows covered a good chunk of the surface up to 1000’s of feet thick. Major climate change!
Mass Extinctions
The Siberian Traps are much more extensive than the Deccan traps
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Mesozoic Overview
Mesozoic
Cretaceous (65-135 MA)
Late Age of the Angiosperms Middle
Early
Jurassic (203-135 MA)
Late Age of the Cycads Middle
Early
Triassic (245-203 MA)
Late Age of the Reptiles Middle
Early
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Many major evolutionary changes occurred during the Mesozoic •Rise of the dinosaurs •Rise of the cephalopods •Major microfossils (coccoliths) •Rise of the angiosperms
Mesozoic Overview
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Mesozoic Paleogeography
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Mesozoic Paleogeography
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Mesozoic Paleogeography
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Mesozoic Paleogeography
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Mesozoic Tectonics (Key Events)
Period North America Orogenies
Other Major Events
Cretaceous Separation of India from Gondwanna
Jurassic Nevadan Orogeny (J-K)
Sevier Orogeny
(J-K)
Opening of Atlantic Ocean
Triassic
Sonoma Orogeny
(Triassic) Opening of Gulf of
Mexico
Devonian Antler Orogeny (Devonian)
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Today
Mesozoic Tectonics A) The Triassic B) The Jurassic C) The Cretaceous
(web notes 31)
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Mesozoic Tectonics
The separation of Gondwanna and Laurentia began in the Triassic. Initial flooding of the “Atlantic Ocean” began in the Jurassic.
(More on sedimentation next time ) This was the start of a new drift direction for North America; WNW
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Paleozoic Tectonics
Now we have convergence along what had been a pretty stable (passive) continental margin (except for the Antler Orogeny) in the Devonian
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Paleozoic Tectonics
Speaking of which… … when the Antler Orogeny occurred, an island arc stuck onto the side of Laurentia. This clump of “new continent” is called a terrane (specifically the Antler Terrane)
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Paleozoic Tectonics
When terranes hit a continent, they are called docking events. Ultimately, continents grow bigger by scooping up geo-crap in their drift direction (Accretionary tectonics)
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Mesozoic Tectonics
Into the Triassic, many more “terranes” (mostly island arcs) began to be scooped up by North America as it drifted WNW
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Mesozoic Tectonics
Into the Triassic, many more “terranes” (mostly island arcs) began to be scooped up by North America as it drifted WNW •Brooke Range Terrane (Alaska) •Stikine Terrane (British Columbia) •Sonoma Terrane (Nevada)
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Mesozoic Tectonics
Into the Triassic, many more “terranes” (mostly island arcs) began to be scooped up by North America as it drifted WNW •Brooke Range Terrane (Alaska) •Stikine Terrane (British Columbia) •Sonoma Terrane (Nevada)
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Mesozoic Tectonics
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Mesozoic Tectonics
The Sonoman Orogeny in the Triassic marks the start of the formation of the Cordilleran Mountains and the current active margin
Mid-Triassic Paleogeography (source http://jan.ucc.nau.edu/~rcb7)
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Mesozoic Tectonics
In the Jurassic, we start to see terranes with mixed lithologies docking with North America (e.g., Klamath Terrane) •Major (felsic) intrusions begin
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Mesozoic Tectonics The culmination of several “hits” and docking events as well as major phases of felsic intrusions is collectively called the Nevadan Orogeny
Mid-Jurassic Paleogeography (source http://jan.ucc.nau.edu/~rcb7)
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Mesozoic Tectonics
In the Cretaceous, more hits and more intrusions. More uplift •Wrangellia Terrane docks
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Mesozoic Tectonics The culmination of several “hits” and docking events from the Jurassic to the Cretaceous produced major phases of thrust faulting and is collectively called the Sevier Orogeny
Early Cretaceous Paleogeography (source http://jan.ucc.nau.edu/~rcb7)
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What’s the Point?
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What’s the Point?
The Appalachians and Cordilleran Mountains were both formed via compressional tectonic events. Appalachians formed through collisions with other continents Cordilleran Mts. formed via accretionary tectonics
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What’s the Point?
And once we get into the Cenozoic, deciphering the tectonic history of the Cordilleran Mountains gets really tricky… … stay tuned for details!
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Today’s Homework 1. Time Chart 3 due in one week (Hadean-Today )
Next Time 1. Mesozoic Sedimentation (Lectures 32 and 33)
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GY 112: Earth History
Lectures 30 and 31: Mesozoic Geology
Instructor: Dr. Doug Haywick [email protected]
This is a free open access lecture, but not for commercial purposes. For personal use only.