GY 112: Earth History

Lectures 31: Mesozoic Tectonics

Instructor: Dr. Douglas W. Haywick

UNIVERSITY OF SOUTH ALABAMA

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)

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

Extinctions have always been a part of the rock record

Mass Extinctions

The cause(s) of the Permian-Triassic extinction remain uncertain. •Asteroid strike •Cosmic radiation •Climate change •Plate tectonics •“Nemesis” •Flood basalts

Mass Extinctions

The crater is approximately 180 km wide. The asteroid impacted in a shallow marine, tropical environment.

Mass Extinctions

The cause(s) of the Permian-Triassic extinction remain uncertain…. … but whatever it was, it caused unprecedented changes

Mass Extinctions

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

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

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

Mesozoic Paleogeography

Mesozoic Paleogeography

Mesozoic Paleogeography

Mesozoic Paleogeography

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)

Today

Mesozoic Tectonics A) The Triassic B) The Jurassic C) The Cretaceous

(web notes 31)

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

Paleozoic Tectonics

Now we have convergence along what had been a pretty stable (passive) continental margin (except for the Antler Orogeny) in the Devonian

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)

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)

Mesozoic Tectonics

Into the Triassic, many more “terranes” (mostly island arcs) began to be scooped up by North America as it drifted WNW

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)

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)

Mesozoic Tectonics

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)

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

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)

Mesozoic Tectonics

In the Cretaceous, more hits and more intrusions. More uplift •Wrangellia Terrane docks

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)

What’s the Point?

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

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!

Today’s Homework 1. Time Chart 3 due in one week (Hadean-Today )

Next Time 1. Mesozoic Sedimentation (Lectures 32 and 33)

GY 112: Earth History

Lectures 30 and 31: Mesozoic Geology

Instructor: Dr. Doug Haywick dhaywick@southalabama.edu

This is a free open access lecture, but not for commercial purposes. For personal use only.