Mesozoic Earth History

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Mesozoic Earth History
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What is the Mesozoic?

• Middle life after Permian extinction
• 250-66 Ma
• Cretaceous
• Jurassic
• Triassic

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Geologic Time Scale
www.geo.ucalgary.ca/macrae/timescale/time_scale.g
if
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Main Happenings in Mesozoic

• Breakup of Pangea
• Lots of mountain-building in western North
  America
• Appearance of dinosaurs
• Extinction of dinosaurs

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Effect of the Breakup

• Populations became isolated
• Or were brought into contact with other
  populations
• Leading to evolutionary changes in the biota

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www.ig.utexas.edu/research/projects/plates/images/
pangea.jpg
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Breakup of Pangea 1Opening of North Atlantic

• Began in Late Triassic
• North America and Africa split apart
• North Atlantic Ocean began to open

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Breakup of Pangea 2Opening of Gulf of Mexico

• In Middle Jurassic, North America and South
  America separated
• Gulf of Mexico began to open
• Restricted basin at first lots of evaporites
  deposited

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Gulf of Mexico Salt
http//oceanexplorer.noaa.gov/technology/tools/map
ping/media/gis_gulf.html
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Breakup of Pangea 3Continued Widening of North
Atlantic

• In Late Cretaceous, Atlantic widened rapidly
• Canada and Europe separated
• My thesis topic!

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Final Breakup

• In Late Cretaceous, Australia and Antarctica
  separated
• In Cenozoic, Antarctica and South America
  separated

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Global Plate TectonicsJurassic to Present Day
By L.A. Lawver, M.F. Coffin, I.W.D. Dalziel L.M.
Gahagan, D.A. Campbell, and R.M. Schmitz ?2001,
University of Texas Institute for
Geophysics February 9, 2001
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Paleogeography of the World

• During the Triassic Period

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Paleogeography of the World

• During the Jurassic Period

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Paleogeography of the World

• During the Late Cretaceous Period

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What does North America look like?

• Still mostly above SL
• Mountain-building on west coast
• Epeiric sea returned to western craton in Middle
  Jurassic
• Eventually joined Gulf of Mexico to create
  continuous seaway from Gulf to Arctic

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Where did most North American mountain-building
occur during Paleozoic?
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Where did most North American mountain-building
occur during Paleozoic?
East Coast - Appalachians
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Cordillera

• Western margin of North America
• Spanish for mountain range
• Rocky Mountains, Sierra Nevadas

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Cordillera Orogenies

• Nevadan orogeny Late Jurassic/Early Cretaceous
• Sevier orogeny Late Cretaceous
• Laramide orogeny Late Cretaceous/Cenozoic
• Caused mainly by convergent margin tectonics

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Global Sea-Level Rise

• A global rise in sea level during the Cretaceous
• resulted in worldwide transgressions
• marine deposition was continuous over much of the
  North American Cordillera

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Cretaceous Flood

• Worldwide transgression
• 1/3 of land area of Earth submerged
• 100 Ma
• Cretaceous Interior Seaway in North America

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Cretaceous Interior Seaway

• Paleogeography of North America during the
  Cretaceous Period

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Western Interior Seaway
www.isgs.uiuc.edu/dinos/westernseaway.gif
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Western Interior Seaway
www.colorado-mall.com/HTML/EDUCATIONAL/SCIENCES/GE
OLOGY/COLO_GEOLOGY/COLO_CREATION/ANCIENT_SEAS/anci
ent_seas.html
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What are the 3 main points from todays class?
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What are the 3 main points from todays class?

• Breakup of Pangea occurred in Mesozoic
• Cordillera began to form through several
  orogenies
• Cretaceous Interior Seaway formed in North
  America

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The Effects on Global Climates and Ocean
Circulation Patterns

• At the end of the Permian Period
• Pangaea extended from pole to pole
• Covered about one-fourth of Earth's surface
• Surrounded by a global ocean that encompassed
  about 300 degrees of longitude
• Such a configuration exerted tremendous influence
  on the world's climate
• resulted in generally arid conditions over large
  parts of Pangaea's interior

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Oceanic Circulation Evolved

• From a simple pattern in a single ocean
  (Panthalassa) with a single continent (Pangaea)

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Oceanic Circulation Evolved

• to a more complex pattern in the newly formed
  oceans of the Cretaceous Period

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Faster Circulation

• The temperature gradient between the tropics and
  the poles affects oceanic and atmospheric
  circulation
• The greater the temperature difference
• the steeper the temperature gradient
• and the faster the circulation of the oceans and
  atmosphere

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Areas Dominated by Seas Are Warmer

• Oceans absorb about 90 of the solar radiation
  they receive
• continents absorb only about 50
• even less if they are snow covered
• The rest of the solar radiation is reflected back
  into space
• Therefore, areas dominated by seas are warmer
  than those dominated by continents