Mesozoic Earth History 245-65 Million years ago Triassic Jurassic Cretaceous

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Chapter 14
Mesozoic Earth History 245-65 Million years
agoTriassicJurassicCretaceous
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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 Pangaea
• Lots of mountain-building in western North
  America
• Appearance extinction of dinosaurs
• More detail in the geologic record
• More climate information!

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Climate information in the geologic record

• Evaporites precipitation lt evaporation dry
• Coal lots of vegetation lots of moisture
• Sand dunes dry

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The hydrologic cycle and climate
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Water moves heat from the equator to the poles

• When water changes phase, it either releases or
  takes up energy
• Evaporation gaseous water carries energy
• Humid regions dont get as hot
• Precipitation releases energy as heat
• Humid regions dont get as cold
• Ocean currents are the Earths heating and AC
  ducts, moderating our climate

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Tectonic drivers of climate

• Tectonics influences the hydrologic cycle
• Mountains can block rainfall
• Massive continents tend to have hotter, drier
  cores
• Coastal regions are more moderate
• Circumpolar currents prevent heat from reaching
  poles
• N/S currents move heat effectively

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End Permian land and oceans
Panthalassa

• Pangaea was shaped like a C
• Inside ocean Tethys Sea
• Outside ocean Panthalassa

Tethys sea
Panthalassa
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www.ig.utexas.edu/research/projects/plates/images/
pangea.jpg
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Breakup of Pangea 1 Triple Junctions

• Seafloor spreading creates a triple junction a
  point where 3 tectonic plates diverge
• North America split off from S America and Africa

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Triple Junctions
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Seafloor spreading raises sea level

• Seafloor spreading causes bulges in ocean basins
• Big enough bulges and/or lots of them lowers the
  ocean volume
• This can cause flooding of the continents.

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Breakup of Pangaea 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 Pangaea 3Continued Widening of North
Atlantic

• In Late Cretaceous, Atlantic widened rapidly
• Canada and Europe separated

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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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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

• General term refering to complex period of
  mountain-building Jurassic-Cenozoic
• Farallon plate goes below N American plate
• Nevadan orogeny Late Jurassic/Early Cretaceous
• Orogeny near the current W coast
• Slope of subducting Farallon plate decreased -gt
• Sevier orogeny Late Cretaceous
• Further east (Utah)
• Laramide orogeny Late Cretaceous/Cenozoic
• Even FURTHER east! Rockies

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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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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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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