Sevier

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Sevier Laramide Orogenies
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The North American Cordillera
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Cordilleran Structure
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Orogenic Sequence
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The Orogenic Belt
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Propagation of Thrust Belts
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Decollement
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Foreland Basins
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Foreland Orogen Basin
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Sevier Orogeny

• 170 to 80 Million years ago

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Sevier horribly complex
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Middle Jurassic 170 160 Million years ago
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Late Jurassic 160 155 Million years ago

• Western Plate Margin Consolidates,
• accretion of Coast Range Ophiolite
• Farallon Plate Subduction Begins

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Latest Jurassic 155 142 Million years ago

• Voluminous Arc Magmatism
• Crustal Shortening

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Early Cretaceous 142 110 Million years ago

• Emplacement of Mega-Thrust Sheet

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Middle Cretaceous 110 85 Million years ago

• Onset of rapid shortening and Sevier Orogeny

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Sevier oversimplified
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Sediments in the Foreland Basin

• The diagram shows two diferent kinds of sediments
  in the foreland basin
• Sediment from the west is clastic sandstone and
  mudstone, eroded from the mountains of the thrust
  belt.
• Sediments from the east are shales and marine
  sediments which developed in a shallow sea.
• The dotted line shows the migration of sea level
  back and forth as sediments were deposited.

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Laramide Orogeny

• 80 to 40 Million years ago

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Sevier another look
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Laramide to the east
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Laramide Involves Basement!
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Follow this link for a neat movie!
http//element.ess.ucla.edu/publications/1998_Lara
mide/RMF_velocity_movie.gif
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