The Historical Geology of the Grand Canyon

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The Historical Geology of the Grand Canyon
By Emily Kahler
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Brief overview of Arizona
?The oldest rocks in the Tucson Mountains are
over 570 million years old. ?Deposited by
sea(sedimentary-- gneiss and schist) ?Paleozoic
era(another sea sedimentary roc,now
limestone ?covered with lots of Volcanoes during
the Jurassic Period (ash and dust). ?Arizona
mountains are weathered Volcanoes. ?Afterwards,
streams passed through creating sandstone and
limestone.
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Overview of the Grand Canyon
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List of Geological events of the Grand Canyon

• The Grand Canyon mountain range (1.7billion yrs
  ago)
• 1.25 billion yrs ago there was a sea which laid a
  sedimentary layer, along with Stromatolites
  preserve.
• 1.2 billion yrs ago sea retreated mud flats
  (Hakatai Shale)

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Continued

• 1.19 billion yrs layer Dox Formation (mudstones
  and shales with ripple marks)
• Between 1.25 and 1.1 billion yrs ago volcanic
  Cardenas Basalts.
• Between 1 billion and 825 million yrs ago
  coastal/shallow sea formations (Chuar group).

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Continued

• unconformity of 250 million years which new rock
  layers laid down but completely eroded.
• The Tapeats Sandstone 550 million yrs ago
• The Bright Angel Shale 540 million yrs ago (ocean
  advancing).
• The Muav Limestone 530 million yrs ago (bottom of
  a shallow sea).

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Continued.

• Redwall Limestone deposited 330 million yrs ago
  (submerged for long time).
• The Supia Group dated at 300 million yrs ago
  (formed above water ).
• The Hermit Shale 280 million yrs ago contains
  plant fossils (above water).

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Continued

• The Coconino Sandstone (sand dunes) 270 million
  yrs ago.
• The layers found within Toroweap Formation
  (sandstone and limestone sometimes coastal and
  sometimes submerged). 260 million years.
• top layer of Grand Canyon, contains many marine
  fossils. Kaibab Limestone (250 million yrs old).
• Rock layers younger than 250 million yrs have
  been eroded away.

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Continued

• The Rocky Mountains form 60-70 million yrs ago
  --Colorado River is born.

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Two possible Theories

• 20 million years ago the Colorado River begins to
  carve into the Grand Canyon probably exiting
  Kanab Canyon.
• At 17 million yrs ago the uplift of Colorado
  Plateau river to cut deeper.
• 5 million years ago the uplift ceases and another
  river on Colorado Plateau captures the Colorado
  river.

• 35 million yrs ago the Kaibab Plateau uplift
  diverts the Colorado, The cut-off western
  portion, (Hualapai Drainage) still drains the
  western region.
• 12 million yrs ago the path to the sea is blocked
  -- Lake Bidahochi.
• Lake Bidahochi is drained and becomes the Little
  Colorado River.

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In more detail

• The Pangea formation
• The north American plate used to be south of were
  it is today.
• The plates moved to where
• they are today.
• The east coast is on
• a subduction boundary
• zone which has caused
• uplift of the land and
• volcanoes.

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Work Cited
Ratkevich, Ron.Cretaceous Period in Sounthern
Arizona http//www.t-rat.com/Pages/CretaceousSAz.
html Bob Ribokas, 1994-2000. The Geology of the
Grand Canyon http//www.bobspixels.com/kaibab.org
/geology/gc_geol.htm The Cenozoic History of
Arizon http//web1.shastacollege.edu/geoscience/hi
stories/ Az/Cenozoic/cz_histAz.html