The Grand Canyon Tells the Story of North America

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The Grand CanyonTells the Story of North America

• Knowing how and where rocks are formed allows us
  to read the story written in the rocks.
• A mile thickness of rocks of the Great Plains are
  exposed by uplift and erosion by the Colorado
  River.

2
Rocks of the Grand Canyon

• Separate the larger puzzle into a series of
  smaller puzzles (I.e., each group of rocks)
• Metamorphic rocks (oldest)
• Intrusive igneous rocks
• Sedimentary rocks lying on an irregular
  metamorphic surface
• Sedimentary layering
• Erosion of the canyon

(Youngest event)
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Rocks of the Grand Canyon

• Each group of rocks is separated by a gap in the
  geologic record (formations and contacts)
• Metamorphic rocks ? Metamorphism
• Granite ? Intrusion of silicic magma
• Eroded surface ? Uplift and erosion
• Sedimentary rocks ? Shallow inland seas
• Erosion of the Canyon ? Recent uplift

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Metamorphic and Igneous Rocks

• Metamorphism of sedimentary rocks
• Igneous intrusion during later stages of
  metamorphism (during mountain building)
• Uplift and erosion (during and after mountain
  building)

(nonconformity)
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Sedimentary Rocks

• Deposition of sediments on eroded metamorphic and
  igneous rocks.
• Uplift and erosion exposing sedimentary layers
  and
• Eventually expose Igneous and metamorphic rocks
  again

G Uplift and Renewed Erosion
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Erosion and Exposure

• Uplift and erosion exposing sedimentary layers
  and
• Eventually Igneous and metamorphic rocks again

G Uplift and Renewed Erosion
G Uplift and Renewed Erosion
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Formation of the Grand Canyon
Sandstone
350
Shale
380
Limestone
450 Million Years Old
300 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion

Erosion
Sandstone
350
Shale
380
Limestone
450
280 million years ago
Regional Uplift Tilting (or folding)
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion

Erosion
Sandstone
350
Shale
380
Limestone
450
270 million years ago
Regional Uplift
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion

Erosion
Sandstone
350
Shale
380
Limestone
450
260 million years ago
Regional Uplift
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion

Erosion
Sandstone
350
Shale
380
Limestone
450
250 million years ago
Regional Uplift
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Formation of the Grand Canyon

1. Regional Uplift, Tilting, or folding) causes
   Erosion
2. Erosion surface indicates gap in geologic record

Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
Limestone
450
Gabbro (790)
240 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion
2. Erosion surface, gap in geologic record
3. Continuous Sedimentation

Sedimentation (e.g., clay)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
220 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion
2. Erosion surface, gap in geologic record
3. Continuous Sedimentation

Sedimentation (e.g., lime mud)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
210 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion
2. Erosion surface, gap in geologic record
3. Continuous Sedimentation

Sedimentation (e.g., quartz sand)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
200 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion
2. Erosion surface, gap in geologic record
3. Continuous Sedimentation

Quartz Sandstone (200)
Sedimentation (e.g., immature sand)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
190 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion
2. Erosion surface, gap in geologic record
3. Continuous Sedimentation

Quartz Sandstone (200)
Arkose (190)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
180 million years ago
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Formation of the Grand Canyon

1. Regional Uplift, Tilting (or folding), Erosion
2. Erosion surface, gap in geologic record
3. Continuous Sedimentation
4. Sedimentation ceases

Arkose (190)
Quartz Sandstone (200)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
170 million years ago
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Formation of the Grand Canyon

1. Erosion of horizontal beds

Arkose (190)
Quartz Sandstone (200)
Erosion
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
160 million years ago
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Formation of the Grand Canyon

1. Erosion of horizontal beds
2. Loss of geologic record (i.e., Arkose)
3. Formation of a horizontal erosion surface

Arkose (190)
Quartz Sandstone (200)
Erosion
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
150 million years ago
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Formation of the Grand Canyon

1. Erosion of horizontal beds
2. Loss of geologic record (i.e., Arkose)
3. Formation of a horizontal erosion surface
4. Renewed Sedimentation

Arkose (190)
Quartz Sandstone (200)
Sedimentation (e.g., reef)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
140 million years ago
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Formation of the Grand Canyon

1. Erosion of horizontal beds
2. Loss of geologic record (i.e., Arkose)
3. Formation of a horizontal erosion surface
4. Renewed Sedimentation

Arkose (190)
Quartz Sandstone (200)
Limestone (140)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (280)
450
Limestone
Gabbro (790)
130 million years ago
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Formation of the Grand Canyon

1. Erosion of horizontal beds
2. Loss of geologic record (i.e., Arkose)
3. Formation of a horizontal erosion surface
4. Renewed Sedimentation

Arkose (190)
Quartz Sandstone (200)
Limestone (140)
Limestone (210)
Shale (220)
Sandstone
350
Shale
380
Gneiss (1,500)
Granite (290)
450
Limestone
Gabbro (790)
120 million years ago
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Formation of the Grand Canyon

• Deciphering Relative Ages
• Principles give sequences of geologic events
• Unconformities indicate gaps in the geologic
  record

Limestone
Quartz Sandstone
Disconformity
Angular Unconformity
Limestone
Shale
Sandstone
Shale
Gneiss
Granite
Limestone
Gabbro
Nonconformities
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Uplift and Erosion

• As the land is lifted up by tectonic forces
• A stream will attempt to maintain its base level
  by
• Cutting down into the rocks due to accelerated
  erosion

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The Grand Staircase
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Eastern Zion National Park