The Cenozoic

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The Cenozoic

• The last era of the geologic history

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The Cenozoic

• We can now recognize the continents
• Half of the ocean floors we see today formed in
  the Cenozoic
• The birth of California and San Andreas fault

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The Cenozoic

• Central and South America were merged by the
  Panamanian land bridge, thus creating the Gulf
  stream currents in the Atlantic used to move
  westward
• Northwestern Europe got warmer as a result

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The Cenozoic

• Scandinavia and Greenland separated
• Australia separated from Antarctica before the,
  Antarctica had a milder climate, warmed by
  south-moving currents

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The Cenozoic

• The Red Sea and Gulf of Aden formed
• India collided with Eurasia most of the Tethys
  seaway disappeared
• The Himalayas and the Alps formed
• Then, a cooling period produced the Pleistocene
  ice age

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Red Sea
Gulf of Aden
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The Red Sea
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Cenozoic in North America

• In the East Nothing too exciting
• The Appalachians were being eroded
• Florida was slowly emerging from the sea
• 2,500 m of carbonates were deposited (like the
  Bahamas Banks)
• The northern part was uplifted in the end of the
  Tertiary

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Cenozoic in North America

• In the South
• The thickest sedimentary strata were deposited in
  the Gulf of Mexico up to 10,000 m
• Tejas transgression moved north
• Deltaic sands and offshore shales interfingered
  (smaller transgressions and regressions)
• Today, ideal conditions for oil reservoirs

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Cenozoic in North America

• The High Plains and the Rocky Mountains area
• Both erosion and terrestrial deposition mixed
  with volcanic ash except for the cannonball Sea
  (a remnant of the Zuni transgression in the Late
  Cretaceous)
• Uplift and more erosion shaped the Rocky Mountains

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Cannonball Sea
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The high Plains and the Rocky Mountains area

• Lower Tertiary sedimentary rocks (Paleocene)
• Fort Union Formation (1,800 m)
• Contains much low-grade coal
• Formed in intermontane basins in the Rocky
  Mountains

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The high Plains and the Rocky Mountains area

• Eocene rocks Wasatch and Green River Formations
  stream and lake deposits (large, shallow lakes)
• The Green River basin contains extremely
  well-laminated lake deposits now oil shales

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Green River Basin
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Green River Formation
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The high Plains and the Rocky Mountains area

• How does oil shale form?
• Algal material within the sediments broke down to
  waxy hydrocarbons (kerogens) and later yielded
  large quantities of petroleum
• It is disseminated in the rock, so it is
  difficult to extract
• Fossils are well-preserved fishes, insects,
  palms

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Fish fossil from Green River Formation
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The high Plains and the Rocky Mountains area

• Late Eocene and Oligocene
• The Yellowstone National Park was quite explosive
  with much activity
• Volcanic ash covered nearby areas
• The White River Formation formed
• Makes up the badlands in South Dakota
• Famous because whole skeletons f Tertiary mammals
  are preserved in flood-plain deposits

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The high Plains and the Rocky Mountains area

• Late Eocene and Oligocene
• Huge amounts of volcanic ash was deposited in a
  lake near Florissant, Colorado
• Contains well-preserved insects, plants, and birds

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Fossil insects from Oligocene tuff
beds, Florissant, Colorado
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The high Plains and the Rocky Mountains area

• Late Tertiary
• The Teton Range formed from normal faulting up
  to 6,000 m displacement
• The face of the Tetons is really a fault scarp
• Extensional faulting

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The Teton range
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The high Plains and the Rocky Mountains area

• Late Tertiary
• Basin and Range Province experienced extension
  (an extensional basin)
• Normal faults
• Linear mountain belts
• Intermontane lakes formed evaporites

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Basin and Range Province
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Geological section across the Basin and Range
Province
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The high Plains and the Rocky Mountains area

• Why do we have extension in the middle of the
  continent?
• There are several theories
• A subducted spreading center but no eastward
  deformation, so, lack of evidence)
• The Basin and Range Province is an adjustment to
  strike-slip motion in California (early Miocene)

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The high Plains and the Rocky Mountains area

• Why do we have extension in the middle of the
  continent?
• 3) A remnant ocean plate from an earlier episode
  of subduction a partially molten mass pushed
  upward (boyancy)
• 4) Convection similar to regular
  breaking-apart of the continents

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Convection
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The high Plains and the Rocky Mountains area

• Miocene (16-13 Ma ago)
• Columbia Plateau
• Volcanic flow (lava) layers from fissures
• Individual flows are 30-150 m thick
• Total accumulation may reach 5 km
• Cover 500,000 km2

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Columbia Plateau
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The high Plains and the Rocky Mountains area

• Pliocene
• Uplift of the Colorado Plateau (did not deform in
  the Mesozoic)
• Uplift occurred about 10-5 Ma ago
• The Grand Canyon formed from erosion by the
  Colorado River 2,600 m deep
• The Colorado River has eroded into pre-Cambrian
  rocks

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The Grand Canyon
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The high Plains and the Rocky Mountains area

• The Sierra Nevada
• Jurassic Nevadan orogeny
• Tertiary eroded granite exposed
• Pliocene, Pleistocene uplifted along normal
  faults (up to 4,000 m)
• The Cascade Range
• Volcanism began 4 Ma ago
• Crater Lake (Oregon) formed 6,000 years ago
• Why the volcanic activity?

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The Sierra Nevada
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The uplifted Sierra Nevada batholith
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Mount St. Helens
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Mount St. Helens
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The formation of Crater Lake
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Wizard Island, Crater Lake
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The west coast

• Subduction of the Farallon Plate responsible
  for the orogenies in the Mesozoic
• Cenozoic subducted at a faster rate than basalt
  could replace the gap at the spreading center
  so even the spreading ridge was subducted

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The west coast

• All that remains today of the Farallon Plate is
  Juan de Fuca and Cocos Plates
• The Farallon Plate moved S-E and the Pacific
  Plate N-W. So, when subducted, it slid sideway to
  the North instead of plunging under the continent
• Baja, California became part of the northward
  movement of the Pacific Plate