THE SIERRA NEVADA MOUNTAINS

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THE SIERRA NEVADA MOUNTAINS
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Only the end

• Of 400 million years of history

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Miscellaneous epeiric seas

• From about 600 my BP

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THE THREE SIERRAS

• 250 150 million years 1st Sierras
• 120 60 million years 2nd Sierras
• 20 my present 3rd Sierras

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1st SIERRAS
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1ST SIERRAS

• Timing - 250 150 my
• Part of Pangea
• Subduction formed
• Little evidence
• Later intrusion and metamorphism
• Erosion (twice)

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2nd SIERRAS
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2ND SIERRAS

• Timing - 120-60 my
• N.A. separated and moving westward
• Subduction formed
• Evidence partially destroyed by erosion

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Plate motions and the 2nd Sierras
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40my of erosion to the 2nd Sierras

• 60-20 my
• no subduction
• erosion

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3rd SIERRAS
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Block faulting to formthe 3rd Sierras

• 20 my eastern part southern block is uplifted
  internal faulting at 12 my ?uplift at 9 my
• 9 my main block is tilted to west
• Erosion continued for 20 my but slightly
  different on the two blocks

N
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Details about the blocks

• Details are dependent on datable lavas and
  pyroclastic material, or
• on dateable terminal sediments of the Kern River.
• Not much and not much done!

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Erosion on the 3rd Sierras

• Streams until the ice ages
• Main block E and W after 9 my tilting
• Southern block S by the Kern River ?60 my to
  present
• Valley glaciers off and on 1.6 my to present for
  the higher parts

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Kern River-1

• Controlled by ancient fault dating back to 2nd
  Sierras
• Fault Kern Canyon Fault
• Located primarily on Southern block
• Timing
• 60 20 my, Mt. Whitney to Kernville to Colorado
  River
• 20 12 my, Mt. Whitney to Kernville to Caliente
  Creek to Bena to San Joaquin Valley
• 12 present, Mt. Whitney to Kernville to lower
  Kern River to San Joaquin Valley

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Kern River-2

• Current topography

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Kern River-3

• 60 -20 my
• Topography much different
• Empties into Colorado River to E

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Kern River-4

• 20 12 my
• Topography different
• Empties into San Joaquin basin SE of Bakersfield
  (Bena)

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Kern River-5

• 12 present
• Topography similar
• Empties into San Joaquin basin toward Bakersfield

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Kern River-6

• Ancient Lake Isabella north
• Walker Lake south
• not on Kern R.
• 12 - 1 my

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ECONOMIC RESOURCES
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TOURISM

• Summer hiking, backpacking, rock climbing,
  camping, boating, fishing, sightseeing, (in
  selected areas) hunting
• Winter skiing
• Mammoth area
• Donner Pass area
• Several other smaller areas

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GOLD-1

• Foothills E of Sacramento

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GOLD-2

• DEEP HYDROTHERMAL VEINS EXPOSED BY 60 MY OF
  EROSION1850s, 1930s, 1980s
• PLACER DEPOSITS BY 60 MY OF STREAM SORTING AND
  DEPOSITION1850s, 1930s

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TUNGSTEN

• DEEP HYDROTHERMAL VEINS EXPOSED BY 60 MY OF
  EROSION
• Hydrothermal fluids CaCO3
• Primarily WWII

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SOUTHERN GEM MINES

• Tourmaline, beryl, and garnet
• From the shallow pegmatites of San Diego and
  Riverside counties
• Varied depending on price for gems1920s empress
  of China bought quantities of tourmaline
• Fine mineral samples

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facetted tourmaline (boron)
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Rough beryl (beryllium)
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Cut garnets (various)
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pegmatite

• An odd igneous rock
• It contains concentrations of rare elements and
  forms rare minerals