THE SIERRA NEVADA MOUNTAINS. Only the end Of 400 million years of history.
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Transcript of THE SIERRA NEVADA MOUNTAINS. Only the end Of 400 million years of history.
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THE SIERRA NEVADA THE SIERRA NEVADA MOUNTAINSMOUNTAINS
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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 SIERRASTHE 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-1Kern River-1 Controlled by ancient fault dating back to 2Controlled by ancient fault dating back to 2ndnd
SierrasSierras Fault = Kern Canyon FaultFault = Kern Canyon Fault Located primarily on Southern blockLocated primarily on Southern block TimingTiming
60 – 20 my, Mt. Whitney to Kernville to Colorado 60 – 20 my, Mt. Whitney to Kernville to Colorado RiverRiver
20 – 12 my, Mt. Whitney to Kernville to Caliente 20 – 12 my, Mt. Whitney to Kernville to Caliente Creek to Bena to San Joaquin ValleyCreek to Bena to San Joaquin Valley
12 – present, Mt. Whitney to Kernville to lower 12 – present, Mt. Whitney to Kernville to lower Kern River to San Joaquin ValleyKern River to San Joaquin Valley
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Kern River-2Kern River-2 Current Current
topographytopography
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Kern River-3Kern River-3
60 -20 my60 -20 my Topography Topography
much much differentdifferent
Empties Empties into into Colorado Colorado River to ERiver to E
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Kern River-4Kern River-4
20 – 12 my20 – 12 my Topography Topography
differentdifferent Empties into Empties into
San Joaquin San Joaquin basin SE of basin SE of Bakersfield Bakersfield (Bena)(Bena)
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Kern River-5Kern River-5
12 – present12 – present Topography Topography
similarsimilar Empties into Empties into
San Joaquin San Joaquin basin basin toward toward BakersfieldBakersfield
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Kern River-6Kern River-6
Ancient Lake Ancient Lake Isabella – Isabella – northnorth
Walker Lake – Walker Lake – southsouth
not on Kern not on Kern R.R.
12 - ~1 my12 - ~1 my
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ECONOMIC ECONOMIC RESOURCESRESOURCES
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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 EROSION—1850’s, 1930’s, 1980’s
• PLACER DEPOSITS BY 60+ MY OF STREAM SORTING AND DEPOSITION—1850’s, 1930’s
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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 gems—1920’s empress of China bought quantities of tourmaline
• Fine mineral samples
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facetted tourmaline (boron)facetted tourmaline (boron)
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Rough beryl (beryllium)Rough beryl (beryllium)
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Cut garnets (various)Cut garnets (various)
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pegmatite
• An odd igneous rock
• It contains concentrations of rare elements and forms rare minerals