THE SIERRA NEVADA THE SIERRA NEVADA MOUNTAINSMOUNTAINS

Only the end• Of 400 million years of history

Miscellaneous epeiric seas

• From about 600 my BP

THE THREE SIERRASTHE THREE SIERRAS

• ~ 250 – 150 million years = 1st Sierras

• ~ 120 – 60 million years = 2nd Sierras

• ~ 20 my – present = 3rd Sierras

1st SIERRAS

1ST SIERRAS

• Timing - ~ 250 – 150 my

• Part of Pangea

• Subduction formed

• Little evidence– Later intrusion and metamorphism– Erosion (twice)

2nd SIERRAS

2ND SIERRAS

• Timing -~ 120-60 my

• N.A. separated and moving westward

• Subduction formed

• Evidence partially destroyed by erosion

Plate motions and the 2nd Sierras

40my of erosion to the 2nd Sierras

• ~60-20 my• no subduction• erosion

3rd SIERRAS

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

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!

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

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

Kern River-2Kern River-2 Current Current

topographytopography

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

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)

Kern River-5Kern River-5

12 – present12 – present Topography Topography

similarsimilar Empties into Empties into

San Joaquin San Joaquin basin basin toward toward BakersfieldBakersfield

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

ECONOMIC ECONOMIC RESOURCESRESOURCES

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

GOLD-1

• Foothills E of Sacramento

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

TUNGSTEN

• DEEP HYDROTHERMAL VEINS EXPOSED BY 60+ MY OF EROSION

• Hydrothermal fluids + CaCO3

• Primarily WWII

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

facetted tourmaline (boron)facetted tourmaline (boron)

Rough beryl (beryllium)Rough beryl (beryllium)

Cut garnets (various)Cut garnets (various)

pegmatite

• An odd igneous rock

• It contains concentrations of rare elements and forms rare minerals