Transcript Geology of the Feather River

Geology of the Feather
River
Where does one start?
NERDS 2006
Teresa Kennedy
Some Understandings
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Plate Tectonics (which is different from
continental drift)
Subduction results in remelted material
(magma) which rises because it is less
dense to form new crust
Plate margins are places of brittle and
ductile deformation
The past is the key to the
present…geologic processes are dynamic
Geologic Time Scale
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Four Major Eras:
Precambrian: Age of Algae
Paleozoic: Age of Fish
Mesozoic: Age of Dinosaurs
Cenozoic: Age of Mammals
Overview
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Igneous, metamorphic, and sedimentary
rocks
Some tilted, some flat-lying
Submarine and subaerial rocks
Much of the rock record missing due to
erosion
Fossils
Heavy vegetation
Glaciations
Precambrian
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~ 4.5 billion years ago
Until 544 million years ago…
Feather River area was at the bottom
of the ocean
No rocks this old are exposed
anywhere close to there!
Paleozoic
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544 million years to 255 million years ago
Western margin of North American craton
was 600 – 700 miles to the east
20,000 – 30,000 feet of rock deposited in
deep ocean
Chert (formed from radiolaria)
Volcanic ash and breccia from volcanoes
caused by subduction to west.
Mesozoic
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225 million years to 65 million years
Deformation: folding and faulting
from collision with other crustal
pieces
Layers tilted up to 60 degrees
Metamorphism from igneous plutons
rising from subducted magma.
Oldest plutons are to the west
Cenozoic
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65 million years to present
Modern volcanic activity related to
spreading of Basin and Range
Crest of Sierra Nevada is to the west
Uplift
• Erosion
• Change in climate
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Glaciers
• Erosion
• Changes in drainage, soils, vegetation