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Geology of the Feather River. Where does one start? NERDS 2006 Teresa Kennedy. Some Understandings. 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
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Geology of the Feather River Where does one start? NERDS 2006 Teresa Kennedy
Some Understandings • 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 • Four Major Eras: • Precambrian: Age of Algae • Paleozoic: Age of Fish • Mesozoic: Age of Dinosaurs • Cenozoic: Age of Mammals
Overview • 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 • ~ 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 • 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 • 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 • 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 • Glaciers • Erosion • Changes in drainage, soils, vegetation