Geology of the Feather River Where does one start? NERDS 2006 Teresa Kennedy

Some Understandings Plate Tectonics (which is different from continental drift) 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 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 Plate margins are places of brittle and ductile deformation The past is the key to the present…geologic processes are dynamic The past is the key to the present…geologic processes are dynamic

Geologic Time Scale Four Major Eras: Four Major Eras: Precambrian: Age of Algae Precambrian: Age of Algae Paleozoic: Age of Fish Paleozoic: Age of Fish Mesozoic: Age of Dinosaurs Mesozoic: Age of Dinosaurs Cenozoic: Age of Mammals Cenozoic: Age of Mammals

Overview Igneous, metamorphic, and sedimentary rocks Igneous, metamorphic, and sedimentary rocks Some tilted, some flat-lying Some tilted, some flat-lying Submarine and subaerial rocks Submarine and subaerial rocks Much of the rock record missing due to erosion Much of the rock record missing due to erosion Fossils Fossils Heavy vegetation Heavy vegetation Glaciations Glaciations

Precambrian ~ 4.5 billion years ago ~ 4.5 billion years ago Until 544 million years ago… Until 544 million years ago… Feather River area was at the bottom of the ocean Feather River area was at the bottom of the ocean No rocks this old are exposed anywhere close to there! No rocks this old are exposed anywhere close to there!

Paleozoic 544 million years to 255 million years ago 544 million years to 255 million years ago Western margin of North American craton was 600 – 700 miles to the east Western margin of North American craton was 600 – 700 miles to the east 20,000 – 30,000 feet of rock deposited in deep ocean 20,000 – 30,000 feet of rock deposited in deep ocean Chert (formed from radiolaria) Chert (formed from radiolaria) Volcanic ash and breccia from volcanoes caused by subduction to west. Volcanic ash and breccia from volcanoes caused by subduction to west.

Mesozoic 225 million years to 65 million years 225 million years to 65 million years Deformation: folding and faulting from collision with other crustal pieces Deformation: folding and faulting from collision with other crustal pieces Layers tilted up to 60 degrees Layers tilted up to 60 degrees Metamorphism from igneous plutons rising from subducted magma. Metamorphism from igneous plutons rising from subducted magma. Oldest plutons are to the west Oldest plutons are to the west

Cenozoic 65 million years to present 65 million years to present Modern volcanic activity related to spreading of Basin and Range Modern volcanic activity related to spreading of Basin and Range Crest of Sierra Nevada is to the west Crest of Sierra Nevada is to the west Uplift Uplift ErosionErosion Change in climateChange in climate Glaciers Glaciers ErosionErosion Changes in drainage, soils, vegetationChanges in drainage, soils, vegetation