Geology Chapters 5,6,7,12

Geology Chapters 5,6,7,12 - Chapter 5 Sedimentation Rocks...

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Chapter 5 - Sedimentation: Rocks Formed by Surface  Processes Thursday, February 14, 2008 10:39 AM Sedimentary Rocks o Composed of Sediments o Sediments      - particles of preexisting rocks of various sizes Include gravel, sand, silk, mud (clay) Material that has settled out of a liquid o Sedimentation     Involve the material in water coming out of this material o In General All sediments have a source  where they are created All sediment are transported  by some sort of surface processes All sediments are deposited  as they settle from suspension in an  environment o The variation of these things will determine the type of sediment o Examples Beach -  Sand eventually becomes sandstone Swamp - Mud eventually becomes shale, coals and shells Has water coming in and water coming out, next to shoreline Desert - no water, wind helps produce sandstone o Environment dictates the rock type Variables: The agent of transport (wind, water, ice) and its strength (strong,  moderate, weak) The type (fresh vs. salt) and amount of water Topography (mountain, lowland, coastal plain, shallow ocean,  deep ocean) Biological Activity (Reef formers, shell producers) Climate (arid, humid, polar, etc.) 3 general types: Continental or nonmarine - land and freshwater environments Lakes: Arid or Humid - mud at bottom (Shale) Alluvial: River- transported sediments (moving water) Desert: Wind-blown sediments - dry (wind) Mainly produce chemical sedimentary rocks Glacial: Ice-transported sediments
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Typically form in the mountains Shoreline or transitional: separate continental and marine  environment Marine - ocean (saltwater) environments  o Types of Sediments Clastic Sediments - produced by weathering of pre-existing rocks Weathering - the breakdown Physical Weathering - big rocks  mechanically  fragmented  or broken into smaller particles Chemical Weathering - components of rocks are  chemically  altered or dissolved Erosion by wind, water, ice, or gravity mobilizes the particles Particles are deposited in a sink they settle out of suspension Sediment source is outside of the basin of deposition Chemical Sediments - produced by precipitation of dissolved solids Most commonly associated with  evaporation Sediment source is within the basin of deposition Examples: Halite (rock salt), Gypsum; form in special conditions Biological Sediments - secreted by biological activity Products include seashells and bones Sediment source is within the basin of deposition Classified by the chemical composition and / or the size of 
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This note was uploaded on 07/07/2009 for the course GEOL 1001 taught by Professor Baksi during the Spring '07 term at LSU.

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Geology Chapters 5,6,7,12 - Chapter 5 Sedimentation Rocks...

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