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Published byAnnis Hawkins Modified over 9 years ago
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Fig 5.12 WHERE DO SEDIMENTS ORIGINATE? WEATHERING OF PRE-EXISTING ROCKS
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HOW ARE SEDIMENTS MOVED? (ERODED/TRANSPORTED) water wind ice gravity
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WHERE DO SEDIMENTS ACCUMULATE?
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75% OF SURFACE ROCKS ARE SEDIMENTARY.
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JUST LIKE IGNEOUS ROCKS: TEXTURE MEANS SIZE OF GRAINS Fine-grained Coarse- grained
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Sedimentary Rocks : Form in surface environments (75% of earth’s surface) Classified according to texture (in part) Reflect conditions of environment of formation Accumulate in layers over time (can be “read” like pages in a book)
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JUST LIKE IGNEOUS ROCKS: TEXTURE IN SEDIMENTARY ROCKS IS A MEANS TO CLASSIFY ROCKS BUT ALSO TELLS US ABOUT FORMATION OF ROCK … TEXTURE RELATES TO ENERGY OF ENVIRONMENT OF DEPOSITION
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WATER SORTS SEDIMENTS ACCORDNG TO SIZE, SO TEXTURE TELLS US ABOUT ENERGY OF E.O.D. Increasing energy = Increasing particle size
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Layered nature of sedimentary rocks reflects depositional processes
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What are SOURCES of sediments for sedimentary rocks?
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Mechanical Weathering
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Chemical Weathering KAlSi 3 O 8 + H + + HCO 3 - + H 2 O ►► Potassium feldspar Al 2 Si 2 O 5 (OH) 4 + K + + HCO 3 - + SiO 2 Clay mineral Carried away in solution Introduced in solution
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Products from mechanical /chemical wxg Solids (residuals) Dissolved minerals From chem. wxg (in solution) secondary minerals from chemical wxg (clays, iron oxides) Primary minerals from mechanical wxg (quartz sand) Minerals + organics = SOIL DETRITAL (CLASTIC) SED RX CHEMICAL SED RX
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Conglomerate & breccia very coarse-grained detrital rocks formed in high-energy environments conglomerate breccia
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Sandstone* a coarse-grained detrital rocks formed in a medium to high-energy environment. * composition of grains is commonly quartz
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Shale* a fine-grained detrital rock formed in a low-energy environment (most common sedimentary rock). * Composition of grains is almost always clay
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Limestone* a chemical rock formed in a variety of environments, often with the assistance of organisms (most common chemical sedimentary rock). *composition is always calcite (CaCO 3 ), grain size is variable
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Solution of calcite CO 2 + H 2 0 ► H 2 CO 3 CaCO 3 + H 2 CO 3 ► Ca 2+ + 2 (HCO 3 ) - Weathering Chemical Weathering Processes : solid solution solution solution 29
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CaCO 3 + 2 H + + (CO 3 ) 2- Ca 2+ + 2 (HCO 3 ) - Formation of Limestone Precipitation of Calcite solid solution solution solution 30
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Rock Salt: a chemical rock formed from evaporation of water (evaporite)
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Sedimentary processes and life processes are intermingled Fossils are evidence of past life. They are concentrated in sedimentary rocks.
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What are fossil fuels? Coal Oil Natural gas All are organic materials with C-H bonds Fossils fuels are concentrated in sedimentary rocks.
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Geologic requirements for oil production: source rock reservoir rock trap
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What is proposed relationship between fossil fuels and global warming?
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Global carbon cycle
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Non-metallic mineral resources are concentrated in sedimentary rocks. Examples? What processes concentrate these materials?
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Limestone Quarry
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Crushed stone Price: $6.80 per ton Volume: 1.1 billion tons Value? Relative cost of development? Copper Price: $3,230 per ton Volume: 2.2 million tons Value? Relative cost of development?
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Chemical Weathering KAlSi 3 O 8 + H + + HCO 3 - + H 2 O ►► Potassium feldspar Al 2 Si 2 O 5 (OH) 4 + K + + HCO 3 - + SiO 2 Clay mineral Carried away in solution Introduced in solution
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