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Fig 5.12 WHERE DO SEDIMENTS ORIGINATE? WEATHERING OF PRE-EXISTING ROCKS.

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Presentation on theme: "Fig 5.12 WHERE DO SEDIMENTS ORIGINATE? WEATHERING OF PRE-EXISTING ROCKS."— Presentation transcript:

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2 Fig 5.12 WHERE DO SEDIMENTS ORIGINATE? WEATHERING OF PRE-EXISTING ROCKS

3 HOW ARE SEDIMENTS MOVED? (ERODED/TRANSPORTED) water wind ice gravity

4 WHERE DO SEDIMENTS ACCUMULATE?

5 75% OF SURFACE ROCKS ARE SEDIMENTARY.

6 JUST LIKE IGNEOUS ROCKS: TEXTURE MEANS SIZE OF GRAINS Fine-grained Coarse- grained

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9 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)

10 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

11 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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16 Layered nature of sedimentary rocks reflects depositional processes

17 What are SOURCES of sediments for sedimentary rocks?

18 Mechanical Weathering

19 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

20 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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22 Conglomerate & breccia very coarse-grained detrital rocks formed in high-energy environments conglomerate breccia

23 Sandstone* a coarse-grained detrital rocks formed in a medium to high-energy environment. * composition of grains is commonly quartz

24 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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27 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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29 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

30 CaCO 3 + 2 H + + (CO 3 ) 2- Ca 2+ + 2 (HCO 3 ) - Formation of Limestone Precipitation of Calcite solid solution solution solution 30

31 Rock Salt: a chemical rock formed from evaporation of water (evaporite)

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33 Sedimentary processes and life processes are intermingled Fossils are evidence of past life. They are concentrated in sedimentary rocks.

34 What are fossil fuels? Coal Oil Natural gas All are organic materials with C-H bonds Fossils fuels are concentrated in sedimentary rocks.

35 Geologic requirements for oil production: source rock reservoir rock trap

36 What is proposed relationship between fossil fuels and global warming?

37 Global carbon cycle

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40 Non-metallic mineral resources are concentrated in sedimentary rocks. Examples? What processes concentrate these materials?

41 Limestone Quarry

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43 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?

44 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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