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Sedimentary Rocks

Sedimentary Rocks. Sedimentary Rocks. Made up of different types of sediments Loose fragments of rock, minerals & organic material . Characteristics. Determined by: Source of sediment Way the sediment was moved Deposition conditions. Formation.

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Sedimentary Rocks

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  1. Sedimentary Rocks

  2. Sedimentary Rocks • Made up of different types of sediments • Loose fragments of rock, minerals & organic material

  3. Characteristics • Determined by: • Source of sediment • Way the sediment was moved • Deposition conditions

  4. Formation • Sediments are transported by: wind, water or ice • Source determines the composition • Once sediment is deposited: (2 main processes) • Compaction • Cementation

  5. Classification • Classified according to: • Processes by which they form • Composition of the rock • 3 main classes: • Chemical • Organic • Clastic *Each class can contain their own groups

  6. Chemical Sedimentary Rocks • Forms from minerals that were once dissolved in water • 2 ways: • Minerals precipitate out of the water • Water evaporates leaving minerals behind, evaporites

  7. Organic Sedimentary Rocks • Forms from the remains of living things • Calcium Carbonates (CaCo3)

  8. Clastic Sedimentary Rocks • Rock fragments that are compacted & cemented together • Classified by the size of their sediments • Conglomerate-2mm to boulders • Breccia-angular & sharp edges • Sandstones-sand-sized grains cemented together • Shales-clay-size particles that are compacted & cemented together

  9. Sedimentary Rocks: Part 2

  10. Characteristics of Clastic Sediments • Physical characteristics are determined by: • Distance the particles move • Agent that moves the particles • 2 characteristics that are affected by transport: • Sorting • Angularity

  11. Sorting • Tendency for currents of air or water to separate sediments according to size • Well sorted—all grains are about the same size • Poorly sorted—grains are all different sizes • In between

  12. Angularity • How round & smooth or angular & uneven a sediment is can tell about the distance the sediment has traveled • The farther sediment travels from its source, the smoother the particles of sediment become

  13. Sedimentary Rock Features • Depositional environments—setting in which sediment was deposited • Common environments: • Rivers, lakes, deltas, beaches & oceans • Have different characteristics that create specific structures

  14. 7 Sedimentary Rock Features • Stratification • Cross-beds • Graded Bedding • Ripple Marks • Mud Cracks • Fossils • Concretions

  15. Stratification • Layering of rock • Shows when the conditions of sediment deposition change

  16. Cross Beds • Slanting layers that form within beds • Generally form in sand dunes or river beds

  17. Graded Bedding • Occurs when different sizes & shapes of sediment settle to different levels. • Usually largest grains are on bottom & smaller on top • Reverse-grading can happen

  18. Ripple Marks • Caused by the action of wind or water on sand. • Indicate that a beach or river was once present

  19. Mud Cracks • Form when muddy deposits dry & shrink • Found on dry lake beds or flood plains

  20. Fossils • Remains or traces of ancient plants & animals

  21. Concretions • Form when minerals precipitate from fluids build up around a nucleus

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