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Sedimentary Rocks

Sedimentary Rocks

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Sedimentary Rocks

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  1. Sedimentary Rocks

  2. What is a sedimentary rock? • Sedimentary rocks are products of mechanical and chemical weathering • They account for about 5 percent (by volume) of Earth’s outer 10 kilometers • Contain evidence of past environments • Provide information about sediment transport • Often contain fossils

  3. What is a sedimentary rock? • Sedimentary rocks are important for economic considerations because they may contain • Coal • Petroleum and natural gas • Sources of iron, aluminum, and manganese

  4. Gravel Beach

  5. Talus Cones

  6. delta

  7. Owens River

  8. Meandering River

  9. Alluvial fans

  10. Sand Dunes

  11. Death Valley salt pan

  12. Playas

  13. Deep Springs Lake

  14. fringing reef

  15. Sandy Beach

  16. Spits

  17. Swamps

  18. Successive stages in coal formation

  19. coal

  20. Sedimentary Rocks

  21. Fossil Fish - 50 Million Year Old Lakes in southern Wyoming These fish tell us the Wyoming climate 50 million years ago. Sedimentary Rock made of fine-grained mudstone.

  22. Sedimentary Rocks • Sedimentary – form in water • Generally formed by the deposition, burial, compaction, and cementation of sediments (pieces of other rocks) • 3 Types • Clastic • Chemical (crystalline) • Organic (Bioclastic)

  23. 3 Types of Sedimentary Rocks: • Clastic (also called Detrial)—made of broken pieces of other rocks

  24. 3 Types of Sedimentary Rocks: Organic—remains of plants and animals are deposited in thick layers • Examples • Fossil rich limestone is made from the shells of ocean animals; used to make chalk

  25. 3 Types of Sedimentary Rocks: • Chemical—minerals dissolved in lakes, seas, or underground water Mineral crystals are made as the shallow water that has flooded the bottom of Death Valley evaporates. Click on image for full size (66K JPG)Courtesy of Martin Miller, University of Oregon

  26. Detrital sedimentary rocks • The chief constituents of detrital rocks include • Clay minerals • Quartz • Feldspars • Micas • Particle size is used to distinguish among the various types of detrital rocks

  27. Classification of sedimentary rocks • Two major textures are used in the classification of sedimentary rocks • Clastic • Discrete fragments and particles • All detrital rocks have a clastic texture • Nonclastic • Pattern of interlocking crystals • May resemble an igneous rock

  28. Detrital sedimentary rocks

  29. Detrital sedimentary rocks • Common detrital sedimentary rocks (in order of increasing particle size) • Shale • Mud-sized particles in thin layers that are commonly referred to as laminea • Most common sedimentary rock

  30. Lake Bed Deposits

  31. Shale containing plant remains

  32. Detrital sedimentary rocks • Sandstone • Composed of sand-sized particles • Forms in a variety of environments • Sorting, shape, and composition of the grains can be used to interpret the rock’s history • Quartz is the predominant mineral

  33. B. Descriptions of individual clastic rocks Arkose Graywacke Quartz Sandstone

  34. World’s Biggest Rock • The Ayers Rock is made up of arkose, a course-grained sandstone rich in feldspar at least 2.5 km thick. Uplifting and folding between 400-300 mya turned the sedimentary layers nearly 90 degrees to their present position. The surface has then been eroded.

  35. Graywacke

  36. Detrital sedimentary rocks • Alternating sequences of shale and sandstone exposed in the Grand Canyon. Shale cannot support steep cliffs or form erosion

  37. Detrital sedimentary rocks • Conglomerate and breccia • Both are composed of particles greater than 2mm in diameter • Conglomerate consists largely of rounded gravels • Breccia is composed mainly of large angular particles

  38. B. Descriptions of individual clastic rocks Breccia Conglomerate

  39. Conglomerate

  40. Conglomerate

  41. Breccia

  42. breccia1

  43. Characteristics of sedimentary rocks • Sorting – the distribution of grain sizes in a rock Sorting depends on properties of the depositing agent

  44. Graded Beds

  45. Sorting Glacier deposit – poorly sorted Sand dune – well sorted