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Sediments and Sedimentary Rocks

Learn about sedimentary rocks, sediment stages, types and formation processes, as well as the characteristics of detrital and chemical sedimentary rocks. Explore depositional environments, sediment structures, and interpreting geological events.

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Sediments and Sedimentary Rocks

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  1. Sediments and Sedimentary Rocks L - 6: cd/EM - E Tom Bean/DRK

  2. 5 % by volume of the upper crust 75% by area of continental areas Often the only record of geologic events: e.g. The Himalayas will someday be sandstone Sedimentary rocks

  3. Sedimentary Stages in the Rock Cycle

  4. DETRITAL & CLASTIC - Rock resulting from the consolidation of loose sediment that has been derived from previously existing rocks and accumulated in layers CHEMICAL - Rock formed by the precipitation of minerals from solution by either organic or inorganic processes 2 KINDS OF SEDIMENTARY ROCKS

  5. Movement of sediment by wind, ice or water (GEOLOGIC AGENTS). Mode of transport produces distinctive deposits. Deposit as layers - beds/strata Transport and deposition of clastic sediments

  6. Sorting: measure of the variation in the range of grain sizes in a clastic rock or sediment Well-sorted sediments indicate that they have been subjected to prolonged water or wind action. Poorly-sorted sediments are either not far-removed from their source or deposited by glaciers. Transport affects the sediment in several ways -

  7. Sorting Well-sorted Poorly-sorted

  8. Well-sorted Sand Rex Elliott

  9. Poorly-sorted Sand Rex Elliott

  10. Roundness: measure of how rounded the corners are Sphericity: measure of how much it is like a sphere * Sorting, roundness, and sphericity all increase with LENGTH of transport. Transport affects the sediment in several ways - SHAPE

  11. Sorting Roundness

  12. Largely based on the size of the particles, which may be anything. Conglomerate (poorly sorted/round) Breccia (poorly sort/angular) Sandstone (quartzite, arkose, greywacke) Mudstone Siltstone Shale - most common rock on continents Types of detrital rocks

  13. Conglomerate Breck Kent

  14. Sandstone Breck Kent

  15. Shale D. Cavagnaro/Visuals Unlimited

  16. CHEMICAL ROCK- Rock formed by the precipitation of minerals from solution by either organic or inorganic processes SEDIMENTARY ROCKS

  17. Limestone CaCO3 Chert SiO2 Salt NaCl, KCl Gypsum CaSO4 • 2H2O Coal altered organic debris Types of chemical sedimentary rocks

  18. Limestone Breck Kent

  19. Halite Breck Kent

  20. Chert Breck Kent

  21. Fossiliferous Limestone Peter Kresan

  22. Restricted environments such as Mediterranean Sea & Texas coast Minerals precipitate according to solubility. Gypsum Halite CaSO4 •2H2O NaCl Chemical environments: Evaporites

  23. One Model for the Formation of Evaporites

  24. Clear water — away from big rivers (or volcanoes) Warm water — subtropical to tropical Shallow water -- two reasons: Organic: sunlight only penetrates to about 100 m Inorganic: CCD so carbonates dissolve Chemical environments: Carbonates

  25. Foraminifer in the Eye of a Needle Chevron Corporation

  26. Coral Reef Surrounding Volcanic Island Jean-Marc Truchet/Tony Stone Worldwide

  27. Common Sedimentary Environments

  28. • Sedimentary structures • Sorting, roundness, sphericity • Sequence & kinds of beds Clues to interpreting sedimentary depositional environments

  29. Particular structural features can give information about the environment of deposition. Structures also help determine if a bed is right-side-up — important in deformed rocks Sedimentary structures

  30. Cross-bedded Sandstone Peter Kresan

  31. Varves record annual cycles in glacial lakes Turbidity currents S. C. Porter

  32. Modern Rippled Sand Raymond Seiver

  33. Ancient Ripple-marked Sandstone Reg Morrison/Auscape

  34. Fig. 7.9

  35. Mudcracks MODERN ANCIENT

  36. Bioturbation Tracks and Tunnels Chip Clark

  37. From Peat to Coal

  38. The end

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