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Clastic sediments can’t be deposited everywhere at once!

Clastic sediments can’t be deposited everywhere at once! Need older rocks as a source of clasts (fragments of older rocks). Most sedimentary rocks accumulate in low-lying basins. basin. 1. Places where sedimentary rocks accumulate. 2. Sediments can accumulate between mountain ranges.

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Clastic sediments can’t be deposited everywhere at once!

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  1. Clastic sediments can’t be deposited everywhere at once! Need older rocks as a source of clasts (fragments of older rocks). Most sedimentary rocks accumulate in low-lying basins. basin 1

  2. Places where sedimentary rocks accumulate 2

  3. Sediments can accumulate between mountain ranges. 3

  4. Basin and Range Province Intermontane Basins 4

  5. Erosion Deposition Fault 5

  6. Uplifted blocks of the Middle Rockies 6

  7. Sedimentary basins of the Middle Rockies 7

  8. Bighorn Mountains The basins lie adjacent to the uplifts and received thick sediment fills during and after mountain-building. Bighorn Basin 8

  9. The basins lie adjacent to the uplifts and received thick sediment fills during and after mountain-building. Gillette, Wyoming Powder River Basin (huge coal deposits) 9

  10. Exposures of Metamorphic Rocks 10

  11. Metamorphic Rock: Any rock formed from preexisting rocks by solid state recrystallization driven by changes in temperature and pressure and chemical reaction of fluids. p. G-12 textbook mica calcite know 11 quartz

  12. Deformed mudcracks in a slate 12

  13. Stretched pebbles in a metaconglomerate 13

  14. Quartzite in the Medicine Bow Range, Wyoming Note remnants of bedding (nearly vertical) 14

  15. Crossbedding (originally in sandstone) still visible in 2 billion-year-old quartzite. There is no metamorphic bedrock at surface in Nebraska, but quartzite boulders were brought to eastern NE from MN and SD by recent glaciers. 15

  16. Contact Metamorphism 16

  17. Example of Contact Metamorphism Marble quarry near Aspen, CO Stone for Lincoln Memorial quarried here more about the quarry 17

  18. Fossils in limestone have been replaced by large, interlocking crystals of calcite. Diagonal lines are from holes drilled for blasting. 18

  19. Regional Metamorphism -the observations “the roots of mountain chains” 19

  20. Regionally metamorphosed rocks often show evidence of intense deformation. 20

  21. 21

  22. Foliation- a planar feature developed in metamorphic rocks produced by the growth of secondary minerals. Foliation in this sketch is vertical 22

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  24. Slaty cleavage in a slate quarry 24

  25. Schist Black Hills, SD Aligned micas reflect light to give outcrop a silvery sheen. 25

  26. Aligned micas in two different samples of schist foliation 26

  27. Gneiss-- minerals segregated into light and dark bands 27

  28. 28

  29. Metamorphism--the plate tectonics model Nearly all metamorphism takes place at active plate boundaries. 29

  30. Important conclusion on Regional Metamorphism: Vertical foliation is common, and develops perpendicular to horizontal stresses generated at convergent plate boundaries. 30

  31. From Slide #9 Important conclusion on Regional Metamorphism: Vertical foliation is common, and develops perpendicular to horizontal stresses generated at convergent plate boundaries. 31

  32. foliation 32

  33. Metamorphism also takes place at divergent plate boundaries. 33

  34. Alvin is a 3-passenger research submarine that has made more than 2000 dives since 1964. Scientists in Alvin discovered the spectacular hot springs (“Black Smokers”) on the deep sea floor in 1977. 34

  35. Water from these springs can reach 400 C. 35

  36. Where does the energy for life come from? The sun (fusion of hydrogen) The earth (fission of radioactive elements) both

  37. Where does the energy for life come from? The sun (fusion of hydrogen) The earth (fission of radioactive elements) both 37

  38. “Godzilla”,a 15-story-high black smoker, was discovered on the Juan de Fuca Ridge in the Eastern Pacific in 1991. It toppled over in 1996. 38

  39. Hot water springs are abundant on the seafloor at and near divergent plate boundaries. Dehydration during subduction Hydrationduring metamorphism Conclusion: By adding water (hydration) to the minerals in basalt, metamorphism at divergent boundaries allows volcanism at convergent boundaries. 39

  40. Structure of Rock Bodies Chapter 7 40

  41. Bighorn Mountains, Bighorn Basin, WY 41

  42. Strike and dip are terms used to efficiently describe the orientation of tabular or planar geologic features.Tabular features: lava flows, sills, dikes, layers of sedimentary rockPlanar features: faults, joints 42

  43. Strike is the compass direction of the intersection of a horizontal plane and some other planar or tabular feature (such as a rock layer or fault) 43

  44. Water surface is horizontal plane 44

  45. The dip of a plane is the direction of its inclination, and the angle between it and a horizontal plane. Remember: Strike and dip describe the orientation of tabular or planar geologic features-- not the land surface 45

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