LECTURE 12

LECTURE 12

DEFORMATION OF ROCKS
1. respondsible: Earth's landscape, sub-surface structures that host petroleum accum.
2. 2 main types
  1. Brittle
    1. rock break by fracturing
    2. transition zone: 10-15km depth
  2. Ductile
    1. rock deform by flow&fold
    2. transition zone: 10-15km depth
3. Caused by
  1. Stress
    1. Compression
      1. squeeze- thick material
    2. Extension
      1. pull apart- thin material
    3. Shear
      1. blocks of rock slide pass one another - thin/thick material
    4. force applied across an area
4. Creates geological structures
  1. Joints
  2. Faults
    1. Strike-slip
      1. fault motion parallel fault strike
        Right lateral
        left lateral
    2. brittle structure
      1. result in shatter/crushed rocks
        Fault breccias
        fault zone: broken rock fragments
        Slickensides
        surface polished by fault motion
    3. Planar fractures offset by movement across the break. active/inactive. caused of earthquake
    4. Direction of fault: dominant type of crustal stress & type of fault
    5. orientation
      1. Hangingwal
        above block
      2. Foot wall
        below block
    6. dip-slip faults
      1. Reserse
        Thrust
        special type of reverse fault
        fault dip <35degree
        hanging wall move up
        help crustal compression
      2. Normal
        hanging wall move down
        help crustal extension (pull apart)
      3. depend on relative motion
  3. Folds
    1. Syncline
      1. Trough-like fold, limbs dip toward hinge
    2. Anticline
      1. arch-like fold, limb dip away from hinge
    3. ductile structure
    4. variety shape, size, geometry
    5. features
      1. Hinge
        portion of max. curvation on fold
      2. Limb
        less-curved sides of fold
      3. Axial plane
        imaginary surface defined by connect hinges of successive folds
    6. fault train
      1. series of anticline & syncline alternate
  4. 3D orientation is decribed by
    1. Strike
      1. horizontal intersection with a tilted surfacce
    2. Dip
      1. angle of surface down from horizontal
      2. perpendicular to strike
5. Tectonic foliation
  1. stress compression structure
  2. Flattening
    1. perpendicular to shorten strain
    2. sand grains flatten + elongate - clay re-orientate
  3. parallel fold axial plane
6. Uplift
  1. constructs mountain

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