LECTURE 12

LECTURE 12

1. DEFORMATION OF ROCKS

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