Sedimentology Exam 1

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Sedimentology Exam 1
2013-10-10 01:32:41
Sed Strat Exam Andy Cohen Geos 302

Sed structures, etc
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  1. Weathering (Def & types)
    Process which breaks down rock at the earth's surface 

    Produces discrete sed. particles and dissolved solutes



  2. Regolith
    Physically disintegrated rock debris
  3. Soils
    Complex material w/ physical, chemical, and biological products of disintegration from bedrock and plants
  4. Why study soils
    origins of sed. materials

    preservation of ancient soils (Paleosols) in rock record
  5. Forms of chemical weathering
    Simple solutions



  6. Major classes of sediments (4)


    Other biogenic (chert, coal)

    Other chemical (evaporites)
  7. Provenance
    Placeand geological setting of a sediment's origin
  8. Reynold's number ()
    Inertial Forces/Viscous Forces

    Laminar or turbulent

    High number: more turbulent
  9. Froude number ()
    Describes how surface waves will pass through a fluid

    Inertial Forces/Gravitational Forces
  10. Flow is shooting or supercritical

    Plane beds


    Chutes and pools (erosion)
  11. Flow is tranquil or subcritical

    Plane beds


    Sand waves

    Dunes (megaripples)
  12. laminar flow
  13. turbulent
  14. Competence
    Max. particle size a given flow can move
  15. Hydrodynamic Lift
  16. Ways to move particles (3)
    Traction (rolling and sliding)


    Suspension (viscosity)
  17. Bedforms
    Mounds or troughs of loose sed on a mobile bed that form at the sed/fluid interface, produced by the flow acting on them
  18. Density Flows
    Fluid moves b/c it is denser than surrounding fluid

    Causes: temp, salinity, composition (rivers entering lakes), turbidity (suspended sediment)
  19. Causes of Turbidity Flows
    Seasonal floods, storms, tsunamis, local earthquakes, landslides, oversteepened slopes
  20. Physical characteristics of Turbidity flows
    Low viscosity, turbulent flows, high  with no internal strength
  21. Turbidity Flow Head
    Turbulent and erosive

    Potentially very high velocities and runouts
  22. Turbidity Flow Body
    Carries traction load at base

    Transmits gravitational shear waves "upstream" 
  23. Turbidity Flow Tail
    Lower velocity and suspended sediment concentration

    Passage often much delayed (days to months)
  24. Bouma Sequence (6, bottom to top)
    Erosional surface

    Graded gravel and sand

    Planar bedded sands

    Ripple bedded sands/silts

    Planar bedded sands and silts

    Mud drape from tail suspension
  25. Angle of repose
    Angle at which materials naturally pile (27-34 degrees for sand)
  26. Sed Fabric
    Internal organization of sed particles
  27. Porosity
    % pore space
  28. Permeability
    Ease with which a fluid is transmitted through a rock
  29. Imbrication
    Conglomerate pebbles dip away from direction of current
  30. Graded Bedding
    Sed particles are finer at the top than at the base

    Indicates declining flow
  31. Sed Structures associated with bedform migration
    Planar and Trough cross bedding
  32. Sed Structures associated with episodic flow
    Flaser bedding

    Lenticular bedding 

    (ex. Lake deposits)
  33. Sturctures associated with unidirectional flow on slopes
    Tool marks

    Flute casts
  34. Bedforms associated with bidirectional flow
    Oscillatory ripples

    Herringbone cross strat
  35. Structures formed by fluid escape
    Flame structures

    Sedimentary dikes

    Dish structures
  36. Structures formed during desiccation

    Raindrop imprints

    Salt casts
  37. Biogenic Structures
    Trace Fossils

    Burrows, trails, borings, footprints, etc


  38. Unroofing in Alluvial Deposits
    Progressive uplift of footwall

    Puts older sediments on top of younger ones
  39. Sinuosity index
    S= (Deepest part of channel)/(Length of Valley)
  40. Anastamosed River
    Multiple stable channels

    Prominent levees, extensive wetlands, vegetated islands
  41. Channel Migration causes...
    Epsilon cross bedding

    Lateral Accretion Surfaces
  42. Crevasse Splay Deposits
    Broken levees

    Rapid loss of flow competence - Climbing ripples
  43. Lake drainage types
    External: has outlet

    Internal: no outlet
  44. Walther's Law
    Sediments usually deposited next to each other may be vertical to eachother when depositional environment changes