Geology 3120 Rock Fabric

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Geology 3120 - Rock Fabric
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Objectives

• Attitudes of Fabric
• Cleavage
• Lineations
• Foliations

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Fabrics
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Fabrics
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Fabrics
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Fabrics
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Cleavage

• General definition - closely-spaced, aligned,
  planar to curviplanar penetrative surfaces
• Continuous verses disjunctive cleavage - planar
  verses non-planar
• Mechanical realignment and growth of clay
  minerals
• Pressure dissolution process

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Slaty Cleavage

• Mechanical alignment and growth of clay minerals

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Slaty Cleavage

• Where is the bedding?

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Slaty Cleavage

• Where is the cleavage?

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Slaty Cleavage

• What direction is the nearest anticline?

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Pressure Dissolution Cleavage

• Extensional veins shortened in silt

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Axial Planar Cleavage

• Identify the folds

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Axial Planar Cleavage

• Identify the cleavage

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Axial Planar Cleavage

• Identify the axial surfaces

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Axial Planar Cleavage
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Axial Planar Cleavage
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Bedding Axial Planar Cleavage Axial Surfaces
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Cleavage Vergence
Central
East
West
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Cleavage Vergence
West
Central
East
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Cleavage Vergence
Central
West
East
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Cleavage Vergence
Central
East
West
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Pressure Solution Cleavage - Limestone

• Insoluble material is typically contained in the
  stylolite

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Introduction to Lineations

• One-Dimensional Features
• Slickenline lineations
• Fault grooves
• Stretched conglomerates
• Boudins

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Slickenline Lineations

• Calcite mineral growth
• on a fault plane

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Grooves

• Grooves are parallel to strike
• What type of fault is this?

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Stretched Conglomerates
Rock has a foliation, lineation depends on
whether clasts are disc- or rod-shaped
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Boudins
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Introduction to Foliations

• Bring in the next dimension
• Deformation or organization of grains with
  respect to a two-dimensional surface
• Foliations in addition to lineations may yield
  information about the stretching direction

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Foliations with Lineations
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References
Slides 3 - 6 http//earth.leeds.ac.uk/minor/duc
tile/describing/lin-plane.htm Slide 1, 8 - 11
http//earth.leeds.ac.uk/minor/cleavage/slatey.htm
Slide 12 http//earth.leeds.ac.uk/minor/dmt/pso
lncleav.htm Slides 13 - 16 http//earth.leeds.ac
.uk/folds/describing/cleavage/cleavage.htm Slide
17 - 20 http//earth.leeds.ac.uk/folds/describin
g/cleavage/cleaverge.htm Slide 21
http//earth.leeds.ac.uk/minor/dmt/stilolite.htm S
lide 23 http//earth.leeds.ac.uk/minor/faults/str
ifibres.htm Slide 24 http//earth.leeds.ac.uk/min
or/faults/grooves.htm Slide 25
http//earth.leeds.ac.uk/minor/ductile/vasgo/congs
.htm Slide 26 http//earth.leeds.ac.uk/minor/ext
end/boudyke.htm Slide 26 http//earth.leeds.ac.u
k/strain/gallery/boudin.html Slide 28
http//earth.leeds.ac.uk/minor/ductile/vasgo/mylli
n.htm Slide 29 http//earth.leeds.ac.uk/minor/duc
tile/gallery/plattgen.htm