Title: Folds, Faults and Other Records of Rock Deformation Ch.11 Grotzinger, Jordan Press & Siever
1Folds, Faults and Other Records of Rock
DeformationCh.11 Grotzinger, Jordan Press
Siever
2Concepts you will need to know for the exams
- Deformation
- Normal fault
- Thrust/Reverse Fault
- Strike-slip Fault
- folds
- Stress
- tension ? ?
- compression ? ?
- shearing
- Factors athat determine the amount and type of
deformation in a rock - Temperature
- Fluids
- Pressure
- How fast materials are deformed
- Composition
- Time
- Fault breccia--- a example of brittle rock
deformation - Mylonite ----- an example of plastic deformation
- Joints fracturs and faults
3A fold is a bend in a rock But, how can this
be???? Inequality is the cause of all local
movements LEONARDO DA VINCI (1452-1519)
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5A fault is a break in a rock across which there
is observable movement. When the break
occurred an earthquake was generated, whether or
not anyone was there to detect it. Sometimes
faults die at depth and do not break the surface.
Sometimes they do such as for the Armenia 1988
earthquake.
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8Directed pressure (cf. confining) in the earth
leads to deformation if it is great
enough. Rocks deform under three orientations
for the directed pressure or STRESS.
9The directed stress can have three orientations
with respect to vertical
(Side view)
(Side View)
(Birds Eye View)
10If the sediments are soft and folds develop
(Side view)
(Side View)
HIGHS
HIGHS
LOWS
LOWS
LOWS
(Birds Eye View)
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14If the sediments are brittle faults can develop
(Side view)
(Side View)
(Birds Eye View)
15If the sediments are brittle faults can develop
(Side view)
(Side View)
(Birds Eye View)
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17What is the direction of directed pressure? How
many orientations of faults can be generated for
the same directed pressure direction??
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19If the sediments two possible orientations for
faults can develop
(Side view)
(Side View)
(Birds Eye View)
20At least 6 factors control how rock deforms e.g.
at shallow depth a rock may fracture whereas at
depth it may flow. Factors are (1) rock type (2)
Confining and directed pressure (3)
temperature (4) Fluids (5) Time (6) Rate of
deformation
21Brittle Means a rock breaks quickly into sharp
pieces, e.g. glass at room temperature Textures
show that rocks break in a brittle fashion at
shallow depths inside faults (I.e. fault breccia,
fault flour)
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23Ductile-- Means that a rock breaks slowly,or has
a lot of give Textures show that rocks break
in a ductile fashion at depths of a few
kilometers inside faults. The minerals
recrystallize, and grow into new shapes
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25Joints are also fractures, but which do not show
clear movement of blocks across them. (
Remember Faults are also fractures but WITH
movement across the fractures)
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27Different types of faults imply different
directions of shortening and lengthening and can
be used to imply different types of plate margin
settings
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