Folds, Faults and Other Records of Rock DeformationCh.11 Grotzinger, Jordan Press & Siever

1. Folds, Faults and Other
Records of Rock
Deformation
Ch.11 Grotzinger, Jordan
Press & Siever

2. Concepts 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
• Anticlines and Synclines
• Dome, Valley and Ridge (TN) topography

3. A 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)

5. A 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.

8. Directed 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.

9. The directed stress can have three
orientations with respect to vertical:
(Side view)
(Side View)
(Bird’s Eye
View)

10. If the sediments are “soft” and folds
develop:
(Side view)
(Side View)
(Bird’s Eye
View)
H
I
G
H
S
L
O
W
S
H
I
G
H
S
L
O
W
S
L
O
W
S

14. If the sediments are brittle faults can
develop:
(Side view)
(Side View)
(Bird’s Eye
View)

15. If the sediments are brittle faults can
develop:
(Side view)
(Side View)
(Bird’s Eye
View)

17. What is the direction of directed
pressure?
How many orientations of faults can be
generated for the same directed pressure
direction??

19. What is your opinion?
1. True
2. False

20. If the sediments two possible orientations
for faults can develop:
(Side view)
(Side View)
(Bird’s Eye
View)

21. At 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

22. Brittle: 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)

24. Ductile-- 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

26. Joints 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)

28. Different types of faults imply different
directions of shortening and lengthening
and can be used to imply different types
of plate margin settings: