of 56
7/29/2019 Folds and Faults
1/56
Folds and Faults
7/29/2019 Folds and Faults
2/56
Folds and Faults
Deformation of Rocks
7/29/2019 Folds and Faults
3/56
Deformation of rocks
Folds and faults are geologic
structures.
Structural geology is the study of thedeformation of rocks and the effects
of this movement.
7/29/2019 Folds and Faults
4/56
Small-scale Folds
7/29/2019 Folds and Faults
5/56
Small-scale Fault
7/29/2019 Folds and Faults
6/56
Orientation of deformed rocks
Strike: compass direction of a line
formed by the intersection of the inclined
plane and a horizontal plane. Dip: angle between the inclined plane
and a horizontal plane, measured
perpendicular to strike.
7/29/2019 Folds and Faults
7/56
7/29/2019 Folds and Faults
8/56
7/29/2019 Folds and Faults
9/56
Dipping Sedimentary Beds
7/29/2019 Folds and Faults
10/56
Cockscomb Ridge, S. Utah
7/29/2019 Folds and Faults
11/56
Cockscomb Ridge, S. Utah
7/29/2019 Folds and Faults
12/56
Stress
(force per unit area)
Types of directed stresses include:
Compression
Extension
Shear
7/29/2019 Folds and Faults
13/56
Compression
Action of coincident oppositely directed forces
acting towards each other
7/29/2019 Folds and Faults
14/56
Tension
Action of coincident oppositely directed forces
acting away from
7/29/2019 Folds and Faults
15/56
Shear
Action of coincident oppositely directed forces
acting parallel to each other across a surface
in a couple
7/29/2019 Folds and Faults
16/56
Strength
Ability of an object to resist deformation
Compressive or tensile
7/29/2019 Folds and Faults
17/56
Strain
Any change in original shape or size of an
object in response to stress acting on the
object
7/29/2019 Folds and Faults
18/56
Types of deformation
Elastic
Ductile (plastic)
Brittle (rupture)
7/29/2019 Folds and Faults
19/56
Elastic deformation
Temporary change in shape or size that is
recovered when the deforming force is
removed
7/29/2019 Folds and Faults
20/56
Ductile (plastic) deformation
Permanent change in
shape or size that is not
recovered when the
stress is removed
Occurs by the slippage
of atoms or small
groups of atoms pasteach other in the
deforming material,
without loss of cohesion
7/29/2019 Folds and Faults
21/56
Brittle deformation (rupture)
Loss of cohesion of a body
under the influence of
deforming stress
Usually occurs along sub-
planar surfaces that
separate zones of coherent
material
7/29/2019 Folds and Faults
22/56
Factors that affect deformation
Temperature
Pressure
Strain rate
Rock type
7/29/2019 Folds and Faults
23/56
Tectonic Forces and Resulting
Deformation
7/29/2019 Folds and Faults
24/56
Types of folds
(bent planar structures)
anticline: older rocks on the inside
syncline: older rocks on the outside
(scale - from mm to tens of km)
7/29/2019 Folds and Faults
25/56
7/29/2019 Folds and Faults
26/56
Fold terms
axial Plane: the plane of mirror
symmetry dividing the fold into two limbs
axis: line formed by the intersection of
the axial plane and a bedding plane
horizontal fold: where the fold axis is
horizontal
plunging fold: where the fold axis is not
horizontal
7/29/2019 Folds and Faults
27/56
Fold Terminology
7/29/2019 Folds and Faults
28/56
7/29/2019 Folds and Faults
29/56
Symmetrical, Asymmetrical
and Overturned Folds
7/29/2019 Folds and Faults
30/56
Anticline
7/29/2019 Folds and Faults
31/56
Asymmetric Folds
7/29/2019 Folds and Faults
32/56
Overturned Folds
7/29/2019 Folds and Faults
33/56
Overturned
Syncline,Israel
7/29/2019 Folds and Faults
34/56
Saudi Arabian Fold
7/29/2019 Folds and Faults
35/56
Map View of
Plunging
Folds
7/29/2019 Folds and Faults
36/56
7/29/2019 Folds and Faults
37/56
7/29/2019 Folds and Faults
38/56
7/29/2019 Folds and Faults
39/56
7/29/2019 Folds and Faults
40/56
7/29/2019 Folds and Faults
41/56
7/29/2019 Folds and Faults
42/56
7/29/2019 Folds and Faults
43/56
7/29/2019 Folds and Faults
44/56
7/29/2019 Folds and Faults
45/56
7/29/2019 Folds and Faults
46/56
7/29/2019 Folds and Faults
47/56
7/29/2019 Folds and Faults
48/56
7/29/2019 Folds and Faults
49/56
7/29/2019 Folds and Faults
50/56
7/29/2019 Folds and Faults
51/56
7/29/2019 Folds and Faults
52/56
7/29/2019 Folds and Faults
53/56
7/29/2019 Folds and Faults
54/56
7/29/2019 Folds and Faults
55/56
7/29/2019 Folds and Faults
56/56