This document summarizes a presentation on the study of deformed rocks and geological folds. It defines key terms like anticline and syncline folds, describes different types of folds like symmetrical, asymmetrical, and recumbent folds. It explains how rocks deform under stress, the different types of strain (elastic, ductile, and brittle), and how geological structures relate to stress and strength. Methods for identifying folds in the field are also summarized, including directly observing folds and measuring the attitude of hinges and axial planes.

1. Institute of Geology
Presentation BY:
“Azhar Mahmood”

2. Topic:
Study of deform rocks, Folds
And Its Types

3. 1: What do deform rock look like ?
2:How do rock deform?
3:How do we know …. Why some rocks break
and other flows ?
4:How are resources related to geological
structures?
5:How do gelogical structure relate to
stress,strain and strenght?
•Why study of deform rocks??

4. • Describe the orientation of rock tilted or dipping bed .
• Describe folded rocks
• Limbs: The two dipping side of the folds is called limb.
• Hing line: Where the dipping limbs join.
• Plunging fold: When the hing line plungs downward into the
ground.
Anticline: Limbs dip away from hing line.
Syncline: Limbs dip in towards hing line.
What do deform rock look like ?

5. Particular rocks deform depend upon …
1:Its temperature amd depth
2:The amount ,rate and direction of the
stress
3:And the quantity of water in the rock
•How do roks deform?

6. • Some rocks are strong and other are not
• Some behave britly while other behave plastically
• With increasing deapth,temprature and confining pressure
decreases brittle fracture and increase plastic flow
• Fault and joints are thus expected near the surface,while plastic
flow should occur at deapth
• Some few weak material flow under less extreme conditions
such as rock salt and glassier ice
•How do we know …. Why some rocks break and
other flows ?

7. • Oil gas and ground water all move through pores and
all three have different densities that came them to
stratify.The lighter oil and gas will tend to migrate
upward and leak out to the surfaces,If no layer stop
them from doing so .
• Metal rich mineral resources commonly form along
joints and faults where warm fluid with hig
concentration of metal ions flow and cool to precipate
these metallic minerals
•How are resouces realted to geological
structures?

8. •How do geological structres relate to
stress,strain and strength?
Deformation by tension results in
the lengthening of the land scape
such as in the basin
And the deformation by
compression can fold or
fracturebut results in a shorting of
land scape

9. •Stress :
•The force that act on the rock
unit to change its shape and its
volume
•And stress causes strain and
deformation

10. •STRAIN
Change in shape or size of an object in
response to an applied stress.
= Deformation
Three Types of Strain
Elastic
Ductile (Plastic)
Brittle (Rupture)

11. •Elastic Deformation
a temporary change in shape or
size that is recovered when the
applied stress is removed.

12. •Ductile (Plastic) Deformation
• A permanent change in shape or
size that is not recovered when
the stress is removed.
• i.e. it flows or bends

13. •Brittle Deformation
(rupture)
• the loss of cohesion of a body
under the influence of deforming
stress.
• i.e. “it breaks”

14. •Objectives of deformation
• Observe and describe the deformation visible at earth
surface
• Understand the relationship between deformation and
the foces that drive it
• Learn the causes and effects of eath quakes
• Understand the relationship between earth resources
and the rock deformation

15. Types of Fold

16. Hormonic folding is where
the number and positions
of folds in successive
surfaces broadly match.
Harmonic Fold

17. Disharmonic Folds
Folding where the
number and positions of
folds is successive
surfaces does not broadly
match.

18. Anticline & Syncline
.The word anticline is from
Greek meaning “opposite or
inclined” ,the older rock are
in the center(core)and the
limbs dip away from each
other.
--------------------------
The word is from the Greek
meaning “together inclined”
,The younger rock are in the
center(core)the limbs dip
toward each other

21. Symmetrical Fold
A symmetrical fold
is one in which the axial
surface essentially vertical.
The term up write is also
used or symmetrical fold is
one that no limb is steeper
than the other.

23. Asymmetrical Fold
If one limb of
the fold is steeper
than the other it is
called asymmetrical
fold.

24. Monocline Fold
A simple fold with only dipping limb is
called a monocline

25. Recumbent Fold
A recumbent fold is one
in which the axial plane is
horizantal or axial plane is
sub horizantal.These
folds are present when
the deformation is intense
and one fold lie on the
top of next fold, so that
axial plane becomes sub
horizantal or horizantal

26. Isoclinal Fold
In isoclinal fold, from the
Greek meaning “Equally
inclined” refer to folds in
which the two limbs dip
at equal angle in the same
direction.

27. Box Fold
A box fold is one in
which the crust is broad
and flat; two hinges are
present , one either side
of the flat crust.

28. Shevron Fold
A shevron fold is one in which
the hinges are sharp and
angular.

29. Infered fold
Folds larger than an outcrop are based on inference. More over, the part of the fold
that was above the present surface of the earth has been removed by erosion.

30. Drag Fold
Drag folds form when a
competent(Strong) bed slides
passed and incompetent(weak)
bed.
such minner folds may
formed on the limbs of larger
folds because of the slipping of
beds passed each other, or they
may develop beneath over
thurst blocks,The axial planes
of the drag folds are not
perpendicular to the bedding
of the competent strata, but
are inclined at an angle.

31. Fan Fold
A fan fold is one , in
which both limbs are
overturned. In the
anticlinal fan fold , the
two limbs dip towards
each other; in the
synclinal fan fold the two
limbs dip away from each
other.

32. Field Identification

33. Direct observation of fold in
Field
The easiest and most satisfactory method is to observe folds, but this
can be done in comparatively few regions. Folds may be deduced
from other data, and are relatively minner features associated with
much larger folds.Where ever small folds are observed in single out
crop it is desirable to record their attitude.To do this one must
measure the attitude of hinges and attitude of the axial planes.The
pattern shown by minner folds in plane should also be recorded as it
is of great use, in conjunction with the plunge of fold s in deducing
larger structures.
In larger folds that can not be observed in a
single out crop or in series of closely adjacent outcrop, the attitude of
axial plane and the hinges can not be measured directly, nevertheless
the same principles apply and geologist should always think a fold 3
dimension.

35. Thank You