Geological Structure - Physical Geology.ppt

VIETNAM OIL AND GAS GROUP
PETROVIETNAM UNIVERSITY
PHYSICAL GEOLOGY
Lecturer: PhD. Phạm Bảo Ngọc
E-mail: ngocpb@pvu.edu.vn
Chapter 7: GEOLOGIC STRUCTURE

Physical Geology
PhD. Phạm Bảo Ngọc 2
CONTENT

Physical Geology

Physical Geology
QUESTIONS
1. The difference between stress and strain .
Three types of stress and the resulting strain
2. The ways rock behaved with stress?
3. What is the difference between strike, direction of dip, and angle
of
dip?
4. Draw a sketch of an anticline and label the limbs, axial plane,
and
hinge line
5. The different types of folds
6. What is the difference between a joint and a fault?
7. The different types of faults
8. Why folds and faults are very important in Petroleum Exploration

Physical Geology
QUESTION 1
The difference between stress and strain.
 Stress – a force per unit area
 Strain is the change in shape or size (volume), or both, in response to
stress
 3 types: compressive, tensional and shear
Strain: shortening or flattening Strain: stretching or extension

Physical Geology
QUESTION 1
The difference between stress and strain.
 Stress – a force per unit area
 Strain is the change in shape or size (volume), or both, in response to
stress
Strain: shear

Physical Geology
QUESTION 2
 Ductile: uốn
 Elastic: đàn hồi
 Brittle: giòn
The ways rock behaved with stress
 Ductile and Elastic =>>> folds
 Brittle =>>> faults and joints

Physical Geology
QUESTION 3
What is the difference
between strike, direction of
dip, and angle of dip?
30°
Strike
Dip
(direction)
Angle of dip
N

Physical Geology
QUESTION 4
Draw a sketch of an anticline and label the limbs, axial plane, and
hinge line
An anticline is a fold
shaped like an arch with
the oldest rocks in the
center of the fold
Fold limb: the side of a fold.
Hinge line: line connecting the points of
maximum curvature on the fold profile.
Hinge zone: the zone of maximum
curvature on the fold profile.

Physical Geology
QUESTION 4
Draw a sketch of an anticline and label the limbs, axial plane, and
hinge line
 Figure also illustrates how
determining the relative
ages of the rock layers, or
beds, can tell us whether a
structure is an anticline or a
syncline
 the oldest exposed
rocks are along the hinge line
of the anticline.
 The youngest rocks were
originally in the upper layers,
were folded downward and are
now exposed along the
synclinal hinge line.

Physical Geology
QUESTION 5
The different types of folds
PLUNGING FOLDS: when the folds axis is dipping or plunging
DOMES & BASINS: Roughly circular pattern of outcrops
Other classification

Physical Geology
QUESTION 5
1) Plunging Fold
plunging anticlines and
synclines are distinguished
from one another in the
same way as are
nonplunging folds:
— by directions of dip or
by relative ages of beds.

Physical Geology
QUESTION 5
1) Plunging Fold
On a surface leveled by erosion, the
patterns of exposed strata (beds)
resemble Vs or horseshoes rather than
the parallel, striped patterns of layers in
nonplunging folds

Physical Geology
QUESTION 5
2) Structural Domes and Structural Basins
 A structural dome is a structure
in which the beds dip away
from a central point, and the
oldest rocks are found in the
center or core of the structure
 In cross section, a dome
resembles an anticline and is
sometimes called a doubly
plunging anticline
Dome near Casper, Wyoming.

Physical Geology
QUESTION 5
 In a structural basin , the beds
dip toward a central point,
and the youngest rocks are
exposed in the center of the
structure
 in cross section, it is comparable
to a syncline (doubly plunging
syncline)
 A structural basin is like a set of
nested bowls

Physical Geology
QUESTION 5
 Domes and basins tend to be features on a grand scale
(some are more than a hundred kilometers across), formed
by uplift somewhat greater (for domes) or less (for
basins)
 Domes and anticlines (as well as some other structures)
are important to the world’s petroleum resources

Physical Geology
QUESTION 6
What is the difference between a joint and a fault?
 If a rock is brittle ->> it will fracture ->> there is some
movement or displacement.
 If essentially no shear displacement occurs, a fracture or
crack in bedrock is called a joint .
 If the rock on either side of a fracture moves parallel to
the fracture plane, the fracture is a fault.
 Most rock at or near the surface is brittle, so nearly all
exposed bedrock is jointed to some extent

Physical Geology
QUESTION 6

Physical Geology
QUESTION 6
Fault in Big Horn Mountains, Wyoming, is marked by
a 2-meter wide zone of broken, red-stained rocks
that offset rock layers. Photo by Diane Carlson

Physical Geology
QUESTION 7
The different types of faults
Based on direction of slippage: dip-slip, strike-slip, or oblique-slip.
In a dip-slip fault , movement is parallel to the dip of the fault
surface. It consist of normal faults and reverse faults
A strike-slip fault indicates horizontal motion parallel to the
strike of the fault surface. It consist of right-lateral fault and left-
lateral fault
An oblique-slip fault has both strike-slip and dip-slip
components.

Physical Geology
QUESTION 7

Physical Geology
QUESTION 7
Normal faults:
Hanging wall
moves down
relative to foot
wall
Block slides
down the dip
angle

Physical Geology
QUESTION 7
Normal faults: Hanging wall moves down relative to foot wall
Block slides down the dip angle

Physical Geology
QUESTION 7
Reverse faults: Hanging wall moves up relative to foot wall

Physical Geology
QUESTION 7
A thrust fault is a reverse fault in which the dip of the
fault plane is at a low angle (<30o) or even horizontal

Physical Geology
QUESTION 7
Strike-slip faults: Displacement to sideways in a horizontal
direction
San Andreas Fault, California

Physical Geology
QUESTION 8
Why folds and faults are very important in
Petroleum Exploration and Exploitation?
Structural Traps

Geological Structure - Physical Geology.ppt

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