1. Introduction to Structural Geology.pdf

Structural Geology
GEOL. 408 (2+1 CH)
BS Geology (4th Semester)
Asad Muhammad
Department of Geology
University of Malakand

Course Contents
DESCRIPTIVE ANALYSIS
• Introduction - geologic mapping
• Components of a geological map
• Mapping procedures
KINEMATIC ANALYSIS
• Strain
• Computing changes in length of lines
• Computing changes in angle between lines
• Strain ellipse and ellipsoid
• Rotational and non-rotational strain
• Strain equations and Mohr’s circle strain diagram
2
DYNAMIC ANALYSIS
• Stress
• Stress vectors, normal stresses and shear stresses
• Stress ellipse and ellipsoid
• Stress equations and Mohr’s stress diagram
FOLDS
• Introduction
• Geometric analysis of folds
• Shape and size of folds
• Fold classification
FAULTS
• Introduction
• Types of Faults
• Determination of Fault displacement
• Faults in three dimensions

JOINTS
• Introduction
• Classification of joints and extension fractures
• Physical characteristics of joint surfaces Joint
related surfaces
CLEAVAGE, FOLIATION AND LINEATION
• Types of cleavage
• Foliation
• Lineation
3
LAB WORK
• Attitude of planes
• Attitude of lines
• Stereographic projections
• Graphic projections
• Interpretation of topographic maps
• Exercises on geologic maps
• Exercises on stereographic and orthographic projection
Course Contents…

Recommended Books
• Foundation of Structural Geology by Park, R.G., 1983, Blackie.
• Structural Geology of Rocks and Regions by Davis, G.H. & Reynolds, S.J., 1996, John Wiley & Sons, Inc. USA.
• Laboratory Exercise Book in Structural Geology by Ghauri, A.A.K.,1989, National Centre of Excellence in
Geology, University of Peshawar.
• An Introduction to Geological Structures and Maps by Bennisen, G.M., 1975, Edwrd Arnold.
• Structural Geology by Twiss, R.J. & Moores, E.M., 1995, W.H. Freeman & Co.
• Ramsay, J. G., Huber, M. I., 1987. The techniques of modern structural geology. Volume 2: Folds and
Fractures. Academic Press, London.
• Hobbs, B. E., Means, W. D., Williams, P. F., 1976. An outline of Structural Geology. John Wiley & Sons, New
York.
• Marshak, G., Mitra, G., 1988, Basic Methods of Structural Geology. Prentice Hall Englewood Cliffs, New
Jersey.
4

Grading System
5
ITEM
MAXIMUM MARKS FOR
COURSES WITH LABORATORY
(2+1 CH)
Mid Term Examination 15%
Internal Marks (Assignments, Quizzes, Presentations) 20%
Laboratory 15%
Final Term Examination 50%
TOTAL 100%

Introduction to Structural Geology
• The word structure is derived from the Latin word struere, which means ‘to
build’.
• Therefore a ‘Geologic Structure is the geometric configuration (arrangement) of
rocks,
and
• Structural Geology is the study of the geometry, distribution and formation of
structures.
6

• Study of the architecture and geometry of the Earth’s crust as it has resulted from
deformation.
OR
• Structural Geology is the study of deformation in rocks (change in structure) due to
internal/external forces. These forces are applied due to tectonic activities of
Earth.
7
Introduction to Structural Geology…

• It aims to determine the strength and mechanical properties of crustal
materials both at the time of deformation and now.
• How the rock bodies deform and the process of deformation.
• To understand Earth’s structures and the processes that create them.
• To learn skills used to analyze and interpret geological structures i.e. folds,
faults and joints etc.
8
Introduction to Structural Geology…

Why do we study Geologic structures?
• Because they provide part of the basis for recognizing and reconstructing the
changes that have marked the physical evolution of the Earth’s outermost
layers.
“The present is key to The past”
(James Hutton)
9
Introduction…

Fig (B): Calcite veins in the marble. The field of view
for this macrophotograph is 12 cm. cross-cutting
relationships. Hundreds of micro-veins. (G. H Davis)
10
• From the scale of the tectonic plates down
to the microscope.
• From Plate tectonics (Regional Structures)
to microtectonics (thin sections)
Introduction…

Structural Geology & Tectonics
• Tectonics and structural geology are very similar with regard to the practice, the scientific
methods followed and standard techniques of data collection and analyses.
• Tectonics is the study of the underlying processes that cause geologic structures to form.
• Tectonics: Study of the origin and geologic evolution (history of motion and deformation) of
large areas (regional to global) of the Earth’s lithosphere (e.g. origin of continents; building of
mountain belts; formation of ocean floor).
• Microtectonics describes microscale deformation and deformation structures visible under the
microscope.
• Structural geology typically deals with the observation, description and interpretation of
structures that can be mapped in the field.
11
Introduction…

Structural Geology – Tectonics and other Disciplines
Research in structural Geology also depends on other branches of geology
12
(3) Characteristics and geometries of structures at depth (3D):
– Geophysics
(1) Accurate interpretation of deformation and its tectonic significance:
– Petrology
– Geochemistry
– Rheology: P-T conditions of deformation and metamorphism
– Geochronology: ages of deformation and metamorphism
(2) Reconstructing pattern and ages of structural and tectonic events:
– Sedimentology
– Paleontology
– Stratigraphy
Introduction…

• Refers to the physical and chemical
changes that produce the structural
changes.
• General term that refers to all
changes in the original form and / or
size of a rock body.
• Deformation is determined by
comparing the rock’s deformed and
undeformed states.
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Deformation

15
Tilted strata
Horizontal strata
Deformation…

• The applied forces may be due to:
 Gravity (vertical force)
OR
 movement of the tectonic plates (horizontal forces).
• The effect of these forces on a rock depends on the area over which
they are applied:
• Force / area = Stress
• So, stress causes strain (if the intensity of stress is greater than the internal strenght of the rocks)
16
Deformation…

• Rocks may respond to stress in a brittle or ductile manner
depending on lithospheric conditions at the time of
deformation.
• During brittle deformation rocks fracture with strain
localized along a plane whilst the rocks to either side
remaining unaffected (e.g. faults and joints).
17
Deformation…

During ductile deformation, rock body changes the shape smoothly and strain is
pervasive throughout the rock body (e.g. folds).
18
Deformation…

Scope of
Structural
Geology
• Hydrocarbon exploration
• Geological structures control the
migration, trapping and escape of
hydrocarbons.
• Mineral exploration
• To identify new mineralized provinces,
structural geology is the first stage to
any regional geophysical and
geochemical surveys. 19

Scope of
Structural
Geology…
• Structural geology is a critical part of Engineering
Geology, which is concerned with the physical and
mechanical properties of natural rocks. Structural
fabrics and defects such as faults, folds, foliations and
joints are internal weaknesses of rocks which may
affect the stability of human engineered structures
such as dams, road and tunnels for various purpose.
• Natural hazard assessment, including earthquakes
can only be investigated by inspecting a combination
of structural geology and geomorphology.
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• Structural geology is central to any study of
past and present mountain belts and
sedimentary basins.
• Environmental Geologist and hydrogeologist
need to understand structural geology
because structures are sites of ground water
flow and penetration, which may affect, for
instance, seepage of toxic substances from
waste dumps, or seepage of salty water into
aquifers.
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Scope of
Structural
Geology…

What makes a
good structural
geologist?
• The ability to think in three dimensions. A
strong imagination is necessary.
• The ability to interact with a large range of
geoscientists over a wide range of geological
and environmental problems.
• The ability to link field studies to
computational modelling.
22

Structural Geology (GEOL. 408)
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Structural Analysis
•Descriptive Analysis
•Kinematic Analysis
•Dynamic analysis
Geological Structures
•Folds
•Faults
•Joints
•Cleavage, foliation
and Lineation

1. Introduction to Structural Geology.pdf

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1. Introduction to Structural Geology.pdf