structure

1. Presentation On
Structural Geology
On Bandarban Hill Range

2. Group member
 Jannatul Mawa (308)
 Shafali Akter Shorna(321)
 Mhamud Reza Mahi(328)
 Al Mamun(333)
 Md.Arafat Hosen (342)
 Ahmed Al Hasan (2350)

3. Introduction
The earth crust contains structures almost
everywhere, and the aims of structural
geology are to understand these structures.
The general disposition, attitude,
arrangement or relative position of the rock
masses of a region or area is called structure
(Bates & Jackson, 1987). Structural geology
is the study of the architecture of rocks
insofar as it is resulted from deformation
(Billings, 1999). Structural geology is about
folds, faults and other deformation structures
in the lithosphere, how they appear and how
and why they formed.
Figure:Geological structure

4. Structural Analysis
Major structures of the investigated area are :
 Anticlinal Plunging fold
 Fault.
Minor structures that were found during investigation are:
 Local Unconformity .
 Fracture.
 Joints.
 Drag Fold

5. Anticlinal Plunging Structure
Plunging fold: The fold axis is not horizontal
Criteria of recognition of Bandarban Anticline in
the field:
• Direct visual observation of this region indicates
that the structure is a large scale fold, which is
convex upward.
• The attitudes of rock strata show that the beds are
dipping in the opposite direction from a place that
represents an imaginary line of the structure.
• The oldest rock is observed at the centre, which is
Bluish Gray shale (UNIT C3) and younger rock is
at the outer side, which Variegated Color
Sandstone (UNIT A). The dip directions are
measured during field investigation.
• The imaginary line along the lowest dip amount is
the axis of the structure.
Figure:Bandarban Anticline
Legend

6. Fault
Faults are fractures, along which the
movement of one block, with respect to other
block, has taken place(Ragan, D. M., 1985).
Criteria of recognition of fault in the field
• Repetition of strata or lithologic irregularities.
• Discontinuity of structures
• Sudden changes in sedimentary facies
• An abrupt change in dip amount of the
anticline.
• Presence of the minor fault
During our field observation we find some
types of fault. These are
 Strike slip fault
 Thurst fault
lii
Figure :Fault Scarpment observed in
the downstream of the Sangu River
section

7. Strike slip fault
Strike slip fault: A fault, in
which the fault trace or fault
plane is absolutely parallel
to the strike of the adjacent
rocks, is known as a strike
fault.
Figure:Strike slip fault

8. Thurst fault
Thrust fault: A fault, which has
a very small angle of hade
(inclination of the fault plane
with the vertical is very small)
and the hanging wall has
apparently gone up with
respect to foot wall is called a
thrust fault.
Figure:Thrust fault

9. Joints
Joints are cracks or fracture present in
the rocks along which there has been
no displacement. Joints occur in all
types of rocks. They may be vertical,
inclines or even horizontal. Their dip
and strike are measured in the same
way as that of sedimentary strata. They
are also formed when the rocks are
subjected to compression or tension
during earth movements
At our field observation we observe joint
at Bandarban Road Cut Section
jj
Figure:Joint observed at Bandarban
Road Cut Section

10. Local Unconformity
Unconformity:An unconformity is a
buried erosional or non-depositional
surface separating two rock masses or
strata of different ages, indicating that
sediment deposition was not continuous.
In general, the older layer was exposed
to erosion for an interval of time before
deposition of the younger, but the term is
used to describe any break in the
sedimentary geologic record.
Figure:Conglomerate bed observed at
the downstream of the Sangu River
Section

11. Drag Fold
Drag fold: As minor folds developed
within the body of weaker rocks
surrounded on both the sides by
layers of stronger rocks.
Figure: Drag fold:
Figure:Drag fold

12. Fracture
A fracture is any separation in a geologic formation, such as a
joint or a fault that divides the rock into two or more pieces. A
fracture will sometimes form a deep fissure or crevice in the
rock. Fractures are commonly caused by stress exceeding the
rock strength, causing the rock to lose cohesion along its
weakest plane.Fractures can provide permeability for fluid
movement, such as water or hydrocarbons. Highly fractured
rocks can make good aquifers or hydrocarbon reservoirs, since
they may possess both significant permeability and fracture
porosity

13. Conclusion
The Field work was operated working from the West flank of the anticline towards
the East flank. Individual locations were plotted on the Anticline separately. A
plunging anticline has a hinge that is not parallel to the earth's surface.

14. References
 Bates, R.L. and Jackson, J.A. (1987) Glossary of Geology. 3rd
Edition, American Geological Institute, Alexandria, 788 p.
 Billings,M.P.,1999,Structural Geology;Prentice Hall of India
Private Ltd,New Delhi,2,140,278.
 Ragan, D.M. (1985) Structural Geology, an Introduction to
Geometrical Techniques. 3rd Edition, John Wiley & Sons, Inc.,
Hoboken, 210-215.

15. Thank You