This is a presentation of Tectonic Framework of Bangladesh. Special thanks to Armaan,Zihad,Salman,wadud and sofol

1. WELCOME TO OUR
PRESENTATION

2. TOPIC:
Tectonic Framework of
Bangladesh

3. What is tectonic framework?
• Tectonics are the processes that control the structure and properties of the
Earth's crust and its evolution through time.These include the processes
of mountain building, the growth and behavior of the strong, old cores of
continents known as cratons and the ways in which the relatively
rigid plates that constitute the Earth's outer shell interact with each other.
Tectonics also provide a framework for understanding
the earthquake and volcanic framework that directly affect much of the
global population.

4. Tectonic framework of Bangladesh
• Tectonic framework refers to the basic structural frame on which
Bangladesh stands. It is essential to have a clear conception about the
tectonic framework of Bangladesh in order to evaluate the prospect of
mineral resources including oil and natural gas. Bangladesh occupies major
part of Bengal Basin which is bordered by Precambrian Indian Shield in the
west and north, Indo-burman range to the east and is open for considerable
distance into the Bay of Bengal to the south

5. Bangladesh is divided into two major tectonics
units:
1.Stable platform in the northwest
2.Deep(geosynclinal) basin to the southeast
3.A third unit, a narrow northeast-southwest trending zone called “Hinge Zone”
separate the above two units diagonally almost through
the middle of the country.The Hinge Zone is currently known as “Palaeo-Continental
Slope”.

6. 1.Stable platform in the northwest
• Stable Precambrian platform refers to the stable shelf of the bengal basin.This unit
occupies Rajshahi-Bogra-Ranpur-Dinajpur areas and is charactarized by limited to
moderate thickness of sedimentary rocks above a Precambrian igneous and
metamorphic basement.
On the basis of thickness of sediment cover,stable plateform is diveded into:
i.Ranpur Saddle(130m-1000m)
ii.Bogra shelf(1-6km)

7. i.Rangpur Saddle(referred to as Dinajpur shield):
• Rangpur Saddle in the north with thin to limited(130m to 1000m)
sedimentary cover above the precambrian basement.
ii.Bogra shelf(referred to as foreland shelf):
• B0gra shelf with mogerate(1 to 6km) sediment covers over the Precambrian
basement.Sedimentary layers in the Bogra shelf dips very gently towards
southeast until it reaches the hinge zone when the dips suddenly increase to
15 to 20 degrees and the sedimentary units plunge to great depths into the
deep geosynclinal basin to the south and southeast

9. 2.Deep(geosynclinal) basin to the southest
• This unit lies to the south and east of stable platform and is characterizing
by huge thickness(maximum of about 22 km near the basin center) of
sedimentary rocks mostly sandstone and shale of tertiary age.It occupies
greater Dhaka-Faridpur-Noakhali-Sylhet-Comilla-Chittagong and
Chittagong Hill tracts and the Bay of Bengal.The huge thickness of
sediments in the basin is a result of tectonic mobility or instability of the
areas causing rapid subsidence and sedimentation in relatively short span of
geologic time.

10. i.Fordeep
As the intensity of the folds decreases
towards the west ,the fold belt unit
merges with the foredeep unit which is
characteized by only mild or no folding
.So the sedimentary layers are generally
horizontal to sub horizontal and are free
from major tectonic deformation in the
foredeep area.This unit covers the central
part of the basin and is represented by
river to delta plain topography at the
surface.

11. i. Fold Belt:
The fold belt is characterized by folding
of the sedimentary layers into a series of
anticlines(upwards folds) and
synclined(downward fold).The anticlines
from the hills and the synclines from
valleys as seen in the topography of the
Chittagong-Comilla-Sylhet regions.The
intensity of the folding is greater
towards the east causing higher
topographic elevation in the eastern
Chittagong Hills tracks than the western
part.

12. 3.Hinge Zone
The hinge zone is a 25-km wide
northeast-southwest zone that
separates the Precambrian
platform in the northwest from
the geosynclinal basin to the
southeast.There is no surface
expression of this unit but it is
marked by the sudden increase
of dip in subsurface sedimentary
layers as shown strongly by the
seismic marker at the top of the
Sylhet Limestone unit of Eocene
age.This is why it is also known
as the Eocene hinge zone.

13. The hinge zone is not a tectonic hinge but represents Eocene shelf
edge/slope break i.e. a paleo-continental slope.The western part of
Bengal basin is marked by a series of migrating shelf breaks with
the most prominent being the Eocene shelf edge.This is also known
as Eocene hinge zone.