This document presents information about sedimentary basins. It discusses the formation of basins through mechanisms like isostatic changes and tectonic activity. It also classifies basins based on the type of plate boundary they form near, such as divergent or convergent boundaries. Additionally, it describes different types of basin margins including shelf-break, ramp, and growth-fault margins. Finally, it provides overviews of major sedimentary basins in Pakistan and how sequence stratigraphy analyzes changes in basins over time.

2. Presented to:
Dr. Kamran Mirza
Presented by:
M. Wajid Manzoor
Roll No: 09
Institute of Geology
Uuniversity of the Punjab Lahore

3. Contents
 Introduction
 Mechanism of basin formation
 Basin classification
 Basin margin
 Sedimentary basins in Pakistan
 Distribution of sedimentary basin types in the world
 Basin and sequence stratigraphy
 References

4. INTRODUCTION
 Sedimentary basins are regions of the earth of
long term subsidence creating accommodation
space for infilling by sediments
 It is also defined as, “ A low lying area/depression
where sediments can be deposit is called
sedimentary basin.”

5.  Basin is formed by crustal subsidence relative to surrounding areas
or some time surrounded area may be uplifted
 Basin have different shapes and sizes & formed by different
mechanisms

6. Mechanisms of Basin Formation
 Major mechanisms for regional subsidence/uplift:
o Isostatic – changes in crustal or lithospheric thickness
o Loading – by thrust sheets, volcanic piles,
o Dynamic effects – asthenospheric flow, mantle convection, plumes

7. Basin Classification
 Basin-generating tectonics is most important for the accumulation
of sediments. Such a basin classification must be in accordance with
the modern concept of global plate tectonics and hence will differ
from older classifications and terminology.
• Sedimentary basins associated with plate tectonic activity.

8. Types of plate boundaries
 There are three types of plate boundaries, characterized by the way the plates
move relative to each other.
o Divergent boundaries
• two plates slide apart from each other.
• Mid Oceanic ridges
o Convergent Boundaries
• two plates slide towards each other
• Subduction
• Orogenic Belt

9. o Transform Boundaries
• plates move parallel to each other
• Strike-slip systems

10. Basin margin concept
 The response of the depositional systems to this fall in relative sea
level depends on the nature of the basin margins.
o Shelf-break margins
o Ramp margins
o Rift margins
o Foreland basin margins
o Growth –fault margins

11. Shelf break margin
 Shelf break margin are those with
well developed depositional
cllinoforms
 Shelf break margin are typical of
passive continental margins at
times of slow rise of relative sea
level, when the deltaic system can
easily prograde to the shelf edge.

12. Ramp margin
 Ramp margins are characterized by
relatively shallow water depths, where
storms and current processes can
operate much of the area of deposition.
 Depositional angles are less than 1°.
 The response of depositional systems in
a ramp setting to the relative sea-level
change is therefore different from the
shelf-break margins.

13. Rift margins
 Rift margins characterize basins
undergoing active crustal extension.
 These margins are characterized by
high topographic relief.
 Subsidence rates generally increase
from the margins to the center of the
rift, although each individual fault
block will have its own pattern of
accommodation.

14. Foreland Basin Margins
 A foreland basin is a structural basin that develops adjacent and
parallel to a mountain belt.
 The rate of tectonic subsidence increases towards the foreland
thrust belt.
 Sediment accommodation may be relatively high in proximal area
compared with the basin center.

16. Growth fault margin
 Growth fault margins are characterized by
gravity driven syn-sedimentary extensional
faults.
 The rate of subsidence is considerably greater
on the hanging wall side of the growth fault,
resulting in an expanded sedimentary
succession.

17. Arc-related basins
 Forearc and backarc basins dominated by sediment derived from arc

18. Forearc Basin
 The area between the accretionary wedge and the magmatic arc, largely
caused by the negative buoyancy of the subducting plate pulling down
on the overlying continental crust
 tens of kilometers to over one hundred kilometers wide &up to
thousands of kilometers long; commonly arcuate.
 Nonmarine siliciclastic fluvial to deltaic deposits

20. Backarc or interarc Basin
 Backarc or interarc basins form by rifling and ocean spreading
either landward of an island arc, or between two island arcs which
originate from the splitting apart of an older arc system
 The evolution of these basins resembles that of normal ocean
basins between divergent plate motions.
 Their sedimentary fill frequently reflects magmatic activity in
the arc region.

21. Sedimentary basins in Pakistan
 There are two major basins in Pakistan
o Indus Basin
o Balochistan Basin
 There are some minor basins namely;
o Kirthar fold-belt basin
o Pishin fold-belt basin
o Sulaiman fold-belt basin
o Makran fold-belt basin
o Offshore Indus basin

23. Distribution of sedimentary basin types in the world

24. Basins and Sequence Stratigraphy
 Patterns, rates of subsidence and sediment supply can be strongly
influenced by tectonic processes that are responsible for forming
some basins
 Temporal and spatial changes in these factors can significantly
affect sequence development in those basins
 Towards shelf margin – rate of subsidence is always greater than
rate of eustatic fall
 No fall of relative sea level

25.  Further landward – rate of subsidence is less than rate of eustatic
fall
 Fall of relative sea level possible
 Area covered by each zone will change with time, basin to basin
 When a discrete shelf margin is present, shelf margin sediments
may be thick even in the absence of rapid thermal/tectonic
subsidence

26. References
 Basin Analysis By Philp A. Allen & Jhon A. Allen 2nd edition
 Internet ( Wikipedia )
 Sequence stratigraphy by D.Emery and K.J.Myers
 Sedimentology and stratigraphy by Sam Boggs 4th edition
 Sedimentology and Stratigraphy by Wiley-Blackwell.Gary Nichols
2nd edition