This presentation provides the brief details on the sedimentary structures present in the Permian and Eocene age rocks. Your suggestions needed. Thanks

1. Sedimentary
structures
Presented by
Hammad Ahmad Sheikh

2. • Sedimentary structures are large scale
features of the sedimentary rocks and
include the familiar cross bedding ripple
marks, bioturbation, bedding unit etc.

3. Depositional Structures
Lamination
• Lamination develops in fine grained
sediment when fine grained particles
settle, which can only happen in
quiet water.
Bedding
• Bedding is produced by changes in
the pattern of sedimentation i.e.
defined by changes in sediment
grain size, color and mineralogy.
Fig 1.1 showing lamination in the Dandot Formation
Fig 1.2 showing Massive bedding in the Tobra
Formaton

4. Depositional structures
Graded Bedding
Normal graded bedding developed
where the coarsest particle at the
base give way to finer particles
higher up.
Inverse graded Bedding
Reverse grading can arise from an
increasing strength of flow during
sedimentation but more commonly
from grain dispersion.
Fig 1.3 showing Normal Graded Bedding in the
Tobra formation.
Fig 1.4 showing Inverse graded Bedding in the
Tobra Formation.

5. Hummocky Cross
stratification
Hummocky Cross Stratification is
characterized by a gently
undulating low angle (<10-15)
cross lamination with the convex-
upward part the hummock and
concave-downward part the swale.
Fig 1.5 showing Hummocky Cross stratification
in the Dandot Formation.
Depositional Environment

6. Depositional structures
Trough Cross Bedding
Trough cross bedding is formed in
result of erosion and deposition
related to ripple and dune migration.
Ripple Cross Lamination
It is form in the result of migration of
asymmetrical Ripples in downcutting
direction.
Fig 1.6 showing Trough Cross Bedding in the
Dandot Formation.
Fig 1.7 showing Ripple Cross Lamination in the
Dandot Formation.

7. Depositional structures
Flaser bedding is formed where
mud deposition is intermittent
with ripple migration, thin streaks
of mud occur between sand.
Flaser bedding is the
characteristic feature of the inter-
tidal zone.
Flaser Bedding
Fig 1.8 showing Flaser Bedding in the
Dandot Formation.

8. Wavy Bedding
When there is an equal proportion
of sand and mud deposited then
wavy bedding is formed.
Wavy Bedding is the characteristic
feature of the mixed flat in the
inter-tidal zone.
Depositional structures
Fig 1.9 showing wavy bedding in the Dandot
Formation.

9. Lenticular Bedding
Lenticular bedding is the term
applied to isolated ripples of sand
within the mud as lenses.
Depositional structures
Fig 1.10 showing Lenticular bedding in the
Dandot Formation.

10. Depositional structures
Asymmetrical Ripple Marks
Current Ripples are produced by
unidirectional currents so they are
asymmetrical with a steep
leeside(downstream) and gentle stoss-
side(upstream).
Ripple Marks
Fig 1.11 showing Asymmeterical Ripple Marks in the
Dandot formation.

11. Depositional structures
Symmetrical Ripple Marks
Under natural conditions they form by
river and stream flow, by backwash on
beaches, and by longshore currents,
tidal currents, and deep-ocean bottom
currents.
Ripple Marks
Fig 1.12 showing symmetrical Ripple Marks in the
Dandot Formation.

12. Erosional structures
The presence of iron nodules mainly composed of hematite in claystone indicates that these
nodules were formed in poorly to moderately drained substrates, probably in fluvial floodplain
environments.
Clay nodules
Fig 1.13 showing clay nodules in the Erosional structures.

13. Channels
Channels are formed by
erosion, principally by
currents but in some cases
by mass movements.
Channels developed in many
environments like in fluvatile,
glacial , deltaic, tidal-flat,
shelf-margin and slope
marine fan locations.
Erosional Structures
Fig 1.14 showing Channels in the
Erosional structures.

14. Rain imprints
Rainspots are small
depressions with rims formed
through the impact of rain on
the soft exposed surface of
fine grained sediment.
Post-Depositional structures
Fig 1.15 showing Rain imprints in the
Dandot Formation.

15. Load Cast
Load structures are formed
through differential sinking of
one bed into another. Load
casts have been reported in
deposits from a variety of
environments, including fluvial,
lacustrine, deltaic, and
shallow-marine.
Post-Depositional structures
Fig 1.16 showing Load cast in the
Dandot Formation

16. Bioturbation is produced by a variety of organisms and because different organism engage in similar
types of behavior.
Biogenic structures
Bioturbation
Fig 1.17 showing Bioturbation in the Tobra
Formation.
Fig 1.18 showing bioturbation in the Dandot
Formation.

17. Biogenic structures
Bioturbation
Fig 1.19 & 1.20 showing Bioturbation in the Tobra Formation.

18. Trace Fossils
Tracks, trails, burrows,
borings, and other structures
made by organisms on
bedding surfaces or within
beds are known collectively
as trace fossils.
Biogenic structures
Fig 1.21 showing Trace Fossils in the
Dandot formation

19. Biogenic structures
• Petrified wood forms when plant
debris is buried by sediment and
then replaced by deposition of
mineral material dissolved in
groundwater.
Fig 1.22 showing Petrified Wood in the Dandot
Formation.
Petrified Wood

20. Biogenic structures
Petrified Wood
Fig 1.23 showing Petrified Wood in the Dandot Formation.