Primary Sedimentary Structures

Roll # 02
Group Roll No. (1 to 8 )
BS-Geology 4th Semester
Aamir Asghar
Sabz Ali Khan & Malli Khan Institute Of
Earthsciences

PRIMARY FEATURES
OF
MARINE
SEDIMENTARY ROCKS

Contents:
1. Ripple mark:
2. Cross bedding:
3. Mud Crack:
4. Graded Budding:
5. Warm Tracks:
6. Leaf Prints:
7. Rip up:
8. Rain Prints:
9. Volcanic clast:
10. Sole Marks:
PRIMARY FEATURES
OF
MARINE
SEDIMENTARY STRUCTURES

Sedimentary Rocks
 Rocks formed by the deposition & cementation of material at
earth surface.
 Sedimentation is collective name of process that caused mineral
and organic particles to settle in place.

Sedimentary Structures
 The majority of structure form by physical process before,
during and after sedimentation.
 Sedimentary structure have variety of uses:
1. For interpreting the depositional environment in term of water
depth and wind strength.
2. For determining the the way of rock succession in area of
complex folding.
3. For determining the paleocurrent pattern and paleogeographic
.

Depositional Sedimentary structure
 When sediments erroded & transported in response to
unidirectional aquous flow such a flow of river,tidal,or stream
current.
 A wide range of sedimentary structure arises from water flowing
overall sedimentary surface.
 With tidal current the flood produce further sedimentary
structure.

 Ripple mark
 Ripple and dunes are Asymmetric bed form that gradually moved
down stream as sediment is transported to erosion of upstream faces
and its deposition on downstream faces.
 Ripple marks usually form in conditions with flowing water, in the
lower part of the Flow Regime.
 There are two types of ripple marks
1. Symmetrical ripple marks:
2. Asymmetrical ripple marks:

1.Symmetrical ripple marks:
 Often found on beaches, they are created by a two way current, for
example the waves on a beach (swash and backwash).
 This creates ripple marks with pointed crests and rounded troughs,
which aren't inclined more to a certain direction

2. Asymmetrical ripple marks:
 These are created by a one way current, for example in a river, or
the wind in a desert. This creates ripple marks with still pointed
crests and rounded troughs
 But which are inclined more strongly in the direction of the current.

formed on an ancient
beach
formed on modern
beach

 Cross Bedding
. Cross bedding include ripples and
dunes, or any cross stratification
caused by currents.
 The "cross" refers to the angle
between flat bedding and the
inclined bedding of the cross bed,
typically about 34 degrees.

 Paleocurrents are best found from cross
bedding

Mud Cracks
 Mud cracks are common in fine
grain sediments and form
through breakup of rocks due
to hydrolic pressure of water.
 They are commonly in tidal
flate species.
 As the water is lost the volume
is reduced and clay mineral pull
apart developing cracks in
surface under sub aerial
condition.

 a poly gonal pattern of cracks
develop when muddy sediments
dries completely .
 These are desiccation cracks the
spacing of desiccation cracks
depends upon the thickness of
layer of wet mud.
Mud Cracks

Mud Cracks – Environment that periodically dries
out

Gradded Bedding:
 This feature relate to the grain
size changes through a bed and
mostly develop in response to
changes in flow condition during
sedimentation.
 There are four types of gradded
bedding:
1. Contect gradding:
2.Reverse gradding:
3.Normal gradding:
4.Coarse tail grading:

1.Contect gradding:
 A gradual decrease in the
average grain size up
through the bed is called
contect gradding.
2.Reverse gradding:
 A pattern of increasing in
average size from base to top
is called reverse gradding.

3.Normal gradding:
 A grain size in a bed is
usually variable and may
show pattern of over all
decrease in grain size
from base to top.

4. Coarse tail gradding:
 A gradual upword decrease in
size of coarse grain.
 Multiple gradding where
there are several grade sub
unit in a bed occur.
 Reverse or inverse gradding
where grain size increase
upthrough the bed is not
common.

Warm Tracks:
 A fossil is remain of living
plants and animals that were
preserved in rocks and other
material .
 That organism lived for short
period of time in many areas
these are called warm tracks.
 Specific index fossil found in
different layer in different
rocks.
 They are used to describe fossil
fuel like oil,coal and petroleum.

Warm Tracks:
 Fossilization and preservation of organism can occured in
several way:
1) Preservation without change:
2) Complete replacement by mineral:
3) Formation of imprints:
4) Formation of thin film of carbon:
5) Filling of holospace by mineral:

 Leaf Prints:
 In fine grain sedimentary rocks
some prints of leaf are
preserved due to some
activities like earthquake.
 There preserved parts are
known as fossil.
 These preserved bodies are
used to identify the older and
younger rocks.

 Rip up:
 When over there was deposition of sand stone a particle of clay
is eroded and preserved in sand stone.
 Rip up are also known as shot rock that are used
to armor shore line.
 A foundation or wall of stone or concrete thrown
together without order as in deep water make
slope to erosion

 Sole Marks:
 Small scale erosion feature on the bed surface are referred as sole
marks.
 They are preserved in the rock record when an other layer of
sediments is deposit on the top leaving the feature on bedding
plane.
 Sole mark may be divided into those that form as a result of
turbulance in water causing erosion.

 Rain Prints:
 Rain print are commonly formed in mud rocks of continental
and shore line environment.
 Raindrop impressions form on exposed sediment by raindrop
impacts.

 Volcanic clast:
 Claustic sedimentary rocks are
rock composed of broken
pieces or claust of older
weathered and eroded rock.
 A claustic rock composed of
fragments and clast of
preexisting minerals and rock .
 A clast is fragment of broken
rock that are form by
weathering.

 Geological field work require to be properly organised even if
the visit is for a short duration.
 The extent of preparation and planning will depend on the
nature of the project.
 But there are certain basic things which must be attended to
for making it a success.
 Geological field work is a serious exercise and any casual
approach may affect its accuracy and therefore its usefulness.

Field study is designed to provide student with the opportunity
to examine social problems.
Evaluate the merit of ideas presented in the classroom.
Learn and practice method of naturalistic field research,data
collection,theory testing or program evaluation & social
intervention.
Develop interpersonal and professional skills & technical
competencies.

Participate in the ongoing activities of an organization.
Through field study upper division student and faculty engage
with our community to study issues,build capacity & impact social
change.

Primary Sedimentary Structures

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