The preparation of a geological field report of any place is a valuable contribution of a number of people who are to be acknowledged. I am grateful to Almighty God for the excellent opportunity to visit Kuakata & its surrounding area, arranged by the Department of Geology & Mining, University of Barisal and for finishing the visit successfully. It deals with the physiography, sedimentology geomorphology and its interpretation, correlation with standard geologic succession, environment and economic geology of Latachapli, Lakkhirhat, Nijampur, NishanBaria, Khapra Bhanga, Lebur Ban, Kuakata Sea Beach Kalapara Upazila, Patuakhali District Barisal, Bangladesh along with the interpretation of paleo-environment of depositional history.

1. 1
GEOLOGICAL FIELD REPORT
On
Latachapli, Lakkhirhat, Nijampur, NishanBaria,
Khapra Bhanga, Lebur Ban, Kuakata Sea Beach
Kalapara Upazila, Patuakhali District
Barisal, Bangladesh
___________________________________________________________
REPORT SUBMITTED IN REQUIREMENT OF PARTIAL
FULFILLMENT OF 1st
YEAR BSc. HONOURS IN GEOLOGY &
MINING
GMF 112: GEOLOGICAL FIELD MAPPING
_____________________________________________________________

2. 2
ACKNOWLEDGEMENTS
The preparation of a geological field report of any place is a valuable contribution
of a number of people who are to be acknowledged. I am grateful to Almighty God for
the excellent opportunity to visit Kuakata & its surrounding area, arranged by the
Department of Geology & Mining, University of Barisal and for finishing the visit
successfully.
My sincere appreciation goes to our Chairman Sir Dr. Dhiman Kumer Roy,
Assistant Professor of Department of Geology & Mining, University of Barisal, for his
constant guidance and heart full co-operation during the field work and his inspiration,
advice and help to understand many technical problems during field work. He explained
all the topics so easily that we do not have any problem to realize.
I thank my respected teacher Muhammad Risalat Rafiq of Geology & Mining
Department, University of Barisal, for his perceptive guidance, vigorous assistance and
thoughtful contribution during the field work & Special thanks to Lina mam her time &
consideration.
We badly missed our respected teacher Abu Jafor Mia , of Geology & Mining
Department, University of Barisal. His presence in this trip will help us more.
I would like to thank the volunteers of the food committee, transport committee
and medicine committee for their excellent performance. I owe a lot to my friends,
specially my group members, who have given me a great deal of support and helped
during field work. We have built an amazing company in this whole trip

3. 3
Tableof Contents
Page
Chapter 01 : INTRODUCTION
Chapter 02 : FIELD EQUIPMENT & SAFETY
2.1 : Field notebook
2.2 : Pencils, eraser, pencil sharpener
2.3 : A few colored pencils
2.4 : GPS Meter
2.5 : Tape measure ,surveyor’s tape or folding ruler
2.6 : Grain Size and Color Indicator etc.
2.7 : Bag pack
2.8 : Hammer
2.9 : Base Map
2.10 : First aid kit
2.11 : Emergency food supplies
2.12 : Suitable clothing and footwear
2.13 : Mobile phone & Laptop
Chapter 03 : INTRODUCTION TO FIELD OBSERVATIONS AT
DIFFERENT SCALES
3.1 : Introduction: What, where and how?
3.1.1 : Defining the fieldwork objectives
3.1.2 : Deciding where to do the fieldwork
3.1.3 : Location, Extent and Accessibility

4. 4
3.2 : Scale of observation, where to start and basic measurements
3.2.1 : Regional context
3.2.2 : Whole exposure
3.2.3 : Hand specimens
3.3 : Overview of possible data formats
Chapter 04: THE FIELD NOTEBOOK
4.1 : Introduction: The purpose of field notes
4.2 : Field notebook layout
4.2.1 : Preliminary pages
4.2.2 : Daily entries
4.3 : Field sketches: A picture is worth a thousand words
4.3.1 : Sketches of exposures
4.4 : Written notes: Recording data, ideas and interpretation
4.4.1 : Notes recording data and observations
4.4.2 : Notes recording interpretation, discussion and idea
Chapter 05: RECORDING LIVING ORGANISM’S
INFORMATION’S
5.1 Introduction
5.2 collecting living organisms data

5. 5
5.3 sampling strategies
5.4 Real life Examples
Chapter 06 : RECORDING FEATURES OF SEDIMENTARY
6.1 Introduction
6.2 Description, recognition and recording of sedimentary deposits
and sedimentary structures
6.2.1 Recording sedimentary lithology
6.2.2 Recording sedimentary structures
6.3 Graphic log
6.4 Rocks in space: Reconstructing sedimentary environments and their
diagnostic features
6.4.1 Meandering river depositional environment
List of Figures
Figure 2.6 : Comparing grain by using Grain Scale
Figure 3.1 : Regional Map of Field Work Area
Figure 3.1.2 : Location map of Fieldwork Area
Figure 3.2.2 : Measuring the length of different sedimentary bed
Figure 3.2.3(a) : Loose sediment including red color sediments indicates Iron
Figure 3.2.3(b) : Ripple marks in Kuakata sea beach
Figure 3.3(a) : Sketches of visiting area
Figure 3.3(b) : Graphic log of stratigraphic succession
Figure 4.2.2 : Daily Entries
Figure 4.3.1 : Geologic exposures
ROCKS AND CONSTRUCTING GRAPHIC LOGS

6. 6
Figure 4.4.1 : Observation & Record data
Figure 4.4.2 : Group discussion
Figure 5.4(a) : Shell of Turritella (Genus)
Figure 5.4(b) : Shell of Conus (Genus)
Figure 5.4(c) : Shell of Apple Snail
Figure 5.4(d) : Soft Sheel Clam
Figure 5.4(c) : Burrows and burrowing animal
Figure 6.2.2(a) : River morphology
Figure 6.2.2(b) : Sediments deposited on the river channel & bar
Figure 6.2.2(c) : Sedimentary bedding
Figure 6.2.2(d) : Example of cross-section of bedding
Figure 6.2.2(e) : Coastal morphology
Figure 6.2.2(f) : Tidal creek
Figure 6.2.2(g) : Mud crack
Figure 6.2.2(h) : River terrace
Figure 6.2.2(i) : Standing on the natural levee
Figure 6.2.2(j) : Small island
Figure 6.2.2(k) : A local man giving information about the newly formed small island
Figure 6.3 : Graphic log and bedding section
Figure 6.4.1 : Meandering depositional environment
Figure* : Working in the Field with Group
List of the Table
Table 3.1.2 : Stations of the investigate areas
Table 6.1 : Some sedimentary rock types which we found in field and the
Sedimentary structures and features that they are commonly associated
with.
Table 6.2 : Some of the common depositional sedimentary structures, bed forms
and their process of formation.
Table 6.3 : Summary of some of the processes/features and the sedimentary

7. 7
environments
Chapter 01: Introduction
The main aim of field geology is to observe and collect data from rocks and/or
unconsolidated deposits, which will further our understanding of the physical, chemical
and biological processes that have occurred over geological time. Many of the basic
observational principles used in field geology have not changed for hundreds of years,
although the interpretation of the data, the scale of resolution and some of the equipment
has advanced greatly. Fieldwork involves making careful observations and measurements
in the field and the collection and precise recording of the position of samples for
laboratory analysis. The very act of collecting field data often raises questions about
processes on Earth, which had perhaps not previously been envisaged. Furthermore,
during fieldwork it is usual to initiate, or to build on, constructing and testing different
hypotheses and interpretations based on the observations; this iterative process will help
to determine the essential data and samples to collect.
Fieldworkwasdoneforthefollowingwork:
1. Deciding what data to collect in order to address the scientific question(s).
2. Finding the most suitable exposures from which to collect the data.
3. Making a good record of the data collected; preferably a record that can be understood
by others and can be used years after the data were collected.
4. Understanding and interpreting the basic observations that are made.
Chapter 02 : FIELD EQUIPMENT & SAFETY
The investigations were carried out in the field by adopting the usual ‘Traverse method’
that is walking on foot through the road cut and stream cut sections with the common
instruments used by a investigator in the field such as:

8. 8
2.1 Field notebook : Field notebook is very essential to complete a fieldwork
successfully . many important information which are collected from our investigation can
be written on the notebook. A notebook is very effective to the geologists and it maybe
be pocket sized but can be very informative tool.
2.2 Pencils, Eraser, Pencil Sharpener : Those are very important tools to
sketching during fieldwork. Sketching is must for a complete and perfect fieldwork
report.
2.3 A Few Colored Pencils : Colored pencils are important to draw a location and
also used as a indicator
2.4 GPS Meter : Global positioning systems (GPS) use ultra high-frequency radio
wave signals from satellites to trigonometrically derive our position to within a few
meters laterally. A wide range of GPS systems are available on the market and the reader
should refer to specialist reviews and literature for more information. Increasingly,
mobile phones contain a GPS unit. Global positioning systems units do not work in deep
ravines and on some coastal sections; they are also not particularly accurate for altitude.
The GPS can be set up for the particular grid system that we are working with or for a
global reference that is based on latitude and longitude.
2.5 Tape measure , Surveyor’s tape or folding ruler : Folding ruler or
surveyor’s tape is a measuring instruments similar in function to rulers are made portable
by folding or retracting into a coil when not in use .when extended for use they are
straight like a ruler. The folding ruler used in geometry, technical drawing and also used
in measurement at sedimentary strata.
2.6 Grain Size and Color Indicator etc. : Various well - established comparison
charts can be used to provide a semi – quantitative description of the rock and any

9. 9
changes in it. These include grain - size charts and rock classification diagrams. The
figures commonly used are included in the appendices at the end of this book but charts
such as those for grain size and texture can also be purchased for use in the field. The
grain size chart should be used by placing the edge of the card on top of a clean fresh
surface of rock and comparing the grain size on the chart to that of the rock until a match
is found for the average grain size and if appropriate the maximum and minimum size. If
the grain size is small it might also be necessary to use a hand lens on the card and rock.
If the rock is poorly consolidated, scatter a few representative grains across the grain -
size images to determine the average size .Weak hydrochloric acid can be used to test for
carbonate. Afresh surface of the rock free from any coating minerals and weathered
coating must be obtained before dropping acid on the rock. The acid will fizz strongly
with fresh calcium carbonate but much less strongly for dolomite (calcium magnesium
carbonate). Freshly powdered dolomite will fizz more readily. Health and safety
precautions for the handling of acid should be followed. In sedimentary rocks an easier
and less destructive method of determining whether there is carbonate is to test the
hardness of the rock. The most common colorless minerals in sedimentary rocks are
quartz and calcite (with feldspar less frequently). Quartz will scratch steel For particular
situations it may be necessary to improvise a scale: e.g. mark a thin, straight piece of
wood in black and white stripes or for
measuring inaccessible cliffs ,paint a length of rope and then take photographs while the
rope is hanging over the cliff .whereas calcite will not. Feldspars have distinct cleavage
and tend to go white and powdery as they weather.

10. 10
Figure : Comparing grain by using Grain Scale
2.7 Bag pack : Backpack is very essential during fieldwork. We carried out our
cloths ,food ,necessary field equipment such as laptop ,paper, clip board ,food ,medicine
by backpack.
2.8 Hammer : A geological hammer is necessary for most geological fieldwork, both
for the collection of samples and, where necessary, to create fresh surfaces so that the
rock and the minerals within it can be described.
2.9 Base Map : Before starting any mapping project it is important to be clear about
the aims of the investigation, for this decision will guide the choice of map scale and
control the nature of the techniques which are needed to cover the area in the detail
necessary to resolve the problem.
2.10 First Aid Kit : In a geological fieldwork an investigator must have a back
packer sized first aid kit with at least the basic gear
2.11 : Emergency Food Supplies : Healthy food and fresh water much needed
during the field work period for our proper nutrition.
2.12 Suitable Clothing & Footwear :
Jacket: It will get cool to cold at night in the mountains and the mornings will
usually be cool also. A fleece jacket will probably do just fine.

11. 11
Long sleeve shirts: Long sleeve t-shirts or flannels or synthetics are good for
layering.
Field hat: This is required for protection from the sun. A lightweight, light
colored hat with a wide brim that shades our neck, ears, and face is best.
Goggles: These are good to protect our eyes on bright days and to make our look
cool in the field.
Footwear: Suitable footwear is very important in a geological fieldwork.
2.13 : Mobile phone & Laptop : Mobile phone & Small computer laptops,
electronic notebooks and Personal Digital Assistants (PDAs) can be used in the fi eld to
record field data.
Chapter 03 : INTRODUCTION TO FIELD
OBSERVATIONS AT DIFFERENT SCALES
3.1 : Introduction: What, where and how?
Going out into the field and examining rocks at an exposure for the first time, or even
subsequently, might well reveal features that we cannot recognize, do not understand or
cannot explain. Overcoming this challenge is a matter of careful study, persistence and
experience. This chapter provides an introduction to some of the key questions for
geological fieldwork and a systematic way of overcoming the challenge of collecting data
and understanding an exposure. The key questions are:
1. What are the objectives of the fieldwork?
2. Where is the best place to gather the data?
3. How do I precisely determine my position?
4. Faced with a new exposure, where do I start?
5. What is the most appropriate way of collecting the data?

12. 12
Figure: Regional Map of Field Work Area
3.1.1 : Defining the fieldwork objectives
Fieldwork is undertaken to address particular scientific problems; these should be clearly
defined before going into the field. This is because it is very easy, when out in the field
and faced by excellent geological exposures, to become distracted by other interesting
features or to spend too long on particular aspects. Before go into the field, decide on the
overall objectives of the fieldwork and at frequent intervals during the fieldwork remind
ourself of these. On a day - to day basis in the field, break the work down into achievable
tasks; these may need to be reviewed and amended if the weather or time available
changes. Another important point to remember is not to over interpret the rocks based on
a single observation. The common overall objectives of fieldwork are summarized below:
1. Gain a general insight into the geology of an area
2. Construct the geological history of an area

13. 13
3. Produce a geological map
4. Determine the sedimentary depositional environment
5. Make a record of a period of climate change
6. Determine the sea - level history over a period of geological time
7. Biostratigraphy
8. Record the deformation history of an area
3.1.2 Deciding where to do the fieldwork
To address all other fieldwork objectives, the following points are worth considering
when choosing the exposures to concentrate on:
1. whether or not they are representative;
2. stratigraphic completeness;
3. how weathered the rocks are;
4. whether they are suitable for sampling without the need to
5. clean the exposures;
6. accessibility;
7. safety.
3.1.2 Location, Extent and Accessibility
Geological data are spatial therefore it is very important to be able to record the position
of geological features accurately. The first part of this is locating the position of the
exposure. By using GPS check that it is correctly adjusted for the country that we are
visiting or an appropriate grid system . Our position might also be immediately obvious
from a topographical map. There are instances, however, when it is not possible to use
either of these methods or when a more accurate position is required. In this case
compass is appropriate for triangulation.
Our studied area is located in south-eastern Bangladesh and in between latitude 210
48/
N
to 210
53/
N and longitude 900
5/
E to 900
12/
E. The area belongs to the Kalapara

14. 14
Upazila, Patuakhali District. It is about 320 kilometers (200 mi) south of Dhaka, the
capital, and about 70 kilometers (43 mi) from the district headquarters.
Kuakata is a town known for its panoramic sea beach. Kuakata beach is a sandy expanse
18 kilometers (11 mi) long and 3 kilometers (1.9 mi) wide. From the beach one can have
an unobstructed view of both sunrise and sunset over the Bay of Bengal.
Figure: Location map of Fieldwork Area
Table 3.1.2 : Stations of the investigate areas
Station No. Latitude Longitude Name of the Place
1 21°51ʹ31.122˝ N 90°10ʹ28.188˝ E Latachapli
2 21°50ʹ57.39˝ N 90°10ʹ49.46˝ E Lakkirhat
3 21°48ʹ15.16˝ N 90°12ʹ35.57˝ E Kauar Chor
4 21°53ʹ40.28˝ N 90°07ʹ0.75˝ E Nishan Baria
5 21°53ʹ54.61˝ N 90°07ʹ3.716˝ E Nilgonj
6 21°53ʹ52.46˝ N 90°07ʹ13.92˝ E Khaprabhanga
7 21°53ʹ43.64˝ N 90°07ʹ23.04˝ E Nijampur
8 21°51ʹ8.86˝ N 90°06ʹ25.30˝ E Nijampur
9 21°40ʹ30.52˝ N 90°05ʹ9.13˝ E Lebur Ban

15. 15
10 21°48ʹ46.11˝ N 90°07ʹ27.56˝ E Kuakta Sea Beach
3.2 Scale of observation, where to start and basic
measurements
Geological observations need to be made at a range of scales. Start at the large regional
scale: this will provide the overall context. Then, consider the whole exposure, followed
by units within the exposure and finally focus down to the hand - specimen scale.
3.2.1 Regional context : Before starting any fieldwork it is essential to research
the regional setting, context and previous work. Aside from books scientific papers and
maps on the regional geology, web – based satellite image display systems such as
Google Earth provide an easy way of investigating the general lie of the land and making
preliminary observations on a large spatial scale and in some cases in more detail. A
desktop regional study may be used to gather information on: access to the field locality
and within it; the overall topography; the type and location of potential exposures; the
general structure and strike of the beds.
3.2.2 Whole exposure : Arriving at a large exposure for the first time can be
both exciting and daunting. It is often difficult to know where to start so, check whether
the exposure is safe and then walk around and view it from different angles before
making a decision.
1. Nature of the contacts
2. Lateral changes in thickness
3. Cross - cutting relationships
4. Evidence of displacement and deformation
5. Angular unconformities

16. 16
Figure : Measuring the length of different sedimentary bed
3.2.3 Hand specimens :
When we select a loose sample, or an area of the unit to examine closely, check that it is
representative of the unit being examined and that it has at least one very fresh surface.
Loose specimens can be hammered to obtain a fresh surface. Only hammer off a small
chip from an exposure if it is absolutely necessary. To select a representative part we
should consider the main features of the unit. For instance if 80% of the unit is sandstone
and the other 20% is a muddy sandstone then ensure that we have a specimen of the main
sandstone. Once we have examined the fresh surface we should supplement our
observations by examining the weathered surface. In some rocks, for instance limestone’s
and metamorphic rocks, differential weathering processes leave some minerals or grains
sticking out of the main surface where they are easier to identify.

17. 17
Figure : Loose sediment including red color sediment indicates Iron
Figure: Ripple marks in Kuakata sea beach
3.3 Overview of possible data formats :

18. 18
The objectives of the fieldwork will determine the most appropriate format for the data
collection. It can also be useful to transfer techniques between different rock types, so the
ranges of field methods are briefly reviewed here.
 Sketches: Sketches on a range of scales both in plain view and cross - section to
show the geometric relationships of rock bodies are used in all aspects of
geological fieldwork.
Figure: Sketches of visiting area
 Graphic logs: These are graphic representations of a stratigraphic succession of
rocks, including information on the facies, boundaries between different units,
bed thickness and lithostratigraphy. Graphic logs are commonly used for
recording changing facies in sedimentary rocks.

19. 19
Figure: Graphic log of stratigraphic succession
 Cross - sections: Field sketches of cliffs and exposures provide one type of
cross - section. Another type that is worth sketching when in the fi eld is a
generalized cross - section of the inferred subsurface geology. This can be
particularly useful where the strata are folded and/or faulted. A sketch cross -
section helps to focus the task and think about different possibilities.
 Maps: Sketch maps and base maps provide an invaluable plan view of the
geological features showing the geometrical relationship between the units and
the location of large - scale geological features.
Chapter 04 : THE FIELD NOTEBOOK
4.1 Introduction: The purpose of field notes The field notebook forms the main
record of the data we gather in the field. In particular, it should contain notes on where
the data were collected, the relationships between the different rock bodies, their
compositional and textural characteristics, and internal features. It usually also records

20. 20
the location of any samples collected, the position and orientation of any photographs
taken, cross references to published information and notes on any ideas that we have for
interpretation or questions raised by our observations. In addition the field notebook
usually links together any other components that we might have used to record data and
ideas in the field. For instance, an electronic database held on a piece of geophysical
equipment, field maps, annotated figures and graphic logging sheets.
4.2 Field notebook layout : designing and using a good field notebook layout
adapted to suit our needs and style will enable us to be systematic in the notes that we
take. This will help ensure that we do not forget major components and that the
information we collect is much more accessible and therefore more readily useable.
Fieldwork can be strenuous and difficult particularly when, for instance, it is raining,
windy, very hot, very cold, at high altitude, or the locality is difficult to access. Quite
often the time available to complete crucial data collection is limited due to
transportation, the hours of daylight, tidal and weather conditions and the overall expense
of completing fieldwork. All of these constraints mean that designing an efficient means
of collecting data in the field will maximize our output.
4.2.1 Preliminary pages : When we start to use a new notebook ensure that we put
our name, address, email and any other contact details in a prominent place on the cover
or immediately inside just in case we should lose it. For the table of contents two to four
pages are usually sufficient with a column for page numbers. Other useful information for
these preliminary pages may include copies of rock classification figures, checklists,
abbreviations and symbols used, photocopies of geological or topographic maps of the
areas we will visit, information on who we need to contact to gain access to the area and
any other information that we might find useful in the field.
4.2.2 Daily Entries : The daily entries will form the bulk of the information in our
field notebook. Example pages for the start of a daily entry are illustrated.

21. 21
Figure : Daily Entries
4.3 Field sketches : A picture is worth a thousand words
Sketches form a vital part of all geological field notebooks. They include: diagrams of
cliffs or quarry faces; sketches of individual features such as a fossil, mineral or
sedimentary structure; sketch maps; cross - sections; and sketches showing ideas for
interpretation. Sketches are one of the best ways of recording and conveying geological
information. This is for two reasons:
1. They provide a shorthand means of conveying information in an easily accessible
form.
2. The very act of producing a good sketch involves carefully observing the features,
units and the relationship between all of them.
4.3.1 : Sketches of exposures

22. 22
Sketches of whole, or representative parts of, exposures such as bedrock, road cuts, river
cross section and quarry faces are commonly used to observe and show one or more of
the following :
1. The main units and the geometric relationship(s) between them;
2. The position of more detailed measurements so that the exact location can be
easily relocated.
Figure : Geologic exposures
4.4 : Written notes: Recording data, ideas and interpretation
4.4.1 Notes recording data and observations
Written notes on the raw scientific data and observations that we collect can range from
bedrock and remain organisms, to structural measurements, to more detailed notes on the

23. 23
relationship between rock bodies. These observations and data should be short notes
rather than full sentences because these take longer to write and can detract from the
main point.
Figure: Observation & Record data
4.4.2 Notes recording interpretation, discussion and ideas

24. 24
As well as new data, we should also record ideas, possible interpretations and questions
when we are in the field to help us test competing theories This might be in the form of a
list, a figure, or even a series of cartoons illustrating a geological history. It is often
useful to record the whole thought process so that we can reanalyze this at a later stage.
Figure: Group discussion
Chapter 05: Recording living organism’s information’s

25. 25
5.1 Introduction:
Unlike many sedimentary particles, such as quartz grains, each fossil has a story to tell
that goes beyond its composition and the way in which it was transported and deposited.
A body fossil represents the remains of a once living organism that had a life history, a
certain environmental tolerance, and a defined range in terms of its geographical and
stratigraphic distribution. Our fieldwork was in Kuakata so there was no presence of body
fossils because the whole area was coastal area and the sediments were newly deposited
but there were possibilities to find out some trace fossils. Trace fossils represent
impressions that an organism made in sediment, such as a footprint, or the disturbance of
sediment as the animal went about feeding, or burrowing to create a living space.
Unfortunately we didn’t get any types of trace fossils but we collected some important
living organisms from those areas.
5.2 Collecting living organism’s data:
For living organisms visible to the naked eye careful observation of morphology, we
should observe three dimensional nature of body of living organisms which we collected
from exposures. It is important to record the body shape, size and to become familiar with
the characteristics of a variety of sections through the organisms. The best items of field
equipment for recording organism’s are:
1.A notebook in which to make sketches.
2. A hand lens to examine detail.
3 .A camera.
5.3 Sampling strategies:
Sampling strategies are much important to recording data which we have collected from
living organisms. Sampling strategies employed to achieve these objectives must be at an
appropriate resolution and carried out efficiently in order to provide valid data.
5.4 Real life Examples: Some of the things that we have studied.

26. 26
Turritella: Turritella is a genus of medium-sized sea snails with an operculum, marine
gastropod mollusks in the family Turritellidae. They have tightly coiled shells, whose
overall shape is basically that of an elongated cone. The shells are quite frequently found
as fossils, and the carbonate stone made from large quantities of Turritella shells is often
referred to as "Turritella limestone".
Figure : Shell of Turritella (Genus)
Conus: Conus is a genus of predatory sea snails, or cone snails, marine gastropod
mollusks in the family Conidae that can be found in the tropical and subtropical seas of
the world.

27. 27
Figure : Shell of Conus (Genus)
Mollusc : The Mollusc (or mollusk) shell is typically a calcareous exoskeleton which
encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which
includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live
in the sea; many live on the land and in freshwater.
Figure : Shell of Apple Snail

28. 28
Figure : Soft Sheel Clam
Burrows: A hole or excavation in the ground made by an animal (as a rabbit,
earthworm, red crab) for shelter and habitation.
Burrow
Burrow

29. 29
Figure : Burrows and burrowing animal
Chapter 06 : RECORDING FEATURES OF SEDIMENTARY
ROCKS AND CONSTRUCTING GRAPHIC LOGS
6.1 Introduction
Sedimentary rocks, particularly coarse - grained siliciclastic rocks, are rewarding to study
in the field. This is because we can gain a lot of information about their mode of
formation directly from field observations and start to make an interpretation without the
need to wait for thin - sections or geochemical analyses, which are required for many
igneous and metamorphic rocks. Some carbonate successions and fine - grained
mudstones can, however, be tricky to interpret in the field and their study can benefit
greatly from follow – up microscope work and/or geochemical analyses. Sedimentary
rocks and the fossils they contain should always be considered together because, as ‘
smart particles ’, fossils provide vital clues on the processes and environment of
deposition of the sedimentary deposits.

30. 30
There are a variety of specific reasons for collecting data from sedimentary deposits aside
from the general ones of geological mapping or constructing a geological history for an
area. These are to:
1. Understand sedimentary processes and depositional environments. This leads to a
better understanding of natural processes on the Earth ’ s surface.
2. Understand the potential of a sedimentary basin or unit for hydrocarbon recovery
or for water resources.
3. Reconstruct past periods of environmental change, particularly climate and sea -
level change. Fine – grained marine sedimentary deposits contain the most
laterally extensive, complete and intact record of the changing chemistry of the
Earth ’ s oceans. Because of the interaction between the oceans and atmosphere,
and that the oceans act like a large mixing pot, marine deposits are fundamental to
understanding the Earth system in the past.
4. Understand and exploit sedimentary building materials and mineral deposits.
6.2 Description, recognition and recording of sedimentary deposits and
sedimentary structures
There are four aspects that need recording in the description of sedimentary rocks:
(1) the composition, which is relatively easy compared with igneous and metamorphic
rocks as there are not many minerals that are common in sedimentary deposits
(2) the texture of the rock;
(3) the sedimentary structures; and
(4) the fossils within them. Composition and texture are taken together as lithology ,
sedimentary structures are covered in Section and the recording of fossils was covered in
Chapter 5 .
6.2.1 Recording sedimentary lithology
Assuming that the sedimentary section under study is divided into units , the next task is
to describe and classify the sedimentary rock type of the unit under consideration.

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Classifying sedimentary deposits provides an approximate quantification of the rock
components and therefore information on the depositional process, sediment source and
environmental conditions.
6.2.2 Recording sedimentary structures
Sedimentary structures are varied and complex. They are dealt with in detail in many
geological textbooks and in specialist sediment logical textbooks A full coverage is
beyond the scope of this book, so instead this section concentrates on how to:
(1) record and describe them;
(2) distinguish between structures that look similar; and
(3) decipher cross - cutting relationships.
Sedimentary structures provide very direct clues about the processes responsible for
deposition of a sedimentary rock, and the processes that occur after its deposition. When
the flow rate changes, some sediment can settle out of the water, adding to point bars,
channel bars and beaches.

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Figure : River morphology
Figure : Sediments deposited on the river channel & bar
Table 6.1 Some sedimentary rock types which we found in field and the
sedimentary structures and features that they are commonly associated with

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Sedimentary
rock type
Depositional features
and sedimentary
structures
Post – depositional
features and
sedimentary
Structures
Commonly
associated
Features
Claystone and
Murdock’s
Lamination :
millimeter - scale
compositional
variation
giving fine - scale
rock banding
Fissility : rock breaks
easily into thin sheets
parallel to bedding
Color : change in
color represents
compositional
variation, particularly
iron minerals, organic
matter and carbonate
content
Fracture pattern :
reflects compositional
variation
Weathering profile :
mudstones with a
higher calcium
carbonate content tend
to stick out as they are
often more resistant to
weathering. Similarly,
Nodules : form
below the
sediment water
interface
under particular
geochemical
conditions. Early
diagenetic
carbonate nodules
can be used to help
calculate the
amount of
compaction. In
some successions
they nucleate on
fossils
Cone - in - cone
calcite : calcite
crystals that grow
in cones
perpendicular to
the
pressure during
over pressuring of
mud rocks
Soft sediment
deformation
Fossils : the low
energy of
deposition, fine -
grained and non -
porous nature
of mud rocks
tends to be
excellent for fossil
preservation, both
mega - and
microfossils.
Trace fossils are
easy to detect if
there is a color
change and the
fine detail is often
well preserved.
Pyrite : this is
often associated
with euxinic
depositional
conditions
Organic matter :
marine and
terrestrial, which
influences color
and can influence

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those with a high
organic - carbon
content tend to
weather
proud. When mud
rocks are interblended
with sandstones or
carbonates the mud
rocks always weather
back.
features : common
for high
sedimentation rate
interblended mud
rocks and
sandstones due to
density contrast of
fresh sediment.
lamination. It
indicates high
productivity and/
or suitable
preservation
conditions
Siltstone and
sandstone
Sedimentary
structures: there is
a wide range many of
which
indicate the processes
of
deposition
Nodules : as
above. Late
digenetic nodules
are more
common
Lies gang rings :
lines of iron
concentration that
form as later fluids
move through the
rock. Can appear
at first glance to be
sedimentary
structures
Fossils : often
present but can be
reworked under
the high - energy
conditions of
deposition
some suggestions for observing, describing and identifying sedimentary structures.
.
1. Should examine the structure if possible in plan view and in cross - section,
preferably in faces that cut through the structure parallel and perpendicular to
the current direction.
2. Identifying the structure is common in the succession or unusual.
3. Recording the size and any systematic variation or repetition, both laterally
and vertically.
4. Recording the position of sedimentary structure within the bed.

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Figure : Sedimentary bedding
Figure : Example of cross-section of bedding

36. 36
Table 6.2 Some of the common depositional sedimentary structures, bed forms and
their process of formation.
Sedimentary
structure or bed
form
Features to observe Processes Day and
Station no
Bedding Continuity,
repetitions,
thickness variation
Varying conditions Station 1
Wave formed
ripple
Three - dimensional.
Climbing or not,
associated with HCS
or SCS or other
structures
Wave Station 3,9,10
Current formed
ripple mark
Three - dimensional.
Climbing or not,
associated structures,
palaeocurrent
Unidirectional
currents
Station 4,7,8
Channel Evidence for base -
level fall; possible
change from marine to
fluvial or submarine
incision
Large - scale
erosion from flow
Station
1,2,4,5,6,7,8
Point bar At the close part of
meandering
Deposition Station 1,6
Natural levee At the side of river
bank
Deposition Station 6
River crick Very small narrow
channel created from
river.
Tide Station 1,6,7,8
Fore shore Near to the sea water
gently getting higher
Deposition Station 9

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to the land
Beach berm Middle of fore shore
and back shore. little
higher than fore shore
and back shore.
Deposition Station 9
Back shore The next part of beach
which connect sea to
the land.
Deposition Station 9
River terrace The outside of
meandering
Erosion Station 1, 7, 8
Small island At the side of a river Deposition Station 2
Meandering Bending of river Erosion and
deposition
Station 1,7,8
Figure: Coastal morphology

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Figure : Tidal creek
Figure: Mud crack

39. 39
Figure : River terrace
Figure : Standing on the natural levee

40. 40
Figure : Small island
Figure : A local inhabitant giving information about the newly formed point bar

41. 41
6.3 Graphic log
These are graphic representations of a stratigraphic succession of rocks, including
information on the facies, boundaries between different units, bed thickness and
lithostratigraphy. This is an idealized and pictorial summary of each of the sedimentary
rock units as they were laid down stratigraphically on top of each other and preserved
Figure : Graphic log and bedding section
6.4 Rocks in space: Reconstructing sedimentary environments and their
diagnostic features
A set of graphic logs in proximal and distal locations, together with sketches and other
information, can be used to record and interpret the depositional environment(s) of the
strata. The graphic logs should provide a summary of features to allow division of the
succession into sedimentary facies (i.e. rock bodies with similar composition, texture,
fossils and sedimentary structures that represent a particular set of processes and
depositional conditions). The construction of facies associations is particularly
appropriate for depositional environments where there are large lateral changes, such as
within a fluvial system. The benefit of carrying out facies analysis is that the facies

42. 42
patterns are then predictable and can be used to assess reservoir and source rock
potential. In summary, facies analysis needs to consider the following.
Table 6.3 : Summary of some of the processes/features and the sedimentary environments
that they might represent. In all cases it is the combination of different lines of evidence
that will help to determine the depositional environment.
Processes/ features Possible environments Staions
Water currents (current -
formed
ripples, cross - stratification,
etc.)
Fluvial, lacustrine or marine 01 , 02, 04, 05, 06, 09, 10
Waves
Large standing body of water,
i.e. large lake or the sea.
Consider: lacustrine or marine
environments (high water
mark to wave base)
09, 10
Tidal features Marine environments near the
coastline
01, 04, 05, 06, 07, 08
Abundance of organic
remains
Delta or fluvial or possibly
lacustrine, sea beach
09, 10
Sedimentary deposits of
highly variable composition
Consider submarine and
alluvial fans, glacial
environments
01, 02, 03, 04, 05,07, 08, 09,
10

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6.4.1 Meandering river depositional environment
A meander, in general, is a bend in a sinuous watercourse or river. A meander forms
when moving water in a stream erodes the outer banks and widens its valley and the inner
part of the river has less energy and deposits silt. Meandering of rivers causes sediment to
deposit. Watercourse deposits sediments to the inner part of the river. These deposition
causes point bar, tidal plain, ox bow lake etc.

44. 44
Figure : Meandering depositional environment
Figure: Working in the Field with Group

45. 45