The document summarizes key concepts and observations from a geological field trip to Chandipur Beach. It discusses the different sedimentary facies observed, including sand berms, backshore, foreshore, and tidal flats. Primary structures like ripples and dunes are described. Observations of minerals, slopes, fossils and other features are provided for each facies. Concepts like transgression, regression, and Walther's law are explained in the context of interpreting the depositional environment and history. Detailed field observations, measurements, and photographs support the descriptions.

1. GEOLOGICAL FIELD TRIP
Chandipur
Objectives-
 To study the sedimentary facies and sedimentary structures in
and around Chandipur Beach
 To understand the direction of current and wave
CONCEPTS LEARNED -
Sedimentology is the study of the processes of formation, transport and
deposition of
material that accumulates as sediment in continental and marine
environments and
eventually forms sedimentary rocks.
Stratigraphy is the study of rocks to determine the
order and timing of events in Earth history: it provides the time frame that
allows us to
interpret sedimentary rocks in terms of dynamic evolving environments.
Silt is defined as the grain size of material between 4 and 62 microns in
diameter. This size range is subdivided into coarse, medium, fine and very
fine. The coarser grains of silt are just visible to the naked eye or with a hand
lens. Finer silt is most
readily distinguished from clay by touch, as it will feel ‘gritty’ if a small
amount is ground between teeth,
whereas clay feels smooth.
Clay is a textural term to define the finest grade of clastic sedimentary
particles, those less than 4 microns in diameter.Clay minerals are a group of
phyllosilicate minerals that are the main constituents of clay-sized particles.

2. When clay- and silt-sized particles are mixed in unknown proportions as the
main constituents in unconsolidated sediment
Sedimentary Facies-A sedimentary facies is a body of sediments with
specified characteristics that reflect the conditions under which it was
formed (Reading & Levell 1996).Describing the facies of a body of sediment
involves documenting all the characteristics of its lithology,texture,
sedimentary structures and fossil content that can aid in determining the
processes of formation
Four different types of sedimentary facies -
 Sand Berm – The sedimentary facies having steeper slope with
vegetation on it and having a dry land. Pile of sand formed due to
Aeolian activities. It consists of heavy particles.
 Backshore – The sedimentary facies which extends from the limit of
high water foam lines to dunes or sand berms .It is affected by waves
during exceptional high tides or severe storms.
 Front Shore- The part of a shore between high and low water marks
or between the water and cultivated or developed land
 Tidal flat- the coastal wetlands that form when mud is deposited by
tides or rivers. They are found
The below figure explains the transportations of sediments which
results in the formation of sedimentary ripples in berm region .
The below figure shows the ripples in tidal flat .

3. DUNES - Beds of sand in rivers, estuaries, beaches and marine environments
also have bedforms that are distinctly larger than ripples. These large
bedforms are called dunes. the term ‘megaripples’ is also sometimes used,
although this term fails to emphasise the fundamental hydrodynamic
distinctions between ripple and dune bedforms.

4. SHARP CHANGE IN TOPGRAPHY –
As we move from sand dunes / sand berms to tidal flat , the dip angle
decreases from 17 degrees in sand berms to 2-3 degrees in backshore
and frontshore to less than 1 degrees in Tidal Flat.As we move
perpendicular to shore , the morphology of the rocks changes from
sand particles to silts to clay .Also , as we move from sand berms to
tidal flat ,the hardness of the region increases and the stickiness
decreases.
Changes in patterns of ripples are observed. These patterns changes
everyday. As we move away from the coast line, the ripples patterns
changes –
It becomes angular to the coast line
It becomes edge shaped (Rounded)
They become elongated (Rectangular)

5. Becomes wavy structures
WHY ALGAE ONLY IN TIDAL FLAT?
Algae get nutrients in clay, that’s why they stay there. Nutrients
in tidal flat region are carried by ground water because the slope of ground
water beneath the surface is much lower than any other sedimentary facies.
The figure below shows the algae in tidal flat region.
PRIMARY AND SECONDARY SEDIMENTARY STRUCTURES –
Primary structures are those which we see in modern sediments and
are preserved in rocks Secondary structures are those which are formed
after the rocks have been formed
 DEPOSITION HISTORY –

6. Firstly , Sediment are carried from balasore to chandipur through Aeolian
and water activities .During this carry , minerals like plagioclase feldspar and
alkali feldspars get destroyed.
Secondly, the deposition is from sea, which leaves patterns on ocean floor.
The above Hjulstrom diagram shows the relationship between the velocity
flow and the transport of loose grains on the basis of their grain size

7. The heavier particles are settled near the berms and the finer grained
particles are carried way deep in the ocean resulting in the different
sedimentary facies.
As we move away from the shore line the grain size decreases -
Four basic divisions are recognised:
clay (<4 mm)
silt (4 mm to 63 mm)
sand (63 mm or 0.063 mm to 2.0 mm)
gravel/aggregates (>2.0 mm)
MARINE TRANSGRESSION AND REGRESSION -
Transgression – time when sea goes to land in geologic time scale is called
as transgression
Regression – time when land moves away from sea in geologic time scale is
called as regression
Dynamic equilibrium between coastline and sea line.Ocean is the primary
basin. Capacity depends on tectonic forces and topography
EFFECT OF GLOBAL WARMING –
Due to global warming , the ice caps will melt and the sea level will rise
(approx. 1 m) ,the marine transgression occurs because the sea level rises
and submerges the coast in it . Thus the coast line shifts backward (i.e .
Coast Regression ) occurs .The proof of this hypothesis is that , while moving
perpendicular to the shore line , it is observed that some charcoal tracers

8. were found parallel to the shore line which is the proof that the coast line
millions of years ago was here.
SYMMETRIC AND ASYMMETRIC RIPPLES -
Symmetry ripples are formed from Bi-directional forces.When these forces
are equal in magnitude and opposite in direction , they forms stoss and lee
sides which are equal in lengths .
Asymmetry ripples are formed from Uni-Directional forces. Thus , due to a
uni directional force , sediments are eroded from stoss side of the ripple and
gets deposited on lee side of the ripple thus , the lengths of stoss and lee
sides differ from each other .
CURRENT RIPPLES –
Current ripples are small bedforms formed by the effects of boundary layer
separation on a bed of sand (Baas 1999). The small cluster of grains grows to
form the crest of a ripple and separation occurs near this point. Sand grains
roll or saltate
up to the crest on the upstream stoss side of the ripple. Avalanching of
grains occurs down the downstream or lee side of the ripple as accumulated
grains become unstable at the crest. Grains that avalanche on the lee slope
tend to come to rest at an angle close to the maximum critical slope angle
for sand at around 308. At the flow attachment point there are
increased stresses on the bed, which result in erosion and the formation of a
small scour, the trough of the ripples.

9. WAVE AND CURRENTS –
Distinguishing between wave and current ripples can be critical to the
interpretation of palaeoenvironments. Wave ripples are formed only in
relatively shallow water in the absence of strong currents, whereas current
ripples may form as a result of water flow in any depth in any subaqueous
environment. These distinctions allow deposits from a shallow lake are to be
distinguished from offshore or deep marine environments .for example. The
two different ripple types can be distinguished in the field on the
basis of their shapes and geometries. In plan view wave ripples have long,
straight to sinuous crests which may bifurcate (divide) whereas current
ripples are commonly very sinuous and broken up into short,curved crests.
When viewed from the side wave ripples are symmetrical with cross-
laminae dipping in both directions either side of the crests. In
contrast,current ripples are asymmetrical with cross-laminae dipping only in
one direction, the only exception

10. HEAVY MINERALS DEPOSITED IN BERMS –
Heavy minerals get deposited in sand berms but not in front shores and tidal
flats region because as the sediments are carried from balasore to chandipur
region , the heavier material falls downwards with sand particles and only
finer grain particles are carried forwards , hence , giving the ripples a
blackish colour.
The figure below shows the black minerals clearly visible over the ripples
formed by aeolian deposits.
RIPPLE INDEX AND SYMMETRY INDEX –
Ripple index – The ratio of wavelength of the ripple is to the height of the
ripple formed by wave or current action.
Symmetry Index – The ratio of lengths of stoss side to lee side of ripple is
called symmetry Index.
RI < 4 – Ripples are formed by Wave Action

11. RI >15 – Ripples are formed by Current Action.
SI = 1 ( Symmetric Ripples are formed )
SI <1 ( Asymmetric Ripples are formed )
OBSTACLE MARKS – The marks which are left away when water recedes
away from front shore during its interaction with shales .
SWASH RIPPLES – The unique patterns of ups and downs obtained in the
Front shore is called swash ripples .
The figure below shows the horizontal swassh ripples clearly visible .
PARTING LINEATIONS – The groove where shales are deposited orthogonal
to the shore line and occur in alternate patterns is called parting lineations.
The figure below shows the parting lineations clearly visible perpendicular to
the shore line.

12. LADDER RIPPLES – The ripples obtained in the area of depression between
two ripples
ROSS DIAGRAM – Frequency Distribution of the plunge of the ripples in
different sedimentary facies
For example – obstacle marks in front shore , sand ripples in sand berms /
Dunes.

13. MUD BALLS –
Found in the area between front shore and tidal flat.Mud balls are formed
as a result of collection of water. If the water has sufficient energy such that
it exceeds the cohesive force between clay particles. It scoops out the clay
and roll it along the minimum diameter to form mud balls.
Once the mud ball is formed . Coming in Water will provide sufficient
torque ot rotate it aloing the longest direction thus , helps in determining
the water direction .
Now the mud ball is aligned in the direction of water flow , thus when
further water comes it acts as a obstacle to water , thus water will
continuously erode the sediment and mud ball will topple in the depth
formed . Thus these mud balls are preserved in the sedimentary sequence.
The below figure shows the mud ball which is nearly spherical ( Figure 1 )
The Second Figure shows the Mud ball naturally placed within the eroded
depth .
FIG – 1 FIG-2

14. BARRIER BAR –
A sand body having huge amount of sand deposited very quickly in front of
shore because of events like storm.
HOW MUDDY AREA IS FORMED IN OPEN ( I.E BETWEEN FRONTSHORE AND
TIDAL FLAT ) ??
It is because of coast regression . Previously , a sand barrier may have been
lying opposite to the muddy area (i.e in the area of tidal flat), now as the
water level increased , the barrier bar got destroyed/eroded and the coast
shifted backward (i.e coast regression took place) , Thus this transgression of
sea shore is called Local Transgression Sequence.
Thus the water collected in between the two barriers resulted in the
formation of marshy land .
WALTHERT’S LAW –
It states that the sedimentary facies which are occurring in vertical sequence
today , they have been lying adjacent to each other many years ago.
The figure below shows the alternate bands of sediments and clay
depositions which proves the walthert’s law and marine transgression and
regression .

15. REEL MARKS – Due to enough pressure in the surroundings nearby, the
ground water discharge takes place occasionally along a valley which occurs
in front shore region . This valley is called Reel Marks
The figure below shows the reel marks which are ground water coming out
of the land fgrom the pressure of the rocks above the land.

16. FIELD WORK (OBSERVATIONS ) -
 Sand berms-
o Steep Slope around 17-20 degrees.
o Consists of mostly silica with traces of heavy black
minerals on the crests of ripples. They might be
hornblende ,tourmaline.(Figure)
o Particles are relatively coarser grained because this region
has a high energy environment created due to the
interaction of land and sea breezes.
o Ripples formed due to Aeolian activities
o Heavy Minerals are clearly observed over the ripples.

17. The below figure shows the ripples formed in the sand berms due to the
Aeolian deposition .
 Back Shore-
o Few obstacle marks
o Swash Ripples- low amplitude ripples with long
wavelengths.
o Slope varies from 2-5 degrees
o Mostly sand particles
o Heavy minerals (Hornblende + Pyroxene) are found in
valley,Biotites are observed on the surface ( or crest) of
the ripples.
 Fore Shore-
o Slope varies from 1-2 degrees
o Consists mostly of fine grained sand particles
o Large number of obstacle marks were found
o Obstacle marks- parabolic pathways along which the water
flowed around the shells

18. o Parting Lineation-Due to the formation of eddy currents
one side gets eroded and other gets accumulated by shells
(figure)
o Direction of obstacle marks mostly N-W( appendix)
o Parting Lineations are observed.
 Tidal Flat
o Slope is less than 1 degree
o Consists of silt and clay minerals
o Pattern keep on changing across the tidal flat.
o Cross stratigraphy is observed.
o Ripples are observed to be formed from cross currents
which originate due to Wind , Air and Gyration of Earth.
o Different structures of ripple marks-Elongated, Linear,
angular, eye shaped, net shape
o Green coloring of tidal flat indicating presence of Algae
due to ground water which leads to presence of nutrients
helping in algae formation
o Presence of charcoal indicating the transgration
movement(definition )(theory of vegetation).
o Biotite presence at crests and fine particles of hornblende,
tourmaline at trough.
o Mostly asymmetric and some symmetric ripples
o Ripples vanishing across the shore .formation of ripples
depends on energy and height
o Due to pressure , Iron on the surface gets oxidized to ferric
oxide and we get brown colour liquid. As shown in the
figure below

19.  Barrier Bars
o Sand particles
o Topography in the region entirely different
o High vegetation between barrier bars and dunes due to
accumulation of water(marshy lands).Clay particles found
o Area after barrier Bar is called Paleo Mud which might
have formed due to the presence of another barrier bar
further ahead indicating trangration
o Alternate Clay and Sand layers found on digging proving
local transgration and regration
o Mud balls found which might have due to the scooping of
sediments
o Direction of mud balls indicating current direction
o Imbricated mud ball
o

20. TIDAL FLAT RIPPLES DATA:

24. FUNDAMENTALS of HISTORICAL GEOLOGY and STRATIGRAPHY
- Ravindra Kumar (20006)