This document discusses stratigraphy and related geological concepts. It begins by outlining the contents of stratigraphy, including principles of sequence stratigraphy, sedimentary basins, models in sedimentary geology, and applied sedimentary geology. It then discusses key stratigraphic concepts like lithostratigraphy, chronostratigraphy, and biostratigraphy. Finally, it covers principles of correlation, criteria for stratigraphic classification, and elements of correlation like time units, rock units, and correlation methods involving lithological, biostratigraphic, and radioactive dating controls.

1. Dr. V. R Ghodake
Sinhgad College of Engineering, Vadgaon Bk., Pune.
Historical Geology
STRATIGRAPHY

2. CONTENTS
 Stratigraphic principles
 Sequence stratigraphy
 Sedimentary basins
 Models in sedimentary geology
 Applied sedimentary geology
 Reflection
 Introduction
 Unconsolidated clastic sediments
 Sedimentary rocks
 Diagenesis
 Sediment transport and deposition
 Sedimentary structures
 Facies and depositional environments
 Glacial/eolian/lacustrine environments
 Fluvial/deltaic/coastal environments
 Shallow/deep marine environments

3. LITHOSTRATIGRAPHY
EACH LAYER IS A DIFFERENT ROCK TYPE.
Chronostratigraphy
Each layer is a different age.
Biostratigraphy
Each layer contains a different fossil
assemblage.

4. Historical Geology is the science which deals
with the historical development of earth. It
aims at reconstruction of the earths
evolutionary history and formulation of
general laws governing the evolution.
4 Aspects of Historical Geology:
i. To Establish age of rock formation exposed
on the earths surface.
ii. Pertains to paleogeography which
describes the distribution of landforms
and sea in the geological past.

5. iii. Covers past tectonic movements inferred on
the basis of paleogeography and structures of
rocks.
iv. Deals with a synthesis of the paleogeography
and paleotectonics of different parts of earths
crust.
Stratigraphy: deals with mutual relationship and
the succession of rocks.

6. STRATIGRAPHY: Generally called as
Historical Geology. It is the branch of Geology
which deals with the history of rocks with
special emphasis on their approximate time of
formation and changes they undergone from
their formation.
Specially sedimentary rocks gives valuable
information about the geological, geographic
and biologic environment with respect to their
formation. There are imprints of times too in
form of structural deformation and physically
dislocation.

7. PRINCIPLES OF CORRELATION:
Correlation may be understood by establishing
equivalence in rocks formation develop in separate
regions with regards to their geological ages and
stratigraphic position.
 Lateral continuity.
 Lithological similarity.
 Position in Stratigraphic sequence.
 Structural relations.
 Fossils.

8. Principle of Original Horizontality
Sedimentary rock layers (and lava
flows) are formed in a horizontal
orientation. Any folding or tilting
must have happened sometime
after the layers were originally
formed.

9. The Law of Superposition is one of
the most basic principles of geology
. This law states that younger rock
layers will be deposited on top of
older layers, during normal
conditions of deposition. This law is
the basic principle of stratigraphy,
the study of sedimentary rock
layers. Stratigraphy is still the single
best method that geologists have for
determining the relative ages of
rock sequences.
Law of Superposition

10. The Principle of Cross-
Cutting Relationships
states that an igneous
intrusion (or a fault) is always
younger than the rock it cuts
across.

11. In the diagram at the left, the
igneous intrusion (E) must be
younger than rock layers A,
B, C, and D because it
contains inclusions from
those layers.
The Principle of Inclusions states that the rock unit
that contains inclusions is younger than the rock
that the inclusions came from.
Gneiss in Granite

12. CRITERIA FOR STRATIGRAPHIC
CLASSIFICATION & CORRELATION:
Non – Paleontological:
i. Order of Superposition.
ii. Petrographic Characters.
iii. Structures and Tectonics.
iv. Geophysics.
Paleontological.
i. Index Fossils.
ii. Fossil Assemblages.
iii. Micro Palaentology.

13. PALAEONTOLOGY:
The study of fossil records to discover
the history of life, ancient climates and
environments.

14. THE FORMATION OF
MINERALISED FOSSILS
Fossils are formed in a number of different ways:
Most are formed when a plant or animal dies in a
watery environment.
And is buried in mud and silt.
Soft tissues quickly decompose leaving the hard
bones or shells behind.
Over time sediment builds over the top
And hardens into rock.

15. THE FORMATION OF MINERALISED FOSSILS
continuous
As the encased bones decay, minerals seep in
replacing the organic material, cell by cell in a
process called "petrification."
Alternatively the bones may completely decay
leaving a cast of the organism.
The void left behind may then fill with minerals
making a stone replica of the organism.

16. THE FORMATION OF MINERALISED
FOSSILS CONTINUOUS

17. FOSSIL DATING:
 Method used to determine the age of fossils or the strata
(layer of sediment) in which they are found.
 Example of methods;
o Relative dating methods
o Absolute dating methods like Radioactive dating.

18. ELEMENTS OF CORRELATION:
Units : Time and Rock Units.
Time
Era
Period
Epoch
Age
Rock Units.
Group
System
Series
Stages.
Methods:
 Lithological and Structural Control.
 Biostratigraphically.
 Radioactive dating control.

19. Lithostratigraphic Units
Supergroup
Group A
Formation A
Member A
Member B
Member C
Formation B
Member D
Member E
Member F
Formation C
Member G
Member H
Group B
Formation D
Member I
Member J
Member K
Member L
Member M
Formation E
Member N
Member O
Member P
Member Q
Formation F
Member R
Member S
Member T
Supergroup
|
Group
|
Formation
|
Member
|
Bed

20. GEOLOGIC
TIME
SCALE
Era Age (Myrs) Epoch
0.01
Holocene
1.8
Pleistocene
5.3
Pliocene
23.8
Miocene
33.6
Oligocene
54.8
Eocene
65
Paleocene
144
206
248
290
323
354
417
443
490
543
2500
3800
P
r
e
c
a
m
b
r
i
a
n
P
h
a
n
e
r
o
z
o
i
c
Eon
Proterozoic
Archean
Hadean
Period
Quaternary
Tertiary
Neogene
Paleocene
Mississippian
C
e
n
o
z
o
i
c
M
e
s
o
z
o
i
c
P
a
l
e
o
z
o
i
c
Cretaceous
Jurassic
Age of the Earth 4600 Myrs (4.6 Byrs)
Source: Geological Society of America (1999)
Geologic Time Scale
Devonian
Silurian
Ordivician
Cambrian
Triassic
Permian
Pennsylvanian

21. FOSSIL RECORD
The dating of all fossils
is included in the
Geological Time Scale.
This scale divides the
time that the earth has
existed into 4 eras.
Eras are then divided
into periods based on
common events in that
time period.

22. RELATIVE DATING
The science determining the relative order of past
events, without necessarily determining their absolute
age.
Determines which fossils are older or younger.
Easy to determine based on which geological deposit
they come from and the Law of Superposition.

23. The Law of Superposition:
o States that the older layer lies underneath the younger layer in
undisturbed contexts.
o Deeper layers are older than fossils from layers closer to the surface
of the earth.
o The higher up you go in an undisturbed rock stratum (rock layer), the younger the
rock layers become and therefore it is believed the fossils within these layers, are
also younger than the fossils beneath them

24. Undisturbed Sedimentary Rock and its Fossils in
Upper strata generally contain fossils of younger,
more complex organisms, whereas, the lower strata
contain fossils of simpler life forms
There is a tendency toward increasing complexity in
life forms over time

25. STRATIGRAPHIC PRINCIPLES
 Lithostratigraphy = subdivision of the stratigraphic record into sediments or
rocks by means of lithological characteristics and stratigraphic position
 Biostratigraphy = subdivision of the stratigraphic record into sediments or
rocks by means of fossil content
 Chronostratigraphy = subdivision of the stratigraphic record into bodies of
sediment or rock represented by a particular age, separated from underlying
and overlying units by isochronous surfaces
 Geochronology = subdivision of Earth history into time intervals

26. 1. The principle of superposition - in a vertical sequence of
sedimentary or volcanic rocks, a higher rock unit is younger than a lower
one. "Down" is older, "up" is younger.
2. The principle of original horizontality - rock layers were originally
deposited close to horizontal.
3. The principle of original lateral extension - A rock unit continues
laterally unless there is a structure or change to prevent its extension.
4. The principle of cross-cutting relationships - a structure that cuts
another is younger than the structure that is cut.
5. The principle of inclusion - a structure that is included in another is
older than the including structure.
6. The principle of "uniformitarianism" - processes operating in the
past were constrained by the same "laws of physics" as operate today.

27. STRATIGRAPHIC PRINCIPLES
 Type sections (stratotypes) constitute the standard of
reference for definition and recognition of a stratigraphic
unit or stratigraphic boundary; they are defined where
these are representative and well developed
 Stratigraphic relationships can be inferred from the
principle of superposition, unconformities, cross-cutting
relationships, ‘included fragments’, and ‘way-up
indicators’

32. Unconformity Types

34. STRATIGRAPHIC PRINCIPLES
Lithostratigraphy
 Lithostratigraphic units are commonly diachronous, as
opposed to chronostratigraphic units
 Detailed geologic mapping is usually strongly based on
lithostratigraphy, whereas overview geologic maps usually
show chronostratigraphic units
 Although objective lithostratigraphic classification should be
as simple and straightforward as possible, reality
demonstrates that this is not always the case; as a result, in
many areas revisions are frequently proposed which can lead
to extremely complicated and confusing situations

36. STRATIGRAPHIC PRINCIPLES
Biostratigraphy
 A vast diversity of types of fossils exists; the following
criteria are important in determining how useful they are for
strictly stratigraphic purposes of correlation:
• Abundance and size
• Degree of dispersal
• Preservation potential
• Rate of speciation
 As a result, especially numerous marine microfossils (e.g.,
forams) are stratigraphically highly useful, whereas others
are more valuable for paleoecologic purposes
 Numerous pitfalls exist in the correlation of biozones (e.g.,
Quaternary pollen zones)

38. FOSSILS & THE GEOLOGIC
TIME SCALE

39. FOSSILS
 Preserved remains or traces of an
organism that lived in the past.
•Fossils are formed when organisms
die and are buried in sediment.
Eventually the sediment builds up and
hardens to become sedimentary rock.

40. Petrified - when minerals
replace the remains and they
become rock
Mold when the shell remains
and the contents dissolve (hollow)
Cast- when the mold becomes
filled with minerals that are not a part
of the original organism

41. Sometimes whole animals become preserved
intact, but this is very rare. If an organism is
surrounded by ice or tar they might be discovered
looking much the same as they did when they
died.
AETOSAUR
FOUND IN
THE
NATIONAL
PETRIFIED
FOREST

42. RELATIVE DATING
Relative dating: looks at where the fossil is located
to determine its age relative to other fossils. This
only works if the area has been undisturbed.

43. ABSOLUTE DATING
Uses radioactive elements near the fossils to determine
the actual age of the fossils.
•By determining the age of the radioactive element, scientists
can calculate the age of the fossil buried nearby.
The absolute age
of fossils is
estimated by
dating
associated
igneous rock and
lava flows.

44. PRE-CAMBRIAN
Began with the
formation of the
Earth 4.6 billion
years ago.
Bacteria
appeared 3.5
billion years ago,
followed by algae
and fungi.

45. PALEOZOIC ERA
Divided into 5 periods:
Cambrian period -
Sponges, snails, clams
and worms evolve
Ordovician period - First
fishes evolved and other
species become extinct
Silurian period - Land
plants, insects and
spiders appear

46. Devonian period-
Amphibians evolve and
cone-bearing plants
start to appear.
Carboniferous period
Tropical forests appear
and reptiles evolve.
Permian period- Seed
plants become
common and insects
and retiles become
widespread. Sea
animals and some
amphibians begin to
disappear.

47. MESOZOIC ERA
 Divided into 3 periods:
 Triassic period - Turtles and
crocodiles evolve and dinosaurs
appear.
 Jurassic period - Large dinosaurs
roam the world. First mammals
and birds appear.
 Cretaceous period - Flowering
plants appear, mammals become
more common dinosaurs

48. CENOZOIC ERA
Divided into 2 periods:
Tertiary period - First
primates appear and
flowering plants
become the most
common.
Quaternary period -
Humans evolve and
large mammals like
woolly mammoths
become extinct.

49. Cross Cutting Relationships in strata

50. Stratigraphy
That’s all about the