GEOLOGY

CEM209N

BY – SHIVANI R. CHANDNANI
PhD Pursuing – National Institute of Technology (NIT), Raipur
M.E – Geotechnical Engineering
B.E. – Civil Engineering
DESCRIPTION OF UNITS
Unit
Description of Units
no.
1. General Geology, Geomorphology, Structural Geology

2. Paleontology, Stratigraphy

Igneous & Metamorphic Petrology, Sedimentary

3.
Petrology
4. Minerology & Economic Geology

5. Engineering Geology & Environmental Geology

6. Geophysical Exploration Methods

 MARKING SCHEME
EVALUATION SCHEME
Duration of ESE – 03 hours
MSE ISA ESE
30 10 60
100

COURSE OUTCOMES (CO’s)

1. Understand earth process & geological formation.

2. Identify the geological structures & properties of rock.
3. Understand physical properties, mechanical properties of the
minerals and their application.
 Stratigraphy
• Stratigraphy is a geological discipline that studies
the formation, distribution, composition, and age
relationships of rock layers (or strata).
• The term stratigraphy comes from two Latin and
Greek roots:
Stratum (Latin): Meaning "layer" or
"something spread out.“
Graphia (Greek): Meaning "writing" or
"description."
• It provides a way to understand the sequence of
geological events over time, helping geologists
interpret Earth’s history, environmental changes,
and structural developments.

• Thus, stratigraphy refers to the description of rock layers or the science of identifying
and analyzing layered materials, primarily focusing on their arrangement and
historical sequencing.
 Stratigraphy & Paleontology
Stratigraphy: The study of rock layers (strata) and
their organization, which includes the analysis of the Paleontology: The study of fossils and ancient life forms,
distribution, composition, and age of these layers. including their structure, evolution, distribution, and interactions
Stratigraphy focuses on understanding geological with their environments. Paleontologists seek to understand the
time scales and the processes that lead to the history of life on Earth, including the patterns of extinction and
formation and alteration of sedimentary rock layers. diversification.

The presence of specific fossils in a stratigraphic Fossils are often found within sedimentary rock layers, making
layer can indicate the age of that layer based on them vital for stratigraphic analysis. Paleontology provides
the known geological time range of the fossils. This is crucial data through fossils that help geologists interpret the
particularly useful for correlating layers across relative ages of rock layers and establish a timeline of Earth's
different geographic locations. history.

Stratigraphy helps understand how sedimentary

environments have changed over time, while
paleontology reveals how life adapted to those Paleontologists provide the necessary taxonomic and
changes. For example, changes in sediment ecological information about fossils, enabling stratigraphers to
composition or depositional environments (e.g., construct a framework for geological timelines and correlate
marine vs. terrestrial) reflected in stratigraphic sedimentary sequences.
records can be correlated with fossil records that
indicate shifts in biodiversity.
Branches of Stratigraphy
 Branches of Stratigraphy
1. Lithostratigraphy
• Lithostratigraphy focuses on the classification, correlation, and interpretation of rock layers
(strata) based on their lithology.
• Lithology refers to the physical characteristics of rocks, such as color, texture, mineralogical
composition, etc. Lithostratigraphy emphasizes these characteristics to identify rock units
and distinguish one layer from another.
• Basically lithostratigraphy aims to divide rocks into formal stratigraphic units. These units are
based purely on their lithological properties rather than their age or fossil content. The
primary lithostratigraphic units are:
a) Formation: It represents a mappable body of rock with distinct lithological
features. Eg. The Chalk Formation in Europe is recognizable by its soft, white
limestone.
b) Member: A smaller, more specific subdivision of a formation with unique
lithological characteristics. Eg. The Kaibab Member within the larger Kaibab
Formation.
c) Bed: The smallest lithostratigraphic unit, often used to describe thin, distinct
layers. Eg. A coal bed within a larger sandstone formation.
d) Group: Several related formations are combined into a group. Eg. The Chalk
Group from Cretaceous period found in England, France, Germany and
Denmark
 Branches of Stratigraphy
2. Biostratigraphy
• Biostratigraphy is the branch of stratigraphy that uses fossil organisms to date and correlate rock layers. Since
different species evolved and went extinct at specific times, their presence or absence in a rock layer provides a
relative time framework for geologists to understand Earth's history and correlate strata across regions.
• It includes the study of fossil succession (fossil species appear, thrive, and become extinct in a definite order
through geological time and index fossils to identify time periods based on fossil content.
• A biozone is a stratigraphic interval defined by the occurrence of particular fossils. These biozones serve as the
basic units of biostratigraphic analysis.
a) Taxon Range Zone: Represents the stratigraphic interval between the first appearance
and the last appearance of a single fossil species in the rock record. It is useful in defining
the entire range of a fossil’s existence within a particular time frame.
b) Concurrent Range Zone: Interval where the ranges of two or more species overlap. This
type of biozone is used to narrow down a time frame when multiple species coexisted.
c) Interval Zone: Marks the interval between two evolutionary or extinction events, even if
fossils are scarce within that interval.
d) Assemblage Zone: Characterized by a distinct combination (assemblage) of several
fossil species that occur together. It helps to identify specific depositional environments
or paleoecological conditions. Assemblage zones are not tied to single species but
reflect the association of multiple taxa.
e) Abundance Zone: Represents the interval where a particular species occurs in
exceptionally high abundance (acme) compared to other layers. Marks environmental
or ecological changes that favored the rapid proliferation of a species. Acme zones are
often associated with climatic shifts or nutrient-rich conditions.
 Branches of Stratigraphy
3. Chronostratigraphy
• Chronostratigraphy is a branch of stratigraphy focused on the age of rock strata and their
placement within a standardized geological time framework.
• Its primary aim is to establish the absolute or relative age of rock layers and link them to
specific geological time units, such as periods, epochs, or ages.
• The fundamental units of chronostratigraphy represent divisions of Earth’s rock record based
on their relative time of formation.

Chronostratigraphic
Units Eonothem Erathem System Series Stage Chronozone
Eon Era Period Epoch Age Chron
Geochronological
Equivalents Phanerozoic Mesozoic Cretaceous Upper Maastrichtian Brunhes
Eonothem Erathem Period Jurassic Stage Chronozone
Examples Series

Chronostratigraphy makes use of techniques such as radiometric dating and global

stratotype section and point (GSSP) to establish the age and correlation of rock layers within
the Earth’s history
 Branches of Stratigraphy
3. Chronostratigraphy
• Radiometric dating is a method used to determine the absolute age of rocks and minerals by measuring
Radiometric the decay of radioactive isotopes.
dating • A radioactive isotope (also called a radioisotope or radionuclide) is an unstable form of an element’s
atom that has an excess of energy or mass in its nucleus, causing it to decay over time. During this
decay, the atom emits radiation (such as alpha, beta, or gamma particles) and eventually transforms
into a more stable isotope or a different element.
• Examples include:
a) Uranium 238 & Thorium 232 formed during stellar nucelosynthesis in stars.
b) Carbon 14 formed in the earth’s atmosphere
c) Cobalt 60 produced by bombarding Cobalt-59 with neutrons in a reactor and is used in cancer
treatment and sterilization.
d) Radon-222 is a radioactive gas produced from the decay of Uranium-238.
• Radioactive isotopes (parent isotopes) decay into stable isotopes (daughter isotopes) at a predictable
How rate, known as the half-life. By measuring the ratio of parent to daughter isotopes in a sample, geologists
Radiometric can determine the amount of time that has passed since the rock or mineral formed.
• For example:
dating works??
Uranium 238 Lead 206 4.5 billion years Useful for dating igneous & metamorphic rocks
Potassium 40 Argon 40 1.25 billion years Dating volcanic rocks such as Mica, Feldspar Older than 100000 years
Organic material such as wood, charcoal, bone, shells (Upto 50000
Carbon 14 Nitrogen 14 5730 years
years old)
 Branches of Stratigraphy
3. Chronostratigraphy
• In radiocarbon dating, scientists measure the amount of Carbon-14 still present in a sample (such as a bone or piece of
Radiometric wood).
dating • Although Nitrogen-14 is produced, it escapes from the sample. Instead of measuring nitrogen, scientists compare the
Carbon-14 content of the sample to modern levels of C-14 in the atmosphere to estimate how much has decayed.
• By comparing the current amount of C-14 (parent) to what it originally would have contained, scientists determine how
many half-lives have passed and thus calculate the sample’s age.
Fraction of C-14 Parent-to-Daughter
Elapsed Time C-14 (Parent) N-14 (Daughter)
Remaining Ratio
Example of
0 years (start) 100% 0% 1.00 100:0
Carbon-14 (C-14)
5,730 years 50% 50% 0.50 1:1
with a half-life of
11,460 years 25% 75% 0.25 1:3
5,730 years.
17,190 years 12.5% 87.5% 0.125 1:7
22,920 years 6.25% 93.75% 0.0625 1:15

• Half-life: The time it takes for half of the atoms in a sample of a radioactive isotope (parent) to decay into the stable
(Age of rock) t = n * Half- product (daughter).
Life in years. • After each half-life, half of the remaining parent isotope converts into the daughter isotope. This pattern continues over
multiple half-lives.
 Branches of Stratigraphy
3. Chronostratigraphy
• A Global Stratotype Section and Point (GSSP), also known as a “golden spike,” is a physical reference
Global point in the rock record that marks the boundary between two chronostratigraphic units, such as periods,
stratotype epochs, or stages.
section and • GSSPs provide standardized global references for geological time intervals, ensuring that rock layers
worldwide can be correlated accurately.
point (GSSP)
• GSSPs provide a physical reference point that serves as the base of a new time unit (e.g., the start of a
new period or epoch).
• Criteria for selecting a GSSP::
a) The section must be easily accessible for study and contain an uninterrupted, clear sequence of
rock layers.
b) It must contain fossils, chemical markers, or events that are recognizable across different regions.
c) A GSSP is often based on a significant biological or geological event, such as the first appearance
of a species or a magnetic reversal.
d) The site should be protected for future research and maintained for long-term accessibility..
• For example:
• Cretaceous-Paleogene (K-Pg) Boundary: The GSSP for this boundary is located in El Kef, Tunisia. It is
marked by a thin clay layer with high iridium content, indicating an asteroid impact that led to the mass
extinction of dinosaurs.
 Branches of Stratigraphy
4. Sequence Stratigraphy
• Sequence stratigraphy is a branch of stratigraphy that analyzes rock layers (strata) based on their
depositional sequences.
• It focuses on understanding the arrangement and distribution of sedimentary layers, their boundaries,
and the processes that controlled their deposition over time, particularly in response to sea-level
changes, tectonics, and sediment supply.
a) Depositional Sequence: A sequence typically represents a complete cycle of sedimentation from
transgression (sea-level rise) to regression (sea-level fall).
b) Unconformities: These are surfaces representing gaps in the geological record, often caused by
erosion or non-deposition. They act as key boundaries between sequences.
c) System Tracts: A systems tract is a subdivision of a sequence, representing distinct phases of relative
sea-level change and sediment deposition. Each system reflects different sedimentary
environments and is associated with either rising, falling, or stable sea levels.
Lowstand System tract Transgressive System tract Highstand System tract Falling Stage System tract
Sea level is at its lowest or Occurs during a sea-level rise, leading to the Sea level stabilizes or reaches a Sea level begins to fall after
is falling. landward migration of shorelines. maximum height. reaching a highstand.
Sediments accumulate in Sediments get thinner as they move toward Sediments prograde (build Erosional surfaces may develop
deep basins the coast, indicating deepening water seaward) into the basin
environments.
Eg. Deltaic or fluvial Eg. Shallow marine sediments Eg. Coastal and shallow marine Erosion of shorelines and delta
sediments at the base of sands. progradation into deeper basins.
a sequence.
 Branches of Stratigraphy
5. Magnetostratigraphy
• Magnetostratigraphy is a branch of stratigraphy that uses the magnetic properties of rocks to determine
their age and correlate them across regions.
• This technique relies on the fact that Earth's magnetic field has undergone periodic reversals over
geological time, where the magnetic north pole flips to become the south pole and vice versa. By
studying the pattern of these magnetic reversals recorded in rocks or sediments, geologists can build a
chronological framework to understand Earth's history and date various geological events.
a) Earth’s Magnetic Field: Earth has a magnetic field generated by the movement of molten iron
within its core. This field periodically reverses in polarity.
b) Remanent Magnetization: As igneous rocks (like basalt) cool from a molten state, iron-rich minerals
(e.g., magnetite) align with Earth's magnetic field at the time of cooling. This alignment is "frozen" in
place, preserving the magnetic polarity.
c) Magnetic Reversals: Over geological time, Earth’s magnetic field has reversed many times. These
reversals occur irregularly but leave a recognizable pattern in the rock record, known as a
magnetostratigraphic sequence.
d) Magnetostratigraphic Correlation: The sequence of magnetic reversals recorded in a region can
be correlated with the Global Magnetic Polarity Time Scale (GMPTS), a standard record of all
known magnetic reversals.
• For example: The Olduvai Subchron (1.95–1.78 million years ago) is a well-known reversal event used to
date hominid fossils in Africa, providing crucial insights into human evolution.
 Principles of Stratigraphy
Principle Description Example

in an undisturbed sequence of sedimentary rocks, the If a geologist finds multiple sedimentary

oldest layers are at the bottom, and the youngest layers rock layers stacked on top of each other,
Law of
are at the top. This principle, first articulated by Nicholas the bottommost layers will be older unless
Superposition
Steno, helps determine the relative ages of fossils based on the sequence has been overturned or
their position within rock layers. disrupted.
This principle states that sedimentary rocks are initially
Sandstone and shale beds that are tilted in
Principle of deposited in horizontal layers. If rock layers are found tilted
a mountain range suggest they were
Original or folded, it suggests that geological forces (such as
originally flat but were later deformed by
Horizontality earthquakes or tectonic movements) disturbed the layers
tectonic forces.
after deposition.
Sedimentary layers extend horizontally over large areas Limestone beds found in two distant regions
Principle of Lateral unless they are interrupted by barriers or changes in the may be considered part of the same
Continuity environment (e.g., river channels). This principle is useful for formation if there is no interruption in their
correlating fossils across distant areas. continuity (e.g., a river eroding through it).
fragments (inclusions) within a rock unit must be older
than the rock containing them. If pieces of one rock are A conglomerate containing pebbles of
Principle of
found inside another, the included fragments (inclusions) granite implies the granite existed before
Inclusion
represent pre-existing material incorporated into the the conglomerate formed.
younger rock.
 Principles of Stratigraphy
Principle Description Application

Proposed by William Smith, the principle of faunal

succession states that fossil organisms succeed one
Principle of A rock layer containing trilobite fossils is
another in a definite, recognizable order through
Faunal likely older than one containing dinosaur
geological time. This principle reflects evolutionary
Succession fossils, as trilobites existed earlier in the
changes—older layers contain more primitive life
(Biostratigraphy) geological time scale.
forms, while younger layers contain more advanced
organisms.
Proposed by James Hutton and popularized by Charles
Lyell, this principle states that the same natural
Observing rivers depositing sediment
Principle of processes we observe today—such as erosion,
today suggests that ancient river
Uniformitarianism sedimentation, and volcanic activity—also occurred in
deposits formed similarly in the past.
the past. This means “the present is the key to the
past.”
Principle of This principle states that any geological feature (like a If a basaltic dike cuts through sandstone
Cross-cutting fault or igneous intrusion) that cuts through a rock layer layers, the dike is younger than the
relationships must be younger than the layer it cuts. sandstone.
 Principles of Stratigraphy
Principle Description Application

An unconformity is a surface within a sequence of layers

that represents a gap in the geological record. It indicates An angular unconformity indicates tectonic
Principle of
a period of erosion or non-deposition. Recognizing activity occurred before new sediments
Unconformities
unconformities helps geologists interpret significant events were laid down.
like sea-level changes or tectonic uplift.
Imagine a beach next to the ocean. As the
Laterally adjacent sedimentary environments will shift sea level rises (a transgression), the beach
Principle of vertically in a predictable manner when there is a change will get submerged, and marine sediments
Walter’s Law of in sea level or sediment supply. The way environments shift will be deposited on top of the beach
Facies sideways (like beach to ocean) will reflect vertically in the sands. Later, if the sea level drops (a
layers of rock (sand below, marine mud above). regression), coastal sands may once again
cover the marine sediments.
Just like rivers today leave layers of mud
Actualism extends the idea of uniformitarianism, along their banks, ancient rivers also did the
Principle of emphasizing that past processes may not always behave same. However, ancient rivers might have
Actualism exactly as they do today, but the fundamental rules of carried different types of minerals or flowed
physics and geology still apply. differently due to changes in climate or
geography.
Stratigraphic Nomenclature
• Stratigraphic nomenclature is the system of naming and classifying rock layers
(strata) based on their distinct characteristics, such as lithology, fossil content,
or age.
• It provides a structured way for geologists to describe, classify, and correlate
rock units systematically. This nomenclature ensures that rock units are
consistently defined and named across different regions and geological
contexts.
• Stratigraphic nomenclature follows specific rules and guidelines established by
international bodies such as the International Commission on Stratigraphy (ICS)
to ensure that names are precise, non-redundant, and widely accepted.
• The key rules of stratigraphic nomenclature include:
a) Uniqueness: Each unit should have a unique and distinctive name.
b) Priority: Names that were published first have priority.
c) Type Section: Every named unit must have a type section (or
stratotype), a well-defined locality where the unit is best exposed and
studied.
d) Non-overlapping Names: Units must not have duplicate or
overlapping names to avoid confusion.
 Stratigraphic Nomenclature
Lithostratigraphic Units

Group Formation Member Bed

Bundelkhand Group Dakota Sandstone Marcellus Member Coal Bed

Stratigraphic Nomenclature
Biostratigraphic Units
Biozone: A stratigraphic unit defined by the presence of
certain fossils or groups of fossils. Biozones are important for
correlating and dating rock layers.
Boundaries:
• FAD (First Appearance Datum): Marks the first
appearance of a particular fossil in the geological
record.
• LAD (Last Appearance Datum): Marks the last
appearance of a fossil in the record.
Types of Biozones:
• Range Biozone: Defined by the total range of a
single species or taxon (the interval between its FAD
and LAD).
• Interval Biozone: Based on the interval between the
FADs or LADs of two different taxa.
• Assemblage Biozone: Characterized by an
association of several fossil species that coexist in a
layer.
• Abundance Biozone: Defined by the abundant
presence of a particular species within a rock layer.
 Stratigraphic Nomenclature
Chronostratigraphic Units

Eonothem Erathem System Series Stage Chronozon

e
Phanerozoic Mesozoic Cretaceous Lower Toarcian Brunhes
Eonothem Erathem Period Jurassic Stage Chronozone
Series
 Stratigraphic Nomenclature
Magnetostratigraphic Unit Sequence Stratigraphic Unit

Magnetozone Sequence

Brunhes Normal
Chron