Principles of Stratigraphy (STRATIGRAPHY- U1 L1) #STRATIGRAPHY #GATE #JAM #CSIR #NET #GEOLOGY
Summary
TLDRThis educational video script introduces the principles and history of stratigraphy, the study of layered rocks and their geological history. It covers the foundational concepts such as superposition, original horizontality, and lateral continuity, as well as the evolution of stratigraphy with the introduction of new branches like seismic and magnetic stratigraphy. The script also highlights the importance of fossils in dating strata and the influence of both gradual processes and catastrophic events in shaping Earth's history.
Takeaways
- 📚 Stratigraphy is the study of stratified rock layers, including their classification, interpretation, and correlation in time and space to interpret Earth's geological history.
- 🌐 The term 'stratigraphy' was coined by French geologist Dr. Bigni in 1849, combining 'stratum' and the Greek word 'graphia' for description.
- 🏞 Traditional branches of stratigraphy include lithostratigraphy, biostratigraphy, and chronostratigraphy, focusing on lithological characters, fossil content, and time of formation, respectively.
- 🔍 In the 1960s, seismic and magnetic stratigraphy emerged, using seismic reflection data and earth's magnetic reversal records for sediment and rock analysis.
- 🌊 Sequence stratigraphy examines the relationship between sedimentation and sea-level changes, while higher-resolution stratigraphy includes event stratigraphy, cyclostratigraphy, and chemostratigraphy.
- 🏗 The foundation of stratigraphy was laid by Nicolas Stino, who proposed the laws of superposition and introduced principles of initial horizontality and lateral continuity.
- 📈 William Smith introduced the concept of layering in sedimentary rocks and published the first geological map of Great Britain, contributing significantly to the field.
- 🔬 Stratigraphy has evolved with the use of radiometric and magnetostratigraphic dating techniques, chemical indicators, and isotopes, enhancing its methods and applications.
- 📝 Basic principles of stratigraphy include the order of superposition, original horizontality, lateral continuity, cross-cutting relationships, principles of inclusion, unconformities, fossil successions, and the concepts of uniformitarianism and catastrophism.
- 🌱 Fossil succession, based on the evolution of organisms, allows for the correlation of rocks from different areas, reflecting the historical evolution of life on Earth.
- 🔄 Uniformitarianism, as proposed by James Hutton, suggests that processes operating today were the same in the past, guiding the understanding of Earth's historical evolution.
Q & A
What is the definition of stratigraphy according to the video?
-Stratigraphy is the study of stratified rocks, which are deposited layer by layer. It includes the classification, interpretation, and correlation of these rocks in time and space to interpret the geological history of the Earth.
Who is credited with coining the term 'stratigraphy'?
-The term 'stratigraphy' was coined by French geologist Dr. Bigsby in 1849.
What are the two components of the word 'stratigraphy' and what do they signify?
-The word 'stratigraphy' is a combination of 'stratum' and the Greek word 'graphia'. 'Stratum' refers to layers of rock, and 'graphia' means description, thus, stratigraphy refers to the description of rock layers forming the Earth's crust.
What are the three traditional branches of stratigraphy mentioned in the video?
-The three traditional branches of stratigraphy are lithostratigraphy, biostratigraphy, and chronostratigraphy. Lithostratigraphy focuses on lithological characteristics, biostratigraphy on fossil content, and chronostratigraphy on the time of formation.
What are the two new branches of stratigraphy that emerged in the 1960s?
-The two new branches of stratigraphy that emerged in the 1960s are seismic stratigraphy and magnetic stratigraphy. Seismic stratigraphy uses seismic reflection data, while magnetic stratigraphy uses earth's magnetic reversal records.
What is the significance of the principle of superposition in stratigraphy?
-The principle of superposition states that in an undeformed sedimentary sequence, the beds are younger as we go from bottom to top. It is fundamental to determining the relative ages of rock layers in stratigraphy.
What does the principle of original horizontality suggest about sedimentary rock deposition?
-The principle of original horizontality suggests that sediments are deposited in a horizontal manner, regardless of the current orientation of the rock. Any tilting or folding occurs after deposition and consolidation.
Can you explain the principle of lateral continuity in the context of sedimentary rocks?
-The principle of lateral continuity states that sediments deposit in a laterally continuous manner unless the edge of the basin is encountered or sediment supply is insufficient. This principle is crucial for tracing and mapping rock layers.
What is the principle of inclusions in stratigraphy, and why is it significant?
-The principle of inclusions states that inclusions, which are fragments of older rocks within sedimentary rocks, are older than the rock in which they are found. This principle is significant for understanding the relative ages of different rock components.
What is the concept of unconformity in stratigraphy, and how does it relate to breaks in sedimentation?
-An unconformity is a surface of erosion and non-deposition that represents a break in sedimentation. It can indicate a period where no sedimentation occurred, possibly due to the filling of a basin, uplift, or lack of sediment supply. Unconformities can be identified by evidence of erosion or changes in the angle of inclination of the beds.
What does the principle of fossil succession imply about the correlation of rock layers?
-The principle of fossil succession implies that the type and species of fossils found in rock layers change over time, reflecting evolutionary processes. By analyzing the fossil content, rock layers can be correlated with those in other areas, providing insights into their relative ages.
What is the concept of uniformitarianism, and how does it relate to the study of Earth's history?
-Uniformitarianism is the concept that the processes operating on Earth today, such as sedimentation and erosion, have been the same throughout geological history. This principle guides the understanding of Earth's historical evolution, suggesting that the study of present-day processes is key to understanding the past.
How does the video describe the evolution of stratigraphy over time?
-The video describes the evolution of stratigraphy through a series of discoveries and observations, starting with the foundational work of Nicolas Stino, who proposed the laws of superposition. It also mentions the contributions of William Smith, who introduced the concept of layering in sedimentary rocks, and Charles Lyell, who elaborated on uniformitarianism. The video highlights the modern advancements in stratigraphy, including radiometric and magnetostratigraphic dating techniques and the use of chemical indicators and isotopes.
Outlines
📚 Introduction to Stratigraphy
This paragraph introduces the topic of stratigraphy, a branch of geology that studies layered rocks and their sequences. It discusses the historical development of stratigraphy, starting with the term's coinage by French geologist Dr. Bigni in 1849. The paragraph outlines the lecture series' content, which includes the principles of stratigraphy, stratigraphic contacts, unconformities, and data collection methods. It emphasizes the importance of stratigraphy in interpreting the geological history of the Earth, including the classification, interpretation, and correlation of stratified rocks in time and space.
🌐 Principles and Branches of Stratigraphy
This paragraph delves into the fundamental principles of stratigraphy, such as the order of superposition, original horizontality, and lateral continuity. It also covers the various branches of stratigraphy, including lithostratigraphy, biostratigraphy, chronostratigraphy, seismic stratigraphy, and magnetic stratigraphy. The paragraph explains how these branches contribute to the understanding of sedimentary and igneous rock relationships and the geological time scale. It also touches on the historical figures who contributed to the development of stratigraphy, such as Nicolas Stino, John Clare, and William Smith.
🔍 Detailed Principles of Stratigraphy
This paragraph provides a detailed examination of the principles that govern stratigraphic studies. It explains the concept of cross-cutting relationships, the principle of inclusions, and the occurrence of unconformities. The paragraph also discusses the significance of fossil successions in correlating rock layers and the impact of uniformitarianism and catastrophism on the understanding of Earth's history. It highlights how these principles help geologists interpret the depositional environment and the chronological sequence of rock layers.
🚀 Modern Developments and Future Lectures
The final paragraph summarizes the modern developments in stratigraphy, including radiometric dating, magnetostratigraphy, and the use of chemical indicators and isotopes. It mentions the establishment of the International Sub-Commission on Stratigraphic Classification for standardizing stratigraphic approaches. The paragraph concludes by previewing the next lecture in the series, which will focus on stratigraphic contacts and field data collection. It also invites viewers to like, share, subscribe, and join the GATE batch for further studies.
Mindmap
Keywords
💡Stratigraphy
💡Stratigraphic Contacts
💡Unconformities
💡Lithostratigraphy
💡Biostratigraphy
💡Chronostratigraphy
💡Seismic Stratigraphy
💡Magnetostratigraphy
💡Sequence Stratigraphy
💡Uniformitarianism
💡Catastrophism
Highlights
Stratigraphy is the study of stratified rocks, including their classification, interpretation, and correlation in time and space to interpret the geological history of the Earth.
The term 'stratigraphy' was coined by French geologist Dr. Bigni in 1849, combining 'stratum' and the Greek 'graphia', meaning description.
Stratigraphy primarily deals with sedimentary rocks but also includes layered igneous rocks like lava flows and the relationship of intrusive igneous rocks with sediments.
Three traditional branches of stratigraphy are lithostratigraphy, biostratigraphy, and chronostratigraphy, each focusing on different aspects of rock classification and correlation.
Seismic and magnetic stratigraphy emerged in the 1960s, utilizing seismic reflection data and earth's magnetic reversal records for rock interpretation.
Sequence stratigraphy examines the relationship between sedimentation and sea-level changes, while higher-resolution stratigraphy includes event stratigraphy, cyclostratigraphy, and chemostratigraphy.
Nicolas Steno is considered the father of stratigraphy, laying the foundation with the laws of superposition and principles of initial horizontality and lateral continuity in 1669.
William Smith introduced the concept of layering in sedimentary rocks and published the first geological map of Great Britain.
Stratigraphy has evolved with the advent of radiometric and magnetostratigraphic dating techniques and the use of chemical indicators and isotopes.
The International Union of Geological Sciences established an international sub-commission for stratigraphic classification to standardize approaches and principles.
Stratigraphy is based on principles that govern sedimentation processes, including the order of superposition, original horizontality, and lateral continuity.
The principle of cross-cutting relationships states that a structure cutting through another is younger, indicating the sequence of geological events.
Inclusions in sedimentary rocks, such as clasts or fragments from older rocks, are evidence of the rock's age relative to the included material.
Unconformities represent breaks in sedimentation, marked by surfaces of erosion and non-deposition, indicating significant gaps in geological time.
Fossil successions allow for the correlation of rock layers based on the presence of specific organisms, reflecting evolutionary changes over time.
James Hutton's principle of uniformitarianism suggests that processes observable today have been the same throughout Earth's history, shaping its geological past.
Stratigraphy recognizes both gradual, uniform changes over time and occasional catastrophic events that have shaped Earth's history.
Transcripts
hello and welcome everyone to earth
science assimilate classes in this video
lecture series we will be studying about
the stratigraphy and this lecture
particular deals with the principles of
a stratigraphy now let's see the content
distribution so in lecture one we will
study about the concept and definition
of stratigraphy and its historical
development
and also the basic principles of
stratigraphy in the second lecture we
will study the stratigraphic contacts
and unconformities and we will also
study how to collect the stratigraphic
data
so in simple word is stratigraphy is
study of a stratified drops which is
deposited layer by layer
this includes classification
interpretation and correlation of
stratified rocks in time and space
and that helps us to interpret the
geological history of the earth
the term stratigraphy was coined by
french geologist dr bigni in 1849 the
word stratigraphy is combination of two
words that is stratum
and the greek word graphia
that refers to description of all rock
bodies forming the earth's crust and
their organization into distinctive
useful and mappable units
so now let us discuss the basic concepts
definition and historical development of
its photography the stratified rocks
always display a record of past
geological events
stratigraphy involves the studies
directed towards interpretation of these
events so stratigraphy is a branch of
geology which deals with the study of
these layered rocks their sequences and
their relationship with each other
static graphic studies deals primarily
with the sedimentary rocks but it may
also include layered igneous rocks like
lava flows it also involves the
relationship of intrusive igneous rocks
with respect to the sediments
branches of stratigraphy
traditionally up to 1960 there were
three branches which are most popular
that were lithostratigraphy
biostratigraphy and chronosterography
the lithostatigraphy involved
the subdivision correlation and
interpretation of sediments and rocks on
the basis of their lithological
characters
whereas the bio stratigraphic with the
recognition sub division and correlation
and interpretation of sediments and
sedimentary rocks
on the basis of their fossil content and
in chronostratigraphy
we do the recognitions of division and
correlation
also the interpretation of sediments and
sedimentary rocks on the basis of their
time of formation
during 60s
two new branches of stratigraphy came
into existence
so these were the seismic stratigraphy
the one which involves recognition
subdivision correlation and
interpretation of sediments and rocks on
the basis of seismic reflection data the
another was magnetic stratigraphy
this involves the recognition
subdivision correlation and
interpretation of sediments and rocks on
the basis of earth's magnetic reversal
records
stored within the iron bearing minerals
and sediments
the sequence stratigraphy
involves actually the relationship
between the sedimentation
and sea level changes
apart from that
higher resolution stratigraphy also
gained popularity it includes the event
stratigraphy which is based on the
marker events or advanced horizon
cyclostratigraphy this is based on short
period high frequency sedimentary cycles
and chemo stratigraphy that is based on
the study of stable isotope ratios of
the sediments and sedimentary rocks
historical developments in stratigraphy
stratigraphy reach the modern level of
development through a series of
discoveries and observations made from
time to time the foundation was laid by
nicolas stino who is regarded as father
of stratigraphy it was justino who
proposed the laws of superposition and
also introduced the principles of
initial horizontality and lateral
continuity in 1669
thereby laying down the basis of a
stratigraphy as a science
while john claire popularized the
hutton's principles of uniformitarianism
it was william smith who first proposed
the concept of layering in the
sedimentary rocks he also introduced
veterans strata to denote these layers
thus giving the name to the science of
stratigraphy
that is derived from this particular
term
smith also published the first
geological map of the great britain
almost simultaneously the concept of
layering in the sedimentary rocks and
significance of different fossils for
the dating strata were elaborated in
france by eric gender ground yard
it was charles loyal who published the
book principles of geology when he
elaborated the principles on
uniformitarianism
and also defined the significance of
stratigraphic sequences
in recent years stratigraphy has evolved
considerably with the dating of rocks
through radiometric and
magnetostratigraphic techniques
use of chemical indicators and isotopes
has also revolutionized the method and
applications in stratigraphic studies
for the purpose of uniformity
of
approach an international sub-commission
on a stratigraphic classification has
been established by the international
union of geological sciences which lays
down the applications and principles
from time to time depending upon new
finding and discoveries
now we will look to the basic principles
of a stratigraphy because stratigraphy
is based on set of principles that
govern the processes of sedimentation
the sedimentation is a result of
accumulation of rock material carried by
different agencies like water wind
glacier and deposition in basin
the mechanism of sedimentation and
accumulation of other stratified rocks
like lava flows determines the
principles of stratigraphic studies so
let's look at the principles of a
stratigraphy this includes order of
superposition
original horizontality principle of
lateral continuity cross-cutting
relationships principles of inclusion
principle of unconformities fossil
successions and lastly
uniformitarianism and catastrophism
it is obvious that when sediments get
deposited in a basin
they go down to the bottom layer by
layer
the bottom most layer is thus first to
deposit this process continues
throughout the course of deposition as
more and more sediments are deposited in
the subsequent layers thus in a
sedimentary sequence the beds or layers
at the bottom are deposited first hence
they are the oldest
the beds overlying them are younger
accordingly in a sedimentary basin it is
possible to determine that which are the
older beds and which are the younger
beds
this principle states that in
undeformed sedimentary sequence the beds
are younger and younger as we go from
bottom to top this principle is known as
order of superposition that constitutes
the basics of principles of stratigraphy
the sedimentary rock occurs in all
orientations
like horizontal
tipping at various angles or maybe even
folded it is obvious they could not have
been deposited in that condition
of tilting or folding
sediments in the basin are always
deposited in a horizontal manner
irrespective of the shape of the base
the tilting and folding are the
structural changes that takes place
after the rocks are deposited and
consolidated so for the study of rocks
you have to visualize the nature
in
their present deposition but assuming
that they were deposited versionally in
a horizontal fashion and this is known
as principle of original horizontality
in basin sediments are spread in all the
directions during the course of
deposition
but when traced
they show lateral continuity
because they deposit horizontally as
well as in laterally continuous manner
when we study sediments we often find
that in a valley deposits cannot be seen
as we can see over here in the diagram
but they are exposed again across the
belly
as we can see
from
this diagram
this is because subsequent erosion along
the valley has removed these sediments
but originally they were deposited in
continuity
which extends up to the limits of the
basin
so
the sediments are deposited in a
laterally continuous manner unless the
edge of the basin is encountered or
sediment supply insufficient
cross-cutting relationship principle the
structure which cuts his younger and the
one which gets cut is older
the basic principle of cross-cutting
relationship is when something cuts
across a sedimentary sequence
it is always younger than the sequence
in other words
all cross cutting features are produced
after the sediment is deposited
the cross cutting feature may be a
structural feature like a fault as we
can see in this diagram or it means
intrusion like a dike as we can see in
this diagram it could also be a feature
of erosion like a valley or break and
deposition all of the changes are
brought about after deposition of
sediment has taken place
sedimentary rocks are often made up of
clasts or fragments of older rocks they
are carried by river water
or by any other medium and deposited in
a basin
after deposition these clasts get
consolidated into rock these glass
changes science from very fine silt to
fragments of gravel and can be termed as
inclusions in the sedimentary rocks
in lava flows
there can also be some inclusions
and they are known as genomics
as we can see in the diagram the
principle of inclusion is that that they
are older than the rock in which they
are deposited
it is obvious
that because they are derived
from denude
or pre-existing rocks that's why the
inclusions are always older means the
rock
which contains inclusion is younger than
the inclusion
and the inclusions are older
when sediments are deposited
continuously they constitute a
sedimentary sequence
and this type of continuous deposition
is known as confirmable deposition very
often it happens that there is a break
in sedimentation and then it creates a
surface of erosion and non-deposition
and this surface is called unconformity
the break in sedimentation can take
place due to non-availability of
sediment or to the filling of of the
basin alternatively the basin may be
uplifted and hence
there is no sedimentation
this break may last for a brief period
of time or for longer period of time in
former case it is difficult to locate on
unconformity
but if this break is longer than the
unconformity can be located by evidences
of erosion or changes in the angle of
inclination of the beds
most sedimentary rocks bear fossils that
are remains of organisms of the
past but the type and species of
organisms that keeps changing from time
to time
and we know that mostly the evolution is
prevailed in nature as a result if we
analyze the rocks of the past they get
some insane organisms and if we are keep
on analyzing the rocks of younger and
younger sequences we get the fossils of
more evolved organisms as we can see
from this diagram that in gambrian we
have shielded
like organisms these are the fishes
which appeared around cambrian toward
vision time and humans appeared around
tertiary quaternary base
so if we are analyzing the rocks on the
basis of presence of their fossil
content they can be correlated from the
rocks of another area as well
we find
no vestige of beginning no prospect
these were the personal statement by
james hutton
this
states that processes which are
operating today
at present on the earth like
sedimentation and erosion
they were same in the past as well
these processes over prolonged period of
time were responsible for changes that
had taken place on the earth
the guiding maximum for understanding
the historical evolution of earth under
this principle as proposed by james
hutton is
study your present is key to the past
it is worth mentioning
that the intensity of these processes
have changed over time for example the
paleocene using period was the period of
thermal maximum and if we see the
blistocene time
this was the period of global wholly so
definitely because of the changing
processes these climatic changes also
brought about
the uniformitarianism as we know is a
slow process and takes these brings
above changes over a prolonged period of
time however we have also noticed that
there are some changes on the earth
which takes place suddenly through some
catastrophic events so catastrophic
events are also important together with
the
uniformitarianism so earth history is
consists of longer period of gradual and
uniform changes but it is followed by
occasional sort catastrophic events
so in a stratigraphy lecture one we have
studied about the stratigraphy its
historical development and fundamental
concepts of stratigraphy
in the next coming lecture we will study
about stratigraphic contacts and also
the collection of data or collection of
stratigraphic data from the field
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