Here i share a assignment cover the topics of palaeomegnetism, palaeoclimatology, and ice age's. Here give the information about this topic and the information is very useful for geology students. In this presentation i covered all detail related to this topics. So i hope this presentation if you like and useful for your study. So if you like this presentation you can follow me on slideSher i share useful materials only on slidesher. Darshan Darji Studying msc Geology at M. G science institute

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ASSIGNMENT
OF
Palaeomegnetism,palaeoclimate,ice age
Submitted in partial fulfilment of
The Degree of Master of Science
In Geology
By
Darji Darshan Kumar Rajesh Bhai
Semester: - 1
Roll No: - 3
Paper- Gel 401
Under the supervision of
Dr.m.v. Majethiya
M.g.science institute
(Geology department)
Year:- 2021-22
Navrangpura,Ahmedanad,Gujarat-380009
Content
• Palaeomegnetism
• Principals of remnant magnetism
• Palaeoclimate
• Types of Palaeoclimate

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• Causes of Palaeoclimate Change
• Ice age
• Stages of Ice Age
• Causes of Ice age
• Evidence of Ice age
• Reference
 Paleomagnetism
palaeomagnetism, is the study of the record of the Earth's magnetic field in rocks,
sediment, or archeological materials. Magnetic minerals in rocks can lock-in a
record of the direction and intensity of the magnetic field when they form. This
record provides information on the past behavior of Earth's magnetic field and the
past location of tectonic plates. The record of geomagnetic reversals preserved in

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volcanic and sedimentary rock sequences (magnetostratigraphy) provides a time-
scale that is used as a geochronologic tool. Geophysicists who specialize in
paleomagnetism are called paleomagnetists.
Paleomagnetists led the revival of the continental drift hypothesis and its
transformation into plate tectonics. Apparent polar wander paths provided the first
clear geophysical evidence for continental drift, while marine magnetic anomalies
did the same for seafloor spreading. Paleomagnetic data continues to extend the
history of plate tectonics back in time as it can be used to constrain the ancient
position and movement of continents and continental fragments (terranes).
Paleomagnetism relied heavily on new developments in rock magnetism, which in
turn has provided the foundation for new applications of magnetism. These include
biomagnetism, magnetic fabrics (used as strain indicators in rocks and soils), and
environmental magnetism.
 Paleomagnetic procedure
Collecting samples on land
The oldest rocks on the ocean floor are 200 mya – very young when compared with
the oldestcontinental rocks, which date from 3.8 billion years ago. In orderto collect
paleomagnetic data dating beyond 200 mya, scientists turn to magnetite-bearing
samples on land to reconstruct the Earth's ancient field orientation.

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Paleomagnetists, like many geologists, gravitate towards outcrops becauselayers of
rock are exposed. Road cuts are a convenient man-made source of outcrops.
"And everywhere, in profusion along this half mile of [roadcut], there are small,
neatly cored holes ... appears to be a Hilton for wrens and purple martins."
There are two main goals of sampling:
Retrieve samples with accurate orientations, andReduce statistical uncertainty.One
way to achieve the first goal is to use a rock coring drill that has a pipe tipped with
diamond bits. The drill cuts a cylindrical spacearound somerock. This can be messy
– the drill must be cooled with water, and the result is mud spewing out of the hole.
Into this space is inserted another pipe with compass and inclinometer attached.
These provide the orientations. Before this device is removed, a mark is scratched
on the sample. After the sample is broken off, the mark can beaugmented for clarity.
 Principles of remanent magnetization
The study of paleomagnetism is possible because iron-bearing minerals such as
magnetite may record past directions of the Earth's magnetic field. Magnetic
signatures in rocks can be recorded by several different mechanisms.
1.Thermoremanent magnetization
Iron-titanium oxide minerals in basalt and other igneous rocks may preserve the
direction of the Earth's magnetic field when the rocks cool through the Curie
temperatures of those minerals. The Curie temperature of magnetite, a spinel-group
iron oxide, is about 580 °C, whereas most basalt and gabbro are completely
crystallized at temperatures below 900 °C. Hence, the mineral grains are not rotated
physically to align with the Earth's field, but rather they may record the orientation
of that field. The record so preserved is called a thermoremanent magnetization
(TRM). Because complex oxidation reactions may occuras igneous rocks coolafter
crystallization, the orientations of the Earth's magnetic field are not always
accurately recorded, nor is the record necessarily maintained. Nonetheless, the
record has been preserved well enough in basalts of the ocean crust to have been
critical in the development of theories of sea floor spreading related to plate
tectonics. TRM can also be recorded in pottery kilns, hearths, and burned adobe
buildings. The discipline based on the study of thermoremanent magnetisation in

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archaeological materials is called archaeomagnetic dating. Although the Māori
people ofNew Zealand do notmake pottery, their 700- to 800-year-old steam ovens,
or hangi, provide adequate archaeomagnetic material.
2.Detrital remanent magnetization
In a completely different process, magnetic grains in sediments may align with the
magnetic field during or soon after deposition; this is known as detrital remanent
magnetization (DRM). If the magnetization is acquired as the grains are deposited,
the result is a depositional detrital remanent magnetization (dDRM); if it is acquired
soon after deposition, it is a post-depositional detrital remanent magnetization
(pDRM).
3.Chemical remanent magnetization
See also: Chemical remanent magnetization
In a third process, magnetic grains grow during chemical reactions, and record the
direction of the magnetic field at the time of their formation. The field is said to be
recorded bychemical remanent magnetization (CRM). A common form of chemical
remanent magnetization is held by the mineral hematite, another iron oxide.
Hematite forms through chemical oxidation reactions of other minerals in the rock
including magnetite. Redbeds, clastic sedimentary rocks (suchas sandstones)arered
because of hematite that formed during sedimentary diagenesis. The CRM
signatures in redbeds can be quite useful and they are common targets in
magnetostratigraphy studies.
4.Isothermal remanentmagnetization
Remanence that is acquired at a fixed temperature is called isothermal remanent
magnetization (IRM). Remanence of this sort is not useful for paleomagnetism, but
it can be acquired as a result of lightning strikes. Lightning-induced remanent
magnetization can be distinguished by its high intensity and rapid variation in
direction over scales of centimeters.
IRM is often induced in drill cores bythe magnetic field of the steel corebarrel. This
contaminant is generally parallel to the barrel, and most of it can be removed by
heating up to about 400 ℃or demagnetizing in a small alternating field.

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In the laboratory, IRM is induced by applying fields of various strengths and is used
for many purposes in rock magnetism.
5.Viscous remanent magnetization
Main article: Viscous remanent magnetization.Viscous remanent magnetization is
remanence that is acquired by ferromagnetic materials by sitting in a magnetic field
for some time. In rocks, this remanence is typically aligned in the direction of the
modern-day geomagnetic field. The fraction of a rock’s overall magnetization that
is a viscous remanent magnetization is dependent on the magnetic mineralogy.
 Palaeoclimate
It is a variation of the climate in past geologic times Palaeoclimate is expressed by its
parameters- palaeo-temperature, precipitation in the past, circulation, sea surface
temperature (SST) and sea level.
The state of the earth’s climate depends on the amount of energy the earth receives from
the solar radiation and the amount of energy the earth releases in the form of infrared heat
energy. Climate processes can be divided in two types internal and external.
From abundant geological evidence, we know that only 350 years ago the world was in the
depths of a prolonged cold spell called the “Little Ice Age”, which lingered for nearly 500
years.
During 4.5 to 3.8 billion years ago, in the beginning there was the bang. An exploding star
or supernova, created a cloud of gas and dust from which the solar system formed.
3.8 to 2.5 billion years ago, the first land masses appeared, and life developed in Archean
Era. The oldest fossils date back to about 3.5 billion years ago. The atmosphere was still
toxic, mainly consisting of ammonia and methane.
2.5 billion to 500 million years ago in Proterozoic era atmospheric oxygen levels slowly
started to increase fuelled by photosynthetic algae. This probably wiped out a huge portion
of the Earth’s anaerobic inhabitants, thus the era’s label as the ‘oxygen catastrophe’.
Paleozoic era 500 to 250 million years ago, the planet’s core finally cooleddown to a level
comparable to today. Earth generally saw a lot of glacial activity because the two primary
super-continents, Gondwana and Laurasia, drifted across North and South poles, receiving
little solar energy.

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During the coldest periods, average temperatures were about four to five degrees Celsius
lower than today.
In Holocene Epoch, 12000 years ago to present. The last ice age ended and earth
experienced a warming phase around 12000 years ago. The Western coast of Greenland
began to submerge due to the increasing weight of ice sheets.
 Palaeoclimatology
Palaeoclimatology is the study of past climates. Since it is not possible to go back in time
to see what climates were like, scientists use imprints created during past climates, known
as Palaeoclimate.
Proxy data is data that Palaeoclimatologist gather from natural records of climate
variability, e.g. tree rings, ice core, fossilpollen, ocean sediments, coral and historical data.
 Types of Palaeoclimatology
1. Tree Ring Analysis
2. Pollen Analysis
3. Isotopes
4. Ice Melting, Sea Level Rise

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1.Tree Ring Analysis
Tree ring analysis is also known as dendrochronology.
From the growth of rings or tree rings we can easily predict about the past climate.
There are mainly two types:
1. Floating Chronology
2. Anchored Chronology
2.Pollen Analysis
Pollen analysis is also known as Palynology.
Used for analyzing the plant pollen.
Pollen grains are well pressed and is the sediment layer in
pond lake and oceans.
Pollen analysis is used to study the long-term patterns of vegetation diversity.
3.Isotopes
The elements who have same atomic number but different atomic weight, those elements
are called Isotopes.
Oxygen is one of the most significant elements for Palaeoclimatology research.
Oxygen is having three Isotopes: 16O, 17O, 18O.
Ice Melting and Sea Level Rise

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Sea ice influences climate because it reflects sunlight and influences ocean circulation.
Less sea ice leads to acceleration of global warming.
There is evidence of ice melt, sea level rise to +5-9 m, and extreme storms is the prior
interglacial period that was less than 1°C warmer than today.
Arctic sea-ice cover is shrinking by 8.9% per decade in summer and 2.5% per decade in
winter. It is also becoming thinner and there is less multi-year ice.
Melting sea ice, in combination with melting glaciers and ice sheet, may cause major
change to global patterns of ocean circulation.
As with snow, less sea ice increases absorption of heat from the sun resulting in increased
warming.
 Ice Age
An Ice age is a period of long-term reduction in the temperature of the Earth's surface and
atmosphere, resulting in the presence or expansion of continental and polar ice sheets and
alpine glaciers.
Within a long-term ice age, individual pulses of cold climate are termed ‘Glacial periods’,
and intermittent warm periods are called ‘Interglacials’.
Glaciologically, Ice age implies the presence of extensive ice sheets in the northern and
southern hemispheres.
By this definition, we are in an Interglacial period - the Holocene of the ice age that began
2.6 million years ago at the start of the Pleistocene epoch, because the Greenland, Arctic,
and Antarctic ice sheets still exist.
 Stages of Ice Age
There have been at least five major ice ages in the Earth's past the Huronian, Cryogenian,
Andean-Saharan, Karoo Ice Age and the Quaternary glaciation. Outside these ages, the
Earth seems to have been ice-free even in high latitudes.
Rocks from the earliest well-established ice age, called the Huronian, formed around 2.4
to 2.1 Ga ago during the early Proterozoic Eon.
The next well-documented ice age occurred from 850 to 630 million years ago (the
Cryogenian period) and may have produced a Snowball Earth in which glacial ice sheets

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reached the equator, possibly being ended by the accumulation of greenhouse gases such
as CO 2 produced by volcanoes.
1.Huronian Period
It was a glaciation that extended from 2400 Mya to
2100 Mya, during the Siderian and Rhyacian periods
of the Paleoproterozoic era.
It is the oldestknown ice age, occurring at a time when
only simple, unicellular life existed on Earth.
This geological era was named from geologic findings
in the Lake Huron region in North America where
three separate horizons of glacial deposits are
separated by non-glacial sediment.
2.Cryogenian Period
The Cryogenian (from Greek cryos "cold" and genesis
"birth") is a geologic period that lasted from 850 to 635 million years ago. It forms the
second geologic period of the Neoproterozoic Era, preceded by the Tonian Period and
followed by the Ediacaran.
The Sturtian and Marinoan glaciations, which are the greatest ice ages known to have
occurred on Earth, occurred during this period.
3.Andean- Saharan Period
The Andean-Saharan glaciation was from 460 Mya to 430 Mya, during the late
Ordovician and the Silurian period.
4.karoo Period
The Karoo Ice Age from 360–260 million years ago (Mya) was the second major ice age
of the Phanerozoic Eon.
It is named after the glacial tillsfound in the Karoo region of South Africa, where evidence
for this ice age was first clearly identified.
Northern Hemisphere glaciation during the Last Glacial Maximum. The creation of 3 to 4
km (1.9 to 2.5 mi) thick ice sheets caused a global sea level drop of about 120 m (390 ft.).
5.Quaternary Period

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Quaternary glaciation also known as the Pleistoceneglaciation or the current ice age, refers
to a series of glacial events separated by interglacial events during the Quaternary period
from 2.58 million years ago to present.
During this period, ice sheets were established in Antarctica.
The major effects of the ice age are erosion and deposition of material over large parts of
the continents, modification of river systems, creation of millions of lakes, changes in sea
level, isostatic adjustment of the crust, and abnormal winds.
 Evidences of Ice Age
Geological evidence for ice ages comes in various forms, including rock scouring and
scratching, glacial moraines, drumlins, valley cutting, and the deposition of till or tillites
and glacial erratics.
Successive glaciations tend to distort and erase the geological evidence, making it difficult
to interpret.
Furthermore, this evidence was difficult to date exactly; early theories assumed that the
glacials were short compared to the long interglacial.
The chemical evidence mainly consists of variations in the ratios of isotopes in fossils
present in sediments and sedimentary rocks and ocean sediment cores.
For the most recent glacial periods ice cores provide climate proxies from their ice, and
atmospheric samples from included bubbles of air.
Because water containing heavier isotopes has a higher heat of evaporation, its proportion
decreases with colder conditions.

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This allows a temperature record to be constructed.
The Paleontological evidence consists of changes in the geographical distribution of
fossils.
During a glacial period, cold-adapted organisms spread into lower latitudes.
This evidence is also difficult to interpret because it requires
Sequences of sediments covering a long period of time, over a wide range of latitudes and
which are easily correlated; Ancient organisms which survive for several million years
without change and whose temperature preferences are easily diagnosed, The finding of
the relevant fossils.
Despite the difficulties, analysis of ice core and ocean sediment cores has shown periods
of Glacial and Interglacial over the past few million years.
These also confirm the linkage between ice ages and continental crust phenomena such as
Glacial moraines, drumlins, and glacial erratics.
 Causes of Ice Ages
The causes of ice ages are not fully understood for either the large-scale ice age periods or
the smaller ebb and flow of glacial–interglacial periods within an ice age.
Several factors are important: Atmospheric composition, such as the concentrations of
carbon dioxide and methane changes in the Earth's orbit around the Sun known as
Milankovitch cycles; variations in solar output; and the impact of relatively large
meteorites, and volcanism.
Some of these factors influence each other. For example, changes in Earth's atmospheric
composition may alter the climate, while climate change itself can change the atmospheric
composition.

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References
• Structural Geology, Ravindra Kumar
• Principles of Paleoclimatology, Thomas M. Crocin
• Encyclopedia of Paleoclimatology and Ancient Environments, Vivien Gornitz
• https://www.google.co.in/
• WWW.WIKIPEDIA.COM
• https://www.sciencephoto.com/
• https://www.britannica.com/