1.Introduction 2.Major glacial phases 3.Pleistocene stages 3.Pleistocene glaciation a.Causes b.Effects c.Pleistocene flora fauna , evolutionary megafaunal extinction changes and d.Pleistocene fossils e.Evidences 4.Next glacial period 5.Conclusion 6.Reference

1. Pleistocene Glaciations
BY
NIKSHITA JENA
II SEMESTER
ROLL NO-22GEOL016

2. CONTENTS…
1.Introduction
2.Major glacialphases
3.Pleistocene stages
3.Pleistocene glaciation
a.Causes
b.Effects
c.Pleistocene flora fauna,evolutionary changesand
megafaunalextinction
d.Pleistocene fossils
e.Evidences
4.Next glacialperiod
5.Conclusion
6.Reference

3. INTRODUCTION
Glaciation-A glaciation (Glacial period ) is an interval of time
(thousand of years to million of years) which is marked by colder temp.
and development of ice sheets in the continents (sub polar to sub tropical
climates).
A major glaciation phase consists of a number of glacial and
interglacial periods. Their study and interpretation is of greatest
importance since they are indicators of earth’s history prior to human
evolution, future climate.
Ice ages were first discovered in 1830 by Louis Agassiz in the Swiss Alps
He identified that they had occurred all over Europe.He did this by seeing
that certain areas had similar features.
The Pleistocene glaciation:-
Pleistocene Epoch: 2.58 million to 10,000 years ago
• During the Pleistocene, the earth experienced multiple
periods of glacial-interglacial cycles.

4. Cont...
•The glaciers were enormous, often 2-3 km thick. At their
maximum extent, they covered up to one third of the earth’s
land surface.
•The glaciers were advanced up to the sub tropical regions.
•Glacial periods have left evidence in landscape in terms of
erosional and depositional features
•More than a century ago, geologists determined using such
evidence that at the coldest time of the Pleistocene, glaciers
covered Edinburgh, Scotland; Moscow, Russia; and Detroit
and Chicago in the US.
•From the glacial deposits alone, glaciologists had inferred
several major advances and retreats of the two major ice
sheets, the Laurentide in North America and the Fennoscandian
in Europe and Asia.

5. Major glacial phases
There have been five known
glacial periods in the Earth’s
history
1.Huronian glaciation – Paleoproterozoic
(2500 my-2100my
ago)
2.Cryogenian glaciation- Neoproterozoic
(Snowball earth) (850my-635my ago
)
3.Andean Saharan glaciation- Ordovician and
Silurian
(450-420mya)
4.Karoo glaciation - Carboniferous and
Permian
(360-260mya)
5.Pleistocene glaciation- Neogene
(2.58my-
12500years)
""

6. Last major glaciation- known as the Last Glacial Maximum.
The last glacial maximum was the most recent glacial period
which began about 110000 years ago and ended about
12500 ago.
The glaciation that occurred during this period covered
many areas of the northern hemisphere, ice sheets covered
Chicago, Boston, Detroit, and Cleveland.
It has different names depending upon its geographic
distribution such as Wisconsin in North America, Devensian
in Great Britain, etc.
The glacial advance reached its maximum extent about
18000 BP.
The last glacial maximum(LGM):

7. PLEISTOCENE STAGES
The Pleistocene is subdivided into four ages and their corresponding roc
units:
• the Gelasian (2.6 million to 1.8 million years ago)
• the Calabrian (1.8 million to 774,000 years ago)
• the Chibanian (774,000 to 129,000 years ago)
• Stage 4 (129,000 to 11,700 years ago) Stage 4 awaits naming and ratification by the ICS.

8. Causes of pleistocene glaciation…
The causes of glaciation may be related to several
simultaneously occurring factors, such as:
• Astronomical cycle Feedback mechanism
• Atmospheric composition
• Plate tectonics
• Ocean current
Astronomical cycle(Milankovitch cycle):
Milankovitch cycles deals with the periodic changes in:
1. ECCENTRICITY-Changes from elliptical to more circular –
(Approximately 100000 years)
2.OBLIQUITY- the tilt of the earth’s axis to the plane of the ecliptic.
(period of about 41,000 years)
Tilt changes from 22.1 and 24.5 degrees with respect to
Earth's orbital plane.Currently 23.5 degree.
3. PRECESSION-(wobble on its axis ) gradual shift in the
orientation of Earth's axis of rotation in a cycle of approximately 26,000

9. This factor affects the duration of seasons in both hemisphere.

11. Obliquity and contrast in insolation between the seasons
less contrast
between seasons
more contrast
between seasons

12. Axial Precession
present

13. Atmospheric composition:
Decrease in atmospheric CO2 an important greenhouse gas
started the long term cooling that eventually led to glaciation.
Recent studies of CO2 content in gas bubble preserved in the
Greenland ice cores supports the theory.
CaSiO3+ 2CO2+2H2O= CaCO3+ SiO2+ CO2+ 2H2O
This reaction shows the consumption of CO2 by silicate
weathering.

14. Plate tectonics and oceanic currents:
An important component in long term temp. drop may be related to
the position of continents relative to pole.This controls the oceanic
currents and the heat flow pattern from equator to pole.
Ex. The development of Isthmus of Panama at the convergent plate
margin about 3.5my ago causing the separation of pacific and
Atlantic ocean which further led to development of Gulf stream. Due
to these moistures are carried to the north pole and precipitated as
snow flakes.

15. Feedback mechanisms must operate to amplify the insolation changes caused by the
orbital parameters.
Feedback mechanisms
One of these is- albedo
The reflectivity of Earth’s surface,increased snow cover in high-latitude areas
would cause increased cooling.
Another feedback mechanism is the decreased carbon dioxide content of the
atmosphere during times of glaciation, as recorded in the bubbles
of long ice cores.

16. Effects of pleistocene glaciation:
The presence of so much ice upon the continents had a profound
effect upon almost every aspect of earth’s hydrologic system.
The major effects were that the continental landforms fashioned
both by glacial erosion and deposition and the global sea level fall.
It also affected the oceanic circulation pattern and atmospheric
wind pattern.
The sea level dropped down up to a depth of 130m below from
present level during the LGM and reached the maximum drop
down at 18000BP .

17. C0NT…
• More pronounced temperature changes in the high
latitudes than the low latitudes.
• Temperature changes in high latitude regions are thought
to be about 10oC between glacial and interglacial.
• Abrupt swings in atmospheric circulation with wind belts
such as the Intertropical Convergence Zone (ITCZ) shifting
latitudinally by several degrees.
• Rises and falls of sea level by up to 120 meters and
advances and retreat of the shoreline across the
continental shelves.
• Massive floods of freshwater down rivers such as the St.
Lawrence and Mississippi rivers at times when the ice
melted.
• Northward and southward movements of vegetation belts
across the continent.

18. The dramatic fall in sea
level may be caused due
to following reasons…
1.Laurentide ice sheet in
Hudson bay, North
America.
2.Cordilleran ice sheet in
Rockies mountain,
Canada.
3.Alpine type of glaciers
in Swiss Alps.
4.Increasing thickness of
ice sheets in both poles.

19. axial

20. PLEISTOCENEFLORAFAUNA, EVOLUTIONARYCHANGESAND
MEGAFAUNALEXTINCTION
• Changes in climate and environment caused large-scale migrations of
both plants and animals, evolutionary adaptations, and in some
cases extinction.
• particular importance is the evolution of the genus Homo and the extinction
of large mammals at the end of the epoch.
• Evolutionary changes during the Pleistocene generally were minor because of
the short interval of time involved. They were greatest among the mammals.
• Mammalian evolution included the development of large forms, many of which
became adapted to Arctic conditions. Among these were the woolly mammoth, woolly
rhinoceros, musk ox, moose, reindeer, and others that inhabited the cold periglacial
areas. Large mammals that inhabited the more temperate zones included the elephant,
mastodon, bison, hippopotamus, wild hog, deer, giant beaver, horse, and ground sloth.
• During episodes of glaciation, polar faunas extended south to about 45° N latitude,
whereas during interglaciations these faunas occurred mostly north of 70° and
subtropical faunas extended far to the north under the influence of the Gulf Stream.

21. • The end of the Pleistocene was marked by the extinction of many genera of
large mammals, including mammoths, mastodons, ground sloths.
• The extinction event is most distinct in North America.

22. PLEISTOCENE FOSSILS
paranthropus robustus
fossil
pleistocene peccary fossil
Bison_latifrons_fossil_buffalo_(Pleistocene;_
North_America)

23. Evidences of pleistocene glaciation
I. Glacial deposits :
1.Glacial striations
2. Glacial moraines
3. Till
4. Loess and 5. Drumlins

24. Glacial Erratic
Boulder transported and
deposited by a glacier having a
lithology different than the
bedrock upon which it is placed.
Rouches Moutonnees
Rock hills shaped by the passage of ice to
give a smooth up-ice side and a rough,
plucked and cliffed surface on the down-ice
side. The upstream surface is often marked
with striations.

25. 1. The skeletons of marine
organisms record the
18O content in the water
(sediments)
2. Marine organisms
incorporate 18O
preferentially in cold
water
3. Ice sheets preferentially
incorporate water with
16O, leaving the water
remaining in the ocean
enriched in 18O
4. So the marine
organisms show high
18O/16O ratio during
glacial period.
II. The Oxygen Isotope (18O) Record
Net transfer of 16O from
oceans to ice sheets,
leaving behind ocean
water rich in 18O.

26. It is known that all interglacial periods are not of same duration.
Based on the solar heating and the amount of CO2 in the
atmosphere some calculations of future temp. have been made.
According to these the interglacial period the earth is in now
may persists for another 50000 years if CO2 level increase to
750ppm (present amount398ppm).If it decreases up to 210ppm
then next glacial period may only be 15000 years away.
Next glacial period

27. The ice ages and the inter glacial periods are not uniformly cold or
warm respectively .They are interrupted by no. of interstadials and
stadials respectively.
Stadial- Short span of cold periods within an inter glacial periods.
Interstadial- Short span of warm periods within an glacial period.
Studies of sea floor sediments and ice core indicate that the
climatic change is not smooth. The change from warm to a cold
climate can occur in a decade or two.

28. Conclusion:
• The glacial and interglacial cycles indicate that earth climate is not smooth but dynamic.
• The northern hemisphere glaciation was established around 3mya and the Antarctic ice
sheets were developed around 32mya. These north and south pole development of ice was
due to the opening and closing of ocean continent gateways.
• More than 30% of the land area of the Earth was covered by glacial ice; during the
interglacial stages, probably only about 10% was covered.
• The animals of the Pleistocene began to resemble those of today, and new groups of land
mammals, including humans, appeared. At the end of the epoch, mass extinctions
occurred: in North America more than 30 genera of large mammals became extinct within
a span of roughly 2,000 years.
• The major effects of the glaciations are erosion and deposition of material over large part
of continents, modification of river system, creation of pluvial lakes, abnormal winds ,
change in sea level. Thus we need to understand the dynamic glacial cycles on the Earth
system.

29. Reference:
Living with Earth, An introduction to
Environmental Geology- By Hudson
(2006)
Earth’s climate, past and future by Willium F.
Ruddiman.
https://www.britannica.com/science/Pleisto
cene-Epoch/Megafaunal-extinctions
https://www.e-
education.psu.edu/earth103/node/636
https://slideplayer.com/slide/7556043/
https://www.slideshare.net/fozzie/lesson-1-
history-of-glaciation