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Geology
GEOLOGY
Subject
:
GEOLOGY
(For under graduate student.)
Paper No.
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Paper – 02
Introduction to Geology – 02
Topic No. & Title
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64
Different Geological Formations Of
India (Part – 02)
Frequently Asked Questions
FAQ’s
Q: How will you classify the geographical area of India?
ANS: The deposits of minerals as well as the fossil records found in the
Indian sub- continent are quite impressive. The geographical area of
India can be categorized as:
(a) Deccan trap
(b) Gondwana
(c) Vindhyan
The Deccan trap spreading over most of Maharashtra, as well as parts of
Gujarat, marginally Andhra Pradesh, Madhya Pradesh and Karnataka, is
believed to be formed from sub- aerial volcanic eruptions linked with the
continental deviation during the Mesozoic Era. The rocks in this era are
igneous in nature.
After getting detached from the remaining Gondwana, the Indian Plate,
during its journey to the north, crossed the reunion hotspot, causing
extensive melting beneath the Indian Craton, which broke through the
craton surface in a flood basalt event, this lead to the Deccan Trap. India
was separated from Madagascar by the Reunion hotspot.
The Vindhyan and the Gondwana include parts of Madhya Pradesh,
Uttarakhand, Rajasthan, Himachal Pradesh, Punjab, Jammu and
Kashmir, Maharashtra, Andhra Pradesh, West Bengal, Jharkhand, Bihar,
Odisha and Chhattisgarh within their folds. The fluviatile rocks of the
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Permo-Carboniferous time are in a sequence formed by the Gondwana
Super-group. The depository of Gondwana rocks in the eastern parts of
India are Rajmahal hills and valleys of Sone and Damodar. Maharashtra,
Andhra Pradesh, West Bengal, Jharkhand, Bihar, Odisha and
Chhattisgarh within their folds. The fluviatile rocks of the PermoCarboniferous time are in a sequence formed by the Gondwana Supergroup. The depository of Gondwana rocks in the eastern parts of India
are Rajmahal hills and valleys of Sone and Damodar.
Maharashtra, Andhra Pradesh, West Bengal, Jharkhand, Bihar, Odisha
and Chhattisgarh within their folds. The fluviatile rocks of the PermoCarboniferous time are in a sequence formed by the Gondwana Supergroup. The depository of Gondwana rocks in the eastern parts of India
are Rajmahal hills and valleys of Sone and Damodar.
Q: What does the Pre – Cambrian era encompass?
ANS: Pre – Cambrian era encompasses a large time span in the history
of the planet Earth and dates back to the formation of Earth about 4600
million years ago (Ma) till the beginning of the Cambrian period of around
540 Ma. The last part of this era marked abundance in the appearance of
macroscopic hard-shelled animals on Earth. This period it accounts for
about 88% of the Earth’s geologic time. Human beings have been able to
learn and unearth very little data from this period and there has also been
a poor fossil record to substantiate the learning curve. The middle part of
this era saw the evaluation of the fauna forms. Towards the end of this
geographical era there was a rapid development of life forms slowly
changing the face of the planet.
Q: Which era is the longest of the Phanerozoic areas?
ANS: Paleozoic Era spans from around 541 to 252 million years ago and
is the longest of the Phanerozoic areas. This era experienced some
dramatic and drastic changes on geological, climatic and evolutionary
fronts. Modern phyla first appeared during this era and there was the
evolution of fish, arthropods, amphibians and reptiles during this time.
Life began its journey from the ocean but gradually transformed into land
life forms during this era. The continents were covered with dense forests
during this time which in the future got transformed into the coal reserves
of Europe and the eastern regions of North America. Towards the later
part of this era, huge reptiles appeared and the first modern plants in the
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form of conifers appeared. This era ended with the greatest mass
extinction event in the history of the planet. Mesozoic era spans from 252
to 66 million years ago and is known as Mesozoic era.
Q: Which era was dominated by the massive reptiles?
ANS: Mesozoic era spans from 252 to 66 million years ago and is known
as the age of reptiles. Massive reptiles dominated the life forms on the
land during this period. This era experienced significant tectonic, climatic
and evolutionary changes. Birds and mammals also first appeared during
this era. The end of this era witnessed another mass extinction event
which completely wiped out several life forms on Earth including the
dinosaurs.
Q: Which era is rightly called as the “age of mammals”?
ANS: Cenozoic is the most recent era and encompasses the timescale
from 66 million years ago till the present time. This age is widely known
as the age of mammals. The end of the Mesozoic era witnessed the
extinction of the large reptiles and with the advent of the Cenozoic era,
which allowed the mammals to evolve and diversify to a large extent.
This period was dominated by smaller fauna and mammals began to
establish their hold on the land and ocean. However, some species of
birds which were huge in size still existed during this time and they were
feared by these smaller mammals. However, the mammals were
considerable larger than the sizes that are found today. The earth started
a dramatic cooling and drying trend on the climatic front and the
continents forms their shapes and positions as is found today.
Q: What are the standard geological eras of the world?
ANS: The standard geological eras of the world are as follows:
- Cambrian era (570 million years)
– 570 years)
– 245 million years)
Q: What is meant by the Dharwar System?
ANS: The Dharwar System derives its name from the Dharwars district in
Karnataka and is inclusive of highly metamorphosed igneous as well as
sedimentary rocks. Granulite, Chlorite and Hornblende are the igneous
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rocks of this system, while different schists like ferruginous quartzites and
quartzites, chlorite-schist, talc-schist and mica-schist are of sedimentary
origin. All these are metalliferous, with ores of gold, lead, copper,
manganese, iron etc.
The rocks of such nature are found in the Dharwar-Bellary-Mysore region
in Karnataka. They are also found in the Aravalli Hills between Palanpur
and Jaipur, in the Jabalpur, Balaghat and Rewa districts of Madhya
Pradesh, Nagpur in Maharashtra, Hazaribagh and Ranchi of Jharkhand,
Keonjhar and Sundargarh districts of Orissa, and Zaskar and Ladakh of
Himachal Pradesh and Jammu & Kashmir.
Q: How will you categorize the Carboniferous rocks?
ANS: The Carboniferous rocks are about 350 million years old. These
rocks are made up of mainly quartzite, shale and limestone. The
Carboniferous rocks can be categorized as
1. Upper Carboniferous rocks
2. Middle Carboniferous rocks
3. Lower Carboniferous rocks
Q: From where does the Gondwana System derive its name?
ANS: The Gondwana System derives its name from the Gonds kingdom
in Andhra Pradesh. These laucustrive and fluviatile deposits are of
continental origin, and occur mainly in Mahanadi valley (Orissa and
Chhattisgarh), Damodar Valley (Jharkhand), Kashmir, Sikkim, Darjeeling
and the south of Madhya Pradesh. These are economically the most
important rocks in India, with 98% of its coal reserves, and rich deposits
of antimony, uranium, copper and iron ore.
Q: Where is the Eocene System found?
ANS: The Eocene System, about 60 mya, is found mainly in Jammu &
Kashmir, Rajasthan, Himachal Pradesh, Gujarat and North-East India,
and comprises lime stones, along with sandstones in Jaintia series in
South and East Meghalaya.
Oligocene and Lower Miocene System is not well-developed in India.
The Tertiary outcrops underwent denudation in this period, leading to
removal rocks of this system. Oligocene rocks are found largely in Barail
series of Assam where lower Miocene rocks with no conformity overlie
them.
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