Dharwar System

 Formation period ranges from 4 billion years ago to – 1 billion years ago.
 Highly metamorphosed sedimentary rock-system. [formed due to metamorphosis of sediments of Archean gneisses
and schists].
 They are the oldest metamorphosed rocks.
 Found in abundance in the Dharwar district of Karnataka.
 Economically the most important rocks because they possess valuable minerals like high-grade iron-ore, manganese,
copper, lead, gold, etc.

Location:

 Dharwar-Bellary-Mysore belt of Karnataka

 Jharkhand, Madhya Pradesh, Chhattisgarh, Odisha etc.
 Himalayan region

Purana Rock System

 Cuddapah and Vindhyan rock systems are together known as the Purana rock system.
 They are formed by the erosion and deposition of Archean and Dharwar rocks
 oldest metamorphosed rocks

Cuddapah System

 They were formed when sedimentary rocks like sandstone, limestone etc., and clay were deposited in synclinal
folds (between two mountain ranges).
 Outcrops best observed in Cuddapah district of Andhra Pradesh.
 These rocks contain ores of iron, manganese, copper, cobalt, nickel, etc.
 They contain large deposits of cement grade limestones.

Vindhyan System (1300-600 million years)

 This system derives its name from the great Vindhyan mountains.
 The system comprises of ancient sedimentary rocks (4000 m thick) superimposed on the Archean base.
 Mostly Unfossiliferous rocks and a large area of this belt is covered by the Deccan trap.
 The Vindhayan system have diamond-bearing regions from which Panna and Golconda diamonds have been mined.
 It is devoid of metalliferous minerals but provides large quantities of durable stones, ornamental stones, limestone,
pure glass making sand, etc.

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 Dravidian Rock System (Palaeozoic)
 Paleozoic rock formation is known as Dravidian systems in India
 The Dravidian period marked the onset of coal formation, particularly the high-quality Carboniferous coal. However,
abundant deposits of these coals are not found in India. These are abundant in fossils and the beginning of coal can
be seen in this period.
 These are found in the Extra Peninsular region and are rarely found in the Peninsular region. The regions of
Anantnag of Kashmir, Spiti, Kangra & Shimla region of Himachal Pradesh, Handwara, Lider Valley, Gharwal &
Kumayun of Uttarakhand, and Pir Panjal are the major regions of Dravidian rocks.
 The Dravidian rocks mainly include shales, sandstones, clays, quartzites, slates, salts, talc, dolomite, marble, etc.
 It marks the beginning of life on the earth’s surface. The rocks of this is the period saw plenty of fossil evidences.

Classification of Dravidian Rock System

1. Cambrian Rocks: They are best developed in the northwest Himalayan region.
2. Ordovician Rocks: These include quartzites, grits, sandstones, etc.
3. Silurian Rocks: These are found in the Lahoul and Spiti Valley. They exist in the form of limes and shales.
4. Devonian Rocks: These are devoid of any fossil fuel remains.
5. Carboniferous Rocks: Mount Everest is composed of Upper Carboniferous limestones.Coal formation started in the
Carboniferous age.

Aryan Rock System

 Period of formation: Upper Carboniferous period to Recent.

 Location: They are found in the Peninsular and Himalayan regions.

The Aryan Group of Rock Formation classified in the following Group:

 Upper Paleozoic Era—- Upper Primary Epoch– Upper Carboniferous & Permian Period formation
 Mesozoic Era-—Secondary Epoch -Triassic, Jurassic & Cretaceous period Formation(Gondwana Rock system, Deccan
trap, Jurassic system)
 Cenozoic Era-—Tertiary Epoch – Paleocene, Eocene, Oligocene-Miocene & Pliocene Period
 Neozoic Era— Quaternary Epoch– Pleistocene & Holocene/recent Period.

Classification of Aryan Rock System:

Gondwana Jurassic Tertiary

Period of Permian period (250 million years between 201.3 million to 60 to 7 million years
formation ago) 145 million years ago
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Features continental origin, fluviatile, and marine transgression in the pivotal role in shaping India’s present
lacustrine deposits laid down in latter part of the Jurassic geographical form. It is called the “Age
synclinal troughs on ancient plateau gave rise to a thick series of of Mammals” because of the
surfaces shallow water deposits in abundance of the fossil remains of
Rajasthan and Kuchchh. these animals in the deposits of this
period.
Location Damodar Valley in Jharkhand, overlay the Triassic system India’s northern plains, in Kashmir’s
Mahanadi River Valley in and cover wide areas in Karewas and the Great Plain. These are
Chhattisgarh and Odisha, parts of Tibet, South Ladakh, Spiti, also found along the coasts of Kachchh,
Madhya Pradesh, etc. Nepal, and Bhutan. Kathiawar, Konkan, Malabar, Nilgiri,
and the Eastern Ghats.
Major Rocks rich deposits of iron ore, copper, Coral limestone, sandstone, Kashmir’s karewas, and the Great
uranium, and antimony. Sandstones, conglomerates, and shales Plains’ Bhangar, and Khadar
slates, and conglomerates are used
as building materials.
Significance contain nearly 98% of India’s coal rock strata laid down during Formation of Himalayas
reserves the Jurassic Period have
yielded gold, coal,
petroleum, and other
natural resources.

The Deccan Trap:

 Period of formation: During the transition from the end of the Cretaceous to the beginning of the Eocene, an
extensive volcanic upheaval occurred across Peninsular India that led to the formation of the Deccan Traps. The
eruption resulted in the discharge of basaltic lava from fissures, covering an expansive region of approximately 10
lakh square kilometers.
 Features: These volcanic deposits are distinct with flat tops and steep sides. They have been named ‘traps’ derived
from the Swedish term which means ‘ stair’ or ‘step.’ The processes of weathering and erosion have significantly
diminished the size of the Deccan Traps, shaping the present geological landscape.
 Major Rocks: The rocks in this region are of basalt type. The weathering of these rocks for a long time has given birth
to black cotton soil known as ‘regur’.
 Location: The current extent of the Deccan Trap spans approximately 5 lakh square kilometers, primarily distributed
across regions such as Kuchchh, Saurashtra, Maharashtra, the Malwa plateau, and northern Karnataka.
The Deccan Trap has been classified into the following groups:

Group Found in Inter-trappean beds Layers of volcanic ash

The Upper Trap Maharashtra and Saurashtra Present Present

The Middle Trap Central India and Malwa Very rare to absent Present

The Lower Trap Present Very rare to absent

Significance: Regur which is black soil was formed due to the weathering of these rocks for a long time. It is an ideal soil
type for cotton in the Penisnular region.

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 Himalayas Formation: Relief & Structure of Himalayas

The Himalayas are the world's highest and youngest mountain range, owe their origin to the theory of plate tectonics.
This immense mountain range began to form between 40 and 50 million years ago, when two large landmasses, India
and Eurasia, driven by plate movement, collided.

 Existence of Pangea and Panthalassa: Around 250 million years ago, there existed
a supercontinent called Pangea (a giant formation of land under which all the continents of the world were
attached together as a monolithic structure). This Pangea was surrounded by a massive water
body called Panthalassa.

Breaking of Pangea: Around 150 million years ago, the supercontinent Pangea began to break into different
parts. First of all, it broke into two parts:

o Laurasia or Angaraland: The northern part of the Pangea was called Angaraland or Laurasia.
 It consisted of landmasses that contained present-day North America, Europe, and Asia.
o Gondwanaland: The southern part of the Pangea was called Gondwanaland.

 It consisted of present-day South America, Africa, South India, Australia, and Antarctica.

 Formation of Tethys Sea: Due to the breaking down of Pangea, a long narrow sea was created between
Angaraland and Gondwanaland, occupying the area where the Himalayas stand today. This sea was known as
the Tethys Sea.
 Deposition of Sediments: During the course of time, huge amounts of sediments were deposited in the bed of
the Tethys Sea by the rivers flowing from Angaraland as well as Gondwanaland.
 Breaking Down of Gondwanaland and Angaraland: The Gondwanaland and Angaraland were further broken
down into different smaller landmasses. The Indo-Australian Plate (comprising present-day Australia and the
Indian Sub-continent) emanated from the Gondwanaland and the Eurasian Plate (containing present-day Europe
and Northern Asia) emanated from the Angaraland.

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 Convergence of Indo-Australian and Eurasian Plates: The convectional currents generated in the Mantle of the
Earth made the Indo-Australian Plate drift northwards towards the Eurasian Plate. This drift continued for
millions of years, leading to the convergence of the two plates across the Tethys Sea.
 Formation of Folds: As the two plates continued to approach each other, the area of the Tethys Sea began to
shrink and the sediments in its seabed were slowly pushed upwards, leading to the formation of folds.
 Genesis of the Himalayas: Eventually, the Tethys Sea vanished completely and sediments rising from its seabed
formed a mountain range, which is now known as the Himalayas.

It is to be noted that the convergence of the two tectonic plates continues to date, leading to the rising of the
Himalayas by about 5 mm per year even now which explains the occurrence of shallow focus earthquakes in the
region today.

Longitudinal Division of Himalayas

 Shiwaliks or outer Himalayas

 Lesser or Middle Himalayas
 The Greater Himalayas
 The Trans-Himalayas – Tibetan Himalayas.
 The Eastern Hills – Purvanchal: A chain of hills in North-East India.

The southern slopes have steep gradients and northern slopes have comparatively gentler slopes.

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