Geological structure of INDIA

1. M R . R A H U L
A S S I S TA N T P R O F E S S O R O F G E O G R A P H Y
S M R J G O V T. P G C O L L E G E , S I WA N I ( B H I WA N I )

2. GEOLOGICAL STRUCTURE OF INDIA
 The geological structure of a country helps in understanding
the types and character of rocks and slopes, the physical and
chemical properties of soils, the availability of minerals, and
the surface and underground water resources.
 But before we can study the geological structure of India, it
is important that we understand what a geological time scale

3. Geological Time Scale

4. GEOLOGICAL HISTORY OF INDIA:
 Major events in the geological history of India:
 Peninsular India was a part of the old landmass since the
formation of the Earth’s Crust
 The upheaval of Himalayas in the tertiary period.
 Aggradational formation of the Indo-Gangetic plain during the
Pleistocene period.
 It continues till today through sedimentation in the floodplains
of the rivers and the lower part of the Gangetic plain.

5. • India is divided into 3 major regions (also
called the Triple Tectonic division):
• The Peninsular Plateau region – It also
includes the Shillong Plateau and the
Kutchch Kathiawar region (Outliers)
• The Extra-peninsular region – the
mountainous region of Himalayas.
• The Indo-Gangetic Plain- between
peninsular and extra-peninsular region.
• In addition to these, there are 2 minor
divisions:
• The Coastal Plains (Eastern and western)
• The Islands (Lakshadweep and Andaman
and Nicobar)
Geological
Divisions
of India:

6. Based on this complex and varied geological history, the
Geological Survey of India has classified rock systems of the
country into 4 major divisions:

8. 1. The Archaean rock system (Early Pre-Cambrian)
• (a). Archaean Gneisses and Schists
These are the oldest rocks and were the first to be formed at the
time of cooling and solidification of the upper crust of the earth’s
surface in the pre-cambrian era.
The rocks are primarily gneisses and granites, having no marks of
fossils.
The system is generally known as the basement complex or
fundamental gneisses.
This is the rock which mineral composition may vary from granite
to gabro.

9. The central and the southern part of
the Peninsula are occupied by this
rock system. To the north-east of the
peninsula, they occupy wide areas in
Orissa, Meghalaya, Madhya
Pradesh, Chhatishgarh, Chotanagpur
plateau of Jharkhand and the whole
of Bundelkhand.
They also occur in roots of the
mountain peaks all along the
Himalayas, forming the bulk of the
high ranges and the bacbone of the
mountain system.
DISTRIBUTION OF ARCHAEAN ROCKS

10. • (b). Dharwar Rocks
• These rocks are formed by erosion and depostion of primary
Archaean rocks.
• First metamorphosed sedimentary rocks in Indian Geological Time
scale.
• No fossils are found in these rocks.
 This system derives its name from the rocks first studied in the
Dharwar district of Karnataka where such rocks are found in
abundance.
 The Dharwar rocks are economically the most important rocks
because they possess valuable minerals like high-grade iron ore,
manganese, copper, lead, gold, quartzite, slates, mica, etc.

11.  The Dharwar system is very well
developed in the Dharwar-Bellary-
Mysore belt of Karnataka. It also
occurs in Jharkhand
(Ranchi,Hazaribagh), Madhya Pradesh
(Balaghat,Rewa), Chhatisgarh
(Baster,Dantewara,Kanker), Orissa
(Sundergarh, Keonjhar) and in the
Aravalis between Jaipur and Palanpur.
 In the extra-Peninsular region, the
Dharwar system is well represented in
the Himalayas both in the central and
northern zones as well as in the
Meghalaya plateau.
DISTRIBUTION OF DHARWAR ROCKS

12. 2. The Purana Rock System (Late Pre-cambrian):
 In India, the word purana has been used in place of Proterozoic and
includes two divisions: (a). Cuddapah system (b). Vindhyan system
 (a). The Cuddapah System:
 These rocks are formed after the erosional and depostional process of
dharwar system.
 These rocks are also metamorphic sedimentary rocks.
 No fossils are found in these rocks.
 These formations, named after the Cuddapah district in Andhra Pradesh are
sedimentary metamorphic formations.
 The economic significance of the Cuddapah system lies in the fact that
these rocks contain ores of iron, manganese, copper, cobalt, nickel, jasper
and asbestos. They also contain large deposits of building purpose
quartzites and cement grade limestones.
 The metallic content in ores of Cuddapah rocks is low and at places
uneconomical for extraction.

13.  These are found in Andhra
Pradesh, southern
Chhattisgarh, Odisha and
along the main axis of
Aravallis.
DISTRIBUTION OF CUDDAPAH ROCKS

14. (b). The Vindhyan System:
 This system derives its name from the Vindhyan mountains.
 Rocks of this system are formed after the Cuddapah system.
 Consists of enormous sedimentary deposits. In some tracts,
Vindhyan rocks are buried under the Deccan lava.
 Fossils are found in these rocks.
 The well-known diamond mines of Panna (Madhya Pradesh)and
Golconda (Karnataka) lie in the Vindhayan system rocks.
 This rock system is well known for red sandstone, sandstone,
durable stones, ornamental stones, raw materials for lime, glass,
cement and chemical industries.

15.  It stretches from Sasaram in
Bihar to Chittorgarh in
Rajasthan with the exception
of the central tract of
Bundelkhand gneiss.
 These rocks are also found in
southern Chhattisgarh,
Bhima valley of Karnataka
and Kurnool districts of
Andhra Pradesh.
DISTRIBUTION OF VINDHYAN ROCKS

16. 3. The Dravidian Rock system (Cambrian to Carboniferous)
 The rocks of the Dravidian system came into being about 600-
300 million years ago.
 These rocks are mostly found in the extra-Peninsular regions of
the Himalayas and the Gangetic plain except small patches.
 They contain abundant fossils in them
 Coal formation started in the Carboniferous age. Carboniferous
in geology means coal-bearing.
 The rocks of Cambrian, Ordovician, Silurian, Devonian and
Carboniferous periods are included in the Dravidian System.

17. 4. The Aryan Rock system
 The Aryan rock system comprises the rock formation ranging
from the upper Carboniferous to recent.
 (a) Gondwana System (b). The Decan Trap
 (c) Tertiary System (d). Quarternary Formations

18. (a). The Gondwana System
 This system derives its name from the Gond region of Madhya
Pradesh also where these rocks were first discovered.
 The peninsula during the Upper Carboniferous period experienced
crustal movements, which led to the formation of basin-shaped
depressions.
 These depressions had countless terrestrial plants and animals,
which were buried to from coal deposits in India known as the
Gondwana Rocks.
 Economically, the Gondwana rocks are the most important in India
contaning about 98 percent of her coal reserves. They have rich
deposits of iron ore, copper and uranium. Sandstones, slates and
conglomerates are used as building materials.

19.  These Rocks are found
mainly along the Damodar
valley in Jharkhand, along
the Mahanadi river valley
in Chhatisgarh and Orissa,
in the southern part of
Madhya Pradesh and the
Godavari valleys of the
peninsula.
DISTRIBUTION OF GONDWANA ROCKS

20. (b). The Deccan Trap:
 Towards the end of the Mesozoic era, intensive volcanic activity
took place, which flooded with lava vast areas of Maharashtra
and other parts of the Deccan known as the Deccan traps.
 The volcanic rocks contain some thin fossil ferrous sedimentary
layers found between the lava flows. This indicates that the lava
flows was not continuous. The volcanic activity led to two great
events. 1.Breakup of the Gondwana landmass
2. Uplift of the Himalayas out of the Tethys Sea.
 The weathering of these rocks for a long time has given birth to
black cotton soil known as ‘regur’.

21.  Deccan Trap covers about
5 lakh sq km mainly in
parts of Kuchchh,
Saurashtra, Maharashtra,
the Malwa plateau and
northern Karnataka.
DISTRIBUTION OF DECAN TRAP

22. (c). Tertiary System
Eocene to Pliocene about 60 to 7
million years ago.
The tertiary is the most significant
period in India’s geological history
because the Himalayas were born
and India’s present form came into
being in this period.
The Tertiary has been called the
age of the Mammals because of the
abundance of the fossils remains of
these animals in the deposits of this
period.

23. (d). The Pleistocene and recent
formations (The quaternary
period)
Quaternary is the name proposed
for very recent deposits, which
contains fossils of species with
living representatives
These include Satluj-Ganga-
Brahmaputra plains and Karewa
formations of the Kashmir valley.