Dravidian and Aryan Rock Systems of India
Geography › India: Location, Geology and the Himalayas · Topic 13.4
The Dravidian rock system, of Palaeozoic age, about 600 to 300 million years old, is rich in fossils and found mainly in the Himalayas, not in the south. The Aryan system, from the Upper Carboniferous to the present, includes the Gondwana system with about 98 per cent of India's coal, the Jurassic marine deposits, the Deccan Trap lavas, the Tertiary system that raised the Himalayas, and the Quaternary alluvium.
6 min read · UPSC Prelims · Geography · India: Location, Geology and the Himalayas
At a Glance
- Dravidian Palaeozoic, 600 to 300 million years; Himalayas
- Gondwana Since the Permian, about 250 million years; coal
- Deccan Trap End of Cretaceous; basalt; black soil
- Tertiary Birth of the Himalayas
- Quaternary Alluvium of the plains
- Exam link UPSC Prelims, Geography: India: Location, Geology and the Himalayas
Where Does It Fit?
This is the fourth topic of the macro on India’s location, geology and the Himalayas. The previous topic described the Archaean and Purana systems, and this one covers the younger Dravidian and Aryan systems. The next topic begins the study of the Himalayan ranges. Previous topic: Archaean Rock System of India. Next topic: Himalayan Ranges – Shiwaliks, Lesser, Greater and Trans-Himalaya.
What Is the Dravidian Rock System?
In short: the Dravidian system is the group of fossil-rich Palaeozoic rocks, found in the Himalayas and not in Dravidian south India.
The Dravidian system covers the Cambrian, Ordovician, Silurian, Devonian and Carboniferous periods, from about 600 to 300 million years ago. These are sedimentary rocks laid down in the sea, and contain abundant fossils, so they have helped geologists to date the history of the region. They are very rare on the Peninsula, which was land at the time, and are found in the extra-peninsular region, mostly in the Himalaya of Kashmir, Spiti and Kumaon, and in the Salt Range. The Carboniferous rocks, about 350 million years old, are limestone, shale and quartzite. Coal began to form in the Carboniferous period around the world, and the word means coal-bearing, although most Indian coal is much younger, as in Coal – Formation, Classification and Distribution. The summit of Mount Everest is made of marine limestone, which formed on the floor of an ancient sea and was raised by the Himalayan collision; recent geological mapping dates it to the Ordovician period, within the Dravidian span, as in Continent-Continent Convergence – Himalayas and Tibetan Plateau.
What Is the Gondwana System?
- Origin: a thick sequence of sandstones, shales and coal seams laid down since the Permian, about 250 million years ago, in long troughs on the old plateau surface, which sank as sediments built up. Rivers and swamps supported land plants such as the Glossopteris flora. The name comes from the Gond tribes of Telangana and Andhra Pradesh, and the same flora in India, Africa, South America, Antarctica and Australia supported the theory of continental drift, as in Continental Drift Theory of Alfred Wegener.
- Coal: the Gondwana rocks contain about 98 per cent of India’s coal reserves, in the valleys of the Damodar, Son, Mahanadi and Godavari. This coal is younger than the Carboniferous coal of Europe and North America, so its carbon content is lower.
- Other resources: iron ore, copper, uranium, antimony, and sandstones, slates and conglomerates for construction.
The Jurassic rocks are marine deposits of shallow water in Kutch and Rajasthan, such as the coral limestone and sandstone of Kutch and the Jaisalmer limestone used for building. The Rajmahal traps of Jharkhand are an early basaltic eruption of the Jurassic-Cretaceous period.
What Is the Deccan Trap?
| Feature | Detail |
|---|---|
| Age and origin | Fissure eruptions of basaltic lava from the end of the Cretaceous to the early Eocene, about 66 million years ago, as the Indian plate crossed the Reunion hotspot, as in Movement of the Indian Plate |
| Extent | Originally about a million square kilometres; weathering has reduced it to about 500,000 sq km, in Maharashtra, Saurashtra and Kutch, the Malwa plateau, and northern Karnataka |
| Thickness | About 3,000 m in the west, thinning to about 600 to 800 m in the south and 150 m in the east |
| Name | Trap means stairs or step in Swedish, from the stair-step landscape of flat tops and steep sides |
| Soil | Weathering gives the black cotton soil or regur |
| Inter-trappean beds | Layers of sediment that settled between successive lava flows; rich in fossils |
| Groups | Upper trap in Maharashtra and Saurashtra, middle trap in central India and Malwa, and lower trap in Madhya Pradesh |
The Deccan volcanism is also studied for its possible role in the mass extinction at the end of the Cretaceous, in which the dinosaurs died, along with the asteroid impact in Mexico, and scientists still debate their relative parts. The Tertiary system, from the Eocene to the Pliocene, about 60 to 7 million years ago, is the most significant in India’s geological history: the Himalayas were uplifted, the foredeep was formed, and India took its present shape. The Tertiary sediments contain the petroleum of Assam, Gujarat and the western offshore, and lignite at Neyveli. The Quaternary, from the Pleistocene to the Recent, is the age of the alluvium of the Indo-Gangetic plain and of the Kashmir karewas, as in Himalayan Valleys, Snowline and Glaciers. As an analytical point, India’s geology explains why its coal is plentiful but of low grade, why its oil is found mostly in young basins, and why the black soil of the west is so well suited for cotton.
Why Is This Topic Important?
- Facts Gondwana coal and Deccan features asked
- Link Soils and resources
- Concepts Systems named by age
What Came Next?
The next topic begins the study of the Himalayan ranges. Next topic: Himalayan Ranges – Shiwaliks, Lesser, Greater and Trans-Himalaya.
Key People and Terms
- Dravidian system Palaeozoic fossil-rich rocks
- Gondwana system Permian-onward coal-bearing deposits
- Glossopteris Fossil seed fern of Gondwana
- Deccan Trap Basalt lava plateau
- Inter-trappean bed Sediment between lava flows
- Regur Black cotton soil
Exam Corner
Points to Remember
- Dravidian rocks are fossil-rich and in the Himalayas.
- Gondwana has about 98 per cent of India’s coal.
- Deccan Trap: basalt, giving regur.
- Trap means stairs in Swedish.
- Tertiary raised the Himalayas.
Do Not Confuse With
- Dravidian system and Dravidian south A rock name, not a region
- Gondwana coal and Carboniferous coal Younger, lower carbon versus older, higher grade
- Deccan Trap and Gondwana Lava flows versus sediments
Memory Hook
Dravidian fossils in the north, Gondwana coal in the valleys, Deccan lava on top, Tertiary lifts the wall.
Mains Angle
Questions link these systems with resources. These points add depth.
- Coal Gondwana basins
- Soil Basalt gives regur
- Himalaya Tertiary uplift
A Question You May Face
An original practice question, not a past paper question.
“Describe the Gondwana system and the Deccan Trap and bring out their economic significance.”
How to Answer
- Dravidian Palaeozoic Himalayan rocks.
- Gondwana Coal troughs.
- Deccan Trap Basalt and soil.
- Tertiary Himalayas and oil.
GS Relevance
Frequently Asked Questions
What is the Dravidian rock system?
The Dravidian rock system consists of fossil-rich sedimentary rocks of the Palaeozoic era, from the Cambrian to the Carboniferous period, about 600 to 300 million years old. They are found mainly in the Himalayas and not in southern India, so the name does not refer to a region.
What is the Gondwana system?
The Gondwana system is a series of sedimentary rocks laid down in river valley troughs from the Permian period, about 250 million years ago. It contains about 98 per cent of India's coal reserves, along with iron ore, copper and uranium, and fossils of the Glossopteris flora.
What is the Deccan Trap?
The Deccan Trap is a vast area of basalt lava flows, erupted from fissures about 66 million years ago, at the end of the Cretaceous. It covers around 500,000 square kilometres of Maharashtra, Gujarat, Madhya Pradesh and Karnataka, and the weathered basalt forms the black cotton soil.
Why is it called a trap?
The word trap comes from the Swedish word for stairs. The lava flows cooled in horizontal layers, and erosion has formed a stepped landscape with flat tops and steep sides on the plateau, so the lava plateau looks like a staircase.
What are inter-trappean beds?
Inter-trappean beds are layers of sediment, sometimes with volcanic ash and fossils, deposited between two successive lava flows when the volcanic activity paused. They are important for dating the Deccan eruptions and for understanding the climate and life of that time.
PYQ Practice — Statement Analysis
1 Gondwana rocks contain most of India's coal.
About 98 per cent of reserves.
2 Dravidian system rocks are found mainly in South India.
They are found mainly in the Himalayas.
3 The Deccan Trap gives rise to black cotton soil.
Basalt weathers into regur.
4 The Tertiary period saw the formation of the Himalayas.
The collision uplifted the range.
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