These geological structure of India notes for OPSC/UPSC explain how the Indian landmass formed, the sequence of rock systems from Archean to Quaternary, the minerals each system holds, and how the Peninsula, the Himalayas and the plains differ in origin. For OAS prelims the chapter gives direct questions on the age order of systems, coal and iron ore, Deccan Trap and Himalayan ranges, and for mains it supports answers on mineral distribution and plate tectonics, with a strong Odisha connection through iron ore, Gondwana coal and the Eastern Ghats.
Geological History of India: Gondwanaland and Plate Movement
The Indian landmass was once part of the southern supercontinent Gondwanaland, which also included South America, Africa, Australia and Antarctica. Gondwana assembled in the late Neoproterozoic and was the largest continental crust of the Palaeozoic era. It began to break up about 120 million years ago in the Cretaceous. The Indian plate separated and drifted northwards across the Tethys Sea, a movement confirmed by palaeomagnetic studies.
The Indian plate collided with the Eurasian plate about 50 million years ago, and the sediments of the Tethys were folded and raised to form the Himalayas in the Tertiary period. The Ganga plain filled the foredeep in front of the rising mountains.
Three stages to remember: breakup of Gondwana (Cretaceous), northward drift of the Indian plate, and collision with Eurasia (Tertiary) which raised the Himalayas. The Himalayas came from the collision of the Indian and Eurasian plates, not from a three-plate convergence.
IMAGE (Diagram): Breakup of Gondwanaland and northward drift of India
Labels: Gondwanaland, India, Africa, Antarctica, Australia, South America, Tethys Sea, Eurasian plate, Himalayas
Caption: India separated from Gondwanaland and drifted north to collide with Asia.
Find it: NCERT Class 11 Fundamentals of Physical Geography Chapter 4, Wikimedia Commons 'Indian plate movement'
Rock Systems of India: Geological Time Scale and Sequence
Indian geologists classify rocks into systems, broadly in the order set out below. This sequence is a frequent exam question.
| System | Age | Main character |
|---|---|---|
| Archean | Pre-Cambrian, oldest | Granite and gneiss; azoic |
| Dharwar | Pre-Cambrian | First sedimentary system; metamorphosed; rich in metals |
| Cuddapah (Purana) | Pre-Cambrian | Slates, quartzites, limestone |
| Vindhyan (Purana) | Pre-Cambrian to Cambrian | Sandstone, limestone, shale; building stone |
| Palaeozoic (Dravidian) | Cambrian to Carboniferous | Marine rocks in Spiti, Kashmir, Salt Range |
| Gondwana | Carboniferous to Jurassic | Coal, sandstone, shale |
| Deccan Trap | Cretaceous to Eocene | Basalt lava |
| Tertiary | Palaeocene to Pliocene | Himalayan folding; oil, Assam coal |
| Quaternary | Pleistocene to present | Alluvium, karewas |
Use the mnemonic D-C-V-G for the old systems: Dharwar, Cuddapah, Vindhyan, Gondwana, from oldest to youngest. Questions ask for the oldest, the youngest, or a wrong sequence.
Archean Rock System
Archean rocks, also called the Primary or Pre-Cambrian rocks, are the oldest rocks of the earth's crust. They are crystalline igneous and metamorphic rocks such as granite and gneiss, and contain no fossils (azoic) and no coal. They form the base of the Peninsula and cover large parts of Karnataka, Tamil Nadu, Odisha, Chota Nagpur and the Aravallis. The Chota Nagpur Plateau is mainly Archean granite and gneiss, while Tamil Nadu holds some of the oldest rocks of the world.
- Archean rocks have no coal; coal is in the Gondwana system.
- The Dharwar system is younger than the Archean system, not older.
Dharwar System
Named after Dharwar in Karnataka, but found also in the Aravallis, Chota Nagpur, Meghalaya and the Himalayas. It is the first sedimentary system and the main storehouse of metallic minerals: iron ore (haematite and magnetite), manganese, copper, lead, gold and silver. The best iron ore of India, including the Keonjhar, Sundargarh and Mayurbhanj belt in Odisha and the Bababudan hills in Karnataka, belongs to this age.
Cuddapah System
Named after Cuddapah district in Andhra Pradesh. Its rocks include slate, quartzite and limestone. The Cuddapah rocks form much of the southern Eastern Ghats, such as the Nallamala and Velikonda ranges (Velikonda lies in Andhra Pradesh). The Papagni and Champaner series belong here, while the Semri series belongs to the Vindhyan system.
Vindhyan System
The Vindhyan system stretches from Chittorgarh in Rajasthan to Sasaram in Bihar. It consists of sandstone, limestone and shale and is valued for building stone, as at the Red Fort and Sanchi, and for cement limestone and diamonds (Panna). It has no coal.
IMAGE (Map): Distribution of rock systems of India
Labels: Archean (Peninsular core), Dharwar, Cuddapah, Vindhyan, Gondwana coal belts, Deccan Trap, Tertiary (Himalaya, Assam), Quaternary (Indo-Gangetic plain)
Caption: Major rock systems of India.
Find it: NCERT Class 11 India Physical Environment Chapter 2; Geological Survey of India map
Palaeozoic (Dravidian) System
The Palaeozoic formations in India are known as the Dravidian system. They include Cambrian, Ordovician, Silurian, Devonian and Carboniferous rocks, mainly shales, sandstones and quartzites, found in the Spiti valley, Kashmir and the Salt Range.
Gondwana System: India's Coal Belt
The Gondwana system, formed from Carboniferous to Jurassic times, is the youngest of the old systems and the most economically important. It holds over 90 per cent of India's coal. The rocks were deposited in river basins and rift valleys, and most coal fields lie in the valleys of the Damodar, Son, Mahanadi and Godavari.
| Coalfield | River valley |
|---|---|
| Jharia, Raniganj, Bokaro, Karanpura | Damodar |
| Singrauli | Son |
| Talcher, Ib valley | Mahanadi |
| Singareni | Godavari |
- The Damuda series contains the metallurgical (coking) coal of India.
- Most Gondwana coal is bituminous with fairly high ash content; high-quality coking coal is limited.
- The Jabalpur series belongs to the Upper Gondwana system and is known for plant fossils.
- Gondwana coal is not low-ash; only some Damuda coal is of coking quality.
- Lignite is mainly from Neyveli in Tamil Nadu, and Tertiary coal is in Assam and the north-east, not in Peninsular India.
- Natural gas and petroleum are not in Gondwana or Dharwar rocks; they lie in Tertiary basins.
Deccan Trap: Volcanic Rocks and Regur Soil
The Deccan Trap was formed by the continuous outpouring of basaltic lava through fissures at the close of the Cretaceous, around 66 million years ago, and continued into the Eocene. The lava spread in layers, giving a step-like (trap) appearance. It is divided into the Upper, Middle and Lower Trap and covers almost all of Maharashtra and parts of Gujarat, Karnataka, Madhya Pradesh and, marginally, Andhra Pradesh. Weathering of basalt produces regur (black cotton) soil, ideal for cotton.
The Deccan plateau of Maharashtra, with black soil cotton fields around Nagpur and Akola, shows how the Deccan Trap turned into fertile regur soil. The Western Ghats are the fault-scarp edge of this plateau, not a fold mountain.
Tertiary System and Himalayan Geology
The Tertiary period (Palaeocene to Pliocene) is the age of mammals and of Himalayan mountain building. Tertiary rocks occur in the foothills of the Himalayas, Assam (Barail range and Surma valley), the Garo hills and Kachchh, as well as in Mayurbhanj, Konkan and Malabar. The coal of upper Assam belongs to the Tertiary age. The Tertiary system also gives India its petroleum, found in the Assam, Gujarat and offshore basins, not in the Peninsular rocks.
Himalayan Ranges by Age
| Range | Relative age | Features |
|---|---|---|
| Himadri (Greater Himalaya) | Oldest | Highest peaks; crystalline core |
| Himachal (Lesser Himalaya) | Middle | Dhauladhar, Pir Panjal; some marine fossils |
| Shiwalik (Outer Himalaya) | Youngest | Mammalian fossils; early human remains |
The Shiwalik range is the most recently formed mountain range of India and is rich in mammalian fossils. The Kashmir valley lies in a synclinorium, and the Meghalaya plateau is a detached part of the Peninsula.
Himadri is the oldest Himalayan range and Shiwalik the youngest. The Aravallis, a Pre-Cambrian relict range, are among the oldest fold mountains in the world.
Quaternary System: Alluvium, Karewas and Desert
The Quaternary (Pleistocene to the present) is the youngest system. In India it includes the alluvial plains of the Indus, Ganga and Brahmaputra, the Rajasthan desert deposits and the karewas of Kashmir, lake deposits famous for saffron cultivation. Ice-age deposits in Kashmir also belong to this period. The Narmada and Tapti valleys carry Pleistocene alluvium.
IMAGE (Timeline): Geological time scale and Indian rock systems
Labels: Archean, Dharwar, Cuddapah, Vindhyan, Palaeozoic, Gondwana, Deccan Trap (66 million years), Tertiary (Himalayas), Quaternary
Caption: From Archean rocks to Quaternary alluvium.
Find it: Draw from the table above; Geological Survey of India stratigraphy chart
Mineral Resources by Rock System
| System | Key resources |
|---|---|
| Archean | Mica (Kodarma), granite, gneiss, gold in places |
| Dharwar | Iron ore, manganese, copper, lead, gold |
| Cuddapah | Limestone, slates, asbestos |
| Vindhyan | Sandstone, cement limestone, diamonds |
| Gondwana | Coal |
| Deccan Trap | Basalt, regur soil, building stone |
| Tertiary | Petroleum, natural gas, Assam coal |
Likely Mains Questions on Geological Structure
- Explain how the geological structure of India influences the distribution of minerals. (150 words)
- Discuss the formation of the Himalayas and its effect on the Indo-Gangetic plain. (250 words)
- Why is the Gondwana system considered the most important rock system of India? (150 words)
- Compare the characteristics of the Peninsular block with the Himalayan region. (250 words)
For mains, use a map-based structure: name the system, give its age, its minerals and one state example. Link tectonics (Gondwana breakup, plate collision) to landforms and then to economic geography.
Geology of Odisha: Odisha Angle
Odisha lies largely on the ancient Peninsular block and has among the oldest rocks of India.
- Iron Ore Group: Archean–Dharwar age iron ore in Keonjhar, Sundargarh and Mayurbhanj supports the state's steel and mining sector.
- Gondwana coal: The Talcher and Ib valley coalfields in the Mahanadi valley belong to the Gondwana system.
- Eastern Ghats: They are made of ancient crystalline rocks such as khondalite and charnockite, not Deccan basalt.
- Coastal plain: The Mahanadi delta is Quaternary alluvium.
Odisha's mineral wealth reflects its geology: iron ore from the old Dharwar-age Iron Ore Group, coal from the Gondwana basins and bauxite on the Eastern Ghats highlands.
Geological Structure of India MCQ and PYQ Practice
The Indian Subcontinent was originally part of a huge mass called
- Jurassic Land Mass
- Ayavarta
- Indiana
- Gondwana Continents
Show answer
(d) - India was part of Gondwanaland. IAS (Pre) 1995
Which is the oldest rock system of India?
- Deccan Trap
- Cuddapah System
- Vindhyan System
- Archean System
Show answer
(d) - The Archean system is the oldest. CGPSC 2013
In which rock system is iron ore found in India?
- Vindhyan
- Cuddapah
- Dharwar
- Gondwana
Show answer
(c) - The Dharwar system holds the best iron ore. UPPSC (Pre) 1994
Which one is the correct sequence of geological structures, from oldest to youngest?
- Cuddapah-Dharwar-Gondwana-Vindhyan
- Dharwar-Cuddapah-Gondwana-Vindhyan
- Vindhyan-Gondwana-Dharwar-Cuddapah
- Dharwar-Cuddapah-Vindhyan-Gondwana
Show answer
(d) - Dharwar, Cuddapah, Vindhyan, Gondwana. BPSC 1998
Why are the Gondwana rocks considered the most important rock system of India?
- More than 90% of limestone reserves are found in them
- More than 90% of India's coal reserves are found in them
- More than 90% of fertile black cotton soils are spread over them
- None of the above
Show answer
(b) - They hold over 90 per cent of coal. IAS (Pre) 2010
The Deccan Trap is the major source for which of the following soils?
- Red tropical
- Chernozem soil
- Regur soil
- Laterite
Show answer
(c) - Basalt weathers into regur soil. UPPSC 2001
Which among the following is the most recently formed mountain range?
- Vindhya
- Aravalli
- Shivalik
- Annamalai
Show answer
(c) - The Shiwaliks are the youngest. UPPSC 2010
The Chota Nagpur Plateau is primarily composed of
- sandstone, limestone and shale
- granite, limestone and dolomite
- Archean rocks of granite and gneiss
- Gondwana coal, sandstone and limestone
Show answer
(c) - It is mainly Archean granite and gneiss. WBCS 2018