What is the classification of Indian rock system? What are their physical and chemical properties? What are tertiary rock systems? What are the features of the rocks of the Deccan trap? Read further to know more.
Given that Indian rocks may be traced back to as early as the Eoarchean Era, the country’s geology is quite diversified.
Some of the rocks have undergone significant alteration.
India’s geographical land area can be classified into the Archaean rock system, the Purana rock system, the Dravidian rock system, and the Aryan rock system.
The Archaean Rock System
Rocks that were created before the Cambrian system.
The rock system of the Archaean includes:
Archaean Schists and Gneisses
The mineral makeup of gneiss ranges from granite to gabbro. Schists, which are primarily crystalline, contain minerals like mica, talc, hornblende, chlorite, etc.
These are the rocks:
- Oldest (pre-Cambrian) rocks [were formed approximately 4 billion years ago].
- When rocks formed, the earth’s surface was extremely hot and the molten lava solidified.
- They are referred to as the “Basement Complex” and serve as the foundation for future layers.
- Since they are volcanic in origin, azoic or non-fossiliferous, foliated (composed of thin sheets), completely crystalline, and plutonic intrusions (volcanic rocks found deep inside).
The Earth has formed 4 billion years ago, less than a billion years ago.
- Elevated metamorphic sedimentary rock system. [developed as a result of the metamorphism of Archaean gneisses and schists]
- They are the first rocks that undergo metamorphism.
- Found in great quantity in the Karnataka district of Dharwar.
- The most significant rocks in terms of economics are those that contain precious minerals like high-grade iron ore, manganese, copper, lead, gold, etc.
Also read: Earth’s Crust: Elements, Minerals and Rocks
Purana Rock System
Formed about 1400 – 600 million years ago.Includes the Vindhyan System and the Cuddapah System, two divisions.
The Cuddapah district of Andhra Pradesh is where outcrops can be best seen. Ores of iron, manganese, copper, cobalt, nickel, etc. can be found in these rocks. Large limestone resources of cement grade are present there.
The massive Vindhyan mountains are where this system gets its name. The system comprises 4000 m-thick layers of old sedimentary rocks on top of an Archaean basis. They are predominantly fossiliferous. The Deccan trap has a significant part of this belt covered.
Panna and Golconda diamonds were mined in the diamond-bearing regions of the Vindhayan system. It lacks metalliferous minerals but is rich in limestone, clean glassmaking sand, durable stones, and beautiful stones.
Dravidian Rock System
They are Palaeozoic in nature.
- Formed between 600 and 300 million years ago.
- They are extremely uncommon in peninsular India and are only found in the Extra Peninsular region (the Himalayas and Ganga plain). [The term “Dravidian” does not imply that they are indigenous to South India]
- It has many fossils.
- The Dravidian system includes the rocks from the Cambrian, Ordovician, Silurian, Devonian, and Carboniferous periods. (None of these is significant; only the Carboniferous is.)
Approximately 350 million years ago, limestone, shale, and quartzite made up the majority of the Carboniferous rocks.
- Limestones from the Upper Carboniferous period make up Mount Everest.
- The Carboniferous era saw the beginning of coal formation.
- In geology, carboniferous refers to coal-bearing. [The majority of the coal discovered in India is not from the Carboniferous era; excellent coal from the Great Lakes region in the USA, the United Kingdom, and the Ruhr region is from the Carboniferous era]
Aryan Rock System
Upper Carboniferous to the recent. It also has different types.
The Gondwana System gets its name from the first inhabitants of Telangana and Andhra Pradesh, known as the Gonds.
- They are deposits that were formed in synclinal troughs on the surface of an old plateau.
- The loaded troughs sank as the sediments built up.
- Terrestrial plants and animals flourished in these troughs where fresh water and sediment accumulated.
- This has occurred since the Permian era (250 million years ago)
A thick succession of shallow water deposits was created in Rajasthan and Kuchchh as a result of the marine incursion that occurred in the later Jurassic period. In Kuchchh, you can find coral limestone, sandstone, conglomerates, and shales.
Between Guntur and Rajahmundry, on the Peninsula’s eastern shore, there is another transgression.
Deccan Traps were created by volcanic eruptions that occurred over a substantial area of Peninsular India between the end of the Cretaceous and the beginning of the Eocene.
- Fissures released basaltic lava that spread over a vast area of around 10 lakh sq km.
- These volcanic deposits are known as “traps” in Swedish, which means “stair” or “step” because of their flat top and steep sides.
- The Deccan Trap is now approximately half the size it once was due to weathering and erosion (denudation), a process that has been occurring for millions of years.
- About 5 lakh square kilometres of the Kuchchh, Saurashtra, Maharashtra, Malwa plateau and northern Karnataka are currently covered by the Deccan Trap.
- The Deccan Traps are 3,000 metres thick in the west, 600–800 metres thick in the south, 800 metres thick in Kuchchh, and barely 150 metres thick in the east.
- The long-term weathering of these rocks produced the “regur,” or black cotton soil.
Rocks of the Tertiary System
Between the Eocene and Pliocene eras, these rocks were created. The Himalayan mountain range has grown in the following ways:
- The Oligocene period saw the formation of the Great Himalayas.
- The Miocene era saw the formation of the Lesser Himalayas.
- The Pliocene and Upper Pliocene epochs saw the formation of shiwaliks.
- Eocene and Oligocene-era structures in Gujarat, Rajasthan, and Assam contain mineral oil.
- The Tertiary epoch has been divided into four temporal sections: the Eocene, Oligocene, Miocene, and Pliocene.
Also Read: Exogenic Forces: Classification – ClearIAS
Rocks of the Quarternary System
These rocks can be found in the Ganges and Indus River plains.
- The Pleistocene and Holocene epochs are separated temporally into two portions that make up the Quarternary epoch.
- The term “Bangar” refers to an old alluvial soil that was produced during the Upper and Middle Pleistocene.
- At the conclusion of the Pleistocene epoch, alluvial soil production started, and it is currently ongoing in the current Holocene epoch. It is called “khadar.”
- The valley in Kashmir was created during the Pleistocene epoch.
- A lake once occupied this valley. The current form (valley), known as “kareva,” was created as a result of the constant deposition of the earth.
- The Thar Desert is where Pleistocene-era deposits can be discovered. The ocean once contained the “Rann of Kachchh.” In the Pleistocene and Holocene eras, sedimentary sediments filled it.
India’s geology history exhibited a distinctive and varied nature. Classification of Indian rocks is based on the geological structure of our country which includes the physical and chemical properties. Rocks from various geologic eras can be found in different parts of India. The Pangaean supercontinent once included the Indian Craton. The Himalayan mountain range was created after the Gondwanaland craton broke (225 million years ago) and drifted towards the Eurasian craton (65 my ago).
The Indo- Ganga- Brahmaputra plain region formed in the upper Pliocene and Pleistocene eras following a series of vast spared alluvial plains in the Outer Himalayas. As a result, different regions of India have rocks that represent practically every sort of geological structure from various geologic eras.
Article Written By: Atheena Fathima Riyas