Geology of India
Geological History of India
India is mostly located on the Indian Plate, which is generally called the northern portion of the Indo-Australian Plate. Indian subcontinent, Australia, New Guinea, and Tasmania, New Zealand etc. have a common geological history by virtue of being an integral part of the Mesozoic Gondwana super-continent until 160 million years ago. The earth is 4700 million years old and the earliest supercontinent Vaalbara started forming around 3600 million years ago. It took nearly 400 million years to get completed and was ready by 3100 million years ago. Then, around 2500 years ago, Vaalbara started breaking. The result of this breaking was that another supercontinent Kenorland formed around 2700-2500 million years ago. The breaking kept on and then Supercontinent Columbia formed around 1800-1500 million years ago. Around 750 million years ago, a new supercontinent was formed that was called Rodinia.
In the late Paleozoic period (542 – 250 million years ago) super continent Pangaea was formed that existed during the Paleozoic and Mesozoic eras. Pangaea started beginning to break up approximately 200 million years ago, before the component continents were separated into their current configuration. It first broke into Northern Laurasia (Angaraland) and Southern Gondwanaland.
Later, the Laurasia and Gondwana drifted apart. Gondwana included Antarctica, South America, Africa, Madagascar, Australia-New Guinea, and New Zealand, as well as Arabia and the Indian subcontinent, which have now moved entirely into the Northern Hemisphere. Thus, from geological history two main structural divisions of India are:
- Himalayan Mountain Chain, which is a part of Laurasia or Angaraland
- southern pan called Gondwanaland of which Peninsular India formed one of the blocks.
The intervening space between the two giant continental blocks was filled with water. It was a shallow sea called Tethy’s Sea. During the subsequent geological periods, the Indian Peninsular block began drifting northward leaving a huge gap filled with water which truly came to be called the Indian Ocean. As the peninsular block continued its drift northward, the Indian Ocean continued to advance and filled up the depressions on either side of the landmass when it compressed the Tethy’s Sea. Thus, the Arabian Sea and Bay of Bengal were formed. What was once the Tethy’s Sea has become the Mediterranean Sea. Other remnants are the Black, Caspian, and Aral Seas (via a former inland branch known as the Paratethys).
The similarity in the geological formation produced more or less similar type of mineral wealth in both India and Australia. Despite the variance in the biotic life between India and Australia, there are certain endemic plant and animal species, pointing to the super continent connection. Please note that Strait of Lombok is part of the biogeographical boundary between the fauna of Indomalaya ecozone and the distinctly different fauna of Australasia. The boundary is known as the Wallace Line, for Alfred Russel Wallace, who first remarked upon the striking difference between animals of Indo-Malaysia from those of Australasia and how abrupt the boundary was between the two biomes.
India’s Rock Formations (Stratigraphy)
India, being a large country, has diverse geology. Different regions in India contain rocks of all types belonging to different geologic periods. Some of the rocks are badly deformed and transmuted while others are recently deposited alluvium that has yet to undergo diagenesis. Mineral deposits of great variety are found in the subcontinent in huge quantity. Structurally the Indian landmass is divided into three main divisions consisting of
- The Himalayan Mountain Chain
- The North Indian Plain
- The Peninsular Plateau.
However, stratigraphically, India can be divided into several divisions such as Archean System, Dharwar System, Cudappah system, Vindhyan system, Paleozoic,Mesozoic, Gondwana, Deccan Trap, Tertiary and Alluvial.
Archean rocks, also known as Pre-Cambrian rocks are the oldest rocks of the earth’s crust. The Archean period covers 86.7% of Total geological history time of earth and therefore is very significant. This period marks the development of first photosynthesis, the life support atmosphere. The major characteristic of the Archean rocks is that they are azoid,means that are devoid of any form of remnants of life in them. They serve as the basement complex or fundamental gneisses.
The Archean rocks in India are called Purana Rocks means the oldest rocks. The Archean or Purana rock system in India is found in Aravallis mountains, 2/3rd of the Deccan peninsula and some parts of north east. These rocks have abundant metallic and non-metallic minerals such as iron, copper, manganese, bauxite, lead, zinc, gold, silver, tin, tungsten, mica, asbestos, graphite, etc.
Dharwar system is later than the Archean system but older than the other systems. The Dharwar period of rock formation has been largely fixed from 2500 million years ago to 1800 million years ago. Dharwar Rock System is special because it is the first metamorphic sedimentary rocks in India. They are named Dharwar system because they were first studied in Dharwar region of Karnataka. But they are also found in Aravallis, Tamil Nadu, Chotanagpur plateau, Meghalaya, Delhi, and the Himalayas region.
The Dharwar rocks are rich in iron ore, manganese, lead, zinc, gold, silver etc. The Champions series containing gold mines lie within this system. This Champion system is named after the Champion reef in the Kolar Gold Fields. The Kolar Gold Fields contain one of the deepest gold mines of world.
The other series of Dharwar system are as follows:
- Champaner series that is found near Baroda. This is source of a lush green variety of marble.
- Closepet series that is found in Balaghat and Chhindwara of Madhya Pradesh. It is rich in Copper ores.
- Chilpi Series that is found in and around the Closepet series in Balaghat and Chhindwara
- Iron-Ore series that is located in Singhbhum, Mayurbnhanj and Keonjhar rangaes.
Cudappah System rocks are rich in metamorphic rocks such as sandstone, shale, limestone, quartzite, and slate. They contain iron and other inferior quality of ores and minerals. They are mainly found in Cudappah district of Andhra Pradesh along with other places such as Chhattisgarh, Rajasthan, Delhi, and the lesser Himalayas. One of the important series of Cudappah System is Papaghani series, named after the river of same name in Andhra Pradesh.
The Vindhyan Mountains form a dividing line between the Ganges plain and Deccan Plateau. The Vindyan system is named after Vidhyan Mountains. This system rocks are extensively distributed in India from Chittorgarh (Rajasthan) to Sasaram (Bihar). The Vindhyan System is separated from Aravallis by the Great Boundary Fault. They are famous sources of Red Sandstone and other building material. The well known Panna and Golconda diamonds are found in this formation. The important series of this system are Bhander series, Bijwar series and Kaimur series. All are rich sources of Building material.
Gondwana System or Carboniferous period System or Dravidian System
As the name suggests, these are the major coal deposits of India.This system contains famous Damuda and Panchet series which are famous for coal deposits (discussed below). The important coal bearing areas of this series are Raniganj, Jharia, Karanpur, and Bokaro of the Damodar basin in Odisha, and the Pench valley in Chhattisgarh and Madhya Pradesh, the jhingurda coal seam (Chhattisgarh). The Gondwana Supergroup forms a unique sequence of fluviatile rocks deposited in Permo-Carboniferous time. Damodar and Sone river valley and Rajmahal hills in the eastern India is depository of the Gondwana rocks.
The Cretaceous system or the Deccan Trap
Some people broadly divide the geographical land area of India into three parts viz. Deccan trap, Gondwana and Vindhyan. The Deccan Trap covers almost all of Maharashtra, some parts of Gujarat, Karnataka, Madhya Pradesh and marginally Andhra Pradesh. Deccan Trap is thought to have formed as result of sub-aerial volcanic activity associated with the continental deviation in this part of the Earth during the Mesozoic era. This implies that generally, the rocks of Deccan Trap are igneous. The Deccan system is marked by a transgression of the sea at Coromandal coast and Narmada valley and the upwelling of huge quantity of Lava/ basalt, so the Cretaceous system or Deccan Trap is made up of Basalt rocks. This system is also called lava trap and is 3000 meters deep. The rocks of this system are found in Maharashtra, Gujarat, Madhya Pradesh, Chhattisgarh, Jharkhand, Orissa, and Karnataka.
- Deccan Trap and Paleontological Murder Mystery
- Some scientists believe that a series of monumental volcanic eruptions in India may have killed the dinosaurs 65 million years ago, not a meteor impact in the Gulf of Mexico. The eruptions, which created the gigantic Deccan Traps lava beds of India, are now the prime suspect in the most famous and persistent paleontological murder mystery, say scientists who have conducted a slew of new investigations honing down eruption timing. The main phase of the Deccan eruptions spewed 80 percent of the lava which spread out for hundreds of miles. It is calculated to have released ten times more climate altering gases into the atmosphere than the nearly concurrent Chicxulub meteor impact, according to volcanologist Vincent Courtillot.
- How it was formed?
- When the Indian Plate mobbed northward after breaking off from the rest of Gondwana, it passed over a geologic hotspot, the Réunion hotspot, which caused extensive melting underneath the Indian craton. The melting broke through the surface of the craton in a massive flood basalt event, creating what is known as the Deccan Traps. It is also thought that the Reunion hotspot caused the separation of Madagascar and India.
The Tertiary System
The Tertiary rock system belongs to Cenozoic era. The Cenozoic era has two periods’ viz. tertiary and quaternary. The beginning of the tertiary period is about 66 million years back. The final break- up of the Gondwana land occurred in this era and the Tethys sea got lifted in the Himalayas. The most important rocks of this system are in northern plains of India, karewas of Kashmir and bhadarwah, Bhangar, and Khadar of the Great Plains. The terraces of Jeelum Narmada, Taptii, Godavari, Krishna, Kaveri, etc. are of this period. The rocks of this system are also found in coast of Kachchh, Katiawar, Konkan, Malabar, Nilgiri, and the Eastern Ghats.
Gondwana and Tertiary Coal Deposits of India
Most of the coal mined in India comes from the rock formations of two geological ages viz.L ower Gondwanaand Tertiary. About 80 per cent of the coal deposits in India is of bituminous typeand is of non-coking grade. This is one of the reasons that India has to rely upon imports of coking coal. Gondwana Coal
Gondwana coal has overwhelmingly higher share (99%) in India’s coal resources and the entire coal mined in the peninsular plateau part belongs to this category. This coal was formed in carboniferous period between 600 to 300 million years ago. The coal obtained from the Gondwana formations is mainly bituminousand needs to be converted into Coke before it can be used in the iron and steel industry.
Distribution of Gondwana Coal
The Gondwana coal mines are located in river valleys of Damodar, Mahanadi, Godavari, Son and Narmada. Damodar valley is home to largest coal mines in Jharkhand-West Bengal coal belt located in Jharia (largest coal field of India), Raniganhj (second largest coal field of India), Bokaro, Giridih, Karanpura , Chandrapur, Tatapani, Talcher, Himgiri, Korba, Singrauli etc.
On the basis of geological units, there are three different Gondwana formations viz. Raniganj
Formation, Barkar Formation and Karharbari Formation. Karharbari Formation is the oldest coal formation in India.
The states in which Gondwana coal fields are found include Jharkhand, Orissa, Chhattisgarh, West Bengal, Madhya Pradesh, Andhra Pradesh, Maharashtra, Uttar Pradesh, Bihar, Sikkim, Assam, with the quantity of reserves in the same order.
Tertiary coal fields share only 1% of coal production of India. Such fields occur in Assam, Arunachal Pradesh, Meghalaya and Nagaland and also in small quantities in Jammu & Kashmir. It is extracted from Darangiri, Cherrapunji, Mewlong and Langrin (Meghalaya); Makum, Jaipur and Nazira in upper Assam, Namchik – Namphuk (Arunachal Pradesh) and Kalakot (Jammu and Kashmir).
Tertiary coal is the lignite coal. Lignite also occurs in the coastal areas of Tamil Nadu, Pondicherry, Gujarat and Jammu and Kashmir. The coal is of inferior quality with around 30 to 50% carbon. India’s largest ignite deposits are at Neyveli in Tamil Nadu.
81% of the coal production in India comes from open pit mines while underground mining currently accounts for around 19% of national output.
List of Gondwana Coalfields
- West Bengal
- Damodar Valley: Raniganj (Trans Barakar),Bankura
- Darjeeling District: Bagrakote, Tindharia
- Damodar Valley: Ranigunj (Cis Barakar), Jharia, Bokaro, Chandrapura, South Karampura, North Karampura, Ramgarh
- Rajmahal Area: Hura, Gilhuria and Jilbari, Chuparbhita, Pachwara, Brahmini
- Deogarh Area: Kundit Kuria, Sahajuri, Jainti
- Hazaribagh District: Giridhi, Chope, Itkhori. Palamu Region: Anuranga, Daltongunj, Hutar
- Madhya Pradesh
- South Rewa Region: Singrauli, Korar, Johilla river, Umaria, Sohagpur
- North Chattishgarh Region: Jhilmili, Tatapani-Ramkola, Sanhat, Jharkhand, Chirimiri- Kurasia, Koreagarh, Bassar, Bisrampur, Lakhanpur, Panchbhaini, Dambhamunda, Sendargarh
- South Chattishgarh Region: Hasdo -Rampur, Korba, Raigarh, Mand River,
- Satpura Region: Mohpani, Sonada, Sahpur (Tawa), Dulhara (Tawa), Pathakera, Bamhanwara, Upper Tawa Valley, Kanhan Valley, Pench Valley.
- Wardha Valley: Kamptee, Bandar, Warora, Rajur (Wun), Ghugus – Telwasa, Chanda, Ballarpur, Wamanapalli, Antargaon – Aksapur, Sasti – Rajpura.
- Mahanadi Valley: Talcher, Ib river (Rampur – Hingir).
- Andhra Pradesh / Telangana
- Pranhita – Godavari Valley Tandur Kanala, North Godavari, South Godavari, Jangam, Chinur-Sendrapalli, Kamavaram, Bandala – Alapalli, Singareni (yellendu), Lingala, Kothagudium, Damar-cherla, Kannergiri, Beddadanuru.
- Uttar Pradesh
- Kota (in Mirzapur District) Assam Abor, Aka and Daphla Hills
- Ranjit Valley List of Tertiary Coal Fields
- Makum coalfield in Dibrugarh district is the main coalfield. Other include Nahorkatiya, Doigrung, Nambor and Longoi.
- Khasi Jaintia and Mikir hills, Balyong, Doigring and Waimong coal-fields
- Arunachal Pradesh
- Namchick- Namphuk (Tirap) Abor hills, Miri, Daphla, Aka hills and Miao Bum
- Nagaland: Nazira, Janji, Disai and Barjan are important coalfields of Nagaland.
- Jammu and Kashmir: Kalakot, Mohogala, Metka, Ladda and Saugar Marg