India’s Rock Formation: Archean, Dharwar, Cudappah, Vindhyan, Gondwana and Tertiary Rocks

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; and
• 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 formations

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

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

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.

Vindhyan System

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.