Gondwana System (Mesozoic Era): Geological Structure of India

Gondwana System

The 'Mesozoic'= middle life. The term is used for a period of geologic time in which the presence of fossil invertebrates dominated the rocks.

The Mesozoic Era includes three periods: Triassic, Jurassic, and Creatceous.

In the Geological Scale Time Scale, these periods extend from the Upper Carboniferous up to the beginning of the Cenozoic Era or the Aryan Era.

The term 'Gondwana' was covered by H.B. Medicott in 1872. It was derived from the ancient tribe of Gonds that inhabits the central provinces of Madhya Pradesh.

The Gondwana formations are fluviatile and lacustrine in character. They were deposited in the river basins and lakes during the Upper Carboniferous Period. These basins later subsided along the trough faults amidst ancient rocks of the great southern continent called the Gondwanaland. These rocks were formed during the Upper Carboniferous and the Jurassic Periods (Mesozoic Era).

The Gondwana group begins with the Permo-Carboniferous period, which, in the Standard Geologic Time Scale, is known as a period of coal formation. The lower Gondwana rocks are found in;

1. Talcher series: 

• It is the series of the Gondwana system named after Talcher in Dhankenal district of Odisha.

• It is rich in good quality coal used for smelting and in thermal power plants.

• Talcher coalfield has the highest coal reserves in India of 38.65 billion tonnes. This coalfield is divided into five (5) production areas namely- Talcher, Jagannath, Kalinga, Lingaraj, and Hingula.

• The industries in Talcher are located along the river Brahmani which flows from the northwest (NW) to southwest (SW).

2. Damuda series:

• The Damuda series belong to the Middle Gondwana Period which contains enormous deposits of coal seams. The coal seams are thicker and more elongated in the eastern coalfields than in the west.

• The important coal-bearing areas of this period are- Raniganj, Jharia, Karanpura, and Bokaro of the Damodar basin, Singrauli, Korba, and Pench Valley (Chattisgarh and Madhya Pradesh), Talcher (Mahanadi Basin, Odisha), and Singareni (Satpura Basin, Madhya Pradesh).

• The Jhingurda Coal Seam with a thickness of about 131 m is the thickest in India.

3. Panchet series:

• It is the youngest series of the Lower Gondwana System, which derives its name from the hill of that name, south of Raniganj. 

• The series consists of greenish sandstone and shales. It is, however, devoid of coal-seams.

• The iron-ore shales of the lower Gondwana system are particularly well developed in the Raniganj coalfields (West Bengal). However, they contain inferior quality iron ore, i.e., sindrites and limonite. Being inferior in quality, they are generally not mined for iron. 

The Gondwana System of rocks provides over 95% of the coal of India. Most of the good-quality coal deposits (bituminous and anthracite) of India are found in Gondwana formations. Moreover, iron ore occurs in the iron-stone shales of Raniganj coalfields. In addition to coal and iron, kaolin, fire-clay, sandstone, and grits are found in the Gondwana formations. 

The Gondwana rocks are also found in the Himalayas from Kashmir to Arunachal Pradesh and Poorvanchal. The coal seams of these areas are metamorphosed. They are also found in Saurashtra, Kachchh, Western Rajasthan, Coromandal Coast, and Rajmahal Hills.

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