Previous Year Question
Which one of the following is the appropriate reason for considering the Gondwana rocks as the most important of rock systems of India?
More than 90% of limestone reserves of India 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 reasons given above is appropriate in this context
Correct Answer: B
Detailed Solution
The Gondwana rock system is India’s most important coal-bearing rock group. More than 90% of India’s coal reserves occur in the sedimentary rocks of the Gondwana sequence.
Formation of Gondwana Rocks
Gondwana rocks were deposited principally in faulted troughs or river-valley basins of Peninsular India.
These rocks were formed mainly from the remains of ancient vegetation, sandstone, shale and other sediments.
Under pressure and temperature, the accumulated plant remains were gradually converted into coal.
Indian Gondwana coal is principally associated with the Permian Period.
Major Gondwana Coalfields
Gondwana coal reserves principally occur in the following river valleys:
Damodar Valley: Raniganj, Jharia, Bokaro, Giridih and North-South Karanpura
Son Valley: Singrauli
Mahanadi Valley: Talcher, Ib Valley and the Korba region
Godavari Valley: Singareni coalfields
Wardha Valley: Coalfields of Maharashtra
Satpura region: Pench-Kanhan-Tawa coalfields
Jharia is India’s major coking-coal field, whereas a large proportion of Gondwana coal is used for thermal-power generation and industrial purposes.
Why are the Other Options Incorrect?
Option (a) is incorrect
More than 90% of India’s limestone reserves do not occur in Gondwana rocks. Major limestone deposits are principally associated with the Vindhyan, Cuddapah and other sedimentary rock groups.
Option (c) is incorrect
Black cotton soil was formed mainly through the weathering of basaltic rocks of the Deccan Traps. It is not directly associated with the Gondwana rock system.
Option (d) is incorrect
Option (b) provides the appropriate reason for the importance of the Gondwana rock system; therefore, the assertion that none of the reasons is appropriate is incorrect.
Hence, the correct answer is more than 90% of India’s coal reserves.