Question

Indian rock belongs to different geologic periods, thus geology of India is very diverse. In this context Write a note on the major rock system of India and their economic significance.

Answer 1

Approach:

• Introduction
• Briefly explain different rock system of India
• List out the economic significance.
• Draw a map showing Indian rock system

Indian rocks are very diverse and they date back from the archean period to recent quaternary period of the era. Following are the different rock system of India and their economic Significance.

Archean rocks:
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 earth and therefore is very significant. This period marks the development of the first photosynthesis, the life support atmosphere.
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 the northeast. 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:
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 have named the 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.

Cuddapah System
These rocks have been formed as a result of erosion and sedimentation of the rocks of the Dharwar system. These are also sedimentary rocks.The rocks have been named after the district of Cuddapah in Andhra Pradesh where these are semi-circular in expansion.These are famous for sandstone, limestone, and marble, asbestos.The Cuddapah rocks are also found in Rajasthan.

Vindhyan System
These have been formed after the cuddapah rocks by the deposition of silt of river valleys and shallow oceans. Thus, these rocks are also sedimentary rocks.

The evidence of fossils of microorganisms is found in this structure.These rocks are found in the Vindhyas, e.g. the Malwa plateau, the Semari range in the Son valley, Bundelkhand etc.

This structure is famous for house-building rocks. The Sanchi Stupa, the Red Fort, the Jama Masjid etc are built with the red sandstone of this structure. Besides, limestone, china clay, dolomite etc are also found in this structure.The diamond mines of Golconda in Karnataka and Panna in Madhya Pradesh are found in this structure.

Gondwana System
The word Gondwana has originated from the Gond region of Madhya Pradesh.98% of coal in India is found in this structure. These rocks have been formed between the Carboniferous and Jurassic periods. Several cracks were formed in peninsular India during the Carboniferous period. basin-like depressions were made because of the sinking of land among these cracks. Coal was formed by the burying down of the vegetation of that period. This coal is now found mainly in the river valleys of the Damodar, the Son, the Mahanadi, the Godavari, and the Wardha etc.

The Deccan Trap
The volcanic action in peninsular India began in the last period (Cretaceous period) of the Mesozoic era. Thus, the Deccan trap has been formed as a result of the fissure eruption.This structure is made up of basalt and dolerite rocks. These rocks are very hard and their weathering has resulted in the formation of the black soil. This structure is found in the most parts of Maharashtra and some parts of Gujarat, Madhya Pradesh and Tamil Nadu.