Hint: Tertiary system -though not included in Sir T Holland system geological classification of Indian Geologic History, is important for certain reasons like the Himalayas were born during this time period, It is the age of mammals, and the Oligocene system belongs to it.
Rock System Based on Geological History Of India is divided into four systems:
- The Archaean Rock System.
- The Purana Rock System.
- The Dravidian Rock System.
- The Aryan Rock System.
This classification was done by Sir T Holland. These rock systems are placed according to their developmental time, e.g. the Archean rock system developed first and the Aryan rock system developed last.
The Archean Rock system developed during the beginning of precambrian time and lasted for approximately 4 million years. The Archean rock system includes Archean Gneisses and Schists. Geiss refers to the Mineral composition varies from granite to gabbro. Schists are mostly crystalline and include mica, talc, hornblende, chlorite, etc. These rocks are the oldest and are formed because of the solidification of molten gamma. These rocks are not fossilised, that is they are unfossiliferous.
The Dharwar system is a subdivision of the Archean system. The rocks from the Dharwar system are highly metamorphosed and are found abundantly in Dharwad district of Karnataka. These are considered to be the most important rocks from the economic point of view because they contain valuable minerals like high-grade iron ore, manganese, lead, copper, gold, etc.
Hence the correct answer is option ‘C’.
Note: The Aryan rock system was developed recently during the Jurassic time. It began to develop during the Carboniferous time. Its Tertiary system is the most significant period in India’s geological history because the Himalayas were born and India’s present form came into being in this period.