RAS question
Aravalli Supergroup represents which geological era?
Correct answer: (A) Archean-Proterozoic.
The Aravalli Supergroup in Rajasthan represents Proterozoic supracrustal rocks resting over an Archaean basement, so the correct geological association is Archaean-Proterozoic.
Explanation
The Aravalli Supergroup is not a recent rock sequence. The GSI background note places Rajasthan's Archaean basement rocks in the Bhilwara Supergroup and then states that Proterozoic supracrustals, including the Aravalli and Delhi supergroups, rest over this Archaean basement. That is why the exam answer is Archaean-Proterozoic: the basement is Archaean, while the Aravalli Supergroup belongs to the Proterozoic supracrustal cover. These Proterozoic supracrustals host important mineralisation, including gold, lead, zinc and copper. For RAS, the key is to connect the Aravalli Supergroup with Rajasthan's ancient shield geology rather than with younger eras such as the Cenozoic, Mesozoic or Paleozoic.
Why the other options are wrong
- (B) Cenozoic is a much more recent era, whereas the Aravalli Supergroup is placed in Proterozoic supracrustals over an Archaean basement.
- (C) Mesozoic refers to a younger era commonly associated with dinosaurs, but the Aravalli Supergroup is tied here to the older Archaean-Proterozoic geological framework of Rajasthan.
- (D) Paleozoic is an intermediate era and does not match the description of the Aravalli Supergroup as Proterozoic rocks resting on Archaean basement.
Concept
This tests Rajasthan's geological structure, especially the age relationship between the Archaean basement and the Proterozoic Aravalli Supergroup. It recurs in RAS because Rajasthan geography often links rock systems with mineral belts and ancient shield geology.