Geological Structure of Rajasthan (Question–Answer Format)
This article presents concise and factual question–answers on the topic “Geological Structure of Rajasthan”, specially designed for B.A. Part-II students.
Question 1: Describe the main features and major geological time sequences of Rajasthan’s geological structure.
Answer:
The geological structure of Rajasthan is highly diverse and complex, making it an important part of the Indian Shield. It contains rock formations ranging in age from the Archaean and Pre-Cambrian eras to the Recent period.
- Part of the Ancient Shield:
Rajasthan forms a significant segment of the Indian Shield, showing varied geological and tectonic characteristics. Its Pre-Cambrian geology is represented by a multi-stage reworking of the Archaean basement (Banded Gneissic Complex – BGC). - Pre-Cambrian and Proterozoic Structures:
Both Archaean and Pre-Cambrian formations coexist in Rajasthan. The Aravalli and Delhi Supergroups show Mesoproterozoic and Neoproterozoic fold–thrust belts, which developed repeatedly over time. - Malani Magmatic Suite (MIS):
The Malani Igneous Suite is a unique feature of Indian geology. The rocks of the Malani series are rhyolitic lava flows lying over the Aravalli schists. The Erinpura granite, Sindreth, and Punagarh volcanic rocks represent the Neoproterozoic magmatic activity. - Rock Groups and Supergroups:
The Aravalli Supergroup and Delhi Supergroup belong to the Pre-Cambrian time scale. The oldest rocks are found in the Banded Gneissic Complex (BGC) and Bundelkhand Gneiss formations. - Tectonic Polarity:
The tectonic and geological polarity of the Pre-Cambrian era in Rajasthan was westward, which continued into the Phanerozoic period. Major Proterozoic ophiolitic suture zones include the Aravalli Suture (Rakhabdev–Jharol, ~1.5 Ga) and the South Delhi Suture (Phulad, ~1.0 Ga). - Mineral Wealth:
Rajasthan occupies a prominent position in India’s mineral landscape, with world-class deposits of lead, zinc, and copper (such as Agucha, Zawar, Dariba, and Khetri) and numerous non-metallic mineral reserves. - Sedimentary Basins:
Alongside the Proterozoic Vindhyan and evaporitic Marwar sequences, Mesozoic and Cenozoic basins developed in western Rajasthan — notably the Barmer, Bikaner, Nagaur, and Jaisalmer basins.
Question 2: Write a short note on the geological origin and significance of the Aravalli Mountain Range.
Answer:
The Aravalli Range in western India is one of the oldest mountain systems in the world, estimated to be over 2.5 billion years old.
- Origin and Extent:
The Aravalli Range originated from the remnants of Gondwanaland and stretches about 692 km from Palanpur (Gujarat) to Delhi (Northeast). Within Rajasthan, its length is around 550 km (79.49%) of the total. - Geological Composition:
The range is primarily composed of metamorphic rocks belonging to the Aravalli and Delhi Supergroups of the Pre-Cambrian age. In Ajmer and western Mewar, rocks of the Delhi group form the beautiful hill ranges. - Geographical Role:
The Aravalli Range divides Rajasthan into two major regions — the western arid (desert) region and the eastern semi-arid plains. It also acts as a climatic barrier, restricting the eastward spread of the Thar Desert. - Economic Importance:
The Aravalli region is rich in marble, granite, and mica, along with metallic minerals such as copper, lead, and zinc, making it a significant mining zone of India.