Bihar, located in the eastern part of India, exhibits a rich and diverse geological framework. Its geological setup provides insights into the ancient history of the Earth, significant rock formations, and their economic potential. The state is divided into three distinct physiographic zones: the Southern Plateau region, the Ganga Plains, and the Himalayan foothills in the north. Each region reflects unique geological features and rock formations.
1. Geological Framework of Bihar
Physiographic Divisions
Southern Plateau Region:
Consists of ancient igneous and metamorphic rocks.
Composed of parts of the Chotanagpur Plateau and Rajmahal Hills.
Rich in mineral resources.
Ganga Plains:
Characterized by recent alluvial deposits.
Formed by the sedimentation process of rivers like the Ganga, Kosi, Gandak, and Son.
Northern Himalayan Foothills:
Transitional zone with sedimentary rock formations.
Impacted by tectonic activities.
2. Stratigraphy and Rock Formations
Precambrian Rocks
Found mainly in the southern part of Bihar.
Include Archaean and Proterozoic rocks.
Composed of:
Granite gneisses: Fundamental rocks that form the base.
Schists and quartzites: Resulting from metamorphism.
Pegmatites and dolerites: Intrusive rocks, often rich in minerals.
Gondwana Formations
Found in the coalfields of Bihar, particularly in areas like Rajmahal and Karanpura.
Represented by:
Sandstones, shales, and coal seams.
Significant fossilized flora providing paleoclimatic evidence.
Rajmahal Trap
Cretaceous volcanic formations.
Composed of basaltic lava flows.
Associated with laterite soils and manganese deposits.
Tertiary Sediments
Found in the northern foothills.
Composed of conglomerates, sandstones, and clays.
Alluvial Deposits
Quaternary period deposits in the Ganga Plains.
Composed of fine silts, sands, and clays, providing fertile agricultural lands.
3. Major Rock Types in Bihar
1. Igneous Rocks
Found in the southern plateau and Rajmahal Hills.
Include granite, basalt, and dolerite.
Economic importance: used in construction and as decorative stones.
2. Metamorphic Rocks
Include gneisses, schists, and quartzites.
Found in the southern part of Bihar.
Rich in minerals like mica and feldspar.
3. Sedimentary Rocks
Found in the Gondwana formations and northern foothills.
Sandstones and shales dominate these regions.
Economically significant for coal and fossil studies.
4. Recent Alluvium
Covers the extensive Ganga Plains.
Essential for agriculture due to high fertility.
4. Economic Significance of Geological Formations
Mineral Resources
Bihar is endowed with significant mineral wealth:
Mica: Found in Nawada and Gaya districts.
Limestone: Used in cement and lime production.
Coal: Present in the Gondwana formations of the Rajmahal coalfields.
Pyrite: Found in Rohtas, used in fertilizer production.
Iron Ore: Found in smaller quantities in the southern region.
Hydrocarbons
Presence of Gondwana formations indicates potential for oil and natural gas exploration.
Construction Materials
Sandstone, granite, and laterite are used extensively in building and infrastructure.
5. Geological Hazards in Bihar
Seismic Activity
Northern Bihar lies in Seismic Zone V, indicating a high risk of earthquakes.
The Himalayan foothills are prone to tectonic activities.
Flooding
The Ganga Plains, due to their flat topography and river systems, are prone to frequent floods.
Soil Erosion
High erosion rates in northern regions and plateau fringes due to deforestation and intensive agriculture.
6. Geological Research and Exploration in Bihar
Extensive studies by the Geological Survey of India (GSI).
Exploration of mineral resources to boost the local economy.
Studies on Gondwana fossils for understanding paleoclimate and tectonics.
7. Conservation and Sustainable Use
Preservation of mineral resources through judicious mining practices.
Development of flood control measures to protect the fertile alluvial plains.
Promoting eco-tourism in regions like Rajgir and Bodh Gaya, which also hold geological significance.