Geological Structure of Bihar

Bihar's rocks belong to four major systems:

1. Dharwar Rock System (Pre-Cambrian)

• Found in SE Bihar: Aurangabad, Gaya, Nawada, Jamui, Munger.
• Composed of mica, schist, quartzite, phyllite, gneiss.
• Oldest metamorphic rocks; Azoic with no fossils.

2. Vindhyan Rock System (Pre-Cambrian)

• Found in Kaimur district and Son Valley (Rohtas).
• Sedimentary rocks: sandstone, limestone, dolomite, quartzite, shale.
• Non-metalliferous and unfossiliferous.

3. Tertiary Rock System (Cenozoic Era, 66–2.6 million years ago)

• Found in north-western Bihar (Terai/Shiwalik region).
• Rocks: sandstone, sandy shale, mudstone, conglomerate.

4. Quaternary Rock System (Pleistocene, last 1 million years)

• Found between Himalayan Terai in north and Chota Nagpur plateau in south.
• Recent deposits, containing fossils of living species.
• Rocks: sandstone, conglomerate, coarse gravel.