🪨 Indian Geography — Chapter 02

Geological Structure of India  |  BPSC / BSSC Exam Preparation  |  Exam Fusion Prep
🌍 Origin — Pangaea Theory
🌐 Division of Pangaea
  • Pangaea → divided into Angaraland (North) and Gondwanaland (South)
  • Indian subcontinent was part of Gondwanaland
📊 4 Groups of Indian Rocks
1️⃣
Archaean Group
2️⃣
Purana Group
3️⃣
Dravidian Group
4️⃣
Aryan Group
⏳ Geological Timeline
Era-wise Classification
Oldest
Archaean / Pre-Cambrian Era
Gneiss & Schist — No fossils — 86.7% of Earth formation
Purana Group
Cuddapah + Vindhyan Systems
Layered sedimentary rocks — Origin of life — Eastern Ghats, Vindhya Plateau
Paleozoic Era
Dravidian Group
First evidence of life — Rich fossils — Absent almost everywhere except Rewa (MP)
Mesozoic → Recent
Aryan Group
Gondwana (coal), Deccan Trap (basalt/black soil), Tertiary (Himalayas), Quaternary (alluvial)
⚡ QUICK RECALL — Fossil Memory
⛏️ Group 1 — Archaean
🌏 Archaean System — Most Ancient Rocks
  • Contribute ~86.7% in formation of the Earth
  • Formed during cooling of the Earth
  • No Fossils — Pre-biological era
  • Rock types: Gneiss and Schist
Bundelkhand Gneiss (most ancient)
Bengal Gneiss
Found In:
Karnataka
Tamil Nadu
Andhra Pradesh
Madhya Pradesh
Odisha
Chotanagpur Plateau (Jharkhand)
🏔️ Dharwar System of Rocks
  • Formed by erosion & deposition of Archaean rocks
  • Most developed in Dharwar region, Karnataka
  • No Fossils
  • Aravalli mountain range — formed from these rocks
⚡ QUICK RECALL
Dharwar rocks → Aravalli mountains bane | Most developed in Karnataka (Dharwar district)
🚨 EXAM TRAP
📦 Group 2 — Purana
🔵 Cuddapah System
  • Formed by erosion of Archaean + Dharwar rocks
  • Layered rocks (sedimentary)
  • No fossils — but origin of life on Earth
  • Named after Cuddapah district, Andhra Pradesh
  • Eastern Ghats — formed from these rocks
🟣 Vindhyan System
  • Plateau — divides Ganga Plain from Deccan
  • Layered, formed by water deposition
  • General absence of fossils
  • Minerals: limestone, sandstone, china clay, copper clay
📊 Cuddapah vs Vindhyan — Comparison
Feature Cuddapah System Vindhyan System
Formation Archaean + Dharwar erosion Water deposition
Fossils Absent (origin of life) Generally absent
Landform Eastern Ghats Vindhya Plateau
Named After Cuddapah district (AP) Vindhya mountains
Minerals — Limestone, Sandstone, Clays
🚨 EXAM TRAP
🦕 Group 3 — Dravidian
🦴 Paleozoic Era Rocks
  • Rocks of Paleozoic Era
  • First evidence of life on Earth
  • Has rich fossils — sabse zyada fossils
  • Absent from almost whole India
  • Found only in: Rewa district, Madhya Pradesh
🚨 EXAM TRAP — Most Asked!
Dravidian Group = almost absent from India — sirf Rewa (MP) mein milte hain. Lekin sabse important = First/Rich Fossils. Ye contradiction yaad rakho!
⚡ QUICK RECALL
Dravidian = Paleozoic Era | Rich Fossils = First life evidence | Location = Only Rewa, MP
🔥 Group 4 — Aryan (4 Sub-Systems)
🪨 1. Gondwana System — Coal Treasure
  • Construction of basin landforms
  • Fossils present
  • ~98% of India's coal reserves found here!
Spread In:
Damodar Valley
Mahanadi Valley
Rajmahal
Satpura
98%
India's Coal Reserves in Gondwana Rocks
🌋 2. Deccan Trap System — Black Soil Origin
  • End of Cretaceous Era → Volcanic activity in western Peninsular India
  • Basalt lava flow → step-like landform (trap = step)
  • Mainly in Maharashtra and Malwa region
  • Also formed: Rajmahal Trap
  • Basalt erosion → Fertile Black Soil (Regur)
Deccan Trap States:
Maharashtra
MP
Gujarat
Karnataka
Andhra Pradesh
⚡ QUICK RECALL
Deccan Trap → Basalt Lava → Black Soil (Regur/Cotton Soil) → Best for cotton cultivation
🏔️ 3. Tertiary System
  • Formed: Eocene to Pliocene epoch
  • Formation of Peninsular Plateau
  • Formation of Himalayan mountains
🌊 4. Quaternary System
  • Rocks of Pleistocene + Holocene epoch
  • Deposits at mouths of Indo-Gangetic Plains
  • Also in Deltaic regions
  • Most recent rocks
🚨 EXAM TRAP
📋 Complete Master Summary Table
Group System Era Fossils Key Feature Location/Landform
1. Archaean Archaean System Pre-Cambrian Absent 86.7% Earth formation, Gneiss & Schist Karnataka, TN, AP, MP, Odisha, Jharkhand
Dharwar System Pre-Cambrian Absent Formed from Archaean erosion Aravalli mountains, Dharwar (Karnataka)
2. Purana Cuddapah System Pre-Cambrian Absent Origin of life, layered rocks Eastern Ghats, Cuddapah (AP)
Vindhyan System Pre-Cambrian Gen. Absent Limestone, Sandstone, Clays Vindhya Plateau (Ganga–Deccan divide)
3. Dravidian Paleozoic Rocks Paleozoic Rich Fossils First life evidence, Absent almost everywhere Only Rewa district (MP)
4. Aryan Gondwana System Mesozoic Present 98% India's coal reserves Damodar Valley, Mahanadi, Rajmahal, Satpura
Deccan Trap Cretaceous end — Basalt lava → Black Soil (Regur) Maharashtra, MP, Gujarat, Karnataka, AP
Tertiary System Eocene–Pliocene — Himalayas + Peninsular Plateau formed Himalayan region
Quaternary System Pleistocene–Holocene — Most recent rocks Indo-Gangetic Plains, Delta regions
🎯 Most Important Points for BPSC/BSSC
🚨 Top Exam Points
  • Coal (98%) → Gondwana rocks
  • Black Soil → Deccan Trap (Basalt)
  • Richest fossils → Dravidian Group
  • Dravidian rocks in India → only Rewa (MP)
  • Aravalli → Dharwar rocks
  • Eastern Ghats → Cuddapah rocks
  • Most ancient → Bundelkhand Gneiss
  • IST + Tropic of Cancer meet → Chhattisgarh
⚡ Memory Tricks
  • A P D A = Archaean, Purana, Dravidian, Aryan (4 groups order)
  • No fossils → Arch, Dhar, Cudd, Vindh (4 oldest)
  • Gondwana = Coal = Damodar Valley (JH/Bihar)
  • Deccan Trap = TRAP matlab steps → volcanic stairs
  • Quaternary = most RECENT → alluvial soil of Ganga
⚡ BIHAR SPECIAL RECALL
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