1.6 Geosynclines

Case Study 1: Himalayan Orogeny and Tethys Geosyncline

• Models/Theories/Laws:
  • Geosynclinal Theory (Kober, Stille)
  • Plate Tectonic Theory (Convergent Boundary)
  • Isostasy and Crustal Shortening
• Recent Data:
  • Geological Survey of India (GSI) reports confirm active crustal uplift in the Higher Himalayas at ~5 mm/year.
  • Ongoing Indo-Eurasian plate convergence at ~44 mm/year (Indian Plate GPS data, 2023).
  • Tethys geosyncline was ~2000 km wide during Mesozoic (fossil & sediment evidence).
• Spatial Variation:
  • Himalayan segments show differential uplift:
    • Kumaon Himalayas: ~4.8 mm/year
    • Sikkim Himalayas: ~6.2 mm/year
    • Western Nepal: highest seismic strain zones
• Temporal Variation:
  • Uplift and orogenesis ongoing since late Eocene (~50 MYA)
  • Modern seismicity reflects reactivation of older geosynclinal features
• Source:
  • GSI Annual Report (2023)
  • National Institute of Rock Mechanics (NIRM)
  • DownToEarth (Sept 2023)
  • Philosophical Transactions of the Royal Society A (2023)
• Insight:
  • The Himalayan system evolved from the Tethys Geosyncline due to plate convergence, proving the shift from classical geosyncline theory to plate tectonic paradigm.

Case Study 2: Vindhyan Basin as a Type of Epicratonic Geosyncline

• Models/Theories/Laws:
  • Stille’s Classification of Geosynclines (miogeosynclines, eugeosynclines)
  • Cratonic Stability Theory
  • Sequence Stratigraphy Model
• Recent Data (2023):
  • Vindhyan Supergroup sediment thickness: ~6 km
  • BARC-ISRO borehole data shows minimal tectonic deformation → stable cratonic setting since ~Proterozoic (~1600 MYA)
  • High uranium and rare earth mineral reserves detected (2023)
• Spatial Variation:
  • Vindhyan Basin: over 1,00,000 sq km across Madhya Pradesh, Uttar Pradesh, Chhattisgarh
  • Greater mineral potential in eastern and southern zones
• Temporal Variation:
  • Sedimentation occurred in phases between 1600–500 MYA
  • Tectonic activity minimal post-Precambrian, indicating tectonic quiescence
• Source:
  • BARC-ISRO Deep Drilling Initiative (2023)
  • PIB (Jan 2024): “Rare Earth Potential in Vindhyans”
  • Economic & Political Weekly: "Geological Stability of Central Indian Cratons" (2023)
• Insight:
  • Vindhyan basin represents a stable epicratonic geosyncline, contrasting the active Himalayan geosyncline, aligning with Stille’s geosyncline classifications and stratigraphic models.