Stratigraphy and Indian Geology
Stratigraphy and Indian Geology tests the principles used to order rock layers, the geological time scale, and the stratigraphic succession of India.
Principles
- Superposition: oldest at bottom in undeformed sequences.
- Original horizontality, lateral continuity, cross-cutting relationships (younger cuts older), inclusions (inclusions are older than host).
- Faunal succession: fossils change in a definite order.
Indian succession, old to young
- Archean: Dharwar Supergroup, schists and gneisses, gold.
- Proterozoic: Cuddapah Supergroup (arenaceous and argillaceous, diamonds) and Vindhyan Supergroup (limestone, sandstone).
- Paleozoic to Mesozoic: Gondwana Supergroup, coal-bearing, Glossopteris flora.
- Cretaceous to Paleogene: Deccan Traps basalt.
- Tertiary to Quaternary: Siwalik Group with vertebrate fossils; alluvium.
Worked example
A sequence has Vindhyan limestone below Gondwana coal below Deccan basalt. Reasoning: Vindhyan is Proterozoic, Gondwana is Permo-Carboniferous to Jurassic, Deccan is latest Cretaceous to Paleogene. Order: Vindhyan, then Gondwana, then Deccan.
Traps
Cuddapah and Vindhyan are both Proterozoic but Cuddapah is older. Gondwana coal is not Tertiary; Tertiary coal occurs in Assam. Deccan Traps are not Archean.