Palaeontology and Stratigraphy of India
What the domain covers
Palaeontology and Stratigraphy of India tests fossil preservation, index fossils, and the geological succession of the Indian subcontinent. Expect questions on Archean basement, Proterozoic basins, Gondwana coal measures, Deccan Traps, Siwalik vertebrates and Cretaceous-Palaeogene boundaries.
Core rules
- Fossils form by preservation of hard parts, moulds and casts, carbonization, petrification and trace fossils. Index fossils are geographically widespread, short-ranging and easily identified.
- Indian stratigraphy includes Archean gneisses and greenstone belts, the Dharwar Supergroup, the Cuddapah and Vindhyan basins, and the Gondwana Supergroup.
- Gondwana rocks are Permo-Carboniferous to Jurassic, largely continental, and include coal measures with Glossopteris flora.
- The Deccan Traps are Late Cretaceous to Paleocene flood basalts of western India. Siwalik rocks are Cenozoic molasse with terrestrial vertebrates. Kutch and Assam include marine Tertiary sequences.
Worked example
A shale contains Glossopteris leaves and coal seams. Glossopteris is a terrestrial Gondwana plant, not a marine fossil. Its association with coal indicates a Permian freshwater swamp environment. The rock belongs to the Gondwana Supergroup, not to the Vindhyan or Siwalik groups. The reasoning combines fossil habitat, lithology and stratigraphic range.
Traps
Siwalik fossils are mainly terrestrial vertebrates, not deep-marine invertebrates. Vindhyan rocks are mostly Proterozoic, not Gondwana coal-bearing strata. Deccan Traps are volcanic, so they do not yield normal marine fossils. Do not use a long-ranging fossil as an index fossil.