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Stratigraphy & Indian Geology
Stratigraphic Principles & Indian Geology
Superposition, the geological time scale and the Precambrian-to-Quaternary architecture of the Indian subcontinent.
PART 1
Topic Breakdown & Traps
The Engineering Principle
Stratigraphy orders rocks in time using superposition (older below younger in undeformed strata), original horizontality, lateral continuity, cross-cutting relationships and faunal succession. The geological time scale divides the Phanerozoic into Paleozoic, Mesozoic and Cenozoic. Indian stratigraphy ranges from the Archean Dharwar cratons through the Proterozoic Cuddapah and Vindhyan basins, the coal-bearing Gondwana Supergroup, the ~66 Ma Deccan Traps, to the Neogene Siwaliks of the Himalayan foreland.
The Core Formula Matrix
Key boundaries (Ma): Cambrian base ≈ 541 · P–Tr ≈ 252 · K–Pg ≈ 66.
Hiatus across an unconformity: older age − younger age.
Sedimentation time: thickness ÷ accumulation rate.
Deccan Traps: flood basalts erupted ≈ 66–65 Ma (near K–Pg).
Hiatus across an unconformity: older age − younger age.
Sedimentation time: thickness ÷ accumulation rate.
Deccan Traps: flood basalts erupted ≈ 66–65 Ma (near K–Pg).
The ‘IIT Traps’
- ⚠Superposition needs undeformed beds. Overturned folds invert the order — check way-up criteria first.
- ⚠Gondwana = coal, not the Gondwana continent only. India's coalfields are Permo-Carboniferous Gondwana.
- ⚠Deccan ≈ K–Pg, not Archean. Deccan Traps are end-Cretaceous, not Precambrian.
📚 Standard references
- Geology of India — M. Ramakrishnan & R. Vaidyanadhan
- Principles of Stratigraphy — Michael E. Brookfield
PART 2
Progressive 3-Tier Question Suite
Q1BASIC1 Mark · MCQ
The law stating that, in undeformed strata, older beds lie below younger beds is the law of
Q2MEDIUM1 Mark · MCQ
The Deccan Trap basalts of India erupted close to the
Q3MEDIUM2 Marks · NAT
A m sequence accumulated at m/Myr. The time represented is _____ Myr.
Myr