lithoStratigraphy of bengal basins

StratigraphyThe study of strata (layers) of rocks with an eye toward interpreting the geologic history of the regionClosely tied to dating methodsUses a variety of methods - fossils, stable isotopes, paleomagnetics, sedimentary cycles - to correlate and distinguish layersVery important for oil exploration and mining

Stratigraphic PrinciplesPrinciple of cross-cutting relationships

Any layer that is cut by something else has to be older than thatApplies to igneous intrusions, faults, veins, erosional surfaces, etc.

Principle of stratigraphic superpositionOldest rocks are on the bottomYoungest rocks are on the top

Principle of UniformitarismForces at play in nature today are those during the past are uniform.

Principle of Faunal SuccessionSediments in sequence,each layer is characterised by an assemblage of fossils

Lithostratigraphy of Bengal Basin

Bengal basin extends from Latitude 20°43´ to 26°36´N and Longitude 88°3´ to 92°40´E. Bengal Basin, covers part of the Himalayan piedmont plain and covers the eastern and southeastern hill ranges of the Sylhet, Chittagong.The stratigraphy of Bengal Basin is somewhat problematic because the greater part is covered by thick alluvium and almost all the strata are devoid of faunal fossilsCome under extra peninsula

Bengal has a thick stratigraphic succession of mostly Tertiary sediments. The thickness of practically all units increase in a southerly direction and the strata that are deltaic or shallow marine in the north become progressively more marine to the south (Alam 1989).

Geographical changes U.Jurassic to L. Cretaceous period:- Rajmahal basalts.During cretaceous period:- eastern sea coast started formingU. Cretaceous period:- Ghatal formation was depositedPaleocene period:- sea regression and sand shale deposition has taken place known as Jalangi formationDuring Eocene time:- detrital influx was meager, widespread limestone depositionThe Oligocene period:- deposition of Burdwan formation. Miocene period :- Himalayan uplift and deposition has taken place in deltaic environmentRecent period:- sea has regressed and alluvium is deposited in the flood plain environment

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