Flow stratigraphy has been carried out in the Rajmahal Traps from exploratory boreholes drilled for coal in the western sector of Bengal Basin. Different volcanic flows have been demarcated according to their broad megascopic characters. These flows are primarily basaltic in nature. It mainly contains plagioclase, augite along with magnetite and Ti-magnetite and shows porphyritic texture. Inter-trappean sediments are largely argillaceous in nature and restricted towards the lower part of this volcanic sequence. However, a prominent megacrystic plagioclase bearing basaltic flow zone occurs persistently in the middle part. It demarcates two separate modes of eruption in the entire volcanic sequence. Episodic volcanism during initial phase results intermittent deposition of inter-trappean sediments below this zone whereas eruption becomes fairly continuous during later stage which inhibits sedimentation above the megacrystic flow. As this megacrystic zone is very prominent and well persistent, it can be treated as marker horizon.

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