Eocene foraminifers of the Naga Hills of Manipur, Indo-Myanmar Range (IMR): Implications on age and basin evolution

Abstract

The Disang Group incorporates the oldest Cenozoic clastic sedimentary rocks that crop out in a series of NNE–SSW trending ridges and valleys throughout much of the Naga Hills. The stratigraphic position of this unit is not well constrained due to a paucity of definitively recognisable, in situ fossils. We report forty-four species attributable of twenty-eight genera. Based on our new reported foraminiferal assemblages, we refine the age and paleoenvironmental interpretations for the Upper Disang Formation. We recognize Planktonic Foraminiferal Zones E14-16 correlative to upper middle Eocene to upper Eocene in the Upper Disang Formation within the Naga Hills. A basin model for this lithological unit involving an upper bathyal bathymetry, rapidly shallowing in a restricted basin with slump deposits where anoxic conditions prevailed is proposed based on field observations, foraminiferal assemblages, and published data.