Y. Raghumani Singh^1*, K. Bigyapati Devi², W. Ajoykumar Singh^1,3, Kh. Radhapiyari Devi¹, T. Nganthoi Chanu¹, Sh. Priyokumar Singh¹ and L. kilong¹

¹Department of Earth Sciences, Manipur University, Imphal-795003(MN), India

²Department of Geology, Mangolnganbi College, Ningthoukhong- 795126(MN), India ³Department of Geology, Pravabati College, Mayang, Imphal- 795009(MN), India

Abstract

This paper presents the results of Eocene molluscan fauna and benthic foraminifera from the Upper Disang Formation of Indo-Myanmar Ranges (IMR) and discussed here the biostratigraphic zone and depositional environment. These fauna and foraminifera are composed of Bivalvia viz. Noetia magnifica, Pitar (Calpitaria) carteri, Corbula (Bicorbula) rakhiensis, Gastropoda viz. Turritella sp., Turbinella premekranica, Lyria samanaensis and foraminifera Nummulites sp. On the basis of molluscan fauna Noetia magnifica, the biostratigraphic zone (Zone-I) is established and assigned middle-late Eocene age to Upper Disang Formation of IMR, Nagaland. The presence of invertebrate fossils and benthic foraminifers indicate a warm tropical-subtropical climate and shallow marine (neritic) depositional environment during the sedimentation of the Upper Disang Formation.

Keywords: IMR, Inner Paleogene Fold Belt, Molluscan Fauna, Nummulites, Phesama, Upper Disang Formation