Middle Miocene final demise of remnants of an eastern Neotethyan seaway, Naga Hills, Indo-Myanmar Range

Abstract

Miocene planktonic foraminifers occur in shale intercalated with thinly bedded siltstone and sandstone of the Surma Group in the foothills of the Naga Schuppen Belt of the Indo-Myanmar Range. Fourteen species from eleven genera are the first clearly imaged middle Miocene foraminifers recorded from the Surma Group in the Naga Hills. This new M5-M6 assemblage from the upper unit of the Bhuban Formation correlates to the uppermost Burdigalian to Langhian (16–14 Ma). Biostratigraphy, paleoenvironment and paleogeography of the assemblage are all significant. They provide a basis for widespread regional and global correlation constraining the timing of elimination of the final remnants of the Neotethyan seaway between India and eastern Eurasia. Results indicate that, unlike the western and Tibetan Himalayas where similar seaways disappeared before the Miocene, a shallow marine embayment that connected to the Indian Ocean endured in eastern parts of the India-Eurasia collision zone until the Middle Miocene.