Eocene ostracods from southern Tibet: Implications for the disappearance of Neo-Tethys

Abstract

The Yadong area was located in the residual Neo-Tethyan basin during the Paleogene. It contains a record of the youngest marine deposition in the Tethyan Himalayas. Therefore, biostratigraphic data from this area are essential to constrain the timing of elimination of the Tethyan Ocean and the India-Asia collision. Ostracods are one of the most diverse groups of living crustaceans, inhabiting marine, non-marine and even some semi-terrestrial habitats. They provide important evidence to reconstruct paleoenvironment and biogeography. This investigation examined ostracod faunas recovered from the Paleogene Zhepure Formation in the Gulupu section, Tüna, Yadong, southern Tibet. The formation can be further divided into a lower Limestone Member and an overlying Shale Member, which are conformable. Abundant, diverse well-preserved marine ostracods were recovered from the Shale Member. We report 29 species from 15 genera. The stratigraphic distribution of the Eocene ostracod assemblages found reveals three ostracod zones, and shows strong affinity to sections previously investigated throughout the Neo-Tethyan region. The Zhepure Formation also yields diverse planktonic and benthic foraminifers, charophytes, nannofossils, and pteropods and indicates that open marine conditions existed widely during the Eocene. Based on this study of little-known Eocene ostracods, we suggest that final closure of the Tethyan seaway occurred after early Late Eocene.