The youngest marine deposits preserved in southern Tibet and disappearance of the Tethyan Ocean

Abstract

Fossil ages as young as Priabonian (38–34Ma) are reported for the last marine sedimentary rocks in southern Tibet. Correlation is based on examination of foraminifers and nannofossil biostratigraphy of youngest preserved sediments in sections at Gamba (Zongpu), Tingri (Qumiba) as well as a previously unreported section at Yadong. Our results demonstrate that a marine seaway remained in existence south of the Yarlung Tsangpo suture zone until at least Priabonian time. Notably this remains a maximum age estimate in this area as all sections are truncated by erosion or faulting. We compare our results with sections throughout the Himalaya region to demonstrate that shallow marine conditions existed widely during the Eocene period. In fact, it seems likely that the marine conditions in the Tethyan Himalaya did not entirely disappear by the end of Priabonian, especially in the eastern Himalaya. The data presented in this study place direct constraints on the elimination of the Tethyan Ocean and thus have important implications for timing of the India–Eurasia collision.