Tithonian ammonoid biostratigraphy in eastern Himalayan Tibet

The Tithonian and Lower Berriasian sediments in the eastern Himalayas of Tibet contain an extensive sequence of ammonoid fauna. New collections in situ through the Lanongla, Pure, Gucuo and Jiapeila sections have facilitated a major revision of the ammonoid assemblages. Probably due to depositional facies segregation, the Belemnopsis galoi-bearing beds can be regarded as the oldest Tithonian sediments in which the basal Tithonian ammonoid Kossmatia is not present. The Lower Tithonian includes the Virgatosphinctes-Aulacosphinctoides and Uhligites-Aulacosphinctes assemblages; the Upper Tithonian includes the Haplophylloceras pingue, Blanfordiceras wallichi and Haplophylloceras strigile-Corongoceras-Himalayites assemblages. The Spiticeras assemblage is suggested to be from the Lowermost Berriasian. The new ammonoid assemblages at well-defined levels in Himalayan Tibet provide some crucial links for correlation with other regions of the SW Pacific domain where these ammonoid genera have been widely distributed.