New ammonoid taxa from the<scp>L</scp>ower<scp>C</scp>retaceous<scp>G</scp>iumal<scp>F</scp>ormation of the<scp>T</scp>ethyan<scp>H</scp>imalaya (<scp>N</scp>orthern<scp>I</scp>ndia)

Abstract

Abstract Knowledge of the E arly C retaceous ammonoids of the NW ‐ H imalayas was poor until recent discoveries. Intense sampling from the G iumal F ormation exposed near the village of C hikkim ( S piti V alley, H imachal P radesh, I ndia) led to the recognition of a new E arly C retaceous ammonoid fauna. The succession consists of arenitic sandstone interbedded with shale that was deposited by turbidity currents on an unstable shelf in the E arly C retaceous. Ammonoids have been obtained only from sandstone beds in the lower one‐third and close to the top of the c . 350‐m‐thick section. Eight new ammonoid taxa (1 genus and 7 species) are described: S inzovia franki sp. nov. (rare), G iumaliceras giumaliense gen. et sp. nov. (abundant), G iumaliceras bhargavai gen. et sp. nov. (rare), N eocomites ( E ristavites ) platycostatiformis sp. nov. (rare), C leoniceras oberhauseri sp. nov. (abundant), A ustraliceras himalayense sp. nov. (rare) and D eshayesites fuchsi sp. nov. (rare). S inzovia and D eshayesites are reported for the first time from the T ethyan H imalaya. According to the biostratigraphic relevance of some ammonoid taxa described here, the age of the G iumal F ormation can be constrained from B erriasian ( G iumaliceras assemblage) to A ptian ( C leoniceras assemblage). The discovery of the new fauna substantiates the significance of the G iumal F ormation around C hikkim and facilitates comparison with faunal assemblages from other regions in the T ethys O cean and beyond.