The age of the uppermost part of the Rurikfjellet Member, Janusfjellet Formation, underlying the Helvetiafjellet Formation, is discussed on the basis of the occurrence of dinoflagellate cysts. Samples collected from thirteen localities in western and central Spitsbergen were examined. Forty‐eight dinoflagellate cyst species were recorded during the study, but only a few provide good time resolution. They show that the youngest beds of the Rurikfjellet Member, previously regarded to be of Hauterivian age, belong to the Barremian. The presence of Barremian sediments below the base of the Helvetiafjellet Formation at several widely separated localities constrains the diachronism of the Rurikfjellet Member ‐Helvetiafjellet Formation transition.

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