The upper part of the Lower Cretaceous (Aptian and Albian) in Spitsbergen is represented by the marine Carolinefjellet Formation, which consists chiefly of shales, siltstones, and sandstones. In this paper five members are recognized within the formation, and a brief lithological description is given for each member. The two uppermost members, Zillerberget and Schonrockfjellet, are defined as new.