ABSTRACT: In this study the foraminifera of the glacial erratic Heiligenhafener Kieselgestein (HKG) consisting of siliceous sandstones are documented for the first time. The glacial erratics in northern Germany were deposited during the Pleistocene. The age of the HKG sandstone is indicated as Eocene from 49.6 Ma to 47.8 Ma. The lower limit is given by the first occurrence of the planktonic foraminifera Pseudohastigerina micra (Cole 1927). The upper limit is derived from previous studies of the Eocene succession of Northern Germany based on benthic foraminiferal faunas. The HKG fauna indicates a boreal, fully marine environment characteristic for a water depth between 50 m and 80 m.