The dinoflagellate cyst (dinocyst) assemblages of two samples from a temporary outcrop in the vicinity of
Haacht (Leuven) have been analysed. The co-occurrence of Areosphaeridium diktyoplokum, Cerebrocysta bartonensis,
Glaphyrocysta semitecta, Rombodinium perforatum and Thalassiphora reticulata allows correlation with the North Sea
Oligocene-1 zone. As a consequence, the considered unit has a latest Eocene to earliest Oligocene age, equivalent to the
age of the marine Tongrian. Comparison of the studied area with the recent 1:50 000 geological map (sheet 24 Aarschot)
shows that the current lithostratigraphic interpretation of the analysed section, i.e. the Middle Eocene Maldegem Formation,
can no longer be uphold.