A palynological investigation of the Miocene Zonderschot Sands (Berchem Formation) from the type locality Zonderschot (northern Belgium) has revealed the presence of a diverse dinoflagellate cyst and acritarch association. The dinoflagellates reflect a shallow marine environment, although the oceanic species Nematosphaeropsis and Impagidinium are prominent in the association and indicate the presence of an oceanic influence. This can be explained only by the depositional area being located at the very southern margin of the relatively isolated North Sea Basin during a period of maximum landward extent of the marine realm. A precise biostratigraphical correlation of the Zonderschot Sands with the Antwerpen Sands (Berchem Formation) from the Antwerp area is established. Biostratigraphical evaluation of key dinoflagellate cyst species indicates a latest Burdigalian (latest Early Miocene) -(earliest?) Langhian (early Middle Miocene) age for the Zonderschot Sands.Sedimentological and biostrati-graphical arguments are proposed that may indicate that the Génicot Formation was deposited just before, during and just after the Hirnantian (latest Ordovician) glaciation. This means the first indication of the presence of the latter in Belgium.