Review of the lithostratigraphy of the Middle Eocene in northern Belgium

The lithology of Middle Eocene deposits, and that of stone layers in particular, was studied in subcrops in northwestern Belgium, allowing the following conclusions regarding their lithostratigraphy to be drawn. On account of its brown colour (lignite), the upper part of the Pittem Member (Gent Formation) has proved to often be a conspicuous key horizon. On the basis of a study of the geometry of the deposits in various boreholes and of the sandstone facies it can now be confirmed that the Beemem Member (previously referred to the Aalter or Knesselare formations) in fact belongs to the Vlierzele Formation. The Oedelem Formation (new name) consists of fossil-rich sand (Aalter Member or Aalter sands sensu stricto) on top of which rests the Evergem Member (new name), which comprises glauconitic sand. In borehole interpretations, this unit has been confused with the Vlierzele sand or with the Wemmel sand. Previous records of Lede Formation strata in the area between Gent and the North Sea coast are here confirmed.