The Pliocene-Pleistocene transition in the subsurface of the Dutch-Belgian border region: insights from borehole Huijbergen

Cross-border correlations of the Pliocene-Pleistocene successions in the southern Netherlands and northernmost Belgium are problematic, because biostratigraphic markers are often lacking. Correlation is further hampered by the poor age constraints of the Belgian Merksplas Formation. To address these issues, sedimentary, mollusc and dinoflagellate cyst analyses are combined to characterise the lithostratigraphic units in the Huijbergen borehole (The Netherlands) and to provide age estimates. Subsequently, the Huijbergen borehole was correlated with nearby boreholes in Essen and Kalmthout (Belgium). The Piacenzian intervals of the Dutch Oosterhout Formation can be correlated with the Belgian Lillo Formation, with the latter's threefold borehole log signature appearing virtually continuous across the border between both countries. The Dutch Maassluis and Waalre formations are correlated with the shell-bearing lower part and the unfossiliferous higher part of the Merksplas Formation respectively. Although dinocysts are not age-diagnostic for the Maassluis and Waalre formations in borehole Huijbergen, characteristic interglacial marine shells provide a Gelasian age assessment for the Maassluis Formation. By correlation, this age estimate can also be applied to the lower part of the Merksplas Formation, thereby elucidating the Pliocene- Pleistocene transition near the Dutch-Belgian border.