A latest Eocene depocenter in between uplifted masses (SW Netherlands and NW Belgium)

Abstract

Under Priabonian (latest Eocene) far-field compression, the major Jurassic graben systems and their proximal areas experienced domal uplift in the Netherlands and northeastern Belgium. It has been proposed that this flexural uplift was simultaneous with flexural subsidence of the surrounding areas. This hypothesis is, however, only based on the correlation of few widely spaced boreholes without supporting biostratigraphic or seismic data. For this study, a seismic line and cross-boundary borehole log correlation panel, comprising three biostratigraphically analyzed boreholes, were used to critically examine the abovementioned hypothesis. The seismic line and correlation panel run from the southern flank of the uplifted West Netherlands Basin, also known as the Voorne Trough, towards the south. They both show a gradual thickening of the Priabonian sequences towards the Voorne Trough, confirming the flexural subsidence hypothesis. The underlying Bartonian and overlying lowermost Rupelian units do not share the abovementioned thickness trend, which highlights the particularity of Priabonian basin dynamics. Within the Priabonian depocenter, plenty of reworked organic material was deposited, mostly of Bartonian age, providing further evidence of the simultaneity of subsidence and uplift in nearby regions. We consider it very likely that subsidence and uplift were part of the same vertical surface deformation process. The results of this study are consistent with the mechanism of lithospheric folding under far-field compression by the convergence between Africa and Europe. A Priabonian N-S compressional stress-field would also be consistent with fault, joint and vein analyses performed at the British Isles west of the study area. As the regional stress-field changed around the Eocene–Oligocene boundary, the vertical surface movements of the study area also changed.

Graphical Abstract