Microfacies analysis of Cretaceous/Tertiary boundary sections in the quarries Geulhemmerberg and Curfs, SE Netherlands

Abstract

Detailed thin-section microfacies analysis reveals the temporal and spatial variation of the depositional and early diagenetic conditions of the upper part of the Meerssen Member of the Maastricht Formation, now considered to span the Cretaceous/Tertiary (K/T) boundary, at Geulhemmerberg and Curfs (Maastrichtian type area, SE Netherlands). The precession- induced cycles of the Meerssen Member have been formed due to periodic variations of hydrodynamic energy and of deposition rate. Their genesis is similar to that of other precession-induced cycles encountered in the underlying Maastrichtian and Campanian carbonates. The microfacies distribution shows that the calcarenitic Geulhemmerberg sediment has been deposited under higher hydrodynamic energy conditions and in deeper water than the coeval sediments of quarry Curfs. The microfacies is locally characterised by dissolution features that may have been produced by percolating meteoric water during syn-sedimentary exposure. We propose that the intercalated clay layers, despite their open marine microfossil assemblage, were deposited under conditions of very low wave energy in very shallow marine depressions that were only affected during storms.