The Geulhemmerberg Cretaceous/Tertiary boundary section (Maastrichtian type area, SE Netherlands); summary of results and a scenario of events

Abstract

Integration of sedimentological, biostratigraphical, geochemical and paleomagnetic analyses of the recently discovered marginal marine Cretaceous/Tertiary (K/T) boundary section in the Geulhemmerberg caves (Maastrichtian type area, Limburg, SE Netherlands) resulted in a depositional model of the succession, placing the results in a global K/T boundary perspective. The proposed depositional scenario involves 1) deposition of marginal marine Upper Maastrichtian calcarenites and formation of a paleo-relief (proto-hardground, Berg en Terblijt Horizon), 2) deposition of latest Maastrichtian calcarenites, 3) K/T storm or hypercane-related 'washing' of the paleoshelf, and removal of latest Maastrichtian and earliest Danian sediments, including removal of an Ir-bearing layer, and 4) storm-induced filling of the paleodepressions in the Late Maastrichtian paleorelief by calcarenites and K/T boundary clays during early P0 Zone times of decreasing storm intensity. Only the distributions of calcareous nannoplankton and ammonites do not fully match this scenario, since early Tertiary nannofossils have been reported from below the Berg en Terblijt Horizon and, at a nearby outcrop, ammonites from just above it. Their distribution patterns across the K/T boundary in the area require further study. We conclude that there is an unprecedented expanded earliest Tertiary succession in Limburg, containing a wealth of information about the first hundreds of years following the mass-extinction event at the K/T boundary.