Abstract Cretaceous limestones near Maastricht (SE Netherlands) have been quarried at least since Roman times. In the late eighteenth century, scientific interest developed in their macrofossil content and specimens were illustrated for the first time. Amongst the early discoveries was a partial skull of a large predatory vertebrate that would play an important role in the emergence of modern palaeontology and our understanding of the concept of extinction. After decades of scientific debate, this animal was recognized as a large extinct marine relative of monitor lizards (varanoids) and named Mosasaurus. A detailed lithostratigraphy of Upper Cretaceous (Santonian–Maastrichtian) rocks was established in the Maastrichtian type area during the mid-1970s, which resulted in a renewed interest in fossil hunting by professional and amateur palaeontologists alike. During recent decades, both micro- and macrofossils have enabled a refinement of biozonations, correlations within the basin and with sections elsewhere, a greater insight into taphonomic processes and updated taxonomic interpretations. A new age model and chemostratigraphical framework is the most recent addition, permitting the placement of geoheritage in a larger frame and intensifying outreach to the public, including also virtual and augmented reality and hands-on experience to visitors of museum and (disused) quarries alike.

Abstract In southern Belgium, 23% of abstracted groundwater volumes are from chalk aquifers, representing strategic resources for the region. Due to their specific nature, these chalk aquifers often exhibit singular behaviour and require specific analysis. The quantitative evolution of these groundwater resources is analysed for the Mons Basin and Hesbaye chalk aquifers as a function of past evolution, in the short and long term. Groundwater level time series exhibit decreases when analysed over different periods. This is particularly visible for the Hesbaye chalk aquifer when comparing the 1960–90 and 1990–2020 periods. Such decreases are associated with observed temperature increases and precipitation decreases, inducing a decrease of aquifer recharge, and a probable increase of groundwater abstraction in the adjacent catchment. Past evolution is also discussed considering recent winter and summer drought events. The aquifers exhibit long delays in response to recharge events, particularly where the thickness of the partially saturated zone plays a crucial role in observed delays. Regarding future evolution, simulations of the impact of climate changes using medium–high emission scenarios indicate a probable decrease of the groundwater levels over the Hesbaye chalk aquifer.

Abstract: The mechanical strength, porosity and permeability of chalk are affected by chemical and mineralogical changes induced by fluids that are chemically out of equilibrium with the host rock. Here, two high-porosity Upper Cretaceous chalk cores from Liège were tested at effective stresses beyond yield at 130°C during flooding with MgCl 2 and NaCl brines. Core L1 (flooded by MgCl 2 brine) deformed more than L2 (flooded with NaCl brine), with volumetric strains of 9.4% and 5.1%, respectively. The porosity losses estimated from strain measurements alone are 5.82% for L1 and 3.01% for L2. However, this approach does not account for dissolution and precipitation reactions. Porosity calculations that are based on strain measurements in combination with (i) the weight difference between saturated and dry cores and (ii) the solid density measurement before and after flooding show an average porosity reduction of 3.69% between the two methods for L1. This discrepancy was not observed for core L2 (with the NaCl brine). The rock and effluent chemistry show that Ca 2+ dissolved and Mg 2+ is retained within the core for the L1 experiment. Therefore, accurate porosity calculations in chalk cores that are flooded by non-equilibrium brines (e.g. MgCl 2 ) require both the volumetric strain and chemical alteration to be considered.