In addition to the type species, Binkhorstia ubaghsii, which is fairly common in the upper part of the Nekum Member (Maastricht Formation) in the wider vicinity of Maastricht (the Netherlands) and Binkhorstia euglypha, which appears to be restricted to the overlying Meerssen Member of the same formation (uppermost Maastrichtian), a third member, B. desaegheri nov. sp., is recorded from the upper middle Santonian of the Campine area in north-east Belgium. The history of Binkhorstia is convoluted, serving as a prime example of how attempts to unravel the higher-level taxonomic position of late Mesozoic crabs may prove difficult. Over time, the genus has been referred to various families or subfamilies, either podotreme or putative eubrachyuran; here the new family Binkhorstiidae is placed in the superfamily Retroplumoidea. Binkhorstiids appear to have been a relatively short-lived endemic group that fell victim to Cretaceous‒Paleogene (K/Pg) boundary perturbations.

Luminescence dating methods are widely used to date coastal sediments, while luminescence tracing methods are an upcoming approach to reconstruct coastal sediment pathways. Both methods rely on subaqueous resetting (bleaching) of luminescence signals and would benefit from quantification of this process in the natural coastal environment. We describe the set-up and outcomes of an in situ subaqueous bleaching experiment for luminescence signals of K-feldspar grains in the Dutch Wadden Sea. We deployed a full-day bleaching field experiment with irradiated feldspar samples tethered to a pole at various positions within and above the water column to quantify (1) the bleaching potential, that is, the light intensity and spectrum as a function of time, depth and tidal stage, and (2) the bleaching efficiency, that is, the degree of bleaching of infrared stimulated luminescence (IRSL) and post-infrared IRSL (pIRIR) signals measured at 150, 225 and 290°C after a full day of light exposure above and below water. Our bleaching-potential results show that the strongest subaqueous light attenuation took place during low tide when sediment concentrations are the highest. We also observed stronger attenuation of the ultraviolet part of the spectrum compared to other parts of the spectrum. Our bleaching-efficiency results show that bleaching reduces with depth, that pIRIR signals bleach slower than IRSL signals underwater and that bleaching efficiency reduces with pIRIR measurement temperature. None of the investigated signals were fully reset after 13.5 hours of light exposure, even for subaerially exposed samples. Our work provides the first quantitative data on pIRIR bleaching in a natural subaqueous environment, which is relevant for K-feldspar-based luminescence dating and tracing applications.

The lower Triassic Main Buntsandstein Subgroup represents a promising, but high-risk geothermal play in the Netherlands. Although the gross thickness in boreholes locally exceeds 200 m, the spatial distribution, geometries and preservation of these sedimentary units remained uncertain due to the lack of seismic data with sufficient resolution and the sparse borehole network. This creates uncertainty in the quantification of the aquifer dimensions that is essential for the planning of geothermal operations.

In this study, seismic interpretation and 2D palinspastic restoration of new and reprocessed seismic data were conducted and combined with borehole data to assess the tectonic evolution of the Roer Valley Graben in the southeastern Netherlands and its control on the spatial distribution of the Main Buntsandstein Subgroup sediments. Our results show that the central and southern parts of the Roer Valley Graben were active depocenters in the Early to Middle Triassic times dominated by fluvial sandstone deposition, providing important play elements for prospective leads on geothermal exploration. The northern part of the basin was a more marginal area where mostly fine-grained sediments were deposited. To the northwest, differential subsidence resulted in the development of areas where the Buntsandstein thickness is reduced to ∼150 m.

After deposition, the Main Buntsandstein sediments were compartmentalised by faulting related to post-depositional tectonic activity, locally reducing the lateral extent of the geothermal target areas down to 1–2 km in a ∼NE–SW direction. On the platform areas adjacent to the Roer Valley Graben and to the southeast, Jurassic sediments are largely absent and the Main Buntsandstein sediments are present at depths shallower than 2 km. These platforms are promising targets for further investigation, as the relatively shallow burial depths, compared to the central part of the Graben, may have contributed to the preservation of more favourable reservoir properties.

Methane is a common constituent of groundwater with multiple possible origins. Elevated methane concentrations may also result from anthropogenically induced pathways between the deep and shallow subsurface caused by oil and gas production. A baseline characterisation of methane occurrence and origin in the subsurface of the Netherlands was made using a large set of methane concentrations in shallow groundwater (n = 12,219, up to 500 mbgs). Additionally, targeted sampling (n = 40) was carried out in (1) the shallow aquifers at locations where the presence of thermogenic methane was deemed most probable, such as above faults and known gas reservoirs, (2) deep groundwater aquifers below the depth of Neogene and Paleogene marine clays that form the hydrogeological base in the country and (3) geothermal formation waters at 1640–2625 mbgs. Median methane concentrations in shallow aquifers are relatively high from an international perspective (0.2 mg L−1). The highest methane concentrations (up to 120 mg L−1) are attributed to reactive organic matter in Holocene deposits and Pleistocene marine and glacial formations. However, elevated concentrations are also found at greater depth (100–160 m bgs) in Pleistocene aquifers in the eastern and southern inland areas of the Netherlands. Isotopic evidence and gas composition of naturally occurring methane indicate that methane in the targeted samples from shallow aquifers was of biogenic origin, and that methanogenesis predominantly occurs via CO2 reduction. Only trace amounts of methane (<0.2 mg L−1) were observed in the deep groundwater aquifers. A combination of methane and ethane isotopic composition showed that this methane consists of varying fractions of both biogenic and thermogenic origin. Methane in the geothermal reservoirs has an oil associated thermogenic origin. Overall, these findings highlight that future observations of thermogenic methane in Dutch shallow groundwater (post-Paleogene) are most probably linked to anthropogenically induced connections with the deep subsurface.

Groundwater is a vital resource for various water users in the Netherlands. However, due to a changing climate, increasing water demand and changes in the water system, the country is increasingly exposed to groundwater droughts. Water managers use various indicators and statistics to identify groundwater droughts. These indicators characterise the drought for example in terms of intensity, duration and probability of occurrence. Often, these indicators require information on long-term average groundwater conditions and extreme situations that can occur over long periods. However, the availability of long-term groundwater observations of more than ten years in length is limited. Particularly, extreme groundwater drought events are ill-described and subject to large uncertainty in their characterisation. This study explores a novel method for obtaining long-term phreatic groundwater levels by combining a data-driven time series model using transfer function-noise modelling with detrended historical meteorological time series representing the current climate. The method is applied to an area in the Netherlands to generate groundwater levels for the period 1910–2022. Our results reveal differences in the characterisation of groundwater droughts when the extended groundwater time series are compared with observations of a limited duration (eight years). Using the 2018 summer drought event as an example, we find that the probability of this groundwater drought occurring is approximately once every twelve years, based on the eight-year observation period. However, this probability reduces to a once every 24-year event when using historically generated groundwater time series to characterise the groundwater drought. We conclude that characterising droughts with the extended groundwater time series based on historical meteorological data can provide a more comprehensive insight into the intensity and frequency of groundwater droughts, as well as the probability of occurrence of current groundwater levels. Hence, the proposed method supports water managers in establishing return period-based criteria for measures, such as deciding when to implement irrigation bans.

Monitoring groundwater levels and soil moisture content (SMC) is crucial for managing water resources and assessing risks, but can be challenging, especially over large acreages. Recent advances in geophysical methods provide new opportunities for accurate groundwater assessment. Seismic wave speed data, sensitive to changes in pore water pressure, can be used in a passive monitoring approach, while electrical conductivity data can be used for monitoring SMC. Combining seismic and electromagnetic induction (EMI)-based monitoring techniques enhances our understanding of groundwater dynamics. Seismic methods enable wide spatial coverage with moderate depth resolution, whereas EMI offers high-resolution, rapid data acquisition, particularly effective for shallow subsurface monitoring. Integrating these approaches can leverage the strengths of each, yielding comprehensive, high-resolution insights into dynamic subsurface hydrological processes. Integrating these approaches allows for improved groundwater monitoring, aiding in better understanding and managing droughts in regions like the Netherlands.

Past hydrogeological processes and human impacts may exert substantial memory effects on today’s groundwater systems. Thorough characterization of such long-term processes is required for scientists and policymakers to predict the hydrogeological impacts of land management options. Especially in data-scarce areas, historical data are essential to unravel long-term hydrogeological processes, which could not be identified by short-term fieldwork or model simulations alone. However, historical data are often overlooked or only used as background information in most hydrogeological studies. We show that the combination of historical reports and quantitative data yields major insights in the hydrogeological system of Curaçao, a small semi-arid Caribbean island. Reconstructing the island’s groundwater conditions over the past 500 years revealed that deforestation and excessive abstraction has had a detrimental effect on the island’s groundwater reserves. Historical notes and data revealed major signs of seawater intrusion, especially during abstraction peaks in the island’s industrial era. Intrusion effects are still observed locally on the island today, but additional groundwater recharge by waste water has caused freshening elsewhere. We hypothesize that the observed aquifer replenishment locally enhances submarine groundwater discharge, flushing accumulated nutrients and pollutants towards Curaçao’s fringing coral reefs. We expect that this study’s insights motivate more hydrogeologists to use historical reports and data in future studies.