My first year as Editor-in-Chief of the Netherlands Journal of Geosciences / Geologie en Mijnbouw turned out to be a steep learning curve which showed me all the facets this task brings. It has been a productive year, though. A total of 49 papers were published in three regular and two special issues. The special issues, on the Meuse Valley and on Seismicity of the Groningen Gas Field, were well received and contain papers authored by members of academic and applied institutions, including universities, consultants, advisory institutions, provinces, energy operators and regulatory authorities. This once again proves that thematic issues are a great strength of the Journal and it is good to notice that the Journal has become a medium for a broad geoscientific research community.

Flooding of the southern part of the North Sea occurred between 9000 and 8000 BP, when the rate of relative sea-level rise was on the order of 0.7 cm per year for the Dover Strait Region and 1.6 cm per year for the area north of the Frisian Islands, forcing the shoreline to recede rapidly. When relative sea-level rise decelerated after 7000 BP for the Belgian coast and 6000 BP for the central Netherlands coast, sediment supply by the tidal currents balanced the creation of accommodation space in the estuaries and other back-barrier basins. Consequently, the barrier started to stabilize, and the tidal basins and their inlets silted up. Between 5500 and 4500 BP, the Belgian coastal plain changed into a freshwater marsh with peat accumulation, and the same happened 500–1000 years later in the western provinces of the Netherlands. The E-W running barrier/back-barrier system of the Frisian Islands in the northern Netherlands stayed open until today, however, because of lower sediment supply.

The period between 4000 and 2000 BP was relatively quiet due to the strong deceleration of the rate of sea-level rise; peat cushions developed behind the barriers, which were straightened by erosion of the headlands. Major and often catastrophic flooding occurred in the Middle Ages, when the estuaries in the southwestern part of the Netherlands formed.

About 226 (± 15%) × 109 m3 sediment, mostly sand, is stored in the barriers and back-barrier basins of the Netherlands, 70% of which was deposited prior to 5000 BP. About 10% of the stored sediment is estimated to be of alluvial origin. Most of the sediment is derived by the erosion of the Pleistocene basement during recession of the barriers, but tide-induced crossshore transport from the North Sea forms an additional source for the barriers and back-barriers of the west-facing coast of the Netherlands.

This paper presents new geological data from two terp excavations at Englum and Ezinge, in the Dutch province of Groningen, and compares them to similar data from the western part of Friesland, in particular from the terp of Wijnaldum-Tjitsma. This terp is situated at a salt marsh ridge of the same height and thickness as Englum and Ezinge, although habitation started 650 years later at Wijnaldum. The measured levels of the tidal-flat/salt-marsh boundary underneath these terps make it possible to reconstruct palaeo-Mean High Water (MHW) levels. These sea-level index points show that palaeo-MHW in the Groningen part of the Wadden Sea was at the upper limit of the range of palaeo-MHW that has been reconstructed for the Dutch Wadden Sea on the basis of data from its western part. The deviating levels indicate that there are differences between regions of the Wadden Sea; this has earlier been established for the German section of the Wadden Sea. In the eastern part of the Dutch Wadden Sea, MHW nowadays is considerably higher than in the western part of the Wadden Sea; the data suggest that this may have been the case already in the 1st millennium BC. Salt marsh levels under dated terp layers make it possible to establish the rate of sedimentation of the developing salt marsh, at 23–91 cm per century for the pioneer zone and low marsh. This rate of development slowed to 4–5 cm per century for the middle marsh and 3–4 cm per century for the high salt marsh.

This study presents the 3-D geometry of the Oligocene Rupel Clay Member and a review of its depositional environment based on new and published data. The Rupel Clay Member (RCM) is a clay layer in the Dutch subsurface which is informally known as the Boom Clay. New depth and thickness maps show that the member is present in nearly the whole subsurface of the onshore Netherlands to a depth of about 1500 m. The thickness of the member is variable but rarely exceeds 125 m. We identified three subunits: RCM-U, with a thickness of 15–40 m; RCM-M, with a thickness of 40–90 m; and RCM-L with a thickness of 25–50 m. The Rupel Clay Member is not a homogeneous clay; both vertical and lateral grain-size trends are present. These trends match with general palaeogeographic trends which foresee near-shore facies in the south and southeast of the onshore Netherlands and a more distal setting when moving northward. The three subunits are correlated with global climatic and regional tectonic events, which have mainly affected marginal facies. Faults are known to cut through the clay layer, but have not been mapped. A mismatch of lithostratigraphic nomenclature between the Netherlands and neighbouring countries is present. Part of the solution for this mismatch lies in the proper interpretation of well data in the Netherlands, both on- and offshore.

An inventory of the available surficial data on active faults in Italy has been compiled by gathering all the available information on peninsular Italy (project by CNR, National Group for the Defense against Earthquakes), the central-eastern Alps and the Po Plain (EC ‘PALEOSIS’ project). Such information has been summarised in maps (reporting surficial expressions of faults with length L≥11 km) and in a table where fault parameters relevant for seismic hazard assessment (e.g. slip rates, recurrence intervals for surface faulting events, etc..) have been reported. Based on the geological characteristics of the Italian territory, a fault has been considered as active if it shows evidence of Late Pleistocene-Holocene displacements. Active faults in Italy are distributed throughout the entire Apennine chain, in the Sicilian and Calabrian regions and in some Alpine sectors, but knowledge is not homogeneously distributed through the territory. The largest amount of data is related to the central Apennines. In contrast, fault geometries and parameters are less well defined in the southern Apennines, Sicily and Calabria, where investigations have started more recently. Knowledge is sparse in the northern Apeninnes, where data necessary to define fault parameters are lacking and also the chronology of the activity has to be considered cautiously. Abundant blind faulting in the Po Plain hinders the detection of active faults by means of the classical surficial investigations and therefore the present knowledge is limited to the Mantova fault. Blind faults and the peculiar recent geological history of the Alpine areas, which is strongly conditioned by the erosional and depositional activity during and after the last glacial maximum, also hinder the identification of active faults in the central-eastern Alps. Some faults in this Alpine sector are believed to be active, but data on their segmentation are still missing. Available information indicates that Italian active faults are usually characterised by slip rates lower than 1 mm/yr. Recurrence intervals for surface faulting events are longer than 1,000 years in the central and southern Apennines. This review on the Italian active faults represents the first step to produce a map of the major seismic sources in Italy, which in turn will result from the merge of surficial data with seismological and geological subsurficial data. The available knowledge gathered in this paper indicates those areas where data are presently sparse. It should be, therefore, possible to better plan future geomorphological and paleoseismological investigations.

Two sections, just below the Nivelle Horizon in the upper Gulpen Formation (Upper Maastrichtian), and seven kilometres apart (CBR-Lixhe and ENCI-Maastricht bv quarries) have been analysed (samples every 5 cm) for dinocyst, pollen grains and bioclast contents as well as for carbon and oxygen isotopic composition, to obtain better insight into the influence of weathering on these sediments. The CBR section lies above groundwater level, while that at the ENCI quarry is some metres below. At the former quarry we recognised the influences of weathering (karst) nearby.

At ENCI, palynological, bioclast and stable isotope results of the carbonate phase (mainly consisting of coccoliths) co-vary remarkably, displaying two cycles which may be interpreted tentatively as climatic fluctuations. The ∂18O curve varies roughly between −1.6‰ and −1.1‰ (on PDB scale), corresponding to a temperature change of about 2°C. Less negative values (i.e. cooler seawater) coincide with larger amounts of pollen of Normapolles and Triporates type assumed to represent temperate forest elements of a vegetation also containing tropical elements such as palms. Assuming the 5 cm sample intervals at ENCI to correspond to 1 ka, climatic maxima (and minima) may be 20–25 ka apart, obviously recalling Milankovitch precession cycles.

These are independent of a sharp sedimentological change noted in the upper part of the lowest cycle (samples 42 to 24). Upwards of sample 42, bioclast contents increase and dinocysts, Spiniferites in particular, decrease significantly, corresponding to a marked shallowing. This turning point is also recorded in the ∂13C curve at ENCI. Bioclast percentages appear to follow composite trends that are influenced by both climatic and sedimentological conditions.

Mosasaur taxa currently known from Campanian-Maastrichtian strata in the Liège-Limburg (SE Netherlands, NE Belgium) and Mons (southern Belgium) basins are listed and briefly discussed and their stratigraphic ranges indicated. Recently published and/or ongoing work on coleoid and ammonoid cephalopods in these areas allows tie points between NW Europe and the United States (Western Interior, Gulf Coast, Atlantic Seaboard) to be established. Future studies need to refine the resultant, rather crude, scheme. The ultimate aim is a more robust picture of mosasaur taxonomy, biostratigraphy and palaeobiogeography, and a detailed evaluation of migratory patterns across the Atlantic.

Besides the Oligocene Boom Clay, the Ypresian clays – part of the Eocene Ieper Group (Kortrijk Formation and Kortemark Member) – are currently being investigated as an alternative host rock for the deep geological disposal of radioactive waste in Belgium and the Netherlands. In this study, broad-ion-beam milling and high resolution scanning electron microscopy (BIB-SEM) analyses were carried out to analyse the mineral fabrics and microstructures of representative Ypresian clay samples from different depths of the ON-Kallo-1 borehole (Kallo, Belgium). Qualitative microstructural observations indicate that mineral fabrics and pore morphologies in fine-grained samples are comparable to those found for fine-grained Boom Clay, but most of the Ypresian clay samples analysed also contained a significant silt fraction, which is associated with larger inter-aggregate pores, coated by a thin, very low porous clay layer. Quantitative pore-shape analysis shows lower axial ratios and elongations, as well as higher roundness and circularities for pores in the clay matrix of the more coarse-grained samples, compared to the fine-grained samples. The contribution of large pores (>1 × 107 nm² pore area) to the total BIB-SEM observed porosity was found to correlate with the non-clay mineral (NCM) content of a sample. Frequencies of pore sizes within the clay matrix follow a power-law distribution, hinting towards the possibility of up-scaling of the nanometre-scale observations to larger scale (micro-) structural features of the material. Power-law exponents are comparable to values found for power-law pore-size distributions within the clay matrix of the Boom Clay, which indicates similarity of the pore-space morphologies within the clay matrix of the Boom Clay and the Ypresian clays. Wood's metal injection, followed by (cooled BIB)-SEM analysis shows that all visible pores are connected via pore throats of diameter down to ~10 nm.

A groundwater model was set up to study far-field transport for the potential of a radioactive waste repository the Boom Clay in the Netherlands. The existing national groundwater model, the Netherlands Hydrological Instrument, was extended in the vertical direction to include geological formation up to and beyond the Boom Clay. As the amount of hydrogeological data in the deeper subsurface is limited, simplifications in the model schematisation were necessary. Moreover, nationwide data about the tops and bottoms of many of the deeper geological formations and their members are lacking and required interpolation. Finally, values for hydrogeological parameters, such as porosity and hydraulic conductivity, are also lacking for the deeper formations. These values were estimated using relationships with depth and lithology. Moreover, no quantitative data about heterogeneity within the deeper geological formations or its members were available.

In the Dutch research programme on the geological disposal of radioactive waste (OPERA), the post-closure safety of a generic repository is assessed in either Boom Clay or rock salt. Disposal of Dutch radioactive waste is not foreseen in the next decades and a choice of host rock has not been made. In the early, conceptual phase of the radioactive waste disposal process in the Netherlands no potential repository locations were selected and a groundwater flow model for the entire Netherlands was build. As a starting point a geological disposal facility is assumed to be present at a depth of at least 500 m within a Boom Clay formation of 100 m in order to be able to make an assessment of post-closure safety with this geological formation in a disposal concept. With these assumptions, a general idea of potential flow patterns has been obtained and broken down into pathline trajectories. These trajectories were calculated to achieve input for the potential transport of radioactive isotopes (radionuclides) from this waste in the Netherlands after the closure of a disposal facility in Boom Clay.

The groundwater flow patterns in the deeper subsurface strongly resemble the larger scale flow patterns in the shallow subsurface, with flow from infiltration areas in the east and the south of the Netherlands towards to seepage areas of the polders in the west and the northern part of the country or towards the river valleys of the Rhine and IJssel. Groundwater flow velocities, however, are much lower in the deeper part of the model and consequently travel times are much larger. The conservative travel times from the pathlines range from a few 1000 years to more than 10,000,000 years depending on the location for the repository. Longer travel times are obtained for locations with a downward groundwater flow in the Boom Clay.

Because of the simplifications in the model schematisation and the uncertainty in the model parameters, the present results should only be considered as a first indication. Moreover, the model could not be validated due to a lack of validation data. However, the insight gained with the model may help to design a data collection strategy for dedicated model validation, such as measuring the hydraulic gradient over the Boom Clay to validate downward flow in the Boom Clay to obtain the necessary data for a post-closure safety assessment.

Due to their potential as a petroleum or geothermal system, the Dinantian carbonates of the Netherlands have recently attracted renewed interest because of the identified presence of excellent reservoir properties. This notion contrasts with the general assumption that these carbonates are tight. Therefore, in order to give the current knowledge state, this paper re-examines the sparse publicly available well and seismic data and literature to assess the distribution and reservoir properties of the Dinantian carbonates.

Dinantian carbonate deposition occurred throughout the study area (southern onshore and offshore of the Netherlands and northern Belgium), which is situated on the northern margin of the London–Brabant Massif, progressively onlapping the latter structure. This study confirms the presence of three carbonate facies types in the study area: a Tournaisian low-gradient carbonate ramp system, succeeded by a succession in which the carbonate ramp system evolved to a rimmed shelf setting. Subsidence of the northern margin of the London–Brabant Massif resulted in a landward shift of the shallow-marine facies belts, while the formation of normal faults resulted in a ‘staircase’-shaped shallow-water platform–slope–basin profile, associated with large-scale resedimentation processes. After deposition, the limestone deposits were frequently exhumed and reburied. A first period of regional exhumation occurred at the end of the Dinantian, which seems to be associated with porosity-enhancing meteoric karstification, possibly limited to the palaeo-shelf edge. The most intense alterations seem to be present as a deep leached horizon below the Cretaceous unconformity at the top of the Dinantian sequences. In addition, clear evidence for hydrothermal fluid migration is found locally, enhancing reservoir properties at some places while occluding porosity at others. The timing of these phases of hydrothermal fluid circulation is poorly understood.

Whereas in the United Kingdom hydrocarbons have been produced from karstified Dinantian carbonates, this petroleum play has received little attention in the Netherlands. This paper shows that, also for the Netherlands, a karstic reservoir probably existed before the start of hydrocarbon generation from the onlapping basal Namurian shales. The hydrocarbon prospectivity of these sediments, however, is primarily controlled by the presence of both a karst-related reservoir and migration routes from a decent-quality source rock. Two geothermal projects producing from this reservoir in the southern onshore Netherlands have shown the potential of the Dinantian carbonates for ultra-deep geothermal projects. To conclude, the findings presented herein are relevant for studies of the hydrocarbon prospectivity and studies of the geothermal potential of Dinantian carbonates in the Dutch on- and offshore.

Ever since the first mosasaur restorations were published, these extinct marine reptiles have been pictured with either notched, forked or undivided tongues. Here, we present an overview of existing iconography, a review of the previous literature, and we discuss how best to reconstruct tongue form in mosasaurs. Despite disagreement about their precise phylogenetic position, most authors consider mosasaurs members of the Varanoidea, derived anguimorphans including Helodermatidae, Varanidae, Lanthanotus and probably snakes. All anguimorphans share a diploglossan (two-part) tongue, in which the foretongue is derived and modified into a highly protrusible chemosensor, while the hindtongue is plesiomorphic, retaining well-developed papillae, mucocytes and robust posterior lobes. We suggest that mosasaurs had a diploglossan tongue that remained in a relatively underived state. The form of the tongue would probably have been most like modern Heloderma or Lanthanotus with a protrusible chemosensory foretongue and a plesiomorphic, papillose hindtongue. Such a tongue is consistent with well-developed vomeronasal chemoreception through tongue-flicking, with the retention of the ancestral function of hyolingual food transport and swallowing following jaw-prehension of prey. The presence of paired fenestrae in the palate associated with the vomers, as well as the presence of pterygoid teeth are in accordance with such a tongue form in mosasaurs.

The Proterozoic basement of Suriname consists of a greenstone–tonalite–trondhjemite–granodiorite belt in the northeast of the country, two high-grade belts in the northwest and southwest, respectively, and a large granitoid–felsic volcanic terrain in the central part of the country, punctuated by numerous gabbroic intrusions. The basement is overlain by the subhorizontal Proterozoic Roraima sandstone formation and transected by two Proterozoic and one Jurassic dolerite dyke swarms. Late Proterozoic mylonitisation affected large parts of the basement. Almost 50 new U–Pb and Pb–Pb zircon ages and geochemical data have been obtained in Suriname, and much new data are also available from the neighbouring countries. This has led to a considerable revision of the geological evolution of the basement. The main orogenic event is the Trans-Amazonian Orogeny, resulting from southwards subduction and later collision between the Guiana Shield and the West African Craton. The first phase, between 2.18 and 2.09 Ga, shows ocean floor magmatism, volcanic arc development, sedimentation, metamorphism, anatexis and plutonism in the Marowijne Greenstone Belt and the adjacent older granites and gneisses. The second phase encompasses the evolution of the Bakhuis Granulite Belt and Coeroeni Gneiss Belt through rift-type basin formation, volcanism, sedimentation and, between 2.07 and 2.05 Ga, high-grade metamorphism. The third phase, between 1.99 and 1.95 Ga, is characterised by renewed high-grade metamorphism in the Bakhuis and Coeroeni belts along an anticlockwise cooling path, and ignimbritic volcanism and extensive and varied intrusive magmatism in the western half of the country. An alternative scenario is also discussed, implying an origin of the Coeroeni Gneiss Belt as an active continental margin, recording northwards subduction and finally collision between a magmatic arc in the south and an older northern continent. The Grenvillian collision between Laurentia and Amazonia around 1.2–1.0 Ga caused widespread mylonitisation and mica age resetting in the basement.