The main objective of this paper is to give an overview of the risks seen in the exploration and production of geothermal energy from the viewpoint of the regulator. The risks are categorised as conventional risks, ultra-deep risks and enhancing factors. These risks are similar to those seen in the oil and gas industry, but the maturity of the geothermal sector in terms of managing such risks is much lower.

Another objective of this paper is to discuss how these risks are managed and mitigated by the sector and the supervisor, State Supervision of Mines (SodM). Portfolio operators developing multiple projects, using skilled employees and embracing continuous improvement are seen as the way forward for the sector to grow safely and sustainably.

This paper concludes that positive developments have started, but a lot of work still needs to be done to ensure safe growth of the geothermal energy sector.

Around 800 AD the peatlands around Amstelland were drained by two rivers. The ‘northern’ Amstel discharged surplus water directly into Lake Almere, which from the 12th century onwards was enlarged to form the Sudersee (in Dutch: Zuiderzee). The ‘southern’ Amstel was a near-abandoned westernmost arm of the River Vecht discharging the poorly drained borderland around the river Vecht into Lake Almere/the Sudersee. As part of the reclamation of peatlands associated with agricultural activities between the end of the 10th and the mid-13th centuries, the rivers were connected via a canal, thus creating the river Amstel, as it is known today.

Two papers (Jansen et al., 2004a, b) in the Netherlands Journal of Geosciences deal with the age and geometry of the Maassluis Formation of the Netherlands. Age estimates are derived mainly from strontium (Sr) isotope measurements (Jansen et al., 2004a). Based on a combination of methods, but most heavily relying on Sr data and sequence boundaries ages based on the Haq curve, the authors (in Jansen et al., 2004b) discuss the possible occurrence of hiatuses in the Maassluis Formation covering intervals of 0.04 to 0.18 Ma.

This paper deals with production and pricing policies for the Groningen gasfield. It will provide an evaluation of the past and a view to its future in a liberalized European gas market. The lifelong production potential and high productivity of the Groningen gasfield is unique. The extremely low-cost field is also unique in the sub-optimal manner in which it has been exploited over the whole of its forty year life to date. Its initial monopolistic situation in the West European energy economy created an opportunity for its development to be limited to production levels, whereby super-normal profits were generated on high value sales at the cost of consumers’ welfare.

The breach in the monopoly, through competition from Soviet gas, readily able to undercut Groningen prices, posed a serious threat both to unit values and market expansion. Fortunately, the fortuitous 1973/4 international oil supplies and pricing crisis restored Groningen’s fortunes. Following the upward price adjustments for foreign sales, the stage was set for achieving high company profits and massive government revenues. Dutch society in a broader sense benefited only indirectly through government tax expenditures. Again, energy consumers’ welfare gains were ignored.

This remains the essence of the situation, pending agreement on the introduction of the liberalized market to meet EU directives. Currently the Dutch gas regime and policy objectives are being adjusted to the requirements of operating in a liberalized market. These changes recognize: first, the invalidity of the government’s long-held fears for gas scarcity in such a way, that the earlier steps to restrict both foreign and national sales have been abandoned, and second, the need to reinstate Gasunie as an active, rather than a passive, player in the European gas market, in which other participants have subverted Gasunie’s earlier dominance.

The second part of the paper will examine, whether and how these changes can be reconciled with the core elements of the Dutch gas policy, i.e. state and private revenues, co-ordination of supply and production, the ‘small fields policy’ and the balancing role of the Groningen field. The liberalization of the European gas market, together with changes in the pattern of supply and demand and stated Dutch policy objectives of energy policy may give rise to conflicts between the interests of the Dutch State, the owners of the field and, again, the consumers.

Previous investigation of isolated landforms, on the eastern margin of the East Anglian Fenland, England, has demonstrated that they represent an ice-marginal delta and alluvial fan complex deposited at the margin of an ice lobe that entered the Fenland during the ‘Tottenhill glaciation’ (termed the ‘Skertchly Line’). They have been attributed, based on regional correlations, to a glaciation during the Late Wolstonian (i.e. Late Saalian) Substage (Drenthe Stadial, early Marine Isotope Stage (MIS) 6). This paper aimed to test this correlation by directly optically luminescence dating, for the first time, sediments found within the Skertchly Line at Shouldham Thorpe, Norfolk, and Maidscross Hill, Suffolk, together with those in associated kame terrace deposits at Watlington, Norfolk. Ages ranged from 244 ± 10 ka to 12.8 ± 0.46 ka, all the results being younger than MIS 8 with some clearly showing the landforms have been subsequently subjected to periglacial processes, particularly during the Late Devensian Substage (∼MIS 2). Most of the remainder fall within the range 169–212 ka and could be assigned to MIS 6, thus confirming the previously proposed age of the glaciation. The local and regional implications of these conclusions are discussed, the maximum ice limit being linked to that of the Amersfoort–Nijmegen glaciotectonic ridge limit in the central Netherlands.

A solitary unprocessed, 26-cm basalt stone recently found at the Roman (69 AD) site at Kotterbos (Lelystad, the Netherlands), situated 40 km north of the Limes, has been examined petrographically and geochemically. The rock is similar to previously investigated Roman basalt stones and blocks from the Limes in the province of Utrecht. All are alkali olivine basalts and basanites, which are also the dominant rock types in the nearby volcanic hinterland in Germany. On the basis of 23 criteria, including all major and minor elements plus a selection of trace elements, the Kotterbos stone correlates with a distinctive subgroup of Limes basalts. This subgroup is characterised by relatively high Mg# and low TiO2 wt% values, as opposed to the other subgroup with lower Mg# and higher TiO2 wt% values. It is argued that the high Mg#–low TiO2 subgroup and the Kotterbos basalt have common geological provenance(s). Five basalt bodies in the hinterland match the criteria of this subgroup, and might be considered as locations of provenance. Of these five, only Rolandsbogen, located next to an ideal anchorage on the west bank of the Rhine, about 12 km upstream from Bonn, can also conform to sensible Roman demands concerning effective logistics and military safety. Consequently, Rolandsbogen is the most likely site of provenance for the high Mg#–low TiO2 subgroup, which includes the Kotterbos basalt. It is argued that the Kotterbos stone is not a rock that somehow got separated from a shipment of building stones to the northern Limes; rather, it is speculated that the stone was picked up as a stray cobble near the basalt body and taken onboard a Roman vessel moored at the Rolandsbogen anchorage.

The Upper Muschelkalk is an unusual reservoir in NW Europe, producing only in the Coevorden Muschelkalk field, onshore the Netherlands. Origin and nature of the gas producing intervals were poorly known. The objective of the paper is to provide a comprehensive description of facies, cyclicity and petrophysical characteristics. From this description a depositional and sequence stratigraphic model is proposed, which explains why there is gas production only from certain intervals of the sequence. Our investigation is based on seismic, core and open hole log data. It indicates that the reservoir consists of dolomites, which are either muddy lagoonal to sabkha, or grainy backshoal deposits. The best reservoir quality is encountered in peloidal-oolitic packstones to grainstones. These represent storm-dominated backshoal deposits and constitute the inner part of a homoclinal carbonate ramp. The succession shows a conspicuous hierarchical cyclicity. Porous backshoal deposits form during maximum transgression and early regression. However permeable, gas producing backshoal deposits only occur in the upper 15 to 20 m, which forms the large-scale regressive hemi-cycle of the Upper Muschelkalk. Better reservoir quality in the upper hemi-cycle is due to changes in grain type and early diagenesis. The investigation might serve as calibration point for further exploring the Upper Muschelkalk reservoir and its facies pattern in the NW European basin.

We investigated the spatial variability of the heavy-mineral composition in the Early Pleistocene fluviatile Kedichem Formation in the Netherlands in order to meet the demand for more information about subsurface sediment composition. We first determined the spatial extension and thickness of the sediment body, then used Fuzzy clustering techniques on a database containing approx. 2000 heavy-mineral counts from the Kedichem Formation to map the spatial extension of the various sediment provenances within the formation. Three clusters could be discerned, one representing a combined Meuse-Scheldt source, the other two representing a mixed Rhine-Baltic source. We made slice maps at several depths through the formation, and plotted the cluster memberships.

The maps show an overall dominance of the Meuse-Scheldt source in the south of the Netherlands, whereas the Rhine-Baltic source occurs mainly in the central Netherlands. The methods employed show that it is possible to map and study the 3-D variation in heavy-mineral composition and hence sediment provenance in the Dutch subsurface with the use of simple statistical and visualization techniques.

This special issue contains the papers presented during the 2004 DEUQUA meeting. The papers provide an overview of recently carried out Quaternary geological studies on different aspects of the river Rhine system. The introductory paper follows the pathway of the Rhine downstream from its source in the Swiss Alps to the delta in the Netherlands. Along this route geological and geographical factors determine the regional subdivisions of the river: the Alps, the Upper Rhine Graben, the Rhenish Massif, and the Lower Rhine Embayment as part of the southern North Sea Basin. Each of these regions can be typified by a characteristic geological evolution.

New evidence from heavy-mineral analyses provides an improved lithostratigraphy and insight in the Quaternary evolution of the Rhine in the Upper Rhine Graben. The Plio-Pleistocene transition is determined by a palaeomagnetic study. The same paper emphasis on the impact of climate change on the composition of the magneto-mineralogy. Pollen analytical results show a complex interrelationship of a number of Middle Pleistocene interglacial periods in the northern part the Upper Rhine Graben. In the same area geomorphological analysis demonstrates a clear influence of tectonics on the preservation of fluvial terrace accumulations. A detailed pollen analytical study on the Late Glacial and Holocene development of the Rhine in the northern Upper Rhine Graben discusses the relation between vegetation cover and river behaviour. Finally, two papers from the Lower Rhine Embayment discuss a revised provenance based lithostratigraphy and its implications for understanding the fluvial history.

Within the collaborative research centre SFB350 at the University of Bonn a component software called GeoToolKit has been developed, which is intended to facilitate the design and implementation of 3D/4D geological applications. It provides a range of geo-oriented software building blocks for application developers involving database management system based spatial and temporal data maintenance, support for efficient spatial and temporal retrieval, communication, visualization and graphical interfaces which the user could assemble in a ready-to-use application. As such, GeoToolKit is not a GIS-in-a-box package - rather it is a library of C++ classes that allows the incorporation of spatial functionality within an application under development. It is primarily oriented towards software engineers with the C++ experience involved in the development of specialpurpose geological applications, which can hardly be modelled within standard GISs. We present applications using GeoToolKit, which have been developed to support the geological reconstruction of the Lower Rhine Basin.

A specimen of the Early Cretaceous amiiform fish Calamopleurus cylindricus with stomach content is described from the Santana Formation, Brazil. The prey concerns a smaller conspecific individual. Until now, prey items documented for Calamopleurus almost exclusively involved the aspidorhynchid Vinctifer. On the basis of the present record it is suggested that the prey preference of Calamopleurus was less pronounced than previously assumed.

The deposits of the Rhine and the Meuse in the Netherlands alternate intheir delta in a complex way. This paper discusses a method to distinguishthe deposits of the Rhine and the Meuse based on the differences in naturalradioactivity of 40K, 238U and 232Th, andthe effect of the age of the deposits on the radiometrie signal. In total,six channel belts of the Rhine and the Meuse were selected for sampling withan approximate age of about 2000, 4000 and 6000 14C years B.P. Ofeach channel belt 5 samples of different lithology were taken: clay (C),clay leads (CL), sandy clay loam (sCL), sandy loam (sL) and sand (S). Allsamples were analysed on organic matter content, grain size, geochemistryand radioactivity of the radionuclides 40K, 238U and 232Th. The radioactivity of the sample is mainly influenced bythe grain size of the sample. Therefore, this signal is divided in partialradioactivities for three grain size fractions – clay (<16 μm), silt (16– 63 μm) and sand (>63 μm) – to make the radiometric fingerprint, whichis independent of the grain size of the sample. These fingerprints show adifference between the Rhine and the Meuse. Additionally, the radiometricsignal strongly depends on the age of the deposits. Remarkably, this trendwith age is opposite in the deposits of the Rhine and the Meuse and oppositein the clay and silt fraction. Because the radiometrie differences betweenthe samples seem more distinct than the geochemical differences, theradiometric fingerprints are more suitable to distinguish the deposits ofthe Rhine and the Meuse. A method is presented to derive the contribution ofthe Rhine and the Meuse in a deposit of unknown origin, assuming that theradiometric fingerprints found are consistent and valid for the Rhine-Meusedelta. To distinguish the deposits of the Rhine and the Meuse, both thegrain size composition and the age of the deposits have to be known.

This paper reports the discovery of an in-situ striated, far-travelled, oversized clast in the Ardleigh Gravels of the Kesgrave Sands and Gravels of the River Thames at Ardleigh, east of Colchester in Essex, eastern England. The morphology, petrography and geochemistry of the clast, and the sedimentology of the host deposit are described. The striations are interpreted, on the basis of their sub-parallelism and the shape and sub-roundedness of the clast, as glacial and the clast is provenanced to Ordovician rocks of the Llŷn and Snowdonia regions of North Wales. On the basis of clast frequency within the Colchester Formation gravels of the Kesgrave Sands and Gravels it is inferred that glaciers reached the Cotswold region of the Thames catchment. Floe-ice transport during spring flood is invoked for movement from the glaciated region to eastern England. The paper discusses the possible age of the glaciation and recognises that it is difficult to be more precise than a cold stage in the early Middle Pleistocene (MIS 18, 16 or 14). Attention is drawn to the possibility of glaciation associated with a diamicton in the region of the Cotswold Hills known as the Bruern Till, but stresses the need for new work on this deposit.

Discussions on the age and the depositional environments of the Veldhoven Formation and its members are persistent in Belgium and the Netherlands. Uncertainties on stratigraphy and the constructive process of sediment accumulation continue today as a result of lack of data on this succession within the Roer Valley Rift System. The present study provides new information on the bio- and lithostratigraphy and facies from two boreholes based on dinoflagellate cyst taxa. The results were correlated by gamma-ray logs towards other key boreholes in the region and show a good consistency for stratigraphy and depositional environments for the members of the Veldhoven Formation.

After marginal to restricted marine conditions in the latest Rupelian (early Oligocene), the start of deposition of the Veldhoven Formation marked the transition towards a higher sea level, expressed by increased glauconite contents and gamma-ray values. The Voort Member in the lower part of the Veldhoven Formation has an early to late Chattian (Late Oligocene) age and comprises predominantly shallow marine (fluctuating restricted to open marine) conditions. The lithology in the lower part of this unit is often very clayey but is coarsening upward into sands. The superjacent Wintelre Member has a latest Chattian to early Aquitanian (early Miocene) age. This member is distinct by its clayey nature which is expressed by relatively high gamma-ray values. Earlier studies suggest a deeper marine facies for the Wintelre Member compared to the Someren and Voort members. However, the dinoflagellate cyst assemblages in this unit are mostly dominated by a single genus indicating a restricted marine setting, including salinities that deviate from normal marine conditions, most probably due to minor ventilation by narrow or lack of connection to the Atlantic Ocean. A glacio-eustatic sea-level fall around the Oligocene/Miocene boundary limited the sea coverage to the strongest subsiding areas, where deposition of the Wintelre Member is recorded, while non-deposition or erosion occurred in the surrounding highs, hence creating an isolated (sub)basin. The superjacent Someren Member was deposited during the late Aquitanian to middle Burdigalian and consists of shallow to open marine clayey fine sands. Increasing clay contents indicate a gradual development towards a higher sea level, which coincide with upward increasing gamma-ray values.

The biostratigraphic results of this study suggest that no major hiatuses are present in the differentially subsiding blocks of the Roer Valley Rift System during the late Oligocene to early Miocene.

Recent measurements of the chemical and isotopic composition of lunar samples indicate that the Moon's bulk composition shows great similarities with the composition of the silicate Earth. Moon formation models that attempt to explain these similarities make a wide variety of assumptions about the properties of the Earth prior to the formation of the Moon (the proto-Earth), and about the necessity and properties of an impactor colliding with the proto-Earth. This paper investigates the effects of the proto-Earth's mass, oblateness and internal core-mantle differentiation on its moment of inertia. The ratio of angular momentum and moment of inertia determines the stability of the proto-Earth and the binding energy, i.e. the energy needed to make the transition from an initial state in which the system is a rotating single body with a certain angular momentum to a final state with two bodies (Earth and Moon) with the same total angular momentum, redistributed between Earth and Moon. For the initial state two scenarios are being investigated: a homogeneous (undifferentiated) proto-Earth and a proto-Earth differentiated in a central metallic and an outer silicate shell; for both scenarios a range of oblateness values is investigated. Calculations indicate that a differentiated proto-Earth would become unstable at an angular momentum L that exceeds the total angular momentum of the present-day Earth–Moon system (L0) by factors of 2.5–2.9, with the precise maximum dependent on the proto-Earth's oblateness. Further limitations are imposed by the Roche limit and the logical condition that the separated Earth–Moon system should be formed outside the proto-Earth. This further limits the L values of the Earth–Moon system to a maximum of about L/L0 = 1.5, at a minimum oblateness (a/c ratio) of 1.2. These calculations provide boundary conditions for the main classes of Moon-forming models. Our results show that at the high values of L used in recent giant impact models (1.8 < L/L0 < 3.1), the proposed proto-Earths are unstable before (Cuk & Stewart, 2012) or immediately after (Canup, 2012) the impact, even at a high oblateness (the most favourable condition for stability). We conclude that the recent attempts to improve the classic giant impact hypothesis by studying systems with very high values of L are not supported by the boundary condition calculations in this work. In contrast, this work indicates that the nuclear explosion model for Moon formation (De Meijer et al., 2013) fulfills the boundary conditions and requires approximately one order of magnitude less energy than originally estimated. Hence in our view the nuclear explosion model is presently the model that best explains the formation of the Moon from predominantly terrestrial silicate material.

Two specimens of a pachydiscid ammonite, a fragmentary silicified phragmocone from the Kunrade Limestone facies at Kunrade (Schunck), and a partial external mould preserved in flint from the Nekum Member (both Maastricht Formation, Belemnitella junior Zone of authors) at the former Blom quarry (Berg en Terblijt), are identified as Pachydiscus (P.) noetlingi Kennedy, 1999, a species previously known only from the Upper Maastrichtian of Baluchistan (Pakistan). This new record underscores the proposal of incursions of Tethyan biota into the type area of the Maastrichtian Stage, previously documented for other groups, including echinoderms and bivalves, as well.

The spatial distribution of porosity and permeability of the Rupel Clay Member is of key importance to evaluate the spatial variation of its sealing capacity and groundwater flow condition. There are only a limited number of measured porosity and permeability data of the Rupel Clay Member in the onshore Netherlands and these data are restricted to shallow depths in the order of tens of metres below surface. Grain sizes measured by laser diffraction and SediGraph® in samples of the Rupel Clay Member taken from boreholes spread across the country were used to generate new porosity and permeability data for the Rupel Clay Member located at greater burial depth. Effective stress and clay content are important parameters in the applied grain-size based calculations of porosity and permeability.

The calculation method was first tested on measured data of the Belgian Boom Clay. The test results showed good agreement between calculated permeability and measured hydraulic conductivity for depths exceeding 200m.

The spatial variation in lithology, heterogeneity and also burial depth of the Rupel Clay Member in the Netherlands are apparent in the variation of the calculated permeability. The samples from the north of the country consist almost entirely of muds and as a consequence show little lithology-related variation in permeability. The vertical variation in permeability in the more heterogeneous Rupel Clay Member in the southern and east-southeastern part of the country can reach several orders of magnitude due to increased permeability of the coarser-grained layers.

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.

A fragmentary and partially dissociated arm of an astropectinid starfish, assigned to the genus Astropecten Gray, 1840, is recorded from decalcified and limonitised, fine-grained sandstone concretions and slabs of late Miocene (Tortonian) age, collected from the former gravel and sand pit ‘de Hoogdonk’ near Liessel, province of Noord-Brabant. Added are two examples of the ichnofossil Asteriacites lumbricalis von Schlotheim, 1820, both preserved in convex hyporelief and co-occurring with other, indeterminate traces. Although astropectinids have been recorded previously from Miocene and Pliocene deposits in the Netherlands, the present is the first record of fossilised traces of starfish.