Nomenclature (Deep)

1. Introduction

The basis for a modern lithostratigraphic nomenclature of the Lower Tertiary, Mesozoic and Palaeozoic was laid in 1980 with the publication of the “Stratigraphic Nomenclature of The Netherlands” by the Nederlandse Aardolie Maatschappij B.V. (NAM) and the Rijks Geologische Dienst (RGD). Five years before, the nomenclature of the Upper Tertiary and the Quaternary had been treated extensively by the authors Doppert et al (1975) of the Geological Survey of the Netherlands in the “Toelichting bij geologische overzichtskaarten van Nederland” Zagwijn and van Staalduinen (1975).

In the years that followed a vast amount of new stratigraphic data became available as a result of the continuing exploration for oil and gas in the Netherlands, both onshore and offshore. Thus, the necessity arose to revise and update the stratigraphic nomenclature.

Publications by Herngreen and Wong (1989) and Herngreen et al (1991a) initiated this operation. In 1990, the RGD decided to coordinate these efforts and initiated a special project to revise and update the litho-stratigraphic nomenclature of the pre-Quaternary of the Netherlands. Financial support was obtained from the Ministry of Economic Affairs.
In order to meet the requirements of the majority of users of the envisaged Nomenclature, reach a general consensus and merge the available expertise, co-operation was sought and obtained from the Netherlands Oil and Gas Exploration and Production Association (NOGEPA) and the Petroleum Geological Circle of the KNGMG (PGK).

This led to the establishment of a Steering Committee as a supervising body, and of eight working groups, covering three specific aspects of the Nomenclature and five consecutive intervals of the stratigraphic column (Table A.1). Thus, scientists from various oil companies, two universities, two consultants and the RGD are cooperating in this project, which started early 1991 and is scheduled to be completed in the course of 1994.

Objectives and scope
The stratigraphic framework established by NAM and RGD in the 1980 Nomenclature served as a basis for the present study. The objectives of the revised and updated nomenclature were:

  • to establish a chronostratigraphic standard to be used for the Netherlands.
  • to identify the main structural elements that are relevant for the stratigraphic development and assign proper names to these elements.
  • to set up a lithofacies scheme and a coding system which can serve as a standard for detailed descriptions of formations, in particular in cores.
  • to retain existing nomenclature as much as possible, but revise and correct older interpretations on the basis of new findings.
  • to formulate new stratigraphic units, paying attention to tectonic setting, depositional environment and age determination.
  • to systematically extend existing lithostratigraphic defi nitions to a comparable degree of detail, separating description from interpretation as much as possible.
  • to demonstrate the link with sequence stratigraphy and eismostratigraphy in cases where this is worthwhile.
  • to show the relationship of Dutch lithostratigraphy with that of surrounding countries.

Basically, the rules for the stratigraphic classification formulated in the International Stratigraphic Guide Hedberg (1976) are followed. In general, a strict distinction between lithostratigraphy and chronostratigraphy is maintained. However, in cases where strong lateral facies changes occur and where clear lithological mark-ers are scarce or absent, biostratigraphy is used to assist correlation. Moreover, where the sedimentary sequence shows a very clear cyclicity, e.g. in the Zechstein, the individual cycles are treated as formations, even though their lithologies are too diverse to qualify as a formation in the sense of the Guide.

Name designations of lithological units do not always follow the “Hedberg” recommendations. This has a two reasons. First, existing names are retained as much as possible and, second, it was tried to avoid a profusion of new names. In addition, it proved difficult to find appropriate topographic names in the offshore area. Thus, the same topographic name is occasionally used for the member as well as for the formation to which it belongs. Furthermore, nearby onshore topographic names have been used for formations that are defined in offshore wells. In one case, for the sake of continuing the accustomed use of existing names, two formations were allowed to have the same topographic name, the lithological affix being the decisive discriminator (Vlieland Sandstone Formation versus Vlieland Claystone Formation).

The codes for the stratigraphic units that are proposed together with the lithological unit names, will effectively prevent erroneous use. We have tried to produce a Nomenclature which is as concise as possible and which will prevent confusion. The nomenclatoral system attempts to show the coherence of the lithologic units. Over-subdivision of units is avoided. Generally, the number of hierarchical levels is restricted to three. The system is devised in such a way that users can easily extend it with in-house stratigra-phies for local use (e.g. field studies).
The section on the Upper Jurassic and Lower Cretaceous contains the most exhaustive, elaborated unit descriptions. This is due to the complex geological setting of the deposits combined with ample well and seismic control and good biostratigraphic dating.

The results of the Working Group on Lithofacies are published separately Reijers et al (1993), because their recommendations are more a specific approach to sediment description than to definition and description of lithostratigraphic units.
The final products of the other working groups will be completed at different times. In order to make the results available as soon as possible, it was decided to publish completed sections as soon as they are ready, preferably batchwise, in a loose-leaf binder. This has the added advantage that any later updates can easily be inserted into the volume.

A large number of institutions and persons have contributed to the production of this publication.
The support of the NOGEPA and in particular the oil companies Amoco Netherlands Petroleum Company, Chevron Oil Company of The Netherlands, Clyde Petroleum Exploratie B.V., Continental Netherlands Oil Co., Elf Petroland B.V., Mobil Producing Netherlands Inc., Petrofina S.A., Placid International Oil, Ltd., Statoil Netherlands B.V., Unocal Netherlands B.V. and Winters-hall Noordzee B.V. is gratefully acknowledged. Special thanks are extended to the Nederlandse Aardolie Maatschappij B.V., who took the initiative to involve the NOGEPA in the project, contributed in all working groups and supplied a large amount of unreleased onshore well data.

We are especially indebted to the company participants in the various working groups, and those from GAPS Nederland B.V., International Geoservices B.V., the Petroleum Geologische Kring, the Technische Universiteit Delft and the Vrije Universiteit van Amsterdam.
The stimulating contacts and discussions on the stratigraphic nomenclature with colleagues of the geological surveys of Belgium, Denmark, Germany and the United Kingdom are gratefully acknowledged.

The Ministry of Economic Affairs is thanked for its financial support enabling us to secure the invaluable input of Drs. W.F.P. Kouwe (InterGeos) and afford publication of the final document. Large parts of the text were written by Mr. Kouwe and the chairmen of the working groups. Drs. T. van de Graaff-Trouwborst took care of the final correction and editing of the English text, Drs. J. Vastenhouw prepared most of the type sections and Mr. J.A.M. Bruinenberg supervised the layout of this publication.
Finally, the director of the Geological Survey of The Netherlands (RGD) is acknowledged for allowing part of his staff to work on the “Nomenclature Project” for a considerable time as well as for his permission to publish the results.

1.1 Sequence stratigraphy

The study of genetically related facies within a frame-work of chronostratigraphically significant surfaces is known as ‘sequence stratigraphy’ Van Wagoner et al (1990). The basic unit, the sequence, is considered to have formed during one ‘cycle’ of rising and falling relative sea level. Such sea level movements are cyclic, i.e. with-out beginning or end, but the produced deposits tend to display clear unconformities, formed at the moment of the maximum rate of sea-level fall. These unconformities (and their lateral correlatives) are taken as the sequence boundaries.
The other main point of reference in the cycle of sea level movements is the moment of the maximum rate of relative sea-level rise. This moment is reflected in deposits by the maximum extent of basin sediments, and is therefore called the maximum flooding surface. The sequence can now be subdivided into the periods between these two reference levels, called systems tracts.

Most sequences are built up of smaller shoaling sequences. These are the parasequences of Van Wagoner et al (1990). The parasequences contained in a sequence can be grouped into a number of associated parasequence sets, each demonstrating its own parasequence stacking type. Each parasequence set is formed during a certain part of the sea-level cycle or systems tract.
Parasequences are formed by shorter-term sea-level fluctuations, superimposed upon the cycle-forming sequences in an analogous fashion.

Sedimentary facies belts shift in response to sea-level movements (linked to climatic changes), sediment input, existing topography, and subsidence patterns. The interaction of topography, subsidence and sea level movements results in accommodation space, which is space available to be filled with sediment at a specific place and moment in time.
This results in constant short-term changes in accommodation space, climate and sediment input, superimposed on a more gradual tectonic subsidence.
During a complete sea-level cycle (sequence and parasequences) these changes will mould the existing depositional setting configuration (palaeogeography). The various shifts in facies resulting from sea-level changes can serve as a tool for regional correlation, because they follow time surfaces.

The mechanism behind the relative sea-level movements is still a matter of debate. Many authors feel that it could be largely eustatic. This implies that the boundaries of the eustatic cycles would coincide globally. On the basis of this principle, the Haq et al (1988) sea-level chart was produced. This chart combines a synthesis of many regional sequence stratigraphic zonations with a wealth of bio-, magneto- and chronostratigraphic zonations.
The data of this chart are incorporated the chronostratigraphic table which is enclosed in the section on Chronology and Chronostratigraphy.

Sometimes serious discrepancies are encountered when this global sea-level chart is used in a regional setting. Sequences may be absent or additional sequences present, and they may change in character, depending on factors such as local tectonics. The caution with which the Haq et al (1988) sea-level chart should be applied does not affect the validity of sequence stratigraphic principles. It is advisable to use this chart as a first reference and to construct, as the need arises, a regional sequence stratigraphic framework for the area under study. The amount of (bio-)stratigraphic control required for a reliable refinement should not be underestimated.

Application to the stratigraphic nomenclature
To understand the depositional model in which the lithostratigraphic units have to be discerned, it can be very useful to apply sequence stratigraphic principles. Especially in the shallow-marine and transitional realms their value is evident. In order to obtain satisfactory results in sequence stratigraphic studies, lithostratigraphic data have to be combined with reliable biostratigraphic control and, where possible, seismostratigraphic observations.

Good results have been obtained for the Upper Jurassic and Lower Cretaceous. For the Cenozoic interval interest-ing results have been obtained as well. The lithostratigraphy of the Upper Permian and the Triassic is largely based on cyclic sedimentation, but details of a sequence stratigraphic interpretation have not been elaborated. Thusfar, the construction of a reliable sequence stratigraphic frame-work for the deposits of the Silesian, which are clearly of a cyclic nature, is hindered by the lack of sufficient high-resolution biostratigraphical control.

1.2 Codes for stratigraphic units

The system of codification of lithostratigraphic units used by NAM and RGD (1980) in the 1980 Nomenclature has been continued in the present publication. This system allows a three-stage hierarchy with the levels of group, formation, and member.
A group consists of two or more contiguous formations with common characteristics concerning lithology and/or interpreted depositional environment. The boundaries between groups follow distinct changes in lithology and are of a regional nature.

The formation is the fundamental unit in lithostratigraphic classification, a regionally or subregionally mappable rock unit. In subsurface geology this unit must, in addition, be identifiable by its wire-line log characteristics. In defining and describing the formations, however, the lithology as derived from the study of sample material is an essential element.
A member is a characteristic, mappable part of a formation. Therefore, a formation does not need to be fully subdivided into contiguous members. Specially shaped forms, such as tongues and lentils Hedberg (1976) are regarded as members. The recognition of these depends largely on the level of detail of the mapping.

Unit codes
A coding system was designed specifically to handle stratigraphic data in a computerised database. Any custom-built and commercially available relational database programs exist, but they all need a consistent lithostratigraphic coding system.
At group level a two-digit code is applied, e.g. RO for the Upper Rotliegend Group, ZE for the Zechstein Group. Each formation within a group is distinguished by the addition of two more digits, e.g. ROSL for the Slochteren Sandstone Formation, ZEZ1 for the Z1 (Werra) Formation. At member level a fifth digit is added, e.g. ROSLU for the Upper Slochteren Sandstone Member of the Slochteren Formation, ZEZ1C for the Z1 Carbonate Member of the Z1 (Werra) Formation.

Because two digits have been used to distinguish groups and formations, it is possible to assign larger units such as ‘Supergroups’ (e.g. N for ‘North Sea Supergroup’) or ‘Subgroups’ (e.g. KNN for ‘Vlieland Subgroup’), if necessary.
Although subdivision into a complete set of contiguous members is formally not obligatory, in some cases a full suite of member names and codes was designed to fill out the lithological sequence of a formation for the sake of electronic data handling. Artificial, informal member names with the affix “main” to the formation name were designed. Of course these units do not warrant a sepa-rate definition and description, since they are completely equatable to the formation they are part of.

Special codes for unit boundaries and unconformities are not given in the current revision and update of the stratigraphic nomenclature. It is left to the users of the Nomenclature to select their own appropriate codes and boundaries suited to the needs of their database system. This applies also to the use of a sixth digit in the codes for beds, reservoir units, etc.

1.3 Accessability of sample material

The descriptions of type sections and additional refer-ence sections are supported by relevant wire-line logs as depicted in this volume. As the need for additional study of sample material from these wells may arise, rules for visual inspection of such material have been set up:

  • Samples from offshore wells can be inspected at the premises of the RGD after due notification. Occasionally the material will only be present in the core repositories of the company which     operated the well, in which case the RGD will mediate to obtain access.
  • Samples from onshore wells are present either at the RGD or at NAM’s facilities in Assen. A request to study this material has to be directed to the RGD, which will then arrange access. It is not possible to take out sample material for further study. In case the RGD possesses microfossil slides, palynological preparations or thin sections of certain intervals, these can be lent to interested parties for a limited period of time.

2. Chronology and Chronostratigraphy

A geological time scale has been drawn up as a reference for the publication of the revision and update of the lithostratigraphy of the Netherlands. It is recommended to use this time scale as a national standard in order to achieve an unambiguous notion of the ages and stages. A simplified version is presented in Fig. A.1. (see pdf)

2.1 Chronology

The subdivision into ages and the spelling are slightly modified after the Global Stratigraphic Chart Cowie and Bassett (1989) as accepted by IUGS. The Cretaceous and Permian, however, have been modified according to Harland et al (1990)

Stage boundary ages
In the left-hand column ‘Time in Ma years’ the “Harland- 1989” linear numeric time scale (Harland et al., 1990) is adopted as the reference for the present Nomenclature. In the column ‘Stage boundary age’ three sub-headings are indicated, i.e. radiometric ages presented by Harland et al (1990), Hedberg (1976), Odin and Odin (1990) and Haq et al (1987). For the mid-European Cretaceous, datings of Lippolt et al (1984) are given. Note that particularly for the Late Jurassic and Early Cretaceous the numeric ages vary considerably, the geochronologic information on that interval being one of the poorest compared to older as well as younger systems.

2.2 Chronostratigraphy

For practical purposes, a column ‘Chronostratigraphy for regional stages and successions’ has been added, despite recommendations to the contrary by the International Stratigraphic Commission (IUGS). This is done to incorporate well-known and widely used regional units. For the Cretaceous the subdivision and correlation of Wagner (1992) has been adopted.

Disputed boundaries
Some (st)age names and boundaries deserve special attention, i.e. the Kimmeridgian and Portlandian, the Permian/Triassic boundary, the Jurassic/Cretaceous (J/C) boundary, and finally the Pliocene/Pleistocene boundary.

Permian/Triassic boundary
The base of the Buntsandstein is indicated as Late Permian, see also NAM and RGD (). According to Harland et al (1990) as well, much of the NW European Buntsandstein is thought to be Permian . Unfortunately, there is no biostratigraphical proof for this assumption from the area under investigation.

Upper Jurassic stages and the Jurassic/Cretaceous boundary
For more detailed information on this subject, please refer to Herngreen and Wong (1989). Since the middle of the nineteenth century the terms Kimmeridgian and Portlandian have been applied in a dual sense: the Kimme- ridgian and Portlandian in the British meaning (sensu anglico) and the short Kimmeridgian and extended Portlandian in the French sense (sensu gallico).
According to the recommendations and resolutions of the First and Second Jura Colloquium (Luxembourg 1962 and 1967), the Kimmeridge (st)age has been defined by the following ammonoidal zones (see Fig. G.1, Section G): top: Aulacostephanus autissiodorensis (Boreal) and Hybonoticeras beckeri(Tethyan); base: Pictonia baylei(Boreal) and Sutneria platynota (Tethyan).

This defines a short Kimmeridgian in accordance with French practice. Unfortunately, no decision has been taken about the name of the terminal Jurassic stage(s). If we were to use the term Portlandian in the original sense, i.e. starting with the albani Zone and ending with the lamplughi Zone, a new stage name would have to be introduced for the period beginning with the elegans and ending with the fittoni Zone. So, even after the two Luxembourg colloquia, there is still considerable uncertainty about the Upper Jurassic stage names. This confusing situation may explain the tendency in Northwest European literature to use the subdivision into Oxfordian, short Kimmeridgian and Volgian. For the Netherlands, the Working Group on Chronology and Chronostratigraphy recommends to follow the British convention.

Of more recent date are the discussions on the terminal Jurassic stage and the Jurassic/Cretaceous boundary in the International Subcommission on Jurassic Stratigra-phy (Lisbon, September 1987; Poitiers, September 1991). To summarize the state of affairs Remane (1991):

  1. The first candidate for the J/C boundary is the Tethyan Tithonian/Berriasian boundary.
  2. The widely used Tethyan (st)age Tithonian has not yet been ratified by the IUGS, nor is a stratotype designated. In particular micropalaeontologists (foraminiferal workers, palynologists,    nannoplankton experts) consider the Tithonian an impractical unit as the sections are generally barren.
  3. Opinions on the base of the Berriasian differ:
    • originally the boundary was placed at the transition Berriasella jacobi/Pseudosubplanites grandis Zone. This boundary proved to be inappropriate and only a limited number of ammonite experts adhere to this definition;
    • most members of the International Working Group on the J/C boundary prefer the base of the combined B. jacobi - P. grandis Zone;
    • others favour the base of the overlying Tirnovella occitanica Zone. If this option is accepted by IUGS the J/C boundary in the Tethyan and Boreal realm will coincide.
  4. For the Netherlands, which is located in the Boreal realm, the Portlandian and Ryazanian stages are used, and the J/C boundary is placed at the base of the runctoni Zone. This boundary is strongly recommended by the Working Group on Chronology and Chronostratigraphy.

Pliocene/Pleistocene boundary
The chronostratigraphical subdivision of the Quaternary in the Netherlands is mainly based on pollen analysis of terrestrial sediments Zagwijn (1985) The local Pliocene/ Pleistocene boundary is defined by the onset of the first cold phase, i.e. the Praetiglian, which occurred approximately 2.4 Ma ago. The International Union of Geological Sciences (IUGS), however, ratified the proposal of the International Commission on Stratigraphy (ICS) regarding the base of the Pleistocene Series. The Pliocene/ Pleistocene boundary stratotype is within subsection B of the Vrica section, Calabria, southern Italy. Closely linked to this resolution is the decision to define the Pliocene/ Pleistocene boundary at the base of the marine clay-stones overlying marker bed e in the Vrica section, (Bassett (1985); Aguirre and Pasini (1985) dated at 1.64 Ma)


2.3 Sequence stratigraphy and eustatic curve

The inclusion of the eustatic sea-level curve of Haq et al (1988) was questioned in the Working Group because of its explanatory rather than descriptive nature. Although no consensus was reached whether this curve may be fully applicable for the Netherlands, it was decided to include the eustatic curve in the present time scale as supplementary information. The accuracy of the interpretations and the philosophy behind the concept fall outside the responsibility of the Working Group.
In modern stratigraphical evaluations the use of genetically related units (Depositional Sequences) has become important and has proven to be meaningful. The relatively frequent variations in accommodation space, may be linked with tectonic activity Cloetingh (1988), or with eustatic sea-level fluctuations (e.g. Van Wagoner et al (1990)). The apparently global nature of these variations in relative sea level offer the possibility of additional detailed chronostratigraphic correlations. Consequently, depositional sequences and eustatic curves have been incorporated in the geological time scale of the Netherlands.
The most complete sequence stratigraphical framework and reference for the eustatic sea- level fluctuations, is currently the “Mesozoic-Cenozoic Cycle Chart” by Haq et al (1988). Some intervals lack detail (e.g. the Triassic) or reflect tectonic overprints and consequently require future adjustments. Despite these problems, the chart (depositional sequences and eustatic curve) has been recalibrated to the “Harland-1989” scale. The “Harland” stage-boundary ages have been adopted. The ages for sequence boundaries and maximum flooding surfaces were constructed by linear extrapolation.
For the Paleozoic a sequence stratigraphical framework and detailed overview of the eustatic history is not yet available. However, a number of sea-level curves for the Paleozoic have been published from several parts of the world Ross and Ross (1985) . It is difficult to compare these curves because of the limited access to verifiable biostratigraphic control points in most of the data sets. Taking the observed sedimentary successions, publish-ed sea-level curves and age control at face value, common short- and long-term sea-level trends can be recognised. These trends may have eustatic significance. However, because a sea-level curve for the Paleozoic would be highly speculative and tentative, it is not included in this Time Scale.

2.4 Main tectonic events

In this column, major local and regional tectonic events have been listed. The tectonic phases are not sharply defined in time and place. The position of the names in the column are only roughly indicative of when the main tectonic activity took place. For comparison with other European and Atlantic tectonic events please refer to Ziegler (1990).

2.5 Enclosure

A.1 Geological time scale for the Netherlands.

3 Main tectonic elements

This section presents the main tectonic elements of the Dutch subsurface, accompanied by a set of small-scale maps and concise descriptions. The purpose is to come to an unambiguous usage of the names of these elements. In the following sections on stratigraphy, the basins and highs mentioned here will be referred to regularly for the distribution of the various formations. To place the various elements in a dynamic tectonic framework, the structural setting is briefly mentioned. For further reading one is referred to regional studies e.g. Heybroek () Heybroek (), van Wijhe (1987), Glennie (1990) and Ziegler (1990).
A number of tectonic phases has affected the area. Structural elements have changed in nature and location during these periods. Therefore maps of six consecutive intervals have been made:

  • Silesian (see pdf) , which includes the effects of the Variscan Orogeny.
  • Early Permian (see pdf).
  • Late Permian (see pdf).
  • Triassic to Liassic (see pdf).
  • Late Jurassic to Early Cretaceous (see pdf) , a period dominated by the Mid and Late Kimmerian deformation phases.
  • Cenozoic. (see pdf)
Four factors complicate delineation of the older tectonic elements (especially Cretaceous and Permian):
  1. Difficulty in identifying stratigraphic units below the Saalian Unconformity, and scarce well penetrations of those deeper units.
  2. Widespread halokinesis of the Zechstein salt complicates the isopach patterns of overlying units, and the decoupling nature of the salt inhibits dating of many of the fault movements affecting the pre-Zechstein.
  3. Widespread erosion of and/or non-deposition on the Mid to Late Kimmerian platform areas make it difficult to assess the precise timing of the formation of these highs.
  4. Reactivation of Late Variscan faults during later phases.
Consequently the boundaries of the structural elements are often not clear-cut and tend to be somewhat arbitrary. Especially the Cretaceous units, and to some extent the Permian units, are rather speculative.
In the following description, the whole area under consideration is considered to be part of the Northwest European Basin, stretching from Ireland to Poland.


3.1 Structural setting

In Cretaceous times, the area of the Northwest European Basin was a foreland basin in an intracratonic setting. To the south, the London-Brabant Massif and the Rhenish Massif acted as positive elements, similar to the Ringkøbing Fyn High in the northeast and the Mid North Sea High in the northwest. During the Silesian, the Variscan belt in the south gradually prograded northwards, but only slightly affected the Northwest European Basin. This Variscan deformation was largely limited to repeated rejuvenation of probably already existing fault zones of Caledonian age associated with thermal subsidence. During the Late Westphalian- Early Stephanian Asturian deformation phase, compressional deformation took place on the northern Variscan forelands and rifting probably in the Ems Low and the Proto Central Graben. Subsequently, a complete change in tectonic regime occurred. The ensuing Saalian deformation phase (Stephanian-Autunian) was caused by thermal doming with associated volcanism. This led to locally deep truncation of the Silesian, e.g. on the Netherlands High.
The faults controlling the structural elements of “young-er” features such as the Sole Pit, Broad Fourteens, West and Central Netherlands Basins, Ems Low and the Central Graben, date back to Silesian-Permian times, or even earlier.

Permian to Middle Jurassic
The Permian to Middle Jurassic sediments of the Netherlands form a nearly conformable sequence, in most areas bounded at the base by the Saalian and at the top by the Mid Kimmerian regional unconformities. In general, the tectonics of this period can be character-ized as more quiet than those of the previous and succeeding periods. The structural architecture of the area was dominated by the Southern Permian Basin, within which a number of smaller sub-basins developed. The tectonic elements are shown on three maps: the Early Permian (see pdf), the Late Permian (see pdf) and the Triassic to Liassic (see pdf) . In general, depocentres occurred along the same trends as in the preceding and succeeding periods. As the depocentres filled up, sedimentation became more uniform over progressively larger areas.

Late Jurassic - Early Cretaceous
Early in the Middle Jurassic (Aalenian-Bathonian), a large area in the middle of the North Sea, the Central North Sea Dome, was uplifted by the Mid Kimmerian tectonic movements. A marked change in structural frame-work occurred during the Late Jurassic. Faulting accel-erated and heat flow increased, accompanied by igneous activity. The well-known rift structures in the Northwest European Basin, such as the Central Graben, Broad Fourteens Basin and West Netherlands Basin, were fully shaped during this time, as well as the smaller Central Netherlands Basin, Terschelling Basin, Vlieland Basin and Lauwerszee Trough.
To the south of the Southern North Sea Basin, the London-Brabant Massif and Rhenish Massif remained stable highs, as did the Ringkøbing-Fyn High in the north-east. The Mid North Sea High, with the Cleaver Bank High to the south of it, was part of the Central North Sea Dome during the Middle to Late Jurassic.
The timing of rifting varied slightly, and prograded from the north to the south. The recognized tectonic pulses are usually referred to as Mid and Late Kimmerian.
In general, deposition during times of rifting is characterized by high sedimentation rates and significant facies changes in the basinal areas. After the Late Jurassic to Early Cretaceous Late Kimmerian phase, when extensional faulting declined and thermal subsidence took over, the old highs were slowly transgressed, and sedimentation patterns became more regular, although initially thicker deposits continued to accumulate in the rift basins than on the highs. (pdf)

Late Cretaceous and Cenozoic
In the Late Cretaceous, subsidence patterns were completely reorganized. The previously stable highs started to subside rapidly, accumulating thick sequences of chalk. Eventually, even the long-lived London-Brabant Massif and the Mid North Sea and Ringkøbing-Fyn Highs were inundated.
Tectonic inversion affected many of the Late Jurassic- Early Cretaceous rift basins during the Late Cretaceous and Early Tertiary. Locally, inversion lead to significant erosion of the rift sequence. The Subhercynian (Santonian to Campanian), Laramide (Paleocene) and Pyrenean (Early Oligocene) unconformities are expressions of these inversion phases. In Cenozoic times, tectonics in general were dominated by overall subsidence of the original Mesozoic North Sea rift system. A thick sequence of sediments, up to ca. 2500 m thick in the north of the Dutch part of the continental shelf, was deposited in the North Sea Basin. The Cenozoic sediments are bounded at their base by the Laramide or Pyrenean unconformity. Within the sequence, sea-level changes and erosional events resulted in numerous breaks in the sedimentary record.

3.2 Structural elements

Achterhoek High
The Achterhoek High is a broad anticlinal structure which developed in the eastern part of the Netherlands during the Silesian. It is bordered in the north by the Gronau Fault Zone, which separates the Westphalian B and Early Westphalian C subcrop below the Saalian unconformity on the Achterhoek High from Late Westphalian C, Westphalian D and Stephanian strata in the Ems Low to the north.

Ameland Block
(Jurassic - Cretaceous)
The Ameland Block, named after the island of Ameland, is a stable structural unit very similar to the Schill Grund High, from which it is separated by the Rifgronden Fault Zone. In the south, the Hantum Fault Zone forms the boundary with the Friesland Platform, and an unnamed fault zone forms the boundary with the Terschelling Basin to the northwest. Late Jurassic erosion was severe on the Ameland Block, and Lower Cretaceous deposits overlay the Lower Triassic and locally thick Zechstein deposits.

Broad Fourteens Basin
(Triassic - Cretaceous)
The Broad Fourteens Basin has a post-Triassic origin. Although located in the same general area as the Permian to Triassic Off Holland Low, from which it developed, the Broad Fourteens Basin has a much more clearly defined northwest-southeast trend. Faulting appears to have begun during the Triassic along its southwestern boundary and subsequently accelerated during Jurassic rifting. During the Late Jurassic to Early Cretaceous, the Broad Fourteens Basin became a pronounced northwest- southeast trending rift basin, with the Indefatigable Fault Zone at its northwestern margin. To the southeast, the basin merges with Central Netherlands Basin without any clear boundary. A series of en-échelon highs, of which the IJmuiden High is one, marks the otherwise poorly defined boundary with the West Netherlands Basin. Faulting and subsidence during the Late Jurassic resulted in increased thicknesses of Upper Jurassic continental deposits. The basin was severely inverted during the Late Cretaceous. The presence of Zechstein salt has resulted in some spectacular low- angle reverse faults. Locally, much of the rift sequence has been removed by Late Cretaceous erosion.

Campine Basin
The Campine Basin is located parallel to the northern flank of the London-Brabant Massif. It existed during Silesian times, and is marked by the preservation of a thick sequence of Westphalian C/D beneath the Saalian unconformity. Termination of basin subsidence in the Permian is implied by the absence or very thin development of deposits of that period.

Central Netherlands Basin
(Permian - Cretaceous)
During the Early Permian, the Central Netherlands Basin was a relatively subtle northwest-southeast trending low which opened to the northwest into the Off Holland Low. During the Late Permian, it was more clearly expressed by the development of the Zechstein 1 evaporites southwest of the Texel- IJsselmeer High.
The Central Netherlands Basin was an area of pronounced subsidence during the Late Jurassic and Early Cretaceous. Its younger history, however, is less well known due to extensive erosion. The basin was inverted strongly during the Late Cretaceous, as a result of which much of the Upper Jurassic to Lower Cretaceous rift sequence has been eroded. To the NW, the basin merges with the Broad Fourteens Basin. To the southeast, the boundary of the basin is poorly defined. The Gouwzee Trough is a deep depocentre of the Central Netherlands Basin, located between two inversion axes, where thick Jurassic deposits have been preserved.

Central Graben
(Cretaceous - Cretaceous)
The Central Graben, although essentially a Late Jurassic to Early Cretaceous rift structure, clearly existed in earlier times, as indicated by isopach patterns. A Late Stephanian to Autunian initiation or precursor of the Central Graben is assumed. It is referred to as the Proto Central Graben. Evidence for Permian subsidence includes the presence of Permian salts further to the north in the graben, outside the Dutch offshore area and the preservation and/or deposition of Lower Rotliegend or Stephanian volcanics, as indicated in several wells within the Netherlands continental shelf on the flanks of the graben. Excess subsidence during Triassic times is clearly visible on isopach maps. Whether the Proto-Central Graben was a true fault-bounded graben or rather a flexure-bounded trough is difficult to determine because of poor seismic data at the edge of the graben.
The Mid and Late Kimmerian tectonic events led to the final structuration of the actual Central Graben. It is a well-defined NNE-SSW-trending, fault-bounded subsidence zone, initiated in the beginning of the Middle Jurassic as a rift in the uplifted Central North Sea Dome, with thick Upper Jurassic and Lower Cretaceous deposits. It is the southern extension of the main Jurassic rift system of the North Sea (Viking Graben - Central Graben). The southern part of this rift zone may be referred to as Dutch Central Graben. In some RGD-publications it was called Central North Sea Graben to dist-inguish it from the Roer Valley Graben, which was also called Central Graben by a number of authors (e.g.van Staalduinen et al (1979)). The northern part of the Dutch Central Graben, which suffered least from Late Cretaceous inversion, shows the greatest thickness of Upper Jurassic sediments. To the south, the boundary of the Central Graben is rather difficult to define in blocks L04 to L09. Under the influence of rifting and differential sediment loading, halokinesis increased, creating salt walls that coincide with the main bounding rift faults. Both rifting and halokinesis had considerable influence on sedimentation within the basin.

Cleaver Bank High
(Cretaceous - Cretaceous)
There are indications of intra-Cretaceous thinning of strata in the south of the Cleaver Bank area. During the Permian, the Cleaver Bank High was the northern part of a long-lived, rather vaguely defined, north-south trend-ing high, located close to the UK-Netherlands median line (van Hoorn, 1987). The Cleaver Bank High remained a relatively stable high during the Late Jurassic and Early Cretaceous. Late Jurassic uplift resulted in erosion down to the Lower Triassic, and locally to the Zechstein. To the west, increasing thicknesses of Triassic deposits have been preserved in the adjacent Sole Pit Basin.

Elbow Spit High
The Elbow Spit High is a prominent NNW-SSE trending asymmetric high, plunging to the southwest from the Mid North Sea High. It is fault bounded on its north-eastern side and to the southwest it dips gently into the Southern Permian Basin. Because of extensive Kimmerian erosion (Middle and Late Jurassic) down to the Lower Cretaceous and Devonian, its Triassic history is uncertain. However, Permian isopach and facies patterns suggest that it was a high at that time. It can be considered as a spur of the Mid North Sea High, separating the Step Graben and the Cleaver Bank High. Nevertheless, in the absence of any Upper Jurassic and Lower Cretaceous deposits on the Elbow Spit High and on the Mid North Sea High and Cleaver Bank High, it is difficult to establish any significant differences with these adjacent highs during Late Jurassic and Early Cretaceous times.

Ems Low
The Ems Low along the Dutch-German border came into existence during the Westphalian C as a broad, subsiding basin and developed into a real graben during the Westphalian D and Stephanian. A relatively thick sequence of Westphalian D (up to 700 m) is overlain by Stephanian. The low is bordered to the west by the Groningen High, the Netherlands High and the Achterhoek High, and towards the southwest by the Gronau Fault Zone. North of the town of Hengelo, the fault zone is informally called the Weerselo Fault and its N- S splay carries the name Reutum Fault.
During Permian to Liassic times, the Ems Low was a north-south trending low, plunging to the north from the Rhenish Massif. Sediments of this age thicken relatively gradually into the low from the surrounding highs. From Jurassiimes on, the Lower Saxony Basin overprinted the Ems Low.

Friesland Platform
(Jurassic - Tertiary)
The newly defined Friesland Platform is located between the Texel-IJsselmeer High in the southwest and the Hantum Fault Zone in the northeast. The area was uplift-ed and eroded down to the Zechstein during the Late Jurassic.
Triassic deposits are best preserved in the south-east, where the platform gradually passes into the western extension of the Lower Saxony Basin.
Further south, on trend with the Texel-IJsselmeer High, several high blocks (sometimes referred to as Dalfsen Saddle and Ommen High) form the southern boundary of the Friesland Platform. To the northwest, the Platform passes into the Vlieland Basin, where Upper Jurassic deposits are present. After some authors Herngreen et al (1991a), the combined high area of the Friesland Platform and Groningen High may be called the North Netherlands High.

Groningen High
(Cretaceous - Tertiary)
The Groningen High is a prominent stable structural high between the Lauwerszee Trough and the Cretaceous to Triassic Ems Low. Much of its significance is derived from the fact that it is the site of the giant Groningen gas field. In Jurassic times it was severely eroded, and Lower Triassic strata subcrop below the Base Cretaceous (Late Kimmerian) unconformity.

Kijkduin High
The Kijkduin High is a part of the earlier West Nether-lands Basin which was inverted during the Late Eocene. It has a NW-SE elongation and is bounded to the north-east by the Mid-Netherlands Fault Zone. Its southwestern flank dips into the Voorne Trough. The Eocene uplift was part of a more extensive positive movement along the Mid-Netherlands Fault Zone during the Pyrenean phase.

Krefeld High
(Cretaceous - Quaternary)
During the Cretaceous the Krefeld High was a poorly defined structure. It may already have come into existence during the early Cretaceous. It is characterized by relatively thin Namurian strata. During the Late Jurassic the high formed the northwestern extension of the Rhenish Massif. Both elements were uplifted, as a result of which all Mesozoic strata present were truncated.

Lauwerszee Trough
(Cretaceous - Tertiary)
The Lauwerszee Trough is a newly defined structural element, named after the former Lauwerszee. It is located between the Groningen High and the Friesland Platform, from which it is separated by the Hantum Fault Zone. The boundary with the Ameland Block is more gradational. Towards the south its boundary is very complex because of interference with the faults associated with the Lower Saxony Basin. The trough was a long-lived feature, existing as early as the Cretaceous, when it separated the Netherlands High from the Groningen High, to Tertiary times. The structure was rejuvenated during the Mid or Late Kimmerian deformation phase. The Lower Cretaceous is developed more thickly than on the flanking highs, but there are no indications of the presence of Jurassic deposits. These might be present locally, in areas of salt withdrawal.
The Lauwerszee Trough showed renewed subsidence during the Paleogene. The corresponding sequence reaches a maximum thickness of the up to 1000m. Total thickness of the Cenozoic sediments is over 1750m. The exact magnitude of tectonic subsidence is obscured by salt flow from the centre of the basin towards the margins. Subsidence along the eastern and western (Hantum Fault Zone) boundary faults is accommodated by the Zechstein salt. Differential loading and tectonic stresses are expressed by salt movement along the fault trajectories.

London-Brabant Massif
(Cretaceous - Cretaceous)
The London-Brabant Massif is a northwest-southeast trending high, consolidated from rocks deformed during the Caledonian orogenic phase and, at least in the United Kingdom, older orogenic periods. The element consists of a large Paleozoic anticlinal core, and extends from Belgium through the southwestern Netherlands to the southern United Kingdom. It forms the southern limit of the Southern North Sea province. During the Carboni-ferous it may have formed a relatively slowly subsiding platform. The Silesian shows an east-west onlap on the northern flank of the Massif (Namurian A in the SE Netherlands to Westphalian C in the United Kingdom 52 offshore quadrant). The London-Brabant Massif may have acted as a source of clastic material during the Late Westphalian C to Stephanian. No Permian to Liassic sediments are preserved on the Massif and it is likely that it remained at least partially subaerially exposed through-out this period. Like the Rhenish Massif it was a sediment source for the flanking Southern Permian Basin and was gradually eroded during this period.
All Mesozoic depositional sequences thin towards the high. During the Late Jurassic and Early Cretaceous, the London-Brabant Massif formed a landmass, which be-came connected with the Rhenisch Massif, where no deposition took place. Inundation of the Massif during the Late Cretaceous and Eo-Oligocene brought an end to its existence.

Lower Rhine Embayment
(Tertiary - Quaternary)
The Lower Rhine Embayment is a Tertiary re-entrant in the southeast of the Netherlands and the neighbouring German territory. It is a block-faulted area between the Rhenish Massif in the east and a Mesozoic and Paleozoic high area in the southwest, which originated in the Early Oligocene. The embayment comprises the southeastern end of the Roer Valley Graben and its adjoining blocks.

Lower Saxony Basin
(Jurassic - Cretaceous)
The Lower Saxony Basin is a WNW-ESE trending Late Jurassic-Cretaceous basin, which is situated mainly in Germany. Its western extension can be seen in the Netherlands, where Jurassic deposits thin towards the west, wedging-out onto the Friesland Platform. The basin was inverted during the Late Cretaceous, with the strongest effect in its southern part. The Gronau Fault Zone forms part of the southwest boundary of the basin. Activity along this fault continued into the Cenozoic.

Mid Netherlands Fault Zone
(Jurassic - Tertiary)
The Mid Netherlands Fault Zone is a newly defined NW- SE trending structural element, which forms the boundary between the Central Netherlands Basin and the West Netherlands Basin. The fault zone is a long-lived feature, composed of a number of fault blocks. It comprises the Peel Block (formerly usually called Peel Horst), the Maasbommel High and the Zandvoort Ridge. The off-shore IJmuiden High may also be considered as an element of this fault zone. Its continuation further to the northwest forms the southwestern boundary of the Broad Fourteens Basin (Indefatigable Fault Zone). It is considered likely that the Mid Netherlands Fault Zone constitutes an old Paleozoic trend that was reactivated repeatedly during later episodes. The Mid Netherlands Fault Zone was last rejuvenated during the Late Eocene (Pyrenean phase).

Mid North Sea High

The Mid North Sea High lies mainly outside the Nether-lands' continental shelf just as the Ringkøbing-Fyn High. It forms a rather stable structural element at the northern boundary of the area under consideration.
During the Permian it bordered the Southern Permian Basin to the north. It was at least partially above water throughout the Late Permian to Liassic period, but its relief was probably relatively low since it was not a source of significant amounts of sediment. The Mid North Sea High was uplifted during the Middle and Late Jurassic. Consequently, no Jurassic and only locally, in the south, some Triassic deposits are present. Because of its position outside the rift basins, only very limited faulting occurred on the Mid North Sea High. During the Late Cretaceous the high gradually lost its significance and the area became a depocentre in the Cenozoic.

Netherlands High
The Netherlands High is a late Silesian (to Autunian) high, which is roughly outlined by the area in the central and northern Netherlands with a Westphalian A to B subcrop. The Hantum Fault Zone forms its northeastern border. In this area, Westphalian C and D strata are assumed to have existed previously because of the high degree of organic maturity beneath the Saalian unconformity. Part of this area may have been the source of sediments deposited in the Ems Low and the Campine Basin during the Late Westphalian C, Westphalian D and Stephanian.

Netherlands Swell
The Netherlands Swell occupies much of the Netherlands’ onshore. Its outline is defined by the impact of the Base Solling (or Hardegsen ) Unconformity, which is known as the most significant interruption of continuous Permian to Middle Jurassic sedimentation. The swell is flanked by the Off Holland Low to the west and the Ems Low to the east. In the centre of the swell, the Main Buntsandstein has been removed completely by erosion caused by the Pre-Solling uplift. Its subsequent history is obscured by severe Kimmerian erosion on the Texel-IJsselmeer High. Its location approximates that of the Netherlands High.

Noord- Holland Platform
(Jurassic - Cretaceous)
The Noord- Holland Platform is a newly defined Jurassic- Cretaceous structural element on the southwestern flank of the Texel-IJsselmeer High, north-east of the Broad Fourteens Basin. Late Jurassic uplift and erosion did affect the area, but less severely than on the central Texel-IJsselmeer High. Zechstein and Triassic deposits are overlain by Upper Cretaceous Chalk. Locally, the Chalk is thinner as a result of Late Cretaceous inversion.

North Sea Basin
(Tertiary - Quaternary)
The North Sea Basin is a rapidly subsiding Cenozoic basin. The outlines of the basin roughly coincide with the present- day North Sea. In the southern continuation of the central axis of the North Sea Basin, a separate depocentre developed in the centre of the Netherlands i.e. the Zuiderzee Low, named after the former Zuiderzee, which reached its maximum rate of subsidence during the Miocene, giving rise to Upper Miocene sediments with a thickness of up to 300m.

Off-Holland Low
Permian - Triassic)
The Off-Holland Low is the Permian predecessor to the Broad Fourteens Basin. Initially, it was a rather broad and poorly defined area where a thick sequence of Upper Rotliegend sandstones developed. To the southeast it gradually merged with the Permian Central Netherlands Basin. In the Early Jurassic, it was gradually overprinted by the northwest-southeast trending Broad Fourteens Basin.

Rhenish Massif
(Cretaceous - Quaternary)
The Rhenish Massif is situated entirely in Germany, just east of the southern Netherlands. It consists of rocks deformed during the Variscan orogeny. It forms the south-eastern limit of the southern North Sea province and was an important sediment source during the Permian and Triassic. It was gradually eroded througout the Permian to Cretaceous period. Renewed uplift occurred first in connection with the Late Kimmerian movements, and later when the Lower-Rhine rift system developed during the Late Oligocene and accelerated during the Middle-Late Miocene.

Ringkøbing- Fyn High
(Cretaceous - Cretaceous)
The Ringkøbing- Fyn High trends roughly east-west from the Central Graben to onshore Denmark. It lies mainly outside the Netherlands continental shelf, but just like the Mid North Sea High forms a rather stable structural element which borders the Southern North Sea area to the north. It has a gradational boundary with the Southern Permian Basin to the south. Its relation to the Central Graben to the west during the Permian is un-known as a result of younger faulting and burial, but it is along the same trend as and is similar to the Mid North Sea High. It was at least partially above water through-out the Upper Permian to Liassic period, but was probably relatively low in relief as indicated by the lack of dispersed sediment. Like the Mid North Sea High, this high gradually lost its significance during the Cretaceous and ceased to exist in Tertiary times.

Roer Valley Graben
(Triassic - Quaternary)
The Roer Valley Graben lies in the southeast continuation of the West Netherlands Basin, where the structural grain shows a NNW-SSE direction. The graben is bound-ed by the Peel Block and the London-Brabant Massif. During the Triassic, a relatively thick package of sediments accumulated in the area. Rifting started in Jurassic times and continental deposits accumulated during the Late Jurassic to Early Cretaceous in the fault- bounded graben. Late Cretaceous inversion affected the basin, but less than the West Netherlands Basin.
Faulting in the Roer Valley Graben resumed during the Late Oligocene, related to the development of the Lower- Rhine Rift System. The graben now shows an asymmetric profile. On the north-eastern side a narrow fault zone, the Peel Boundary Fault (post inversion throw up to 1000m), separates the graben from the bordering Peel Block, whereas on the south-western side the boundary faults show a wider spa cing with a more gradual step- like profile towards the neighbouring London-Brabant Massif. The Tertiary sequence in the graben reaches a maximum thickness of 2000m. Strongest subsidence occurred during the Oligocene and Miocene. On older maps the Roer Valley Graben was often referred to as the Central (Netherlands) Graben or Centrale Slenk.
The Peel Block, the Venlo Block, the K?r Block and the Erft Block are fault blocks which belong to the north-eastern rift shoulder of the Roer Valley Graben. Major uplift of these blocks during the Late Jurassic to Early Cre-taceous resulted in erosion, locally down to the Cretaceous.
As a result of extensive coal-mining activities in the past the main faults have been named. The Tegelen Fault separates the Peel Block and the Venlo Block. The Viersen Fault separates the Krefeld High on the one side from the Venlo Block and the K?r Block on the other side.
The southern boundary of the Roer Valley Graben is marked by a fault zone which comprises a set of en-échelon faults. In the province of Limburg, the southern edge of the Roer Valley Graben is marked by a distinct fault called the Feldbiss Fault. Towards the northwest its role is gradually taken over by the Geleen Fault. Its continuation into Belgium is named Neeroeteren Fault . In the province of North-Brabant, where the Roer Valley Graben re-enters in the Netherlands, its boundary is formed by the Rijen Fault.

Schill Grund High
The Schill Grund High is a southerly extension of the Ringkøbing-Fyn High. During the Jurassic, the Schill Grund High was a stable platform area, which flanked the rapidly subsiding Central Graben on the eastern side. In the south, at that time, the Rifgronden Fault Zone separated the Schill Grund High from the newly formed Terschelling Basin. Whereas most of the Jurassic, Upper and Middle Triassic on the Schill Grund High was re-moved during Middle and Late Jurassic uplift, much of the Lower Triassic escaped erosion. To the north, erosion cuts deeper into the section, and on the Ringkøbing-Fyn High (mainly in Danish territory) the Cretaceous has been truncated.

Southern Permian Basin
(Permian - Triassic)
The Southern Permian Basin is a roughly east-west trending, elongate intracratonic basin, extending from onshore United Kingdom into Poland, the deepest part of the basin occurring in Germany, south of the Danish border. In general, it gradually wedges out onto the flanking Mid North Sea and Ringkøbing-Fyn Highs to the north, and London-Brabant and Rhenish Massifs to the south. It is expressed most clearly in the thickness variations and isopach patterns of the Rotliegend and to a progressively lesser degree of the Zechstein and Triassic. Due to progressive basin fragmentation during the Triassic, it ceased to exist.

Step Graben
(Jurassic - Cretaceous)
The Step Graben is a feature which is directly related to the Jurassic rifting of the southern North Sea. It is not named after a geographic feature, but its name is deri-ved from the fact that it is considered to be an intermediate block, stair-stepping from the Mid North Sea/ Cleaver Bank High into the Central Graben. Uplift at the end of the Middle Jurassic resulted in some erosion of earlier Jurassic deposits, whereas most of the Triassic escaped erosion. The remaining stratigraphic sequence differentiates the Step Graben from neighbouring highs and the Central Graben proper. The area was affected by Late Jurassic to Early Cretaceous rifting, although considerably less than the Central Graben. Upper Jurassic deposits are developed only relatively thinly. Halokinesis accelerated during the Late Jurassic and Early Cretaceous, and resulted in the formation of salt walls that are parallel to the main north-south faults. In the north some northwest-southeast salt walls are also present that coincide with the boundary faults of the Outer Rough Basin, which is situated mainly in German and Danish territory and was hardly affected by the Mid Kimmerian uplift.

Terschelling Basin
(Jurassic - Cretaceous)
The newly defined Terschelling Basin, named after the Terschelling Bank, is a Late Jurassic to Early Cretaceous basin. It boundaries are formed by a the Rifgronden and Hantum Fault Zones in the northeast and southwest respectively. An unnamed fault zone forms the south-eastern boundary. In general, structural events occurred slightly later in the Terschelling Basin than in the Central Graben. Besides faulting, halokinesis played an important role in controlling deposition.
Contrary to the bordering Central Graben, uplift occurred before the end of the Middle Jurassic, and the older Jurassic sequence was removed by erosion. Consequently, Upper Jurassic deposits, which are thinner and younger than in the Central Graben, generally rest on the Triassic. Subsidence and faulting continued during the Early Cretaceous, and deposits from that period are thicker than in the Central Graben.

Texel-IJsselmeer High
(Permian and Jurassic - Cretaceous)
The Texel-IJsselmeer High has been a high during much of the geological history. During the Permian it was a rather subtle northwest-southeast trending high that plunged to the northwest into the Southern Permian Basin. Marked thinning of the Upper Rotliegend occurs across the High and Zechstein facies patterns were strongly influenced by its presence. During Triassic times the area of the Texel-IJsselmeer High was part of the Netherlands Swell.
Late Jurassic and Early Cretaceous uplift of the northern part of the Netherlands resulted in a number of struc-tures, one of which was the rejuvenated Texel- IJsselmeer High. It was eroded deeply. On the central parts of the High the Westphalian A is overlain by Late Cretaceous Chalk.

Vlieland Basin
(Jurassic - Cretaceous)
The Vlieland Basin is a shallow, relatively little faulted, basinal area. Thin Upper Jurassic deposits are overlain by the Lower Cretaceous, thinning towards the Texel- IJsselmeer High and onto the Friesland Platform. A sub-tle high, known as the Vlieland High Herngreen et al (1991a), separates the Vlieland Basin from the Central Graben. During the Late Cretaceous, inversion affected the basin, resulting in truncation of the Chalk sequence. A notable feature of the Vlieland Basin is the presence of the Mid-Late Jurassic Zuidwal volcano below the Waddenzee, southeast of the island of Vlieland.

Voorne Trough
The Voorne Trough is a northwest-southeast striking basin to the southwest of the Kijkduin High. It developed during the Paleocene and Eocene. The trough exhibits an asymmetric north/south profile with a long southern flank which gradually rises onto the former London- Brabant Massif and a short, slightly steeper northern flank. The through was filled by Paleocene and Eocene sediments. The structure ceased to exist after the Early Oligocene.

West Netherlands Basin
(Triassic - Cretaceous) The West Netherlands Basin is a northwest-southeast trending basin along the northeastern margin of the London-Brabant Massif. The basin is bounded by faults in the southwest, against the London-Brabant Massif. The Mid Netherlands Fault Zone separates it from the Broad Fourteens Basin and Central Netherlands Basin to the north and northwest. The basin gradually merges into the Roer Valley Graben (towards the southeast), which has a more NNW-SSE orientation. These two basins overly the Silesian Campine Basin.
During the Triassic, subsidence was possibly related to sediment loading, whereas from the Late Jurassic onwards, extensional faulting became more dominant.
In the Late Jurassic to Early Cretaceous, rifting made the basin more pronounced. The absence of Zechstein salt resulted in a characteristic structural style, with Late Jurassic-Early Cretaceous half- grabens in which coastal clastics accumulated. During Late Cretaceous inversion, many of the rift faults were re-activated as reverse faults. Continuing inversion during the Tertiary led to the formation of the Kijkduin High.

Winterton High
(Jurassic - Cretaceous)
The Winterton High is a structural high between the Broad Fourteens Basin and the Sole Pit Basin in the U.K. sector of the North Sea. Uplift during the Late Jurassic - Early Cretaceous caused deep erosion, locally down to the Cretaceous.

Van Adrichem Boogaert, H.A. & Kouwe, W.F.P., 1993-1997. [Stratigraphic unit]. In: Stratigraphic Nomenclature of the Netherlands.
Retrieved [Datum] from [url].