Existing Late Jurassic stratigraphy was established in 1980 when NAM and RGD published the ‘Stratigraphic Nomenclature of the Netherlands’. Van Adrichem Boogaert and Kouwe revised the standard in 1993-1997. The lithostratigraphical classification was based on various regional publications of the Upper Jurassic, e.g. by Brown in Glennie (1990), Cameron et al. (1992), Frandsen et al. (1987), Herngreen & Wong (1989), Herngreen et al. (1991), Michelson & Wong (1991) and Ziegler (1990). New data gathered from continued exploration in the Dutch Central Graben and adjacent Terschelling Basin during the past twenty years (1993-2012) resulted in an improved understanding of the latest Middle Jurassic to earliest Cretaceous, Callovian-Ryazanian, siliciclastic successions. Several studies contributed to this progress, e.g.: Abbink et al. (2006), Herngreen et al. (2000, 2003), Duin et al. (2006), Wong (2007), Andsbjerg & Dybkjaer (2003), Michelsen et al. (2003), Johannessen (2003), Fraser et al. (2003), Coward et al. (2003) and Lott et al. (2010). New palynological techniques (e.g. Sporomorph Ecogroups in Abbink, 1998) and newly acquired sedimentological, lithological, stratigraphic and seismic data led to the identification of three well recognizable unconformities or their correlatable conformities in the late Middle Jurassic to earliest Cretaceous. These (un-)conformities resulted in the definition of three major stratigraphic sequences in the Late Jurassic and one in the overlying earliest Cretaceous interval. The unconformities and stratigraphic units in-between are related to to tectonic, climatic, environmental and stratigraphic events (Abbink et al., 2006). The recognition of these sequences in wells in the Central Graben and Terschelling Basin showed the present lithostratigraphic scheme to be outdated for consistent stratigraphic interpretation. Hence the necessity arose to revise and update the Late Jurassic succession of the Stratigraphic Nomenclature for the subsurface of the northern Dutch offshore area. In order to reach broad acceptance and a general consensus, cooperation was sought and obtained from the E&P industry and consultants. A series of workshops and (inter)national presentations were organized on this topic from 2010-2012. The recommendations from these meetings and discussions afterwards are integrated in the present contribution (see pdf).
For a good understanding of the studied interval and correct application of the presented lithostratigraphy, detailed information is incorporated in the definitions. All definitions include detailed descriptions of lithology, boundaries, depositional setting, sequence stratigraphic interpretations, and ages. Reference is made to diagnostic fossil species, including dinoflagellates, sporomorphs, foraminifers and ostracods. Presented biostratigraphic data is derived from RGD/TNO studies and publications, and various company and consultancy reports.
A TNO selection of diagnostic biomarker horizons, correlated with the standard ammonite zonation for Northwest Europe, is presented in the biomarker Table I (see pdf). Specific details regarding the Jurassic-Ryazanian interval, including detailed bioevents, are recorded in Munsterman et al. (2012) and will be published in Verreussel et al. (in prep.).
The Permian, Triassic and Early Jurassic were periods of relative tectonic quiescence in the Netherlands (De Jager, 2007). During the Triassic, a rifting phase related to the Mesozoic break-up of the Pangea supercontinent commenced in the Artic-North Atlantic and between Greenland and Scandinavia (Lott et al., 2010). During the Jurassic, an eastern branch of the incipient rift basins/structures protruded into the North Sea area (Ziegler 1988, 1990). As such the structural outline of the Netherlands progressively changed from a single large basin, the Southern Permian Basin, into a multi-basinal pattern during the Late Jurassic (Wong, 2007; Fig. 3).
The slow regional subsidence in pre-rift (Early Jurassic) times led to the accumulation of the predominantly marine argillaceous deposits of the Altena Group. In general, regional extension was east-west directed. An uplift phase ended the largely uniform subsidence and sheet-like deposition of Middle Jurassic sediments. This uplift, related to the development of a thermal dome in the central North Sea area during the Aalenian to Bathonian (Mid-Kimmerian tectonic phase), caused wide- spread erosion and non-deposition (Underhill & Partington, 1993; Andsbjerg & Dybkjaer, 2003). It created a hiatus between the Late Jurassic and underlying Middle to Early Jurassic or older strata in the northern Dutch offshore. In the Middle Callovian, rifting starts in the Dutch area and continues until the base of the Valanginian. At first, rifting only affected the relatively narrow area of the graben axis. This phase is referred to as Sequence 1 in Abbink et al. (2006). During the Late Kimmeridgian, a change in the tectonic regime occurs in the southern North Sea. Extension direction changes from E-W to SW-NE (Zanella & Coward, 2003). Numerous old lineaments/ structures were rejuvenated, which resulted in the opening of the Terschelling Basin and the Step Graben as peripheral basins of the Central Graben and initiates the end of subsidence in some parts of the Central Graben. This phase coincides with Sequence 2 in Abbink et al. (2006). During this phase, the Terschelling Basin was filled with locally more than 2000 m thick siliciclastic sediments belonging to the predominantly non-marine Schieland Group and the marine Scruff Group (e.g. Duin et al., 2006). During the third phase, adjacent platforms, like the Schill Grund and Cleaver Bank Platforms were flooded. This phase, occurring around the Jurassic-Cretaceous boundary, is referred to as Sequence 3 in Abbink et al. (2006). Sequences 2 and 3 are relatively thick in the Terschelling Basin as compared to the Central Graben. Moreover, hiatuses occur during Sequence 2 and 3 in the Central Graben, but deposition of Sequence 2 and 3 was continuous in the depocentre of the Terschelling Basin (Abbink et al., 2006). In the Early Cretaceous, at the end of the Ryazanian, rifting came to a halt. Fault activity in the Graben area gradually ceased and the succeeding shallow marine sandstones and shales of the Early Cretaceous Rijnland Group effectively blanket the former graben and platform areas. From then on, the southern Graben basin is subjected to thermal subsidence. Because the subsidence is then no longer limited to the Graben area, it is reflected in a large-scale regional transgression (Copestake et al., 2003). This “Sequence 4” is referred to as the ‘Cretaceous transgression’ and starts in the Valanginian.
|Sedimentation of the Schieland Group (Central Graben Subgroup) in the Dutch Central Graben commenced in the Middle to Late Callovian G.2 (see pdf) . The sandy fluvial plain sediments of the Lower Graben Formation covered the erosion surface, mostly consisting of Lower to Middle Jurassic Altena Group sediments.The upper part of the succession in particular shows a near coastal marine setting, consistent with the inferred J46 MFS sensu Partington et al. (1993) from the lamberti Ammonite Zone. The shift to the Middle Graben Formation in the Early Oxfordian reflects an instantaneous change to more fine-grained, lacustrine to marginal marine sedimentation. In the southern Dutch Central Graben deposition started in the Late Callovian with the sedimentation in restricted to shallow marine depositional environment. These deposits are lithostratigraphically categorised within the Rifgronden Member of the Friese Front Formation. During the Middle Oxfordian continental conditions (lower delta plain, lacustrine, lagoonal tidal flats, estuary and tidal channels, bay head deltas and mouthbars) returned, and prevailed throughout the Dutch Central Graben. Marine incursions were scarce, and were restricted to the far north during the rest of the Oxfordian.|
|The Bathonian-Callovian Mid-Kimmerian uplift practically terminated the deposition of the Altena Group in the Netherlands. But, while essentially non-marine Schieland Group deposition had already commenced in the Dutch Central Graben, deposition of the Brabant Formation (Altena Group, Oisterwijk Limestone Member) persisted into the Early-Middle Oxfordian in parts of the Roer Valley Graben and West Netherlands Basin (Haanstra (1963) ; NAM and RGD (1980) ). These deposits are overlain unconformably by floodplain deposits (Schieland Group, Nieuwerkerk Formation) of Late Oxfordian to Portlandian age, now preserved only as erosional remnants.|
|From the Late Oxfordian onwards, the open marine realm started to expand southwards into the Dutch Central Graben, first into block F03. Initially, a stacked prograding marginal marine barrier-island system (Upper Graben Formation) developed, behind which (F08-F14) a paralic delta-plain setting formed, which is represented by the Puzzle Hole Formation sediments. To the north of the barrier complex, the Kimmeridge Clay Formation represents the open-marine environment. The coastal sand-bars of the Upper Graben Formation in the F03-area drowned at the end of the Oxfordian. Thin coastal-barrier sand-beds are found locally in the uppermost parts of the Puzzle Hole Formation, suggesting the existence of a backstepping coastal-barrier system. To the south (F14-F17), the paralic Puzzle Hole Formation grades into a non-marine (coastal) delta plain facies (Friese Front Formation). Seismic and paleogeographic information suggests that the transitions from the Puzzle Hole Formation into the Kimmeridge Clay Formation and the Friese Front Formation were fault controlled.|
|In the northern part of the Central Graben, the Kimmeridge Clay Formation developed further southwards (F05 Block). Reconstruction of the sedimentation in the Middle Central Graben is limited due to the Subhercynian/ Laramide inversion in Blocks F08-F17. At the base of Sequence 2 (Late Kimmeridgian) marine deposition (Lies Formation) also flooded into the northern part of the Step Graben, transgressing deposits of the Zechstein Group. During the Kimmeridgian, the thus far scattered deposition of the Friese Front Formation in the southern Dutch Central Graben gradually became more widespread. In Sequence 2 (Late Kimmeridgian) the Terschelling Basin also opens with fluvial Friese Front Formation deposits. The depocentre of the Dutch Central Graben axis shifted to the peripheral basins due to a change in the tectonic regime (see geological history above).
Meanwhile the Broad Fourteens Basin also initiated rifting and widespread deposition commenced with the sandy fluvial-plain sediments of the Aerdenhout Member from the Breeveertien Formation (see pdf). It unconformably overlies deposits of the Altena or Upper Trias Groups.
In the Lower Saxony Basin (= Niedersachsen Basin (see pdf) ), deposition of the Basal Weiteveen Clastic Member also seems to have started in Sequence 2.
|In the latest Kimmeridgian, the first marine influence is shown in the southern Dutch Central Graben and Terschelling Basin, as testified by the deposition of the shallow marine Oyster Ground Member (Skylge Formation (see pdf) ). It is in conformable contact with the underlying main Friese Front Member. In the Terschelling Basin the Oyster Ground Member may interfinger with the main Friese Front Member. During the Early-late Middle Volgian a new transgression resulted in deposition of the Terschelling Sandstone Member, a foreshore to shoreface setting grading northwards into the shallow (to open-) marine Noordvaarder Member (in F15-F17-F18, G.2 (see pdf) ). These sand dominated successions were occasionally extensively deposited at the fringes of the Dutch Central Graben (e.g. B14 and F11).
The distribution of the open marine Kimmeridge Clay Formation is limited to the northern part of the Central Graben and decreases in size due to the inversion of the Central Graben axis. The depocentre of relatively open marine clays, had now shifted to the southernmost Central Graben, southern Terschelling Basin and northern Vlieland Basin (L03-L12; L02-M01) and refers to the Lies Member.
During this period, the Vlieland Basin was divided into two subbasins, separated by the Zuidwal volcanic dome (Herngreen, Smit and Wong (1991)). During the late Middle Volgian, marine conditions prevailed only in the northern subbasin, whereas the southern subbasin was characterised by terrestrial (lacustrine to lagoonal) deposition.
|During the Early-Middle Volgian, clastic deposition in the Lower Saxony Basin was periodically replaced by precipitation of evaporites and carbonates (evaporitic and marl members of the Weiteveen Formation (see pdf) ). These cycles may be correlated with cycles of coarser and finer clastics, occasionally with evaporites, in the Broad Fourteens Basin (Breeveertien Formation, several members (see pdf) ). In the Central Netherlands Basin (sometimes referred to by the obsolete name ’Voorthuizen subbasin’; Haanstra (1963) ), the lithofacies (carbonates, marls, evaporites, coal beds) of the Zurich Formation are similar to those of the Niedersachsen Group.|
|During the Late Volgian, marine conditions (Scruff Greensand Formation) briefly reached the entire Vlieland Basin (see pdf).
In the southern Dutch Central Graben and Terschelling basin the setting became more shallow, inducing the northward progradation of shallow marine spiculitic glauconite sands (Scruff Spiculite Member). In the northern Central Graben the basin becomes semi-enclosed and circulation started to stagnate, resulting in the deposition of bituminous claystones of the Clay Deep Member (Lutine Formation).
In the Lower Saxony Basin (see pdf), the Late Volgian shoaling trend is also reflected in as a hiatus on top of the Serpulite Member within the Weiteveen Formation. At the beginning of the Ryazanian, the deposition of evaporites and carbonates with minor clastics of the Weiteveen Formation was replaced by restricted marine to lacustrine deposition of the Coevorden Formation.
|In the Broad Fourteens Basin (Breeveertien Formation (see pdf) ) this overall regressive tendency is also reflected by a hiatus (subaerial exposure) between the coastal/fluvial plain Driehuis Mottled Claystone Member (Sequence 2) and the overlying coastal plain Bloemendaal Member (Sequence 3) showing brackish water conditions (e.g. in well K18-Kotter-14: Late Volgian-Early Ryazanian succession is absent).
This period is marked by the resumption of widespread deposition of the Nieuwerkerk Formation in the Roer Valley Graben and West Netherlands Basin (see pdf). Thick sequences of locally coarse fluvial-plain sediments were deposited on rapidly subsiding fault blocks in the axes of these basins. The depositional realm expanded gradually. Consequently, the basin margins were covered by only a thin veneer, or remained exposed.
|During the Ryazanian the deposition area of the Clay Deep Member (Lutine Formation) showing stagnant marine circulation in the northern Dutch Central Graben expanded southward into Block F05 and the Step Graben. The succession of the Lutine Formation superseded the Scruff Greensand Formation further South in the mid-Ryazanian (see pdf). Initially, sedimentation of the Scruff Greensand Formation resumed (Stortemelk Member) and subsequently succeeded up into the Late Ryazanian of the Vlieland Basin, where this unit is intercalated with lagoonal/lacustrine deposits of the Zurich Formation. In the Dutch Central Graben, differential subsidence gradually stopped by a general decrease of tectonic activity reflecting the final stages of rifting in the area. A more evenly distributed sedimentation pattern, associated with the post-rift sag, started. This is shown comparing the highly variable thicknesses of the sequences underlying the Stortemelk Member with the far more constant development of the post-rift sequence (Clay Deep Member, Stortemelk Member and Schill Grund Member). In the Late Ryazanian, mudstone deposition becomes dominant throughout most of the Dutch Central Graben area.
In the Broad Fourteens Basin, West Netherlands Basin and Roer Valley Graben highly differential subsidence patterns continued at least throughout the Valanginian.
In the Broad Fourteens Basin the lagoonal Neomiodon Claystone Member slightly unconformable (K10-event sensu Jeremiah et al., 2010) succeeded the underlying sandy Bloemendaal Member during the latest Ryazanian.
|Valanginian - Barremian|
|The Late Jurassic rift phase came to an end and coincides with the Cretaceous transgression (Sequence 4). This occurred by the end of the Ryazanian, albidum Ammonite Zone. The Dutch area became subjected to subsidence which is reflected in a regional transgression. The ongoing marine transgression simultaneously reached the Vlieland Basin, Broad Fourteens Basin and Lower Saxony Basin, where the first transgressive and coastal-barrier sands of the Vlieland Sandstone Formation (Friesland, Kotter, and Bentheim Sandstone Members, resp. G.2 (see pdf) , G.3 (see pdf) and G.4 (see pdf) ) were deposited. Deposition of the transgressive Kotter Member was followed by the regressive, lagoonal Helm Member (Breeveertien Formation, G.3 (see pdf) ), while the Friesland Member in the Vlieland Basin was followed by open-marine fines of the main Vlieland Claystone Formation G.2 (see pdf) . In the Lower Saxony Basin deposition of the Bentheim Sandstone Member was preceded by the open-marine Bentheim Claystone Member It was followed by the open-marine to lagoonal Ruinen Member G.4 (see pdf) .|
|The advancing transgression caused the Vlieland Basin (see pdf) to drown during the Valanginian. The coastline shifted to the Friesland Platform. In the central parts of the Broad Fourteens Basin (K18-Q01-P03) a stacked coastal-barrier complex was formed (Helder Member). In the central-northern West Netherlands Basin the fluvial Delft Sandstone Member and lagoonal Rodenrijs Claystone Member are the coastal/fluvial-plain equivalent of the coastal-barrier complex in the Broad Fourteens Basin. Inland fluvial-plain equivalents are found in the Roer Valley Graben and southern West Netherlands Basin (Nieuwerkerk Formation, Alblasserdam Member), and the Central Netherlands Basin and Noord Holland Platform (Zurich Formation).|
|The margins of the West Netherlands Basin (L16, P09, Q07) remained exposed until the Late Valanginian, when the transitional area into the West Netherlands Basin (Q07-Q14) was flooded. In the Dutch part of the Lower Saxony Basin the Late Valanginian and Early Hauterivian history is obscured by a hiatus, separating the Ruinen and Westerbork Members of the Vlieland Claystone Formation G.4 (see pdf) . This hiatus is also known from other areas, such as the Vlieland Basin (Herngreen, Smit and Wong (1991) , G.2 (see pdf) ) and West Netherlands Basin Haanstra (1963) .During the mid-Hauterivian transgressive phase, an increasing part of the West Netherlands and Central Netherlands Basins and various platform areas were incorporated into the marine realm (G.4 (see pdf) and G.5 (see pdf) ). The coast line shifted from the Broad Fourteens Basin to the West Netherlands Basin (G.3 (see pdf) and G.5 (see pdf) ), Central Netherlands Basins, Noord-Holland Platform, southern Friesland Platform and Groningen High, where a sheet of amalgamated transgressive and coastal-barrier sands was deposited (Rijn Member, Rijswijk Member and Friesland Member of the Vlieland Sandstone Formation) followed by marine fines (Vlieland Claystone Formation).|
|On the landward side of the Vlieland Sandstone Formation coastal-barrier system in the West Netherlands Basin and Roer Valley Graben (Rotterdam area), coastal/fluvial-plain and lagoonal deposition of the Delfland Subgroup (Nieuwerkerk Formation, Delft Sandstone Member and Rodenrijs Claystone Member, G.5 (see pdf) ) continued. Minor (restricted-) marine incursions have been recorded van Amerom, Herngreen and Romein (1976).|
|Over an increasing area condensed basinal sequences of shallow-marine claystones were deposited (Vlieland Claystone Formation, G.2 (see pdf) ). During the Hauterivian, the area of the marine basin expanded across the northern off-shore, Vlieland Basin, northern Friesland Platform, Lower Saxony Basin (Westerbork Member of the Vlieland Claystone Formation) and Broad Fourteens Basin. In the Lower Saxony Basin, intercalated sandstone deposits of mid-Hauterivian age ( Gildehaus Sandstone Member, G.4 (see pdf) ) reflect a period of coastal influence in this basin. In the most distal basin areas (Cleaver Bank High, Mid North Sea High) chalk-like marl deposition set in ( Vlieland Marl Member, G.2 (see pdf) ).|
|During the Barremian three transgressive-regressive sequences occurred. The first one (latest Hauterivian-Barremian) formed the Berkel Sand/Claystone and Berkel Sandstone Mbs. G.5 (see pdf) . Its maximum extension reached slightly further south than the mid-Hauterivian Rijswijk Member transgression. During the second Barremian transgressive pulse, the IJsselmonde Claystone and the IJsselmonde Sandstone Mbs. (Vlieland Claystone Formation, resp. Vlieland Sandstone Formation) were deposited, and the transgression reached the Rotterdam area. The Nieuwerkerk Formation realm retreated further south. Main Vlieland Claystone Formation was deposited on top of the Berkel sandstone complex. At the same time, the crest of the Texel-IJsselmeer High (see pdf) was gradually flooded. During the Late Barremian the area of marine deposition included virtually the entire West Netherlands Basin, as the Eemhaven Claystone Member (Vlieland Claystone Formation) was deposited. During the subsequent regressive phase (Late Barremian-Early Aptian), the progradational De Lier Member (Vlieland Sandstone Formation) was deposited along the south-ern margin of the West Netherlands Basin.|
Not yet classified in terms of sequences
|By Aptian and Albian times most of the Netherlands’ territory north of the line O-quadrant - Breda - Nijmegen was covered by outer-neritic shelf seas G.6 (see pdf) , reflected in the widespread Holland Formation. A relatively thin succession of marine marls and claystones was formed in most places, but in most of the southern Broad Fourteens and West Netherlands Basins a much thicker sequence, including Holland Greensand Member, was deposited. Along the southwestern rim of the West Netherlands Basin this open-marine sand deposit grades into a coast-al-sandstone equivalent (Spijkenisse Greensand Member)|
|Along the margin of the Lower Saxony Basin some areas were uplifted during the Albian (Coevorden area, also crest of the Texel-IJsselmeer High (see pdf) ), and the interval in other areas includes several poorly documented breaks in deposition, related to the (Late Aptian-Early Albian) Austrian tectonic phase. The deposition of the Holland Greensand Member and Spijkenisse Sandstone Member in the West Netherlands Basin is also linked to this tectonic event. The start of widespread chalk deposition during the Early Cenomanian is taken as the boundary between the Rijnland and Chalk Groups. In the southern half of the Netherlands the base of the Chalk Group is placed at the base of the Texel Greensand Member or its equivalents. The most complete successions of Holland Formation indicate that its deposition seems to have persisted into the earliest Cenomanian.|
|Several seismic examples of each described interval from various structural settings are included. Different colours have been used in these seismic lines, to discern typical seismic facies. Each one of these seismic facies represents the typical development of (part of) a litho-stratigraphic unit, and reflects a specific lithofacies association and depositional setting. It should be kept in mind that the given sections and their descriptions are not definitions, but examples. Depending on vintage and processing of seismic data, the described seismic facies may differ considerably. For the interpretation of the presented examples nearby well stratigraphies were tied in.|
|Northern-central Dutch Central Graben:|
|Figure G7 (see pdf) displays the seismic facies trend from the northern to the central part of the Dutch Central Graben. The seismic character of the Upper Jurassic in this province has been described by Herngreen and Wong (1989) . In the displayed section the following units can be discerned: Lower Graben Formation: high-amplitude, parallel reflections with relatively low frequency and medium continuity, characterised by two very high-amplitude, very continuous reflections. This unit is restricted to fault-controlled depressions.|
|Middle Graben - Upper Graben Formations:|
|low-amplitude, high-frequency parallel reflections, very continuous. Because of the low amplitudes, the unit is virtually transparant. This unit also shows two continuous, very high-amplitude, parallel reflections at its top. The lower one reflects the base Upper Graben Formation, while the upper one its contact with the Kimmeridge Clay Formation Towards the south, where the Upper Graben Formation grades into the Puzzle Hole Formation, the two parallel reflections diverge as the interval becomes thicker see figure G.9 (see pdf) .|
|Kimmeridge Clay - Scruff Greensand Formations:|
|often very thick, but variable interval, mostly low-amplitude, high-frequency reflections of very high continuity, parallel, divergent, or sigmoidal. Internally repeated trends of increasing amplitude can be observed. This unit often displays an internal unconformity, downcutting towards the western flank of the Dutch Central Graben figure G.8 (see pdf) . In synclines the top can display a sudden decrease in reflection amplitude. This marks the onset of the Scruff Greensand Formation Very rarely a thin, transparant interval at the very top of these occurrences marks the Clay Deep Member or Schill Grund Member of the Kimmeridge Clay Formation|
|Puzzle Hole - Friese Front Formations:|
|package of highly variable thickness, with high amplitude, relatively low frequency, parallel reflections of moderate to high continuity. This unit represents the Puzzle Hole and Friese Front Fms. in the southern-central part of the Central Graben. Figure G.7 (see pdf) clearly shows how the lateral transition between the Kimmeridge Clay Formation and the Puzzle Hole Formation was tectonically fixed for a long time, approx. at mark A. At mark B it shows the fault-controlled transition from the Puzzle Hole Formation realm to that of the Friese Front Formation|
|Vlieland Claystone - Holland Formations:|
|characterised by a very thin package of parallel or wavy reflections of high amplitude, low frequency and high continuity. Especially the Holland Formation is marked by very high-amplitude, low- frequency, continuous reflections separated by varying transparant zones.|
|Southern Dutch Central Graben|
|Figures G.10 (see pdf) and figure G.11 (see pdf) roughly represent the southward continuation of figure G.7 (see pdf)|
|Friese Front Formation:|
|Figure G.11 (see pdf) demonstrates the loss of reflector continuity in the Friese Front Formation towards the south, marking the transition from paralic to fluvial-plain deposits. In addition, it displays the complex sigmoidal-oblique fill of this basin. Figure G.10 (see pdf) shows the transparant character of the unconformable, basal Rifgronden Member (lagoonal to lacus-trine) of that formation.|
|Scruff Greensand Formation:|
|Both figures show the southward thinning (convergence) of the Scruff Greensand Formation This thinning is accompanied by reflectors with increasing amplitude and conti-nuity, and decreasing frequency. In figure G.11 (see pdf) an unconformity can be observed at the base of this unit, and here only the Stortemelk Member of the Scruff Greensand Formation is present.|
|Vlieland Claystone - Holland Formations:|
|compared to the northern Dutch Central Graben (figure G.7-G.8 (see pdf) -figure 9 (see pdf) ), the Vlieland Claystone Formation is developed thicker here, with a divergent, shingled to subparallel character. The amplitudes are more varied. Reflections marking disconformities (sequence boundaries) have higher ampli-tudes. Continuity and frequency remain high. The thin Holland Formation displays very high-amplitude, low-frequency, continuous reflections separated by varying transparant zones.|
|Figure G.12 (see pdf) shows the Upper Jurassic-Lower Cretaceous development in the northern part of this basin.|
|Kimmeridge Clay Formation:|
|mildly unconformable, transparent, wavy, moderate to high continuity ( Zurich Formation, Lower Member in the southern part of the basin.|
|Scruff Greensand Formation:|
|interval with lenticular, high-frequency, low-amplitude reflections.|
|Zurich Formation (Upper Zurich Member):|
|continuous, high-amplitude, low-frequency reflections.|
|Vlieland Sandstone Formation (Friesland Member):|
|this unit cuts into the Zurich Formation, and is represented by a sequence of almost transparant, low-amplitude reflections of fairly high frequency and moderate continuity.|
|Vlieland Claystone and Holland Formations:|
|transparent, moderate to high-continuity, high-frequency facies. In this interval the more prominent and continuous reflections mark sequence boundaries.|
|Lower Saxony Basin and Central Netherlands Basin|
|Not depicted. The Upper Jurassic-lowermost Cretaceous (Zurich Formation or Niedersachsen Group) is restricted to erosional remnants, such as rim synclines. Seismic facies resemble those of the Vlieland Basin. A gradual onlap of the Rijnland Group (Vlieland Sandstone Formation, covered by Vlieland Claystone Formation) is seen. Locally (Coevorden-Schoonebeek area) the Holland Formation rests unconformably on older rocks, down to Triassic.|
|Broad Fourteens Basin|
|The typical development in this basin can be seen in figure G.13 (see pdf)|
|Breeveertien Formation (Delfland Subgroup):|
|is a mildly unconformable, onlapping unit of moderately continuous shingled, divergent or parallel reflections with moderate to low amplitude and high to low frequency. More transparent intervals usually represent the claystone members, while sandstone members tend to show a more pronounced, hummocky character, with many internal truncations.|
|Vlieland Sandstone Formation:|
|mildly unconformable, onlapping unit with low frequency, low-moderate amplitude, shingled or oblique parallel reflections. Towards the east the basal interval grades into a unit of high amplitude, parallel reflections, formed by the lagoonal Helm Member of the Breeveertien Formation|
|Vlieland Claystone Formation:|
|fairly transparent unit of low amplitudes and high conti-nuity. In some parts reflections have a higher-amplitude, parallel character.|
|frequently absent in this area, but where present can be thick and tends to have a continuous, parallel character, with higher amplitudes.|
|West Netherlands Basin|
|Figures G.14 (see pdf) and G.15 (see pdf) display the western, resp. eastern development of this basin. The major difference between the two is the structural style. The eastern part is intensely faulted, and this pattern was already present during the depositon of the Upper Jurassic.|
|Nieuwerkerk Formation (Delfland Subgroup):|
|especially in the lower parts, differential deposition in various fault blocks is important. Seismic facies of the Nieuwerkerk Formation can be differentiated into two subfacies:|
|- irregular, discontinuous hummocky clinoforms of moderate to low amplitude (’wormy’ facies), represent-ing sand-dominated braided fluvial deposits, often showing a mounded character in downthrown blocks with a thick development (valley fills, see G.15 (see pdf) ); - a more transparant facies with some very contigh-amplitude reflections, representing flood-plain or lacustrine fines, and some intercalated high-sinuosity fluvial intervals.|
|Vlieland Sandstone and Vlieland Claystone Formations:|
|comparable to the development in the Broad Fourteens Basin, although considerably thinner here, as a result of the later start of deposition.|
|thick in the western section, with internal disconformities. The character is comparable to the Broad Fourteens Basin.|
|Structural element||Late Jurassic to Early Cretaceous structural elements
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|Chronostratigraphy||Aptian-Albian litho-chronostratigraphic chart through the Netherlands' territory
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|Late Jurassic - Early Cretaceous (pre-Aptian) Graben litho-chronostratigraphic chart through the Broad Fourteens Basin
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|Late Jurassic - Early Cretaceous (pre-Aptian) Graben litho-chronostratigraphic chart through the Lower Saxony Basin
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|Late Jurassic - Early Cretaceous (pre-Aptian) litho-chronostratigraphic chart through the West Netherlands Basin
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|Late Jurassic - Early Cretaceous (pre-Aptian) litho-chronostratigraphic chart through the Vlieland Basin, Terschelling Basin and Dutch Central Graben
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|References||See References Upper Jurassic/ Lower Cretaceous|
D.K. Munsterman, R.M.C.H. Verreussel, H.F. Mijnlieff, N. Witmans, S. Kerstholt-Boegehold & O.A, Abbink (2012), Revision and update of the Callovian-Ryazanian Stratigraphic Nomenclature in the northern Dutch Offshore, i.e. Central Graben Subgroup and Scruff Group. Netherlands Journal of Geosciences-Geologie en Mijnbouw, 91 (4):555-590.