new insights into salt tectonics in the northern dutch offshore a framework for hydrocarbon exploration the northern dutch offshore is an area that has seen less hydrocarbon exploration activity than other areas of the netherlands acquisition of a new regional 3d seismic dataset allowed further testing and re evaluation of established geological concepts in this area it is recognized that the presence and movement of upper permian zechstein evaporites had a major impact on depositional patterns in mesozoic sediments structural development and hydrocarbon migration as such this study looks specifically at the role of salt tectonics in tectonosedimentary development to assess this salt tectonic evolution within its structural context a restoration of the step graben and dutch central graben was performed it follows that depositional patterns are closely linked to the nature of salt structure movement and the timing of regional tectonism for example during late triassic rifting salt pillows developed and sedimentation focused away from salt structures into depocentres along regional fault trends restoration results show that this interplay between salt movement and tectonism is needed to accommodate the sedimentation patterns associated with the formation of the step graben and central graben during the triassic and jurassic and later during late cretaceous and cenozoic inversion tectonics 2018 the author s

north sea rift system abstract the mesozoic north sea rift forms an integral part of the arctic north atlantic rift system rifting activity in the north sea commenced during the earliest triassic during the mid jurassic the central north sea underwent a temporary doming stage crustal extension peaked during the late jurassic earliest cretaceous abated subsequently and terminated altogether during the paleocene the saucer shaped cenozoic post rift basin straddles the axis of the viking and central grabens this speaks for the applicability of a depth dependent pure shear model rather than a simple shear model geophysical data indicate an important discrepancy between upper and lower crustal attenuation across the north sea rift suggesting that during rifting processes the mono discontinuity was seriously destabilized this requires a basic modification of currently favoured crustal stretching models

implications of continuous structural inversion in the west netherlands basin for understanding controls on palaeogene deformation in nw europe a detailed analysis of high quality 3d seismic and borehole data provides new insights into the palaeogene tectonic history and inversion of the west netherlands basin the inversion characteristics are compared with those of other basins in the region to provide constraints on the palaeogene compressional tectonic movements in nw europe the inversion of the west netherlands basin which is characterized by the doming of the basin centre and by the reactivation of pre existing faults in a reverse mode was found to be the result of a continuous inversion process rather than a distinct tectonic pulse the intensity of the tectonic movements was not uniform throughout the eocene and was strongest during the latest eocene these characteristics are similar to those of other basins in the southern north sea region and in the english channel area in addition a good correlation exists between alpine tectonic events and the palaeogene inversion phases in light of these observations the latest eocene inversion pulse in the southern north sea region can be considered as the culmination of a long term inversion process that originated from the alpine collision

formation of ripples in erodible channels formation of ripples and dunes in erodible channels is analyzed by using the hydrodynamic model developed by kobayashi and madsen this issue applying the continuity equation of sediment the propagation velocity of the wavy bed is expressed in terms of the net fluxes of bed load along the wavy bed and suspended sediment out of the bed load transport layer the spatial variation of the bed load transport rate is derived by analyzing the balance of forces acting on a representative bed load particle on a sloping bed the net flux of the suspended sediment out of the bed load transport layer is obtained by solving the diffusion equation for the suspended sediment near the bed the stability analysis predicts that a perturbation that is either fairly short or long relative to the depth of flow will initially grow depending on whether the flow is hydraulically smooth or fully rough thus the model explains why ripples are not observed in experiments involving fairly coarse sediments since in these cases the flow is rough turbulent

data mining in the dutch oil and gas portal a case study on the reservoir properties of the volpriehausen sandstone interval this paper presents the results of a data mining exercise on core measurements and reports of the triassic lower volpriehausen sandstone member rbmvl in the netherlands the availability of a large accurate online dataset via the dutch oil and gas portal nlog enables the definition of general reservoir property trends on a regional subregional scale accurately defined trends are capable of restricting the uncertainty range of key parameters in exploration studies e g porosity and permeability and thus of reducing risk plotting core porosity v core permeability resulted in a curved data cloud on a log normal plot although porosity permeability relationships are often defined by straight lines the dataset in this study shows that a curved relationship results in a better fit with permeability measurements over the entire porosity range two methods were applied to define a porosity depth relationship for sandstones of the rbmvl the results of both methods confirm and enable quantification of the well known trend of decreasing porosity with depth by assigning grain density attributes to the core measurements the dependency of the porosity depth relationship on sedimentary facies and diagenesis type grade could be determined this case study demonstrates the power of this free online dataset in understanding reservoir quality 2018 the author s

mesozoic resource potential in the southern permian basin area the geological key to exploiting remaining hydrocarbons whilst unlocking geothermal potential it is generally accepted that hydrocarbon exploration in northern europe has reached a mature stage a basin s maturity is defined by the underlying number of new discoveries and the declining production rate of mature fields spe 2015 for geoscientists a mature basin has well defined characteristics in terms of for example reservoir presence or trap formation e g byrne 2012 it is interesting therefore to note how much is still unknown about certain stratigraphic intervals in northern europe the mesozoic overburden of the southern permian basin sensu maystrenko et al 2008 doornenbal stevenson 2010 continues to provide fresh insights into the geological history of an area where as the name suggests historical hydrocarbon exploration has focused on the paleozoic the aim of this special publication is to increase knowledge of the mesozoic overburden as a driver for further hydrocarbon exploration production and the development of new geothermal energy sources the succeeding chapters are introduced by tectonic framework overviews that give a context for the papers that follow the remaining articles are organized in approximate stratigraphic order from old to young and include a variety of examples from semi regional to localized field or sub basin studies an overview of the study area for all the following chapters is given in figure 1 it is recognized that the overprinting mesozoic systems have different naming conventions across the study area e g the central european basin system sensu littke et al 2008 maystrenko et al 2008 here we use the title southern permian basin area to emphasize the resource opportunities associated with a region that has at least in large part been associated with hydrocarbon exploration and very large gas fields in the permian rotliegend for our purposes this includes part of the polish trough the highs surrounding the basin e g the ringkobing fyn high and analogous elements of the danish and norwegian offshore in this introduction an overview of the geological history and resource base of the area is presented as a framework for the chapters that follow a description of further prospective resources is then offered oil and gas plus geothermal potential

cross section restoration of salt related deformation best practices and potential pitfalls abstract cross section restoration typically assumes plane strain deformation and area conservation constraints that are usually invalid for salt because of its characteristic three dimensional flow and possible dissolution thus restoration of salt related deformation provides added challenges and uncertainty in this review paper we summarize the historical development of ideas methods and applications of restoration in salt basins while most published restorations do not maintain salt area constraints on its variation range from arbitrary assumptions to quantitatively incorporating isostatic calculations we illustrate several scenarios in which the presence of salt adds ambiguity to restoration primarily because it can hide deformation diapirs can widen during extension and narrow during shortening translating overburden can move into salt and drive allochthonous advance secondary minibasin subsidence can be accommodated at both shallow and deep salt levels and allochthonous salt can record evacuation of deeper salt although we caution against using restoration to test and validate small scale details of interpretations we emphasize that sequential restoration remains an essential tool in structural and basin analyses however because of the uncertainties a regional three dimensional approach and sound geological reasoning are critical for deriving meaningful and useful results from cross section restoration of salt structures

unsteady flow in straight alluvial streams part 2 transition from dunes to plane bed the effect of suspended sediment on the modification of individual dunes in unsteady channel flow is analyzed the model is an extension of that developed by fredsoe 1979 in which the change of the dune dimensions was analyzed assuming that the transport of sediment mainly occurs as bed load by including suspended sediment it is possible to describe dune behaviour at high sediment transport rates for which the dunes are washed out so the bed at sufficiently high bed shear stress becomes plane the model is compared with laboratory experiments and the agreement is reasonable the effect of temperature variations on dune dimensions is incorporated in the analysis

interaction between bottom currents and slope failure in the late cretaceous of the southern danish central graben north sea the nw european chalk group was deposited in a deep epicontinental sea traditionally conceived as a quiet depositional setting that was only affected by redeposition along structural highs the chalk sea was however locally affected by powerful bottom currents during some periods three dimensional seismic reflection data from the southern central graben show abundant intra chalk morphological elements concentrated at two stratigraphic levels within the turonian campanian sequence both levels are topped by extensive unconformities the geometry of the elements produced by alongslope processes is interpreted as caused by se directed bottom currents flowing between the bo jens and adda ridges the highest current intensities led to the formation of the two unconformities judged by the occurrence of the largest current formed channels and drifts at these two stratigraphic levels this sea floor topography was locally modified by large scale downslope mass transport stratigraphical coincidence of the largest slumps and bottom current erosion suggests a coupling between downslope and alongslope processes current erosion impinged upon the slopes during periods of highest current speeds destabilizing the slope sediments and triggering slumping the smoothing of the bathymetry following local relaxation of the tectonic inversion accounted for the coeval deactivation of alongslope and downslope processes during the succeeding maastrichtian deposition

tectonostratigraphy of a rift basin affected by salt tectonics synrift middle jurassic lower cretaceous dutch central graben terschelling basin and neighbouring platforms dutch offshore the middle jurassic lower cretaceous in the eastern dutch offshore provides excellent examples of sand rich sediments that locally accumulated in the vicinity of rift basin margins affected by salt tectonics these types of deposits are often geographically restricted and difficult to identify but can be valuable targets for hydrocarbon exploration the distribution thickness and preservation potential of fluvio lacustrine shallow and deep marine sediments is discussed to provide new insights into the regional and local tectonostratigraphy of the dutch central graben the terschelling basin and their neighbouring platforms new sedimentological geochemical biostratigraphic stratigraphic and structural information have been analysed and integrated into a new tectonostratigraphic model for the callovian lower graben formation oxfordian middle and upper graben formations early middle volgian terschelling sandstone and noordvaarder members and the late volgian early ryazanian scruff greensand formation it is demonstrated that salt withdrawal at the basin axis was the primary control on the generation of high accommodation during the callovian early kimmeridgian incised valleys developed on the platforms providing lateral sediment input during the late kimmeridgian ryazanian salt migration shifted laterally towards the basin margins providing accommodation adjacent to active salt bodies and deposition of overthickened sandy strata

inversion of the broad fourteens basin offshore netherlands a small scale model investigation abstract the southern north sea exhibits spectacular examples of graben inversion which have been extensively documented by oil industry exploration the broad fourteens basin which is located at the southern limit of the southern permian salt basin displays numerous structural patterns of positive inversion which are related to the inversion which are related to the presence and thickness of zechstein salts in the northern part of the broad fourteens basin the zechstein salt is rather thick 500 m allowing decollement of the mesozoic series during both extension and compression salt is missing to the southern part of this graben and both mesozoic series and palaeozoic basement display similar patterns of deformatiqn the mechanical significance of inversion patterns was investigated through laboratory experiments on brittleductile models models were built with sand and silicone putty that represent respectively the frictional behaviour of the mesozoic cover as well as the palaeozoic basement and the viscous behaviour of a decollement layer mainly composed of zechstein salts which is intercalated between them the models were scaled to fit natural configurations observed in the broad fourteens basin all small scale experiments were carried out in two steps 1 graben formation with synkinematic sedimentation and 2 compression at various angles of obliquity to the graben experimental results show that the structures generated by or reactivated during inversion are strongly dependent on a the strength of the decollement layer which is a function of the layer thickness and of the displacement velocity applied at the model boundaries and b the strength of the sedimentary overburden which is a function only of its thickness for a given lithology reactivation of normal faults occurs when the angle between the compression and the direction of the normal faults is smaller than 45 the ductile layer which can be a source for diapirs during extension plays during compression an important ro1e in the thrusting of the graben fill onto the adjacent platforms

triassic rifts and facies patterns in western and central europe the triassic evolution of western and central europe was governed by regional crustal extension that induced the subsidence of a complex network of grabens and troughs these formed an integral part of the arctic north atlantic and the tethys central atlantic gulf of mexico rift and rift wrench systems which in the course of the mesozoic and cenozoic developed into major break up axes of pangea

geological evolution of the chalk group in the northern dutch north sea inversion sedimentation and redeposition in contrast to the norwegian and danish sectors where significant hydrocarbon reserves were found in chalk reservoirs limited studies exist analysing the chalk evolution in the dutch part of the north sea to provide a better understanding of this evolution a tectono sedimentary study of the late cretaceous to early palaeogene chalk group in the northern dutch north sea was performed facilitated by a relatively new 3d seismic survey integrating seismic and biostratigraphic well data seven chronostratigraphic units were mapped allowing a reconstruction of intra chalk geological events the southwestward thickening of the turonian sequence is interpreted to result from tilting and the absence of coniacian and santonian sediments in the western part of the study area is probably the result of non deposition seismic truncations show evidence of a widespread inversion phase the timing of which differs between the structural elements it started at the end of the campanian followed by a second pulse during the maastrichtian a new finding not reported before after subsidence during the maastrichtian and danian renewed inversion and erosion occurred at the end of the danian halokinesis processes resulted in thickness variations of chalk units of different ages in summary variations in sedimentation patterns in the northern dutch north sea relate to the sub hercynian inversion phase during the campanian and maastrichtian the laramide inversion phase at the end of the danian and halokinesis processes additionally the late cretaceous sea floor was characterized by erosion through contour bottom currents at different scales and resedimentation by slope failures

linking changes in tectonic style with magmatism in northern europe during the late carboniferous to latest permian abstract early carboniferous to permian magmatism associated with rifting within the northern foreland of the variscan orogen was widespread across europe during the long period of magmatic activity the regional tectonic setting changed across the region from early carboniferous extension and basin formation to a rifting wrenching style of deformation in the late carboniferous stephanian to early permian wrenching and faulting were accompanied by widespread voluminous and episodic magmatic extrusion intrusion and underplating this was followed by thermal relaxation and the development of the northern and southern permian basins in later permian times thermal relaxation was punctuated by a permo triassic phase of extension and graben formation 40ar 39ar ar step heating dating for mineral separates and whole rock samples of magmatic rocks from southern scandinavia oslo graben and south sweden and rugen north germany provides further radiometric evidence for three of the proposed periods of magmatic activity in the region latest carboniferous to earliest permian ages c 300 310 ma were obtained for volcanic rocks in the oslo graben and dolerite sills and dykes in south sweden and north germany this phase can be time correlated with magmatic activity that occurred throughout europe during large scale dextral wrenching that followed the variscan orogeny a second phase of alkaline intrusions is confined to the oslo graben and related to caldera collapse around c 275 ma the third permo triassic phase c 250 ma is considered to be related to a new tectonic cycle involving extension that triggered minor melting of enriched fertile mantle

permo carboniferous magmatism and rifting in europe introduction an extensive rift system developed within the northern foreland of the variscan orogenic belt during late carboniferous early permian times post dating the devonian early carboniferous accretion of various neoproterozoic gondwana derived terranes on to the southern margin of laurussia laurentia baltica fig 1 rifting was associated with widespread magmatism and with a fundamental change at the westphalian stephanian boundary in the regional stress field affecting western and central europe ziegler 1990 ziegler cloetingh 2003 the change in regional stress patterns was coincident with the termination of orogenic activity in the variscan fold belt followed by major dextral translation between north africa and europe rifting propagated across a collage of basement terranes with different ages and thermal histories whilst most of the carboniferous permian rift basins of nw europe developed on relatively thin lithosphere the highly magmatic oslo graben in southern norway initiated within the thick stable and presumably strong cold lithosphere of the fennoscandian craton the rift basins in the north sea in contrast developed in younger caledonian age lithosphere which was both thinner and warmer than the lithosphere of the craton to the east

overburden deformation patterns and mechanisms of salt diapir penetration in the central graben north sea abstract active and passive diapirism control the deformation and geometry of hydrocarbon traps in the overburden and a more detailed understanding of this process will help reservoir prediction and hydrocarbon recovery cores studies of seven central graben diapirs indicate zechstein salt penetrated late cretaceous chalk by extreme tectonic thinning with high angle 70 to bedding normal faulting tensile fracturing and pressure solution attenuation of the chalk significantly weakens the overburden allowing buoyancy forces to dome up the overburden doming created enough topography for downslope sliding of chalk slabs on slip planes parallel to bedding or in the case of the kyle diapir for chaotic debris flows of lithified chalk significant extensional bedding parallel faults and slump folds are developed within palaeocene shale on the diapiric flanks inter granular slip in unconsolidated clastic material was probably the dominant deformation mechanism diapirs have penetrated the palaeocene clastic sediments by maintaining topographic relief so that unlithified sediment continually slid off the crest producing translated intact rafts up to several tens of metres in thickness

stepwise basin evolution of the middle jurassic early cretaceous rift phase in the central graben area of denmark germany and the netherlands this paper presents the results of a cross border study of the middle jurassic early cretaceous rift phase in the danish german dutch central graben area based on long distance correlations of palynologically interpreted wells a stepwise basin evolution pattern was determined four phases are defined and described as tectonostratigraphic mega sequences tms the tms are governed by changes in the tectonic regime tms 1 reflects the onset of rifting triggered by regional east west extension rift climax was reached during tms 1 reflected by thick mudstone accumulations tms 2 reflects a change in the tectonic regime from east west to ne swextension nw se trending normal faults became active during this phase switching the depocentres from the graben axis into adjacent basins tms 3 displays divergent basin development in the dutch central graben area it is characterized by a basal unconformity and widespread sandstone deposition indicating continued salt and fault activity organic rich mudstone deposition prevails in the danish and german central graben area indicating sediment starvation and water mass stratification with tms 4 the rift phase ended reflected by regionally uniform mudstone deposition the basin evolution model presented here coherently places the lithostratigraphic units occurring in a stratigraphic framework and provides a valuable basis for hydrocarbon exploration activities in the region

structural evolution of inverted basins in the dutch offshore abstract the structural evolution of the dutch central north sea graben and the fault bounded broad fourteens basin is discussed graben formation started during the early triassic and culminated in strong differential subsidence during the late jurassic early cretaceous narrow fault bounded grabens and troughs and broad intervening highs were formed as a result of crustal distension and associated transtensional deformations the thickness of the late jurassic to early cretaceous fill of these basins may have exceeded 3000 m concurrent with the filling of these basins the bordering highs became deeply truncated during the late cretaceous and early tertiary compressive stresses resulted in inversion of these basins whereby movements along their bounding normal faults were reversed giving rise locally to overthrusting as for instance in the broad fourteens and west netherlands basins the timing of these compressional deformations has been palaeontologically dated and coincides with major orogenic events in the alps

upper permian zechstein microbialites supratidal through deep subtidal deposition source rock and reservoir potential zechstein 2 z2 carbonate microbialites flourished under arid paleoclimatic conditions in the late permian microbial carbonates from the roker formation outcrop in northeast england with its subsurface equivalent being the main dolomite from northwest central poland the z2 carbonate deposits developed in supratidal through deep subtidal zones and consist of various stromatolites and thrombolites planar stromatolites and thrombolites characterize intertidal and supratidal facies and biohermal stromatolites with oolitic grainstone and crinkled stromatolites typify shallow subtidal facies the z2 subtidal and or intertidal microbialites with oolites form complexes more than 10 m 33 ft thick and are important reservoir facies for hydrocarbons subtidal slope and intertidal lagoonal microbial mudstone and wackestone have poor reservoir properties but contain total organic carbon as much as 2 wt and are considered as potential source rocks the thermal maturity assessed from c27 17 trisnorhopane tm and c27 18 trisnorhopane ts as the ts ts tm ratio c30 moretane hopane ratio sterane ratio expressed as 20s 20s 20r and ratio shows to indicates a mature character of organic matter with respect to oil generation

on the origins of eogenetic chlorite in verdine facies sedimentary rocks from the gabon basin in west africa abstract the verdine facies clay assemblages are regularly encountered in shallow marine sediments of equatorial latitudes where fe of terrigenous origin is readily available there the 7 a fe rich green clay odinite of syn sedimentary origin commonly occurs previous findings suggested that odinite serves as a precursor of diagenetic chlorite whose importance in porosity conservation has been widely acknowledged the investigation of fe rich clays is therefore helpful to constrain the specific conditions and mechanisms which give rise to chlorite growth thus illuminating the history of early burial in this contribution we studied cretaceous sediments from the gabon coast where multiple sedimentary basins came into existence prior during and after the opening of the south atlantic analyzed core is siliciclastic and petroleum bearing stemming from the fluvio lacustrine deltaic environment recovered from depths of 1500 m tvd electron micro beam investigation coupled with x ray diffraction on the clay fraction and spectra fitting revealed odinite interstratified odinite chlorite o c and to a lesser extent illite chlorite smectite i c s and illite smectite occur as grain coatings and pore filling phases with a characteristic honeycomb texture embryonic chlorite emerges at the contact of odinite and o c flakes as a particulate authigenic mineralization formed from aluminosilicate and fe oxyhydroxide debris at sediment water interface odinite becomes intrinsically unstable possibly due to the activity of fe reducing bacteria or decaying organic matter creating a prevalently reducing environment that promotes fe reduction such condition facilitated a two step chlorite growth which first included a partial chloritization of odinite through the in situ solid state transformation of 7 a to 14 a layers then with increasing burial at peak diagenetic conditions 50 c 1 5 km depth odinite and o c both recrystallized to form eogenetic chlorite most likely following the ostwald ripening mechanism

geological history and petroleum system of the mittelplate oil field northern germany the geological history of germany s largest and most productive petroleum accumulation the mittelplate oil field in schleswig holstein northern germany is reconstructed by simulating the structural and thermal evolution along a 2d cross section the mittelplate field is located at the western flank of the busum salt dome at the transition from the schleswig holstein mainland to the german north sea sector organic geochemical data confirm the lower jurassic posidonia shale to be the predominant oil source rock in the schleswig holstein area the studied section is characterized by salt walls and salt domes built up by permian evaporites reconstruction of the structural and thermal evolution of the mittelplate field by means of basin modelling reveals the dominating influence of salt dynamics on the entire petroleum system the development of secondary rim synclines during salt rise provided accommodation space for the deposition of the posidonia shale as well as the deltaic middle jurassic reservoir sandstones the rise of the nearby oldenswort salt wall controlled the timing of maturation and petroleum generation during cenozoic times hydrocarbon migration from the posidonia shale into the reservoirs occurred up dip from the deeper subsiding rim syncline into the structural trap with the middle jurassic reservoir sandstones pinching out at the flank of the busum salt dome along the modelled 2d section the field s recent temperature field and its complex reservoir architecture are reconstructed