simulation of curved open channel flows by 3d hydrodynamic model a mathematical model of three dimensional 3d free surface flows has been applied to simulate the curved channel flows and mass transport in the horizontal plane a channel fitted curvilinear coordinate system is used whereas in the vertical plane the transformation is adopted to track the free surface and variable bed topography to reduce the numerical diffusion the second order upwind scheme of roe is incorporated to discretize the convection terms the standard k e model has been modified to take account of some anisotropic effects appearing in shallow curved channels i e streamline curvature and the damping effects of free surface and solid walls the governing equations are solved in a collocated grid system by a fractional three step implicit algorithm two test cases from curved flumes have been studied 1 a 270 channel bend with a sloped outer bank and 2 a meandering channel with mass transport the results are compared with the available data which shows generally good agreement

interaction between aeolian fluvial and playa environments in the permian upper rotliegend group uk southern north sea the permian upper rotliegend group in offshore uk quadrants 42 43 47 and 48 comprises a sequence of mixed aeolian fluvial playa deposits these deposits are up to 300 m thick and contain a record of the interaction between desert fluvial systems and adjacent aeolian and playa environments the relative dominance of water vs wind transport and deposition in this stratigraphic package was a function of fluctuations in the discharge of ephemeral fluvial systems and changes in water table playa level driven by a combination of climatic change and syndepositional tectonics the rotliegend sedimentary record is punctuated by numerous surfaces recording erosion by wind and water the origin of these surfaces is mostly climatic with periods of increased runoff resulting in fluvial incision especially near active faults during periods of reduced runoff wind erosion of fluvial deposits occurred with fluvially derived sand being reworked into expanding aeolian dune fields wind erosion also occurred as a rising water table isolated dunes from their sediment supply resulting in deflation of dunes down to the water table these surfaces formed in a basin that was subsiding thus even in a background of overall increasing accommodation space climatically driven falls in the water table allowed for periods of erosion the occurrence of significant erosion especially near syndepositional fault zones resulted in a sedimentary record that shows pronounced lateral as well as vertical facies variations

analytical solution of a model of contaminant transport in the advective zone of a river abstractan analytical solution of a model of contaminant transport in the advective zone of rivers is presented and evaluated an existing model that accounts for transport in the advective zone by dividing the channel into flowing and stagnant zones is solved with laplace transforms for the case of a gaussian pulse injected into the center of the channel the effects of the two main parameters of the model the fraction of the channel occupied by the stagnant zone and a transfer coefficient are consistent with expectations from the theory of shear dispersion another parameter which is related to the streamwise width of the initial pulse determines whether a separate pulse appears in the tracer response curves a procedure for determining the parameters from temporal moments of measured concentration curves is described and applied to measurements in the advective zone of a mountain stream predictions from the model of reichert and wanner fit the measurements especially the peak concentration better

new insights on subsurface energy resources in the southern north sea barrin area the southern north sea basin area stretching from the uk to the netherlands has a rich hydrocarbon exploration and production history the past present and expected future hydrocarbon and geothermal exploration trends in this area are discussed for eight key lithostratigraphic intervals ranging from the lower carboniferous to cenozoic in the period between 2007 and 2017 a total of 95 new hydrocarbon fields were discovered particularly in upper carboniferous rotliegend and triassic reservoirs nineteen geothermal systems were discovered in the netherlands onshore mainly targeting aquifers in the rotliegend and upper jurassic lower cretaceous formations although the southern north sea basin area is mature in terms of hydrocarbon exploration it is shown that with existing and new geological insights additional energy resources are still being proven in new plays such as the basal upper rotliegend ruby discovery for natural gas and a new chalk play for oil it is predicted that hydrocarbon exploration in the southern north sea basin area will probably experience a slight growth in the coming decade before slowing down as the energy transition further matures geothermal exploration is expected to continue growing in the netherlands onshore as well as gain more momentum in the uk

depositional systems composition and geochemistry of triassic rifted continental margin redbeds of the internal rif chain morocco the middle to upper triassic redbeds at the base of the ghomaride and internal dorsale calcaire nappes in the rifian sector of the maghrebian chain have been studied for their sedimentological petrographic mineralogical and chemical features redbeds lie unconformably on a variscan low grade metamorphic basement in a 300 m thick upward fining and thinning megasequence successions are composed of predominantly fluvial red sandstones with many intercalations of quartzose conglomerates in the lower part that pass upwards into fine grained micaceous siltstones and massive mudstones with some carbonate and evaporite beds this suite of sediments suggests that palaeoenvironments evolved from mostly arenaceous alluvial systems middle triassic to muddy flood and coastal plain deposits the successions are characterized by local carbonate and evaporite episodes in the late triassic the growth of carbonate platforms is related to the increasing subsidence norian rhaetian during the break up of pangea and the earliest stages of the western tethys opening carbonate platforms became widespread in the sinemurian sandstones are quartzose to quartzolithic in composition testifying a recycled orogenic provenance from low grade palaeozoic metasedimentary rocks palaeoweathering indices chemical index of alteration chemical index of weathering and plagioclase index of alteration suggest both a k enrichment during the burial history and a source area that experienced intense weathering and recycling processes these processes were favoured by seasonal climatic alternations characterized by hot episodically humid conditions with a prolonged dry season these climatic alternations produced illitization of silicate minerals iron oxidation and quartz rich red sediments in alluvial systems the estimated burial temperature for the continental redbeds is in the range of 100 to 160 c with lithostatic tectonic loading of ca 4 to 6 km these redbeds can be considered as regional petrofacies that mark the onset of the continental rift valley stage in the western pangea middle triassic before the opening of the western part of tethys in the middle jurassic the studied redbeds and the coeval redbeds of many alpine successions betic tellian and apenninic orogens show a quite similar history they identify a mesomediterranean continental block originating from the break up of pangea which then played an important role in the post triassic evolution of the western mediterranean region

early permian rotliegendes palaeowinds of the north sea abstract the classical desert sediments of the early permian upper rotliegendes were deposited in a post variscan basin that extends from eastern england to the russo polish border which has been referred to as the southern permian basin these sediments comprise four main depositional facies fluvial wadi aeolian sabkha and lacustrine the lacustrine facies includes important bedded halites the southern permian basin is separated from the smaller northern permian basin by the fragmented mid north sea ringkobing fyn system of highs and beyond the grampian spur lies the even smaller moray firth basin these latter basins contain rock sequences similar to those of the southern basin with the exception that bedded halite has not been recognised in the lacustrine facies the rotliegendes of the southern basin apparently conforms to deposition in a northern hemisphere tradewind desert similar to the modern southern sahara apart from regional palaeomagnetic considerations and the occurrence of sediments of a non arid nature south of the variscan highlands the strongest evidence supporting this interpretation is the pattern of palaeowind directions deduced from the orientations of dune bedding this is seen in both outcrop and core and derived from the continuous dip meter logs of many north sea wells by plotting the poles to the bedding attitudes on polar nets palaeowind directions have also been deduced from the dip meter logs of wells drilled in the northern and moray firth basins in general they indicate winds that blew in a direction opposed to those of the southern basin thus an area of high barometric pressure seems to have been located over the mid north sea high when the bedding attitudes in a well are roughly unidirectional an origin on a transverse dune is normally indicated with some wells the indicated palaeowind direction is regionally anomalous in many cases this can be rectified if the well is presumed to have drilled down through one flank of a seif dune the indicated palaeowind is thus changed by up to 90 and then commonly fits the regional pattern these early permian desert basins were smaller and closer to the equator than the modern sahara their location in the centre of a continent between the caledonian and variscan mountain ranges suggests the analogy of a more tropical equivalent of the central asian takla makan desert

mercia mudstone formation caprock to carbon capture and storage sites petrology and petrophysical characteristics porous rocks in the subsurface are now used for carbon capture and storage ccs to help ameliorate the effects of greenhouse gas emissions these porous reservoir rocks require a caprock to retain the co 2 it is important to characterize caprock quality and its stability in the presence of elevated partial pressures of co 2 lower triassic sandstones are common in the uk and nw europe and are being considered for future ccs projects the caprock to these sandstones is the middle and upper triassic mercia mudstone group we have studied the mercia mudstone using mineralogy petrology and mercury injection porosimetry to assess its caprock quality detrital minerals are dominated by quartz k feldspar illite and chlorite diagenetic pore filling minerals are dominated by calcite dolomite and gypsum in samples with abundant clay minerals there are only small quantities of pore filling diagenetic cements porosity is broadly uniform for both clay rich and clay poor samples the cleaner clay poor samples had their initial pore spaces filled with early diagenetic pore filling carbonates and gypsum despite the broadly uniform porosity mean pore throat diameter displays a strong inverse correlation with clay content whereas threshold capillary entry pressure shows a strong positive correlation with clay content the more clay rich samples represent much better caprock than the coarser grained samples that contain abundant pore filling cement the samples could support potential column heights of supercritical co 2 between 70 and 540 m and have calculated permeabilities between 10 20 and 10 19 m 2 leakage would occur only on geological time scales assuming that these samples are representative of the whole caprock because caprock quality correlates with illite content and illite will be relatively immune to elevated partial pressures of co 2 the mercia mudstone probably represents a durable caprock for future lower triassic sandstone ccs projects

the role of detrital anhydrite in diagenesis of aeolian sandstones upper rotliegend the netherlands implications for reservoir quality prediction the rotliegend upper permian reservoir interval in the southern permian basin spb contains low permeability streaks corresponding to anhydrite cemented intervals an integrated study was conducted using core cuttings thin sections and well log data from a gas exploration well and two geothermal wells that target the zone of interest this study aims at understanding the origin and nature of these low permeability streaks as well as their impact on reservoir properties and to establish a predictive model of their spatial distribution high resolution xrf core scanning analysis allowed to extrapolate spot observations in thin sections to the entire core diagenetic history includes grain rearrangement and anhydrite haematitic clay coatings dolomite rims quartz overgrowths kaolinite and second generation carbonates as cementing phases coupling of all data reveals the detrital origin of the anhydrite gypsum grains which were deposited together with the coarse grained sand fraction in an aeolian sandflat environment such partially or completely dissolved grains acted as local sources of anhydrite cement and as nuclei for precipitation explaining its preferential occurrence in coarsegrained laminae thick gypscretes in the vicinity likely supplied the anhydrite gypsum grains a conceptual model is proposed including the location of nearby gypscretes and the prevailing west southwest aeolian transport direction on the southern rim of the spb

petrographic classification of sand and sandstone abstract petrographic classifications of sand and sandstone proposed more than half a century ago are still in use although they were formulated at a time when depositional and post depositional sedimentary processes were poorly understood and before the relationships between tectonics and sedimentation could be interpreted in modern plate tectonic terms as a consequence too many scientific articles and technical reports are still encumbered with obsolete concepts graphical tools and ambiguous terminology that make sediment descriptions awkward and misleading a renovation that treasures the legacy of the pioneers is required the descriptive petrographic classification of sand and sandstone proposed in this paper is based on the quasi universally used gazzi dickinson point counting method and simply translates into words ternary compositions of quartz feldspar and lithic fragments without introducing any new names the classic qfl plot is subdivided into 15 fields labelled by adjectives introduced long ago by k a w crook and endorsed by w r dickinson and more recently by g j weltje which reflect relative abundances of the three main framework components provided they exceed 10 qfl according to standard use the less abundant component goes first the more abundant last e g litho feldspatho quartzose composition translates into q f l 10 qfl for lithic rich sand and sandstone information on the prevailing rock fragment type can be added by an additional free adjective e g metamorphiclastic carbonaticlastic as proposed long ago by r v ingersoll for lithic poor feldspatho quartzose and quartzose sand and sandstone further formal subdivisions are proposed based on the q f ratio thus reaching a total of 18 compositional fields overall modern sand known to be derived from different source rocks and found in major world s rivers deserts and deep sea fans fits in the pigeonholes defined by the relative abundance of quartz feldspar and lithic fragments the aim of this classification is to restore directness in sandstone petrology and to avoid ambiguities generated in the past by making reference to badly defined archetypes such as greywacke or arkose thus confusing petrographic composition with subjective considerations about plate tectonic setting texture hydraulic behaviour mechanical durability or chemical durability in the illusion that a classification could be genetic at the same time as descriptive

flow near sloped bank in curved channel shear and velocity distributions near a sloped bank in a 270 open channel bend are studied data which include detailed velocity and turbulence measurements in both the longitudinal and transverse flow directions are collected with a laser doppler anemometer system the flow adjacent to a 2 1 horizontal vertical and a 3 1 sloped bank is examined the purpose is to examine in unprecedented detail the developing flow near a sloped bank in a curved channel including the effect of varying side slope it is found that the longitudinal flow redistribution is fully developed at the downstream end of this 270 bend although the spiral flow is found to develop much more quickly in the straight reach upstream of the bend it is found that the friction factor on the sloped bank is more dependent on channel shape than a local velocity shear stress relationship within the bend velocities and shear stresses on the sloped bank increase significantly with the shear stress correlating more directly with the loc

calibration of a two dimensional finite element flood flow model using satellite radar imagery the application of numerical models of free surface flow to fluvial flood prediction is currently hampered by the lack of distributed calibration and validation data we address this shortcoming by the use of satellite borne synthetic aperture radar imagery to map a flood on a 15 km reach of the river thames england a finite element numerical model of shallow water flow is constructed over the reach and analysis shows that floodplain friction is the dominant factor affecting inundation extent when compared to channel friction turbulence parameterization and downstream boundary conditions the area of the domain correctly classified by the model is maximized with the constraint of uniform floodplain friction 77 at maximum compared with 70 for a simple planar model of the water free surface a simple distributed calibration scheme is also tested with a minor improvement over the uniform parameterization

diagenetic and porosity evolution of conglomerate sandstones in bayingebi formation of the lower cretaceous chagan sag china mongolia frontier area abstract the fan delta conglomerate sandstones of bayingebi formation including conglomerates and pebbly sandstones in the chagan sag are reservoir for large accumulations of hydrocarbons based on observation of cores thin sections sem and cl combined with application of fluid inclusion and carbon and oxygen isotopes it indicates that the conglomerate sandstones are mainly feldspathic litharenites with immature texture it has considerable heterogeneity with a wide range of porosity from 0 3 to 15 3 and the permeability from 0 004 md to 1168 md this study discusses conglomerate sandstones diagenesis and its controls on reservoir quality its eodiagenesis is primary compaction and the minor of calcite cementation the subsequent mesodiagenesis includes weak compaction precipitation of quartz overgrowth and feldspar overgrowth albitization dissolution of early carbonate cement and metastable framework grains late carbonate cementation and illitization a comparison between porosity depth data and normal compaction curve of conglomerate sandstones shows two groups group a is mainly composed of tight conglomerate sandstones with permeability less than 1 md and porosity less than 10 petrology studies show that two types of the tight conglomerate sandstones developed in this group one type mainly depositing in the thinly bedded subaqueous channels of fan delta front is characterized by abundant clay minerals occluding intergranular pores the other type mainly depositing in the thinly bedded subaqueous channels or along sandstone mudstone interface of thickly bedded subaqueous channels is characterized by abundant carbonate cements occluding intergranular and intragranular pores group b is mainly composed of conglomerate sandstones with higher permeability more than 1 md and porosity ranging from 5 to 16 corresponding to the burial depth from 2200 to 3400 m it mainly deposited within the thickly bedded subaqueous channels of fan delta front significant dissolution of carbonate cement feldspars and other metastable framework grains by organic acids and co 2 generated from organic maturation are the major cause of abnormally high porosity

detrital modes in a late miocene wedge top basin northeastern calabria italy compositional record of wedge top partitioning abstract the composition and stratigraphic relations of sandstones and associated conglomerates derived from erosion of the northern calabrian terranes provide important constraints for paleotectonic and paleogeographic models of the neogene wedge top depozone evolution of the southern italy foreland basin system after onset of continental collision in the southern italy orogenic belt during late oligocene to early miocene the calabrian arc drifted northeastward accreting over the adria lithosphere during mid to late miocene time since the tortonian the northern calabrian terranes represented an uplifted thrust belt in which along its leading edge tectonic subsidence was responsible for accumulation of a thick tortonian to quaternary succession dominantly siliciclastic up to 3300 meters thick deposited in the wedge top depozones rossano and crotone basins sandstone assemblages have a homogeneous quartzofeldspathic composition in the rossano and crotone basins characterized by a compositional trend through time in response to regional tectonics evolution of the basins fill occurred during 1 serravallian tortonian 2 late tortonian to early messinian and 3 late messinian detritus shed into those basins was derived mainly from terranes within the strongly deformed sila mountains allochthon which was one of the principal structural elements of the nearby northern calabrian terranes consisting of hercynian plutons intruding paleozoic cambrian to carboniferous metasedimentary host rocks and locally having a sedimentary cover of mesozoic longobucco group or early miocene paludi unit clastics low to medium grade metamorphic and minor plutonic grain types metamorphiclastic petrofacies represent the main detritus in the earliest serravallian tortonian sedimentation that accompanied progressive flexural bending of the western margin of the foreland basin system tortonian to early messinian time was characterized by isolation of the mediterranean region from the global marine realm leading to evaporite sedimentation in the foreland in addition to intense regional and local tectonics compositional response to those events was a marked increase in sedimentary detritus sedimenticlastic petrofacies related to cannibalization of early messinian evaporite successions after the evaporitic events within the basins and the gradual re establishment to the normal marine conditions sandstone detrital modes are characterized mainly by a return of the serravallian tortonian compositional modes i e metamorphic plutoniclastic petrofacies the post evaporitic sedimentation corresponds to a major tectonic rearrangement on both rossano and crotone basins related to extrusion and inversion of the basal portion of the serravallian tortonian sequences in the intermediate zone to form an intervening ciro structural high in the crotone basin during late messinian deposition of the carvane conglomerate records an abrupt sudden arrival of distinctive sedimentary containing clasts of detritus of reddish limestone marl quartz arenite siltstone and chert derived from mesozoic to tertiary basinal sequences of the southern apennines domains i e sicilide complex terranes detrital mode evolution of the inner portions of the late miocene southern italy foreland basin system was in response to abrupt tectonic partitioning due to continuation of accretionary processes rapid uplift of mid crustal blocks and the superposition of wrench tectonics

diagenetic patterns in eolian coastal sabkha reservoirs of the solimoes basin northern brazil abstract the jurua formation carboniferous solimoes basin is the largest gas reservoir in brazil a petrologic study of the jurua sandstones from the urucu area revealed the diagenetic evolution and controls on the quality of the main reservoirs as well as the relationships among diagenetic patterns depositional facies and stratigraphic unit boundaries the sandstones mudrocks evaporites and dolostones were deposited within a coastal sabkha environment with pervasive eolian reworking under increasing marine influence and a hot and dry climate eolian dune and sandsheet sandstones are the best reservoirs four stacked drying wetting upward cycles were identified with sabkha facies at the base overlain by eolian sandsheet and dune deposits which in turn are overlain again by sabkha deposits commonly eroded by the next cycle the sandstones are mostly subarkoses and arkoses blocky dolomite is the most abundant diagenetic constituent in the non eolian sandstones its distribution shows no relationship with depositional cycle limits microcrystalline pore filling and pore lining dolomite is more abundant in the eolian sandstones stable o and c dolomite isotope values presented by these dolomite cements indicate initial precipitation from a dominantly marine fluid at low temperatures 18ovpdb values mostly between 1 and 5 13cvpdb values from 3 to 2 with increasing contribution of organic matter decarboxylation at higher temperatures during burial 18ovpdb values between 12 and 6 13cvpdb from 3 5 to 8 9 chemical compaction through intergranular and stylolitic pressure dissolution and cementation by quartz overgrowths are more intense in the non eolian sandstones poikilotopic patchy post compactional anhydrite cementation is more abundant in the eolian sandstones but pervasive only close to the contacts with interbedded sabkha evaporites abundant anhydrite and quartz cementation along the base of depositional cycles contributed to the strong compartmentalization among the reservoir sub units but not to introduce internal heterogeneity to the reservoirs conversely dolomite cementation substantially affected the internal porosity and permeability heterogeneity by generating laterally extensive barriers to fluid flow

wavelet transform based seismic facies classification and modelling application to a geothermal target horizon in the ne german basin at the geothermal test site near gros sch onebeck ne german basin a new 3d seismic reflection survey was conducted to study geothermal target layers at around 4 km depth and 150 c we present a workflow for seismic facies classification and modelling which is applied to a prospective sandstone horizon within the rotliegend formation signal attributes are calculated along the horizon using the continuous morlet wavelet transform we use a short mother wavelet to allow for the temporal resolution of the relatively short reflection signals to be analysed time frequency domain data patterns form the input of a neural network clustering using self organizing maps neural model patterns are adopted during iterative learning to simulate the information inherent in the input data after training we determine a gradient function across the self organizing maps and apply an image processing technique called watershed segmentation the result is a pattern clustering based on similarities in wavelet transform characteristics three different types of wavelet transform patterns were found for the sandstone horizon we apply seismic waveform modelling to improve the understanding of the classification results the modelling tests indicate that thickness variations have a much stronger influence on the wavelet transform response of the sandstone horizon compared with reasonable variations of seismic attenuation in our interpretation the assumed thickness variations could be a result of variable paleo topography during deposition of predominantly fluvial sediments a distinct seismic facies distribution is interpreted as a system of thicker paleo channels deposited within a deepened landscape the results provide constraints for the ongoing development of the geothermal test site

groundwater ferricretes from the silurian of ireland and permian of the spanish pyrenees abstract haematite nodule horizons occur in alluvial lacustrine deposits from the mill cove formation silurian of dingle ireland and the unidad roja superior permian of the spanish pyrenees these horizons generally less than 1 m thick are not associated with palaeosol profiles but are hosted by laminated or structureless bioturbated mudstones to sandstones the sequences contain weakly developed calcrete profiles the haematite nodules are interpreted as having formed around fluctuating water tables and are analogous to present day groundwater ferricretes laterites or plinthites fe2 mobilised during periods of reducing groundwaters was segregated into ferric oxide nodules during falls in the water table or during influxes of oxygenated meteoric waters the prevailing climate during deposition of both sequences was probably semi arid and the presence of ferricrete like horizons is not evidence of humid climates the horizons represent early diagenetic effects not related to prevailing soil moisture regime

diagenesis of shallowly buried cratonic sandstones southwest sinai egypt abstract in spite of their age quartzose and feldspathic lower carboniferous sandstones deposited on the arabian shield in western sinai remain friable and porous average of 19 maximum of 25 except for strongly cemented ferricretes and silcretes these fluvial and shallow marine sandstones were not buried more than 1 5 km until late cretaceous and younger time when the deepest rocks reached 2 5 km owing to shallow burial depths and episodic exposure meteoric water dominated the pore system for most of geologic time iron oxides had multiple diagenetic stages and yield carboniferous and late cretaceous paleomagnetic signatures and oxygen isotopic data for authigenic quartz sparry calcite and kaolinite yield meteoric signatures the most significant diagenetic changes were 1 cementation by iron oxide that locally reaches 40 in groundwater ferricretes 2 reduction in porosity to 19 from an assumed original porosity 45 19 porosity was lost by compaction and 7 by cementation 3 generation of diagenetic quartzarenites by the loss of 7 detrital feldspar by kaolinization and dissolution and 4 development of three thin mature silcretes apparently by thermal groundwaters some outcrop samples have halite and gypsum cements of young but uncertain origin recycled from topographically higher younger rocks or from aerosols mature silcretes are strongly cemented by microcrystalline quartz multiply zoned syntaxial quartz and originally minor opal quartz overgrowths in most sandstones average only 2 2 but display a variety of textures and in places overprint isopachous opal now dissolved grain coats these features have more in common with incipient silcrete cement than normal burial quartz cement most silica was imported in groundwater

late permian non marine marine transitional profiles in the central southern permian basin northern germany the transition from rotliegend to zechstein within the southern permian basin is one from continental desert to a marine environment during the upper rotliegend ii a huge playa lake existed there this lake was temporarily influenced by precursors of the zechstein transgression therefore the mega playa evolved into a sabkha system one of these early marine ingressions is known from an outcrop in schleswig holstein laminated silt and claystones deposited within a standing water body are intercalated in siltstones of a salt flat environment the lake sediments are characterised by high frequency cyclicity shown by the sedimentary record and also by palaeontological data the section contains fresh water as well as brackish marine and marine fauna climatically forced cycles interact with marine incursions after the zechstein transgression had flooded the basin completely sedimentation was controlled by sea level fluctuations two sections in the southern north sea and in schleswig holstein are presented in this paper cyclicities with different frequencies controlled the sedimentation of the kupferschiefer t1 and the werra carbonate ca1 sediments of the north sea sequence were deposited within a shallow bay at the margin of an elevation therefore the high frequency cyclicity became obvious within the sedimentary patterns and in the faunal content

braided rivers within an arid alluvial plain example from the lower triassic western german basin recognition criteria and expression of stratigraphic cycles based on a detailed sedimentological analysis of lower triassic continental deposits in the western germanic sag basin i e the eastern part of the present day paris basin the conglomerat basal gres vosgien and conglomerat principal formations three main depositional environments were identified i braided rivers in an arid alluvial plain with some preserved aeolian dunes and very few floodplain deposits ii marginal erg i e braided rivers aeolian dunes and aeolian sand sheets and iii playa lake an ephemeral lake environment with fluvial and aeolian sediments most of the time aeolian deposits in arid environments that are dominated by fluvial systems are poorly preserved and particular attention should be paid to any sedimentological marker of aridity such as wind worn pebbles ventifacts sand drift surfaces and aeolian sand sheets in such arid continental environments stratigraphic surfaces of allocyclic origin correspond to bounding surfaces of regional extension elementary stratigraphic cycles i e the genetic units have been identified for the three main continental environments the fluvial type fluvial aeolian type and fluvial playa lake type at the time scale of tens to hundreds of thousands of years these high frequency cycles of climatic origin are controlled either by the groundwater level in the basin or by the fluvial siliciclastic sediment input supplied from the highland lower triassic deposits from the germanic basin are preserved mostly in endoreic basins the central part of the basin is arid but the rivers are supplied with water by precipitation falling on the remnants of the hercynian variscan appalachian mountains consequently a detailed study of alluvial plain facies provides indications of local climatic conditions in the place of deposition whereas fluvial systems only reflect climatic conditions of the upstream erosional catchments

the avaatech xrf core scanner technical description and applications to ne atlantic sediments abstract x ray fluorescence xrf core scanning provides rapid high resolution down to 1 mm records of chemical composition on split sediment cores the measurements are non destructive and require very limited sample preparation the new avaatech xrf core scanner operational since 2002 covers the atomic mass range from al to u instrument parameters especially tube voltage can be adjusted to provide optimum settings for selected elements or sets thereof owing to the nature of the surface of split sediment cores particularly effects resulting from sample inhomogeneity and surface roughness results are semiquantitative yet provide reliable records of the relative variability in elemental composition downcore selected case studies from diverse sedimentary settings in the ne atlantic ocean illustrate a range of applications of xrf logging data these include preliminary stratigraphic interpretations glacial interglacial cycles provenance studies of the terrigenous sediment fraction lithological characterization early diagenetic processes and distinction between carbonate phases aragonite v calcite

the diagenetic destruction of porosity in plutoniclastic petrofacies the miocene diligencia and eocene maniobra formations orocopia mountains southern california usa

marine ingressions into the middle late permian saline lake of the southern permian basin rotliegend northern germany possibly linked to sea level highstands in the arctic rift system abstract a huge saline lake existed in the southern permian basin spb of northwest europe during late wordian to early wuchiapingian more than 2500 m thick continental siliciclastics and evaporites of the upper rotliegend ii were deposited before the marine zechstein transgression flooded the basin marine deposition took place in the arctic rift system between east greenland and the fennoscandian shield at that time interval sediments of the foldvik creek group reflect relative sea level fluctuations short termed pre zechstein ingressions from the boreal realm into the spb are known by the marine lamellibranch liebea reichei however sedimentological analysis of different saline lake horizons show that the marine influenced saline lake horizon does not differ lithologically from other saline lake claystone layers in the rotliegend succession the 87 sr 86 sr ratios of anhydrite 0 7089 0 7100 reflect deposition in a continental setting in contrast to this s isotopic values more than 11 7 cdt reflect marine pre zechstein ingressions into the spb in the middle niendorf and munster members s isotopic values of anhydrite can be used as an indicator for marine influence in the spb the pre zechstein ingressions superimpose the climatic triggered lake level fluctuations of the rotliegend saline lake two marine ingressions can be integrated into a set of regularly recurring abnormities in the depositional evolution these important evolutionary steps the saline lake formation the garlstorf ingression the p ameland and bahnsen lake level highstands the niendorf ingression and the zechstein transgression show a periodicity of more or less 1 ma one million year cyclicity is also known from deposits of the arctic rift system in east greenland wegener halvo and ravnefjeld formations a correlation of the upper rotliegend ii deposits with the succession of east greenland is proposed based on the assumption that the marine ingressions as well as the exceptionally intensive saline lake expansions could be linked to sea level highstands in the arctic rift system the result is the first correlation of upper rotliegend ii deposits with marine strata

influence of the water content on x ray fluorescence core scanning measurements in soft marine sediments the x ray fluorescence xrf core scanner provides bulk sediment chemistry data measured nondestructively at the split core sediment surface although this method is widely accepted there is little known about the effects of physical properties such as density and water content on xrf core scanner data comparison of xrf scanner measurements from the sediment surface and dry powder samples of sediment core geob7920 indicates strongly reduced element intensities for the lighter elements al and si we relate the lower element intensities of the measurements taken at the sediment surface to the amount of water in the sample volume analyzed by the xrf core scanner the heavier elements k ca ti and fe remain relatively unaffected by the variation of any physical property within sediment core geob7920 additionally we successfully use the elemental intensity of cl as a proxy for the seawater content in the sample volume analyzed by the xrf core scanner this enables the establishment of a correction function for the elements al and si that corrects for the radiation absorption of the water content in sediment core geob7920 off cape blanc nw africa

calibration of xrf core scanners for quantitative geochemical logging of sediment cores theory and application abstract on line analysis of split sediment cores by xrf core scanners has become increasingly popular in the past decade because it allows nondestructive extraction of near continuous records of element intensities from sediment cores with a minimum of analytical effort a disadvantage of xrf core scanning relative to conventional geochemical analysis is the problematic conversion of core scanner output to element concentrations the main reason for this long standing problem is the poorly constrained measurement geometry attributable to inhomogeneity of the specimens e g variable water content and grain size distribution irregularities of the split core surface and in some setups spatial variations in thickness of an adhesive pore water film which forms directly below a protective foil covering the core surface we propose a log ratio calibration model for xrf core scanners derived from a combination of xrf spectrometry theory principles of compositional data analysis and empirical evidence the log ratio calibration model provides accurate and precise predictions of sediment composition element concentrations from xrf core scanner output with a limited number of parameters namely 2 d 1 where d equals the number of chemical elements whose concentrations are to be estimated the model can accommodate the inherent non linearity of the relation between relative intensities and concentrations which is apparent from the fact that it provides unbiased estimates an immediate corollary of our results is that log ratios of element intensities which are related to log ratios of element abundances by a simple linear transformation provide the most easily interpretable signals of relative changes in chemical composition consistent use of log ratios of element intensities or concentrations should minimise the risk of drawing erroneous conclusions from geochemical proxies the relative standard deviation precision of predicted element concentrations in core geob7920 is less than 2 stochastic simulations indicate that this level of precision can be attained with 40 randomly selected calibration specimens improved control over input errors and development of robust goodness of fit statistics allows xrf core scanning to be developed into a rigorous quantitative measurement technology the log ratio calibration equation derived in this study may be adapted to inter laboratory and inter instrument calibration as well

long range high resolution stratigraphic correlation of rotliegend fluvial fan deposits in the central dutch offshore abstract the rotliegend feather edge area in the central part of the endorheic southern permian basin in the dutch offshore is characterized by a predominance of mud prone evaporite bearing playa and lake deposits with a subordinate amount of interbedded thin fluvial sheet sandstones the distribution and lateral facies changes of the sandstone bodies have been analyzed by generating a long range high resolution chronostratigraphic correlation framework the correlation technique of pattern matching of gr logs was applied supported by calculating spectral trend curves flooding events are the primary near synchronous correlation surfaces which can be traced up to and over 100 km the basin setting of the southern permian basin the studied sandstone depositional architecture logs and sedimentary characteristics core are analogous to the depositional setting of laterally amalgamated terminal lobes of dryland river systems in an endorheic basin such as the holocene altiplano basin in bolivia present day lake eyre australia and the miocene ebro basin spain the integrated approach has yielded a stratigraphic reservoir architecture framework in which the reservoir sandstones with net sand up to 10 m have been identified as amalgamated terminal splay sandstone sheets formed at the end of dryland river pathways alternating with lacustrine mudstone layers deposited during short duration high magnitude flooding in intermittent wet climate periods

measuring sandstone compaction from modal analyses of thin sections how to do it and what the results mean abstract calculation of compactional porosity loss from modal analyses of thin sections is a useful technique for characterizing the diagenesis and porosity evolution of sandstone reservoirs to obtain meaningful results however it is essential to assume an appropriate value for the original porosity and to use point counting categories that clearly distinguish between grains and intergranular materials because of the latter requirement it is commonly not appropriate to make calculations of compactional porosity loss from modal analyses that were not performed for the specific objective of measuring intergranular volume suites of modal analyses from deeply buried sandstone units typically show wide variations in the relative importance of compaction versus quartz cementation this heter geneity must reflect subtle variations in depositional sand characteristics in particular the distribution of detrital intergranular clays that tend to promote both mechanical grain rearrangement and stylolitic grain dissolution as well as locally inhibiting quartz cement growth despite wide variation in the mechanism of porosity loss total helium porosity tends to be relatively constant at individual well locations suggesting a close interdependence between compaction and quartz cementation with total porosity loss dependent mainly upon thermal exposure either maximum temperature or time temperature integral

predicting floodplain inundation raster based modelling versus the finite element approach we compare two approaches to modelling floodplain inundation a raster based approach which uses a relatively simple process representation with channel flows being resolved separately from the floodplain using either a kinematic or diffusive wave approximation and a finite element hydraulic model aiming to solve the full two dimensional shallow water equations a flood event on a short c 4 km reach of the upper river thames in the uk is simulated the models being validated against inundation extent as determined from satellite synthetic aperture radar sar imagery the unconstrained friction parameters are found through a calibration procedure where a measure of fit between predicted and observed shorelines is maximized the raster and finite element models offer similar levels of performance both classifying approximately 84 of the model domain correctly compared with 65 for a simple planar prediction of water surface elevation further discrimination between models is not possible given the errors in the validation data the simple raster based model is shown to have considerable advantages in terms of producing a straightforward calibration process and being robust with respect to channel specification copyright 2001 john wiley sons ltd

validation of a three dimensional numerical code in the simulation of pseudo natural meandering flows validation of a three dimensional finite volume code solving the navier stokes equations with the standard k epsilon turbulence model is conducted using a high quality and high spatial resolution data set the data set was collected from a large scale meandering channel with a self formed fixed bed and comprises detailed bed profiling and laser doppler anemometer velocity measurements comparisons of the computed primary and secondary velocities are made with those observed and it is found that the lateral momentum transfer is generally under predicted at the apices this results in the predicted position of the primary velocity maximum having a bias towards the channel center compared to the position where it has been measured using a simplified two zone roughness distribution whereby a separate roughness height was prescribed for the channel center and channel sides relative to a single distributed roughness height generally led to a slightly improved longitudinal velocity distribution the higher velocities were located nearer to the outside of the bend improving both the free surface calculation and scheme for discretization of the convection terms led to no appreciable difference in the computed velocity distributions a more detailed study involving turbulence measurements and bed form height distribution should discriminate whether using distributed roughness height is a precursor to using an anisotropic turbulence representation for the accurate prediction of three dimensional river flows

effects of bed forms and large protruding grains on near bed flow hydraulics in low relative submergence conditions in mountain rivers bedforms large relatively immobile grains and bed texture and topographic variability can significantly alter local and reach averaged flow characteristics the low relative submergence of large immobile grains causes highly three dimensional flow fields that may not be represented by traditional shear stress flow velocity and turbulence intensity equations to explore the influence of large protruding grains and bedforms on flow properties we conducted a set of experiments in which we varied the relative submergence while holding the sediment transport capacity and upstream sediment supply constant flow and bed measurements were conducted at the beginning and end of each experiment to account for the absence or presence of bedforms respectively detailed information on the flow was obtained by combining our measurements with a 3d numerical model commonly used velocity profile equations only performed well at the reach scale when shallow flow effects and the roughness length of the relatively mobile sediment were considered however at the local scale large deviations from these profiles were observed and simple methods to estimate the spatial distribution of near bed shear stresses are likely to be inaccurate zones of high turbulent kinetic energy occurred near the water surface and were largely controlled by the immobile grains and plunging flow the reach averaged shear stress did not correlate to depth or slope as commonly assumed but instead was controlled by the relative boulder submergence and degree of plunging flow for accurate flow predictions in mountain rivers the effects of bedforms and large boulders must be considered

cortex a shipboard xrf scanner for element analyses in split sediment cores abstract the cortex corescanner texel is a non destructive xrf system for the logging of split sediment cores it is a seaworthy instrument that remains active during heavy weather conditions the scanner produces reliable counts for k to sr highly correlated with concentrations measured with atomic absorption spectrometry aas the option to scan al si and elements heavier than sr is in preparation a core section of 1 m can be scanned at 2 cm intervals within an hour a maximum resolution of 1 mm can be achieved at present each region and sedimentary environment requires separate calibration in the nearby future the generator settings will be standardized which may result in the development of a standard calibration procedure because of the high resolution of its semi quantitative records the cortex is a useful tool for detailed time series analysis inter core correlation and shipboard analysis

amalgamated interdune deposits white sands new mexico abstract cores taken by mckee and moiola 1975 from white sands dune field indicate that interdune areas are underlain by 7 0 10 4 m of clastic gypsum deposits clean sand bodies as much as 4 5 m thick are separated by thin beds of silly sand mckee and moiola interpreted the sequence to be the product of climbing bed forms interdune silty sands were interpreted to be deposited upon truncated dune sands and to be soon buried by the next wave of advancing dunes if the dunes are climbing in such a manner a pinchout of interdune sediments downwind across interdune surfaces is required the thickness of the silly sands should be related to the size of the interdune area and the rate of dune migration we tested this autocyclic hypothesis by trenching the length of the interdune areas in both t e barchanoid and transverse dunes trenches revealed that interdune deposits form flat lying sheets which extend uninterrupted to positions directly beneath the windward slopes of dunes at the downwind end of each interdune area this relationship precludes the possibility that under present conditions thick dune sands are being preserved because there is little or no net accumulation of dune sand interdune deposits are being amalgamated thin lenses of dune sediment exposed on the wall of one trench show that a minimum of three interdune deposits have been fused to form the uppermost 30 cm of the interdune deposit clean sand in the cores may have accumulated during periods when sediment supply was greater than at present silly sediments accumulated during periods when as in the p esent sand supply was limited and dunes did not climb appreciably future studies of modern and ancient eolian sediments should attempt to document whether the interdune deposits represent deposition within single interdune areas or amalgamation of several discrete deposits

influence of early diagenesis on reservoir quality of rotliegende sandstones northern netherlands reservoir quality of rotliegende sandstones lower permian in the northern netherlands was significantly affected by early diagenetic processes that are related to sedimentary facies in marginal desert playa lake environments in the past burial related products and processes have received more attention than early diagenetic processes neglecting the effects that early diagenesis can have on reservoir quality and well productivity of rotliegende sandstones shallow groundwater related diagenesis is a major factor affecting rotliegende reservoir sandstones the precipitation of the main porosity occluding cements dolomite anhydrite and quartz occurred early in the diagenetic history oxygen isotopes of dolomite d18o 18 4 to 23 4 smow suggest that meteoric water has played a major role throughout the diagenetic history and that precipitation of these cements occurred at low temperatures 80 c the strontium isotopes of dolomite cements 87sr 86sr 0 70935 0 71387 and the sulfur isotopes of anhydrite cements d34s 6 7 to 9 7 cdt rule out permian or younger seawater as a source for these cements and are consistent with formation from meteoric water within a continental basin an early diagenetic origin of the cements is also suggested by the fact that the majority of sandstone samples have lost more porosity due to cementation than through compaction most samples with high 20 amounts of porosity loss via cementation were affected by early dolomite and anhydrite the relative abundance of dolomite and anhydrite cements can be correlated with depositional environments wet depositional environments e g interdune and fluvial sandstones with water tables close to the surface show the highest amount of dolomite and anhydrite cements whereas dry environments with relatively deep water tables e g dune sandstones are characterized by low amounts of cements the precipitation of early diagenetic cements has strongly influenced the present day porosity patterns with depositional environments interpreted as drier showing less cements and significantly altering the porosity patterns formed during early diagenesis knowledge of the influence of sedimentology and paleogeography on the diagenetic patterns is a key element for improved understanding and prediction of reservoir quality in the rotliegende sandstones of the northern netherlands

silicate facies iron formation and strata bound alteration tuffaceous exhalites derived by mixing evidence from mn garnet stilpnomelane rocks at redstone timmins ontario silicate facies iron formation composed of mn garnet stilpnomelane and ferrotschermakitic hornblende mark an exhalative sedimentary stratigraphic horizon located regionally at the break between two volcanic supercycles consisting of lowermost calc alkaline felsic pyroclastic rocks overlain by komatiitic ultramafic flows locally mn garnet stilpnomelane rock flanks and in places is footwall to a strata bound volcanic hosted nickel sulfide deposit at redstone timmins mn garnets have normal reverse and oscillatory zoning patterns with a coupled substitution of mn ca for fe mg stilpnomelane amphibole chlorite and biotite each have elevated mno contents but do not display any concentric zoning patterns the al ti and ti zr ratios of mn garnet stilpnomelane rock are similar to those of dacitic tuff at redstone however the former rock is enriched in fe mg and mn but depleted in na relative to the latter discordant alteration pipes and concordant strata bound altered rocks associated with massive base metal sulfide and archean lode au volcanic hosted deposits are predominated by fe mg mn al enriched alkali depleted rocks very similar to silicate facies iron formation at redstone mn garnet stilpnomelane rocks represent a mixture of pyroclastic material plus chemical sediment whereby all of the al ti zr v and p have a volcaniclastic origin and most of the fe mn mg ca co and rb are chemically precipitated whereas cr ni sr na nb ba and k have been leached from a volcanic precursor y is mobile perhaps due to a preferred partitioning into the mn garnet structure both silicate facies iron formation and semiconcordant alteration zones are enriched in elements commonly mobile in hydrothermal systems such as fe mg mn si relative to 100 percent tuff as well as immobile elements including al ti zr y nb rare earth elements relative to 100 percent exhalite the resultant group of aluminosilicate minerals within these altered rocks is a function of the bulk rock composition which in turn represents a mixture of exhaled chemical sediment and volcaniclastic debris strata bound fe mg mn al enriched tuffaceous exhalites typically occur in a mixed volcano sedimentary setting distal from a volcanic center but proximal to the hydrothermal vent often flanking or stratigraphically at or near a prospective gold or base metal ore horizon

the rotliegend sedimentation history of the southern north sea and adjacent countries in this study more than 900 well logs and 125 core descriptions from the uk the netherlands and germany are analyzed and integrated into a refined tectono stratigraphic subdivision three periods of rotliegend deposition schneverdingen slochteren and hannover correspond to distinct phases of basin extension a climatic cyclicity of drying upward sequences is superimposed upon the tectonically driven phases of sediment accumulation resulting in a fine scale cyclicity that can be correlated across a variety of facies in the southern permian basin the fluvial aeolian and sabkha and lake environments are represented by conglomerates sandstones and claystones respectively the aeolian facies identified in this study include a variety of deposits found in a modern desert environment and range from sheet sand minor dune barkhan dune transverse dune and star dune to longitudinal dune the main controlling factors that were responsible for the sedimentological differences across the basin are the evolution of the tectonic elements the increasingly arid climate and the westward prograding extension of the basin these distinctive features are retained and enhanced during post rotliegend basin evolution prevailing winds blowing from the north east explain in part the distribution of the various aeolian facies across the basin

triassic redbeds in the malaguide complex betic cordillera spain petrography geochemistry and geodynamic implications abstract sandstone petrography and mudstone mineralogy and geochemistry of triassic mudstones and sandstones from continental redbeds of the malaguide complex betic cordillera southern spain provide useful information on provenance palaeoclimate and geodynamics during the early stages of the pangea break up and on their diagenetic evolution the sandstones are quartzarenites to sub litharenites with minor lithic fragments and rare feldspars the mudstone samples show a paas like elemental distribution the samples likely record recycling processes from their metasedimentary basement rocks that significantly affected the weathering indices and monitors cumulative effects including a first cycle of weathering at the source rocks sandstone composition and chemical mineralogical features of mudstones record a provenance derived from continental block and recycled orogen that were weathered under warm and episodically wet climate source areas were located towards the east of the present day malaguide outcrops and were formed by fairly silicic rock types made up mainly of palaezoic metasedimentary rocks similar to those of the paleozoic underlying series with subordinate contributions from magmatic metamorphic sources and a rare supply from mafic metavolcanic rocks clay mineral distribution of mudstones is dominated by illite and illite smectite mixed layer that result from differences in provenance weathering and burial temperature history illite crystallinity values illitization of kaolinite occurrence of typical authigenic minerals and apatite fission track studies coupled with a subsidence analysis of the whole malaguide succession suggest burial depths of at least 4 6 km with temperatures of 140 160 c typical of the burial diagenetic stage and confirm the middle miocene exhumation of the betic internal domain tectonic stack topped by the malaguide complex

deposition and early alteration of evaporites summary the depositional settings for primary and early diagenetic evaporite deposits generally fall into three categories marginal mixed shallow subaqueous and subaerial shallow and deep subaqueous these three environmental groupings hold for both marine and nonmarine settings although the details of continental evaporites may be far more complex than in most marine fed water bodies the primary evaporite morphologies from many continental playa hypersaline marine and marine marginal depositional settings are reasonably well understood because of the numerous detailed studies of recent holocene and cenozoic deposits that serve as models for sedimentary interpretation the sedimentological features that develop in deeper water settings are inferred based on examination of unaltered cenozoic deposits each environmental setting develops characteristic depositional features and patterns and one facies grades into the next because there may be significant physiochemical changes in water composition during deposition as well as sudden change s in both water depth and basinal circulation description and interpretation of evaporative rocks should not be based on mineralogy alone but on the distinct sedimentary characteristics of each part of a deposit in cases where sediments still reflect their primary mineralogy and morphology most of the environments can now be recognized however geochemical studies are commonly required to determine the source s of the original water the determinative geochemical techniques that presently serve as a support to sedimentologic study include studies of fluid inclusions bromine content of chloride salts and the stable isotopes of strontium sulphur carbon and oxygen only after these and perhaps other chemical analyses are considered can the full depositional history of a region be reasonably unravelled

velocity redistribution in curved rectangular channels the main velocity redistribution in steady flow through curved conduits of shallow rectangular cross section is considered its mechanism is analysed using a mathematical model of steady incompressible laminar flow in coiled rectangular pipes the transverse transport of main flow momentum by the secondary circulation is shown to be the principal cause of this velocity redistribution the importance of the side wall regions even in shallow channels is assessed and the neglect of the influence of the side walls in the commonly applied simplified models of flow through shallow curved channels is shown to be strongly limiting in case of long bends with a rectangular cross section

the role of diagenesis and depositional facies on pore system evolution in a triassic outcrop analogue se spain abstract this study aims at unravelling the diagenetic history and its effect on the pore system evolution of the triassic redbeds exposed in se spain tibem 1 an outcrop analogue of the tagi trias argilo greseux inferieur reservoir berkine ghadames basin algeria similar climatic base level and tectonic conditions of aforementioned alluvial formations developed analogue fluvial facies stacking patterns furthermore interplay of similar detrital composition and depositional facies in both formations resulted in analogue early diagenetic features petrographic observations indicate lithic subarkosic floodplain facies and subarkosic braidplain facies compositions which are considered suitable frameworks for potential reservoir rocks primary porosity is mainly reduced during early diagenesis through moderate mechanical compaction and formation of k feldspar overgrowth gypsum dolomite and phyllosilicate cements early mesodiagenesis is testified by low chemical compaction and quartz cementation telodiagenetic calcite filling fractures and k feldspar dissolution determined the final configuration of analysed sandstones mercury injection capillary pressure technique reveals overbank deposits in the floodplain as the least suitable potential reservoirs because of their lowest open porosity op k k 95 md and greater thickness and lateral continuity so being considered the best potential reservoir the accurate estimation of tibem microscale attributes can provide important input for appraisal and enhanced oil recovery performance in tagi and in others reservoirs consisting on similar fluvial sandy facies

compositional and geochemical signatures for the sedimentary evolution of the middle triassic lower jurassic continental redbeds from western central mediterranean alpine chains abstract compositional and chemical analyses suggest that middle triassic lower liassic continental redbeds in the internal domains of the betic maghrebian and apenninic chains can be considered a regional lithosome marking the triassic jurassic rift valley stage of tethyan rifting which led to the pangaea breakup and subsequent development of a mosaic of plates and microplates sandstones are quartzose to quartzolithic and represent a provenance of continental block and recycled orogen made up mainly of paleozoic metasedimentary rocks similar to those underlying the redbeds mudrocks display k enrichments intense paleoweathering under a hot episodically humid climate with a prolonged dry season and sediment recycling redbeds experienced temperatures in the range of 100 160 c and lithostatic tectonic loading of more than 4 km these redbeds represent an important stratigraphic signature to reconstruct a continental block mesomediterranean microplate that separated different realms of the west

deep water clastic evaporites deposition in the messinian adriatic foredeep northern apennines italy did the mediterranean ever dry out a new genetic facies model for deep water clastic evaporites is presented based on work carried out on the messinian gessoso solfifera formation of the northern apennines during the last 15 years this model is derived from the most recent siliciclastic turbidite models and describes the downcurrent transformations of a parent flow mainly composed of gypsum clasts the model allows clearer comprehension of processes controlling the production and deposition of clastic evaporites representing the most common evaporite facies of the northern apennines and the definition of the genetic and stratigraphic relationship with primary shallow water evaporites formed and preserved in marginal settings due to the severe recrystallization processes usually affecting these deposits petrographic and geochemical analyses are needed for a more accurate interpretation of the large spectrum of recognized gravity driven deposits ranging from debrisflow to low density turbidites almost all the laminar balatino gypsum previously considered a deep water primary deposit is here reinterpreted as the fine grained product of high to low density gravity flows facies associations permit the framing of the distribution of clastic evaporites into the complex tectonically controlled depositional settings of the apennine foredeep basin the messinian salinity crisis occurred during an intense phase of geodynamic reorganization of the mediterranean area that also produced the fragmentation of the former miocene apennine foredeep basin in this area primary shallow water evaporites equivalent to the mediterranean lower evaporites apparently only formed in semi closed thrust top basins like the vena del gesso basin the subsequent uplift and subaerial exposure of such basins ended the evaporite precipitation and promoted a widespread phase of collapse leading to the resedimentation of the evaporites into deeper basins vertical facies sequences of clastic evaporites can be interpreted in terms of the complex interplay between the messinian tectonic evolution of the apennine thrust belt and related exhumation erosional processes the facies model here proposed could be helpful also for better comprehension of other different depositional and geodynamic contexts the importance of clastic evaporites deposits has been overlooked in the study of other mediterranean areas based on the apennine basins experience it is suggested here that evaporites diffused into the deeper portions of the mediterranean basin may consist mainly of deep water resedimented deposits rather than shallow water to supratidal primary evaporites indicative of a complete basin desiccation

diagenetic constraints on heterogeneous reservoir quality assessment a triassic outcrop analog of meandering fluvial reservoirs reliable modeling of meandering fluvial reservoirs is challenging because of the heterogeneity in magnitude and pattern of porosity and permeability related to depositional and diagenetic features early mechanical and chemical alterations proceed along different pathways directly related to depositionally governed differences in textural and compositional parameters in a well constrained sedimentological framework and with relatively homogeneous conditions of detrital composition this study aims to determine the effect of depositional fabric on early diagenetic processes and their collective effect on petrophysical properties pore size distribution open porosity and permeability a high resolution qualitative and quantitative petrographic analysis is conducted on 22 fine to very fine grained sandstones from the main meandering fluvial facies of the channel center and margin point bar lower middle and upper scroll bar and chute channel of a triassic outcrop analog the occurrence of small scale internal heterogeneity associated with detrital matrix and suspension settling laminae favors the compaction process and hinders early pore filling cement precipitation that helps the preservation of primary porosity multivariate statistical treatment of data demonstrates that large 1 m and well connected primary intergranular pores are the main contributors to permeability in the more heterogeneous samples the distribution of the finer grained sediment fraction is strongly facies related as a result of hydraulic sorting better understanding of linkages between depositionally predictable features and diagenetically induced heterogeneity may lead to realistic reservoir models and enhanced effectiveness of exploitation and bypassed oil recovery strategies

evolution of calcrete in palaeodrainages of the lake napperby area central australia abstract carbonate lithofacies developed along the trunk valley of palaeodrainage channels as well as those adjacent to gypsite facies in the lake napperby drainage basin in central australia show wide ranges of sedimentary characteristics reflecting significant variation in depositional environments sedimentological and geochemical characterization of the calcrete lithofacies in this drainage area indicate that whereas variations in bedrock morphology are important in overall distribution of the phreatic and vadose calcrete varieties faulting and basin adjustments since the early quaternary may also have played a significant role in redistribution of the hydrologic zones and hence the evolution of these calcretes accordingly phreatic calcretes which initially precipitated from laterally moving groundwaters along the palaeodrainage channels undergo systematic mineralogical changes due to direct evaporative precipitation and diagenetic displacement replacement processes mainly dolomitization and silicification under present hydro chemical conditions within the zone of grounwater fluctuations however lateral and downward shifts in groundwater flow due to excessive volumetric expansion and reduction in effective permeability of calcrete may ultimately result in isolation of the calcrete like those observed from the eastern margins of the lake the evolution of the vadose calcretes is thereafter topographically controlled and relates to mobilization and redistribution of earlier deposited calcretes under present meteorological conditions