site investigations to evaluate flow liquefaction slides at sand heads fraser river delta l ecoulement par liquefaction spontanee est un processus recurrent dans la progradation du delta du fleuve fraser une portion du delta a ete etudiee au moyen d essais de penetration au cone sismique et de resistivite et au moyen de l analyse spectrale de la methode des ondes de surface et de l echantiollonage de sol et de vapeur dans un effort pour determiner la stratigraphie du site l etat in situ et le degre de saturation afin explorer l enigme de l ecoulement par liquefaction spontanee un ensemble de capteur de pression interstitielle et d inclinaison a ete installe comme partie de l etude pour mesurer les effets de la vidange resultant du reflux de la maree les resultats ont indique que le lit de la mer a faible profondeur etait partiellement sature contenant un volume significatif de gaz methane qui affectait la reponse dynamique de la pression interstitielle durant le jusant une reduction de la contrainte effective atteignant 16 5 kpa a ete mesuree de meme qu un delai de 50 min entre le reflux de la maree et la reaction de la pression interstitielle ceci suggere que les effets de tampon sont un facteur significatif dans le declenchement de la liquefaction spontanee des sables l ches non viellis la ou ils reposent sur des pentes sous marines les resultats des essais in situ montrent que les sables nouvellement deposes du fleuve fraser ont une forte susceptibilite a l ecoulement par liquefaction

how porosity and permeability vary spatially with grain size sorting cement volume and mineral dissolution in fluvial triassic sandstones the value of geostatistics and local regression although it is well known that sandstone porosity and permeability are controlled by a range of parameters such as grain size and sorting amount type and location of diagenetic cements extent and type of compaction and the generation of intergranular and intragranular secondary porosity it is less constrained how these controlling parameters link up in rock volumes within and between beds and how they spatially interact to determine porosity and permeability to address these unknowns this study examined triassic fluvial sandstone outcrops from the uk using field logging probe permeametry of 200 points and sampling at 100 points on a gridded rock surface these field observations were supplemented by laser particle size analysis thin section point count analysis of primary and diagenetic mineralogy quantitative xrd mineral analysis and sem edax analysis of all 100 samples these data were analyzed using global regression variography kriging conditional simulation and geographically weighted regression to examine the spatial relationships between porosity and permeability and their potential controls the results of bivariate analysis global regression of the entire outcrop dataset indicate only a weak correlation between both permeability porosity and their diagenetic and depositional controls and provide very limited information on the role of primary textural structures such as grain size and sorting subdividing the dataset further by bedding unit revealed details of more local controls on porosity and permeability an alternative geostatistical approach combined with a local modeling technique geographically weighted regression gwr subsequently was used to examine the spatial variability of porosity and permeability and their controls the use of gwr does not require prior knowledge of divisions between bedding units but the results from gwr broadly concur with results of regression analysis by bedding unit and provide much greater clarity of how porosity and permeability and their controls vary laterally and vertically the close relationship between depositional lithofacies in each bed diagenesis permeability and porosity demonstrates that each influences the other and in turn how understanding of reservoir properties is enhanced by integration of paleoenvironmental reconstruction stratigraphy mineralogy and geostatistics

the depositional architecture and facies variability of shelf deltas in the eocene battfjellet formation nathorst land spitsbergen deltas are commonly classified according to their plan view morphology as either river dominated tide dominated or wave dominated however most deltas form under the mixed influence of these processes commonly with laterally varying process regimes it has also become clear that there is a mismatch between the plan view morphology and internal facies composition in some deltas combined outcrop and subsurface data from the eocene battfjellet formation spitsbergen provide an example of ancient shelf deltas that formed under mixed influence internally these shelf deltas are characterized by wave dominated facies that are normally associated with strike extensive nearly linear shoreline sandstones however the formation comprises partially overlapping sandstone bodies of limited lateral extent 20 km in any direction this stacking pattern is attributed to frequent autogenic lobe switching that caused localized and rapid transgressions such processes typify fluvial dominated deltas and occur less commonly in wave dominated ones thus there is an apparent mismatch between inferred plan view morphology and internal facies composition it is argued that the battfjellet deltas were flood dominated and prograded mainly during periods of high fluvial discharge however reworking of the fluvial flood facies by fair weather and storm waves as well as longshore currents resulted in a wave dominated facies character delta lobes undergoing auto retreat were particularly prone to reworking by basinal processes including tidal currents it is suggested that repeated delta progradation from inner shelf settings towards the outer shelf and shelf edge was aided by high sediment supply rather than relative falls in sea level as previously suggested this interpretation is supported by i the lack of major facies dislocations and extensive sub aerial unconformities and ii an overall relative rise in sea level as evidenced by an overall low angle 0 8 to 1 2 ascending shoreline trajectory the latter results from the combined effect of basin subsidence eustatic highstand and sediment compaction

conditions for formation of massive turbiditic sandstones by primary depositional processes it can be shown from bedform stability diagrams that each turbidity current regardless of whether its density is low or high or whether its history is simple e g surging flow or complex e g sustained flow should pass through a final waning phase in which flow conditions are prone to bedform development yet many thick deep marine sandstones of supposed turbidity current origin are totally devoid of tractional structures such as plane parallel lamination and ripple cross lamination tdure a mathematical model for the calculation of duration of sediment deposition from high density turbidity currents hdtcs is used to show that the absence of bouma tb and tc divisions cannot be explained by rapid temporal flow deceleration only the model calculations imply that discernible tractional structures are formed even at residence times within the upper stage plane bed and ripple stability regimes of several seconds and several tens of seconds respectively therefore other explanations have to be sought for the absence of lamination in turbiditic massive sandstones these include incompatible grain size post depositional removal or obstruction of lamination by bioturbation and liquefaction and erosion of laminated divisions followed by rapid burial

the bouma division a and the possible duration of turbidity currents abstract experimental data arnott and hand 1989 combined with theoretical arguments suggest that the transition in a turbidite from division a to division b occurs at a deposition rate of unsupported grains of about 6 7 10 4 m s 1 in the case of fine medium quartz sand a second rate may be calculated from properties measured at the transition from division b to division c allen 1971b these rates together permit an estimate to be made of the order of magnitude of the duration of deposition from a turbidity current the calculated order of a few tens of minutes for a mio pliocene turbidite described and interpreted hydraulically by komar 1985 is in broad agreement with his independent estimate based on the sequenc of sedimentary structures

morphometric analysis and genetic implications of pro deltaic sea floor undulations in the northern alboran sea margin western mediterranean basin abstract several fields of seafloor undulations from pro deltaic wedges in the northern margin of alboran sea western mediterranean basin are described in this paper a series of elongated subparallel bathymetric undulations are distinguished in the foreset to bottomsets regions of the holocene pro deltaic wedges related with the guadalfeo and verde seco rivers multibeam data surficial sediment samples and high resolution seismic profiles have been used in this study and integrated in a geographical information system quantitative measurement of key morphometric parameters wave length height asymmetry length and wave form index was performed on multibeam data and seismic profiles using the arcgis software wave form index and depth data were analysed statistically and a cluster analysis was carried out in each area according to these results we infer that sea floor undulations in the study areas are best explained by the influence of strong sediment flows normal to bathymetric contours probably coupled with the effect of subsequent slow sediment deformation processes such as sediment creeps the influence of bottom current activity is considered less likely as the position of river mouths and the very high slope gradients seems to be the key factors which control the development of these sea floor undulations the alboran sea sea floor undulations are compared with those of other fields in shallow water environments and the different processes of formation evaluated

contrasting styles of shelf sediment transport and deposition in a ramp margin setting related to relative sea level change and basin floor topography turonian cretaceous western interior of central utah usa abstract the turonian lower ferron sandstone and juana lopez members of the mancos shale in the western interior foreland basin form a series of regressive shoreface to shelf depositional complexes sourced from the sevier fold thrust belt to the west continuous dip parallel outcrop exposures around the northern and eastern edges of the tertiary san rafael anticline sra in central utah provide an insight into the origins of anomalous marine mudstone encased sandstones lower ferron strata consist of both coarsening and thickening upward and sharp based shoreface successions interpreted to have been deposited as sequential highstand and falling stage systems tracts overlying these shallow marine deposits is a surface that marks sediment bypass that is correlated down dip into coarse grained cross bedded sandstones interpreted as the deposits of channelised turbidity flows these turbidites are considered to be the products of sustained hyperpycnal flows exiting rejuvenated lowstand rivers based on sustained flow indicators such as dune scale cross bedding absence of genetically related slumps and delta front deposits in up dip areas surfaces of sediment bypass coarser grain sizes than the underlying shoreface deposits and regional palaeogeography the flows are interpreted to have been ignitive in proximal areas down a tectonically induced slope in the uplifted area of the farnham dome the change in depositional style from falling stage to lowstand systems tracts is attributed to increased rates of sediment supply to the shoreline promoting hyperpycnal flows a flooding surface caps the interval and separates the lower ferron sandstone from the overlying juana lopez member this interval in contrast consists only of heterolithic parallel and ripple laminated graded sandstone mudstone couplets interpreted to have been deposited by turbulent storm induced geostrophic flows the couplets are arranged into bundles and are interpreted as parasequences which in turn are arranged into a progradational parasequence set deposited during a period of sea level highstand divergent sole mark and bedform palaeocurrents from both members suggest slight eastward deflection of the turbulent flows off the proto sra further evidence for this topography is inferred from an absence of turbidites along the western side of the structure the inferred influence of local basin floor structures on sedimentation of these units has important implications for structural models for this basin for generalized sequence stratigraphic models applied to ramp type foreland basin sequences and for elucidating the origin of anomalous marine mudstone encased sandstone bodies

geometry and facies of tertiary clinothems spitsbergen sandstone clinothems from the battfjellet formation palaeogene on spitsbergen are locally exceptionally well preserved along depositional dip parallel mountainsides the clinothems are more than 1 km wide and more than 100 m thick superposition of several sandstone clinothems separated by mudstones reflects repeated shoreline progradation and transgression deposition took place partly on post transgressional depositional shelves and partly by contributing seaward sloping wedges or clinothems to a ramp progradation shorelines dominated both by mouth bar and shoreface environments have been identified the clinothems are organized into an overall progradational architecture with a geometry having features in common with progradational seismic facies

active sand transport along a fjord bottom channel bute inlet british columbia an underwater channel system is incised in the holocene fjord basin sediments of bute inlet british columbia high resolution side scan sonar swaths and seismic profiles reveal two channels within a zone of extensive rotational sliding on the slopes of a fjord head delta the channels coalesce into a single sinuous channel that extends 14 km downfjord on a 0 9 slope where it splits into two distributaries which continue another 18 km ending within stacked depositional lobes piston cores show sands in the channels and lobes in contrast to deep water silty clays in the basin floor the sea floor features and sediment distributions result from active highly mobile slide generated sediment flows which transport sands via the channels from the delta to the fjord basin

ichnofabrics and geometric configurations of ophiomorpha within a sequence stratigraphic framework an example from the upper cretaceous us western interior ichnofabric in the upper cretaceous sego sandstone and anchor mine tongue of east central utah can be differentiated into two components 1 discrete ophiomorpha and 2 mottling and other trace fossils the ichnofabric index method was employed to evaluate spatial variability of the ichnofabrics within depositional sequences and component systems tracts indices were logged for amount of bioturbation caused solely by ophiomorpha oii and that represented by all other biogenic features bii values of oii 1 are more pervasive in lowstand systems tracts compared to transgressive systems tracts this is consistent with the predominance of marginal and nearshore marine sand dominated settings that are characteristic of lowstands which are favourable habitats for colonization by ophiomorpha producers ichnofabric index values vary both vertically and laterally within any given systems tract reflecting differences in physical and biological parameters operating in the palaeoenvironment these parameters include the total number and behaviours of organisms occupying the substrate as well as substrate texture and grain size and rates of sedimentation the architectural style of ophiomorpha was examined within five depositional facies shelf storm deposit lower shoreface shoreface and estuarine inclinations of individual burrow elements were approximated relative to bedding planes categorized as either vertical inclined or horizontal and then plotted on ternary diagrams based on the types of facies present these results suggest that variations in the geometric configurations of ophiomorpha are controlled primarily by physical energy levels and the rate and nature of sedimentation results of this study have broad implications for understanding the physical factors affecting facies variability within sequences and systems tracts when coupled with sedimentologic data recognition of variations in the distribution of ichnofabrics and architectural style of ophiomorpha can provide additional information useful for characterizing depositional environments and therefore could be integrated with other basin analysis techniques to test and refine sequence stratigraphic interpretations

constraining sub seismic deep water stratal elements with electrofacies analysis a case study from the upper cretaceous of the maloy slope offshore norway abstract electrofacies represent rock facies identified from wireline log measurements and allow extrapolation of petrophysical characteristics away from stratigraphic intervals that are calibrated to core this approach has been employed to reduce uncertainty in the identification of the sub seismic depositional elements in the late cenomanian coniacian succession of the northern maloy slope offshore norway core logging permits identification of eleven distinct sedimentary facies that are grouped into four facies associations fa a turbidite sandstones fa b heterolithic siltstones and sandstones fa c debrites and fa d slide and slump deposits each facies association is defined by a distinct combination of petrophysical characteristics including porosity density gamma ray sonic and resistivity using neural network analysis electrofacies are calibrated with sedimentary facies thereby allowing us to map their thickness and stacking patterns within the studied deep water succession we demonstrate that this approach is particularly useful where the presence of glauconite makes the distinction between sandstone from shale rich units difficult using gamma ray logs alone our results indicate that the succession of interest is dominated by debris flows and slide and slump deposits which are commonly poorly imaged on seismic reflection datasets in the northern north sea the methodology presented here can aid the correlation of deep water stratal elements at production and exploration scales in stratigraphic successions that have undergone similar burial histories furthermore this method may help in the identification of mass flow deposits that are present in upper cretaceous deep water systems of the north sea

sediment slump structures a review of diagnostic criteria and application to an example from newfoundland abstract in the study of the history of deformed sedimentary rocks it is important that the cause of the deformation and the timing of deformation relative to metamorphic and tectonic events be assessed there is a continuous gradation between the deformation of freshly deposited sediments by gravitational forces and the deformation of well lithified sediments by tectonic forces so determining the degree to which gravity tectonism and lithification influenced deformation can be very difficult the characteristics that may be considered in determining the origin of deformational structures in sedimentary rocks can be divided into five categories ductile deformation structures 1 can provide definitive criteria for recognizing post lithification deformation but not pre lithification deformation this also holds for 2 brittle deformation structures and decollements overprinting of sediment reworking or remobilization structures 3 are the best criteria for recognizing pre lithification structures fabrics 4 can be very useful but are as yet poorly understood and there are misconceptions in the literature about what sort of fabrics are or are not found in unlithified sediments spatial relationships 5 may also tell us a great deal but are most useful when taken in conjunction with other types of evidence complex fold patterns in sandstones on farmer head north central newfoundland provide a case study for criteria that may be used to determine the degree of lithification during deformation although these folds have been interpreted as slump folds by earlier workers fabrics and spatial relationships point to a tectonic post lithification origin for the structures a conclusion which has significant implications for the interpretation of the regional geology

facies and architecture of an estuarine tidal bar the trompeloup bar gironde estuary sw france abstract this study describes the sedimentary facies and internal architecture of a modern estuarine tidal bar present in the bay head delta of a wave and tide dominated estuary the gironde estuary in southwest france based on 51 cores 2 to 5 m long this work demonstrates that such bars are composite sedimentary bodies made up of individual sigmoidal sand units isolated from one another by thick muddy layers the bar appeared in the study area around 1874 since then its evolution has been characterized by phases of rapid downstream bar migration alternating with periods of bar abandonment during the periods of active bar progradation which commonly last between 10 and 20 years the bar progrades up to 7 km seaward and forms a narrow 200 800 m wide sand ridge up to 6 m thick during abandonment phases which also last around 10 20 years the bar is starved of sand and a mud layer 1 to 3 m thick is deposited the vertical succession formed by the seaward progradation of the tidal bar records these alternating phases of growth and abandonment a typical vertical succession in the bar system is 8 m thick and comprises several superimposed upward coarsening units of cross stratified sand deposited during phases of seaward progradation separated by a thick layer of thinner bedded mud and sand laminae deposited during phases of bar abandonment when a tidal bar builds up to the supratidal zone marshes accumulate and the bar becomes a permanent island in the estuary the large scale architecture of the bar is thus made of an alternation of potential sandy reservoir units and muddy internal seals the reservoir units are characterized by a sigmoidal shape the muddy layer which is deposited between the two sigmoidal units is a thick continuous potential internal seal this complex internal architecture is due to the fact that there is a considerable amount of mud present in the bay head delta of the gironde estuary it is thought to be representative of the architecture of tidal bars in the inner part of wave and tide dominated estuaries

morphological changes and sedimentary processes induced by the december 2003 flood event at the present mouth of the grand rhone river southern france the study which is based on repetitive bathymetric surveys assesses changes and effects of one of the most important floods recorded in the rhone delta area bottom morphology and sediment distribution in the rhone outlet after the december 2003 flood are discussed by comparison between digital terrain maps dtms of november 2003 and january 2004 the post flood morphology shows that the whole of the system is active mainly in the east the channel of the rhone has been hollowed out on the left bank by more than 5 m the eastern coast of the mouth has retreated 400 m the mouth bar has prograded 200 m and the slope of the delta front has increased by 0 19 the overlay of pre and post flood dtms makes it possible to estimate the total volume deposited in the 0 to 20 m zone as 7 8 10 the acquisition of bathymetric measurements immediately before and after a major flood allows more than a simple morphological description in addition an analysis of the solid load transfer processes towards the prodelta is achievable three mechanisms are highlighted most of the material eroded in the channel and supplied to the delta front corresponds to fine sediment that drape homogeneously over the pre flood morphology of the delta front the transit of the coarsest sediment primarily sand is slowed down in the channel of the rhone this sediment builds up in relatively small areas leading to the formation of gullies on the prodelta slope the gullies have fixed positions and disappear gradually towards the west following the progressive migration of the active band towards the east these old features are not reactivated by floods occurring after their formation during the flood only a small volume of coarse sediment bypasses through the gullies and the fine deposits are remobilised rapidly or compacted flood input concerns essentially the delta front which traps 90 of the fluvial solid discharge between 0 and 20 m depth the coarse prodelta supply is then due mainly to mass movements of unconsolidated material deposited beforehand on the top of the delta front consequently the main nourishment of the prodelta does not occur directly during and or immediately after a flood event but is delayed by sediment being temporarily trapped on the delta front

basin floor fans in the north sea sequence stratigraphic models vs sedimentary facies discussion original article shanmugan g r b bloch s m mitchell g w j beamish r j hodgkinson j e damuth t straume s e syvertsen and k e shields 1995 aapg bulletin v 79 p 477 512

pliocene pleistocene glaciomarine sedimentation in eastern prydz bay and development of the prydz trough mouth fan odp sites 1166 and 1167 east antarctica abstract lithostratigraphy grain sizes and down hole logs of site 1166 on the continental shelf and site 1167 on the upper slope are analyzed to reconstruct glacial processes in eastern prydz bay and the development of the prydz trough mouth fan in eastern prydz bay upper pliocene lower pleistocene glaciomarine sediments occur interbedded with open marine muds and grade upward into waterlaid tills and subglacial tills lower pleistocene sediments of the trough mouth fan consist of coarse grained debrites interbedded with bottom current deposits and hemipelagic muds indicating repeated advances and retreats of the lambert glacier amery ice shelf system with respect to the shelf break systematic fluctuations in lithofacies and down hole logs characterize the upper pliocene lower pleistocene transition at sites 1166 and 1167 and indicate that an ice stream advanced and retreated within the prydz channel until the mid pleistocene the record from site 1167 shows that the grounding line of the lambert glacier did not extend to the shelf break after 0 78 ma published ice rafted debris records in the southern ocean show peak abundances in the pliocene and the early pleistocene suggesting a link between the nature of the glacial drainage system as recorded by the trough mouth fans and increased delivery of ice rafted debris to the southern ocean

gravity currents facilitate formation of high frequency internal solitons and bores at the base of the fraser delta in the southern strait of georgia

early cambrian teichichnus dominated ichnofabrics and palaeoenvironmental analysis of the caerfai group southwest wales uk abstract the early cambrian caerfai group of pembrokeshire in southwest wales yields an intensely bioturbated teichichnus dominated ichnofabric and provides evidence for the early evolution of infaunal organisms three units of the caerfai group comprise the focus of this study in sections exposed at caerfai bay in the st non s sandstone few primary sedimentary structures are observed bedding being predominantly massive with subordinate parallel and current ripple cross lamination the topmost st non s sandstone contains common soft sediment deformation phenomena and collectively deposition is believed to have taken place in the proximal subaqueous reaches of a steep fronted delta system teichichnus is the dominant trace with subordinate planolites palaeophycus and possible rhizocorallium the overlying caerfai bay shales were deposited from mass flows with evidence of downslope creep suggesting deposition on a steep delta front sandstone debrites are common as are tuffaceous beds with evidence of reworking by bottom currents sandstone and tuff event beds contain common skolithos and arenicolites with less frequent planolites interbedded mudstones contain infrequent teichichnus the caerfai bay shales coarsen and thicken upwards into the caerbwdy sandstone debrite sandstone beds dominate and bed thickening upsection indicates progradation of the delta system the dominant trace fossil within the unit is teichichnus which is constrained to the top few centimetres of individual sandstone beds less common are planolites and palaeophycus the size and abundance of teichichnus in the caerfai group are similar to or exceed those in contemporaneous sections in avalonia and baltica local environmental factors were probably the primary control on trace fossil distribution substrate and salinity are proposed as the main influences on ichnodiversity and size in the caerfai group teichichnus is most abundant in the st non s sandstone where the proximal reaches of the delta experienced reduced salinity and possibly higher oxygen levels burrow diameter progressively decreases upsection and bioturbation becomes less pervasive in subsequent units of the caerfai group this indicates that by the cambrian stage 2 significant advances into reduced salinity environments had occurred along with the dispersal of the teichichnus producer throughout the avalonia baltica seaway correlation within avalonia indicates that a transgression in the cambrian stage 2 initiated the deposition of the caerfai group marking the onset of the welsh basin

a delta plain sheet sand in the fraser river delta british columbia canada abstract borehole data in the fraser river delta demonstrate that a nearly continuous sand unit generally 8 to 20 m thick underlies the surficial silts and sands of most of the delta plain the sand unit consists of one or more sharp based fining upward sequences and is interpreted to be a complex of distributary channel deposits distributary channel migration and the resulting accumulation of channel sands has occurred primarily in a tidal flat environment due to the interaction of tidal and fluvial processes and the high proportion of sand in the sediment load this sand unit thus provides a model for sand rich river and tide dominated delta plains jetties now maintain the position of the main channel of the fraser river where it crosses the tidal flats and prevent channel migration and further storage of sand in the lower delta plain as a result more of the available sand is being transported directly to the river mouth where failures transport the sand downslope consequently these structures contribute to instability at the river mouth

basin floor fans of the central tertiary basin spitsbergen relationship of basin floor sand bodies to prograding clinoforms in a structurally active basin

the foreslope hills large scale fine grained sediment waves in the strait of georgia british columbia abstract the foreslope hills are a set of 20 m high 5 km long ridges at 230 350 m water depth in the south central strait of georgia occupying a 60 km 2 area at the base of the fraser river delta foreslope they are composed of clay silt and fine sand previous authors have interpreted them as 1 a single mass slide deposit 2 mud diapirs 3 in situ rotational failures and 4 creep deformation features but collaborative evidence for these interpretations is lacking seafloor surface morphological renders derived from recent multibeam sonar bathymetry data show linear evenly spaced symmetrical ridges with ridge bifurcation resembling wave ripples but on a much larger scale detailed multichannel and single channel seismic reflection data show sinusoidal internal reflections suggesting upslope migration the ridges occur within the uppermost portion of the holocene section in a very high sedimentation rate environment consequently they are probably less than 3000 years old moored current meter records for the region show reversing currents largely oriented normal to the ridge crests averaging 10 cm s with a maximum of 50 cm s this evidence combined with increasing documentation of large scale sedimentary bedforms in slope and rise environments suggests that the foreslope hills should be re interpreted as sediment waves upslope migration is typical of many large scale fine grained sediment waves the preferred physical interpretation for the creation and maintenance of the foreslope hills as sediment waves is the lee wave model requiring a phase shift in density stratified flow as it passes over the wavy topography maximum measured bottom currents are easily strong enough to entrain silt and clay delivered to the site by turbidity currents or by sediment plume fallout from fraser river outflow either strong flood tides or severe biannual density intrusions due to their intense stratification may be susceptible to lee wave formation and the creation of sediment waves leading to the observed pattern of upslope migration

origin and variability of sedimentary facies of the fraser river delta foreslope british columbia abstract five sedimentary facies have been recognized in piston cores from the fraser river delta foreslope 1 river plume suspension deposited massive silty clay with minor organics 2 suspension deposited silty clay to clayey silt with rare parallel silt and very fine sand laminations deposited under minor traction 3 clayey silt with silt or very fine sand interbeds from mixed suspension and low density turbidity current traction deposition 4 silty very fine to medium grained sand with less than 10 thin clay or silt interbeds predominantly deposited from high density turbidity currents and 5 organic rich disorganized chaotic beds facies distribution patterns suggest that the fraser delta foreslope is dissected by a number of both active and inactive channels these channels have served as a mechanism for coarse grained sediment to bypass the delta plain and upper foreslope and be introduced directly to the lower foreslope and basin floor it is hypothesized that these channels debouch as a series of depositional lobes and slump related failure deposits in the prodelta basinal environment the direct introduction of clastic sediment into water depths exceeding 250 m suggests a process analogue for the interpretation of shelf edge deltas in the rock record thus the fraser river delta may offer a unique opportunity to model active sedimentation associated with a lowstand of sea level

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion the pennsylvanian jackfork group in the ouachita mountains of arkansas and oklahoma has conventionally been interpreted by many workers including us as a classic flysch sequence dominated by turbidites in a submarine fan setting however normal size grading and bouma sequences indicative of turbidite deposition are essentially absent in these sandstone beds they appear massive i e structureless in outcrop but when slabbed reveal diagnostic internal features these beds exhibit sharp and irregular upper bedding contacts inverse size grading floating mudstone clasts a planar clast fabric lateral pinch out geometries moderate to high detrital matrix up to 25 sigmoidal deformation duplex structures and contorted layers all these features indicate sand mplacement by debris flows mass flows and slumps mud matrix in these sandstones was sufficient to provide cohesive strength to the flow discrete units of current ripples and horizontal laminae have been interpreted to represent traction processes associated with bottom current reworking the dominance of sandy debris flow and slump deposits nearly 70 at degray spillway section and bottom current reworked deposits 40 at kiamichi mountain section and the lack of turbidites in the jackfork group have led us to propose a slope setting our rejection of a submarine fan setting has important implications for predicting sand body geometry and continuity because deposits of fluidal turbidity currents in fans are laterally more continuous than those of plastic debris flows and slumps on slopes a turbidite dominated fan model would predict an outer fan environment with laterally continuous sheetlike sandstones for the jackfork group in southern oklahoma and western arkansas whereas a debris flow slump model would predict predominantly a slope environment with disconne ted sandstone bodies for the same area

the use of a morphological acceleration factor in the simulation of large scale fluvial morphodynamics abstract numerical simulation of fluvial morphodynamic processes can identify important dynamics at time and space scales difficult to observe in the field however simulations involving large spatial scales and or the long timescales characteristic of morphodynamic processes are often untenable because of long computation times the morphological acceleration factor morfac applies a scalar multiplier to the sediment continuity equation and is often applied in morphodynamic simulations to reduce computational time although the use of morfac in coastal simulations is relatively common its applicability in field scale fluvial models is generally confined to steady flow simulations over reach scale spatial domains here we explore the viability of using morfac to simulate large scale long term morphodynamics in a gravel bed river we use delft3d to simulate a 60 d period with a significant discharge event in the nooksack river washington we systematically adjust morfac values ranging from 5 to 50 to compare with a baseline condition of no acceleration model results suggest that morfac based modification of the inflow hydrograph time series reduces peak flow magnitudes and flood wave celerities higher morfac values result in greater flood wave attenuation and lower celerity reducing the simulated morphological impact at locations farther downstream in general relative error compared to the model baseline increases farther downstream because of the altered flood wave propagation however error analysis also shows a positive relationship with channel slope and a negative relationship with channel width hence errors increase in the steeper confined reaches of the upper part of the domain even for the lowest morfac values absolute cumulative volume change errors are on the order of 10 indicating that the use of morfac in fluvial simulations is best restricted to short term and or smaller scale modeling efforts wider channel sections with lower gradients are shown to produce lower morfac related errors therefore morphological acceleration as examined here is potentially more appropriate for limited reaches rather than large scale domains

practical problems in the application of the sequence stratigraphic method and key surfaces integrating observations from ancient fluvial deltaic wedges with quaternary and modelling studies sequence stratigraphy solved the basic problem that genetically related but different lithofacies were routinely assigned to different lithostratigraphic units defined by arbitrary vertical and horizontal cutoffs stratigraphically important stratal relationships and especially stratal terminations for example lapout can be observed in seismic data and can be documented in continuous outcrops such as in the deserts of the western interior of north america and in closely spaced well log data sets in sparse data sets interpolation of lapout patterns introduces uncertainty in correlation and designation of sequences and systems tracts and their associated surfaces diachroneity of fluvial terrace deposits is documented using detailed facies architectural studies and calls into question the assumed chronostratigraphic significance of many so called sequence boundaries identified in the rocks of the cretaceous interior seaway of north america sequence boundaries formed during prolonged sea level falls may be less chronostratigraphically significant than transgressive surfaces formed during rapid rises as a consequence flooding surfaces are theoretically more significant and also have greater utility as allostratigraphic boundaries although they may also exhibit diachroneity tectonic unconformities produce differential lithospheric deformation which results in angular unconformities although the angle of discordance may be very small in the cretaceous interior seaway of north america such unconformities may be expressed by marine erosion in distal basin settings regional isochronous bentonites provide useful marker beds that clearly illustrate angular discordance in the fluvial realm such tectonic discontinuities may be indicated by changes in palaeocurrent orientations as well as by provenance changes although sequence stratigraphy provides a powerful methodology and theoretical framework for correlating and understanding the evolution of stratigraphic successions in the context of changing accommodation allostratigraphy remains the only accepted scheme for the formal naming of stratigraphic units based on bounding discontinuities whatever type of sequence stratigraphy or allostratigraphy is preferred in all cases it is key to recognize that sequence stratigraphy at its heart is the re ordering correlation and sometimes renaming of stratigraphic units on the basis of bounding discontinuities and their correlative surfaces as opposed to the arbitrary lithofacies oriented approach using broad facies zones for example shazam lines or arbitrary cutoffs such as is used in traditional lithostratigraphy

anatomy of shelf deltas at the edge of a prograding eocene shelf margin spitsbergen although shelf edge deltas are well imaged seismic features of holocene and pleistocene shelf margins documented outcrop analogues of these important sand prone reservoirs are rare the facies and stratigraphic architecture of an outcropping shelf edge delta system in the eocene battfjellet formation spitsbergen is presented here as well as the implications of this delta system for the generation of sand prone shelf margin clinoforms the shelf edge deltas of the battfjellet formation on litledalsfjellet and hogsnyta produced a 3 5 15 km shelf edge attached slope apron 70 m of sandstones proximally tapering to zero on the lower slope the slope apron consists of distributary channel and mouth bar deposits in its shelf edge reaches passing downslope to slope channels chutes that fed turbiditic lobes and spillover sheets in the transgressive phase of the slope apron estuaries developed at the shelf edge and these also produced minor lobes on the slope the short headed mountainous rivers that drained the adjacent orogenic belt and fed the narrow shelf and the shelf edge position of the discharging deltas made an appropriate setting for the generation of hyperpycnal turbidity currents on the slope of the shelf margin the abundance of organic matter and of coal fragments in the slope turbidites is consistent with this notion evidence that many of the slope turbidites were generated by sustained turbidity currents that waxed then waned includes the presence of scour surfaces and thick intervals of plane parallel laminae within turbidite beds in the slope channels and thick spillover lobes with repetitive alternations of massive and flatlaminated intervals the examined shelf edge to slope system now preserved mainly below the shelf break and dominated by sediment gravity flow deposits has a threefold stratigraphic architecture a lower progradational part in which the clinoforms have a slight downward directed trajectory a thin aggradational zone and an upper part in which clinoforms backstep up onto the shelf edge a greatly increased density of erosional channels and chutes marks the regressive to transgressive turnaround within the slope apron and this zone becomes an angular unconformity up near the shelf edge this unconformity with both subaerial and subaqueous components is interpreted as a sequence boundary and developed by vigorous sand delivery and bypass across the shelf edge during the time interval of falling relative sea level the studied shelf margin clinoforms accreted mostly during falling stage sea level below the shelf edge but the outer shelf later became estuarine as sea level became re established above the shelf edge

formation of deep incisions into tide dominated river deltas implications for the stratigraphy of the sego sandstone book cliffs utah u s a abstract the upper cretaceous sego member of the mancos shale in east central utah is composed of tidally deposited sandstones interbedded with intervals containing marine shales and thin wave deposited sandstones the tidal sandstones have been interpreted to comprise multiple amalgamated estuarine valley fills above a major sequence boundary that is incised into distal marine deposits of the underlying buck tongue shale according to this interpretation the deposits constitute the base of a thick transgressive succession within the sevier foreland clastic wedge alternatively lower sego sandstones have recently been interpreted by the authors to be tide dominated river delta deposits in an overall regressive interval of the foreland succession a cross section showing facies variations and stratigraphic surfaces within the lower sego member along 100 kilometers of the eastern book cliffs is used in this paper to refine depositional and sequence stratigraphic interpretations of these tidal deposits particularly the origin of deep incisions within the sego sandstones a strike oriented section of the lower sego member reveals tidal sandstone lenses 40 50 kilometers wide and tens of meters thick separated laterally by areas tens of kilometers wide that have no tidal sandstones facies variations within the tidal sandstones reflect depositional processes on tide dominated deltas that prograded obliquely into the shallow intracratonic western interior seaway of north america two major episodes of delta progradation and subsequent transgressions are interpreted to have formed tidal sandstone layers within the lower sego sandstone thinner tidal sandstone layers of more local extent are interpreted to reflect changes in tidal current strength but not necessarily shifts in shoreline position or major changes in water depth multiple origins are suggested for incised erosion surfaces within the lower sego sandstones firstly the tide dominated deltaic sandstones are floored by laterally discontinuous erosion surfaces these basal surfaces marking abrupt vertical changes in depositional process and coarsening of grain size are interpreted to record tidal scouring of the sea floor during shoreline progradation secondly sharp based upward coarsening deltaic sandstones are cut by numerous deep incisions with tens of meters of relief and locally they are entirely removed by erosion some of this deep erosion within the lower sego sandstone may reflect the upstream avulsion of incised distributaries during forced regression of deltas into the basin whereas others may have formed by tidal erosion of abandoned distributaries during more gradual progradation and subsequent retrogradation of deltas highly variable facies trends within incision fills are related to pronounced changes in sediment supply to different distributaries on the delta to differences between incisions cut during delta regression versus those cut during the start of transgression and to varying distances from delta axes when the entire coast was transgressed the influence of tides waned and wave generated currents ravined delta tops depositional interpretations of the sego member indicate that the buck tongue to neslen interval lies in a broadly regressive part of the foreland basin fill

large scale mass wasting events on the fraser river delta front near sand heads british columbia although the fraser river delta front supports coastal structures including ports a lighthouse jetties submarine power cables and sewage pipelines the stability of the delta front is little understood five large scale mass wasting events at the mouth of the main channel near sand heads have been detected by comparing successive bathymetric surveys conducted by public works canada between 1970 and 1986 these events can involve the downslope movement of more than 1 106 m3 of silty sand and the landward retrogression of the delta front crest of up to 350 m or more morphologic and sedimentologic evidence suggests that these events are slope failures which result from the liquefaction of silty sand rapid deposition at the river mouth is likely a prerequisite for failure although interstitial gas tidal currents waves and earthquakes also may contribute to failure these results have important implications for the foundation stability of the sand heads lighthouse and future coastal structures in t

geomorphology and potential slope instability on the fraser river delta foreslope vancouver british columbia le delta du fleuve fraser est localise dans une des regions ayant les plus hauts risques sismiques au canada et comprend pour une bonne part des sables fluviaux meubles tres connus comme possedant un potentiel eleve de liquefaction sismique des etudes recentes de la rive ouest du delta du fraser indiquent que la liquefaction cyclique durant un fort tremblement de terre est possible engendrant potentiellement des deformations incluant des extensions laterales un ramollissement cyclique et possiblement une coulee l on presente une evaluation preliminaire de la stabilite statique des pentes apres secousse dans laquelle les analyses ont ete limitees aux valeurs estimees des resistances au cisaillement ultimes ou a l etat d equilibre deduites de correlations avec les donnnees du terrain et aux contraintes de cisaillement calculees en partant de la bathymetrie du lit de mer existant l on a trouve que le coefficient postliquefaction de securite contre le glissement etait inferieur a l unite pour la pente de la terrasse superieure roberts en supposant une limite inferieure de resistance au cisaillement ultime equivalente a 0 06 p 0 les donnees pour evaluer la validite de cette hypothese sont insuffisantes cependant il y a abondance de depots de rupture le long de la base de la pente du delta

seabed instability due to flow liquefaction in the fraser river delta les ruptures par liquefaction de depots de sables l ches peuvent representer une menace importante pour les structures cotieres on a evalue a partir des concepts d etats stationnaires les contributions possibles de divers mecanismes de declenchement lors d une rupture par liquefaction qui a eu lieu en 1985 a l embouchure du chenal principal de la riviere fraser parmi les mecanismes qui ont pu declencher le glissement par liquefaction en 1985 on a etudie la sedimentation les vagues de surface et les marees basses l analyse montre qu une sedimentation rapide genere des contraintes de cisaillement dans la pente mais ne pourrait pas faire demarrer des ruptures par liquefaction lorsqu on evalue l effet des vagues de surface et leur capacite a causer des glissements de type coulee profonde on trouve qu il ne s accumule pas de pressions interstitielles significatives dues aux vagues de surface pouvant exister dans la region les marees basses ne peuvent pas non plus declencher de rupture dans des sables submerges et completement satures l apparition de gaz provoque cependant la desaturation des sediments ce qui peut induire des pressions interstitielles residuelles pendant les marees basses on emet donc l hypothese que c est la combinaison de sediments l ches de faibles quantites de gaz et de marees basses qui favorise les ruptures par coulees liquefiees dans le delta ces ruptures conduisent a des glissements regressifs

turbiditic levee deposition in response to climate changes the var sedimentary ridge ligurian sea abstract article history received 31 may 2010received in revised form 25 october 2010accepted 25 october 2010available online 31 october 2010communicated by d j w piperkeywords last deglaciationoverbank depositsturbidity currentsvar sedimentary ridgeligurian sea the var turbiditic system located in the ligurian sea se france is an intermediate mud sand rich system theparticularityofthevardeep seafanisitssinglechannelwithabruptbendsanditsasymmetricandhyper developed levee on the right hand side the var sedimentary ridge long term sediment accumulation on thevar sedimentary ridge makes this an ideal target for studying the link between onshore climate change anddeep sea turbidite stratigraphy this paper focuses on the establishment of the rst detailed stratigraphy ofthe levee which is used to analyze the timing of overbank deposition throughout the last deglaciation mainresults indicate that high variability in turbidite frequencies and deposition rates along the var sedimentaryridgearedeterminedbytwomainparameters 1 theprogressivedecreaseoftheleveeheightcontrollingtheabilityofturbiditycurrentstospilloutfromthechannelontothelevee and2 climaticvariationsaffectingthedrainage basin in particular changes in glacial condition since late last glacial maximum to early holocene compared to other deep water areas this study con rms the ability of turbiditic systems to record pastclimatic events on millennial timescales and underlines the in uence of european deglaciation on theobserved decrease in turbidite activity in the var canyon the presence of a very narrow continental shelf andasingle largechannel leveesystemmakesthevarsedimentaryridgeauniqueexampleofclimate controlledturbiditic accumulations 2010 elsevier b v all rights reserved

storm deposits from the quaternary outardes delta quebec canada abstract sand laminae interbedded with thicker pelitic sediments in the uplifted post glacial succession near outardes falls quebec are interpreted as storm deposits the sands were put into suspension by strong wave action in the coastal zone and transported offshore shallow water benthos were also carried offshore and deposited with the sand their presence indicates the coast was ice free at this time in places the pelitic units with sand laminae are confined to bathymetric lows suggesting that they may have been transported by low density turbidity currents the transition to this type of flow may have been aided by the presence of high subaqueous slopes and high concentrations of suspended fine sediments

the bouma sequence and the turbidite mind set abstract conventionally the bouma sequence bouma a h 1962 sedimentology of some flysch deposits a graphic approach to facies interpretation elsevier amsterdam 168 pp composed of ta tb tc td and te divisions is interpreted to be the product of a turbidity current however recent core and outcrop studies show that the complete and partial bouma sequences can also be interpreted to be deposits formed by processes other than turbidity currents such as sandy debris flows and bottom current reworking many published examples of turbidites most of them hydrocarbon bearing sands in the north sea the norwegian sea offshore nigeria offshore gabon gulf of mexico and the ouachita mountains are being reinterpreted by the present author as dominantly deposits of sandy debris flows and bottom current reworking with only a minor percentage of true turbidites i e deposits of turbidity currents with fluidal or newtonian rheology in which sediment is suspended by fluid turbulence this reinterpretation is based on detailed description of 21 000 ft 6402 m of conventional cores and 1200 ft 365 m of outcrop sections the predominance of interpreted turbidites in these areas by other workers can be attributed to the following 1 loose applications of turbidity current concepts without regard for fluid rheology flow state and sediment support mechanism that result in a category of turbidity currents that includes debris flows and bottom currents 2 field description of deep water sands using the bouma sequence an interpretive model that invariably leads to a model driven turbidite interpretation 3 the prevailing turbidite mind set that subconsciously forces one to routinely interpret most deep water sands as some kind of turbidites 4 the use of our inability to interpret transport mechanism from the depositional record as an excuse for assuming deep water sands as deposits of turbidity currents 5 the flawed concept of high density turbidity currents that allows room for interpreting debris flow deposits as turbidites 6 the flawed comparison of subaerial river currents fluid gravity flows dominated by bed load transport with subaqueous turbidity currents sediment gravity flows dominated by suspended load transport that results in misinterpreting ungraded or parallel stratified deep sea deposits as turbidites and 7 the attraction to use obsolete submarine fan models with channels and lobes that require a turbidite interpretation although the turbidite paradigm is alive and well for now the turbidites themselves are becoming an endangered facies

process regime changes across a regressive to transgressive turnaround in a shelf slope basin eocene central basin of spitsbergen abstract the sedimentological architectural and stratigraphic database from one investigated shelf margin clinothem complex in the eocene central basin of spitsbergen suggests that dominating process regimes and facies products may change several times during a sea level cycle even though the basin wide processes are constant continuous mountainside exposures were investigated by a combination of walking out of stratigraphic surfaces and geometrical elements closely spaced detailed vertical sections and tracing on helicopter photo mosaics the clinothem complex represents a regressive to transgressive shoreline complex and consists of five clinothem sets recognized by specific stacking patterns and sedimentary facies the regressive part preserves wave and river dominated deltaic deposits in a progradational to aggradational stacking pattern the delta clinothems consist of tide influenced distributary channels wave and hyperpycnal flow dominated mouth bars that on the shelf sourced turbidite filled slope channels and slope lobes the transgressive part of the clinothem complex preserves strongly tide dominated estuarine deposits underlain by tidal ravinement surfaces that cut down into deposits of wave dominated deltas this change in facies product on the inner shelf from wave to tidal at the regressive to transgressive turnaround was however not a basin wide process change inasmuch as the distributary channels also reflect tidal influence this suggests that tidal currents were present only in areas protected from waves and amplified by the lateral confinement of the estuary there was a process regime change on the middle to outer shelf from wave dominated highstand and falling stage delta complex to river dominated and wave influenced early lowstand delta complex the delta complex prograded across the shelf during highstand and during falling stage the relative sea level fall forced the deltas out to shelf edge the early lowstand delta mouth bars are volumetrically dominated by hyperpycnites indicating dominance of riverine processes the proportion of the hyperpycnal flow deposits decreased during the late lowstand and the delta complex became wave dominated anew the process regime change from wave dominance to fluvial dominance and back to wave dominance is interpreted to have occurred due to the seaward and then landward shift of the feeding river system whereas the tidal effects were dependent on shelter from waves and on the shoreline configuration

tidal signatures in a shelf margin delta based on its anomalous thickness 150 m and stratigraphic position above continental slope mudstone an upward coarsening succession consisting in part of tidal rhythmites in the glenelg field offshore nova scotia canada is interpreted to be a strongly tide influenced shelf margin delta deposit a large funnel shaped erosional shelf edge invagination is observed where the paleoshelf edge is resolved in three dimensional seismic data adjacent to glenelg we propose that the delta at glenelg prograded into a similar shelf edge invagination within which tidal currents were amplified and wave energy was attenuated given that funnel shaped invaginations e g slope canyon heads slump scars fluvially incised knickmarks are relatively common along modern shelf edges and that fluvio deltaic systems should be focused into these topographic lows during regression across the shelf it seems likely that shelf edge invaginations play an important but underappreciated role in mediating terrigenous clastic sedimentation during sea level lowstands

sulfur isotopic trends and iron speciation from the c 2 0 ga pilgujarvi sedimentary formation nw russia abstract sulfide sulfur isotope values and iron speciation data are reported here for sediments from the 2 0 ga old pilgujarvi sedimentary formation pechenga greenstone belt nw russia sulfides are abundant throughout the c 1400 m thick turbiditic sandstone siltstone shale succession and present as pyrite and pyrrhotite a stratigraphic trend is discernible with respect to sulfide mineralogy and sulfur isotopic compositions changing up section from highly to less variable and positive 34 s values the occurrence of pyrrhotite particularly high in the upper part of the section is thought to be the result of decomposition of pyrite during low grade metamorphism this is evidenced by the crystallographic habit and sulfur isotopic composition of the different sulfide minerals the 34 s of both sulfur species is quite variable in the lower part of the formation 9 5 to 18 7 while the upper part displays a smaller fluctuation in 34 s 4 4 13 3 the pyrrhotite is generally depleted in 34 s by approximately 3 6 average isotopic difference between pyrrhotite and pyrite compared to the pyrite this shift in the sulfur isotopic composition results from thermal decomposition of pyrite the overall spread in 34 s is indicative for the microbial reduction of sulfate but 34 s values suggest a sulfate limited environment in the upper part of the formation we note however that the sulfate limitation is restricted to the pore water realm caused by high sedimentation rates that inhibited a sufficiently high sulfate flux from the overlying water column into the sediment based on iron speciation data a previous characterization of the depositional environment as non euxinic can be specified more precisely we note that the siliciclastic succession of the pilgujarvi sedimentary formation was deposited under anoxic and ferruginous water column conditions derived from high ratios of fe hr fe t and low ratios of fe py fe hr

the owen ridge uplift in the arabian sea implications for the sedimentary record of indian monsoon in late miocene abstract the pelagic cover of the owen ridge in the arabian sea recorded the evolution of the indian monsoon since the middle miocene the uplift of the owen ridge resulted from tectonic processes along the previously unidentified miocene india arabia plate boundary based on seismic reflection data tied with deep sea drilling to track the miocene india arabia plate boundary we propose a new timing for the uplift of the owen ridge and highlight its impact on the record of climate changes in pelagic sediments the new dataset reveals a fracture zone east of the owen ridge corresponding to the fossil plate boundary and documents that the main uplift of the owen ridge occurred close to 8 5 ma and is coeval with a major uplift of the east oman margin late miocene deformation at the india arabia plate boundary is also coeval with the onset of intra plate deformation in the central indian ocean suggesting a kinematic change of india and surrounding plates in the late miocene the uplift of the owen ridge above the lysocline at 8 5 ma accounts for a better preservation of globigerina bulloides in the pelagic cover previously misinterpreted as the result of a monsoon intensification event

high resolution stratigraphy and sedimentary evolution of coarse grained canyon filling turbidites from the upper cretaceous transgressive megasequence campos basin offshore brazil abstract coniacian to lower maastrichtian coarse grained turbidites fill intra slope fault controlled canyons in the campos basin off shore brazil they form part of an upper albian to lower paleocene transgressive succession characterized by onlapping deepening upward sedimentation throughout the eastern brazilian margin in the carapeba and pargo crp pg oil fields the turbidites consist mainly 95 of graded beds without any other sedimentary structures individual beds are up to 12 m thick and are composed of small pebble 2 cm to granule rich sandstones and medium to very coarse sandstones the finer grained portions of these graded beds show better sorting and higher porosity and these characteristics can be recognized in density logs use of 92 density logs calibrated w th 13 cores permitted the mapping of 198 coarse grained turbidites in the crp pg turbidite system the turbidites form eight thinning and fining upward facies successions some bounded by regional unconformities or local erosion surfaces the successions are 27 140 m thick and contain 7 58 turbidites their durations are estimated to be between 0 4 0 9 m y they form 1 12 km wide tabular or linguoid sandstone bodies in which the younger or more distal turbidites become finer grained thinner bedded and more discontinuous upsection and downcanyon the successions are stacked in an overall retrogradatioual pattern for at least 20 km recording the backfilling of the crp pg canyon turbidites in the crp pg area were probably deposited during falls of relative sea level that punctuated the overall transgressive setting of the late cretaceous and early tertiary there is a mismatch between the number of successions eight and the number of time equivalent third order fluctuations of relative sea level four and part of a fifth haq et al 1988 suggesting that eustatic sea level fluctuation was not the dominant control on most of the successions cross sections and isopach maps of the successions do not suggest internal channeling and a channel fill origin for the fining and thinning upward successions seems unlikely we therefore suggest that episodic tectonic reactivation in the uplifted precambrian source area and faulted basin margin led to relatively abr pt increases in the volume of sediment supplied to the head of the canyon across a narrow shelf steady denudation and decreasing supply of sediment led to formation of the fining and thinning upward successions

sea level fall below the shelf edge without basin floor fans a fall of sea level to below the shelf edge formation of type 1 sequence boundary increases greatly the likelihood of sand delivery into deep water basin floor areas although an unusually high sediment supply can bring significant volumes of sediment to the shelf edge at any time an eocene ypresian data set from seismic scale mountainside outcrops of shelf slope clinoforms illustrates that a fall of sea level below the shelf edge produces significant sand accretion on the shelf margin but brings no sand out onto the basin floor fall and subsequent rise of relative sea level are documented by the style and topographic position of successive shelf edge to slope clinoforms each representing a shelf edge delta with its greatly extended slope apron of turbidite lobes sheets and chutes a downslope shift of clinothems at the shelf edge and a headward cannibalization of the oldest perched slope deltas are the criteria for recognition of 1 the time interval of sea level fall and 2 the position of sea level below the shelf edge the lowest sea level is recorded by the most basinward clinothem set with a high density of erosive turbidite chutes at its upper surface the sequence boundary wave eroded terraces at its updip near shelf edge end identify the shoreline position at lowest sea level aggradation and landward stepping of clinothems reflect subsequent rise of relative sea level the fall to rise configuration and especially the occurrence of peak erosion at the time of lowest sea level are compelling evidence for placing the type 1 sequence boundary at the fall to rise turnaround and not along the surface onto which the clinothems downlap the excellent exposure downdip as well as along strike of the clinoform complex demonstrates the absence of sand accumulation beyond the base of slope the slope turbidites were produced from dilute nonignitive flows and caused significant shelf margin accretion the data show that such slopes can be extremely sand prone and that sea level fall below the shelf edge does not necessarily result in basin floor sand deposits beyond the base of slope particularly where canyons have not been eroded into the slope

directional petrological characterisation of deep marine sandstones using grain fabric and permeability anisotropy methodologies theory application and suggestions for integration abstract different methods for quantifying preferred grain orientation or grain shape fabric in sandstones are reviewed and their value for the reconstruction of palaeocurrent direction and preferred direction of pore fluid flow is reassessed critically based on existing knowledge from literature and new grain fabric data it is shown that petrographic analysis has distinct merits because grain fabric can be determined with low equipment costs and population statistics are based on the orientation of individual grains several recommendations are given how to standardise procedures for acquisition of grain fabric through microscopy these recommendations include 1 the careful selection of cross section orientations to acquire apparent long grain axes that are representative of true long grain axes 2 the preferred measurement of the coarsest grains in cross section and 3 a new statistically founded method to select a subset of grains that is representative of the total population of grains in a sandstone sample magnetic techniques that use anisotropy of magnetic susceptibility ams as a proxy for grain orientation require specialised equipment and are more restricted in statistical evaluation but these methods benefit greatly from being able to measure a large number of grains in a three dimensional space in a short amount of time and with a lower sensitivity to user bias of the two magnetic techniques discussed in this paper the new enhanced ams method in which rock magnetic properties are enhanced by introducing magnetite into the pores and as precipitates on grain surfaces is regarded to be an improvement over the traditional natural ams method in which only the natural assemblage of magnetite particles present in the rock is analysed enhanced ams measures the preferred orientation of essentially all grains in a rock sample thus providing the shape fabric of a hydrodynamically more accurate representation of framework grains than natural ams through a small technical modification the enhanced ams method can be used to obtain a magnetic cast of the pore network of a rock sample so that the resulting ams is controlled by the shape anisotropy of the individual pores it is commonly assumed that long axes of sand grains in sedimentary deposits parallel the direction of the flows that formed the deposits this concept is challenged by a new systematic study of grain fabric in deep marine turbidites it indeed appears that grains in ripple cross laminated divisions of turbidites dominantly attain a preferred orientation parallel to the palaeoflow direction but grains in plane parallel laminated divisions have an additional flow perpendicular mode which suggests a contribution of rolling grain transport three different fabric modes occur in massive structureless sandstones and massive divisions in turbidites apart from flow aligned and flow perpendicular modes there is a statistically significant but hydrodynamically enigmatic flow oblique mode with an average azimuthal deviation of 40 this large variation of fabric types suggests that a similar variation exists in preferred paths of pore fluid flow within turbidites controlled to at least some degree by depositional process this is confirmed by independent laboratory measurements of permeability anisotropy on samples for which grain fabric data are available and thus defines grain fabric analysis as a viable alternative to traditional permeametry techniques

turbidite variability and architecture of sand prone deep water slopes eocene clinoforms in the central basin spitsbergen abstract the architecture and turbidite variability within six wedge shaped downslope thinning sand prone slope accumulations are documented from eocene shelf margins on spitsbergen the central basin formed as a small foreland or piggy back basin and the studied turbidites accumulated mainly on the slope portion of sand prone clinoforms that developed during depocenter migration and infilling of the basin the shelf margin clinoforms have amplitudes minimum water depths from 100 to 350 meters and their shelf slope and basin floor segments are well imaged and can be walked out along many of the mountainsides only a small percentage of the clinoforms are sand prone and these developed when sea level occasionally fell to or below the shelf edge of the sand prone clinoforms some had their sand budget partitioned mainly out onto the basin floor basin floor fans but most trapped the sand on the slope only the latter are now visible as downslope thinning wedges some 2 5 3 5 km in downdip extent the turbidites within this type of clinoform have been examined and classified the lower slope to base of slope segment of the studied clinoform complexes are dominated by lobes consisting of broad shallow channels and sheet like turbidites becoming heterolithic and muddy out on the basin floor beds on the lower slope vary from thick up to 4 5 meters ungraded or laminated sandstones to thinner ungraded sandstones with coarse cappings the middle slope segment of clinoform complexes is dominated by narrow channels chutes that feed downslope to progradational chute mouth lobes chutes contain ungraded and laminated sandstone beds up to 3 m thick whereas the chute mouth lobes show alternations of thinner ungraded to laminated or rippled sandstones these lobes become more heterolithic and muddy downslope the shelf edge to upper slope segment of clinoform complexes is dominated by upward coarsening and thickening sheetsands of steep fronted shelf edge deltas the sandsheets of the delta front can be traced updip into mouth bar and distributary channel sandstones it is argued that shelf margin accretion represented by the sand prone slope wedges was achieved mainly by sand laden currents that flooded from the shelf edge as hyperpycnal flows this hypothesis is supported by 1 the direct connection between channel and mouth bar systems at the shelf edge and the turbidites of the slope lobes 2 the systematic progradational character of the slope lobes 3 the absence of large scale slump scars gullies or canyons on the slope and 4 the dominance of a type of turbidite that implies deposition from sustained flow detailed examination of the architecture of one of the slope wedges shows that there are unconformities developed within the stratigraphy below the shelf edge and that these erosional terraces beheaded the deltas perched on the uppermost slope the erosion surfaces indicate fall of sea level to this position despite the magnitude of this fall up to 80 meters the lack of canyons on the slope prevented the construction of basin floor fans such falls of sea level on non canyoned slopes simply promote sand prone accretion of the shelf margin

carbonate debris flows cow head group western newfoundland abstract the cow head group is an allochthonous cambro ordovician sequence of deep water limestone conglomerates mudstones to grainstones minor quartz sandstones siltstones and shales platy clast conglomerates and boulder rich megaconglomerates as much as 100 m thick exhibit features similar to those described for subaerial debris flows that is flat sharp bases with only minor evidence for erosion poorly developed clast fabric with tilting of platy clasts at right angles to the flow direction boulders floating within flows or projecting above the tops of flows irregular flow tops indicating primary relief above the sea floor and tapered flow margins snouts snout geometry and the extent of boulder projection both allow calculation of debris static strength these results combined with measured flow thickness permit calculation of minimum and maximum paleoslope gradients original debris static strengths were in the range of 103 to 105 dynes cm2 similar to the observed range in subaerial flows calculations yield bottom gradients of l l 8 but independent field data suggest that the paleoslope dip was on the order of only a few degrees this constraint suggests that debris strength was substantially reduced during flow probably by excess pore fluid pressures thus permitting flow on very gentle slopes the paleoslope orientations used in this study are substantially different from those previously published by hubert et at 1977

non cohesive silt turbidity current flow processes insights from proximal sandy silt and silty sand turbidites fiordland new zealand silt rich turbidites are commonly interpreted as distal marine deposits they are associated with interlaminated clay and silt deposition from the upper and rear portions of turbidity currents here multibeam bathymetry and shallow sediment core data from the intra slope secretary basin fiordland new zealand located 10 km from shore are used to describe a suite of late holocene proximal sandy silt and silty sand turbidites that contain negligible clay and a wide variety of vertical grading patterns the steep rugged catchment to the secretary basin is dominated by a complex tributary turbidite channel network that feeds the low gradient secretary basin floor intra slope lobe sediment core t49 is located within the lobe and positioned between shallow channels that are prone to deposition from decelerating silty sand and sandy silt turbidity currents the wide variety of sedimentary structures and vertical grading patterns dominated by inversely graded beds implies a range of non cohesive flow processes with deposition from multiphase mixed mode turbulent and laminar flows that have undergone a variety of up dip flow transformations most flows were initially erosive followed by deposition of partitioned 2 or 3 phase mixed mode flows that include high density transitional and laminar flows that can be fore or after runners to low density turbulent flow sections turbulence is inferred to have been suppressed in high density flows by increasing flow concentration of both sands and silts the very fine and fine sand modal grain sizes of sandy silt and silty sand turbidites are significantly coarser than classical abyssal plain silt turbidites and are generally coarser than overbank silt turbidites while the low percentage of clays within secretary basin sandy silt and silty sand turbidites represents a fundamental difference between these and other silt and mud turbidites we suggest these beds represent a previously undescribed suite of proximal continental slope deposits c 2016 elsevier b v all rights reserved

basic building blocks and process variability of a cretaceous delta internal facies architecture reveals a more dynamic interaction of river wave and tidal processes than is indicated by external shape abstract although delta building processes and the resultant facies and facies associations have been studied for over a century there remains a lack of well documented facies architectural studies of ancient deltas in this study architectural element analysis is applied to determine the basic building blocks of a cretaceous delta at the top of the upper turonian wall creek member exposed along the western flanks of the powder river basin wyoming we document the bed scale basic building blocks of this ancient delta and show them in the context of their facies and stratal variability and their hierarchical spatial arrangement within a single deltaic parasequence we also test the idea that external sand body shape may not reflect the internal facies complexity as has recently been suggested in studies of several modern deltas including the burdekin in australia the brazos in the gulf of mexico and the baram trusan in borneo five orders of bounding surfaces separate six facies architectural elements in the prodelta and delta front deposits these elements are prodelta fines pf frontal splay fs channel ch storm sheet ss tidally modulated deposit tm and bar accretion ba seasonal to decadal river floods are thought to represent the main building phases of the delta producing channels bars and frontal splay elements during intervening periods the delta was reworked by waves storms and tides producing tidally modulated and storm sheet elements due to the complex interactions of river effluents with waves storms and tides the delta is interpreted as mixed influenced regional sandstone isolith facies and paleocurrent maps help to reconstruct the paleogeography and show how the various architectural elements varied across the delta front the channels bars frontal splays and tidally modulated elements are found only near the distributary mouth whereas the storm sheets occur extensively away from the distributary mouth the plan view morphology of the studied delta shows a smooth fronted arcuate to cuspate shape which should indicate wave dominance in contrast our analysis of the internal facies architecture shows that the delta was constructed rapidly during major river floods with significant tidal reworking additional outcrop mapping shows that storm wave reworked sands are attached to the flanks of the system previously published delta models predict incorrectly that the tidal reworking of a river flood dominated system should result in a more bird foot shape versus the lobate geometry that is actually mapped our analysis of internal facies versus external shape matches similar observations on several modern deltas and suggests that external shape is a poor indicator of internal facies complexity

origin and timing of sand injection petroleum migration and diagenesis in tertiary reservoirs south viking graben north sea petrographic fluid inclusion and carbon and oxygen stable isotope studies of tertiary injectite reservoirs in the south viking graben of the north sea allow an understanding of the origin and timing of sand injection petroleum migration and diagenesis injection from shallowly 400 m 1300 ft buried paleocene and eocene unconsolidated sandstones occurred at the end of the eocene probably in response to earthquake activity liquid oil was already present in the parent sands prior to injection and leaked from the injectites to the seabed upward migrating oil and basinal brines mixed with downward invading mixed meteoric marine pore fluids in the injectites causing extensive biodegradation of the oil biodegradation of oil provided the driver for early carbonate cementation in injectites causing diminished reservoir quality however early carbonate cementation also sealed off the injectites as potential escape routes for petroleum from the underlying parent sands oil and gas continued to migrate into the reservoir parent sands upon increased burial causing a mixing of high api oil with the early charged extensively biodegraded low api oil the study of early diagenetic imprints reveals the evolution of injectite reservoirs which forms the basis for understanding how to explore and develop them

sediment transport in a submarine channel system fraser river delta canada abstract the sand heads seavalley is a submarine channel system seaward of the mouth of fraser river canada soundings and sonographs reveal that the seavalley is composed of tributary channels that coalesce downslope into a single sinuous channel that splits into distributary channels at the base of the slope the channels are inferred to result from turbidity currents generated by periodic liquefaction of sandy sediment at the mouth of the river bathymetric surveys of a river mouth slope failure in 1985 are used to estimate sediment transport rates for a turbidity current generated by the failure these rates are compared to predictions using a turbidity current model based on relationships between settling velocities of surface sediments and shear velocities required to transport the sediment as suspended and wash loads model predictions that assume suspended load transport are much lower than estimates from the landslide but predictions based on wash load transport show reasonable agreement the better agreement with the wash load model may be because grain sizes in the deposits are controlled by the sizes of sediment supplied to the distributary mouth bar by the river rather than by the competency of the turbidity curre t itself

slope failures and stability analysis of shallow water prodeltas in the active margins of western greece northeastern mediterranean sea sediment instabilities are common on the prodeltas of the seismically active continental margins of western greece sediment failures on the low angle 0 5 2 prodelta slopes manifest themselves as successions of peripheral rotational block slumps restricted to the foresets of the late highstand systems tract hst the individual slump blocks are about 80 150 m long and are bounded by growth faults acting as curved slip planes that extend to a mean depth of 10 15 m below seafloor shear planes develop in the lower part of muddy and or gas charged hst foresets deeper basal transparent muddy layers of the early hst bottomset together with the late pleistocene transgressive systems tract sequences tst are mostly unaffected on the steeper 2 6 fan delta slopes of the western gulf of corinth debris flows and avalanches with a significant retrogressive component dominate slope destabilisation sediment cores taken from landslide scarps and slide planes penetrated gas bubble releasing sediments thereby indicating that failure planes are in the late hst foresets upper part of the early hst bottomsets gas charged zone the foresets of the hst prodelta deposits display high water content 30 80 low bulk density 1 4 1 9 g cm 3 and relatively low values of undrained shear strength 3 20 kpa the water content of the hst distal muddy bottomsets is relatively higher 50 110 and bulk density relatively lower 1 3 1 7 g cm 3 with low values of shear strength 2 10 kpa the shear strength of the gas releasing sediment layer displays lower values 2 9 kpa relative to the overlying post failure muddy sediments of the late 100 300 years slope stability was calculated using the normalised soil parameter nsp method under undrained conditions for normally consolidated prodelta sediments this analysis indicates that instabilities could be induced by critical earthquake ground accelerations of 26 6 29 6 g for the hst foresets and 12 4 14 1 g for the basal transparent layer belonging to the early hst bottomsets consequently the early hst bottomsets has to be considered a potentially unstable layer since the regional peak ground accelerations pgas for the next 50 years are expected to range from 19 to 30 g moreover our results show that new glide planes in the prodeltaic sediment bodies of the seismically active continental margins of western greece will likely develop from the gas charged sediments of the lower part of the hst foresets to the upper part of early hst bottomsets

powerful unconfined turbidity current captured by cabled observatory on the fraser river delta slope british columbia canada turbidity currents are one of the main sediment transport processes on earth yet are notoriously difficult to monitor directly this article presents the first direct and high bandwidth observation of a turbidity current using a cabled sea floor observatory on 5 june 2012 a platform on ocean networks canada located in 107 m of water on the fraser river delta slope was displaced downslope and severed from its data cable the platform weighed ca 1000 kg in water the event took place during high river discharge high tides and rapid sediment accumulation on adjacent upslope areas of the sea floor data recorded as it tumbled downslope allow a reconstruction of the flow which is inferred to have been an unconfined turbidity current lines of evidence indicate that the flow came in as a bed hugging wedge and built up to between 1 m and 4 m in height as the head passed through comparison with laboratory data suggest that the flow was initially supercritical while the adjacent slope offset to the north clearly exhibits change over an annual resurvey period the bathymetry directly at the event location show no resolvable change over a period from seven months before the event to one month after sediment cores collected after the event were pervasively biototurbated and they contain no obvious deposit connected with this event the remarkable aspects of this research follow the flow was powerful enough to carry a 1 tonne platform and sever a heavily armoured cable the current occurred on the unchannelized open slope this powerful event failed to cause discernible seabed elevation change the flow was triggered by tidal conditions the event was detected by a purpose designed cabled observatory thus providing high bandwidth data and also alerting researchers in real time to mount follow on investigations

a river mouth submarine channel and failure complex fraser delta canada abstract high resolution seismic and side scan sonar surveying combined with coring of the fraser delta slope seaward of the main fluvial distributary has revealed a complex suite of morphologic units which include undisturbed delta slope sediments shallow rotational slides relict and active slope channels debris accumulations and ponded turbidites sediment transport through the main submarine channel is thought to be primarily by debris flows rather than by turbidity currents although this is a seismically active region the instability related features described here are probably due primarily to rapid sediment deposition on the upper delta slope at the river mouth

flow and bed profile in meandering sand silt rivers mathematical models for defining three dimensional flow and bed topography in sinuous channels with suspendable bed material are presented it is shown theoretically that the secondary flow in sinuous channels shows a reduction in its magnitude below that of a uniformly curved channel and also displays a phase lag relative to the channel plan form the model for bed topography is derived by considering the sediment balance for bed load and suspended load the transport rate and direction all of which are governed by the three dimensional flow a laboratory test supports the model the present study has made it possible to predict the large scale bed topography of meandering sand silt rivers including such features as the magnitude and the location of local scour and point bar deposits

sediment transport of fine sand to fine gravel on transverse bed slopes in rotating annular flume experiments large scale morphology in particular meander bend depth bar dimensions and bifurcation dynamics are greatly affected by the deflection of sediment transport on transverse bed slopes due to gravity and by secondary flows overestimating the transverse bed slope effect in morphodynamic models leads to flattening of the morphology while underestimating leads to unrealistically steep bars and banks and a higher braiding index downstream however existing transverse bed slope predictors are based on a small set of experiments with a minor range of flow conditions and sediment sizes and in practice models are calibrated on measured morphology the objective of this research is to experimentally quantify the transverse bed slope effect for a large range of near bed flow conditions with varying secondary flow intensity sediment sizes 0 17 4 mm sediment transport mode and bed state to test existing predictors we conducted over 200 experiments in a rotating annular flume with counterrotating floor which allows control of the secondary flow intensity separate from the streamwise flow velocity flow velocity vectors were determined with a calibrated analytical model accounting for rough bed conditions we isolated separate effects of all important parameters on the transverse slope resulting equilibrium transverse slopes show a clear trend with varying sediment mobilities and secondary flow intensities that deviate from known predictors depending on shields number and strongly depend on bed state and sediment transport mode fitted functions are provided for application in morphodynamic modeling

amalgamation surfaces bed thicknesses and dish structures in sand rich submarine fans numeric differences in channelized and unchannelized deposits and their diagnostic value abstract hydraulic differences between channelized and unchannelized flows in sand rich submarine fans result in different distributions of amalgamation surfaces bed thicknesses and dish structures in successions of these two different environments distribution trends of these fabrics were quantified for the sand rich fans of the reiselsberger sandstein cenomanian turonian these trends can be used as criteria to distinguish channelized from unchannelized paleoenvironments of sand rich submarine fans amalgamation surfaces in the studied fans channelized regions are considerably more abundant than in the unchannelized fan areas in unchannelized deposits tabular amalgamation surfaces outnumber nontabular ones whereas the opposite occurs in channelized successions these results indicate a higher degree of erosive power of gravity driven sediment flows in channels as a result of a greater flow thickness higher flow velocity and turbulence the average turbidite layer thickness in channelized successions is markedly greater than in unchannelized deposits layer as defined herein this is mainly attributed to the combined effects of differences in sediment fall out rate and the inefficiency of sand rich suspensions to transport sand in the proximal and channelized fan areas more sediment is deposited from a flow in the form of a layer than in distal unchannelized fan regions despite a higher degree of erosion in channels the greater average bed thickness in channel fills is a function of layer thickness and more frequent amalgamations bed as defined herein dish structures seem to be considerably more common in midfan than in outer fan successions this may indicate a higher sedimentation rate from individual suspension currents in midfan areas

stability of the fraser river delta front the distributary front deposits of the delta consist mainly of interlayered sand and silt and lie in one of the most seismically active zones in canada subsurface deposits at the north tend to be siltier than those at the south sediments on the surface of the delta slope range from clayey silts at the north to pure sands at the south slope angles vary from 23 at the head of the slope to 1 2 within 2 km beyond the tidal flats hydraulic bedforms observed on the sandy slopes southeast of the main channel gradually increase in size from small ripples to large asymmetric sand waves 2 3 m high and approximately 30 m long they are generated primarily by flood tidal currents which scour the seabed to a water depth in excess of 100 m formation of gullies which crease the delta slope probably is initiated principally by failure of oversteepened deposits at a channel mouth previous studies have suggested that the large hummocks or ridges at the base of the slope off the main channel have been formed by the co

initiation of turbidity currents outcrop evidence for eocene hyperpycnal flow turbidites abstract the most widely used although not as widely documented explanation for initiation of turbidites is the conversion of catastrophic sediment failures into turbidites such instantaneous sediment failures generate short lived surge type flows that deposit turbidite beds described as bouma sequences in this communication we present data from the eocene central basin of spitsbergen that shows turbidite systems that are volumetrically dominated by thick ungraded and laminated sandy turbidite beds deposited by gradual aggradation from sustained flows sustained flows are long lived and more or less continuous they can be generated by a variety of mechanisms e g 1 instability during volcanic eruptions and the consequent remobilisation of unconsolidated material 2 seismically triggered subaerial sliding within the drainage 3 storm surges 4 retrogressive slope failure 5 breaching and 6 hyperpycnal flows our database shows that in the eocene central basin the sustained flows were generated by hyperpycnal flows i e by direct river effluent the hyperpycnal flow turbidites have been recognized on the basis of 1 physical connection between fluvial and turbidite channels at the shelf edge 2 abundance of thick turbidite sandstone beds 3 sand prone nature of the turbidite systems 4 downslope changes of individual thick sandy turbidite beds and their collapsed pinch out segments 5 great abundance of continental material leaves coal fragments in turbidite beds 6 low abundance of associated slumped or debris flow beds and 7 the occurrence of turbidites in systematically accreted shelf margins these features strongly suggest that hyperpycnal flow generated by direct river effluent deposited significant number of turbidite beds in the documented slope and basin floor turbidite successions we also argue that the hyperpycnal flows are preferentially fed into the deepwater slopes beyond the shelf edge during the falling stage and lowstand of relative sea level the turbidite beds were studied in the context of seismic scale 1 15 km dip oriented outcrops by measuring detailed vertical sections following individual beds and packages of beds downslope for distances over 5 km lateral mapping and helicopter taken photomosaics

sea level fluctuations and the geometric variability of tide dominated sandbodies abstract this paper presents examples of various large tidal sandbodies from the eocene roda sandstone in the southern pyrenees and the late pleistocene and early holocene in the east china sea an attempt is made to summarize the geometric variability of these large tidal sandbodies in relation to the sediment supply and tidal discharge of the depositional system transverse sand bars were developed in low sinuosity high gradient channels with high influxes of coarse sediments and water from fluvial systems tidal point bars were formed in meandering low gradient estuarine channel where tidal influence was stronger and sediment was finer than those of the transverse sand bar a tidal delta complex was built up at the estuary mouth with an abundant sediment supply and an increased tidal discharge tidal sand ridges were formed when relict fluvial or deltaic sands were eroded and reworked by strong tidal currents during subsequent sea level rise since the sediment supply and the tidal discharge of the depositional system were closely related to the eustatic sea level change and basin subsidence i e the relative sea level change special attention will be given to the relationship between geometric variability of tidal sandbodies and the sequence stratigraphic framework in which various sandbodies occurred three orders of eustatic sea level fluctuations can be recognized the third order eustatic sea level cycle together with basin subsidence controlled the development of systems tracts and the occurrence of different tidal sandbodies such as estuary and tidal flat facies during the late stage of a lsw systems tract type 1 sequence or a sm systems tract type 2 sequence tidal point bar facies tidal delta facies or tidal sand ridge facies during a tr systems tract estuary facies during an early hs systems tract and fluvial sand bar facies in a late hs systems tract and the early stage of a sm or lsw systems tract there are also the fourth order and fifth order eustatic fluctuations which are superimposed on the third order eustatic changes and have important control on the build up abandonment and preservation of composite and single tidal sandbodies respectively since the deposition of tidal sandbodies is very sensitive to eustatic sea level changes recognition of various tidal sandbodies is important in sequence stratigraphy analyses of sedimentary basins and in the facies prediction of clastic sediments in basin modelling

probable sequential arrangement of depositional systems on cratons depositional systems recorded in cratonic successions are formed by fluvial eolian deltaic wave storm and tidal processes their spatial and temporal distribution is controlled by tectonic uplift the areal width over which marine processes inundate cratons and climate the craton width of marine sedimentation appears to control the lateral and vertical distribution of sediment depositional systems for transgressive clastic sequences craton widths are narrow and are dominated by subtidal and coastal storm generated and wave dominated barrier depositional systems during early phases of transgression as the craton becomes submerged over a wider area tidal depositional systems become dominant and include subtidal sand bodies and coastal tidal flats during regression fluvial and eolian depositional systems become dominant tectonism controls the facies patterns in two ways if tectonism is active during deposition cratonic sequences of narrower shelves dominated by wave and storm depositional systems seem to be characteristic if tectonism consists of uplifts confined to the margins of the craton sediment yield increases onto the craton favoring regressive fluvial and deltaic depositional systems although the climatic variable is more difficult to evaluate it tends to control the occurrence of clastic sediments more humid and carbonate sediments arid tropical in tropical and subtropical latitudes a carbonate facies distribution is favored and the stratigraphic development of depositional systems controlled by increasing width of cratonic inundation by marine processes occurs in much the same way as suggested for clastic sediments if tectonic uplift is active in areas adjoining carbonate cratonic sedimentation a regressive deltaic clastic wedge occurs instead of nonmarine eolian sediments which appear to be normative regressive sediments in carbonate terrains

interplay between shoreline migration paths architecture and pinchout distance for siliciclastic shoreline tongues evidence from the rock record facies geometry and key internal stratigraphic surfaces from eight cretaceous and eocene clastic shoreline tongues have been documented the regressive parts of all the studied tongues represent storm wave influenced strandplains deltas or fan deltas and the regressive shoreline trajectories varied from descending to ascending the transgressive parts of the tongues are dominated by either estuarine or coastal plain deposits the distance from the coeval up dip non marine deposits to the basinward pinchout of amalgamated shoreface sandstones measured along depositional dip is here termed the sand pinchout distance the study shows that the angle of regressive to transgressive turnaround defined by the angle between the regressive and subsequent transgressive shoreline trajectories and the process regime during turnaround largely control the sand pinchout distance the amount of transgressive erosion can also partly control the pinchout distance but this parameter was comparable for the different examples presented here if the type of depositional system at turnaround and the depth of transgressive erosion are constant small angles of turnaround are associated with large pinchout distances whereas larger angles of turnaround result in smaller pinchout distances the model developed allows sand pinchout distance to be predicted using data for the landward parts of shoreline tongues the dataset also shows that steeply rising aggrading shoreline trajectories tend to produce more heterolithic sandstone tongues than those formed by lower angle trajectories

the paleocene eocene thermal maximum petm in svalbard clay mineral and geochemical signals abstract for the first time the paleocene eocene thermal maximum petm interval has been identified in drillcores and field outcrops from the paleogene central basin in svalbard based on mineralogical and geochemical information grumantbyen and frysjaodden formations a more than 300 m thick paleogene interval representing deltaic delta influenced marine shelf and deep water slope environments the petm has been recognized in the deepest and most distal deposits in the lower parts of the frysjaodden formation here this global event is displayed in clay mineralogical distributions as significantly increased kaolinite abundances reflecting a period with intensified chemical weathering in the land areas surrounding this paleogene basin the period was characterized by dominantly reducing sea floor conditions as seen in the th u distribution and the well developed parallel lamination in the pyrite rich shales all to be expected during an interval with increased temperature and precipitation

slump and debris flow dominated upper slope facies in the cretaceous of the norwegian and northern north seas 61 67 n implications for sand distribution a regional sedimentological study of cretaceous sequences in the mid norway region norwegian sea and in the agat region agat field area northern north sea reveals that these sequences were predominantly deposited in an upper continental slope environment by slumps and debris flows examination of nearly 500 m of core from 14 wells shows eight distinct lithofacies facies 1 contorted conglomerate and pebbly sandstone represents deposits of sandy slumps and debris flows possibly in a channel setting facies 2 contorted sandstone is the most widespread and is the product of sandy slumps and debris flows facies 3 contorted mudstone indicates deposition from muddy slumps and debris flows facies 4 rippled sandstone suggests bottom current reworking facies 5 gr ded sandstone represents turbidity current deposits and is very rare facies 6 laminated mudstone is a product of pelagic or hemipelagic deposition facies 7 cross bedded sandstone is indicative of tidal processes and facies 8 laminated sandstone represents delta front and shelf deposits these facies and their association suggest a shelf edge delta to upper slope environment of deposition existing core data document deltaic facies only in the mid norway region the proposed shelf edge delta and upper slope model has important implications for sand distribution 1 this model provides an alternative to the conventional submarine fan model previously applied to these sequences 2 although slump and debris flow emplaced sands are usually discontinuous and unpredictable highly amalgamated slump and debris flow sands may develop thick reservoirs 3 by using the eocene frigg formation as an analog it is predicted that externally mounded seismic facies in the study area may be composed of sandy slumps and debris flows

thick turbidite successions from supply dominated shelves during sea level highstand emphasis on the association between relative sea level lowstand and the formation of sandy deep water fans has tended to downplay the significance of high sediment supply and its potential to create deep water fans even during sea level highstands the lance fox hills lewis shelf margin in southern wyoming suggests that high supply was critical in causing the accretion of this moderately wide maastrichtian shelf margin at a minimum rate of 47 8 km m y and the generation of large sand rich fans during every shoreline regression across the shelf it is surprising that fans developed from shelf margin clinoforms that show systematically rising shelf edge trajectories proxy for rising relative sea level as well as from those that show flat trajectories stable to falling relative sea level however the latter producing more sediment bypass resulted in bigger and thicker fans whereas the former produced somewhat smaller and thinner fans we term the former highstand fans and suggest caution in using the lowstand model for high supply systems