the geography of semidiurnal mode 1 internal tide energy loss 1 the semidiurnal mode 1 internal tide receives 0 1 0 3 tw from the surface tide and is capable of propagating across ocean basins the ultimate fate of mode 1 energy after long distance propagation is poorly constrained by existing observations and numerical simulations here global results from a two dimensional semi analytical model indicate that topographic scattering is inefficient at most locations deeper than 2500 m next results from a one dimensional linear model with realistic topography and stratification create a map of mode 1 scattering coefficients along the continental margins on average mode 1 internal tides lose about 60 of their energy upon impacting the continental margins 20 transmits onto the continental shelf 40 scatters to higher modes and 40 reflects back to the ocean interior these analyses indicate that the majority of mode 1 energy is likely lost at large topographic features e g continental slopes seamounts and mid ocean ridges where it may drive elevated turbulent mixing

breaking of internal waves and turbulent dissipation in an anticyclonic mode water eddy abstracta four month glider mission was analyzed to assess turbulent dissipation in an anticyclonic eddy at the western boundary of the subtropical north atlantic the eddy radius 60 km had a c

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

pervasive dolomitization with subsequent hydrothermal alteration in the clarke lake gas field middle devonian slave point formation british columbia canada the clarke lake gas field in british columbia canada is hosted in pervasively dolomitized middle devonian carbonates of the slave point formation the clarke lake field consists mostly of pervasive matrix dolomite and some saddle dolomite the latter varying in volume from about zero in limestones to normally 20 40 locally up to 80 in dolostones over any given 10 m 33 ft core interval some of the saddle dolomite is replacive some is cement and both varieties are associated with dissolution porosity and recrystallized matrix dolomite the major objective of this study is to identify the causes and timing of matrix and saddle dolomite formation specifically whether these dolomites are hydrothermal a comprehensive petrographic and geochemical examination indicates that pervasive matrix dolomitization was accomplished by long distance migration of halite saturated brines during the late devonian to mississippian fluid inclusion homogenization temperatures suggest about 150 uncorrected to 190c corrected at the time of matrix dolomitization these temperatures differ markedly from most published work on the dolomitized devonian reefs in the alberta basin south of the peace river arch where pervasive matrix dolomitization was accomplished by advection of slightly modified seawater at temperatures of about 60 80c and where no hydrothermal influence was ever present the saddle dolomites at clarke lake are not cogenetic with matrix dolomite and are not the product of hydrothermal dolomitization sensu stricto instead they formed through the hydrothermal alteration of matrix dolomite by way of invasion of a gypsum saturated brine during periods of extremely high heat flow and regional plate margin tectonics in the late devonian to mississippian fluid inclusion homogenization temperatures suggest that hydrothermal alteration occurred between 230 uncorrected and 267c corrected which is significantly higher than the maximum temperature of about 190c attained by the slave point formation during burial the sources of the halite and gypsum saturated brines are middle devonian evaporite depositional environments roughly 200 km 124 mi south and or east of clarke lake near the peace river arch

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

deep sea fluid and sediment dynamics influence of hill to seamount scale seafloor topography abstract deep sea sediments play a central role in a wide range of subject areas a number of important controls on the formation of sedimentary deposits have been studied however to date the impact of submarine landscape geometry as a possible control has received comparatively little attention this seems to be particularly true for intermediate scale topographic features such as abyssal hills knolls and seamounts that can be found in many regions of the global seafloor recent estimates suggest that in the deep open oceans away from continental margins there might be as many as 25 106 abyssal hills knolls and seamounts despite this large number very little is known about how they influence environmental complexity and patchiness biogeochemical fluxes and the formation of sedimentary records this paper reviews the currently known types of fluid flow interactions with abyssal hills knolls and seamounts that could potentially influence the way sediments are formed the main types of relevant flow components are quasi steady to eddying background flow internal lee and near inertial waves barotropic and baroclinic tides and seamount trapped waves previous studies looking into systematic links between fluid dynamics and sediments at hills knolls and seamounts are reviewed finally a case study is presented which aims to combine our current knowledge and investigate whether a given combination of recent fluid flow components leaves a detectable imprint in the recent sediments on and around a short seamount the main conclusions and implications are as follows 1 topographically generated flow field geometries that are composed of a number of different prevailing fluid flow components can be reflected and detected in properties of the underlying sediments 2 tidal and other higher frequency lee wave near inertial components of deep ocean currents can be essential for locally driving total current velocities across threshold values for non deposition erosion resuspension of freshly deposited deep sea sediments moreover there is evidence suggesting that not only maximum current speeds but also intensities of higher frequency tidal and or near inertial current direction variability might control sediment dynamics and sediment formation this relativises the view that current speed is the main or even only controlling factor for sediment dynamics and sediment formation 3 when it comes to the reconstruction of paleo flows these findings imply that certain sedimentary records may well reveal more about variability in the higher frequency flow components than about variability in the basin scale net flow component that often is the focus of paleoceanographic studies 4 single core paleo records from hill seamount or similarly controlled sediment deposits may be biased due to the asymmetry of flow fields around these topographic features to arrive at unbiased paleo records for non fluid dynamic parameters the influence of the flow field geometry would have to be removed from the record first 5 it seems the mechanistic understanding of hill and seamount related flow topography interactions and their links to sediment dynamics is approaching a level that may a facilitate improved interpretation of topographically controlled sedimentary paleo records b help fill in the knowledge gap that exists for functional deep sea biodiversity at intermediate space scales and c improve predictive capabilities for exploration of economically relevant iron manganese fe mn crusts on seamounts

redistribution of energy available for ocean mixing by long range propagation of internal waves ocean mixing which affects pollutant dispersal marine productivity and global climate1 largely results from the breaking of internal gravity waves disturbances propagating along the ocean s internal stratification a global map of internal wave dissipation would be useful in improving climate models but would require knowledge of the sources of internal gravity waves and their propagation towards this goal i present here computations of horizontal internal wave propagation from 60 historical moorings and relate them to the source terms of internal waves as computed previously2 3 analysis of the two most energetic frequency ranges near inertial frequencies and semidiurnal tidal frequencies reveals that the fluxes in both frequency bands are of the order of 1 kw m 1 that is 15 50 of the energy input and are directed away from their respective source regions however the energy flux due to near inertial waves is stronger in winter whereas the tidal fluxes are uniform throughout the year both varieties of internal waves can thus significantly affect the space time distribution of energy available for global mixing

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

climatic impacts of parameterized local and remote tidal mixing abstractturbulent mixing driven by breaking internal tides plays a primary role in the meridional overturning and oceanic heat budget most current climate models explicitly parameterize only the local dissipation of internal tides at the generation sites representing the remote dissipation of low mode internal tides that propagate away through a uniform background diffusivity in this study a simple energetically consistent parameterization of the low mode internal tide dissipation is derived and implemented in the geophysical fluid dynamics laboratory earth system model with gold component gfdl esm2g the impact of remote and local internal tide dissipation on the ocean state is examined using a series of simulations with the same total amount of energy input for mixing but with different scalings of the vertical profile of dissipation with the stratification and with different idealized scenarios for the distribution of the low mode internal tide energy dissipation uniformly over ocean basins co

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

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

scattering of internal tides by irregular bathymetry of large extent we present an analytical theory of scattering of tide generated internal gravity waves in a continuously stratified ocean with a randomly rough seabed based on a linearized approximation the idealized case of constant mean sea depth and brunt vaisala frequency is considered the depth fluctuation is assumed to be a stationary random function of space characterized by small amplitude and a correlation length comparable to the typical wavelength for both one and two dimensional topographies the effects of scattering on the wave phase over long distances are derived explicitly by the method of multiple scales for one dimensional topography numerical results are compared with buhler holmes cerfon j fluid mech vol 678 2011 pp 271 293 computed by the method of characteristics for two dimensional topography new results are presented for both statistically isotropic and anisotropic cases

internal tide generation by arbitrary two dimensional topography to date analytical models of internal tide generation by two dimensional ridges have considered only idealized shapes here we advance the green function approach to address the generation of internal tides by two dimensional topography of arbitrary shape employing the wentzel kramers brillouin wkb approximation to consider the impact of non uniform stratifications this allows for a more accurate analytical estimation of tidal conversion rates studies of single and double ridges reveal that the conversion rate and the nature of the radiated internal tide can be sensitive to the topographic shape particularly around criticality and when there is interference between wave fields generated by neighbouring ridges the method is then applied to the study of two important internal tide generation sites the hawaiian and luzon ridges where it captures key features of the generation process

decay of an internal tide due to random topography in the ocean we present a theoretical and numerical study of the decay of an internal wave caused by scattering at undulating sea floor topography with an eye towards building a simple model in which the decay of internal tides in the ocean can be estimated as is well known the interactions of internal waves with irregular boundary shapes lead to a mathematically ill posed problem so care needs to be taken to extract meaningful information from this problem here we restrict the problem to two spatial dimensions and build a numerical tool that combines a real space computation based on the characteristics of the underlying partial differential equation with a spectral computation that satisfies the relevant radiation conditions our tool works for finite amplitude topography but is restricted to subcritical topography slopes detailed results are presented for the decay of the gravest vertical internal wave mode as it encounters finite stretches of either sinusoidal topography or random topography defined as a gaussian random process with a simple power spectrum a number of scaling laws are identified and a simple expression for the decay rate in terms of the power spectrum is given finally the resulting formulae are applied to an idealized model of sea floor topography in the ocean which seems to indicate that this scattering process can provide a rapid decay mechanism for internal tides however the present results are restricted to linear fluid dynamics in two spatial dimensions and to uniform stratification which restricts their direct application to the real ocean

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

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

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

tidal conversion at a submarine ridge the radiative flux of internal wave energy the tidal conversion powered by the oscillating flow of a uniformly stratified fluid over a two dimensional submarine ridge is computed using an integral equation method the problem is characterized by two nondimensional parameters a and b the first parameter a is the ridge half width scaled by h where h is the uniform depth of the ocean far from the ridge and is the inverse slope of internal tidal rays horizontal run over vertical rise the second parameter b i s the ridge height scaled by h two topographic profiles are considered a triangular or tent shaped ridge and a polynomial ridge with continuous topographic slope for both profiles complete coverage of the a b parameter space is obtained by reducing the problem to an integral equation which is then discretized and solved numerically it is shown that in the supercritical regime ray slopes steeper than topographic slopes the radiated power increases monotonically with b and decreases monotonically with a in the subcritical regime the radiated power has a complicated and nonmonotonic dependence on these parameters as a 0 recent results are recovered for the tidal conversion produced by a knife edge barrier it is shown analytically that the a 0 limit is regular if a 1 the reduction in tidal conversion below that at a 0 is proportional to a 2 further the knife edge model is shown to be indicative of both conversion rates and the structure of the radiated wave field over a broad region of the supercritical parameter space as a increases the topographic slopes become gentler and at a certain value of a the ridge becomes critical that is there is a single point on the flanks at which the topographic slope is equal to the slope of an internal tidal beam the conversion decreases continuously as a increases through this transition visualization of the disturbed buoyancy field shows prominent singular lines tidal beams in the case of a triangular ridge these beams originate at the crest of the triangle in the case of a supercritical polynomial ridge the beams originate at the shallowest point on the flank at which the topographic slope equals the ray slope

saturation of the internal tides and induced mixing in the abyssal ocean as part of an ongoing effort to develop a parameterization of wave induced abyssal mixing the authors derive an heuristic model for nonlinear wave breaking and energy dissipation associated with internal tides then the saturation and dissipation of internal tides for idealized and observed topography samples are investigated one of the main results is that the wave induced mixing could be more intense and more confined to the bottom than previously assumed in numerical models furthermore in this model wave breaking and mixing clearly depend on the small scales of the topography below 10 km or so which is below the current resolution of global bathymetry this motivates the use of a statistical approach to represent the unresolved topography when addressing the role of internal tides in mixing the deep ocean

instability and focusing of internal tides in the deep ocean received 18 december 2006 and in revised form 7 april 2007 the interaction of tidal currents with sea floor topography results in the radiation of internal gravity waves into the ocean interior these waves are called internal tides and their dissipation due to nonlinear wave breaking and concomitant threedimensional turbulence could play an important role in the mixing of the abyssal ocean and hence in controlling the large scale ocean circulation as part of on going work aimed at providing a theory for the vertical distribution of wave breaking over sea floor topography in this paper we investigate the instability of internal tides in a very simple linear model that helps us to relate the formation of unstable regions to simple features in the sea floor topography for two dimensional tides over one dimensional topography we find that the formation of overturning instabilities is closely linked to the singularities in the topography shape and that it is possible to have stable waves at the sea floor and unstable waves in the ocean interior above for three dimensional tides over two dimensional topography there is in addition an effect of geometric focusing of wave energy into localized regions of high wave amplitude and we investigate this focusing effect in simple examples overall we find that the distribution of unstable wave breaking regions can be highly non uniform even for very simple idealized topography shapes

interaction of superinertial waves with submesoscale cyclonic filaments in the north wall of the gulf stream abstracthigh resolution nearly lagrangian observations of velocity and density made in the north wall of the gulf stream reveal banded shear structures characteristic of near inertial waves niws here the current follows submesoscale dynamics with rossby and richardson numbers near one and the vertical vorticity is positive this allows for a unique analysis of the interaction of niws with a submesoscale current dominated by cyclonic as opposed to anticyclonic vorticity rotary spectra reveal that the vertical shear vector rotates primarily clockwise with depth and with time at frequencies near and above the local coriolis frequency f at some depths more than half of the measured shear variance is explained by clockwise rotary motions with frequencies between f and 1 7f the dominant superinertial frequencies are consistent with those inferred from a dispersion relation for niws in submesoscale currents that depends on the observed aspect ratio of the wave shear as well as the vertical vorticity

scattering of internal waves at finite topography in two dimensions part i theory and case studies abstract the scattering of internal gravity waves at finite topography in two dimensions is studied theoretically and numerically for a finite depth ocean a formal solution is derived using a mapping function based on ray tracing the solution satisfies radiation conditions energy is conserved the incoming energy flux is redistributed in physical and modenumber space numerical solutions are calculated for a single plane wave propagating from the ocean side onto slope shelf configurations where a flat shallow shelf is connected to a flat deep ocean by linear slopes staircases convex or concave parabolic profiles and half cosine slopes the fraction of the incoming energy flux transmitted onto the shelf and reflected back to the deep ocean and the distribution of these fluxes in modenumber space are calculated the results depend on the parameters of the incident wave and of the topography especially important is the distinction between supercritical topography where the slope of the topography exc

internal tides and ocean mixing recent satellite and in situ observations have shown that at ocean ridges and other seafloor topographic features a substantial amount of energy is transferred from the main ocean tides into internal tides in his perspective garrett explains how these internal waves with tidal periods propagate through the density stratified deep ocean and eventually break down into turbulence the resulting mixing affects ocean stratification and ocean circulation it thus influences climate as well as biological production the energy for the internal tides is derived from the rotational energy of the earth moon system changes of the length of the day and the distance to the moon

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

the role of internal tides in mixing the deep ocean abstract internal wave theory is used to examine the generation radiation and energy dissipation of internal tides in the deep ocean estimates of vertical energy flux based on a previously developed model are adjusted to account for the influence of finite depth varying stratification and two dimensional topography specific estimates of energy flux are made for midocean ridge topography weakly nonlinear theory is applied to the wave generation at idealized topography to examine finite amplitude corrections to the linear theory most internal tide energy is generated at low modes associated with spatial scales from roughly 20 to 100 km the richardson number of the radiated internal tide typically exceeds unity for these motions and so direct shear instability of the generated waves is not the dominant energy transfer mechanism it also seems that wave wave interactions are ineffective at transferring energy from the large wavelengths that dominate the energy flux instead it appears that most of

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

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography application to the southern ocean abstract recent estimates from observations and inverse models indicate that turbulent mixing associated with internal wave breaking is enhanced above rough topography in the southern ocean in most regions of the ocean abyssal mixing has been primarily associated with radiation and breaking of internal tides in this study it is shown that abyssal mixing in the southern ocean can be sustained by internal waves generated by geostrophic motions that dominate abyssal flows in this region theory and fully nonlinear numerical simulations are used to estimate the internal wave radiation and dissipation from lowered acoustic doppler current profiler ladcp ctd and topography data from two regions in the southern ocean drake passage and the southeast pacific the results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation previously inferred from finescale measurements in the region suggesting that it is one of the

tidal conversion by supercritical topography calculations are presented of the rate of energy conversion of the barotropic tide into internal gravity waves above topography on the ocean floor the ocean is treated as infinitely deep and the topography consists of periodic obstructions a green function method is used to construct the scattered wavefield the calculations extend the previous results of balmforth et al for subcritical topography wherein waves propagate along rays whose slopes exceed that of the topography everywhere by allowing the obstacles to be arbitrarily steep or supercritical so waves propagate at shallower angles than the topographic slopes and are scattered both up and down a complicated pattern is found for the dependence of energy conversion on e the ratio of maximum topographic slope to wave slope and the ratio of obstacle amplitude and separation this results from a sequence of constructive and destructive interferences between scattered waves that has implications for computing tidal conversion rates for the global ocean

global observations of open ocean mode 1 m2internal tides abstracta global map of open ocean mode 1 m2 internal tides is constructed using sea surface height ssh measurements from multiple satellite altimeters during 1992 2012 representing a 20 yr coherent internal tide field a two dimensional plane wave fit method is employed to 1 suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence and 2 separately resolve multiple internal tidal waves global maps of amplitude phase energy and flux of mode 1 m2 internal tides are presented the m2 internal tides are mainly generated over topographic features including continental slopes midocean ridges and seamounts internal tidal beams of 100 300 km width are observed to propagate hundreds to thousands of kilometers multiwave interference of some degree is widespread because of the m2 internal tide s numerous generation sites and long range propagation the m2 internal tide propagates across the critical latitudes for parametric subharmonic instability 28 8 s n

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

abyssal ocean overturning shaped by seafloor distribution the abyssal ocean is broadly characterized by northward flow of the densest waters and southward flow of less dense waters above them understanding what controls the strength and structure of these interhemispheric flows referred to as the abyssal overturning circulation is key to quantifying the ocean s ability to store carbon and heat on timescales exceeding a century here we show that north of 32 s the depth distribution of the seafloor compels dense southern origin waters to flow northward below a depth of about 4 kilometres and to return southward predominantly at depths greater than 2 5 kilometres unless ventilated from the north the overlying mid depths 1 to 2 5 kilometres deep host comparatively weak mean meridional flow backed by analysis of historical radiocarbon measurements the findings imply that the geometry of the pacific indian and atlantic basins places a major external constraint on the overturning structure

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

long range propagation of the semidiurnal internal tide from the hawaiian ridge abstract the northeastward progression of the semidiurnal internal tide from french frigate shoals ffs hawaii is studied with an array of six simultaneous profiling moorings spanning 25 5 37 1 n 1400 km and 13 yr long ocean topography experiment topex poseidon t p altimeter data processed by a new technique the moorings have excellent temporal and vertical resolutions while the altimeter offers broad spatial coverage of the surface manifestation of the internal tide s coherent portion together these two approaches provide a unique view of the internal tide s long range propagation in a complex ocean environment the moored observations reveal a rich time variable and multimodal internal tide field with higher mode motions contributing significantly to velocity displacement and energy in spite of these contributions the coherent mode 1 internal tide dominates the northeastward energy flux and is detectable in both moored and altimetric data over the entire array phase and group prop

topographic scattering of the low mode internal tide in the deep ocean we investigate the role of deep ocean topography in scattering energy from the large spatial scales of the low mode internal tide to the smaller spatial scales of higher modes the complete green function method which is not subject to the restrictions of the wkb approximation is used for the first time to study the two dimensional scattering of a mode 1 internal tide incident on subcritical and supercritical topography of any form in arbitrary stratifications for an isolated gaussian ridge in a uniform stratification large amplitude critical topography is the most efficient at mode 1 scattering and small amplitude topography scatters with an efficiency on the order of 5 10 in a nonuniform stratification with a pycnocline the results are qualitatively the same as for a constant stratification albeit with the key features shifted to larger height ratios having validated these results by direct comparison with the results of nonlinear numerical simulations and in the process demonstrated that wkb results are not appropriate for reasonable ocean predictions we proceed to use the green function approach to quantify the role of topographic scattering for the region of the pacific ocean surrounding the hawaiian islands chain to the south the line islands ridge is found to scatter 40 of a mode 1 internal tide coming from the hawaiian ridge to the north realistic small amplitude rough topography scatters 5 10 of the energy out of mode 1 for transects of length 1000 3000 km a significant finding is that compared to large extents of small amplitude rough topography a single large topographic feature along the path of a mode 1 internal tide plays the dominant role in scattering the internal tide

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

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

structure propagation and mixing of energetic baroclinic tides in mamala bay oahu hawaii abstract large semidiurnal vertical displacements 100 m and strong baroclinic currents 0 5 m s 1 several times as large as barotropic currents dominate motions in mamala bay outside the mouth of pearl harbor hawaii during september 2002 the authors sought to characterize them with a 2 month mclane moored profiler deployment and a 4 day intensive survey with a towed ctd adcp and the research vessel r v revelle hydrographic sonar spatial maps and time series of turbulent dissipation rate diapycnal diffusivity k isopycnal displacement velocity u energy e and energy flux f are presented dissipation rate peaks in the lower 150 m during rising isopycnals and high strain and shows a factor of 50 spring neap modulation the largest k values in the western bay near a submarine ridge exceed 10 3 m2 s 1 the m2 phases of and u increase toward the west implying a westward phase velocity cp 1 m s 1 and horizontal wavelength 60 km consistent with theoretical mode 1 values these phase

evidence for enhanced mixing over rough topography in the abyssal ocean the overturning circulation of the ocean plays an important role in modulating the earth s climate but whereas the mechanisms for the vertical transport of water into the deep ocean deep water formation at high latitudes and horizontal transport in ocean currents have been largely identified it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise however measurements of the internal wave field the main source of energy for mixing and of turbulent dissipation rates have typically implied diffusivities across surfaces of equal density of only approximately 0 1 cm2 s 1 too small to account for the return flow here we report measurements of tracer dispersion and turbulent energy dissipation in the brazil basin that reveal diffusivities of 2 4 cm2 s 1 at a depth of 500 m above abyssal hills on the flank of the mid atlantic ridge and approximately 10 cm2 s 1 nearer the bottom this amount of mixing probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry may be large enough to close the buoyancy budget for the brazil basin and suggests a mechanism for closing the global overturning circulation

global mapping of diapycnal diffusivity in the deep ocean based on the results of expendable current profiler xcp surveys 1 based on the results of the extensive xcp surveys in the north pacific we first examine the empirical relationship between the estimated diapycnal diffusivity in the thermocline and the numerically predicted available energy density of the semidiurnal internal tide major energy source for diapycnal diffusivity at each location the diapycnal diffusivity is estimated by applying the parameterization of gregg 1989 to the fine scale vertical shear of horizontal velocity measured by xcp next the numerically predicted energy density of the semidiurnal internal tide at each longitude and latitude in the world s oceans is incorporated into the resulting empirical relationship to obtain the global distribution of diapycnal diffusivity in the thermocline this model predicts that strong diapycnal mixing mixing hotspot is limited to the prominent topographic features at latitudes between 20 and 30

generation of internal waves in the deep ocean by tides 1 a direct computation of the tidal generation of internal waves over the global ocean is presented it is based on linear wave theory and high resolution data for the bottom topography the geographical distribution of the energy flux from tides to internal waves is determined with a spatial resolution of a few kilometers the total flux over the area with a depth greater than 500 m is found to be 1 2 tw the greatest uncertainties of the computation are due to unresolved topography and to nonlinear effects caused by supercritical bottom slope

sensitivity of internal wave energy distribution over seabed corrugations to adjacent seabed features here we show that the distribution of energy of internal gravity waves over a patch of seabed corrugations strongly depends on the distance of the patch to adjacent seafloor features located downstream of the patch specifically we consider the steady state energy distribution due to an incident internal wave arriving at a patch of seabed ripples neighbouring i another patch of ripples i e a second patch and ii a vertical wall seabed undulations with dominant wavenumber twice as large as overpassing internal waves reflect back part of the energy of the incident internal waves bragg reflection and allow the rest of the energy to transmit downstream in the presence of a neighbouring topography on the downstream side the transmitted energy from the patch may reflect back partially if the downstream topography is another set of seabed ripples or fully if it is a vertical wall the reflected wave from the downstream topography is again reflected back by the patch of ripples through the same mechanism this consecutive reflection goes on indefinitely leading to a complex interaction pattern including constructive and destructive interference of multiply reflected waves as well as an interplay between higher mode internal waves resonated over the topography we show here that when steady state is reached both the qualitative and quantitative behaviour of the energy distribution over the patch is a strong function of the distance between the patch and the downstream topography it can increase or decrease exponentially fast along the patch or stay nearly unchanged as a result for instance the local energy density in the water column can become an order of magnitude larger in certain areas merely based on where the downstream topography is this may result in the formation of steep waves in specific areas of the ocean leading to breaking and enhanced mixing at a particular distance the wall or the second patch may also result in a complete disappearance of the trace of the seabed undulations on the upstream and the downstream wave field

satellite investigation of the m2 internal tide in the tasman sea abstractthe m2 internal tide in the tasman sea is investigated using sea surface height measurements made by multiple altimeter missions from 1992 to 2012 internal tidal waves are extracted by two

a coupled model for laplace s tidal equations in a fluid with one horizontal dimension and variable depth abstracttide topography interactions dominate the transfer of tidal energy from large to small scales at present it is poorly understood how low mode internal tides reflect and scatter along the continental margins here the coupling equations for linear tides model celt are derived to determine the independent modal solutions to laplace s tidal equations lte over stepwise topography in one horizontal dimension celt is i applicable to arbitrary one dimensional topography and realistic stratification without requiring numerically expensive simulations and ii formulated to quantify scattering because it implicitly separates incident and reflected waves energy fluxes and horizontal velocities obtained using celt are shown to converge to analytical solutions indicating that flat bottom modes which evolve according to lte are also relevant in describing tides over sloping topography the theoretical framework presented can then be used to quantify simultaneous incident and reflected energy fl

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

stochastic modeling of seafloor morphology inversion of sea beam data for second order statistics at scale lengths less than 100 km or so statistical descriptions of seafloor morphology can be usefully employed to characterize ridge crest processes off ridge tectonics and vulcanism sedimentation and postdepositional transport we seek to develop methods for the estimation of seafloor statistics that take into account the finite precision resolution and sampling obtained by actual echo sounding systems in this initial paper we restrict our attention to the problem of recovering second order statistics from data sets collected by multibeam devices such as sea beam the seafloor is modeled as a stationary zero mean gaussian random field completely specified by its two point covariance function we introduce an anisotropic two point covariance function that has five free parameters describing the amplitude orientation characteristic wave numbers and hausdorff fractal dimension of seafloor topography we formulate the general forward problem relating this model to the statistics of an ideal multibeam echo sounder in particular the along track autocovariance functions of individual beams and the cross covariance functions between beams of arbitrary separation using these second moments as data functionals we then pose the inverse problem of estimating the seafloor parameters from realistic noisy data sets with finite sampling and beamwidth and we solve this inverse problem by an iterative linearized least squares method the inversion method is applied to sea beam transit data from both the pacific and atlantic oceans sea beam system noise stands out as a sharp spike on the along track autocovariance function and can be modeled as a white noise process whose amplitude generally increases with beam angle the five parameters in our second order model can be estimated from the inversion of data sets comprising 100 200 km of track length in general the cross track wave number is the most poorly determined although uncertainties in the assumed sea beam response may bias the values of the fractal dimension using the assumed beamwidth the measured noise values and the seafloor parameters recovered from the inversion we generate sea beam synthetics whose statistical character can be directly compared with raw sea beam data for most of the track segments we have processed thus far the synthetics are similar to the data in the case of one atlantic profile however the comparison clearly indicates the necessity of incorporating higher order statistics the space domain procedures described in this paper can be extended for this purpose

coupled fluid flow heat and mass transport and erosion in the alberta basin implications for the origin of the athabasca oil sands regional topography driven flow systems related to laramide tectonic rebound were simulated using two dimensional coupled fluid flow heat transport and solute transport numerical models to replicate present formation water salinity and temperature distributions and investigate the accumulation of the athabasca oil sands previous modelling of this system was replicated and it predicted repeated replacement of all basin formation water with freshwater during deposition of the oil sands due to high permeabilities to match present alberta basin temperature and salinity distributions model hydrostratigraphy permeabilities and heat fluxes were adjusted this revised model conducts fluids along the mannville aquifer rather than the upper devonian aquifer and replicates present salinity distributions assuming instantaneous uplift around 60 ma fluid fluxes in principal aquifers decrease by two orders of magnitude using new permeabilities resulting in primarily conductive heat transport thus genesis

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

nonreflecting internal wave beam propagation in the deep ocean using linear internal wave theory for an ocean stratified by both density and current several background profiles are identified for which internal wave beams can propagate without any internal reflection these special profiles are favorably compared with available oceanic data

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

standing internal tides in the tasman sea observed by gliders abstractlow mode internal tides are generated at tall submarine ridges propagate across the open ocean with little attenuation and reach distant continental slopes a semidiurnal internal tide beam identified in previous altimetric observations and modeling emanates from the macquarie ridge crosses the tasman sea and impinges on the tasmanian slope spatial surveys covering within 150 km of the slope by two autonomous underwater gliders with maximum profile depths of 500 and 1000 m show the steepest slope near 43 s reflects almost all of the incident energy flux to form a standing wave starting from the slope and moving offshore by one wavelength 150 km potential energy density displays an antinode node antinode node structure while kinetic energy density shows the opposite mission mean mode 1 incident and reflected flux magnitudes are distinguished by treating each glider s survey as an internal wave antenna for measuring amplitude wavelength and direction incident fluxes are 1 4 and 2 3 k

topographies lacking tidal conversion the consensus is that in a stratified sea a classical model of tidal flow over irregular but smooth topography necessarily leads to the generation of internal tides regardless of the shape of the topography this is referred to as tidal conversion here it is shown however that there exists a large class of topographies for which there is neither tidal conversion nor any scattering of incident internal waves this result is obtained in a uniformly stratified rigid lid sea using a barotropic tide that owing to its large horizontal scale is supposed to be simply a mass conserving periodic back and forth flow the baroclinic response at the tidal frequency is upon non dimensionalizing and stretching of coordinates determined by a standard hyperbolic boundary value problem bvp we here solve this hyperbolic bvp by mapping a domain of complicated yet a priori unknown shape onto a uniform depth channel for which the same hyperbolic problem is known to display neither conversion of the barotropic tide nor scattering of internal wave modes the map achieving this is required to satisfy hyperbolic cauchy riemann equations defined as analogues of the cauchy riemann equations that are used in solving elliptic problems mapping the rigid lid surface in the original cartesian frame onto a rigid lid surface in the transformed frame this map is solved in terms of one arbitrary function each particular function defines a new topographic shape that can be computed a posteriori the map is unique provided the jacobian of transformation does not vanish which is guaranteed for subcritical bottom topography whose slope is everywhere less than that of the characteristics for topographies that can thus be mapped onto a channel tidal conversion and scattering are absent examples discussed include the classical wedge a near gaussian ridge a continental slope and near sinusoidal topographies

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