simple shear testing of sensitive very soft offshore clay for wide strain range stiffness and damping properties of sensitive very soft clay sediments of the italian adriatic continental shelf are determined by means of two series of cyclic simple shear tests one with 12 stages and one with two stages the apparatus used in this research is capable of investigating the stress strain behaviour of the soil in a wide range of shear strains from about 0 0004 to 1 test results were expressed in terms of small strain shear modulus g0 normalized equivalent shear modulus geq g0 and damping ratio d versus cyclic shear strain amplitude c these parameters were analyzed in the framework of existing literature by comparison with empirical correlations developed for onshore materials of different plasticity and limited to g0 also for soft soils the dependence of g0 geq g0 c and d c on factors such as void ratio stress history and loading cycles is analyzed and discussed

observations of the internal tide in monterey canyon abstract data from two shipboard experiments in 1994 designed to observe the semidiurnal internal tide in monterey canyon reveal semidiurnal currents of about 20 cm s 1 which is an order of magnitude larger than the estimated barotropic tidal currents the kinetic and potential energy evidenced by isopycnal displacements of about 50 m was greatest along paths following the characteristics calculated from linear theory these energy ray paths are oriented nearly parallel to the canyon floor and may originate from large bathymetric features beyond the mouth of monterey bay energy propagated shoreward during the april experiment itex1 whereas a standing wave that is an internal seiche was observed in october itex2 the difference is attributed to changes in stratification between the two experiments higher energy levels were present during itex1 which took place near the spring phase of the fortnightly 14 8 days cycle in sea level while itex2 occurred close to the neap phase further evide

consolidation characteristics of sediments from the peru chile continental margin and implications for past sediment instability abstract one dimensional consolidation tests were performed on eight near surface samples 0 5 to 3 5 m from the peru chile continental margin these tests show that the consolidation behavior of these deposits is strongly influenced by the presence of high concentrations of organic matter resulting from the occurrence of coastal upwelling along this margin of south america organic carbon concentrations as high as 12 are found in samples from an upper slope mud lens between 10 5 to 13 6 s that lies beneath an area of intense upwelling with increasing organic content both the compressibility and rate of secondary compression are found to increase the increase in void ratio with increasing organic content and the ease by which organic matter is deformed appear responsible for these trends outside the mud lens the compressibility also increases as a result of increasing concentrations of clay size material and the abundance of smectite and illite all of the sediments along the margin behave as if they were consolidated under a pressure greater than the present effective overburden pressure evidence of erosion as a cause of the overconsolidation is present only on the upper slope mud lens at 13 6 s where 14 c dating verifies the erosion of 3 5 to 7 m of sediment numerous unconformities and intervals of deformed bedding in a core from 13 6 s attest to the past instability of sediments at this site at the other locations along the margin the increase in the overconsolidation ratio with increasing organic carbon content suggests that the bonding of sediment particles by organic matter may be responsible for the apparent overconsolidation low sedimentation rates on the slope off northern chile may also be a contributing factor to the apparent overconsolidation of sediments in this area

late quaternary morpho sedimentology and submarine mass movements of the betsiamites area lower st lawrence estuary quebec canada abstract a complex submarine geomorphology was revealed from multibeam bathymetry and seismic reflection surveys conducted between 2001 and 2007 in the lower st lawrence estuary offshore betsiamites river quebec canada in this paper we describe the submarine morpho sedimentology of an area of 500 km 2 with focus on the consequences of four mass movement events the general morpho sedimentology of the area and submarine features resulting from mass movement processes channel erosion and gas seepage are described a spatio temporal sequence for the occurrence of the mass movements and a chronology for the failures are established we propose dates for four of the observed mass movement deposits a buried paraglacial debris flow deposit is dated as older than 9280 cal bp whereas a major landslide scar characterized by two topographic depressions on the shelf and a sediment lobe in the laurentian channel were dated around 7250 cal bp morphological observations and sediment core analyses allow us to identify a least two different recent i e less than 500 yr old debris flow accumulations associated with two recent earthquakes 1 the ad 1663 m 7 and 2 ad 1860 m 6 or ad 1870 m 6 5 earthquakes in addition to a complex geomorphology influenced by mass movements we have identified several regions on the shelf and on the laurentian channel with evidence of pockmarks which could potentially influence submarine slope stability in the estuary

observations of overturning in the thermocline the context of ocean mixing abstract the time sequence of events that lead to internal wave breaking and ocean turbulence is investigated data are obtained from depths 100 400 m with a repeat profiling ctd and a coded pulse doppler sonar the instruments were deployed from r p flip during february march 1995 while stationed 30 km west of point arguello california as an aspect of the marine boundary layer experiment although the water depth at the site is 1500 m both rms shear and diapycnal diffusivity as inferred from the average rate and size of overturning events increase with depth below 250 m a deep source of wave energy is implied depth time series of 6 4 m shear s 2 m strain n2 n2 where n is the buoyancy frequency 6 4 m gradient richardson number ri n2 s2 and 2 m effective strain rate the depth derivative of ctd inferred vertical velocity are obtained at 4 minute intervals over a 9 day 100 400 m domain the occurrence of overturns static instabilities of vertical scale 2 m in the observed density

dynamics of advection driven upwelling over a shelf break submarine canyon 1 the response over a submarine canyon to a several day upwelling event can be separated into three phases an initial transient response a later much longer steady advection driven response and a final relaxation phase for the advection driven phase over realistically steep deep and narrow canyons with near uniform flow and stratification at rim depth we have derived scale estimates for four key quantities observations from 5 real world canyon studies and 3 laboratory studies are used to validate the scaling and estimate the scalar constant for each scale based on 4 geometric parameters of the canyon the background stratification the coriolis parameter and the incoming current we can estimate 1 the depth of upwelling in the canyon to within 15 m 2 the deep vorticity to within 15 and 3 the presence absence of a rim depth eddy can be determined based on laboratory data 4 the total upwelling flux can also be estimated the scaling analysis shows the importance of a rossby number based on the radius of curvature of isobaths at the upstream mouth of the canyon this rossby number determines the ability of the flow to cross the canyon isobaths and generate the pressure gradient that drives upwelling in the canyon other important scales are a rossby number based on the length of the canyon which measures the ability of the flow to lift isopycnals and a burger number based on the width of the canyon that determines the likelihood of an eddy at rim depth generally long canyons with sharply turning upstream isobaths strong incoming flow small coriolis parameter and weak stratification have the strongest upwelling response

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

mineralogy chemistry and physical properties interrelationships of some sensitive clays from eastern canada this paper describes the use of quantitative mineralogy and specific surface area in interpreting the index properties of clayey soils from nine sites in eastern canada samples representative of t

early diagenetic processes in coastal marine sediments disturbed by a catastrophic sedimentation event abstract following a catastrophic flash flood in july 1996 as much as 50 cm of post glacial clays were deposited in less than 2 days in the upper reaches of the saguenay fjord quebec canada disrupting the normal sedimentation and diagenetic regimes we report detailed geochemical analyses of sediments porosity eh organic and inorganic carbon fe and mn reactive solid phases and acid volatile sulfide and porewaters salinity dissolved organic carbon doc fe ii mn ii nitrate ammonium and sulfate for seven stations located in the saguenay fjord three of these sag 05 sag 09 and sag 30 were visited in 1996 and once per year thereafter to document the chemical evolution of the sediment toward a new steady state the flood deposits contain less organic carbon and more inorganic carbon than the indigenous fjord sediments the flood deposit modified the distribution patterns of reactive mn and fe as a result of the reduction of mn and fe oxides delivered with the deposit and those concentrated at the now buried former sediment water interface most of the mn ii migrated to the new sediment water interface where a mn rich layer was formed in contrast much of the fe ii was precipitated as sulfides and remained trapped at or close to the old interface a nitrate peak developed in the porewater at the old sediment water interface possibly because of the oxidation of ammonia by mn oxides the distributions of porewater doc within the flood deposit correlate with the distributions of dissolved mn ii and fe ii suggesting that adsorbed doc was released when metal oxides were reduced

tidally forced internal waves and overturns observed on a slope results from home abstract tidal mixing over a slope was explored using moored time series observations on kaena ridge extending northwest from oahu hawaii during the survey component of the hawaii ocean mixing experiment home a mooring was instrumented to sample the velocity and density field of the lower 500 m of the water column to look for indirect evidence of tidally induced mixing and was deployed on a slope in 1453 m water depth for 2 months beginning in november 2000 the semidiurnal barotropic tidal currents at this site have a significant cross ridge component favorable for exciting an internal tidal response a large amplitude response is expected given that the slope of the topography 4 5 is nearly the same as the slope of the internal wave group velocity at semidiurnal frequency density overturns were inferred from temperature profiles measured every 2 min the number and strength of the overturns are greater in the 200 m nearest the bottom with overturns exceeding 24 m present at any depth nearly

intense variable mixing near the head of monterey submarine canyon abstract a microstructure survey near the head of monterey submarine canyon the first in a canyon confirmed earlier inferences that coastal submarine canyons are sites of intense mixing the data collected during two weeks in august 1997 showed turbulent kinetic energy dissipation and diapycnal diffusivity up to 103 times higher than in the open ocean dissipation and diapycnal diffusivity within 10 km of the canyon head were among the highest observed anywhere e 1 1 10 6 w kg 1 k 1 0 10 2 m2 s 1 mixing occurred mainly in an on axis stratified turbulent layer with thickness and intensity increasing from neap to spring tide strain spectra showed a gentler than k 1z rolloff suggesting that critical reflection and scattering may push energy into high wavenumbers dissipation dependence on shear appears to be much weaker in the canyon than in the open ocean with indications that the dependence maybe as low as e s coastal canyons may account for a small but significant fraction of the int

structure of the baroclinic tide generated at kaena ridge hawaii repeat transects of full depth density and velocity are used to quantify generation and radiation of the semidiurnal internal tide from kaena ridge hawaii a 20 km long transect was sampled every 3 h using expendable current profilers and the absolute velocity profiler phase and amplitude of the baroclinic velocity pressure and vertical displacement were computed as was the energy flux large barotropically induced isopycnal heaving and strong baroclinic energy flux divergence are observed on the steep flanks of the ridge where upward and downward beams radiate off ridge directly above kaena ridge strong kinetic energy density and weak net energy flux are argued to be a horizontally standing wave the phasing of velocity and vertical displacements is consistent with this interpretation results compare favorably with the merrifield and holloway model

internal tides and mixing in a submarine canyon with time varying stratification abstractthe time variability of the energetics and turbulent dissipation of internal tides in the upper monterey submarine canyon msc is examined with three moored profilers and five adcp moorings spanning february april 2009 highly resolved time series of velocity energy and energy flux are all dominated by the semidiurnal internal tide and show pronounced spring neap cycles however the onset of springtime upwelling winds significantly alters the stratification during the record causing the thermocline depth to shoal from about 100 to 40 m the time variable stratification must be accounted for because it significantly affects the energy energy flux the vertical modal structures and the energy distribution among the modes the internal tide changes from a partly horizontally standing wave to a more freely propagating wave when the thermocline shoals suggesting more reflection from up canyon early in the observational record turbulence computed from thorpe scales is greatest in the bottom 5

evaluation of disturbance induced on soft offshore sediments by two types of gravity piston coring techniques abstract sample disturbance is still a key issue in offshore investigations especially when logistic and financial limitations do not allow the use of drilling equipment this paper focuses on the comparison between the disturbance induced by a conventional free fall piston corer ff and a modified piston corer ad equipped with a velocity control angel descent method twin core samples were retrieved in two successions of pelitic sediments with a prevailing non clayey fraction and a non negligible sandy fraction comparison was based on different acquisition physical and mechanical parameters ranging from accelerometer data to magnetic susceptibility logs and geotechnical parameters from laboratory investigations including oedometer compression tests and cyclic simple shear tests accelerometer data highlighted the sharp reduction in velocity obtained for ad samples magnetic susceptibility logs characterized by a pattern of peaks induced by several volcaniclastic levels present in the succession indicated that the ad method significantly reduces core shortening among geotechnical investigations cyclic shear tests provided small strain shear moduli always higher in ad samples whilst the response of oedometer compression tests was equivocal in fact methods for assessing sample disturbance have demonstrated to bear limited effectiveness when applied to soils with relatively low clay content and significant overconsolidation as it is the case of the studied sediments

flow and mixing in ascension a steep narrow canyon 1 a thin gash in the continental slope northwest of monterey bay ascension canyon is steep with sides and axis both strongly supercritical to m2 internal tides a hydrostatic model forced with eight tidal constituents shows no major sources feeding energy into the canyon but significant energy is exchanged between barotropic and baroclinic flows along the tops of the sides where slopes are critical average turbulent dissipation rates observed near spring tide during april are half as large as a two week average measured during august in monterey canyon owing to ascension s weaker stratification however its average diapycnal diffusivity 3 9 10 3 m2 s 1 exceeded the 2 5 10 3 m2 s 1 found in monterey most of the dissipation occurred near the bottom apparently associated with an internal bore and just below the rim where sustained cross canyon flow may have been generating lee waves or rotors the near bottom mixing decreased sharply around ascension s one bend as did vertically integrated baroclinic energy fluxes dissipation had a minor effect on energetics which were controlled by flux divergences and convergences and temporal changes in energy density in ascension the observed dissipation rate near spring tide was 2 1 times that predicted from a simulation using eight tidal constituents averaged over a fortnightly period the same observation was 1 5 times the average of an m2 only prediction in monterey the previous observed average was 4 9 times the average of an m2 only prediction

the july 1996 flood deposit in the saguenay fjord quebec canada implications for sources of spatial and temporal backscatter variations in july 1996 a major rainstorm and flood took place in the saguenay fjord backscatter strength measurements made with a simrad em1000 multibeam echosounder in 1993 1997 and 1999 have shown spatial and temporal variations which are interpreted in relation to the occurrence of the flood after empirical calibration of the different maps the data show an overall diminution of 5 db in backscatter strength in 1997 1 yr after the flood took place while the data sets obtained in 1993 and 1999 show comparable levels of backscatter strength the different data sets show a similar pattern of low and high backscatter patches which represent variations of the backscatter strength of a few decibels several grain size and water content measurements were also carried out on sediment box core and grab samples from the fjord bottom in 1997 and 1999 these have shown that the areas with higher acoustic backscatter correspond to the finer sediments while the low backscatter patches correspond to the coarser material the data show little relation between water content and backscatter strength thus indicating a poor dependence between the impedance terms bulk density and sound speed and the backscatter having taken this into account the major contribution to backscatter strength is assumed to result from differences in surface and volume roughness of the sediment since finer grain sizes offer higher backscatter the grain size of the sediment is not considered as being a major contributor to roughness and hence backscatter strength the major factor that seems to control roughness generation in the saguenay fjord is considered to be bioturbation the areas where geological processes most physically disturb the bottom which coincide with the areas where also most accumulation takes place and the coarser grain sizes are deposited are more sparsely colonized by organisms this results in a lower degree of bioturbation lower roughness and thus backscatter strength this hypothesis helps explain the variation in backscatter strength observed between the different measurement years the several million tons of sediment deposited in the fjord bottom after the 1996 flood buried the benthic fauna which was still recovering 1 yr later the less bioturbated sediment at this time would present lower roughness with respect to the 1993 and 1999 data resulting in a lower backscatter strength

distribution and biogeochemistry of sedimentary humic substances in the st lawrence estuary and the saguenay fjord quebec abstract the concentrations of sedimentary humic substances hs were measured in the st lawrence marine system quebec canada including the saguenay fjord concentration ranges for humin humic acids and fulvic acids were 7 49 1 19 and 0 5 6 mg per gram of sediment dry weight respectively hs always represented the dominant component of sediment organic matter som i e 52 100 for which humin humic acids and fulvic acids accounted for 38 88 4 28 and 2 14 respectively these results indicate that most hs and an important part of som were associated with the mineral matrix and thus defined as humin hs concentrations varied slightly by site location and depth but major changes in concentration in the fjord were caused by episodic events such as floods and landslides in the fjord sedimentary hs were mostly terrigenous and molecules such as lignin likely contributed to the high proportions of hs in the st lawrence estuary an important input of marine particulate organic matter and favorable conditions for its degradation seem to have promoted the mineralization of the labile som before its burial the less labile som was buried in sediments where humification and stabilization appeared to occur such processes could explain the lower som concentrations but greater humin proportions with increasing distance downstream and sediment depth estimations based on hs profiles suggest that 25 of the surface som will be preserved in deeper layers i e 1 m principally in the form of humin sorption of organic matter onto mineral surfaces might have contributed to som preservation and humin stabilization in sediments drift spectroscopy suggests that carboxylate groups may mediate this sorption

diagnosing a partly standing internal wave in mamala bay oahu 1 an internal partly standing wave in mamala bay hawaii is studied using new observations and the princeton ocean model pom previous work suggested a convergence in the bay of east and westbound waves emanating from kaena ridge and makapuu point respectively new energy flux measurements with shipboard adcp ctd confirm that makapuu point is the eastern source after validating the pom results against observations the model output is modally decomposed and compared with the expected theoretical patterns of kinetic and available potential energy energy flux and group velocity for a partly standing wave agreement is seen for the first baroclinic mode which also contains most of the energy the results confirm previous suggestions of standing wave dynamics in mamala bay

mixing in the romanche fracture zone the romanche fracture zone is a major gap in the mid atlantic ridge at the equator which is deep enough to allow significant eastward flows of antarctic bottom water from the brazil basin to the sierra leone and guinea abyssal plains while flowing through the romanche fracture zone bottom water properties are strongly modified due to intense vertical mixing the diapycnal mixing coefficient in the bottom water of the romanche fracture zone is estimated by using the finestructure of ctd profiles the microstructure of high resolution profiler data and by constructing a heat budget from current meter data the finestructure of density profiles is described using the thorpe scaleslt it is shown from microstructure data taken in the bottom water that the ozmidov scale lo is related to lt by the linear relationship lo 5 0 95lt similar to other studies which allows an estimate of the diapycnal mixing coefficient using the osborn relation the thorpe scale and the diapycnal mixing coefficient estimates show enhanced mixing downstream eastward of the main sill of the romanche fracture zone in this region a mean diapycnal mixing coefficient of about 1000 3 1024 m2 s21 is found for the bottom water estimates of cross isothermal mixing coefficient derived from the heat budgets constructed downstream of the current meter arrays deployed in the romanche fracture zone and the nearby chain fracture zone are in agreement with the finestructure estimates of the diapycnal mixing coefficient within the romanche fracture zone although the two fracture zones occupy only 0 4 of the area covered by the sierra leone and guinea abyssal plains the diffusive heat fluxes across the 1 4 8c isotherm in the romanche and chain fracture zones are half that found over the abyssal plains across the 1 88c isotherm emphasizing the role of these passages for bottom water property modifications

transition from partly standing to progressive internal tides in monterey submarine canyon monterey submarine canyon is a large sinuous canyon off the coast of california the upper reaches of which were the subject of an internal tide observational program using moored profilers and upward looking moored adcps the mooring observations measured a near surface stratification change in the upper canyon likely caused by a seasonal shift in the prevailing wind that favoured coastal upwelling this change in near surface stratification caused a transition in the behaviour of the internal tide in the upper canyon from a partly standing wave during pre upwelling conditions to a progressive wave during upwelling conditions using a numerical model we present evidence that either a partly standing or a progressive internal tide can be simulated in the canyon simply by changing the initial stratification conditions in accordance with the observations the mechanism driving the transition is a dependence of down canyon supercritical internal tide reflection from the canyon floor and walls on the depth of maximum stratification during pre upwelling conditions the main pycnocline extends down to 200 m below the canyon rim resulting in increased supercritical reflection of the up canyon propagating internal tide back down the canyon the large up canyon and smaller down canyon progressive waves are the two components of the partly standing wave during upwelling conditions the pycnocline shallows to the upper 50 m of the watercolumn above the canyon rim resulting in decreased supercritical reflection and allowing the up canyon progressive wave to dominate

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

strength development with burial in fine grained sediments from the saguenay fjord quebec following a sedimentological and geotechnical investigation two main types of materials were identified in the saguenay fjord 1 organic rich sediments deposited by continuous sedimentation and 2 unbioturbated sediments deposited rapidly by episodic events the consolidation state of sediments with depth were analysed in all subsurface deposits sediments are overconsolidated irrespective of the depositional processes however in continuously deposited sediments strength develops more rapidly than in turbidites or mass flows in the surficial bioturbated layer strength and liquidity index gradients are at a maximum and the rate of strength variation can reach values as high as 9 kpa kpa results from one dimensional creep tests suggest that in the organic poor turbidites the strength development is controlled at least partly by thixotropic strengthening for bioturbated clays it appears that the viscosity and the aggregating potential of organic matter controls the evolution of the strength

development of the submarine channel in front of the nidelva river trondheimsfjorden norway abstract the nidelva submarine channel is a 4 km long and up to 100 m deep erosional feature seaward of a former outlet of the river nidelva in trondheimsfjorden norway mechanisms of channel evolution and sedimentary processes associated to its development are revealed by analyzing the sea bed morphology and the stratigraphy of the fjord sediments based on high resolution seismic data swath bathymetry imaging and gravity cores seismic data suggest that the submarine channel is eroded into late pleistocene clays filling a bedrock depression a thick holocene deltaic succession overlay the glacio marine clays seismic facies suggest that turbidity currents likely initiated downcutting of the channel in the early holocene these flows were guided by sea bed morphology and bedrock exposures favouring confluence and acceleration the area was subjected to glacio isostatic rebound and rapid fall of relative sea level in the holocene this resulted in a fast delta progradation likely with an enhanced activity of delta derived sediment gravity flows promoting incision in mid to late holocene such flows including hyperpycnal flows were responsible for deep incision of the channel laminated clay rich beds are interpreted as deposited by the overspill of turbiditic flows along the channel and likely originate from large terrestrial quick clay slides in the last 2000 years erosive flows initiated by mass wasting along the coast controlled the evolution of the channel after the mouth of the nidelva river moved to a more easterly position in the embayment present slope failure along the channel flanks seems to be controlled by the distribution of the laminated clay rich layers in the stratigraphy

propagation and dissipation of the internal tide in upper monterey canyon 1 submarine canyons are sites of intense turbulence and mixing monterey canyon cuts into the continental shelf off california and is defined by its sinuous nature temperature salinity and current velocity measurements were made over 21 days in april 2009 with a depth cycling towed body to understand internal tide propagation and dissipation through the canyon bends cross canyon transects reveal complex flow patterns that follow large scale bathymetry on scales greater than 5 km changes in thalweg direction deflect baroclinic energy flux but the bends in the measurement region are too sharp for the flux to follow the thalweg ridges that form the bends in the canyon act as obstacles to the flow and turbulent dissipation rates greater than 1 10 5 m2 s 3 were observed on their flanks especially at the largest meander the gooseneck the canyon integrated baroclinic energy flux increased from 2 7 mw at the most western section to 3 7 mw at the gooseneck ridge which has a nearly critical bottom slope with respect to the semidiurnal baroclinic tide on the western side baroclinic energy flux was 50 less on the eastern side of the ridge while measured dissipation near the gooseneck meander was sufficient to explain the flux divergence turbulence near the gooseneck may have been undersampled between the gooseneck ridge and the most eastern cross canyon transect dissipation may account for the decrease in the energy flux though a local energy balance does not hold the energy budget is balanced over the larger scale of the measurement region east of the gooseneck ridge

internal wave reflection on shelf slopes with depth varying stratification abstractreflection of internal waves from sloping topography is simple to predict for uniform stratification and linear slope gradients however depth varying stratification presents the complication that regions of the slope may be subcritical and other regions supercritical here a numerical model is used to simulate a mode 1 m2 internal tide approaching a shelf slope with both uniform and depth varying stratifications the fractions of incident internal wave energy reflected back offshore and transmitted onto the shelf are diagnosed by calculating the energy flux at the base of slope with and without topography and at the shelf break for the stratifications topographies considered in this study the fraction of energy reflected for a given slope criticality is similar for both uniform and depth varying stratifications this suggests the fraction reflected is dependent only on maximum slope criticality and independent of the depth of the pycnocline the majority of the reflected energy flux is in

virgin compression of structured soils this paper describes a study of the virgin compression behaviour of both naturally and artificially structured soils under one dimensional compression or isotropic compression it is proposed that during virgin compression the additional voids ratio sustained by soil structure is inversely proportional to the current mean effective stress the proposed formula has been verified for 20 different naturally and artificially structured soils and it is seen that the proposal describes well the behaviour of all these soils finally a general discussion on soil structure and its features is presented and the proposed compression equation is extended to describe the compression of structured soil along a general stress path cet exposa est une etude du comportement d une consolidation vierge sur des sols structuras de mani gravere naturelle et artificielle avec une consolidation unidimensionnelle on isotrope nous avancons que pendant la consolidation vierge le taux de pore additionnel subi pa

biogeomorphological implications of microscale interactions between sediment geotechnics and marine benthos a review abstract at the foundations of biogeomorphological processes in the sea lie interactions between the activities of marine benthic animals and the geotechnical properties of their sedimentary environments the potential significance of these interactions which take place at a microscale level of millimetres to metres for the large scale geomorphology of the seabed has rarely been appreciated in the context of this review large scale is defined as greater than 50 m to hundreds of kilometres the present review addresses this link drawing examples from a wide range of marine environments including estuaries the intertidal zone continental shelves and slopes and the deep sea it firstly considers sediment stabilisation slope failure sediment mixing biodeposition sediment compaction and hydrodynamic effects this is followed by a consideration of two extremes of the ecological pyramid the effects of marine meiofauna and marine vertebrates the final section draws attention to the central role of faunal mucus and extracellular polymeric material ecpm in many of the microscale interactions that we describe the implications of these microscale biological processes and features are discussed in terms of their influence on and control of the large scale geomorphology of the seabed

physicochemical and geotechnical characteristics of recent saguenay fjord sediments in the spring of 1985 the first goetechnical reconnaissance of recent saguenay fjord sediments took place in which were recorded the two saint jean vianney slides of 1663 and 1971 cores from the upper part of the fjord were tested onboard the ship and in the laboratory the mineralogy of the recent sediments is like that of the raised marine deposits of the area except for the organic content which is higher the microstructure of the sediment is quite typical of flocculated marine soils the freshly sedimented soil in its sedimentary environment has gained strength and sensitivity up to 12 in excess of what is usually expected for such material it has been concluded that the physicochemical characteristics of the sediment such as depicted by its initial plasticity before leaching are first order parameters in the source of apparent overconsolidation and structuration key words recent sediments shear strength sensitivity consolidation structuration microstructure landslide physicoche

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

flow and mixing in juan de fuca canyon washington we report breaking internal lee waves strong mixing and hydraulic control associated with wind driven up canyon flow in juan de fuca canyon washington unlike the flow above the canyon rim which shows a tidal modulation typical on continental shelves the flow within the canyon is persistently up canyon during our observations with isopycnals tilted consistent with a geostrophic cross canyon momentum balance as the flow encounters a sill near the canyon entrance at the shelf break it accelerates significantly and undergoes elevated mixing on the upstream and downstream sides of the sill on the downstream side a strong lee wave response is seen with displacements of o 100 m and overturns tens of meters high the resulting diffusivity is o 10 2 m2 s 1 sufficient to substantially modify coastal water masses as they transit the canyon and enter the salish sea estuarine system

turbulent mixing and exchange with interior waters on sloping boundaries abstractmicrostructure measurements along the axes of monterey and soquel submarine canyons reveal 200 300 m thick well stratified turbulent near bottom layers with average turbulent kinetic energy dissipation rates e 4 10 8 w kg 1 and eddy diffusivities k 16 10 4 m2 s 1 assuming mixing efficiency 0 2 to at least thalweg depths of 1200 m turbulent dissipation rates are an order of magnitude lower in overlying waters whereas buoyancy frequencies are only 25 higher well mixed bottom boundary layer thicknesses hn are an order of magnitude thinner than the stratified turbulent layer hn he because well stratified turbulent layers are commonly observed above slopes arguments that mixing efficiency should be reduced on sloping boundaries do not hold in cases of energetic internal wave generation or interaction with topography an advective diffusive balance is used to infer velocities and transports predicting horizontal upslope flows of 10 50 m day 1 extrapolating this estimate globa

observations of nonlinear internal wave run up to the surfzone abstractthe cross shore evolution of nonlinear internal waves nliws from 8 m depth to shore was observed by a dense thermistor array and adcp isotherm oscillations spanned much of the water column at a variety of periods at times nliws propagated into the surfzone decreasing temperature by 1 c in 5 min when stratification was strong temperature variability was strong and coherent from 18 to 6 m depth at semidiurnal and harmonic periods when stratification weakened temperature variability decreased and was incoherent between 18 and 6 m depth at all frequencies at 8 m depth onshore coherently propagating nliw events had associated rapid temperature drops t up to 1 7 c front velocity between 1 4 and 7 4 cm s 1 and incidence angles between 5 and 23 front position t and two layer equivalent height ziw of four events were tracked upslope until propagation terminated front position was quadratic in time and normalized t and ziw both decreased collapsing as a linearly decaying funct

aging of oil gas bearing sediments their compressibility and subsidence the in situ stiffness and apparent maximum preconsolidation stress of many soils and sediments appear to be higher than in the laboratory tests we seek to verify experimentally whether this also holds for deep marine sediments we also discuss an alternative explanation for this effect to the classical one implying the sample damage during coring we test numerically the explanation suggesting possible unaccounted changes in stiffness occurring in sediments in situ when subjected to aging or secondary compression for geological scale time periods results of aging tests on sandy and clayey sediments are presented involving secondary compression at the constant in situ stress level during which strain develops together with other changes in properties only two weeks of aging produced a notable increase in the apparent maximum preconsolidation stress and in the stiffness below it and above the in situ stress a framework for a mathematical model is proposed based on the supposition that during aging the sediment develops a secondary microstructure through reactions of local dissolution precipitation of less stable minerals

internal tide convergence and mixing in a submarine canyon abstractobservations from eel canyon located on the north coast of california show that elevated turbulence in the full water column arises from the convergence of remotely generated internal wave energy the incoming semidiurnal and bottom trapped diurnal internal tides generate complex interference patterns the semidiurnal internal tide sets up a partly standing wave within the canyon due to reflection at the canyon head dissipating all of its energy within the canyon dissipation in the near bottom is associated with the diurnal trapped tide while midwater isopycnal shear and strain is associated with the semidiurnal tide dissipation is elevated up to 600 m off the bottom in contrast to observations over the flat continental shelf where dissipation occurs closer to the topography slope canyons are sinks for internal wave energy and may have important influences on the global distribution of tidally driven mixing

influence of an organic poor landslide deposit on the early diagenesis of iron and manganese in a coastal marine sediment sediments and porewaters were subsampled from two box cores collected at 135 m depth on the landward slope of the largest basin of the saguenay fjord quebec canada the saguenay fjord sediments are composed mostly of eroded glaciomarine clays surrounding the fjord area the sediments contain relatively large concentrations of organic carbon and are sulfidic a few millimeters below the sediment water interface they are characterized by anomalously high hg concentrations and acid volatile sulfide avs pyrite ratios the vertical distribution of total hg concentrations in the sediments can be correlated to the organic matter content and an anthropogenic source the high avs pyrite ratios reflect conditions conducive to preservation of fe monosulfides in 1971 a catastrophic landslide resulted in the displacement and transport of 6 9 106m3 of post wisconsinian marine clay into the saguenay fjord the landslide material was deficient in organic carbon and anthropogenic hg relative to the indigenous sediment subsequent to burial the landslide deposit influenced the migration and deposition patterns of mobilizable elements acting alternatively as a sink and a source of reduced fe and mn as the redox boundary migrated through it nonsteady state sulfate reduction rates were established due to the nonuniform distribution of organic carbon with depth iron sulfide peaks reflect this distribution and the position of the relict redox boundary manganese remobilization was apparently unaffected by the deposition of the landslide layer and reduced mn migrated freely to the redox boundary a schematic representation of the sequence of diagenetic events which led to the postdepositional remobilization of fe and mn and the migration of the oxidation front following the deposition of the landslide material is proposed

internal tide reflection and turbulent mixing on the continental slope abstract observations of turbulence internal waves and subinertial flow were made over a steep corrugated continental slope off virginia during may june 1998 at semidiurnal frequencies a convergence of low mode onshore energy flux is approximately balanced by a divergence of high wavenumber offshore energy flux this conversion occurs in a region where the continental slope is nearly critical with respect to the semidiurnal tide it is suggested that elevated near bottom mixing k 10 3 m2 s 1 observed offshore of the supercritical continental slope arises from the reflection of a remotely generated low mode m2 internal tide based on the observed turbulent kinetic energy dissipation rate the high wavenumber internal tide decays on time scales o 1 day no evidence for internal lee wave generation by flow over the slope s corrugations or internal tide generation at the shelf break was found at this site

tenth canadian geotechnical colloquium recent developments in consolidation of natural clays a global analysis of the consolidation of natural clays is realized considering the consolidation process to be a combination of the effects of compressibility and of permeability the compressibil

a reflecting steepening and breaking internal tide in a submarine canyon submarine canyons are common features of the coastal ocean although they are known to be hotspots of turbulence that enhance diapycnal transport in their stratified waters the dynamics of canyon mixing processes are poorly understood most studies of internal wave dynamics within canyons have focused on a handful of canyons with along axis slopes less steep than semidiurnal d2 internal wave characteristics subcritical here we present the first tidally resolving observations within a canyon with a steeply sloping axis supercritical a process study consisting of two 24 hour shipboard stations and a profiling mooring was conducted in the la jolla canyon off the coast of la jolla ca baroclinic energy flux is oriented up canyon and decreases from 182 18 w m 1 at the canyon mouth to 46 5 w m 1 near the head the ratio of horizontal kinetic energy to available potential energy and the observed group speed of each mode are lower than expected for freely propagating d2 internal waves at each station indicating partial reflection harmonic analysis reveals that variance is dominated by the d2 tide moving up canyon the relative importance of d2 decreases and its higher harmonics are needed to account for a majority of the observed variance indicating steepening steep internal tides cause large isopycnal displacements 50 m in 100m water depth and high strain events these events coincide with enhanced o 10 7 10 5 m2 s 3 dissipation of turbulent kinetic energy at mid depths

organic matter in anoxic sediments off central peru relations of porosity microbial decomposition and deformation properties abstract microstructure of central peru continental margin sediments suggests that in environments of rapid hemipelagic sedimentation organic matter decomposition has a significant effect on geotechnical properties in highly porous surface sediments particles resembling the remains of fecal pellets appear to be coated by bacterial sheaths but after burial sheaths disappear as an increasingly uniform and closed structure of organo mineral aggregates develops interstitial water nutrient and solid phase c n and p profiles support the interpretation that this progression corresponds to decomposition and metabolite regeneration from labile organic matter by microbial sulfate reduction it is proposed that early aggregation has a strengthening effect and that this combined with the low density of near surface sediments results in an effective overburden pressure lower than experimentally determined preconsolidation pressures more basic knowledge of the lifetime of organo mineral aggregates and the influence of gross and local microstructure on the rates and products of diagenetic reactions is needed in order to verify the relationship between organic matter accumulation and sediment stability in continental margin environments

effects of biological activity by abyssal benthic macroinvertebrates on a sedimentary structure in the venezuela basin abstract macrobenthic standing stock estimates from the venezuela basin were in agreement with those calculated from other ocean basins biomass and density values were significantly higher at a site characterized by hemipelagic sedimentation compared to two sites characterized by carbonate and turbidite sedimentation the higher standing stock is probably related to the higher input of organic matter to that site vertical distribution of fauna suggests that sediment was well mixed to 6 8 cm depth at the carbonate and turbidite sites and to 10 12 cm depth at the hemipelagic site infrequent mixing probably extends to 30 cm at the turbidite site 18 cm at the hemipelagic site and 10 cm at the carbonate site mixing rates were predicted to be the highest at the hemipelagic site where benthic standing stocks were highest these mixing depths and rates were in general agreement with those determined by radiochemical methods and by visual and x ray photographic observations gradients of decreased porosity and increased density were probably the result of biological activity burrowing and tube dwelling as opposed to effects of overburden pressure sediment shear strength was controlled by biological activity coupled with biologically mediated chemical bonding at the redox discontinuity layer destruction of sand sized foraminiferan tests by faunal ingestion of sediments contributes to a reduction in mean grain size at the sediment surface

micro scale geotechnical variability in continental slope and abyssal sediments influenced by the oxygen minimum zone in the arabian sea abstract we describe a new micro scale method of measuring the penetration resistance of the surficial layers of slope and abyssal plain sediments within and below the omz on the oman continental slope the micro scale load resistance penetrometer mlrp continuously measures the penetration resistance q of a cylindrical probe driven at constant velocity into cores of sediment recovered by sub coring box core samples measurements are recorded at 0 8 mm depth intervals into the sediment by an automated data acquisition system these provide continuous depth profiles of penetration resistance q and its variability qr in surficial sediments 0 100 mm the results represent the first published application of this technique to slope and abyssal plain sediments the q data divide the stations into shallow omz somz stations 391 854 m deep omz domz stations 987 1285 m and abyssal non omz anomz stations 3392 3396 m one station 688 m was anomalous penetration resistance q was positively related to shear strength and inversely related to water content but not to bioturbation measured as burrow numbers relaxation and pull out data were obtained from three stations three patterns of qr were observed consisting of well confined data data containing large negative and positive spikes and data showing a progressive down core increase in spikes four additional measures of q variability were defined which show statistically significant relationships with burrow numbers an increase in bioturbation estimated by burrow numbers is associated with a decrease in micro scale variability in q this is related to the activity of burrowing macrofauna our results are discussed in the context of biogeotechnical modifications of sedimentary environments

u pb geochronology of zircons from fossiliferous sediments of the hajnacka i maar slovakia type locality of the mn 16a biostratigraphic subzone lacustrine sediments of the hajnacka i maar of southern slovakia contain teeth and skeletal remains of a mammal fauna including index early villanyian arvicoline rodents u pb dating of magmatic zircons extracted from the redeposited fossiliferous maar sediments revealed a total of six volcanic events the oldest age of 3 43 ma was interpreted as that corresponding to the initial phreato magmatic eruption that created the maar most zircons grouped around 3 06 0 03 ma the age attributed to the catastrophic eruption that killed the mammal assemblage thriving within and around the maar studied this age coincides with the 3 1 ma boundary between the mn 16a and 16b subzones of the european mammal neogene chronostratigraphic scale estimated from the succession of early villanyian palaeontological localities according to the hypsometry of rodent teeth younger zircon ages overlapped those of the neighbouring basaltic lava flows necks and dykes thus recording superimposed effusions the youngest 1 58 ma old zircon defines the age limit for the final redeposition of the fossiliferous sediments in the maar drainage lake regime

earthquake and flood induced turbidites in the saguenay fjord quebec a holocene paleoseismicity record abstract a 38 m long piston core from the deep basin of the saguenay fjord quebec recorded rapidly deposited layers rdl interpreted to represent major floods and earthquakes over the past 7200 years high resolution physical magnetic and sedimentological analyses revealed at least 14 rdl generally with a sandy base and a light gray color interbedded with hemipelagic sediments digital x radiography and grain size analyses at

internal tide radiation from mendocino escarpment abstract strong semidiurnal internal tides are observed near mendocino escarpment in full depth profile time series of velocity temperature and salinity velocity and density profiles are combined to estimate the internal tide energy flux divergence of this flux demonstrates that its source is the barotropic tide interacting with the escarpment a baroclinic energy flux of 7 kw m 1 radiates from the escarpment corresponding to 3 of the 220 kw m 1 fluxing poleward in the surface tide energy and energy flux are concentrated in packets that emanate from the flanks of the ridge surmounting the escarpment and one site 90 km north of the escarpment coherent beamlike structure along semidiurnal ray paths remains identifiable until the first surface reflection beyond the first surface reflection north of the escarpment the energy flux drops by 2 kw m 1 and beams are no longer discernible turbulence as inferred from finescale parameterizations is elevated by over two orders of magnitude relative to th