geophysics of proposed proterozoic sutures in canada abstract sutures have been identified or proposed at several sites in the canadian shield although many authors have suggested that some form of primitive plate tectonic processes have played a major role in the formation of the archean crust of the superior structural province proterozoic sutures resembling phanerozoic examples have been proposed only within the younger churchill and grenville provinces and at or near the boundaries between the older superior and slave provinces and the younger provinces gravity magnetic seismic and paleomagnetic data related to three proposed sutures in the latter category have been interpreted and generally support the view that the shield comprises a mosaic of once separated but now joined cratonic blocks the sutures vary in complexity from wide zones containing distinctive rocks formed at ancient accreting and consuming plate margins to cryptic sutures marked only by abrupt changes in metamorphism and zones of cataclasis paired negative and positive gravity anomalies associated with these sutures have been interpreted in terms of juxtaposed crustal blocks of different density and thickness magnetic anomaly patterns change abruptly at structural province boundaries available seismic results support the concept of thickened crust in the younger province as derived from gravity modelling most authors prefer interpretation of proterozoic pole positions in terms of one plate models but in some cases the interpretation of paleomagnetic data is equivocal and two plate models have been proposed

reflection study of the haughton impact crater the western flank of the haughton impact crater was imaged with a 10 25 km long multifold reflection profile the seismic waves mapped 10 acoustic discontinuities in the stratified sedimentary target rocks the impact disturbed the entire 1900 m of the highly competent paleozoic strata the average seismic velocity of over 6000 m s exhibited by these rock units is a clear indication of the undisturbed impact area s unusually high elastic strength the dynamic and destructive forces of the cratering process are manifested on the seismic profile by a dense and complex system of faults these steeply dipping faults penetrated the sedimentary rocks but showed no recognizable extension into the crystalline basement the recognition of normal faults 3 km west of the faulted annulus suggests a structural diameter of 24 km some 4 km larger than postulated from earlier geological data it has been found that the surface morphologically distinct ring zones do not have seismically recognizable subsurface signatures in the central interior region of the crater coherent reflection signals are lacking however some weak local acoustic discontinuities are recognized the underlying crystalline basement rocks did not exhibit any seismically mappable impact related zones of alteration

a note on megaripples in the surf zone evidence for their relation to steady flow dunes megaripples in the combined flow environment of the nearshore are proposed to behave like dunes or large ripples in rivers tidal estuaries and deserts their profile basically is symmetric and thus significantly different from the traditional asymmetric triangular features observed in steady flows similarly their planform often exhibits little directionality unlike crescentic or lunate steady flow dunes that point in the downstream direction these characteristics are the result of complex combined flows in the nearshore including oscillatory flows wave skewness and steady currents undertow rips and alongshore flows recent observations of megaripples in the nearshore suggest that they occur frequently however they are rarely considered in studies of flow resistance or sediment transport in addition megaripples are thought to be the source of hummocky cross stratification in sedimentary sequences and are generally attributed to storm waves on inner continental shelves however observations show that they also exist inside the surf zone and under lower energy conditions a better understanding of their dynamics and thus their occurrence and characteristics would improve the understanding of nearshore wave and circulation dynamics sediment transport large scale morphodynamics and the resulting sedimentary sequences it is hypothesized that megaripples in the nearshore are dynamically similar to steady flow features which are observed in rivers estuaries and deserts and have been studied in much more detail

interpretation of 2d seismic profiles in complex geological terrains examples from the flin flon mining camp canada abstracta methodology was demonstrated for the 3d interpretation of networks of 2d seismic profiles in conjunction with other 3d geological constraints the methodology employs 3d migration of 2d seismic data as a means of directly correlating reflections with out of plane geology followed by ray trace modeling of interpreted 3d geological surfaces the proposed interpretation workflow was demonstrated with examples taken from 2d seismic profiles that were recently acquired for vms ore exploration within the flin flon mining camp canada in each example the utility of the method was demonstrated and the resulting inferences were validated by comparison with a true 3d seismic survey acquired over a subset of the same area

observations of sand bar evolution on a natural beach waves currents and the location of the seafloor were measured on a barred beach for about 2 months at nine locations along a cross shore transect extending 255 m from 1 to 4 m water depth the seafloor location was measured nearly continuously even in the surf zone during storms with sonar altimeters mounted on fixed frames the crest of a sand bar initially located about 60 m from the shoreline moved 130 m offshore primarily when the offshore significant wave height exceeded about 2 m with 1 5 m of erosion near the initial location and 1 m of accretion at the final location an energetics type sediment transport model driven by locally measured near bottom currents predicts the observed offshore bar migration but not the slow onshore migration observed during low energy wave conditions the predicted offshore bar migration is driven primarily by cross shore gradients in predicted suspended sediment transport associated with quasi steady near bottom offshore flows these strong 50 cm s currents intensified near the bar crest by wave breaking are predicted to cause erosion on the shoreward slope of the bar and deposition on the seaward side the feedback amoung morphology waves circulation and sediment transport thus forces offshore bar migration during storms

the impact of bedform migration on benthic oxygen fluxes permeable sediments are found wide spread in river beds and on continental shelves the transport of these sediments is forced by bottom water currents and leads to the formation of bedforms such as ripples and dunes the bottom water flow across the bedforms results in pressure gradients that drive pore water flow within the permeable sediment and enhance the supply of reactive substrates for biogeochemical processes this transport reaction system has been extensively studied for the case of stationary bedforms whereas bedform migration the most ubiquitous form of sediment transport has been often ignored to study the impact of sediment transport on pore water flow we incorporated an empirical model of bedform migration into a numerical transport reaction model for porous media using oxygen as reactive solute the modeled oxygen flux changes significantly as soon as the sediment divides into an upper mobile layer migrating bedform and a stationary layer underneath the bedform is increasingly flushed with oxic bottom water whereas pressure gradients and pore water flow reverse at increasing rate underneath the bedform this suppresses net pore water displacement and reduces the oxygen penetration depth up to 90 in effect the overall oxygen uptake decreases significantly with bedform migration although bottom water velocities increase this counterintuitive effect is systematically described for a range of different sediment types current velocities and respiration rates and should be considered in future studies

analysis and interpretation of the heterogeneous rupture process application of the empirical green s function method and nonlinear inversion technique to large earthquakes abstract heterogeneous rupture processes were revealed using an empirical green s function egf method and a nonlinear inversion technique three events the 1980 east izu peninsula earthquake the 1983 japan sea earthquake and the 1987 east chiba earthquake are studied kernel events used as empirical green s functions were selected among the foreshocks and aftershocks the dimension and orientation of the fault plane were evaluated from the aftershock distribution and main shock fault plane solution a moment ratio between the main shock and the kernel event was estimated in order to identify the number of subfaults strong motion waveforms recorded at near distances were inverted to estimate moment release rupture time and rise time at each subfault with the stress drop calculated from the moment release and rise time distributions of these faulting parameters can be related to the aftershock distribution and geological structures general features are that the moment release was large where the aftershock activity was low that the irregular rupture propagations detected here were related to geological structures such as a ridge junction seamount chains and other tectonic plate boundaries and that stress drop distributions show some relation to the pattern of aftershocks an exception is the small moment release at the bending corner of the 1983 japan sea earthquake where the aftershock activity was low with this method it is possible to extract not only the detailed source history but also information on geophysical structures

linkage between turbulent kinetic energy waves and suspended sediment concentrations in the nearshore zone abstract knowledge about the tradeoffs among turbulent kinetic energy tke waves and suspended sediment concentrations sscs in the nearshore zone is relevant for understanding beach morphodynamics at different temporal and spatial scales a field measurement lasting for nearly three tidal cycles was conducted to holistically discern couplings between tke waves and sscs with further evaluation of the relative significance of tke and waves on sscs under various wave conditions over a meso macro tidal beach yintan to the north of beibu gulf china the results showed a dramatic increase in wave groupiness intensity from the shoaling wave condition to the breaking wave condition and a clear decrease further into the surf bore condition the near bed tkes under the surf bore condition were an order of magnitude larger than those under the breaking and shoaling wave conditions at the measurement position the averaged sscs in the near bed approximately 10 cm under the surf bore condition were 1 5 and 4 5 times larger than those under breaking and shoaling wave conditions respectively the variations in relative wave height were a decisive indicator for the differences in tke intensities among different wave conditions while the occurrence of peak tkes at the wave front within the intrawave cycle was associated with flow acceleration regardless of wave conditions mean sscs were well correlated with waves in terms of both incident wave scale and wave group scale which was limited to the shoaling wave condition and the occurrence of near bed intrawave peak sscs was always related to the offshore wave phase further tke contributed more effectively to sediment suspension at the wave group scale than at the incident wave scale especially under broken wave condition among the hydrodynamic factors tke played the most important role in the variations in sscs for all wave conditions flow acceleration served as the second most important factor under the broken wave condition while wave group single wave and advection were equivalent and less important factors for sscs

seismic reflection profiling of the pyhasalmi vhms deposit a complementary approach to the deep base metal exploration in finland abstractin the pyhasalmi case study the seismic data is used in direct targeting of shallowly dipping mineralized zones in a massive sulfide ore system that was deformed in complex fold interference structures under high grade metamorphic conditions the pyhasalmi volcanic hosted massive sulfide vhms deposit 50 mt is located in a proterozoic volcanic belt in central finland acoustic impedance of pyhasalmi ore 32 106 kg m2 s is distinct from the host rocks 16 19 106 kg m2s enabling its detection with seismic reflection methods drill hole logging further indicates that the seismic imaging of a contact zone between mafic and felsic volcanic rocks possibly hosting additional mineralizations is plausible six seismic profiles showed discontinuous reflectors and complicated reflectivity patterns due to the complex geology the most prominent reflective package at 1 2 km depth was produced by shallowly dipping contacts between interlayered felsic and mafic volcanic rocks the topmost of these b

a progressive geophysical exploration strategy at the shea creek uranium deposit the athabasca basin is a large paleo to mesoproterozoic quartz arenite sandstone basin that occupies most of the northernmost quarter of sas katchewan and a smaller portion of northeastern alberta the locations of the basin and the uranium discoveries discussed in this paper are shown in figure 1 the majority of the unconformity type uranium deposits of the athabasca basin are sandstone hosted and are associated with post hudsonian reactivated graphitic faults within aphebian metasedimentary gneisses of the wollaston domain and the wollaston mudjatik transition zone in the eastern portion of the athabasca basin however the shea creek deposit consisting of the anne kianna and colette zones occurs in the western portion of the basin and is associated with the transition between the granitic clearwater domain and the lloyd domain

3d seismic imaging of volcanogenic massive sulfide deposits in the flin flon mining camp canada part 2 forward modeling abstractwe applied seismic modeling for a detailed 3d geologic model of the flin flon mining camp canada to address some imaging and interpretation issues related to a 17 km2 3d survey acquired in the camp and described in a complementary paper part 1 a 3d geologic volumetric model of the camp was created based on a compilation of geologic data constraints from drillholes surface geologic mapping interpretation of 2d seismic profiles and 3d surface and grid geostatistical modeling techniques the 3d modeling methodology was based on a hierarchical approach to account for the heterogeneous spatial distribution of geologic constraints elastic parameters were assigned within the model based on core sample measurements and correlation with the different lithologies the phase screen algorithm used for seismic modeling was validated against analytic and finite difference solutions to ensure that it provided accurate amplitude variation with offset behavior for dipping strata synthetic data were gener

sand bed roughness in the nearshore 1 measurements made using sonar altimeters mounted on an amphibious surveying vehicle are analyzed for root mean square rms bedform roughness observations for 22 days over a 500 m 700 m area are used to quantify the cross shore distribution of roughness and its variability large bedforms with amplitudes 5 50 cm occur frequently in shallow water 2 m water depth however the patchiness of these bedforms is also largest in shallow water this is likely owing to the spatial and temporal variability of the waves and currents of the sediment grain size distributions and of the large scale nearshore morphology large bedforms were observed to exist only for mobility numbers 150 above this threshold the rms roughness was 2 cm and the bed was interpreted to have transitioned to sheet flow conditions however the state of the bed e g large ripples small ripples flat bed was not predictable for mobility numbers between about 30 and 150 existing models for orbital ripples do not predict the observed large bedforms and have little predictive skill for these data

intrawave observations of sediment entrainment processes above sand ripples under irregular waves 1 measurements of intrawave sediment entrainment processes are reported above ripples under irregular waves generated in a large scale flume facility the data consist of substantive observations of small scale processes collected at high spatial and temporal resolution under irregular wave forcing typical of coastal environments acoustic measurements were made of water velocities bed forms and suspended sediment concentration over plane and rippled beds during each rippled bed experiment measurements were taken over the crests of steep sided ripples above which flow separation was considered likely to occur above the ripple crests a strong intrawave variation in the near bed suspended sediment indicative of vortex formation and shedding was observed to dominate wave half cycles where the orbital diameter was greater than 1 2 times the ripple wavelength l the irregular waves were parameterized with a significant wave height hs and a significant orbital diameter d0s thus during irregular wave conditions and over steep ripples where d0s l 1 2 vortex shedding was deemed as the dominant sediment entrainment process furthermore the percentage of wave half cycles where vortex shedding was observed was found to scale as 26 d0s l these results demonstrate for under irregular waves the existence of a clear suspended sediment structure consistent with vortex shedding previously observed under regular waves citation o hara murray r b p d thorne and d m hodgson 2011 intrawave observations of sediment entrainment processes above sand ripples under irregular waves j geophys res 116 c01001 doi 10 1029 2010jc006216

modes of cross shore sediment transport on the shoreface of the middle atlantic bight the mechanisms responsible for onshore and offshore sediment fluxes across the shoreface zone seaward of the surf zone were examined in a 3 year field study the study was conducted in the southern part of the middle atlantic bight in the depth region 7 17 m using instrumented tripods supporting electromagnetic current meters pressure sensors suspended sediment concentration sensors and sonar altimeters the observations embraced fairweather moderate energy swell dominated and storm conditions cross shore mean flows ranged from near zero during fairweather to 20 cm s 1 during the storm oscillatory flows were on the order of 10 cm s 1 during fairweather and 100 cm s 1 during the storm suspended sediment concentrations at about 10 cm above the bed were 5 kg m 3 during the storm three methods were applied to evaluate the relative importance of incident waves long period oscillations mean flows and gravity in effecting shoreward or seaward sediment flux 1 an energetics transport model was applied to instantaneous near bottom velocity data 2 higher moments of near bottom flows were estimated and compared and 3 suspended sediment fluxes were estimated directly from the instantaneous products of cross shore velocity and suspended sediment concentration the results show that measurable contributions were made by all four of the processes most significantly mean flows were seen to dominate and cause offshore fluxes during the storm and to contribute significantly to onshore and offshore flux during fairweather and moderate energy incident waves were in all cases the major source of bed shear stress but also caused shoreward as well as seaward net sediment advection low frequency effects involving wave groups and long period waves made secondary contributions to cross shore sediment flux contrary to expectations low frequency fluxes were just as often shoreward as seaward whereas cross correlations between suspended sediment concentration and the instantaneous near bottom current speed were high and in phase under storm conditions they were weak and out of phase during fairweather conditions this suggests that simple energetics models are probably inadequate for predicting fairweather transport of suspended sediment

relaxation time effects of wave ripples on tidal beaches 1 seabed roughness due to wave ripples is a key factor in controlling sediment transport processes in the nearshore zone roughness is commonly considered a function of the ripple geometry which in turn can be predicted from sediment and hydrodynamic parameters existing ripple predictors consider the bed morphology to be in equilibrium with the hydrodynamics whereas recent laboratory measurements show that the time scale for ripple development is of the order of tens of minutes to hours here we show that wave ripples on tidal beaches are significantly affected by relaxation time effects with ripple height and length progressively increasing during the rising tide and remaining constant during the falling tide moreover we examine the ripples in the context of existing empirical models and suggest how the temporal evolution over a tidal cycle may be predicted

frequency dependent cross shore suspended sediment transport 1 a non barred shoreface abstract the local time varying and time averaged suspended sediment transports across a marine non barred shoreface were obtained from field measurements of the near bed velocity and sediment concentration vectors using electromagnetic current meters and optical backscatterance suspended solids sensors co spectral analyses of velocity and sediment concentration revealed the contributions of waves of different frequencies to the total transport the transport attributable to quasi steady currents was determined from the product of the time averaged cross shore velocity and sediment concentration estimates of the local time integrated sediment volume flux total and net and the associated erosion or accretion were determined using depth of activity rods suspended sediment transport was associated with 1 local wind forced waves 2 swell 3 low frequency waves group bound long waves and 4 offshore directed mean currents undertow these transport components varied spatially and temporally in response to changes in the wave height to water depth ratio the local net oscillatory transport rate at wind wave and swell wave frequencies was directed onshore predominantly and increased as water depth decreased in association with wave shoaling the local mean sediment transport rate was predominantly offshore and dominated the net transport rate wherever wave induced components were weak relative to the mean currents under breaking waves the suspended sediment transport contribution associated with wind waves and swell waves was reduced as a result of dissipation the net suspended sediment transport rate exhibited a distinct vertical structure reflecting the balance at each elevation between the opposing mean and oscillatory components of transport the local time averaged total and net sediment volume flux and resulting erosion and accretion patterns support the hypothesis of a near balance in sediment flux for the complete storm event

the drag coefficient bottom roughness and wave breaking in the nearshore the bottom drag coefficient in the nearshore has been suggested to depend on bottom roughness bedforms or alternatively on wave breaking the hypothesis that bottom drag coefficient depends on bottom roughness is tested with 2 months of field observations collected on a sandy ocean beach during the duck94 field experiment both the drag coefficient estimated from alongshore momentum balances and bottom roughness estimated from fixed altimeters are larger within the surfzone than in the region farther seaward although the drag coefficient increases with roughness seaward of the surfzone no relationship was found between the drag coefficient and roughness related quantities within the surfzone these results suggest that breaking wave generated turbulence increases the surfzone drag coefficient

3d seismic survey at the millennium uranium deposit saskatchewan canada mapping depth to basement and imaging post athabasca structure near the orebody three dimensional seismic reflection measurements have been used to assist mine planning at the millennium uranium deposit canada the deposit is located within the crystalline basement separated

swash zone sediment dynamics a comparison of a dissipative and an intermediate beach high frequency measurements of water depth current velocity and suspended sediment concentration were used to investigate sediment transport processes in the swash zones of a dissipative beach and a steeper intermediate beach infragravity frequency motions dominated velocity spectra of the dissipative beach swash while incident wave frequencies dominated the velocity spectrum of the intermediate beach swash velocity variance the ratio of local wave height to water depth mean bed shear stress and the mean friction velocity were greater on the intermediate beach mean suspended sediment concentrations were an order of magnitude greater on the intermediate beach infragravity frequencies dominated the oscillatory component of sediment transport on the dissipative beach incident wave frequency sediment transport dominated the intermediate beach a maximum in the net shoreward transport occurred in approximately the mid swash zone on both beaches suggesting accretion in the shoreward half of the swash and erosion in the seaward part of the swash net sediment transport rates were lower on the ebb tide than on the flood tide despite similar incident wave conditions

three simple models of wave sediment transport abstract the process of sediment transport by nonbreaking waves over horizontal rippled beds is presented by three different models which are evaluated through comparison with wave flume data the conclusion from this testing is the simpler the better it is shown that the process in question can in fact be modelled adequately without quantitative consideration of the suspended sediment distribution only a reference average concentration at the bed is needed on the other hand classical diffusion models severely underpredict the transport of coarse sand in suspension because the process is much more organized than diffusion the possibility of adapting the models to conditions involving sheet flow and or breaking waves is discussed

cross shore migration of lunate megaripples during duck94 1 remote acoustic observations of lunate megaripple migration are presented from two storm events during the duck94 nearshore dynamics experiment for time periods during which longshore currents were weak 20 cm s during these periods significant wave orbital velocities were 50 80 cm s megaripple heights were 0 05 0 5 m megaripple horns were directed shoreward the crest to trough slope of the shoreward advancing ripple face was close to the angle of repose and migration speeds were 10 40 cm h onshore the observations also indicate that the megaripples stalled and may have begun to migrate offshore when the mean offshore flow exceeded 20 cm s during the second storm stress based bed load sediment transport models are moderately successful in predicting the observed dependence of migration velocity on measured fluid velocities separated into zero mean current infragravity wave and sea and swell wave frequency bands wave and mean current friction factors fw and fc are obtained by best fit between the predicted and observed migration velocities for two choices 3 2 and 5 2 for the stress exponent in the bed load transport part of the model net transport is computed using wave velocity amplitudes determined from both run length statistics and wave by wave improved agreement with observations is obtained for the wave by wave net transport predictions and for the wave like treatment of the infragravity band the level of agreement is relatively insensitive to the value of the best fit current and wave friction factor values for 5 2 and 3 2 are fc 4 3 10 3 and 8 0 10 3 and fw 1 7 10 2 and 4 8 10 2 respectively

structural control of uranium mineralization at the dominique peter deposit saskatchewan canada the dominique peter deposit is part of a cluster of unconformity related uranium deposits that have been exploited since 1980 at the cluff lake mine in northern saskatchewan it is located on the south side of the 18 km basement core of the 39 km diameter circular carswell structure the metamorphic basement cylinder has risen at least 1 200 m through the mesoproterozoic sandstones underground structural study at dominique peter resulted in a revision of the understanding of the succession of tectonic events controlling mineralization emplacement and deformation the main premineralization ductile deformation d 1 and d 2 produced a flat lying gneissosity and subsequent development of foliation conformable mylonites and exhibits some contrasts with the eastern athabasca trans hudsonian tectonics east west to northwest southeast general extension ca 1 3 ga resulted in the formation of a set of 015 degrees to 050 degrees listric normal faults the latter controlled the opening of quartz then uraninite veins and induced a general tilting of fault blocks to the east mechanisms of mineralization emplacement are described in detail foliation reactivation in mylonite and aluminous gneiss is favorable to vein opening the postmineralization formation of the carswell circular structure ca 480 ma displays a centrifugal deformation with a symmetry axis located in the center of the basement dome a suite of pseudotachylyte veins breccias and shatter cones accompanies this deformation overall geometry of the carswell dome and surrounding rings as well as the nature of associated breccias presents strong similarities with those of other impact related structures

an energetics total load sediment transport model for a plane sloping beach bagnold s energetics based total load sediment transport model for streams is used as a basis for the development of a total load model of time varying sediment transport over a plane sloping bed in both the bedload and suspended load the transport rate vectors are found to be composed of a velocity induced component directed parallel to the instantaneous velocity vector and a gravity induced component directed down slope the model is applied to idealized surfzone conditions leading to estimates of the local longshore and onshore offshore sediment transport rates as well as the equilibrium beach slope as a function of the local wave and current conditions the model is combined with a nonlinear longshore current model and spatially integrated to obtain predictions of the total longshore transport rate as a function of the incident wave conditions the results support the general form of the wave power equation except that the wave power coefficient is no longer constant but is instead a complex function of the incident wave and beach characteristics

3d seismic imaging of volcanogenic massive sulfide deposits in the flin flon mining camp canada part 1 seismic results abstracta 17 km2 3d 3c seismic survey was conducted within the active flin flon mining camp located in manitoba canada the results for the vertical component data as obtained by conventional dip moveout and prestack time migration processing sequences and comparison of images from the 3d seismic volume with the subsurface location of known ore zones and the mine horizon generally showed a very good correlation a well defined diffraction response from the shallowest ore zone was observed in the unmigrated data with a corresponding phase reversal in the migrated data at the transition from intact ore to backfilled ore zone the geometry of unmined and backfilled ore zones compared well with strong reflection amplitudes on corresponding cross sections to depths of 1000 m at greater depths the ore zone had a weaker seismic signature due to a combination of effects including imaging conditions ore composition and the increased presence of rhyolite within the mine horizon in the case of the deeper or

cross shore sediment transport on natural beaches and its relation to sandbar migration patterns 2 application of the field transport parameterization 1 a cross shore sediment transport parameterization shape function based on data from intensive field experiments carried out on five european beaches is incorporated into a simple time dependent model to explore its capability for reproducing sandbar generation and evolution in the medium term o months model results are compared with bar crest migration patterns observed at duck north carolina the model comprises a simple wave transformation routine that accounts for linear shoaling and assumes a saturation law for wave decay inside the surf zone second order statistics derived from the cross shore distribution of wave heights are used to scale the sediment transport parameterizations which estimate the cross shore structure of the third and fourth velocity moments cross shore gradients in sediment fluxes calculated with an energetics approach produce bed elevation changes the updated morphology affects the wave propagation in the next time step forming a fully coupled model for predicting sandbar evolution bar generation close to shore and the details of the sandbar evolution are successfully reproduced r2 0 86 over the 77 day period of the observations using default values for drag coefficients and efficiency factors in accordance with the observations the model shows rapid offshore sandbar migration in response to individual storms and weak onshore bar movement for lower energy conditions owing to its simple nature the model is not capable of reproducing the whole profile morphology especially in the trough no trough generation and it is only valid for replicating bar crest position the results suggest that a convergence of sediment near the breakpoint breakpoint hypothesis combined with morphological feedback can successfully explain the evolution of bar crest over periods of months from the details of forcing incident waves and water levels

geology and thermotectonic evolution of the western margin of the trans hudson orogen evidence from the eastern sub athabasca basement saskatchewan in the cree lake zone of northern saskatchewan reworked archean orthogneisses are overlain by a highly deformed supracrustal sequence the paleoproterozoic wollaston group this package of rocks was deformed and metamorphosed during the ca 1 8 ga continent continent collision of the trans hudson orogen tho forming the wollaston fold thrust belt that underlies the eastern athabasca basin the hudsonian structural metamorphic and magmatic evolution of the wollaston fold thrust belt in the eastern athabasca area involved six major stages 1 early collisional stage dp1 at 1860 1835 ma involved burial of wollaston group metasediments from surface to depths equivalent to 3 5vkbar 1 kbar 100 mpa by thrust pile stacking or imbrication tectonics prograde metamorphism with garnet growth and development of early leucosomes and emplacement of ca 1840 ma grey granite suite 2 collisional stage dp2a at 1835 1820 ma involved continued deeper burial of wollaston group metasediments along a prograde

spatially correlated depth changes in the nearshore zone during autumn storms acoustic reflection measurements of seabed elevation were made at stanhope beach prince edward island during three successive storms in october november 1989 the instruments were located approximately 200 m offshore on the seaward face of a shore parallel bar in a mean water depth of 2 2 m bed elevation measurements were made at 30 min intervals with a range resolution of 1 mm at horizontal spacings between 22 cm and 1 5 m using an array of four acoustic sounders operating at 1 2 25 and 5 mhz it is shown that such an array can be used as 1 an interferometer to determine bedform properties and migration rates 2 a leveling device to determine changes in local bottom slope and 3 an erosion deposition gauge in the interferometric mode time domain autocorrelation and cross correlation analyses of the bottom elevations are used to estimate the wavelengths migration rates and migration directions of sand ripples and megaripples the ripple wavelengths 10 15 cm and heights 3 5 cm are comparable to measurements made by divers ripple migration rates were 1 6 cm h 1 directed offshore in the direction of the mean shore normal near bottom current and increased with increasing mean current speed evidence of megaripple like features 2 5 cm height 1 5 3 m length is found also migrating in the direction of the mean shore normal near bottom drift at speeds of about 20 cm h 1 bedload transport rates in the onshoreoffshore direction are estimated from the bedform migration rates the ripple transport rate was small an order of magnitude smaller than the transport of sediments in suspension by the mean offshore drift in contrast the large scale bedform transport appears to have been comparable to the mean current transport of suspended sediment interestingly it appears that the total bedform transport was comparable to that predicted by watanabe s 1981 net bedload transport formula provided a coefficient appropriate to irregular wave conditions is used during the third and highest energy storm event the measurements indicate transition to flat bed and generalized local erosion at a maximum rate of 8 cm h 1 this erosion event was associated with a general shoreward migration of the bar

intrawave sand suspension in the shoaling and surf zone of a field scale laboratory beach short wave sand transport in morphodynamic models is often based solely on the near bedwave orbital motion thereby neglec ting the e ect of ripple induced and surface induced turbulence onsand transport processes here sand stirring was studied using measurements of the wave orbital motion turbulence ripple characteristics and sand concentration collected on a eld scale laboratory beach underconditions ranging from irregular nonbreaking waves above vortex ripples to plunging waves and boresabove subdued bed forms turbulence and sand concentration were analyzed as individual events and ina wave phase averaged sense the frac tion of turbulence events related to suspension events is relativelyhigh 50 especially beneath plunging waves beneath nonbreaking waves with vortex ripples the sandconcentration close to the bed peaks right after the maximum positive wave orbital motion and shows amarked phase lag in the vertical although the peak in concentration at higher elevations does not shiftto beyond the positive to negative ow reversal under plunging waves concentration peaks beneaththe wavefront without any notable phase lags in the vertical in the inner surf zone bores the sandconcentration remains phase coupled to positive wave orbital motion but the concentration decreaseswith distance toward the shoreline on the whole our observations demonstrate that the wave drivensuspended load transport is onshore and largest beneath plunging waves while it is small and can alsobe o shore beneath shoaling waves to accurately predict wave driven sand transport in morphodynamicmodels the e ect of surface induced turbulence beneath plunging waves should thus be included

effective utilization of seismic reflection technique with moderate cost in uranium exploration abstract in participation with numerous industrial partners the seismic laboratory of the university of saskatchewan has conducted a variety of active seismic reflection experiments both on the west and east sides of the athabasca basin results of the investigations at shea creek mcarthur river and keefe lake illustrate that the seismic investigations deliver effective highly relevant primary structural images of the subsurface with resolution that no other geophysical technique can match correlation of similar seismic signatures on several distant but inter related seismic sections allowed spatial extension of promising exploration target zones previously unrecognized within the three dimensional seismic volume comparable reflectivity patterns defined the complex areal distribution of mineralization related fault systems beyond these novel contributions extended analysis of seismic signal attributes amplitude and frequency optical televiewer and full wave sonic data offer detailed lithological characterization including alteration zones clay content as well as porosity and fracture density information although these structural and geologically relevant anomalies are primary indicators of mineralization presenting novel exploration advantages the seismic method is still not a standard component of the athabasca basin exploration approach due to the negative perception that it is very expensive comparing the costs of all geophysical techniques to the cost of a single logged drill hole illustrates that the results of a properly designed seismic data acquisition program not only leads to more effective planning of a drilling program but also would lead to a much quicker recognition of the major mineralized zone s and a reduction in the number of required exploration boreholes this integrated approach to exploration would then translate into a significant reduction of the total exploration expenditures unquestionably the drilling of boreholes provides the most explicit reliable information to a certain depth but only within a very small area directly connecting the borehole information to seismic results extends the local reliable data permitting reduction of the number of boreholes to create accurate two dimensional or three dimensional subsurface images and reduction of the expenditures of the total exploration program

flow velocities sediment transport and morphological change in the swash zone of two contrasting beaches abstract as part of a large uk research project focussing on the role of swash on shoreline change two field experiments were conducted on contrasting sandy beaches a flatter dissipative beach and a steeper intermediate beach this paper describes almost 300 h of nearshore velocity data collected during this project supplemented by suspended sediment transport sediment tracer and beach profile data during both field experiments the upper part of the beach experienced progressive accretion indicating that onshore sediment transport prevailed in the swash and inner surf zones suspended sediment transport and tracer dispersal were also onshore the associated cross shore flow field was however dominated by offshore directed mean flows especially on the steeper beach velocity skewness defined as u 3 u 2 1 5 where u is the cross shore velocity and kurtosis defined as u 3 u u 2 2 were mainly directed offshore implying that energetics based sediment transport models are unable to predict the direction of sediment transport in the swash zone possible explanations for the observed accretion include enhanced bed shear stress on the uprush due to in exfiltration effects flow acceleration and or bore turbulence and advection of bore entrained sediment into the swash zone

cross shore sediment transport on natural beaches and its relation to sandbar migration patterns 1 field observations and derivation of a transport parameterization 1 cross shore sediment transport processes are investigated with measurements of horizontal velocity and sediment suspension obtained with electromagnetic current meters and optical backscatter sensors on five different beaches across europe data were gathered under a wide variety of hydrodynamic and morphological conditions spanning the swash surf and shoaling zones results show that the near bed velocity moments normalized by the local energy level ut2 n have consistent shapes shape functions when plotted against normalized cross shore depth h hb according to the energetics approach near bed velocity moments are good descriptors of sediment transport processes consequently the shape functions describe and quantify the cross shore distribution of the most relevant cross shore sediment transport processes the pattern consists of net onshore transport in the swash zone offshore transport in the surf zone and onshore transport in the shoaling zone thereby producing divergence of sediment in the inner surf swash zone and convergence in the breaker zone in consequence the shape function supports the breakpoint hypothesis for sandbar generation this behavior is a product of the balance between multiple opposing mechanisms including undertow coupling between mean flows and short long wave stirring short long wave skewness and long wave coupling with short wave variance the cross shore structure of the measured and normalized cross shore sediment fluxes is consistent with the velocity moment shape functions showing the robustness of the approach apart from the shortcomings bound to the energetics approach the present parameterization is also limited due to the difficulty of defining with confidence a breaker depth hb in bar trough systems

geometry migration and evolution of wave orbital ripples at leo 15 observations of the temporal evolution of the geometric properties and migration of wave formed ripples are analyzed in terms of measured suspended sand profiles and water velocity measurements six weeks of bedform observations were taken at the sandy medium to coarse sized sand leo 15 site located on beach haven ridge during the late summer of 1995 with an autonomous rotary sidescan sonar during this period six tropical storms several of hurricane strength passed to the east of the study site ripples with wavelengths of up to 100 cm and with 15 cm amplitudes were observed the predominant ripples were found to be wave orbital scale ripples with ripple wavelengths equal to 3 4 of the wave orbital diameter although orbital diameters become larger than 130 cm during the maximum wave event it is unclear if a transition to non orbital scaling is occurring ripple migration is found to be directed primarily onshore at rates of up to 80 cm day suspended transport due to wave motions calculated by multiplying acoustic backscatter measurements of suspended sand concentrations by flow velocity measurements are unable to account for a sufficient amount of sand transport to force ripple migration and are in the opposite direction to ripple migration thus it is hypothesized that the onshore ripple migration is due to unobserved bedload transport or near bottom suspended transport bedload model calculations forced with measured wave velocities are able to predict the magnitude and direction of transport consistent with observed ripple migration rates sequences of ripple pattern temporal evolution are examined showing mechanisms for ripple directional change in response to changing wave direction as well as ripple wavelength adjustment and erosion due to changing wave orbital diameter and relative wave to current velocities

bedform contributions to cross shore sediment transport on a dissipative beach abstract field measurements of hydrodynamics suspended sediment transport rates and bedform sediment transport rates were made in the intertidal section of a dissipative sandy beach d50 0 26 mm slope 1 80 at perranporth uk pressure transducers acoustic doppler velocimeters optical backscatter sensors and an acoustic sand ripple profiler were deployed for 12 tides measuring in a range of wave heights from 0 5 to 2 2 m water depths from 1 to 6 m and in current strengths up to 0 4 m s data were analysed in terms of the distance to shore x normalised by the surf zone width xs and spanned the region 0 4 1 5 the fractional contribution of the shoreward directed bedform transport to the total absolute transport was up to 100 and occurred broadly in the region of the breakpoint 0 5

geometry and dynamics of wave ripples in the nearshore zone of a coarse sandy beach 1 extensive measurements of ripple characteristics and dynamics along with associated suspended sediment fluxes and hydrodynamic conditions were made in the shoaling and surf zones of a macrotidal coarse grained beach at sennen cove cornwall england median grain diameter 0 69 mm suborbital vortex ripples were observed during the majority of the study period with height 5 cm and length 35 cm the scale and shape of the ripples did not vary significantly as the bed shear stress increased during wave shoaling and breaking however ripple migration rates onshore directed were strongly dependent on their location relative to the breakpoint increasing from 0 1 cm min 1 under shoaling waves to 2 cm min 1 in the outer surf zone during low energy conditions farther inside the surf zone ripples persisted but migration rates slowed probably owing to the presence of the offshore directed mean flow which impedes landward migration of the ripples under low wave conditions during which measured sediment fluxes peaked around the outer surf zone and decreased through the saturated surf zone bed form transport rates under shoaling waves were of the same magnitude as net suspended sediment fluxes but at least an order of magnitude smaller in the outer surf zone under high energy conditions during which suspended sediment fluxes in the surf zone were offshore directed owing to the presence of the seaward directed mean flow bed form transport rates were several orders of magnitude smaller than suspended fluxes

an interpretation of surface and borehole seismic surveys for mine planning at the millennium uranium deposit northern saskatchewan canada abstractthe millennium uranium deposit is located within the athabasca basin in northern saskatchewan canada the deposit is hosted within moderately dipping paleoproterozoic gneisses that are unconformably overlain by more than 500 m of flat lying porous paleoproterozoic to late mesoproterozoic athabasca group sandstones the deposit is associated with the sandstone basement unconformity post athabasca structure and hydrothermal alteration these features combine to create a complex 3d hydrogeologic setting that presents challenges with respect to mine development production and safety in 2007 as part of a prefeasibility study for potential mine development a seismic program consisting of a 3d surface survey vertical seismic profiling moving source profiling and side scan surveys was undertaken to map the complex geology the geometry and resolution of these different seismic surveys allowed for direct imaging of the geologic targets of interest regardless of orientation and size after int

sediment transport processes and morphodynamics on a reflective beach under storm and non storm conditions abstract new field experiments of sediment transport on the shoreface of a reflective beach r 0 4 0 6 during pre storm storm and post storm conditions are reported data were collected outside the breakpoint and include water surface elevations cross shore and long shore flow velocity suspended sediment concentrations bedform dimensions and the morphological response instruments included two pulse coherent adps an adv multiple obs and a pencil beam sonar the depth averaged mean velocity was always offshore and increased by a factor five during the storm and this increase is attributed to undertow being enhanced by strong backwash plumes from cusp bays estimates of cross shore suspended sediment transport are landward during the pre and post storm phases consistent with the morphological response during the storm the shoreface quickly appeared to reach equilibrium despite energy levels being maintained with sediment transport rates reducing rapidly after the initial phase of the storm streaming in the wave boundary layer was observed and strongest during the pre storm phase consistent with the observed shoreward transport during the storm the near bed streaming was too small to reverse the increased offshore current consistent with the observed net offshore transport the generally small orbital velocity skewness observed on this steep reflective beach suggests that wave reflection may reduce the overall skewness of the velocity in turn contributing to the stability of reflective beach types

megaripple migration in a natural surf zone migrating megaripples are bedforms that appear in the surf zone of sandy coasts1 with heights of 0 1 0 5 m and wavelengths of 1 5 m they are similar in size and shape to small dunes large ripples or sand waves such sedimentary bedforms have been studied in subaerial2 steady flow3 and intertidal4 environments as well as in laboratory flume experiments5 they affect overlying currents by introducing hydraulic roughness4 6 and may provide a mechanism for sediment transport7 8 as well as forming sedimentary structures in preserved facies9 10 the formation orientation and migration of such bedforms is not understood well11 12 dunes for example can be aligned with their crests perpendicular to steady unidirectional winds13 but in more complex wind fields their orientation becomes difficult to predict14 15 16 17 similarly it is not known how sea floor megaripples become aligned and migrate in the complex flows of the surf zone here we present observations in the surf zone of a natural beach which indicate that megaripples do not migrate in the direction of the vector sum of the currents but are aligned so that the sediment transport normal to the bedform crest is maximized17 this may need to be taken into account in modelling morphology change and interpreting existing and fossil morphologic patterns

uranium mineralization indicators from seismic and well log data in the shea creek area at the southern margin of the carswell impact structure athabasca basin canada the primary economic uranium u mineralization indicators in the athabasca basin are the reactivated prominent basement deformation zones basement alteration halos and the overlying sandstone alteration halos enveloping the deposit high resolution seismic surveys from the shea creek area are investigated to assess the potential of the surface seismic reflection technique for detecting these key mineralization markers four seismic profiles identify ductile to highly brittle deformation features of the basement one of the brittle deformation features is a southwest dipping prominent reactivated shear zone comparable to basement structures hosting other known deposits in the basin the carswell meteor impact structure is also a conspicuous component of the shea creek regional structural regime the seismic sections identify several features of the impact structure including recognition that the dimensions of this structure are significantly larger than those estimated by previous geological studies this larger area includes both the cluff lake mine and the shea creek u deposits and it reveals that the basement was considerably disturbed by the impact and suggests the reactivation of the southwest dipping shear zone complex trace analysis of the seismic sections provides detailed information about the lateral changes in the reflectivity properties of the unconformity interval which is another key zone of interest for uranium exploration based mainly on velocity information several sub zones of clay alteration and silicification were identified within prominent fracture depth intervals both in the sandstone and the basement thus this study documents that these primary mineral indicators can be detected by the seismic method cross plots of velocity versus density of well log data identify changes in lithological units such as unaltered basement fractured altered basement unaltered sandstone clay alterations in sandstone and silicification in sandstone

eulerian measurements of horizontal accelerations in shoaling gravity waves laboratory and field measurements of suspended sediment in the nearshore suggest that fluid accelerations are an important factor in sediment transport by oscillatory waves here eulerian accelerations of the cross shore velocity are calculated from measurements of velocity obtained by an array of bottom mounted electromagnetic flow meters spanning a natural surf zone large shoreward accelerations of brief duration are associated with the steep front faces of both near breaking and breaking waves weaker offshore accelerations of longer duration occur during passage of the more gently sloped rear faces the acceleration field is thus strongly skewed in the shoreward direction power spectra and bispectra indicate as expected that statistics of the acceleration field are significantly influenced by high frequency motions but are rather insensitive to surf beat

application of modern 2 d and 3 d seismic reflection techniques for uranium exploration in the athabasca basinthis article is one of a series of papers published in this special issue on the theme lithoprobe parameters processes and the evolution of a continent seismic reflection techniques have been applied in several studies over the last 20 years as a uranium exploration tool within the athabasca basin and have been utilized to provide the larger structural context for known uranium deposits within the basin at the crustal scale deposits within the eastern athabasca basin are shown to be associated with deep seated shear zones that originated during trans hudson orogeny and have subsequently been reactivated during and subsequent to deposition of the basin fill sandstones seismic properties of the athabasca sandstones and underlying basement have been determined through in situ borehole measurements reflectivity within the sandstones is generally weak seismically recognizable signatures are primarily associated with variations in fracture density porosity and degree of silicification the basement unconformity and regolith a prime target of exploration is widely imaged as it is characterized by variable but generally distinct reflectivity results fr

measured and predicted rates of sediment transport in storm conditions abstract owing to difficulties in obtaining measurements and to the vagaries of the weather at sea few field data exist pertaining to sediment mobilisation and transport in storm conditions consequently empirical formulae widely used to predict sediment transport in marine environments remain largely untested in extreme conditions in the present paper bedload transport rates estimated from measured rates of bedform migration and measured rates of suspended sediment transport have been compared with predictions from various empirical formulae rates of bedload transport inferred from measured rates of ripple migration are found to compare favourably with previous observations and with empirical predictions obtained using the bijker formula measured rates of total sediment transport are found to agree well with predictions from the soulsby formula results show that these formulae are able to predict accurately marine sediment transport in combined wave current conditions during a storm

3d reflection seismic imaging for open pit mine planning and deep exploration in the kevitsa ni cu pge deposit northern finland a 3d reflection seismic survey was conducted over an area of about 9 km 2 at the kevitsa ni cu pge platinum group elements orebody northern finland where open pit mining started in mid 2012 t